PDCD1 and neoplasm: However, the increase in the CD8+:Foxp3+ ratio in the tumor of PD-1Ab, PD-1KO, and PD-cKO mice suggests that the proposed enhanced immunosuppressive capacity by Foxp3+Tregs in the absence of PD-1 signaling could be counteracted by the adequate expansion of functional effector CD8 T cells leading to tumor growth inhibition.