CARBOHYDRATES AND ANTIGEN RECOGNITION BY T-CELLS

T Lymphocytes (T cells) recognize short antigenic peptides bound to ei ther MHC I or IT molecules, in contrast to antibodies which can bind t o native antigen, The mechanism by which antigens are processed into p eptides, and the nature of the interactions of antigenic peptides with MHC molecules and with the T cell receptor have now been defined in s ome detail. Of significance to glycobiologists is the recent appreciat ion that the carbohydrate of glycoprotein antigens can contribute to t he T cell recognition of epitopes presented by MHC molecules, Experime nts using model T cell epitopes have demonstrated that carbohydrate ca n modulate T cell responses in a variety of ways; for example, there a re a number of cases where glycopeptide-specific T cell responses have been identified, Many of these glycopeptide-specific T cell responses involve a peptide bearing a single glycosyl residue, thus it appears very likely that both glycan and peptide make contact with the T cell receptor binding site, Significantly, glycopeptide-specific T cell res ponses have also been detected to native glycoproteins, The ability of carbohydrate to influence T cell recognition of antigen has important consequences for a wide range of immune responses as well as the curr ent strategies for mapping T cell determinants.