CTLA4 and neoplasm: Currently, the best accepted hypothesis is that anti-CTLA-4 antibodies mediate at least some of their immune boosting effects by engaging with activating Fc gamma receptors (FcγR) by binding to CTLA-4 on Treg to induce macrophage mediated depletion of the Treg through antibody-dependent cell-mediated cytotoxicity (ADCC) within the tumor environment or at the infusion site (63).