<unk> s are mechanically active cells and migrate from blood to an inflammatory site to perform their functions.<unk> s and their macrophage and dendritic cell progeny serve three main functions in the immune system. These are phagocytosis, antigen presentation, and cytokine production. Phagocytosis is the process of uptake of microbes and particles followed by digestion and destruction of this material.<unk> s can perform phagocytosis using intermediary (opsonising) proteins such as antibodies or complement that coat the pathogen, as well as by binding to the microbe directly via pattern-recognition receptors that recognize pathogens.<unk> s are also capable of killing infected host cells via antibody-dependent cell-mediated cytotoxicity. Vacuolization may be present in a cell that has recently phagocytized foreign matter. Many factors produced by other cells can regulate the chemotaxis and other functions of<unk> s. These factors include<unk> st particularly chemokines such as<unk>  chemotactic protein-1 (CCL2) and<unk>  chemotactic protein-3 (CCL7); certain arachidonic acid metabolites such as Leukotriene B4 and members of the 5-Hydroxyicosatetraenoic acid and 5-oxo-eicosatetraenoic acid family of OXE1 receptor agonists (e.g., 5-HETE and 5-oxo-ETE); and N-Formylmethionine leucyl-phenylalanine and other N-formylated oligopeptides which are made by bacteria and activate the formyl peptide receptor 1. Microbial fragments that remain after such digestion can serve as antigens. The fragments can be incorporated into MHC<unk> lecules and then trafficked to the cell surface of<unk> s (and macrophages and dendritic cells). This process is called antigen presentation and it leads to activation of T lymphocytes, which then<unk> unt a specific immune response against the antigen. Other microbial products can directly activate<unk> s and this leads to production of pro-inflammatory and, with some delay, of anti-inflammatory cytokines. Typical cytokines produced by<unk> s are TNF, IL-1, and IL-12.<unk> c cells may contribute to the severity and disease progression in Covid-19 patients.
Monocyte
Basophil
Prolymphocyte
Podocyte
Thymocyte
Agranulocyte
Plasma cell
Lymphoblast