Antigenitet

Antigenitet, or antigenicity, is the property of a substance to be recognized by the immune system, particularly by antibodies and T cell receptors. It describes the potential of a molecule to bind specifically to immune receptors, rather than the ability to provoke a full immune response. Immunogenicity is the related concept that refers to the ability to elicit an adaptive immune response; an antigen may be highly antigenic without being highly immunogenic unless it is presented in an appropriate context.

Determinants of antigenicity include the presence of epitopes—specific molecular features recognized by immune receptors. B-cell epitopes are typically accessible on the native structure and bound by antibodies, while T-cell epitopes are peptides presented by MHC molecules. Epitopes can be linear or conformational. Size, complexity, chemical composition, and three-dimensional structure influence antigenicity, as do the molecule’s stability and its ability to reach immune surveillance in the organism. Haptens are small molecules that are antigenic but immunogenic only when conjugated to a larger carrier protein.

Measurement and implications: antigenicity is often assessed by binding assays, such as ELISA or immunoblotting, and by evaluating cross-reactivity with related antigens. In clinical contexts, antigenicity underpins diagnostics (antigen tests), allergen characterization, and the identification of tumor-associated or autoantigens.

Applications and caution: vaccine design and immunodiagnostics target specific antigenic determinants to guide immune recognition. Safety considerations include avoiding autoantigen cross-reactivity and managing hypersensitivity to allergens.