Immunological antigen (Ag)

Immunological antigens are diverse molecules, primarily proteins or polysaccharides, that are recognized by the adaptive immune system to elicit a specific immune response (NIH National Cancer Institute). They function as the primary recognition elements for antibodies and T-cell receptors, facilitating the identification of foreign pathogens such as viruses and bacteria, as well as abnormal host cells like those found in cancer (StatPearls, 2023). In clinical practice, antigens are the foundational components of vaccines, which introduce specific epitopes to prime the immune system for future encounters with pathogens (Nature Reviews Drug Discovery, 2020). Furthermore, specific antigens serve as the targets for monoclonal antibody therapies and chimeric antigen receptor (CAR) T-cell therapies, which are engineered to bind to surface-expressed markers on diseased cells. However, the broad nature of antigens also encompasses allergens and autoantigens, which can trigger harmful hypersensitivity or autoimmune reactions (Janeway's Immunobiology, 2016). Consequently, while they are essential for protective immunity, their therapeutic manipulation requires precise targeting to avoid off-target effects and systemic toxicity.

Other names

AntigenImmunogenAllergenNeoantigenAutoantigenEpitope

Antigens act as the molecular triggers for the adaptive immune system; they are recognized by B-cell receptors (BCRs) or processed into peptides and presented by Major Histocompatibility Complex (MHC) molecules to T-cell receptors (TCRs), leading to lymphocyte activation and clonal expansion (Janeway's Immunobiology, 2016; StatPearls, 2023).