PDCD1 and cancer: PD-1 ligand 1 (PD-L1, B7-H1 or CD274) and PDL2 (also B7-DC or CD273) are two ligands for PD-1.481,482 Their interaction may cause the inhibition of T-lymphocyte proliferation and cytokine production to suppress the immune response.483 High level of PD-L1 expression was reported in many types of cancer and myeloid cells in the tumor microenvironment.484–489