Antibodies to thymic epithelial cells in myasthenia gravis

The presence of anti-thymus antibodies was investigated in the serum of 36 patients with myasthenia gravis (MG). Using an immunofluorescence technique on frozen thymic sections, we found 45% of patients sera reacting with normal or MG thymuses. Staining was confined to subcapsular and medullary keratin-positive epithelial cells. Thirty-five out of 36 sera from healthy controls and all 15 sera from patients presenting another autoimmune disorder were negative. Antibodies to thymic epithelial cells were almost exclusively detected in patients presenting thymic hyperplasia and did not disappear after thymectomy. They were not clearly associated with antiacetylcholine receptor antibody titer, nor with disease severity. Their strong association to thymic abnormalities highlights the role of the thymus in pathogenesis of MG. The reasons for the appearance of these antibodies, the structure they recognize on thymic epithelial cells and their possible etiological role are discussed.