The following pathways may contribute to PD-1 blockade therapeutic resistance: the absence of antigenic proteins, impaired antigen presentation, lack of T cells with tumor antigen-specific T-cell receptors, insensitivity to T cells (mutations in the interferon gamma pathway), overexpression of other inhibitory immune checkpoints and immunosuppressive cell recruitment (17, 36–38). The gene discussed is PDCD1; the disease is neoplasm.