T lymphocytes comprise cells expressing either an αβ or a γδ TCR. The riddle how αβ TCRs are triggered by specific peptides presented in the context of MHC was elucidated some time ago. In contrast, the mechanisms that underlie antigen recognition by γδ TCRs are still baffling the scientific community. It is clear that activation of γδ TCRs does not necessarily depend on MHC antigen presentation. To date, diverse and largely host-cell-derived molecules have been identified as cognate antigens for the γδ TCR. However, for most γδ TCRs, the activating ligand is still unknown and many open questions with regard to physiological relevance and generalizable concepts remain. Especially the question of how γδ T cells can distinguish homeostatic from stress conditions via their TCR remains largely unresolved. Recent discoveries in the field might have paved the way towards a better understanding of antigen recognition by the γδ TCR and have made it conceivable to revise the current knowledge and contextualize the new findings. They are able to recognize a plethora of infections such as by mycobacteria,3Plasmodium,5 or cytomegalovirus (CMV)6 and induce potent infection containing reactions, such as granzyme and cytokine release.8 Besides, γδ T cells were also shown to be effective in inducing antitumor responses.11T cells are divided into αβ and γδ T cells based on the expression of their respective T-cell receptor (TCR). With a frequency of 0.5–16% of all T cells in human peripheral blood γδ T cells are the smaller subset although higher abundances can be observed in peripheral tissues.13 and by the clonal expansion of specific γδ TCRs upon infections.15 Like its αβ counterpart, the γδ TCR is composed of two chains, named gamma and delta, whose diversity is generated by the recombination of variable (V), diversity  and joining (J) fragments. With some exceptions in sharks,16 somatic hypermutation as in immunoglobulin genes does not occur in TCRs so that the recombined region, which makes up the complementarity defining region 3 (CDR3), comprises most of the receptor’s diversity. The recognition of antigens, however, seems to be entirely different when compared between αβ and γδ TCRs. Most αβ TCRs bind to major histocompatibility complexes (MHC) I or II presenting small peptide fragments derived from pathogens or tumor specific proteins. Together with co-receptor engagement of CD4 or CD8 and co-stimulation through CD28, this elicits T-cell activation. In contrast, the γδ TCR does not require MHC-mediated antigen presentation and no general requirement for co-receptor interaction has been identified so far. This has led to the notion that the mere binding of the γδ TCR to its cognate antigen is sufficient for activation. Moreover, γδ TCRs have the ability for both innate and adaptive ligand recognition via either germline-encoded regions of the receptor, reminiscent of PRRs or adaptive antigen binding via the CDRs.17Besides the different immune receptors expressed by γδ T cells like NK cell receptors and NCRs, their TCR is one of the main cell-surface molecules that is involved in the recognition of pathological conditions. This assumption is supported by blocking experiments18 Alternative methods like the generation of blocking antibodies, genetic approaches or tetramer staining with known T-cell antigens is on the one hand side tedious and labor-intensive or on the other hand requires a priori knowledge of possible candidates, which introduces a bias.19 Third, it is difficult to assess whether the recognition of certain antigens by γδ TCRs can be generalized, because a number of known antigens are bound solely by particular clones that have been identified in individuals. Moreover, findings in the mouse system can in most cases not be translated into the human system and vice versa because the TCR sequences and subsets in mice and humans differ substantially. This also complicates the assessment of physiological relevance of many human γδ TCR ligands since they can be identified only in vitro without the possibility to test their functionality in transgenic animals.Although central for understanding γδ T-cell biology and their application in therapeutic approaches, the identification of γδ TCR antigens has been proven challenging for several reasons. First, since no general restricting molecule could be identified for the γδ TCR, the antigens could be virtually any molecule present on cell surfaces or in the surrounding extracellular space. This becomes particularly problematic if not only proteins, which are already very diverse, but also carbohydrates, lipids and nucleic acids could be recognized or at least involved in the recognition because this further increases the complexity of the question and is technically demanding to address. Second, the affinity of TCRs to their antigens is typically low being mostly within the range of 1–100 µM. Therefore, classical methods of protein biochemistry cannot be applied.Despite all these obstacles, several antigens for the γδ TCR have been identified since the discovery of γδ T cells  reactive to the MHC-Ib molecule T10/T22 develop without the presence of their cognate antigen in β2-microglobulin knockout mice.26 In contrast, experiments with mice expressing another T10/T22-reactive γδ TCR (KN6)27 and an MHC class I-reactive γδ TCR28 showed that the development and maturation of γδ T cells were impaired in a β2-microglobulin knockout background. As the β2-microglobulin knockout does not completely eliminate surface expression of T10/T22, a mouse model with a more specific knockout of T10 and T22 was generated and led to the conclusion that the antigen is important for the development of γδ T cells.29 However, even the complete absence of the respective antigen failed to abolish the generation of at least some T22-reactive γδ T cells, which might be explained by a certain plasticity of the γδ TCR for different ligands. Thus, γδ T cells can develop without the presence of their cognate antigen but their functional maturation is heavily impaired. Moreover, nonexpanded clones reactive to MHC or MHC-like molecules likely make up only a small part of the total γδ TCR repertoire and their disappearance might not be detectable in β2-microglobulin knockout mice. Therefore, clones reactive to MHC or MHC-like molecules likely coexist next to those recognizing non-MHC molecules.The paradigm of γδ T cells not being restricted to MHC is based to a large extent on the observation that γδ T cells develop normally in β2-microglobulin knockout mice whereas αβ T cells are missing due to missing positive selection in the thymus.22 and class I molecule H-2,30 both found to activate cytotoxic γδ T-cell clones derived from athymic mice. In humans, HLA-24,31 HLA-B27,32 and HLA-A233 were specifically activating γδ T-cell clones derived from healthy individuals that have been expanded in culture. All these identified interactions have in common that they are independent of peptide presentation by the MHC, as their activation also occurred in cell lines with peptide-loading defects. These γδ T-cell clones were therefore qualified as alloreactive. The fact that some of them are able to cross-react with some subtype of the same MHC indicates that they might even be binding to less polymorphic parts of the MHC molecule. Additionally, a further alloreactive Vγ5Vδ1+ TCR has recently been found to recognize HLA-A∗24:02 on cancer cells.23 It was shown to be dependent on peptide loading of the HLA complex but not the presentation of a specific peptide. Given the increased stability of peptide-presenting MHC molecules on cell surfaces, the authors reasoned that the random peptide presentation might be rather required for target stabilization than for specific antigen presentation. In contrast to this, Vδ1+ γδ T cells derived in vitro from human hematopoietic stem and progenitor cell (HSPC) were reactive to MHC HLA-A2-restricted peptide presentation of the melanoma antigen MART-1.34 However, the resolved structure of the interacting proteins suggests that binding of the respective γδ TCRs to MART-1 presenting MHC is less peptide-centric as compared to the interaction with a MART-1-specific αβ TCR. Hence, one might speculate that MART-1-MHC-specific activation of some γδ TCR is still different from classical αβ TCR MHC-restriction and that MART-1 could also be a specific stabilizer for the MHC that is required for proper detection by the respective γδ TCRs.Examples of γδ TCR-ligands that are classical MHC molecules comprise murine MHC class II molecule I-E39 Human γδ TCRs recognizing CD1-molecules are Vδ1+24 or Vδ3+40 and they can react to several presented phospho- and glycolipids.36 However, unloaded CD1-d was also able to bind to Vδ1+ γδ TCRs albeit with lower affinity than if presenting lipids,24 which would be in-line with the mentioned alloreactivity observed in MHC-reactive γδ TCRs. Another MHC-Ib molecule that is a putative ligand for the γδ TCR is murine Qa-1b presenting an artificial glutamine-tyrosine polypeptide.41 In addition, in vivo expansion of γδ IELs in response to Salmonella infection was dependent on peptide loading of Qa-1b.42 Yet, unambiguous evidence that physiological peptides bound to Qa-1b are specifically recognized by γδ TCRs does not exist and a mere stabilizing function as in the case of human HLA∗24:02 cannot be excluded.23Besides classical MHC recognition some γδ TCRs are reactive towards MHC class Ib or MHC-related proteins in mice and humans. The lipid-antigen-presenting molecules CD1-c and CD1-d are amongst the best studied examples of this group.43 endothelial protein C receptor (EPCR),25 MHC class I-related Chain A or B (MICA/MICB),46 UL16-binding protein 4 (ULBP4)13 and T10/T22 in mice.50 The reasons are that either the reactive γδ TCRs are binding independently of the presented antigen (MR-1), no further molecules are presented (EPCR) or the antigen-binding cleft of the respective ligand is truncated, which precludes the loading of antigen (T10/T22). Thus, overall γδ TCR recognition of classical MHC or MHC-like molecules seems to be independent of the presentation of foreign antigens, which is in contrast to αβ TCR antigen binding.Other functional interactions of γδ TCRs with MHC-like molecules do not require the presentation of antigens as is the case for MHC-related protein 1 (MR-1),−- or Vγ9−Vδ2+ sequences. Furthermore, reactive TCRs were usually derived from particular private clones  that were not shared between individuals or were of low abundance in peripheral blood . However, γδ TCR repertoire analysis revealed that clones of the Vδ2−- or Vγ9−Vδ2+ subsets can undergo rapid and sustained clonal expansion in response to e.g., CMV infection15 and MART-1-HLA-A2 reactive γδ T cells could be expanded from PBMCs in vitro.34 These features of MHC- and MHC-like-reactive γδ TCRs are reminiscent of the adaptive responses observed in αβ T cells, hence this type of antigen recognition in γδ TCRs was termed adaptive as has been reviewed by Willcox & Willcox18 as well as Davey et al.52 As