CD1c, also known as R7 or M241, is a 43 kD member of the five CD1 antigens (CD1a-e) in human. The CD1 molecules are type I glycoprotein with structural similarities to MHC class I and a non-covalent associated with beta2-microglobulin, belonging to Ig superfamily. CD1c is expressed on cortical thymocytes, Langerhans cells, dendritic cells, and a subset of B cells. It has been reported that CD1c is also expressed on mature T cells with tightly regulated manner. The function of CD1c is involved in antigen-presentation of glycolipids. It may also act in T cells as an immune regulatory molecule.