PDCD1 and neoplasm: Fc effector function is required for antitumor efficacy of anti-CTLA4 antibodies in mouse tumor models and antibody-mediated depletion of tumorous, but not peripheral, Tregs has been shown to be a critical factor.14 15 We have shown the requirement for anti-CTLA4 Fc effector function is eliminated if Fc effector-less CTLA4 antagonists are combined with anti-PD-1 in mouse tumor models.