* Epitope – the distinct surface features of an<unk> , its<unk> ic determinant.Antigenic molecules, normally "large" biological polymers, usually present surface features that can act as points of interaction for specific antibodies. Any such feature constitutes an epitope. Most<unk> s have the potential to be bound by multiple antibodies, each of which is specific to one of the<unk> 's epitopes. Using the "lock and key" metaphor, the<unk>  can be seen as a string of keys (epitopes) each of which matches a different lock (antibody). Different antibody idiotypes, each have distinctly formed complementarity-determining regions. * Allergen – A substance capable of causing an allergic reaction. The (detrimental) reaction may result after exposure via ingestion, inhalation, injection, or contact with skin. * Superantigen – A class of<unk> s that cause non-specific activation of T-cells, resulting in polyclonal T-cell activation and massive cytokine release. * Tolerogen – A substance that invokes a specific immune non-responsiveness due to its molecular form. If its molecular form is changed, a tolerogen can become an immunogen. * Immunoglobulin-binding protein – Proteins such as protein A, protein G, and protein L that are capable of binding to antibodies at positions outside of the<unk> -binding site. While<unk> s are the "target" of antibodies, immunoglobulin-binding proteins "attack" antibodies. * T-dependent<unk>  –<unk> s that require the assistance of T cells to induce the formation of specific antibodies. * T-independent<unk>  –<unk> s that stimulate B cells directly. * Immunodominant<unk> s –<unk> s that dominate (over all others from a pathogen) in their ability to produce an immune response. T cell responses typically are directed<unk> ainst a relatively few immunodominant epitopes, although in some cases (e.g., infection with the malaria pathogen Plasmodium spp.) it is dispersed over a relatively large number of parasite<unk> s.<unk> -presenting cells present<unk> s in the form of peptides on histocompatibility molecules. The T cells selectively recognize the<unk> s; depending on the<unk>  and the type of the histocompatibility molecule, different types of T cells will be activated. For T-cell receptor (TCR) recognition, the peptide must be processed into small fragments inside the cell and presented by a major histocompatibility complex (MHC). The<unk>  cannot elicit the immune response without the help of an immunologic adjuvant. Similarly, the adjuvant component of vaccines plays an essential role in the activation of the innate immune system. An immunogen is an<unk>  substance (or adduct) that is able to trigger a humoral (innate) or cell-mediated immune response. It first initiates an innate immune response, which then causes the activation of the adaptive immune response. An<unk>  binds the highly variable immunoreceptor products (B-cell receptor or T-cell receptor) once these have been generated. Immunogens are those<unk> s, termed immunogenic, capable of inducing an immune response. At the molecular level, an<unk>  can be characterized by its ability to bind to an antibody's paratopes. Different antibodies have the potential to discriminate among specific epitopes present on the<unk>  surface. A hapten is a small molecule that can only induce an immune response when attached to a larger carrier molecule, such as a protein.<unk> s can be proteins, polysaccharides, lipids, nucleic acids or other biomolecules. This includes parts (coats, capsules, cell walls, flagella, fimbriae, and toxins) of<unk> cteria, viruses, and other microorganisms. Non-microbial non-self<unk> s can include pollen, egg white, and proteins from transplanted tissues and organs or on the surface of transfused blood cells.
Antigen
Immunogen
Antibody
Specifier 
Allergen
Immunotoxin
Microantibody
Heterophile antibody