Detection and quantification of pathological changes of NMJ function. (A-C) Contractility traces in response to optical stimulation of a representative tissue before (A, score = 0.78) and after (B, score = 0) 48h of treatment with 20% of myasthenia gravis (MG) serum and 48 after removal of the serum (C, score = 1). (D) Effect of human sera from healthy donors and MG patients on NMJ function (n = 12; after treatment ANOVA F = 0.0002; * p = 0.0015 **p = 3.5·10-6), and recovery after washing. Sera was added at day 18 after the beginning of the coculture. (E) Differential effect of sera from 3 different donors at different concentrations (n = 15; after treatment ANOVA F = 2·10-5; *p< 0.01 vs control group). Treatment was started at day 14 with sequential dose increments at days 16, 18 and 20. Error bars = SEM.