Programmed cell death ligand 1(CD274, or B7-H1, PD-L1), is the first member of B7 family to be discovered. B7 family molecules are type I transmembrane proteins belonging to the immunoglobulin superfamily. In concert with their CD28 family receptors, the B7s are key regulators of the adaptive immune response. CD274 is suggested a negative regulator of T and B cell, and play important role in mediating tolerance of lymphocytes to self-antigens.
