Polyreactive autoantibodies purified from human intravenous immunoglobulins prevent the development of experimental autoimmune diseases.

Intravenous immunoglobulins (IVIg) are therapeutic preparations of normal human polyclonal Ig G (IgG) that exert immunomodulatory effects in patients with autoimmune or systemic inflammatory diseases. Two different IgG subfractions were evaluated for their respective immunomodulatory effects in the treatment of experimental autoimmune diseases: a fraction enriched in antibodies that recognize the F(ab')(2) portion of IVIg and a fraction of natural polyreactive autoantibodies purified on a dinitrophenyl (DNP)-Affiprep immunoadsorbent. A very small fraction of IgG interacting with DNP but not with F(ab')(2) fragments expressed an increased ability to bind to self-antigens. The anti-DNP fraction, but not the anti-idiotype fraction, protected against inflammation observed in collagen-induced arthritis and experimental autoimmune encephalomyelitis in rats. Furthermore, it was able to reduce the occurrence of spontaneous diabetes mellitus in nonobese diabetic mice at lower concentrations than unfractionated IVIg. The therapeutic benefit of the anti-DNP fraction was associated with the inhibition of secretion of proinflammatory cytokines and stimulation of secretion of IL-1 receptor antagonist. Our results provide evidence that polyreactive autoantibodies play a role in the protective effect of IVIg in experimental models of autoimmune diseases in which inflammatory reactions are part of the disease process.