a consequence, it is often difficult to judge whether the ligand-specificities observed are a general phenomenon that is particularly relevant, since most of the interactions were identified in cell culture systems in vitro and, so far, evidence for physiological relevance is still rare. On the other hand, also in αβ T cells the amount of particular antigen-specific clones is low prior to expansion and it is conceivable that antigen-naïve but potentially reactive γδ T cells present at low frequencies would expand upon antigen exposure. In fact, the EPCR-reactive LES clone (Vγ4Vδ5+) made up about 25% of the entire T-cell repertoire in a CMV-positive transplanted patient.25 In addition to the low abundance of naïve γδ T cells, it is possible that other MHC- or MHC-like reactive γδ TCRs escaped the detection by tetramer staining as in the case of CD1-d or MR-1 because the affinity for their cognate antigen was too low for flow cytometry approaches. Concerning the methodology employed for the identification of the so far investigated MHC molecules as γδ TCR ligands, it has been criticized that it relied to a large extent on previous knowledge and techniques from αβ TCRs and the detection of MHC or MHC-like molecules as γδ TCR ligands might thus not appear very surprising. Despite this technical bias in many studies published in the past, the identification of HLA∗24:02 as an antigen for the alloreactive Vγ5Vδ1+ γδ TCR by Kierkels et al. indicates that also approaches without preconceived ideas of putative antigen candidates can reveal MHC or MHC-like molecules as γδ TCR ligands.23 The question to what extent the reactivity to MHC molecules can be generalized awaits further investigation and unbiased identification of reactive γδ TCRs.Reactivity of γδ TCRs to MHC or MHC-like molecules is largely dependent on the CDRs with a substantial focus on the CDR3δ in most cases  and the TCR-chains are commonly composed of Vδ253 and ephrin receptor A2 (EphA2),54 which were recognized by Vδ2− γδ T-cell clones in a TCR-dependent manner on cells that were either transformed, CMV-infected or exposed to abiotic stressors, e.g., heat. The human DNA mismatch repair protein MutS-Homologue 2 (hMSH2)55 is found at the cell surface of malignant cells and induces target cell killing dependent on Vδ2+ γδ TCRs. Furthermore, histidyl tRNA synthetase57 is recognized by a Vγ3Vδ2+ TCR identified in a polymyositis patient although it remains elusive how this target can be reached by the γδ TCR since no cell-surface exposition has been shown to date. In both cases the γδ TCRs were Vγ9−Vδ2+.Adaptive or adaptive like antigen recognition by γδ TCRs is by no means limited to MHC- or MHC-like molecules as shows the wide and diverse range of cell surface or soluble molecules reported to be γδ TCR antigens. These include the cell stress-induced Annexin A2+ TCR,58 bacterial superantigens such as SEA, OXYS, and DX261 and even the algal protein phycoerythrin (PE), which is a prototype B-cell antigen but can also be bound by range of different murine, ruminant as well as human γδ TCRs.62 Similar observations were made with the haptens Cy3 and NP.63 However, it is very unlikely that PE or haptens represent actual antigens under physiological conditions. Nevertheless, these studies underline the plasticity of γδ TCR target recognition and it might be used in experimental models. Strikingly, not only entire proteins but also small peptide fragments can be detected by γδ TCR without the requirement for presentation by other cells or molecules. Examples are the insulin peptide B:9–23 in mice,65 peptides derived from mycobacterial and mammalian heat shock proteins in mice and humans68 and from the Lysteria monocytogenes protein Listeriolysin O in humans.69 Other peptides, however, do not bind the TCR directly but seem to require presentation on target cells such as those derived from tetanus toxin71 and from immunoglobulin λ-chain from B-cell lymphoma.73 Recognition of these peptides, whether presented or not, was found to be γδ TCR dependent but neither were direct interactions between γδ TCR and peptides shown nor exists evidence for their physiological relevance. Recently, murine γδ NKT cells with a Vγ1Vδ6.3+ TCR were found to be activated constitutively when cultured in vitro. The reaction was TCR-dependent and driven by polyanions present on the treated plastic ware used for culturing the cells.74 Although both chains were required for the reactivity, the Vγ1-chain seemed to have a slightly higher importance with only secondary relevance of the CDR3. Interestingly, many of the aforementioned peptide-specificities of γδ TCRs mice are mediated via Vγ1+ TCRs. Although the peptides described are not necessarily polyanionic, reactivity for short polymeric sequences by this group of TCRs might be a common feature that is, however, probably not CDR3 dependent.Foreign antigens derived from pathogenic or nonpathogenic organisms that have been reported to activate γδ TCRs comprise herpex simplex virus glycoprotein I (HSV-gI) recognized by a murine Vγ2Vδ875 Although recognition of antigen by VDJ-recombined adaptive immune receptors depends on more factors than the mere CDR3 length, this points to an antigen-binding mode of γδ TCRs that is substantially different from αβ TCRs. Together with the great variety of γδ TCR antigens this has led to the concept of a rather immunoglobulin-like (Ig-like) recognition of antigens by γδ TCRs.76 In accordance with this, similar to immunoglobulins, γδ TCRs seem to be able to recognize structural as well as sequence epitopes. Moreover, the fact that many different γδ TCRs can be specific for the same target molecule as e.g., in the case of PE, CD1-d, or MR-1 is reminiscent of polyclonal antibodies with the same target specificities but different binding modes.Together with the different MHC and MHC-like molecules, these examples of recognized molecules illustrate the high diversity of ligands for the γδ TCR that is in contrast to αβ TCRs, which can recognize a wide range of peptides but all in the context of the less polymorphic MHC class I and II molecules. Furthermore, comparison of the CDR3 lengths between the different adaptive immune receptors revealed that overall γδ TCRs resemble more immunoglobulins with a shorter CDR3γ and a longer CDR3δ, which is in contrast to CDR3α and CDR3β that have comparable lengths.77 To what extent a possible Ig-like antigen recognition by γδ TCRs plays a role in vivo remains a matter of debate.Despite these striking similarities between γδ TCRs and immunoglobulins with regard to their antigen recognition properties, one should always bear in mind that fundamental differences exist. The affinity of most γδ TCRs for their antigens is low in contrast to high-affinity antibodies, which has important considerations for technical applications, such as flow cytometry or co-immunoprecipitation. Due to the high density of γδ TCR molecules on the cell surface in physiological contexts and similarly high expression of the respective ligands, the high avidity of this interaction probably circumvents the single molecule low-affinity binding.78 This subset is also found in other species, e.g., in non-human primates80 or alpaca but not in rodents.82 Vγ9Vδ2+ TCRs recognize small non-proteogenic phosphorylated molecules termed phosphoantigens (p-Ags) in an MHC-independent way.83 The most potent p-Ag is (E)-4-hydroxy-3-methyl- but-2-enyl pyrophosphate (HMBPP), an intermediate of the prokaryotic non-mevalonate pathway of isoprenoid biosynthesis. Isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) are present in both prokaryotes and eukaryotes. However, their efficiency to activate Vγ9Vδ2+ TCRs is lower compared to HMBPP. IPP and DMAPP can accumulate inside eukaryotic cells in response to stress situations e.g., infection or malignant transformation whereas HMBPP is produced directly by pathogens such as gram-positive bacteria, Plasmodium or Toxoplasma gondii.84 Besides the naturally occurring p-Ags, synthetic aminobisphosphonates as alendronate, zoledronate or pamidronate can activate Vγ9Vδ2+ TCRs by inhibiting the enzyme farnesyl pyrophosphate synthase in the mevalonate pathway of eukaryotic isoprenoid biosynthesis leading to an intracellular accumulation of IPP.86 Vγ9Vδ2+ T cells can therefore be expanded for cancer immunotherapy by administration of these aminobisphosphonate drugs as has been reviewed by Morita et al.83 and Legut et al.87 The recognition of ubiquitous microbial or stress signals by γδ TCRs is reminiscent of the PAMP-detection by pattern recognition receptors, which is supported by the semi-invariant V-usage of these γδ TCRs and rather polyclonal expansions in response to p-Ags.88 Therefore, Vγ9Vδ2+ TCR-mediated recognition of p-Ags has been termed innate-like.84In humans the largest subset of γδ T cells in peripheral blood express a semi-invariant TCR composed of a restricted Vγ9JP rearrangement together with a more diverse Vδ2 chain.+ TCRs, these small phosphorylated moieties are not the cognate antigens binding to γδ TCRs and cell to cell contact is necessary.89 Especially, the protein butyrophilin 3 A1 (BTN3A1) has been shown to be essential for γδ TCR-mediated p-Ag-recognition.91 BTN3A1 belongs as the other butyrophilins to the B7 receptor family-like proteins and consists of two extracellular Ig-like domains, transmembrane and juxtamembrane domains and an intracellular B30.2 domain.92 After the discovery of BTN3A1 as a central mediator of p-Ag reactivity, two different models of interaction with p-Ags were proposed. Vavassori et al.93 first showed evidence for an antigen presentation by BTN3A1 and a direct interaction between p-Ag presenting BTN3A1 and the Vγ9Vδ2+ TCR. In contrast, Sandstrom et al.94 made the observation that the intracellular B30.2 domain of BTN3A1 binds the p-Ags in a pocket with basic residues and no direct interaction between the extracellular IgV-domain of BTN3A1 and the Vγ9Vδ2+ TCR was detected. Subsequent mutagenesis experiments with BTN3A1 intra- and extracellular domains revealed that the second model of intracellular p-Ag binding held true.95 Moreover, rodent cells expressing human BTN3A1 are not able to stimulate Vγ9Vδ2+ TCRs upon p-Ag exposure indicating that other mechanisms and molecules are probably involved.94 Thus, the current concept of BTN3A1-mediated activation of Vγ9Vδ2+ TCRs implies that intracellular p-Ag binding to the B30.2 domain leads to conformational changes that translate to the extracellular domain of BTN3A1 in order to be sensed indirectly by Vγ9Vδ2+ TCRs. In-line with this hypothesis, NMR-studies of the B30.2 domain and the juxtamembrane domain of BTN3A1 revealed conformational changes upon p-Ag binding.98 Furthermore, the cytoskeletal adaptor protein periplakin as well as the GTPase RhoB were reported to interact with the B30.2 domain and thereby assist to organize BTN3A1 membrane organization influencing Vγ9Vδ2+ TCR activation.100Despite the requirement for p-Ags for the activation of Vγ9Vδ2+ TCRs as the BTN3A isoforms BTN3A2 and BTN3A3 were shown