FCGR2A and neoplasm: Phagocytosis of mAb-opsonized target cells by FcγR-expressing myeloid cells is a well-established mechanism of action for tumor-targeting mAbs.8 Importantly, mAbs targeting T-cell receptors such as CD2534 or 4-1BB28 have also been shown to cause depletion of T-cell populations expressing high levels of target receptor.