Cluster of Differentiation Antigen 1c/Blood Dendritic Cell Antigen 1 (CD1c/BDCA-1) is a transmembrane glycoprotein in the CD1 family of MHC-like molecules. It is expressed by humans but not by mice or rats. Human CD1c/BDCA-1 is a 316 amino acid protein with a predicted molecular weight of 43 kDa. It binds to lipid and glycolipid antigens and presents them to T cells. CD1c/BDCA-1 is expressed by dendritic cells and B cells, where it traffics between endosomes and the plasma membrane. Heterodimerization with beta-2-Microglobulin is required for CD1c membrane trafficking. CD1c is thought to present a wide variety of lipids to T cells and has been shown to mediate T cell activation in response to Mycobacterium tuberculosis.