to be required by the use of knock down and knockout cell lines.101 In contrast to the observation of BTN3A1 homodimers, BTN3A1 and BTN3A2 seem also to be able to form heterodimers, which enable the correct BTN3A1 localization to the cell membrane and complete functionality in terms of p-Ag reactivity. Interestingly, expression of BTN3A1 alone can lead to Vγ9Vδ2+ TCR activation in response to p-Ag, albeit with much lower efficiency. To which extent BTN3A homo- or heterodimers play important functions in p-Ag recognition by Vγ9Vδ2+ TCRs or whether interconversion between both structural arrangements can occur is still to be elucidated.However, BTN3A1 alone is not sufficient for p-Ag recognition by Vγ9Vδ2+ TCR activation is compelling, no direct interaction with the γδ TCR has been established so far. Rodent cell lines expressing transgenic human BTN3A1 were shown to require human chromosome 6 for inducing functional p-Ag reactivity in Vγ9Vδ2+ TCRs.102 Hence, another component encoded on this chromosome appeared to be essential to induce p-Ag responses. Recently, BTN2A1 has been identified by two different approaches to be this enigmatic “factor X” and to be a direct ligand for Vγ9Vδ2+ TCRs. Rigau et al.103 employed tetramerized soluble TCR staining of target cells and a genome-wide CRISPR screening to identify candidates for Vγ9Vδ2+ TCR ligands. At the same time, Karunakaran et al.104 generated radiation hybrids of Chinese Hamster Ovarian (CHO) cells containing human chromosome 6 and screening for abrogation of p-Ag reactivity led to the identification of the gene encoding BTN2A1. Both publications suggested binding of the Vγ9-chain to BTN2A1 via germline-encoded regions and without major involvement of the CDRs with an affinity of around 45–50 µM. BTN2A1 itself seems to form homodimers linked by disulfide bridges and it associates with BTN3A1 on the cell surface as has been shown by co-immunoprecipitation104 and FRET.103 Interestingly, not only the extracellular IgV domains of BTN2A1 and BTN3A1 but also their intracellular regions seem to be at least in close proximity although only the B30.2 domain of BTN3A1 is able to bind p-Ag as shown by isothermal calorimetry (ITC).103 The domains of the Vγ9-chain involved in interaction with BTN2A1 were determined by mutagenesis of the γδ TCR and BTN2A1 and molecular modeling in silico. The data suggest that interaction occurs between the C, C’, F, and G β strands (CFG interface) of BTN2A1 and residues of the germline-encoded hypervariable region 4 (HV4) as well as CDR2γ.104 The results from the mutagenesis study conducted by Rigau et al.103 were not entirely consistent with these observations. Based on their mutagenesis experiments, they concluded that the outer face of the ABED β-sheet is important for the interaction with BTN2A1. However, in both cases the interaction interface of the Vγ9-chain with BTN2A1 was germline-encoded and a central glutamic acid residue at position 70 was considered to be relevant by both groups. Further investigation might be required to completely solve this discrepancy.Although the evidence for BTN3A1 as the p-Ag sensing molecule and its influence on Vγ9Vδ2+ TCR response to p-Ag, are involved in this process.105 Mutations in the CDR3γ and the CDR2δ led furthermore to the abrogation of p-Ag reactivity but not the binding of the Vγ9-chain to BTN2A1. This indicated that binding to BTN2A1 is required but not sufficient for a Vγ9Vδ2+ TCR-mediated response.103 Thus, it has been speculated that at least a second interaction is necessary. Whether this is mediated by BTN3A1 as proposed by Rigau et al.103 or if a yet completely unknown ligand is involved as suggested by Karunakaran et al.,104 remains to be defined.A still unsolved question concerning BTN-mediated p-Ag-reactivity is how the CDR3γ and CDR3δ, which are both reported to be required for a Vγ9Vδ2+ TCRs. Other proteins with structural similarity to the B7 receptor superfamily such as Skint-1 and Butyrophilin-like (Btnl)1 and 6 in mice as well as BTNL3 and 8 in humans were shown to be relevant for the development and possibly for the tissue homing and homeostasis of certain γδ T-cell subsets as has been reviewed recently by Haday and Vantourout.17The role of butyrophilins in γδ T-cell biology exceeds their implication in p-Ag sensing and the activation of Vγ9Vδ2+ TCR require Skint-1 expression, since mice with a mutation in the Skint-1 gene leading to a premature insertion of a stop-codon lack this skin-resident γδ T-cell subset.107 It is in particular the homing to the skin as well as the phenotype of these Vγ5Vδ1+ T cells that is affected rather than their differentiation in general.108 This effect was additionally shown to be γδ TCR-dependent, which makes Skint-1 a putative ligand.110 Mutagenesis of the membrane distal domain of Skint-1 and NMR-studies suggest a putative receptor-interaction surface but a direct interaction with the γδ TCR has not been shown so far.111Murine DETCs bearing a canonical Vγ5Vδ1+ IELs in the gut in a γδ TCR-dependent manner. Likewise, human intestinal Vγ4+ TCRs can be activated by the co-expressed Btnl-homologues BTNL3 and BTNL8.112 TCR-dependent responsiveness to BTNLs seems thus to be evolutionarily conserved. Recently, direct binding as well as the mode of interaction of Btnl/BTNL proteins and the respective γδ TCRs were revealed.114 The interaction was mediated via the germline-encoded γ-chain HV4 with the involvement of some CDR2 residues and the CFG-domain of Btnl6 and BTNL3, reminiscent of superantigen binding to αβ TCRs.115 Other CDRs and the entire δ-chain were not involved but are available for clonally specific ligand binding of e.g. CD1-d or EPCR. This indicates that γδ TCRs are intrinsically able to combine clonal adaptive reactivity and nonclonal innate responsiveness to common ligands. The physiological role of BTNL-responsiveness by γδ TCRs beyond its implication in γδ T-cell development remains to be elucidated. It has, however, been discussed, that it may serve as a signal of normality, keeping the cells ready to respond to cognate antigens under stress conditions.113The case of Btnl/BTNL proteins in mice and humans seems to be, however, much clearer. Btnl1 and 6 form heterodimers and are required for the development of Vγ7116 Moreover, the recently investigated interaction mode between BTN2A1 and the public Vγ9JP-chain follows the same principle as between BTNL/Btnl proteins and γδ TCRs. In both cases, the HV4 was described as the major mediator of the interaction, suggesting that a binding mode via germline-encoded domains might describe a more general feature of butyrophilin binding by γδ TCRs.Whether germline-encoded recognition of B7 family-like proteins via the γ-chain HV4 extends also to other γδ TCRs and represents a general principle is unclear. The tissue-specific expression of certain γ-chains would reflect such a broadly applicable mechanism.Hallmarks of antigen recognition by αβ TCRs are the recognition of pathogen-derived peptides presented by MHC molecules and additional regulation via co-receptors, which allow all together the fine-tuned discrimination of foreign from self. Ligands of γδ TCRs, however, are representing a wide range of largely host-cell-derived molecules, which are believed to be signals of cellular stress  receptor that was reported to enhance TCR-mediated immune responses of γδ T cells.100 Although no direct binding of the Vγ9Vδ2+ TCR to BTN3A1 has been observed so far, this conformational change is required for p-Ag-mediated activation either via BTN3A1 interacting with the CDRs of the TCR or indirectly via a yet unknown molecule. Conformational differences of γδ TCR ligands might also be caused by multimerization as it is the case for the MHC-molecule HLA∗24:02 recognized by the alloreactive Vγ5Vδ1+ TCR23  on the surface of a reporter target cell line, which led to the expression of a fluorescent reporter gene construct upon functional αβ TCR binding.140 To γδ TCRs however, these approaches cannot be applied since no general restrictive molecule such as the MHC exists or has at least not been identified yet. Therefore, the emerging possibilities of CRISPR-Cas9 technology might be better applicable in this context. With the appropriate readout systems at hand, such as target cell killing or binding of TCR-tetramers, genome-wide CRISPR libraries might allow for a negative selection of those cells where the target for the γδ TCR is not present anymore.During the past decades, research on γδ TCR ligands revealed a plethora of diverse molecules that are recognized by either unique specific γδ TCRs or by omni-present TCRs with canonical γδ rearrangements such as Vγ9Vδ2. Although some general patterns like involvement of butyrophilins and BTNLs or the recognition of MHC-like molecules can be observed, an overarching concept of what is driving the activation of γδ TCRs is still missing. Thus, in order to broaden our understanding of γδ TCR specificities and their implications in health and disease, unbiased and large-scale screening approaches for further ligands will be required. For αβ TCRs, a multitude of these methods is already established as recently reviewed by Gerber et al.To get a better understanding of γδ TCR activation, the mere identification of ligands on its own will, however, not be sufficient. Especially for host-cell-derived ligands for the γδ TCR, which might be directly recognized without further processing, it is essential to understand the mechanisms by which a discrimination between normal and stress conditions can take place. Besides the differential expression of the respective ligand, co-stimulatory effects by other molecules, multimerization, conformational changes and differential glycosylation of the putative ligand should be considered and investigated more in this context. This should help to reconcile so far contradicting observations in γδ TCR research and help to better understand ligand recognition by the γδ TCR.


Home Video Telehealth offers a unique opportunity to support already burdened caregivers of persons with dementia. Veterans Health Administration, through the MISSION Act, is increasingly using video telehealth to provide “care at the right time and in the right place.” Little is known about the benefits and challenges of using video telehealth for in-home caregiver support. We present findings from our seven years offering in-home dementia management to caregivers of Veterans with dementia, that includes supporting caregivers through supportive listening, tips for communication and safety strategies, and recommendations regarding non-pharmacologic management of behaviors. Perceived benefits of in-home video telehealth include an ‘in vivo’ perspective of the family’s natural context and remediating barriers to care such as decreased mobility. Perceived challenges include dealing with technology and privacy concerns. By describing considerations for in-home video telehealth to a clinical population with unique care needs, we inform broader application of a promising technology.


