Changes in Follicular Helper T Cells in Idiopathic Thrombocytopenic Purpura Patients

Background: Idiopathic thrombocytopenic purpura (ITP) is a primary autoimmune disease with a decreased platelet count caused by platelet destruction mediated mainly by platelet antibodies. T follicular helper (TFH) cells have demonstrated important roles in autoimmune diseases. The aim of this study is to explore the might role of TFH cells in the patients of ITP.Methods: Twenty-three ITP patients and 12 healthy controls (HC) were enrolled in this study. The frequency of circulating TFH cells in both the patients and HC was analyzed by flow cytometry. Serum interleukin (IL)-21 and IL-6 levels were measured using ELISA, and platelet antibodies were tested using a solid phase technique. Additionally, IL-21, IL-6, Bcl-6 and c-Maf mRNA expressions in peripheral blood mononuclear cells (PBMCs) were detected using real-time PCR.Results: The percentages of circulating CXCR5⁺ CD4⁺TFH cells with ICOS^high or PD-1^high expression were significantly higher in the ITP patients than in the HC. Moreover, the frequencies of circulating CXCR5⁺ CD4⁺TFH cells with inducible costimulator (ICOS)^high or programmed death-1 (PD-1)^high expression were notably higher in ITP with platelet-antibody-positive ( ITP (+) ) patients than in ITP with platelet-antibody-negative ( ITP (-) ) patients and HC, as were the serum IL-21 and IL-6 levels (significant). Moreover, a positive correlation was found between the CXCR5⁺CD4⁺TFH cells with ICOS^high or PD-1^high expression and the serum IL-21 levels of ITP (+) patients. Additionally, the mRNA expression levels of IL-21, IL-6, Bcl-6 and c-Maf were significantly increased in ITP patients, especially in ITP (+) patients.Conclusions: This study demonstrated TFH cells and effector molecules might play an important role in the pathogenesis of ITP, which are possible therapeutic targets in ITP patients.