FcgR4 (Low affinity immunoglobulin gamma Fc region receptor IV) is also known as CD16-2, FcgammaRIV, receptor for the Fc region of immunoglobulin gamma. Also acts as a receptor for the Fc region of immunoglobulin epsilon. Binds with intermediate affinity to both IgG2a and IgG2b. Does not display binding to IgG1 or IgG3. Plays a role in promoting bone resorption by enhancing osteoclast differentiation following binding to IgG2a. Binds with low affinity to both the a and b allotypes of IgE. Has also been shown to bind to IgE allotype a only but not to allotype b. Binding to IgE promotes macrophage-mediated phagocytosis, antigen presentation to T cells, production of proinflammatory cytokines and the late phase of cutaneous allergic reactions.
