Intravenous immunoglobulin: exploiting the potential of natural antibodies.

Antibodies present in healthy conditions in the absence of deliberate immunization or infections are called natural antibodies. A significant proportion of natural antibody pool is believed to interact with self-antigens, and thus is called natural autoantibodies. Natural autoantibodies belong to IgG, IgM and IgA subclasses, and are encoded by V(D)J genes in germline configuration and bind to self molecules with varying affinities. In addition to serving in first line defense mechanism, natural antibodies participate in the homeostasis of the immune system. Intravenous immunoglobulin (IVIg) is a therapeutic preparation that contains substantial amount of natural antibodies exclusively of IgG subclass. In addition to its role in protection against pathogens in primary and secondary immunodeficiency patients, IVIg exerts a number of immunoregulatory functions through its interaction with innate and adaptive immune system and thereby imposing immune homeostasis.