Receptor for the invariable Fc fragment of immunoglobulin gamma (IgG). Binds with intermediate affinity to both IgG2a and IgG2b. Can bind to IgG2a and IgG2b monomers. Does not display binding to IgG1 or IgG3. Recognizes neutralizing virus-specific IgGs displayed on the cell surface of infected cells and triggers antibody-dependent cellular cytotoxicity (ADCC). Confers protection to lethal influenza virus infection. On splenic dendritic cells, uptakes antigen immune complexes and efficiently divert them into MHC class I and II antigen presentation pathways to provide for superior priming of CD4-positive and CD8-positive T cell immune responses. Mediates neutrophil activation by IgG complexes redundantly with FCGR2A. Plays a role in promoting bone resorption by enhancing osteoclast differentiation following binding to IgG2a. Also acts as a receptor for the Fc region of immunoglobulin epsilon (IgE). 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. Binds aggregated IgE but not the monomeric form and bound monomeric IgG is readily displaced by IgE complexes. Binding to IgE promotes macrophage-mediated phagocytosis, antigen presentation to T cells, production of pro-inflammatory cytokines and the late phase of cutaneous allergic reactions. Mediates enhanced ADCC in response to afucosylated IgGs