The FUN-2 monoclonal antibody reacts with human CD32 (also known as Fc gamma RII), a 40 kDa polymorphic transmembrane glycoprotein. CD32 is expressed on B cells, monocytes, granulocytes, macrophages, and platelets and dimly on natural killer cells. CD32 mediates oxidative burst and phagocytosis in granulocytes as well as platelet aggregation. CD32 enables interaction between Fc gamma RII-expressing cells and IgG-containing immune complexes. The CD32 receptor is thought to play a role in inflammation and autoimmune disease.