Experimental autoimmune myasthenia gravis (EAMG) in rats can be produced as the result of immunization with purified acetylcholine receptor (AChR). However, antibodies produced against an irreversibly denatured AChR were not capable of producing detectable AChR-dependent neuromuscular impairment such as that seen following immunization with AChR of intact conformation. This immunopathological difference was observed despite the fact that both immunizations resulted in the production of clonotypically heterogeneous antibodies with similar titers, isotype distribution, and relative binding avidities for conformationally intact AChR. Although they had no apparent disease-causing potential of their own, antibodies produced against denatured AChR could, however, bind AChR at the neuromuscular junction and mediate in vivo AChR-dependent neuromuscular impairment if a second anti-antibody was provided. Finally, immunization against denatured AChR, or administration to naive rats of antibodies obtained by immunization against denatured AChR, resulted in the recipient rats becoming resistant to the usual pathological effects of antibodies produced against intact AChR (either induced by active immunization or following passive antibody transfer). These observations suggest that disease severity in this system may be influenced by relationships between disease-causing and disease-abrogating antibodies.
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