Lewis antigen (Le)

Lewis antigens are a family of carbohydrate (glycan) blood group antigens formed by fucosylation of type I (Le^a^, Le^b^) and type II (Le^x^, Le^y^) oligosaccharide precursors by specific fucosyltransferase enzymes (primarily encoded by FUT3 and FUT2 genes). These antigens are not synthesized on red blood cells directly but are secreted by epithelial tissues (notably gastrointestinal tract) and adsorbed onto the erythrocyte membrane from plasma. Besides their role in distinguishing blood groups, Lewis antigens serve as ligands for selectins, mediating cell–cell adhesion, especially in immune cell trafficking and tumor cell metastasis. Sialylated variants (sLe^a^, sLe^x^) are crucial in cancer biology and are widely used as clinical biomarkers (e.g., CA 19-9 in pancreatic cancer). Overexpression of Lewis antigens is linked to a range of pathological processes, including cancer progression and reproductive dysfunction, while their function in normal physiology includes mediating embryo implantation and immune regulation.

Other names

Lewis blood group antigenLewis a antigen (Le^a^)Lewis x antigen (Le^x^)Sialyl-Lewis a (sLe^a^)Sialyl-Lewis x (sLe^x^)CD15 (for Lewis x)Le^c^ antigenLe^y^ antigenLewis c antigen

Blocking cell–cell adhesion: Therapeutic antibodies can bind to Lewis antigens and block interaction with selectins, thus inhibiting cancer cell metastasis. Immune modulation: Targeting surface carbohydrates may influence immune cell trafficking or recognition of tumor cells.