CD1d

null CD1d is the single group 2 member of the CD1 family and the presenting molecule for invariant natural killer T (iNKT) cells. It binds lipid antigens in a deep hydrophobic groove and displays them to the semi-invariant TCR of iNKT cells; the marine sponge glycosphingolipid alpha-galactosylceramide is the prototypical agonist. Endogenous ligands include lysophospholipids and beta-glucosylceramide, while microbial ligands derive from Sphingomonas bacteria and mycobacteria. CD1d is broadly expressed on hematopoietic cells, including B cells, monocytes, and dendritic cells, and is inducible on epithelia. Through iNKT cell activation CD1d shapes Th1/Th2 balance, antitumor immunity, and autoimmunity, and CD1d-deficient mice lose iNKT cells entirely.