Low-affinity Fcγ receptors, autoimmunity and infection

Low-affinity Fc gamma receptors (Fc gamma Rs) mediate the effects of immunoglobulin G (IgG) antibodies on leukocytes, including recruitment to inflammatory lesions, phagocytosis, antibody-dependent cellular cytotoxicity, release of inflammatory mediators and regulation of B cell activation. These functions are an important part of the mammalian response to infection, but if deployed inappropriately can cause autoimmune disease. Although most Fc gamma Rs are activatory, there is also an inhibitory Fc gamma R that, when bound to IgG immune complexes, is able to downregulate the effects of both the activatory Fc gamma Rs and the B cell receptor. This review discusses the role of the low-affinity Fc gamma Rs in a balanced immune response and how perturbations in Fc gamma R function result in susceptibility to infection or autoimmunity.