IgG

Function

• IgG-mediated binding of pathogens causes their immobilization and binding together via agglutination; IgG coating of pathogen surfaces (known as opsonization) allows their recognition and ingestion by phagocytic immune cells, leading to the elimination of the pathogen itself;
• IgG activates the classical pathway of the complement system, a cascade of immune protein production that results in pathogen elimination;
• IgG also binds and neutralizestoxins;
• IgG also plays an important role in antibody-dependent cell-mediated cytotoxicity (ADCC) and intracellular antibody-mediated proteolysis, in which it binds to TRIM21 (the receptor with greatest affinity to IgG in humans) in order to direct marked virions to the proteasome in the cytosol;
• IgG is also associated with type II and type III hypersensitivity reactions.