Objective:To measure the proportions of blood T cell subsets,Th1,Th2,Th17,Th22,and Treg cells,and other parameters in patients with chronic immune thrombocytopenia (CITP) before and after treatment with Yiqi Tongyang Decoction(益气通阳方,YTD) to exploreT cell status of patients with CITP,and to define the mechanism of action of YTD.Methods:The changes in peripheral blood T lymphocyte subsets,and those of Th1,Th2,Th17,Th22,and Treg cells in 30 patients with CITP (22 females and 8 males) were analyzed using multiparametric flow cytometry before and after treatment with YTD for 6 months,and 26 healthy volunteers (14 males and 12 females) acted as a control.T-box expressed in T-cells (T-bet) and GATA binding protein 3 (GATA-3) mRNA levels in patients and controls were analyzed using real-time reverse transcdption-polymerase chain reaction.Results:The proportions of Th1,Th17,Th22,Th1/Th2,and Th17/Treg ceils increased in the peripheral blood of patients with CITP compared to those in controls before YTD therapy (P＜0.05).Th1 cell numbers and the Th1/Th2 ratio fell in the treated patients with CITP to approximate the values of the control group (P＞0.05).Th17 cell numbers and the Th17/Treg ratio also decreased in the treatment group (P＜0.05),but not to the levels of the controls.The number of Treg cells in the peripheral blood of patients with CITP before treatment was lower than that in the control group (P＜0.05),but increased after YTD treatment (P＜0.05),but not to the level of controls.T-bet and GATA-3 mRNA levels in peripheral blood were initially higher in patients before treatment than controls (P＜0.05),but decreased after YTD therapy (P＜0.05).Conclusions:Imbalances in T lymphocyte levels,particularly those of Th1/Th2 and Th17/Treg ceils,play important roles in the pathogenesis of CITP.YTD efficiently regulated the dynamics of Th1/Th2 and Th17/Treg equilibria.