Preparation:This antibody was produced from a hybridoma (mouse myeloma fused with spleen cells from a mouse immunized with PD-L1 protein). IgG1 fraction of culture supernatant from the hybridoma was purified by protein G affinity chromatography.

B7-H1 (also known as PD-L1 or CD274) is a B7 family member and it is a ligand for PD-1 (programmed death-1, a member of the CD28 family). PD-L1 is constitutively expressed on a wide variety of immunocytes and nonhematopoietic cell types including some malignant tumors, suggesting the potential mechanism of immune evasion. Emerging data suggest that patients whose tumors overexpress PD-L1 by IHC have improved clinical outcomes with anti-PD-1Cdirected therapy. The use of PD-L1 (B7-H1) immunohistochemistry (IHC) as a predictive biomarker is important for anti-PD-1Cdirected therapy in human cancer.