Peptidantigene

Peptidantigene is a term used in immunology to describe peptide antigens, which are short amino acid sequences that can elicit an immune response when presented to immune receptors. In this sense, peptidantigene refers to the peptide component of an antigenic determinant that is recognized by T cells or B cells, often in the context of major histocompatibility complex (MHC) presentation.

Biological characteristics typically include small size and sequence specificity. For MHC class I presentation, peptide fragments are usually about 8 to 11 amino acids long and originate from intracellular proteins. They are transported into the endoplasmic reticulum by TAP and loaded onto MHC I molecules for surface display. For MHC class II, longer peptides, generally 12 to 25 amino acids, are generated in endosomal/lysosomal compartments and loaded onto MHC II for presentation to CD4+ T cells. Some peptidantigen epitopes can be linear, while others may require processing to be properly presented.

Processing and presentation are central to recognition by immune receptors. T cells recognize peptidantigen-MHC complexes via T-cell receptors, providing specificity for the peptide sequence and the presenting MHC allele. B cells may recognize peptidantigen epitopes directly or as part of a conformational structure, contributing to antibody responses. Peptidantigen research also intersects with epitope mapping and vaccine design, where selected peptide sequences aim to provoke protective immunity.

Applications of peptidantigen concepts include peptide vaccines, diagnostic assays, and immunological studies. Limitations involve HLA restriction, peptide stability, and potential for tolerance or autoimmunity, requiring careful selection and validation of peptide epitopes. See also: epitope, peptide vaccine, antigen presentation.