Infection and inflammation have been implicated in the etiology and subsequent morbidity associated with preterm birth. At present, there are no tests to assess for fetal compartment infection. The thymus, a gland integral in the fetal immune system, has been shown to involute in animal models of antenatal infection, but its response in human fetuses has not been studied. This study aims: (a) to generate magnetic resonance imaging (MRI) -derived fetal thymus volumes standardized for fetal weight; (b) to compare standardized thymus volumes from fetuses that delivered before 32 weeks of gestation with fetuses that subsequently deliver at term; (c) to assess thymus size as a predictor of preterm birth; and (d) to correlate the presence of chorioamnionitis and funisitis at delivery with thymic volumes in utero in fetuses that subsequently deliver preterm.Women at high-risk of preterm birth at 20-32 weeks of gestation were recruited. A control group was obtained from existing data sets acquired as part of three research studies. A fetal MRI was performed on a 1.5T or 3T MRI scanner: T2 weighted images were obtained of the entire uterine content and specifically the fetal thorax. A slice-to-volume registration method was used for reconstruction of three-dimensional images of the thorax. Thymus segmentations were performed manually. Body volumes were calculated by manual segmentation and thymus:body volume ratios were generated. Comparison of groups was performed using multiple regression analysis. Normal ranges were created for thymus volume and thymus:body volume ratios using the control data. Receiver operating curves (ROC) curves were generated for thymus:body volume ratio and gestation-adjusted thymus volume centiles as predictors of preterm birth. Placental histology was analyzed where available from pregnancies that delivered very preterm and the presence of chorioamnionitis/funisitis was noted.P < .001). Of the 16 fetuses that delivered preterm, 13 had placental histology, 11 had chorioamnionitis, and 9 had funisitis. The strongest predictors of prematurity were the thymus volume Z-score and thymus:body volume ratio Z-score .Normative ranges were created for thymus volume, and thymus volume was standardized for fetal size from fetuses that subsequently delivered at term, but were imaged at 20-32 weeks of gestation. Image data sets from 16 women that delivered <32 weeks of gestation (ten with ruptured membranes and six with intact membranes) and 80 control women that delivered >37 weeks were included. Mean gestation at MRI of the study group was 28+4 weeks (SD 3.2) and for the control group was 25+5 weeks (SD 2.4). Both absolute fetal thymus volumes and thymus:body volume ratios were smaller in fetuses that delivered preterm (We have produced MRI-derived normal ranges for fetal thymus and thymus:body volume ratios between 20 and 32 weeks of gestation. Fetuses that deliver very preterm had reduced thymus volumes when standardized for fetal size. A reduced thymus volume was also a predictor of spontaneous preterm delivery. Thymus volume may be a suitable marker of the fetal inflammatory response, although further work is needed to assess this, increasing the sample size to correlate the extent of chorioamnionitis with thymus size. Calculation of volumes of the gland using magnetic resonance imaging (MRI) obviates some of these difficulties and has successfully been used to evaluate the fetal thymus, both in uncomplicated pregnancies and in those with fetal growth restriction.10 More recent MRI advances have enabled reconstruction of the fetal thorax to further account for unpredictable fetal motion, so improving the accuracy of volumetric assessments.11The thymus plays an integral role in the development of the fetal immune system, being the main site of T-cell production and development, and has been suggested as a marker of the fetal inflammatory response,This study aims to investigate if alterations in thymus volume occur in fetuses that are delivered preterm and if there are associations between the size of the gland and the presence of chorioamnionitis at delivery. This will be achieved by: (a) generating MRI-derived normal ranges for thymus volume, and thymus volume standardized for fetal size, in uncomplicated pregnancies between 20 and 32 weeks of gestation; (b) comparing thymus size in fetuses that deliver very preterm, standardizing for fetal body volume; (c) assessing thymus size as a predictor of PTB; and (d) correlating the presence of chorioamnionitis and funisitis at delivery with thymic volumes in utero in fetuses that subsequently deliver preterm.2This study was conducted at a large London teaching NHS Foundation Trust hospital. Women at high risk of preterm delivery were prospectively recruited with written informed consent between December 2015 and March 2020 .12) or women with PPROM, confirmed on clinical assessment at vaginal speculum examination. High-risk asymptomatic women were recruited from the Preterm Surveillance Clinic and women with PPROM were recruited from the antenatal ward or Maternity Assessment Unit. Exclusion criteria were: fetuses known to have structural or chromosomal abnormalities, multiple pregnancies, active labor, maternal inability to give informed consent, pregnancy complications including preeclampsia and fetal growth restriction, and contraindications to MRI such as claustrophobia or a recently sited metallic implant.Inclusion criteria were: gestational age 20-32 weeks and high-risk of PTB. This included either asymptomatic women with a history of previous PTB, late miscarriage >16 weeks, or cervical surgery with a >50% risk of PTB in the next 2 weeks  with a 32-channel coil placed around the mother's abdomen. Imaging of the entire uterus to include whole fetal body and thorax was performed: T2 weighted single-shot turbo spin echo (ssTSE) images in three or more orthogonal planes re-orientated with respect to the fetus/uterus were acquired. The following scanning parameters were used: TR = 25 991 ms, TE = 80 ms, slice thickness of 2.5 mm, slice overlap of 1.25 × 1.25 × 1.25 mm on 1.5T, and 1.21 × 1.21 × 1.5 or 1.25 × 1.25 × 2.5 mm on 3T, with a flip angle = 90°. Three-dimensional (3D) MR images of the fetal thorax were obtained from 4-8 motion corrupted T2 MRI stacks using the deformable slice-to-volume reconstruction method.http://itksnap.org)16 and 3D Slicer (version 4.10.2 https://www.slicer.org)17 17 . Intra- www.iFINDproject.com), the Placental Imaging Project (www.placentaimagingproject.org) and ‘Antenatal assessment of fetal infection utilizing advanced MRI protocols’. All women had given informed written consent to allow their imaging data to be used. Cases were selected from uncomplicated pregnancies where the MRI was performed between 20+0 and 32+0 weeks of gestation and delivery occurred >37 weeks of gestation. All fetuses had undergone the same imaging protocol described above on a 1.5 Tesla or 3 Tesla scanner (Phillips) and had thymus and body volumes reconstructed using the same protocols.A control group was identified from three other studies: the intelligent Fetal Imaging and Diagnosis project  were generated for low thymus:body volume ratio and low gestation adjusted thymus volume centiles as predictors of PTB.Data were assessed for normality using distributional plots of standardized residuals. Demographic and neonatal outcome data were analyzed using a Student t test where data were continuous and chi-squared test where the data were categorical. For the control cases, the Wright and Royston xrimel method was used to estimate normal growth trajectory of thymus volume and thymus:body volume ratios between 20 and 32 weeks of gestation.We estimated the difference between fetuses that delivered preterm and those that delivered at term in thymus and body volumes and thymus:body volume ratios adjusting for the effects of gestation and the strength of the magnet by multiple regression.2.2This study was conducted under the ethics numbers 07/H0707/105 (dated 29 October 2007), 14/LO/1806 (dated 25 January 2015), 19/SS/0032 (dated 7 March 2019). All regulatory approvals were obtained before commencing the research.2Recruitment for this study can be seen in In addition, 80 control cases were identified. All of these pregnancies were delivered after 37 weeks of gestation and were scanned on a 1.5T (50 cases) or 3T (30 cases) scanner using similar protocols: 3D reconstruction of the fetal body was performed for each of the data sets.Clinical characteristics of the group that delivered preterm and the control group are denoted in P < .001).11 Although numbers are small the finding that thymus volume and thymus:body volumes were smaller persisted in the preterm cohort in both fetuses with ruptured membranes and those with membranes intact.The gestation-adjusted thymus volume centiles and the thymus:body volume ratio were tested as predictors of PTB . FetusesAlthough the numbers are small, the relation between thymus volume and the presence of funisitis can be seen in +0 weeks of gestation with a reduced thymus:body volume ratio of 0.011. The mean number of days from MRI to delivery in the preterm group was 10.5 (SD 14.2). Two fetuses from the control group that delivered >37 weeks were admitted to the neonatal unit, one for a few hours only with suspected respiratory distress syndrome and the second for 2 days with hypoglycemia.There was one intrapartum death at 224We have reported normal ranges for MRI-derived fetal thymus volume between 20 and 32 weeks of gestation, finding that absolute thymus volumes and thymus:body volume ratios increase with gestation in uncomplicated pregnancies. We have also demonstrated a smaller thymus volume in fetuses that subsequently deliver very preterm. This finding persists when thymus volume is standardized for the overall body volume of the fetus. Where histology was available, 85% of the preterm cases showed evidence of chorioamnionitis and 69% had evidence of funisitis.21 funisitis,6 and elevated cord blood interleukin-6 levels at delivery6 have previously been reported in women with PPROM. Assessment of the transverse diameter of the thymus has also been investigated as a predictor of neonatal sepsis, a measurement <5th centile having a sensitivity of 100%, specificity of 73%, positive predictive value of 55%, and negative predictive value of 100% in detecting subsequent early neonatal sepsis.22The findings, of a small thymus in fetuses with PPROM, are in accordance with previous US studies. Associations between a reduction in length of the fetal thymic perimeter, <5th centile, measured on an axial 2D ultrasound image, and chorioamnionitis,23 The thymus diameter was assessed using 2D ultrasound, and amniocentesis was performed to assess for microbial invasion of the amniotic cavity. Placentas were then assessed for histological evidence of chorioamnionitis at delivery; 32.3% of women had intra-amniotic infection and 51.6% had evidence of placental chorioamnionitis. Isolated histological chorioamnionitis and funisitis were found in 22.6% and 25.8% of fetuses, respectively. In all cases of intrauterine infection and 23.8% of cases without intrauterine infection, the fetal thymus perimeter was <5th centile for gestational age. The fetal thymus was <5th centile for gestational age in 100%, 71.4% and 12.5% of women with histological signs of funisitis and isolated chorioamnionitis, and without histological signs of infection, respectively.23 This again is in accordance with this study's findings of a smaller thymus size in fetuses that subsequently deliver preterm. The numbers in this study are too small to find exact associations between the thymus volume and the presence of chorioamnionitis; however, there was a trend towards a smaller thymus in fetuses delivering very preterm with evidence of funisitis.A reduction in fetal thymus perimeter has also been found in women at high risk of PTB but with intact membranes, which correlated with the presence of both intrauterine infection and chorioamnionitis at delivery.9 It should be noted that the median gestational age at imaging was 20.5 weeks and very few of the PTBs occurred very early in gestation, hence the infective/inflammatory processes may not have commenced at the time of this initial scan.In contrast to these findings, Brandt et al prospectively assessed the fetal thymus in 520 pregnancies using 2D ultrasound, measuring the transverse and anterio-posterior thymus diameters and the thymic:thoracic ratio. Of this population, 12.3% underwent PTB; however, there was no correlation between thymus size and premature delivery.24All of the previous studies, however, have only evaluated the thymus using two-dimensional