Background：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. It also involved in the costimulatory signal, essential for T-cell proliferation and production of IL10 and IFNG, in an IL2-dependent and a PDCD1-independent manner. PD-L1 is a 290 aa transmembrane protein with a calculated molecular weight of 33 kDa, the apparent molecular weight has been reported as 45-70 kDa, suggesting probable glycosylation(PMID: 18760278; 16493058).?
