Thymic and peripheral blood T- and B-cell levels in myasthenia gravis.

We have compared the percentage of T and B lymphocytes in the thymus and peripheral blood populations of patients with myasthenia gravis. There were significantly fewer thymic T cells in myasthenic hyperplastic thymus (MG-H), but not in myasthenia gravis-thymoma (MG-T), compared with normal thymus biopsies obtained at cardiac surgery. Conversely, B cells were increased in MG-H versus MG-T and normals. Peripheral blood T and B cells were not different in any group of myasthenic patients compared to normal populations. In vitro autologous mixed lymphocyte reactions between thymus and peripheral blood lymphocytes occurred in MG-H, but did not correlate with the degree of thymic B-cell increases in these patients.