Antibody - Fc Receptor Interactions in Antimicrobial Functions

Abstract

Antibody molecules, produced during the adaptive immune response, are involved in protection from all types of pathogens, including viruses, bacteria, fungi, and protozoa. Antibodies bind to their cognate antigen via their two Fab portions, but most of their biological functions are mediated by their Fc portion when they bind to specific Fc receptors (FcR) on the membrane of immune cells. Crosslinking of FcR on the surface of cells activates several effector functions. These effector functions are beneficial because they lead to destruction of pathogens. However, in some cases, antibodies can direct these effector functions against normal tissues and cause autoimmune diseases. In recent years, the interaction of IgG antibody molecules with Fcγ receptors has been analyzed in great detail and new clues on the way particular factors modulate the IgG-FcγR interaction have been elucidated. Some of these factors include the different IgG subclasses, and the glycosylation pattern of the antibody. In this review, we describe the main types of Fcγ receptors (FcγR), and our current view of how different IgG subclasses bind to different FcγR, to promote antimicrobial cell responses. In addition, novel clinical aspects of antibody-FcγR interaction, including non-antibody molecules that can bind FcγR, and glycosylation variants of antibodies that can bind different cell membrane receptors are discussed. Keywords: Antibody, immunoglobulin, immunoreceptor, macrophage, neutrophil, phagocytosis.