The disease-specific arm of the therapeutic effect of intravenous immunoglobulin in autoimmune diseases: experimental autoimmune myasthenia gravis as a model.

BACKGROUND [corrected] Intravenous immunoglobulin administration has been beneficially used for the treatment of a variety of autoimmune diseases including myasthenia gravis, although its mode of action and active components have not yet been fully identified. OBJECTIVES To isolate from IVIg a disease-specific fraction involved in the therapeutic activity in myasthenia and to identify its properties and function. RESULTS IVIg administration in experimental autoimmune MG results in suppression of disease that is accompanied by decreased Th1 cell and B cell proliferation. Chromatography of IVIg on columns of IgG from rats with EAMG or from MG patients resulted in depletion of the suppressive activity that IVIg has on rat EAMG. Moreover, the minute amounts of IgG fractions eluted from the EAMG or MG-specific columns retained the immunosuppressive activity of IVIg. CONCLUSIONS Our study supports the notion that the therapeutic effect of IVIg is mediated by a minor disease-specific immunoglobulin fraction that is present in IVIg and is essential for its therapeutic activity.