[TCR alpha beta + CD4- CD8- T cells among the peripheral blood mononuclear cells of myasthenia gravis patients].

We investigated the occurrence of TCR alpha beta + CD4- CD8- mononuclear cells (DN alpha beta T cells) and TCR gamma delta + CD3+ mononuclear cells (gamma delta T cells) among the peripheral blood mononuclear cells of 22 myasthenia gravis patients (MG) and 22 controls in order to examine whether extrathymic T cell subpopulations might be responsible for the pathogenesis of MG. The differences between the mean percentages of both DN alpha beta T cells and gamma delta T cells in the MG patients (DN alpha beta T cells: 0.53 +/- 0.51%, gamma delta T cells: 3.45 +/- 2.79%) and the controls (DN alpha beta T cells: 0.32 +/- 0.16%, gamma delta T cells: 3.81 +/- 2.36%) were not significantly different. However, higher DN alpha beta T cells ratios (1.48 approximately 1.84%) were noted in three MG patients. Thymectomy and subsequent thorough dissection of the anterior mediastinum 3 years after thymectomy had no effect on the symptoms of one patient, a 25-year-old woman without thymoma. The other two patients, a 45-year-old man and a 41-year-old woman without thymoma, had recurrences despite long-term remissions (14 years and 30 years, respectively) after thymectomy. Examination of DN alpha beta T cells, which are probably generated extrathymically without negative selection, may play an important role in understanding the pathogenesis in these three cases of MG.