T helper type 17 cells expand in patients with myasthenia-associated thymoma.

Myasthenia gravis (MG) is a prototypical CD4(+) T cell-dependent autoimmune disease mediated by anti-acetylcholine receptor autoantibodies (AChR-Abs). Certain subsets of helper T cells are suggested to be involved in the pathogenesis of MG, including Th1 and regulatory T cells (Treg). However, whether the recently identified Th17 cells play a role in the development of MG and its prognosis is still unknown. Here, we demonstrated that Th17 cells and their associated cytokines are increased, while the Treg cells are decreased in the peripheral blood mononuclear cells (PBMCs) from MG patients with thymomas (TM), but not from those with normal thymus (NT) or thymic hyperplasia (TH). Furthermore, the quantity of Th17 cells correlates with the quantitative myasthenia gravis (QMG) score in patients with TM. We also found a significant positive relationship between the frequency of Th17 cells (%) and the concentration of AChR antibodies in patients with MG. Therefore, the Th17/Treg imbalance in TM may suggest MG with certain pathological subtype, and the increase in Th17 cells may reveal the severity of the disease, which is valuable in the diagnosis and choice of therapeutic strategy for patients with MG.