Fc fragment of IgG, low affinity IIb, receptor (CD32) Adenovirus (Ad-CD32)

CD32 (also designated Fc gamma RII) is a 40 kDa 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. CD32 is a cell surface marker that exists as several isoforms, which are produced by alternative splicing. The cytoplasmic portion of FcRIIA and FcRIIC contains an activatory ITAM motif whereas FcRIIB contains an inhibitory ITIM motif. Differential splicing of FcRIIB gene yields two isoforms FcRIIB1and FcRIIB2. All forms are present on monocytes, placental trophoblasts and endothelial cells. Neutrophils express FcRIIA and C. FcRIIB is expressed by B lymphocytes and mast cells. In platelets and megakaryocytes, CD32 is noncovalently associates with a member of the immunoglobin superfamily glycoprotein VI (GPVI), which is a collagen receptor that plays a critical role in collagen-induced platelet aggregation. GPVI exists as 55 kDa protein in megakaryocytes and a 58 kDa protein in platelets.