Antigeny

Antigeny is a term occasionally used in immunology to describe the property of a molecule to be recognized as an antigen by the adaptive immune system. In most modern texts, the same concept is more commonly referred to as antigenicity, and to a related extent immunogenicity.

Antigenicity refers specifically to the ability of a substance to be recognized by antibodies or T‑cell receptors. It is determined by the presence of epitopes — specific molecular determinants on the antigen that bind with high affinity to antibody paratopes or TCR/MHC complexes. Both linear epitopes (continuous amino acids) and conformational epitopes (discontinuous residues brought together in the folded protein) contribute to antigenicity. Other factors include cross‑reactivity, haptenation (small molecules that are not antigenic by themselves becoming antigenic when bound to a carrier), and the density of epitopes presented to the immune system.

Immunogenicity is related but distinct: it is the ability of a substance to elicit a detectable immune response, which requires antigen presentation, costimulatory signals, and usually adjuvants or inflammatory context. A substance can be antigenic but not strongly immunogenic, especially if it is self or phylogenetically conserved.

Measurement typically involves serological assays to detect binding to antibodies (for example ELISA) or T-cell assays to assess recognition of epitopes, as well as functional tests like neutralization or protection in models.

Usage notes: antigeny is uncommon in contemporary literature, with antigenicity and immunogenicity preferred. When encountered, it is usually used as a synonym or historic term rather than a distinct scientific category.