Low affinity immunoglobulin gamma Fc region receptor III (Fc gamma RIII/CD16) is a member of the Ig superfamily. Based on close relationships in their extracellular domains, the Fc gamma Rs have been divided into three classes composing of Fc gamma RI (CD64), Fc gamma RII (CD32), and Fc gamma RIII (CD16). Each group may be encoded by multiple genes and exist in different isoforms depending on species and cell type. Mouse CD16 is a type I transmembrane protein having two extracellular Ig-like domains consisting of immunoglobulin domain, repeat, signa and transmembrane, transmembrane helix. It is expressed on a variety of myeloid and lymphoid cells and associates with Fc R gamma to deliver an activating signal upon ligand binding. Fcgr3 is IgG binding and activation or inhibition of immune responses such as antibody-dependent cellular cytotoxicity, phagocytosis, cell surface receptor signaling pathway and positive regulation of type I/IIa/III hypersensitivity.