In light of PD-1 blockade for tumor therapy, genetically inactivated PD-1-/- OT-1 CD8+ T-cells showed an augmented capacity to enhance Tc17 differentiation in vitro in a T helper type 17 (Th17)-like cytokine environment and mount immunity to tumor tissue in an IFNγ dependent manner in tumor bearing mice. The gene discussed is PDCD1; the disease is neoplasm.