Fc gamma RIII/CD16 is a low/intermediate affinity activating receptor for polyvalent immune-complexed IgG. It is involved in phagocytosis, secretion of enzymes and inflammatory mediators, antibody-dependent cytotoxicity, and clearance of immune complexes. It is expressed on NK cells, T cells, monocytes, and macrophages. Mouse Fc gamma RIII/CD16 is encoded by a single gene and is expressed as a type I transmembrane protein on a variety of myeloid and lymphoid cells. It associates with Fc R gamma to deliver an activating signal upon ligand binding.