Glycosylation and Fc receptors.

Immunoglobulins and Fc receptors are critical glycoprotein components of the immune system. Fc receptors bind the Fc (effector) region of antibody molecules and communicate information within the innate and adaptive immune systems. Glycosylation of antibodies, particularly in the Fc region of IgG, has been extensively studied in health and disease. The N-glycans in the identical heavy chains have been shown to be critical for maintaining structural integrity, communication with the Fc receptor and the downstream immunological response. Less is known about glycosylation of the Fc receptor in either healthy or disease states, however, recent studies have implicated an active role for receptor associated oligosaccharides in the antibody-receptor interaction. Research into Fc receptor glycosylation is increasing rapidly, where Fc receptors are routinely used to analyze the binding of therapeutic monoclonal antibodies and where glycosylation of receptors expressed by cells of the immune system could potentially be used to mediate and control the differential binding of immunoglobulins. Here we discuss the glycosylation of immunoglobulin antibodies (IgA, IgE, IgG) and the Fc receptors (FcαR, FcεR, FcγR, FcRn) that bind them, the function of carbohydrates in the immune response and recent advances in our understanding of these critical glycoproteins.