CD274 and neoplasm: PD1 is a transmembrane glycoprotein expressed on the surface of immune-cells that binds PDL-1 expressed on the surface of tumor cells; the interaction between PD1 and PD-L1 down regulates the cytotoxic response of T cells.9 ICIs block CTLA-4/B7 receptor and PD-1/PDI-L1 pathways, enhancing T-cell action against tumor cells.