CD32 (also designated Fc gamma RII) is a low affinity receptor for the Fc fragment of aggregated IgG. CD32 is responsible for the clearance of immunocomplexes by macrophages and also plays an important role in the regulation of antibody production by B cells. IgG can noncooperatively bind either one or two highly glycosylated CD32 molecules, and this binding delivers a negative signal for B cells . CD32 exists as several isoforms that are produced by alternative splicing of three distinct genes, A, B, and C . These isoforms are designated FcgRIIA, FcgRIIB1, FcgRIIB3, and FcgRIIC . All isoforms are present on monocytes, placental trophoblasts and endothelial cells . In addition, the FcgRIIB forms are present on B lymphocytes, and the FcgRIIA and FcgRIIC forms are found on neutrophils.