A disease-specific fraction isolated from IVIG is essential for the immunosuppressive effect of IVIG in experimental autoimmune myasthenia gravis.

Intravenous immunoglobulin (IVIG) treatment is beneficially used in autoimmune disorders including myasthenia gravis (MG) although its mode of action and active components are still not fully identified. In an attempt to isolate from IVIG a disease-specific suppressive fraction, IVIG was passed on columns of IgG from rats with experimental autoimmune MG (EAMG) or from MG patients. These chromatographies resulted in depletion of the suppressive activity of IVIG on rat EAMG whereas the minute amounts of IgG fractions eluted from the EAMG- or MG-specific columns retained the immunosuppressive activity of IVIG. These results demonstrate that a minor disease-specific immunoglobulin fraction present in IVIG is essential for its suppressive activity.