Epitopeja

An epitope, or antigenic determinant, is the specific part of an antigen that is recognized by the immune system. Epitopes are the targets of antibodies produced by B cells as well as of T-cell receptors on T cells when peptides are presented by MHC molecules. The concept of epitopes is central to understanding how the immune system identifies and responds to diverse antigens, including pathogens and allergens.

Epitopes can be classified by the type of immune receptor they engage. B-cell epitopes can be linear, consisting of a continuous stretch of amino acids, or conformational (discontinuous), formed by amino acids that are brought together in the three-dimensional folding of the antigen. T-cell epitopes are short peptides derived from processed antigens and presented on MHC molecules; they are recognized by T-cell receptors on CD4+ and CD8+ T cells. In general, MHC class I presents about 8–11 amino acids to CD8+ T cells, while MHC class II presents 12–25 amino acids to CD4+ T cells.

Epitope identification, or epitope mapping, aims to determine which regions are targeted by immune responses. Experimental approaches include peptide libraries, phage display, and structure-based methods, while computational predictions estimate likely epitopes based on sequence, structure, and MHC-binding motifs. Epitope knowledge underpins the design of epitope-based vaccines and diagnostic assays but faces challenges such as conformational dependence, antigen variability, and potential cross-reactivity or immune escape.

Overall, epitopes define the specificity of immune recognition and play a key role in immunology, vaccinology, and clinical diagnostics, guiding both fundamental research and applied strategies.