epitóp

An epitope, or antigenic determinant, is the specific portion of an antigen that is recognized by the immune system. Epitopes are the sites to which antibodies bind or that are presented by MHC molecules to T cells. A single antigen can display multiple epitopes.

There are B-cell epitopes and T-cell epitopes. B-cell epitopes are recognized by antibodies and B-cell receptors; they can be linear, consisting of a short consecutive amino acid sequence, or conformational (discontinuous), formed by amino acids brought together in the folded protein. T-cell epitopes are short peptides presented on MHC class I or II molecules and recognized by T-cell receptors; their length and processing differ between MHC classes and depend on antigen processing by antigen-presenting cells.

Epitopes are central to vaccine design and serology. Immunodominant epitopes elicit the strongest responses, while subdominant epitopes can influence the breadth and cross-reactivity of the immune response. Hapten-carrier effects illustrate how small molecules become antigenic when linked to a larger carrier. Epitopes can also be cross-reactive, potentially causing diagnostic cross-reactivity or, in some cases, autoimmune phenomena.

Identification and mapping of epitopes employ experimental and computational approaches. Experimental methods include peptide libraries, phage display, and structural studies of antigen–antibody complexes, while computational predictions use sequence and structural features to forecast likely epitopes. Knowledge of epitopes supports the development of vaccines, diagnostic assays, and targeted immunotherapies.