Abstract: Objective To explore thefrequency of Th1, Th17 and Treg cells in peripheral blood of children with ITP and its clinical significance. Methods Forty-six children with ITP diagnosed and treated in our hospital from June 2017 to September 2018 were enrolled as a case group, and 40 children in the same period were examined as health controls. The frequency of Th1, Th17, Th2 and Treg cells in peripheral blood mononuclear cells were detected by flow cytometry. The cytokines IFN-γ, IL-4 and IL-17 were detected by enzyme-linked immunosorbent assay （ELISA）. The relationship between Th17, Th2, Treg cell ratio, cytokine-level and different periods of disease and platelet levels were analysed. Results The ratio of Th1 cells and Treg cells and the level of IFN-γ、IL-17 in peripheral blood of the case group were lower than that of the control group, and the proportion of Th2, Th17 and the level of IL-4 were higher than that of the control group, the difference was statistically significant （P<0.05）. The levels of Th1, Treg and platelet count in peripheral blood of children in case group after treatment were higher than those before treatment, while the levels of Th2, Th17 and Th2 were lower than those before treatment, the difference was statistically significant （P<0.05）. The change of platelet count before and after treatment were positively correlated with Treg and Th1 levels （r=0.461, 0.383）, and negatively correlated with Th17 and Th2 levels （r= -0.362, -0.311）. Conclusion The unbalanced proportion of Th1, Th2, Th17, Treg cells and cytokines in peripheral blood is related to the pathogenesis of ITP in children. T lymphocytes can be used to predict disease status and platelet level.

Key words: Immune thrombocytopenic purpura, Lymphocytes, Regulatory T cells, Cytokine