By binding to PD-1 and blocking the binding of PD-1 to PD ligand1 (PD-L1) and PD-L2, it relieves the immunosuppressive effect of PD-1, activates the function of T cells, enhances the immune surveillance and killing ability of T cells against tumors, and generates tumor immune response. The gene discussed is PDCD1; the disease is neoplasm.