Myasthenia gravis induces the activation and maturation of lymphocytes in thymoma.

The biological differences between lymphocytes separated from thymoma patients with myasthenia gravis (MG) and those separated from thymoma patients without MG was examined. We investigated whether lymphocytes in thymoma (Th-L) of patients with and without MG could react to interleukin-2 (IL-2) to develop cytolytic activity against K562 and lympho kine-activated killer (LAK) activity, and their phenotypic changes during incubation with IL-2. Sixteen thymoma patients who consisted of eight patients with MG and eight patients without MG were investigated. Th-L of all MG patients could react to IL-2 to develop LAK activity. Th-L of all of MG patients also developed cytolytic activity against K562 target cells. Cytolytic activity against K562 and LAK activity from Th-L of the MG patients were significantly higher than those from Th-L of the patients without MG (P < 0.01, P < 0.01). The proportions of CD3+ and CD4-/CD8+ cells of Th-L of MG patients increased significantly during the incubation period with IL-2 (P < 0.05, P < 0.05). The proportion of CD4+/CD8+ cells of Th-L of patients with MG decreased significantly (P < 0.05) during incubation with IL-2. On the other hand, there was no significant phenotypic change in Th-L of the patients without MG. These results indicate that MG induces the functional and phenotypic activation and functional and phenotypic maturation of Th-L.