CD274, also known as B7-H1 or PD-L1, is a 43kD glycoprotein of the B7 family of the immunoglobulin superfamily. CD274 is expressed on the B and T lymphocytes, natural killer cells, and dendritic cells. The receptor for the B7-H1 molecule is PD-1, which contains an Immunoreceptor Tyrosine-based Inhibitory Motif (ITIM), and is expressed on activated B and T cells. The interaction between CD274 and PD-1 seems to downregulate the T and B immune responses.