Antibodies to polyadenylic acid in patients with myasthenia gravis.

Sera from 100 patients with myasthenia gravis and 45 patients with non-myasthenia gravis neuromuscular diseases were studied for antibodies to poly rA, poly rA-rU, native and denatured DNA. All patients with myasthenia gravis had significant anti-acetylcholine receptor antibodies with a mean titre of 1.2 X 10(-7)M. Forty-eight per cent of the myasthenia gravis patients had anti-poly rA antibody levels which were greater than 3 standard deviations from the mean of 65 control patients by Millipore filter radioimmunoassay. The antibody was specific for poly rA and present in a much higher frequency than antibodies to the other nucleic acids tested. Sucrose-gradient ultracentrifugation demonstrated that the antibody was limited to the IgM class alone. Mechanisms relating these findings to a more generalized immunological dysfunction are discussed.