Elevated Profile Of Th17, Th1 And Tc1 Cells In Patients With Immune Thrombocytopenic Purpura

Background Chronic immune thrombocytopenic purpura(ITP) is an acquired organ-specific autoimmune disease characterized by thrombocytopenia caused by circulating anti-platelet autoantibodies which binds platelet membrane glycoproteins (GPs) mediating the destruction of platelets by macrophages in the reticuloendothelial system.Although autoreactive B lymphocytes secreting antiplatelet antibodies are considered as the primary immunologic defect in ITP,T-lymphocyte abnormalities are considered important in the pathogenesis of ITP.It has become evident that the high Th1/Th2 ratio was closely related to the etiology and disease status of chronic ITP, and described a higher Th1 response.Studies suggest that Tc1 cells which can produce IFN-γand IL-2 like Th1 cells have been linked to the development of some autoimmune diseases and chronic infective disease.Th17 characterized by the production of interleukin 17(IL-17) has been shown to play a crucial role in the development of autoimmune diseases.Objective To further investigate the role of Th17,Th1 and Tc1 cells,as well as their relationship in the pathogenesis of ITP,and evaluated their clinical relevance.Design and Methods(1) Patients and controls:Thirty adult chronic ITP patients were enrolled by diagnostic criteria for ITP.All the patients' platelet count ranged between 1 and 30×109/L,and all required treatment because of clinically significant bleeding.Patients complicated with viral hepatitis,diabetes,hypertension, cardiovascular diseases,pregnancy,active infection,or connective tissue diseases, were excluded.The control group consisted of 30 adult healthy volunteers matched for sex and age with the study population and platelet counts were ranged from 136 to 298×109/L.(2) We examined the levels of Th17,Th1 and Tc1 cells in peripheral blood which was activated in vitro by PMA/ionomycin in short-term cultures in ITP patients and controls by flow cytometry through intracellular cytokines analysis.Th17 cells and Th1 cells were identified as those that were CD3+CD8—IL-17A+and CD3+CD8—IFN-γ+,and Tc1 cells were those that were CD3+CD8+IFN-γ+.(3) ELISA was used to detect the expression of Th1 and Th17 cytokines(IFN-.and IL-17) in plasma. (4)Anti-platelet autoantibodies were detected using the modified MAIPA(monoclonal antibody immobilization of platelet antigens) assay.Results The results showed that the percentages of both Th1 and Tc1 in ITP patients increased significantly compared with the normal controls(P＜0.01 for Th1, P＜0.05 for Tc1),and there was a significantly positive correlation between Th1 and Tc1(r=0.58,P=0.01) in ITP patients.More importantly,the percentage of Th17 in patients with ITP was markedly higher than that of normal controls(P＜0.05).Also, the percentage of Th17 positively correlated with Th1(r=0.61,P=0.007) while there was no significant correlation between Th17 and Tc1(r=0.09,P=0.71).No significant associations of megakaryocyte quantity and anti-platelet autoantibody with the three kinds of cells were found,and there were no statistical differences between primary ITP and recurrent ITP patients.Besides,there are no significant differences between ITP patients and controls in the expression IFN-γ.and IL- 17 in plasma.Conclusions Our study data strongly support a high Th1 and Tc1 polarization of the immune response in ITP and CTL-mediated cytotoxicity is an alternative mechanism for platelet destruction in ITP,and Tc1 may play roles of both cytotoxicity and immune regulation in the pathogenesis of ITP.More important,our study demonstrates for the first time that Th17 may be an important determinant in the evolution of ITP along with Th1 and Tc1,suggesting that blocking the abnormality of Th17 cell in ITP is likely a promising therapeutic concept for ITP.