Lymphocyte subpopulation in neoplastic and non-neoplastic thymus and in blood of patients with Myasthenia gravis.

The lymphocyte subpopulations in the thymus and in the blood were investigated in ten myasthenic patients who had been thymectomized. Histologically, the thymuses tested comprised three cases of thymoma including two cases with malignant characteristics, five cases of hyperplastic thymus with lymph follicles and germinal centres, and two cases of persistent thymus without lymph follicles. Virtually all lymphoid cells in the three thymomas formed spontaneous rosettes with sheep red blood cells as did normal thymocytes from non-myasthenic patients. There was no significant proportion of immunoglobulin Ig-bearing lymphocytes. While the majority consisted of cells forming spontaneous rosettes with sheep red blood cells, there was a certain proportion (2-17%) of Ig-bearing lymphocytes in four of five hyperplastic thymuses, in one of two persistent thymuses, and in a residual atrophic thymus of a thymoma. The myasthenic patients tested were for the most part normal, as compared with healthy individuals, in the proportion of rosette-forming lymphocytes and Ig-bearing lymphocytes in the blood collected immediately before and one to three months after thymectomy. The presence of Ig-bearing lymphocytes in the thymus was not necessarily related to the appearance of circulating antibody to striated muscle. The antibody to striated muscle was demonstrated in all myasthenic patients with thymoma.