Fc receptors in mucosal immunology

Immunoglobulin A (IgA) is the most prevalent antibody class at mucosal surfaces. In addition to protecting mucosal surfaces by preventing invasion of pathogens, IgA can interact with multiple IgA receptors by binding to the Fc tail, carbohydrate side chains, or accessory molecules. The best characterized IgA Fc receptor is FcαRI (CD89), which acts as a regulator between anti- and proinflammatory responses of IgA. Furthermore, the Fcα/μR, polymeric Ig receptor, transferring receptor, and asialoglycoprotein receptor have been described, as well as IgA receptors on M cells, T cells, natural killer cells, and dendritic cells. However, the significance of several of these receptors is still unclear. The neonatal Fc receptor for IgG, furthermore, plays a role in transporting IgG across epithelial cells, whereas Fc receptors for IgE are involved in parasitic infections, allergies, and asthma. The focus of this chapter is therefore the role of Fc receptors in mucosal immunology.