Abstract
It has frequently been suggested that the deficit in neuromuscular transmission characteristic of patients with myasthenia gravis might be produced by a curare-like agent which can circulate in the blood. In a search for such an agent, previously described (1), serum samples obtained from a series of individuals afflicted with myasthenia gravis were tested for neuromuscular blocking action. The assay involved measurement of the changes in muscle tension output of an indirectly stimulated frog sartorius muscle-sciatic nerve preparation which was immersed in the diluted serum.
Serum samples obtained from a few myasthenic patients caused a reduction in muscle tension output, and this result appeared to parallel the cytolytic destruction of fibers lying on the surface of the sartorius muscle used in the assay (1). From these and more recent observations(2), it is clear that serum exhibiting the above type of cytolytic activity occurs in 44% of patients afflicted with myasthenia gravis and in 22% of normal controls. The relative strengths of the active serums found in each group are unknown.
The results described above led us to think about the nature of the cytolytic system involved and the possible connection between the activity of this system and etiologic factors which operate in myasthenia gravis. As to the nature of the cytolytic system, we speculated that serum complement (C') might be concerned because, as is well known, C' plays an essential part in immune hemolysis. For this and other reasons, it seemed worthwhile to carry out determinations of C' activity on serum obtained from myasthenic patients. Encouragement was provided by the early results which showed that in many myasthenic patients, serum C' activity was far outside the normal range.
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