parameters. Its shape is variable and volumetric assessment provides a more complete evaluation of the size of the gland because of its lobular nature. A previous study by Li et al compared 2D and 3D ultrasound measurements of the thymus, finding that the correlation between thymus volume and gestational age was significantly stronger using 3D volume measurement than that of any of the 2D parameters evaluated.26 and in those with growth restriction,27 to our knowledge our study is the first to assess thymus volume, using either modality, MRI or ultrasound, in pregnancies at high risk of PTB. MRI may be a superior imaging modality in this cohort of fetuses, particularly those with ruptured membranes as oligohydramnios and unfavorable fetal lie can give inadequate visualization of the gland.6Although thymic volume has previously been assessed using 3D ultrasound in uncomplicated pregnancies7 Where there was evidence of chorioamnionitis, the thymus revealed more advanced signs of cortical shrinkage and lobules were more separated, confirmed by fractal dimension analysis. Although there was variation within the group this was thought to be attributable to the differences in the length of exposure to in utero infection. Term and preterm neonates who died of sepsis all had thymuses that were almost completely devoid of thymocytes and with irregular narrowing of the cortex.Although further work is required to assess the relation in more detail, thymus volume may be reduced in fetuses at high risk of PTB because of alterations in the structure of the gland occurring in the presence of fetal compartment infection. Toti et al undertook histological assessment of the thymus in a number of late miscarriages and PTBs resulting in fetal demise/neonatal death due to sepsis with evidence of histological chorioamnionitis (n = 40).28 However, these findings, and the lack of histological changes in the gland, may be attributable to the fact that the sheep model gave a single dose of lipopolysaccharide whereas the antenatal insult may be more extensive and prolonged in clinical practice.In contrast, in a sheep model, following lipopolysaccharide-induced chorioamnionitis, no histological changes in the thymus or changes in markers of apoptosis and proliferation in the thymoctes were identified. However, as was the case in our study, thymus:body-weight ratios were reduced by 40% 5 days after lipopolysaccharide administration. Blood lymphocytes were also found to be 40% lower than the control group after 1 day and elevated at 5 days.29 Further work is also required to correlate the imaging findings with markers of infection in both placental histology and umbilical cord blood and both short-term and long-term postnatal outcomes. In this study, the thymus was not the primary focus of all of the investigations and in 24% of cases a thymus volume could not be reconstructed. Acquisition techniques have been optimized and we would anticipate this percentage being significantly lower in the future. In addition, MRI studies in the future could include additional sequences to detect microstructural and perfusion alterations within the thymus that may also be associated with a reduction in volume and the presence of funisitis.At present, numbers within this current study are small, the timing between the MRI scan and delivery varies, and placental histology was not available in all cases. The slight difference in the gestation at which the MRI was performed between cases and controls is a limitation of the study; however, it has been adjusted for in the analysis. Furthermore, the presence of confounding factors such as the timing of steroid administration, which has been shown to alter the structure of the gland in an ovine model of chorioamnionitis, needs to be considered in a larger sample.5We have reported normal ranges, between 20 and 32 weeks of gestation, for thymus volume and thymus volume standardized for fetal size derived from healthy fetuses that subsequently delivered at term. Thymus volumes are smaller in fetuses that subsequently deliver very preterm, a finding which persisted after standardization for fetal size. Although numbers were too small to compare fetuses with and without chorioamnionitis/funisitis at delivery it may be reflective of thymic involution as a consequence of infective/inflammatory processes in the in utero environment, which are also associated with the etiology of preterm delivery. Thymus volume and thymus:body volume ratio also appeared to be good predictors for preterm delivery. Further evaluation is needed to assess the utility of thymus volume as a marker for the fetal inflammatory response both using MRI and using ultrasound. MRI potentially has the advantage over ultrasound as it can provide visualization of the whole gland, particularly in pregnancies where ultrasound images may be suboptimal such as those involving oligohydramnios, raised body mass index, and unfavorable fetal position, and can provide more insight into tissue microstructure and perfusion. Evaluation of the thymus shows potential to help to inform the timing of delivery where there is clinical uncertainty regarding the presence of fetal compartment infection. It may also serve as a marker of fetal compartment infection in pregnancies where there has been instrumentation of the uterine cavity, such as in cases of fetal surgery.


Couto, MD (Video).Please watch a video commentary on “The Combined Effect of Intravenous and Topical Tranexamic Acid in Liposuction: A Randomized Double-Blinded Controlled Trial”


Most people encounter art images as digital reproductions on a computer screen instead of as originals in a museum or gallery. With the development of digital technologies, high-resolution artworks can be accessed anywhere and anytime by a large number of viewers. Since these digital images depict the same content and are attributed to the same artist as the original, it is often implicitly assumed that their aesthetic evaluation will be similar. When it comes to the digital reproductions of art, however, it is also obvious that reproductions do differ from the originals in various aspects. Besides image quality, resolution, and format, the most obvious change is in the representation of color. The effects of subjectively varying surface-level image features on art evaluation have not been clearly assessed. To address this gap, we compare the evaluation of digital reproductions of 16 expressionist and impressionist paintings manipulated to have a high color saturation vs. a saturation similar to the original. We also investigate the impact of viewing time (100 ms vs. unrestricted viewing time) and expertise (art experts vs. laypersons), two other aspects that may impact the perception of art in online contexts. Moreover, we link these dimensions to a recent model of aesthetic experience [the Vienna Integrated Model of Top-Down and Bottom-Up Processes in Art Perception (VIMAP)]. Results suggest that color saturation does not exert a major influence on liking. Cognitive and emotional aspects , however, are affected – to different extents for experts and laypersons. For laypersons, the increase in color saturation led to more positive assessments of an artwork, whereas it resulted in increased confusion for art experts. This insight is particularly important when it comes to reproducing artworks digitally. Depending on the intended use, increasing or decreasing the color saturation of the digitally reproduced image might be most appropriate. We conclude with a discussion of these findings and address the question of why empirical aesthetics requires more precise dimensions to better understand the subtle processes that take place in the perception of today’s digitally reproduced art environment. Perceiving digitally reproduced images has become an indispensable part of our media-suffused everyday life. Digital reproductions specifically play a significant role in people’s encounter with works of art. For many viewers, their first encounter with an artwork does not take place in front of the physical artifact in a gallery or museum. Artworks are rather often first perceived as reproductions presented in a digitized form, selected, and compiled by a search engine on the Internet. Such reproductions resemble the original – more or less – and are often thought to be identical to the original artwork. But, digital reproductions of the same painting may differ in several ways, as shown in In digital reproductions, color is one of the image features expected to differ the most , especiaTo date, only a few studies have investigated the influence of color saturation on the liking of digitized images of art. To address this gap, we provide empirical evidence of the relation between color saturation, expertise, and viewing time. The present study compares high-quality digital color reproductions of impressionist and expressionist works with matching versions of the same paintings with increased saturation. The effect of color saturation is assessed with regard to both general hedonic liking and various aesthetic outcomes tied to later processing stages . Based oIn our results, we demonstrate that color saturation does not exert a major influence on liking. Cognitive and emotional aspects , however, are affected. As such, our findings suggest that the evaluation of more specific aesthetic reactions is needed to clearly depict the effect visual variables may have on the evaluation of digitized art images. Moreover, we show that color saturation affects viewers differently depending on their expertise in the field of art. While laypersons are positively influenced by increased color saturation, high saturation has a negative influence on experts’ evaluations. Also, and in contrast to previous studies e.g., , we showInvestigating the effect of color saturation in digitized images on the evaluation of art may enable us to further highlight differences in the assessment processes of art experts and laypersons. Furthermore, our findings may encourage art museums and galleries to carefully adjust the color saturation of digitized art images they use on websites or as merchandising products.In the following, we summarize existing research on the aesthetic processing of digitized art images. We also provide an overview of empirical research on color saturation, viewing time, and the relative expertise of the viewer, from which we derived the research questions for our study.The differences between original artworks and different reproductions, including digitized art images, have been empirically studied . Siri etWhen it comes to saturation preference in general, studies have shown that Western adults prefer more saturated colors over less saturated colors, provided the color is not “too vivid” . These pSaturated colors are also preferred when it comes to the evaluation of digital images. The aesthetic quality of digital images affects the attractiveness of websites and subsequently influences viewer behavior . RegardiModels of aesthetic perception e.g.,  describeDue to the mixed evidence, it is unclear to what extent saturation – a feature that can be easily changed in digitally reproduced art images – affects aesthetic evaluation. It is, thus, not yet possible to sufficiently explain the influence of saturation on either the initial assessment or subsequent cognitive and emotional processing of digitized art images.According to cognitive models of the perception of art , short-tStudies have shown that aesthetic judgments are made very quickly . ResearcAccording to models of aesthetic perception , the timThere is evidence that experts and laypersons differ in their aesthetic judgments . “ExtensRecent studies have investigated the consistency of expert judgments. Expert and lay judgments are affected by viewing time. via considerations based on basic circumplex models  proposed by According to VIMAP, the emotional and cognitive elaboration of an artistic stimulus occurs at a later stage than the purely visual evaluation of the stimulus that happens within the first 100 ms of perception. The influence of color saturation on emotional and cognitive reactions to an image should thus be assessed only when the image is processed top-down and can be perceived for an unlimited time. With regard to the relative expertise of the viewer, models of aesthetic perception  offer liDigitally reproduced art images are said to be similar to the originals, especially when it comes to specific aesthetic qualities of the image like color intensity, yet a difference is visible in terms of emotional reactions . PreviouCompared to laypersons, we expect art experts to be less influenced by the manipulation of the image surface , whereas laypersons’ liking of digitized images will be influenced by color saturation.Moreover, the effect of color saturation on liking will be more strongly influenced by viewing time in the case of experts than in the case of laypersons, as predicted by models of the cognitive processing of aesthetic stimuli .We further expect that the manipulation on color saturation will be more visible with regard to specific emotional reactions  than with regard to liking.The study followed a quasi-experimental mixed-subject design. The independent variables were saturation , expertise (art experts vs. laypersons), and viewing time (100 ms vs. unlimited).ageM = 23.24, SD = 5.27, and range = 19–50; all lay viewers of art as assessed via post study interviews the Vienna art interest and art knowledge questionnaire (VAIAK); ageM = 27.25, SD = 7.42, and range = 18–62; considered to be relatively expert viewers of art) participated in the experiment. Participants were asked to inform the experimenter about any vision impairments that were not corrigible to normal with glasses or contact lenses. Participants were also asked to inform the experimenter if they had an abnormal color vision. One participant stated that he could only see with one eye and was therefore excluded from the analysis.Seventy-two psychology students from the University of Basel  from the Aesthemos  were disvia the 11-item “interest” battery from the VAIAK . Thus, all data were retained for analysis. For all statistical tests throughout the paper, we used an alpha level of 0.05. Due to the exploratory nature of the study, no adjustments for multiple comparisons were performed.All participants completed all portions of the study. The test-retest reliability, as measured by the repeated images in block 1, showed that all image ratings had good reliability  than laypersons . Experts were also able to list significantly more painters within 60 s  than laypersons .As expected, VAIAK  scores iTo evaluate the effects of saturation, expertise, and viewing time on image liking, a repeated-measures ANOVA was calculated. Saturation  × viewing time (100 ms vs. unrestricted) were defined as within-participant factors and expertise (experts vs. laypersons) as a between-participant factor. F = 3.995, p = 0.047, η2p = 0.027], with more highly saturated images liked more than the original ones across all participants. No significant main effects were found for either expertise  or viewing time . The results did reveal, however, a significant interaction between expertise × saturation . Compared to experts , laypersons liked more saturated images  over less saturated images . A significant main effect was detected for saturation . Post hoc comparisons within the expertise groups showed that the effect on liking was driven by a significant saturation effect in the laypersons group  but not in the experts group . Viewing time had no significant impact on laypersons’ liking  or on art experts’ liking .Moreover, we found a significant three-way interaction between saturation × viewing time × expertise . Furthermore, experts took longer to view and evaluate the images in the unrestricted time condition (block 2). Experts spent around 62.44 s (median) per image, whereas laypersons only spent around 44.72 s (median). As requirements for a t-test were not met , a nonparametric test was calculated: a Wilcoxon-Mann-Whitney test revealed a significant difference between the groups , with an effect size of r = 0.44, which according to Mean ratings over all images show that laypersons were more consistent in their judgments across both viewing times  that cover aesthetic assessments beyond basic liking. As listed in Moreover, significant saturation × expertise interactions were found for all dimensions, except “surprise” and “insight.” With regards to “interest,” laypersons found images with increased saturation more interesting, whereas experts found them less interesting. A similar pattern was observed for “being moved”: laypersons found images with increased saturation more moving, and experts felt less moved. In contrast, with regard to “boredom,” experts rated original and manipulated images to a similar degree, whereas laypersons found the original images more boring. Finally, concerning “confusion,” experts rated images with increased saturation as more confusing, perhaps because the colors did not match their expectations of the artistic style or of similar art, whereas, for laypersons, increased saturation did not have an effect.An innumerable variety of digitized art images can be found online that may differ substantially from the original in terms of several features, even though they show the same image content and are attributed to the same artist. We conducted a study that reflects a similar encounter with digitally reproduced art. Our focus was to manipulate color saturation (using a matched condition of both high-fidelity versions and increased-saturation versions of the same paintings) – an image component that substantially varies in digital reproductions of art images on the Internet  – and toWe found a main effect for color saturation – more saturated images were liked relatively more when compared within-participants – that extended across both expertise levels and both during short and unrestricted viewing times. The results reflect earlier findings that saturated colors are preferred in general  supports the argument that saturation is one of the features of images that may be processed first, almost immediately following viewing an image. This is in line with the findings of Interestingly, one could argue based on our results that, despite its small effect size, saturation may have an impact when considered at the level of basic hedonic  responses, which may not themselves change or may even inform subsequent analyses. Laypersons’ first impression of an image is in strong accordance with their liking of the artwork, even when there is enough time to contemplate and evaluate it. At the same time, as suggested above, our results also show that art experts are not quite as consistent in their liking of judgments in very short vs. unrestricted viewing times. This is in contrast to Additionally, investigating the perceived visual complexity of the artworks may serve to further differentiate image processing between different levels of expertise and viewing times: for instance, visual complexity and colorfulness have been found to shape viewers’ first impressions differently, depending on their age and education level, respectively . MoreoveThe present study supports previous theoretical arguments about aesthetic reactions or features of aesthetic experience beyond basic hedonic liking. As our results show, the effects of saturation manipulation only became apparent when participants were asked to rate their aesthetic reactions to the artworks. Alternatively, our findings reveal that aesthetic reactions indicating an outcome paraphrased by easy-to-achieve positive or also negative sensations on VIMAP showed significant effects. Interestingly, the specific dimensions we looked for in our study showed significant differences according to the manipulation of saturation, and they also revealed differences between experts’ and laypersons’ evaluations of the images. As shown in It should also be noted that the observed effect sizes were rather small. In line with the VIMAP stages of higher-order cognitive processing , we did More generally, we argue that in studies of empirical aesthetics, the dimension of liking may not be precise and differentiated enough to adequately reflect and evaluate the perception of art images. In our study, the evaluation of liking could not reflect the diverse dimensions of perceiving an image that were affected by manipulating color saturation, neither in the perception of experts nor in that of laypersons. Including more differentiated and specific factors than liking gave a more detailed impression of the effect of color saturation on the perception of an artwork. We conclude that asking only about the liking of an artwork is not specific enough to evaluate responses to an art image. More research is needed to carefully examine the processes occurring in interaction with art and to analyze specific aesthetic reactions in detail.In the following, we address the main limitations of our work and discuss avenues for future work. First, our study employed only a small range of artistic styles (impressionism and expressionism) and a limited pool of viewers. Findings might differ for other image contents or styles, especially if color plays a substantial role in the artwork  familiarity. Future studies on the effects of color saturation should consider including familiarity as a covariable, as it is a known predictor of image liking .In our study, we wanted to investigate the effect of altered saturation as an image feature that often varies unintentionally in digitally reproduced art images on the Internet. In that context, however, images are rarely seen in isolation. The isolated presentation of images in the present study may thus be seen as a limitation in recreating the real situation of how images are seen on the Internet. To investigate the effect that juxtaposed images have on each other is the content of our next study.In summary, it can be said that whenever a digitized artwork is downloaded from the Internet, the choice of a single version of color saturation out of countless variations exerts an influence on the reception of the image and thus needs to be controlled carefully.The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.Ethical review and approval was not required for the study on human participants in accordance with the local legislation and institutional requirements. The patients/participants provided their written informed consent to participate in this study.CR, MP, KO, and EM contributed to conceiving and designing the study. TT carried out the measurement of color saturation on the image stimuli. CR prepared the study and collected the survey data. CR and EM performed the statistical analysis. CR, MP, and EM wrote the first draft of the manuscript and wrote the sections of the manuscript. All authors contributed to the article and approved the submitted version.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Drowning is one of the most important causes of deaths from injuries in the world, and among adolescents. Although drowning is one of the major public health threats, it can be prevented by knowing its effective factors. Purposes: This study aims to investigate the effective factors of near-drowning in junior high school students, based on Theory of Planned Behavior.This cross-sectional study was conducted in 2018 in Guilan province, north of Iran. Of the seven coastal cities, three cities were randomly selected as samples. The data gathering tool was a researcher-made questionnaire including questions about demographic variables, knowledge and constructs of the Theory of Planned Behavior  and near-drowning. After confirming the validity and reliability, students completed the questionnaire. 734 students were randomly selected using multi-stage cluster sampling. Data were analyzed using logistic regression, linear regression and SPSS-16 software.21.1% of the students had near-drowning experience. 59.4% of the injuries were occurred in the sea and the rest of them were in pool, river, dam, pond, bathtub, well and canal. Most of the injuries were occurred at 4-8p.m (35.5%). Near-drowning following swimming (41.3%), playing and recreation (23.9%), and diving (12.3%) were the most common mechanisms. Logistic regression showed a significance between sex (p = 0.000), father s education (p = 0.005), place of residence (p = 0.000), swimming skills (p = 0.003), intention (p = 0.020) and near-drowning. Also linear regression revealed a significant relationship between attitude and drowning prevention behaviors (p = 0.018).In the studied population, the near-drowning rate is high. Considering most of the injuries occurred in the sea following swimming, accurate knowledge of all effective factors of near-drowning will help design appropriate interventions to prevent drowning in adolescents, including beach safety, setting time for swimming in the sea and swim training.Drowning; Injury Prevention; Safety promotion; Health promotion


