Antibodies which block anti-myelin basic protein antibodies associated with development of experimental autoimmune encephalomyelitis in Wistar rats

Objective: In sera from normal rats and from rats injected with whole myelin in complete Freund adjuvant to induce EAE we study the presence of antibodies capable to inhibit the reactivity of autoantibodies directed to myelin basic protein (MBP). Methods: Sera from rats that developed or not clinical signs of EAE were obtained previously to immunization, at acute stage of the disease and when the animals were completely recuperated, and chromatographied on a protein G-Sepharose column to obtain the retained (IgG) fractions. Then these fractions were depleted of anti-MBP reactivity by affinity chromatography and the ability of these depleted sera to block the reactivity of anti-MBP IgG antibodies was analyzed by an immunoblot technique. Results: IgG fractions from preimmune sera inhibited the anti-MBP IgG reactivity associated to EAE. The analysis of sick EAE animals showed that the inhibitory activity faded away with the onset of the clinical signs but returned at its maximum value during the spontaneous remission. Animals that never developed clinical EAE did not show changes in the level of inhibitory activity that was similar to that observed in the preimmune sera. Conclusions: The presence of IgG antibodies blocking the anti-MBP IgG reactivity correlates with the development of the clinical signs of EAE.