Myasthenia gravis: antibodies to acetylcholine receptor with human and rat antigens

Serum antibodies to acetylcholine receptors (AChR) in myasthenia gravis were surveyed by radioimmunoassay, using 125I-alpha-bungarotoxin-complexed receptors of human muscles and denervated rat muscles. Antibodies were detected more frequently with human AChR than with rat AChR. Furthermore, antibody titers to human AChR were not always parallel to titers observed in the rat receptors, indicating the heterogeneity of antibody specificities in different individuals. Correlation between antibody titers and clinical severity was better when the antibody concentration was determined with human AChR. About 90% of the myasthenic sera contained antibodies to AChR, and 40% also contained other antibodies such as thyroid autoantibodies. These findings suggest that myasthenia gravis is a multiple immunopathy.