The Lewis antigen system is a human blood group system and includes Lewis a, Lewis b Lewis c, their sialyl forms, and Lewis x, Lewis y and their sialyl forms. Lewis a Lewis b antigens are not expressed on cord red blood cells - RBCs (e.g. Cord blood is blood that remains in the placenta and in the attached umbilical cord after childbirth). Lewis antigen levels on RBCs are often diminished during pregnancy, possibly due to pregnancy-associated changes in plasma lipoproteins. Lewis antigens are also found on lymphocytes and platelets; on other tissues, including pancreas, stomach, intestine, skeletal muscle, renal cortex, and adrenal glands; and in soluble form in saliva as glycoproteins. Because of structural similarities, the term “Lewis antigen” was applied to other glycan sequences and includes the Lewis x and Lewis y determinants and sialylated forms e.g. sialyl Lewis x and sialyl Lewis y. Some Lewis blood group antigens have important functions in leukocyte trafficking and tumor-cell metastasis. Lewis x, lewis y and their sialyl forms are potential antigens for cancer immunotherapy.

This 3D model was generated using SGI (Silicon Graphics) Octane IRIX workstation in 2002.