programmed cell death 1 (pd-1, cd279, blue sheets) immune checkpoint protein bound to programmed death-ligand 1 (pd-l1, green

programmed cell death pd1 surface receptor immune white blood system apoptosis inhibitor tumor cancer pdl1 ligand nivolumab antibody melanoma metastatic pembrolizumab cd274 listeria pdb3bik immunotherapy cd279 pdcd1 checkpoint structure peptide protein amino acid molecule polypeptide polymer atoms science scientific disease health molecular model 3d rendering illustration