To investigate the significance of humoral immunological factors in juvenile myasthenia gravis (JMG) patients, 11 children with JMG (age of onset between 2 and 13 years) and 8 healthy controls were enrolled. Plasma IL-2, IL-10, IFN-gamma, TNF-alpha, complement factor C3, C4, and C1q levels were measured by ELISA. IL-2, IL-10, TNF-alpha, C3, and C4 levels were significantly elevated in the patient group. Moreover, plasma IL-10 levels were associated with the presence of anti-AChR antibody and response to treatment suggesting a critical role for IL-10 in JMG pathogenesis.