IgG Fc region receptors are members of the Ig superfamily that play roles in activating or inhibiting immune responses such as degranulation, phagocytosis, ADCC, cytokine release, and B-cell proliferation.There are three genes for human Fc γ RII /CD32 (A, B, and C) and one for mouse Fc γ RII B (CD32B). CD32 is a low affinity receptor for IgG. CD32B is expressed on B cells and myeloid dendritic cells. Ligation of CD32B on B cells downregulates antibody production and may, in some circumstances, promote apoptosis.