Increased Number of Tc17 and Correlation with Th17 Cells in Patients with Immune Thrombocytopenia Yu Hu1, Dao-xin Ma1*, Ning-ning Shan2, Yuan-yuan Zhu1, Xin-guang Liu1, Lei Zhang3, Shuang Yu1, Chun- yan Ji1, Ming Hou1 1 Department of Hematology, Qilu Hospital, Shandong University, Jinan, People’s Republic of China, 2 Department of Hematology, Provincial Hospital Affiliated to Shandong University, Jinan, People’s Republic of China, 3 Department of Orthopedics, Qilu Hospital, Shandong University, Jinan, People’s Republic of China Abstract Background: IL-17-secreting CD8+ T cells (Tc17 subset) have recently been defined as a subpopulation of effector T cells implicated in the pathogenesis of autoimmune diseases. The role of Tc17 and correlation with Th17 cells in the pathophysiology of immune thrombocytopenia (ITP) remain unsettled. Design and Methods: We studied 47 ITP patients (20 newly-diagnosed and 27 with complete response) and 34 healthy controls. IL-17-producing CD3+CD8+ cells (Tc17) and IL-17-producing CD3+CD82 cells (Th17) were evaluated by flow cytometry and expressed as a percentage of the total number of CD3+ cells. Specific anti-platelet glycoprotein (GP) GPIIb/ IIIa and/or GPIb/IX autoantibodies were measured by modified monoclonal antibody specific immobilization of platelet antigens. Peripheral blood mononuclear cells of ITP patients were isolated, incubated in the presence of 0, 0.25, 0.5, or 1 mmol/L of dexamethasone for 72 h, and collected to detect Tc17 and Th17 cells by flow cytometric analysis. Results: IL-17 was expressed on CD3+CD82 and CD3+CD8+ T cells. The percentages of Tc17 and Th17 cells in newly- diagnosed patients were significantly elevated compared to controls, and Tc17 was decreased after clinical treatment. The Th17:Tc17 ratio was significantly lower in newly-diagnosed patients compared with controls, and was increased in patients who had complete response. There was a significantly positive correlation between Tc17 and Th17 cells in the control group, but not in the ITP patients. A positive correlation existed between Tc17 and the CD8:CD4 ratio, as well as CD8+ cells in patients with ITP. The frequencies of Tc17 were marginally higher in autoantibody-negative patients than autoantibody- positive patients. Moreover, both Tc17 and Th17 cell percentages decreased as the concentration of dexamethasone in the culture media increased in ITP patients. Conclusions: Tc17 and the Th17 subset are involved in the immunopathology of ITP. Blocking the abnormally increased number of Tc17 may be a reasonable therapeutic strategy for ITP. Citation: Hu Y, Ma D-x, Shan N-n, Zhu Y-y, Liu X-g, et al. (2011) Increased Number of Tc17 and Correlation with Th17 Cells in Patients with Immune Thrombocytopenia. PLoS ONE 6(10): e26522. doi:10.1371/journal.pone.0026522 Editor: Jacques Zimmer, Centre de Recherche Public de la Sante´ (CRP-Sante´), Luxembourg Received July 29, 2011; Accepted September 28, 2011; Published October 24, 2011 Copyright: 2011 Hu et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was partially supported by research funding from the National Natural Science Foundation (30600680, 81070396, 81070407, 81170515), the Shandong Technological Development Project (2005BS03022, Q 2008C 07, and BS2009SW014), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (SRF for ROCS, SEM), and Independent Innovation Foundation of Shandong University (IIFSDU; 2009TS063, 2009TS071, and 21300070613233). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: daoxinma@hotmail.com Introduction Immune thrombocytopenia (ITP) is characterized by a low platelet count, which is the result of increased platelet destruction and insufficient platelet production [1]. The pathophysiology of ITP is heterogeneous and complex. T-lymphocyte abnormalities are considered important in patients with ITP. Many cellular mechanisms of immune modulation have been described in patients with ITP, such as T helper 1 (Th1) bias [2], a decreased number or defective suppressive function of regulatory T cells [3], and platelet destruction by cytotoxic T lymphocytes (CTLs) [4]. More recently, utilizing a new animal model of ITP it has been shown that CTLs mediate thrombocytopenia [5]. However, the mechanism of cellular immune abnormalities in patients with ITP remains unclear. Th17 cells comprise a novel Th cell subset characterized by the production of IL-17 [6]. Th17 cells have been shown to play a crucial role in the induction of autoimmune diseases, including rheumatoid arthritis, experimental autoimmune encephalomyelitis (EAE), and allergen-specific responses [7]. In our previous work, we determined the number of Th17 cells in the peripheral blood of ITP patients and healthy controls by flow cytometry through intracellular cytokine analysis, and demonstrated for the first time that Th17 cells are elevated in ITP patients [8]–[][10]. More recently, a completely new subset of IL-17-secreting CD8+ effector cells, so-called Tc17, have been described with a quite different phenotype from other cytolytic T cells. Similar to Th17 cells, na¨ıve CD8+ T cells differentiate into Tc17 cells in the presence of IL-6 and IL-21 along with TGF-b [7]. Tc17 cells secrete IL-17A and IL-17F, and little or no IFN-r and IL-4. In contrast to Tc1 or Tc2, PLoS ONE | www.plosone.org 1 October 2011 | Volume 6 | Issue 10 | e26522