CD80 and cancer: The B7 family ligands include B7-1 (1), B7-2 (2), PD-L1 (B7-H1) (3, 4), PD-L2 (B7-DC) (5, 6), inducible T cell co-stimulator ligand (ICOSL) (also known as, B7-H2, B7h, B7RP-1, GL50, LICOS) (7–10), B7-H3 (11), B7-H4 (B7x, B7S1) (12–14), B7-H5 (HHLA2) (15, 16), and B7-H6 (17), etc. The importance of these molecules has been highlighted by the FDA approval of several drugs for the treatment of cancer and autoimmune disease by targeting the ligands or their receptors.