Susceptibility to murine experimental autoallergic myasthenia gravis: the role of antibody specificity.

To examine the differing susceptibility of C57BL/6J and C3H/HeJ mice to experimental autoallergic myasthenia gravis (EAMG), we have compared the pathogenicity of sera from the two strains. Mice were immunized with acetylcholine receptor from T. californica and muscle weakness assessed as the time mice were capable of running on an exercise drum following the administration of a sub-lethal dose of D-tubocurarine. 16 of 20 C57BL/6J and only 4 of 19 C3H/HeJ mice developed muscle weakness. However, anti-AChR antibody titres were similar in both strains. The effect of transfer of pooled immune sera from each strain to naive recipients was therefore compared. Transfer of pooled C57BL/6J sera to naive C3H/HeJ and C57BL/6J mice produced significant muscle weakness (P less than 0.001 & P less than 0.001 respectively). Transfer of pooled C3H/HeJ sera did not produce statistically significant muscle weakness in either strain. It is concluded that differences in disease susceptibility result from differences in antibody specificities of the major antibody populations, rather than differences in total antibody amounts or other factors.