Characterization of thymus cells in hyperplastic thymuses in patients with myasthenia gravis and ulcerative colitis with monoclonal antibodies.

Recently, increasing attention has been paid to thymic relevance to pathogenesis in some autoimmune diseases. In this report, the thymus cells from 7 patients with myasthenia gravis (MG) and 6 patients with ulcerative colitis (UC), who had undergone thymectomy for complication of thymic hyperplasia, were studied. The thymus cells were characterized with monoclonal antibodies (Anti-Leu-2a and Anti-Leu-3a) which define human T-cell surface antigens. Although the control thymus consisted of 82-94% of thymocytes which were reactive with Anti-Leu-2a and 90-95% of cells reactive with Anti-Leu-3a, in UC patients both Leu-2a positive thymus cells (38-56%) and Leu-3a positive cells (68-82%) were decreased. Concerning MG thymocytes, Leu-2a positive cells were also decreased (66-81%), but the percentage of Leu-3a positive cells did not show a remarkable change (86-90%) compared with control thymocytes. Considering the above results and many reports telling functional and populational abnormalities of peripheral immunocompetent cells, the process of intra-thymic T-cell maturation may be impaired in these autoimmune diseases.