Glycoepitopes

Glycoepitopes are antigenic determinants formed by carbohydrate structures (glycans) that are recognized by the immune system. They can be detected by antibodies (B cell responses) and, in some cases, by glycan-specific T cell receptors when presented as glycopeptides. Glycoepitopes may arise on glycoproteins, glycolipids, or free polysaccharides and can be linear or conformational, depending on the three-dimensional structure of the glycan and its presentation in a larger molecule.

In infectious disease and transplantation, glycoepitopes include blood group antigens and pathogen-associated glycans such as bacterial capsular polysaccharides and viral envelope glycans. Tumor-associated carbohydrate antigens (TACAs) such as TF antigen (Galβ1-3GalNAc), sialyl-Tn, Globo H, and Lewis antigens are notable examples studied in cancer immunology.

Antibody recognition of glycoepitopes can be influenced by the carrier protein, linkage type, branching, and density of glycans, and peptides in glycopeptides can provide T cell help. Glycoepitope mapping is challenging because glycans are heterogeneous and can mask underlying epitopes; conformational epitopes depend on cis/trans linkages and three-dimensional presentation.

Methods such as glycan arrays, mass spectrometry, and structural studies are used to characterize glycoepitopes and their specificities. Applications include the design of vaccines and diagnostics that target carbohydrate antigens, and the study of immune responses to pathogens, cancer, and transplantation.