CD80 and neoplasm: It can be induced on the cell surface, binds to CD80 (B7-1) and CD86 (B7-2) on the surface of antigen presenting cells (APCs), and has a higher affinity than the costimulatory molecule CD28 of T cells, thereby inhibiting cytotoxic T-cell activity and enhancing regulatory T-cell (Treg) immunosuppressive activity, causing the immune evasion of tumor cells (17, 18).