Cellular immunity in myasthenia gravis. Response to purified acetylcholine receptor and autologous thymocytes.

To determine the potential importance of an immune response directed against the acetylcholine receptor in myasthenia gravis, we studied cell-mediated immunity to receptor as measured by lymphocyte stimulation in 21 myasthenic patients and 21 controls, including five with amyotrophic lateral sclerosis. The mean (+/- S.E.M.) stimulation index was 5.3 +/- 1.3 for patients and 1.2 +/- 0.3 for controls (P less than 0.005). Fourteen patients had indexes greater than 2.0 (nine of 11 males, five of 10 females, 10 of 11 elderly patients, and five of six with thymoma). Stimulation index correlated with disease activity (rs = 0.71, P less than 0.01). Peripheral blood lymphocytes from one of three young female myasthenic patients responded to autologous thymocytes but not to receptor; peripheral blood lymphocytes from the other two responded to receptor but not to autologous thymocytes. Our findings are further evidence that autoimmunity to the acetylcholine receptor plays a central part in myasthenia gravis.