Decreased frequency of intrathymic regulatory T cells in patients with myasthenia-associated thymoma.

Naturally occurring CD4+CD25+ regulatory T cells (Treg) are essential for the control of unwanted autoimmune responses. In this study, we analysed their frequency in peripheral blood and in the thymus/thymomas of patients with myasthenia gravis (MG). We found a marked decrease in the number of CD4+CD25+ thymocytes in MG-associated thymomas, but no differences in the peripheral compartment, suggesting that the thymic development of Treg might be impaired in these patients.