Malnutrition is a significant risk factor for ill health among children under 5 years of age and the consequences are significant.The aim of this study was to determine the prevalence and factors associated with malnutrition among under-5-year-old hospitalised children.This study was set at Sebokeng, Kopanong and Heidelberg hospitals, Sedibeng district, South Africa.This was a cross-sectional study comprising 306 hospitalised under-5-year-old children. Information on socio-demography, feeding practices, immunisation and clinical problems was obtained from caregivers and medical records. Anthropometric measurements were also performed.n = 29) of admissions. Among these, 82.8% (n = 24) had severe acute malnutrition. On test of association, monthly household income (p = 0.01), mother’s and father’s employment status , breastfeeding history (p = 0.01) and having diarrhoea in index admission (p = 0.01) were significantly associated with malnutrition admission. In multivariate regression analyses, not being breastfed  and diarrhoea at index admission were independently associated with malnutrition .Most participants were male (59.8%), had normal birth weights (80.0%), come from a household with a monthly income R2000 (about 150 US dollars) (50.3%), up-to-date immunisation (97.4%), breastfed for 6 months (57.4%) and were fed 3–4 meals/day (66.7%) and, at most, one snack/day (63.4%). Acute malnutrition accounted for 9.5% (A significant proportion of participants had malnutrition and were subjected to suboptimal feeding practices. Healthcare providers in primary care need to entrench dietary education and anthropometric screening in all clinic visits for children 5 years old, particularly when they present with diarrhoea or are not being breastfed. However, the geographical landscape typical of South Africa means that peri-urban informal settlements also experience socio-economic deprivations, and sometimes even worse than in rural areas. While Gauteng province is the economic hub of South Africa, there are several pockets of socio-economically deprived communities within this success story. Of the five health districts in the Gauteng province, Sedibeng is the most economically challenged with several communities typical of this socio-economic deprivation.8 Data from the district health information system (DHIS) in 2015 and 2016 indicate a very high in-hospital case fatality rate of 13.8% among children younger than 5 years, a significant proportion of which is because of severe acute malnutrition (SAM).9 Such high fatality rate raises serious clinical and public health concerns and makes it imperative to explore factors that may be influencing malnutrition in this district. The aim of this study was therefore to determine the prevalence and factors associated with malnutrition among under 5-year-old children admitted to the three public hospitals in Sedibeng District, South Africa.In South Africa, several studies have examined the prevalence, associated factors, impact and the double burden of malnutrition (underweight and overweight).This was a cross-sectional study with analytical component.This study was conducted at the paediatric wards of Heidelberg, Kopanong and Sebokeng hospitals. The first two are district hospitals with 126 and 248 beds, respectively, while Sebokeng is a regional specialist hospital with 800 beds.9 Assuming a confidence interval (CI) of 95%, a sampling error of 5% and a response distribution of 50%, the minimum sample required for this study, as determined using Raosoft sample size calculator,10 was 306. This sample was proportionally divided among the three hospitals, based on their contribution in 2014 and 2015 to the total number of admissions. This resulted in 78 children being sampled from Heidelberg Hospital, 81 from Kopanong Hospital and 148 from Sebokeng Hospital.All children aged 1–59 months admitted to the paediatric wards of the three hospitals from 15 March to 15 May 2016 were eligible for the study. During 2014 and 2015, 153 of 1463 (10.5%) of the children aged 1–60 months admitted to the three hospitals were for malnutrition.Participants were consecutively recruited during admission. Caregivers were approached and briefed by the ward clerk or research assistant on the nature and purpose of the research. Each carer was invited to participate, and assent and consent obtained from parents or legal guardians. If a caregiver did not want to participate, the next caregiver was approached, and recruitment continued until sample size was reached over a period of 2 months. Children who were too sick to participate and those admitted to the intensive care unit were excluded.Prior to proceeding with data collection, the first author trained the research assistant and ward clerk on the aim and objectives of the study, and how to administer the questionnaire independently. Where the participants could not speak English, the research assistant or ward clerk interpreted for the researcher.11 was used for data collection, after permission was obtained from the authors. The following sections of the questionnaire were adapted to address the aim and objectives of this study:A researcher-administered questionnaire adapted from a previous studyThe question on religion listed under caregiver’s characteristics was removed.The questions relating to the source and quality of water, dietary practices, diarrhoea, health characteristics and immunisation were adapted to local contexts.Caregivers were approached by the ward clerk as part of his normal duties of obtaining information from patients and capturing this electronically. After the consent form was signed, the questionnaire was administered by the research assistant alone or in the presence of the researcher. Interviews were conducted within 2 days of admission to avoid significant changes in anthropometric parameters. Each interview lasted a maximum of 30 min.Data collected included information on each participant’s demographic profile, household, socio-economic status and medical conditions. Additional information on socio-economic status, clinical condition, environmental condition, breastfeeding and dietary practices was extracted from the child’s medical records. Anthropometric parameters  were measured by the first author. Other information such as immunisation and deworming status and previous episodes of clinic attendance for illness were collected from the Road-to-Health Card (RTHC).Each participant was given a unique code. Data from all completed questionnaires were captured into a secured computerised file. Only the research team had access to this information.Data were captured onto Microsoft Excel spreadsheets and imported into STATA statistical analysis software, version 14.0, with the assistance of a statistician. Descriptive statistics were used to summarise participants’ socio-demographic, clinical, dietary and anthropometric characteristics. These were reported as frequencies, percentages  and means with standard deviations (continuous data). Where data were not deemed normally distributed, medians and interquartile ranges were reported.The proportions of participating children with different categories of malnutrition were determined based on the WHO classification. Moderate acute malnutrition (MAM) was defined as a standard deviation of less than –2 for height-for-age (stunting) or for weight-for-age (underweight). Severe acute malnutrition was defined as a standard deviation of less than –3 for weight-for-height.p < 0.05.The sample was divided into two groups: those who were wellnourished and those who were malnourished (MAM or SAM). These were compared by using Pearson’s Chi-square test and logistic regression in terms of socio-economic, dietary and clinical characteristics. Where statistically significant associations were detected, further analyses were carried out by using multivariate logistic regression to determine factors independently associated with malnutrition. Statistical significance was taken as Ethics clearance was obtained from the Human Research and Ethics Committee of the University of the Witwatersrand (Number M161041). Permission was obtained from the Sedibeng District Health Services management. To ensure anonymity, questionnaires were coded and did not collect personal identifiable data.n = 148) and district hospitals   see .As shown in n = 120). However, at the time of the study, most were no longer breastfeeding (74.6%) and many had stopped because the child was sick  or there were breast problems in the mother . Although supplementary foods were started for most participants between 6 and 9 months of age (73.6%), one in five (19.1%) were on supplementary feeds before the age of 6 months. Most participants (66.7%) were fed only three to four meals a day and had at most one additional snack per day (63.4%).In terms of diet, most participants were reportedly breastfed for > 6 months of age  and were aged 18–35 years (84.0%), single (66.0%) and unemployed (71.2%). In contrast, most of the fathers were employed (60.1%). Most households had four or less dependents (77.5%), private water source (69.9%) and total≈monthly income of 2000 Rands ($150) or less (50.3%)  .n = 29) of study participants were categorised as being malnourished, of whom 82.8% (24) had SAM  (interquartile range [IQR]: 6.4–11.8), 75 centimetres (cm) (IQR: 61–88) and 14 cm (IQR: 12.3–15), respectively. By using the WHO classification, 9.48% ( had SAM .p < 0.001) or mothers (p = 0.002), those breastfed (p < 0.01) and those from households with income > R2000 per month (p < 0.001) were significantly less likely to be admitted for any category of malnutrition. On the contrary, participants who presented with diarrhoea (p < 0.001) were significantly more likely to be admitted for malnutrition , mother’s employment status (p = 0.02), household income (p < 0.01), child’s breastfeeding status (p < 0.01) and presenting medical problem (p < 0.01) were significantly associated with admission for malnutrition.On tests of association, father’s employment status (p = 0.02) and those who presented with diarrhoea on admission  were significantly more likely to be admitted for any category of malnutrition. The strengths of these relationships were stronger for SAM only; compared with others, participants who were not breastfed  and those who presented with diarrhoea on admission  were significantly more likely to be admitted for SAM.In the final multivariable regression analysis , compareThis study revealed a high prevalence of acute malnutrition (9.4%) with most children affected (82.8%) suffering from SAM. In addition, the feeding practices offered to the children in the study were poor and placed them at significant risk of malnutrition. Although household income and parents’ employment status appeared to influence malnutrition, having diarrhoea at presentation and a history of not being breastfed significantly increased the risk of malnutrition.12 a prevalence of 9.4% is still high and has serious clinical and public health implications. According to the DHIS in Sedibeng District, the case fatality rate is high (2.4%).9 Put together, both findings suggest that children at risk of malnutrition are not being identified early for intervention in primary care. Strategies that compel healthcare practitioners in primary care to screen for malnutrition such as including anthropometric measurements  as part of the vital signs during every clinic visit by a child are needed to improve early detection of malnutrition. Those found to be at risk should be immediately referred to a dietician for appropriate interventions and linked with the ward-based outreach team for follow-up at the community level.Although a prevalence of malnutrition of 26.0% has been reported in a study conducted in the same age group in Cape Town,12 However, only 57.4% were breastfed for at least 6 months – the commonest reasons for stopping early being sickness of the mother or the baby (32.1%) and breast problem (26.2%). Considering that 71.2% of mothers were unemployed, mothers ought to have had enough time for exclusive breastfeeding for 6 months. To compound the problem of poor nutritional practices, 19.05% of children were started on solid foods before 6 months of age. The later practice has been reported to have detrimental effects on the health of infants.13 The feeding practices found in this study therefore suggest the need to intensify dietary education and promotion of breastfeeding during antenatal care visits, more so, that a history of not being breastfed significantly increased the risk of malnutrition in this study.That 70.2% of children in this study were breastfed at all is a welcome finding and may reflect the strength of the campaign on exclusive breastfeeding by the South African Department of Health.14 Although this could be because of unavailability of food and poor knowledge on diet, it raises serious concerns considering that inadequate food intake is a risk for malnutrition that, in turn, predispose to physical and cognitive underdevelopment