Studies on lymphocyte subsets in thymic tissue and functions of peripheral lymphocytes in patients with tumorous thymus with special reference to myasthenia gravis.

In order to obtain a better understanding of the immunological abnormalities present in myasthenia gravis (MG), which is often accompanied by thymoma or thymic hyperplasia, we investigated lymphocyte subsets and their functions using samples of thymoma or thymic hyperplasia tissues from 11 patients (6 cases with MG), and peripheral blood from 6 patients (4 cases with MG). In most thymic tissues from patients with MG, a maturating tendency of lymphocytes was generally observed. Especially in the medulla of thymic hyperplasia, an entirely peripheral blood type of T-lymphocytes, which were Leu-6- and either Leu-2a+ or 3a + 3b+, were encountered abundantly. Therefore, the presence of abnormal maturation of lymphocytes in the thymus or destruction of the barrier between the thymus and the peripheral blood in MG cases was indicated. In cases without MG, no such tendency was noted. As to the peripheral blood in patients with MG, concanavalin A-induced suppressor cells were significantly decreased (p less than 0.01). All of these changes were considered to be intimately related to the appearance of MG.