Intravenous immunoglobulin in autoimmune and inflammatory diseases: More than mere transfer of antibodies

Initially used for the treatment of immunodeficiencies, intravenous immunoglobulin (IVIg) has increasingly been used as an immunomodulatory agent in immune thrombocytopenic purpura, autoimmune neuropathies, systemic lupus erythematosus, myasthenia gravis, Guillain–Barré syndrome, and Kawasaki disease. Although IVIg benefits have been reported in many autoimmune and systemic inflammatory diseases, its mechanisms of immunomodulation are not fully understood and probably involve Fc-dependent and/or F(ab′)2-dependent mutually non-exclusive effects. These mechanisms of action of IVIg reflect the importance of natural antibodies in the maintenance of immune homeostasis. We discuss here the recent advances in the understanding of immunoregulatory effects of IVIg.