and poor quality of life.14 In the first 6 months of life, promoting exclusive breastfeeding given on demand or at least every 2 h and the provision of dietary education have the potential to increase the number of meals per day found in this study. Beyond 6 months, dietary education at the clinical coalface and empowerment of community health workers to teach carers the correct feeding practice are interventions that could address the small number of meals. At systems level, inter-sectorial collaboration across government departments may address socio-economic depravities and promote access and judicious use of social grants, food banks and female self-reliance through small-scale businesses.Most participants had three meals on the average per day and, at best, an additional snack per day. This is not only inadequate to support normal childhood development; it falls far short of the daily requirement of six to eight meals recommended for the study population.15 In essence, although screening can identify children at risk for nutritional and clinical interventions, the underlying problem in many cases is socio-economic, and it may therefore be more appropriate to address the socio-economic depravities that place these children at risk of malnutrition through inter-sectorial collaboration highlighted above. This study found that both parents being employed protected against malnutrition and that mothers’ employment did so to a greater extent than the fathers’ (The relationship between poor household income (< R2000 per month) and malnutrition in this study reiterates findings of a previous study that showed parental unemployment linked to poor household income as a risk factor for malnutrition.fathers’  and 6 – p < 0.01) in this study is consistent with findings of other studies17 and indicates the importance of prompts that compel clinicians to do anthropometric measurements in children who present with diarrhoea.The strong association between diarrhoea and malnutrition (OR = 23.3; 95% CI: 6.85–79.43; 17 On the contrary, malnutrition may reduce the effectiveness of Rota virus.19 Although intuitive, it is not clear whether the introduction of Rota virus immunisation has led to any reduction in the prevalence of malnutrition in South Africa.This study reports a very high immunisation coverage, including Rota virus, that has been associated with significant reduction in the incidence of diarrhoea.This was a cross-sectional study and the associations found were only suggestive and not causal in nature. Considering that several study measures relied on self-reports, there is a potential for recall and information bias, with possible misclassifications. Intra-performer variability during anthropometric measurements could also have resulted in a margin of human error that might have affected some study estimates. However, the same researcher performed the anthropometric measurements and adhered strictly to the WHO guidelines. Notwithstanding these potential limitations, the findings of this multicentre study provide an understanding of malnutrition and its associated factors within the context of a typical South African peri-urban health district that are useful for informing interventions in this or similar settings.A significant proportion of participants had malnutrition and was subjected to suboptimal feeding practices. Healthcare providers in primary care need to entrench dietary education and anthropometric screening in all clinic visits for children < 5 years old, particularly when they present with diarrhoea or are not being breastfed.


The aims of the present study were: 1) to calculate the change of direction (COD) deficit (using a modified version of the 505 test and 10 m sprint time), and (2) to examine the differences in linear sprint, jump and COD performances, as well as COD deficit, between under-13 (U13) and under-15 (U15) male handball players.One hundred and nineteen young male handball players . Tests included anthropometric measurements, countermovement jump (CMJ), triple leg-hop for distance, linear sprint test , and a modified version of the 505 COD test.P < 0.05) in age, predicted age at peak height velocity (APHV), distance from PHV (DPHV), height, and body mass between the age categories. Moreover, U15 players demonstrated higher performances in all jump tests and lower sprint times in 10- (ES = 0.84) and 20-m (ES = 0.51) and a higher 505 deficit (ES = 0.38) than the U13 players (P < 0.05). However, no significant differences were observed for the 505 COD test between groups .Results showed moderate to very large differences (Our results suggest that during the transition from pre- to post-puberty, young handball players should focus on transferring their progressive improvements in strength, speed, and power capacities to COD performance. Handball is an intermittent sport, which requires good levels of different physical qualities, such as endurance, strength, speed, and coordination . In termAlthough COD performance has been considered one of the most important physical qualities in a wide variety of team-sports, including handball ,6–8, infIn order to assess the strengths and weaknesses of a given player, standardized physical measurements are commonly used to provide useful, and more precise information, to subjective coaching appraisals of player´s performance . In thisThis cross-sectional comparative study was conducted to compare the physical performance of two different age-categories of handball players (U15 and U13), from a top-level Spanish handball club. Testing sessions were undertaken between 16:30 and 19:00 hours, and players were assessed at their regular training facility. The testing took place in an indoor court . The young athletes were previously familiarized with procedures and assessment routines, which were completed on the same day. In this regard, four days before the measurements, all players participated in a pilot session. The data collected in this session were used to calculate the between-day intraclass correlation coefficients (ICCs). Subjects were required to refrain from any intense physical workout for 24 h before the tests and to be in a fasting state for at least 2 h. The order of assessments was as follows: (1) anthropometric measurements, (2) countermovement jump (CMJ), (3) triple leg-hop for distance, (4) linear sprint test, and (5) modified 505 COD test. Prior to the measurements, athletes performed a standardized warm-up, consisting of jump rope activation, general dynamic mobility, multi-directional accelerations, and submaximal jump attempts.One hundred and nineteen young male handball players took part in this study. For the purposes of the present study, players were grouped into two age groups: U13  and U15 . Subjects were part of the youth categories of Abanca Ademar León handball club and were selected by their respective coaching staff. All players participated in an average of 540 ± 10.1 min of combined handball and physical training per week and had a training background of 5.5 ± 2.8 years. Before taking part in the study, subjects and their parents/guardians were fully informed about the protocol and provided their written informed consent. The Institutional Ethics committee  approved the procedures in accordance with the latest version of the Declaration of Helsinki.Body height was measured using a fixed stadiometer , sitting height with a purpose-built table , and body mass with a digital scale  . PubertaA CMJ without arm swing was performed on a photocell mat  according to the procedures described by Bosco et al. (11). Each player performed two maximal jump trials interspersed with 45 s of passive recovery. Subsequently, the average jump height was calculated and considered for analysis. The ICC of the CMJ was 0.96.The triple leg-hop test requires participants to perform 3 consecutive hops on the same leg aiming for maximum distance . The toeTime during a 20-m sprint (with 5 and 10 m split times) in a straight line was measured by means of single beam photocell gates placed 1.0 m above the ground level . Each sprint was initiated 1.0 m behind the first photocell gate, which then started a digital timer. Players started the sprint test in a standing position with their preferred foot behind the starting line, followed by accelerating forward at maximal effort until they passed the last photocell gate placed at 20 m. Each player performed two maximal 20-m sprints with at least 2 min of passive recovery in between the two trials [COD deficit = (modified 505 test time– 10-m test time) [The ability of athletes to perform a single and rapid 180° directional change over five meters was measured using a modified version (stationary start) of the 505 test . Playersst time) .® software package version 22.0. . Data normality was confirmed using the Kolmogorov-Smirnov test. The differences in age, APHV, MO, height, and weight between the age categories were assessed using an independent t-test. The differences in the physical fitness between U13 and U15 players were analyzed using a univariate analysis with MO as covariate. The statistical significance level was set at P < 0.05. Effect sizes (ES) were calculated to estimate the magnitude of differences in the tested variables and interpreted using the following thresholds: <0.2, trivial; ≥0.2, small; ≥0.6, moderate; ≥1.2, large; ≥2.0, very large and; ≥4.0, almost perfect [Data are presented as means ± standard deviations. The statistical analyses were performed using the SPSSP < 0.05) in age, APHV, MO, height, and weight were observed between the age categories . P < 0.05, considering MO as covariate). No significant differences were observed for the 505 COD test between U13 and U15 groups .Moderate to very large differences  and sprint tests . Regarding COD performance, U15 players also presented a significantly higher deficit , although no significant differences were observed for the 505 COD time between groups. These data may be of great interest and have important implications for practitioners involved in the development and training of young handball players.As expected, U15 players outperformed the younger players (U13) in all performance measurements, which is consistent to previous research describing youth athletes from other team sports  ,24. ThesWhen analyzing the COD test considering DPHV as the covariate, results indicated no significant differences between groups . These findings are supported by previous studies, showing similar COD performance in different age groups of young athletes  ,24,28. TThe U15 athletes demonstrated higher COD deficit  than the U13 players . These data are in agreement with previous studies in team-sport athletes , which showed that faster and more powerful athletes tend to present higher COD deficits (when compared to their slower and weaker peers) ,32,33. TWe have to acknowledge some limitations in the current study, including the lack of a larger sample of young athletes, especially in the U13 group, or having more distinct age groups to examine the evolution of these parameters throughout the players’ development. Another limitation is related to the fact that 505 test involves one single 180° COD and, thus, may not be represent the actual capability of players to successively change direction while playing. The implementation of other drills, using different cutting maneuvers , closer to the movement patterns observed in handball  can be also useful to evaluate these athletes. What it is clear here is that, due to the importance of COD performance in handball, coaches and technical staff should gradually include specific training practices for improving this complex physical quality from the younger categories. Training sessions comprising consecutive accelerations and decelerations, planned and unplanned agility drills, and technique exercises are recommended to properly develop COD performance in young handball players during their specialization years.In conclusion, in youth handball players, jump  and sprint  performance was superior in U15 than U13 players; nonetheless, when it comes to COD performance, there were no significant differences between players. In contrast, U15 players presented a significantly higher COD deficit than the U13 players. These findings have important practical applications for coaches and sport scientists when training or testing young handball players. In general, it appears that, during the transition from pre- to post-puberty, young handball players should focus on transferring their progressive increases in strength, speed, and power capacities to COD performance. As such, more mixed training strategies  ,8 may beS1 Data(XLS)Click here for additional data file.