Intravenous γ-globulin inhibits binding of anti-GM1 to its taget antigen

In this study, we preincubated the sera ot 3 patients with neuropathies associated with elevated titers of IgM anti-GM, antibodies, with increasing concentrations of intravenous Ig (IVIg) and assayed the inhibitory effect of this mixture on antibody binding to immobilized GM 1 by an enzyme-linked immunosorbent assay. Pharmacologic concentrations of IVIg, ranging from 0.1 μg/ml to 100 mg/ml, inhibited anti-GM, binding to its target antigen from 26 ± 3 to 71 ± 7%, respectively, in a dose-dependent manner. A similar inhibition of binding was also observed with IVIg F(ab') 2 fragments. These findings provide a possible mechanism for the clinical efficacy of IVIg in motor neuropathies.