Increased frequency of thymic T follicular helper cells in myasthenia gravis patients with thymoma

Abstract

BACKGROUND: To investigate the presence of T follicular helper (TFH) cells and their associated molecules in myasthenia gravis (MG) patients with thymoma. METHODS: TFH cells are detected in thymus around the thymoma region of 50 patients and atrophic thymus in 10 patients as control. The percentage of TFH cells among CD4(+) T cells and the expression level of surface markers CXC chemokine receptor 5 (CXCR5), inducible co-stimulator (ICOS), programmed cell death 1 and the cytoplasmic marker B cell lymphoma 6 (Bcl-6) were analyzed by immunohistochemistry (IHC) staining, immunofluorescence (IF) and western blotting (WB). RESULTS: Higher percentage of thymic TFH cells was found in MG patients with thymoma compared with both thymoma patients without MG and control group. The expression levels of the four markers in thymoma of MG patients were significantly higher than thymoma patients without MG and control group. No significant difference was found in the levels of programmed cell death 1 (PD-1) and Bcl-6 between thymoma patients without MG and the control, while the levels of CXCR5 and ICOS in thymoma patients without MG were higher than control group. CONCLUSIONS: These results suggested thymic TFH cells might involve in the pathogenesis of MG with thymoma. However, it needs further study to test if the inhibition of the function of TFH cells could effectively alleviate the severity of MG.