antigenicitet

Antigenicity is the property of a substance to be recognized by the immune system, specifically its ability to bind to antibodies or T-cell receptors. It is distinct from immunogenicity, which describes the capacity to provoke an immune response. A molecule can be antigenic and yet poorly immunogenic if it binds receptors without eliciting a strong or durable reaction.

Antigenicity arises from specific parts of the molecule called epitopes. B-cell epitopes are typically accessible on the surface and can be linear or conformational, whereas T-cell epitopes must be processed and presented by major histocompatibility complex (MHC) molecules. The strength and specificity of binding to antibodies or TCRs determine the apparent antigenicity of a substance.

Several factors influence antigenicity. Molecular size and complexity, the three‑dimensional arrangement of epitopes, and their accessibility on the molecule affect recognition. Post‑translational modifications such as glycosylation can mask or reveal epitopes. Cross‑reactivity, where similar epitopes are found across different antigens, can broaden or confound antigenic recognition. Immunodominance, epitope density, and the context of exposure also play roles.

Measuring antigenicity involves serological and biophysical assays such as ELISA, Western blot, or surface plasmon resonance to assess binding, as well as functional tests that infer recognition by immune components. Antigenicity is central to vaccine design, diagnostic development, and understanding pathogen evolution, including antigenic drift and shift that can alter epitope profiles over time.