Schematic representation of mechanisms underlying the impact of FcγRIIb upon activation and internalization of BCRs. Internalization of type I CD20 mAbs correlates with levels of expression. major histocompatibility complex class II (MHCII) monoclonal antibodies (mAbs) or type II CD20 mAb binding in cis results in limited internalization, despite robust phosphorylation of FcγRIIb (P). In contrast, type I CD20 mAbs promote internalization/degradation. CD20 mAb binding to FcγRIIb in trans competes for binding in cis but does not affect internalization.