Changes in Serum Complement Activity in Patients with Myasthenia Gravis.

Abstract

From earlier work it is known that serum samples obtained from patients with myasthenia gravis show, more frequently than normal controls, a cytolytic activity against skeletal muscle of the frog. In seeking an explanation of this result, the serum complement (C[image]) activity has been investigated since the C[image] system plays a role in immune hemolysis. Serum C[image] activity was determined on serial samples obtained from 13 normal controls and 68 patients with myasthenia gravis. C[image] activities of all controls fell in a band extending + 20% of the mean normal value. C activities of the serums obtained from individual myasthenic patients often showed considerable variation with time. The extreme C[image] activities found in this group were 0.05 and 2.57 times the mean control value. Study of clinical data gives some indication that during exacerbation of the disease, serum C[image] activity falls to subnormal values and that with remission C[image] activity rises often overshooting the normal range. The possible significance of these changes is discussed and an autoimmune mechanism is proposed to explain the etiology of this disease.