IgG subclasses of human autoantibodies.

IgG comprises of four subclasses which differ from each other with respect to their biological properties. Fc gamma receptor shedding as well as a variety of T cell cytokines are influential in the distribution of these subclasses, but the route the antigen is introduced into the body is also important. With regard to nonorgan-specific autoimmune conditions, such as rheumatoid arthritis and systemic lupus erythematosus, IgG1 and IgG3 autoantibodies predominate, whereas IgG4 antibodies are regularly encountered in organ-specific autoimmune diseases. This suggests that the target organ may be continuously stimulating the immune system.