- The Fc Receptors are membrane proteins which bind to the Fc Region of Antibody. Fc Receptors are primarily expressed on phagocytic cells such as Macrophages, Neutrophils, and Dendritic Cells as well as the anti-parasitic leukocytes Basophils, Eosinophils, and Mast Cells. These receptors allow phagocytes to recognize antibody-coated (opsonized) microbes and induce the cells to phagocytose the microbe and degrade the organisms. Consequently, Fc Receptors are key molecules which connect microbial antibody binding to microbial death and destruction.
- A variety of Fc Receptor subtypes exist which display specificity for different isotypes of antibody. In most cases, Fc Receptors only bind antibody which is cross-linked with its antigen, guaranteeing that activation of phagocytes only occurs when the antibody is actually bound to a microbe. The primary exception to this is the Fc Receptor for IgE which can bind its antibody in the absence of antigen. The IgE Receptor is only expressed on anti-parasitic leukocytes such as Mast Cells, Basophils, and Eosinophils and plays a key role in the molecular pathogenesis of allergic responses (See: Type I Hypersensitivity).