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Summary1. A muscle binding, complement fixing component has been demonstrated in the crude globulin fraction of a pool of serum from 10 patients with myasthenia gravis of recent onset and progressive character, by means of the immunofluorescence technic. This component could not be demonstrated in a similarly prepared normal serum globulin pool. Untagged myasthenic globulin was shown to block competitively adherence of fluorescein tagged myasthenic globulin to skeletal muscle striations; whereas prior treatment of muscle sections with normal serum globulin intensified staining with fluorescein tagged myasthenic globulin. Individual myasthenia gravis serums included in the pool also blocked staining with fluorescein conjugated myasthenic globulin. Normal serums did not block adherence of the fluorescein tagged myasthenic globulin to skeletal muscle. 2. The myasthenia gravis globulin fraction was shown to fix guinea pig complement to human skeletal muscle, by successive treatment of muscle sections with myasthenic globulin, guinea pig complement, and fluorescein conjugated rabbit anti-guinea pig complement. Normal serum globulin failed to fix complement by this technic. 3. Thirty-one myasthenia gravis serums were screened, with 11 normal serums, and 5 serums from patients with other generalized myopathies, for their ability to fix guinea pig complement to skeletal muscle. Thirteen myasthenic serums gave unequivocal evidences of complement fixation, using the immunofluorescence technic. No normal serums fixed complement. Serum from one patient with paroxysmal myoglobinuria also fixed complement. Serum from one patient with acute dermatomyositis gave rise to fluorescence in the sarcolemma when layered onto skeletal muscle followed successively by guinea pig complement and fluorescein conjugated rabbit anti-guinea pig complement.
Strauss et al. (Sat,) studied this question.