Figure 1.

Mechanisms of action of therapeutic CD20 mAbs. CD20 mAbs can induce tumor killing in several ways. A. Direct binding of CD20 mAbs initiate the crosslinking of multiple CD20 molecules, resulting in cell-death via induction of non-classical apoptosis; B. Activation of complement result in complement-dependent cytotoxicity; C. recognition of opsonized tumor cells by FcγRs expressed on immune effector cells initiate antibody dependent cell-mediated cytotoxicity; D. FcγR may only serve as crosslinking platform and thereby enhance antigen signaling in the tumor cells; E. Ab-initiated complement activation yields to deposition of complement cleavage fragments, which may enhance tumor killing through recognition by complement receptors (CRs) in a process called complement-enhanced ADCC.