PDCD1 and neoplasm: Programmed death ligand 1 (PD-L1 and CD274) is an immunosuppressive protein that, binding directly to its receptor PD-1 on tumor-infiltrating lymphocytes, attenuates T cell activation, induces the apoptosis of activated T cells, as well as induces T-cell anergy and exhaustion [5,6], allowing tumors to evade immune attacks.