Lewis antigen (specifically, Lewis a, Lewis c, and Lewis x antigens) (Le^a^, Le^c^, Le^x^)

Lewis a/c/x antigens are fucosylated carbohydrate structures found on glycolipids and glycoproteins at the surface of many human cells. They are part of the Lewis blood group system, which is determined by the action of fucosyltransferase enzymes encoded by FUT3 ("Lewis gene") and FUT2 ("Secretor gene"). The most clinically relevant forms are Lewis a (Le^a^) and Lewis x (Le^x^), with sialylated derivatives such as sialyl-Lewis x playing key roles in cell adhesion processes. These antigens serve important biological functions including mediating leukocyte trafficking through interaction with selectins during inflammation, acting as markers during embryogenesis (SSEA‑1/Le^x^), facilitating neuronal development, and serving as biomarkers in oncology—where their overexpression is linked to tumor progression. In transfusion medicine they define histo-blood groups alongside ABO/H systems. While not classical "receptors" or "enzymes," they are considered valid therapeutic targets because interfering with their function can disrupt pathological cell-cell interactions involved in cancer metastasis or inflammatory diseases. No approved drugs currently target them directly but research into anti-glycan antibodies or selectin antagonists continues. The term "Lewis c" is less commonly used than "a" or "x," but all refer broadly to structurally related fucosylated oligosaccharide epitopes within this family.

Other names

Lewis a antigen (Le^a^)Lewis c antigen (Le^c^)Lewis x antigen (Le^x^)CD15 (for Le^x^)SSEA-1 (Stage-specific embryonic antigen 1; for Le^x^)Blood group antigensFucosylated oligosaccharides

Therapeutic strategies under investigation include inhibition of cell adhesion by blocking selectin–Lewis interactions to prevent tumor metastasis or inflammation.