CD274, also commonly referred to as PDL1, is a ligand that binds with the receptor PD1, commonly found on T-cells, and acts to block T-cell activation. PD1 expression has been observed in a variety of cancers including melanoma and non-small cell lung cancer. The interaction of PD1/PDL1 is hypothesized to be a possible mechanism for the tumor to escape immune response. A number of checkpoint blockade inhibitors including pembrolizumab and nivolumab have been developed that target the PD1/PDL1 interaction in order to allow T-cells to recognize tumor cells without being deactivated by the tumor.

Programmed cell death 1 ligand 1 (PD-L1) (PDCD1 ligand 1)(Programmed death ligand 1) (B7 homolog 1) (B7-H1) (CD antigen CD274)