OBJECTIVE: To investigate the expression of IL- 23/IL- 17 axis in peripheral blood of patients with primary immune thrombocytopenia （ITP） and its clinical significance.METHODS: The real-time quantitative reverse transcription-polymerase chain reaction（RT-PCR）was used to determine the expression of IL-23p19, p40, p35, IL-23R, IL-12Rbeta1, IL-12Rbeta2, IL-17A, IL-17F mRNA in the peripheral blood of 45 ITP patients and 30 healthy controls. The correlations between the expression of IL-23 and IL- 17, platelet counts, serum cytokine concentrations of ITP patients were analyzed. Furthermore, nine newly diagnosed ITP patients were followed up during treatment.RESULTS: The gene expressions of IL-23p19, p40, IL-23R, IL-12Rbeta1, IL-17A, IL-17F in ITP patients were significantly higher than those in healthy controls, the relative expression levels of ITP were 5.58, 2.13, 4.20, 2.45, 4.29, 2.50 times as much as that of healthy controls. And elevated serum IL-23［（198.70±94.56）ng/L vs（50.72±22.97）ng/L, t= 10.06, P<0.001］, IL-17［（85.25±21.97）ng/L vs（11.39±4.27）ng/L, t=21.94，P<0.001］levels were also observed in these ITP patients. In addition, the serum IL-23 level in ITP patients was positively correlated with IL-17（r=0.496, P<0.01）, but negatively correlated with the platelet counts（r=-0.408, P<0.01）, and IL-17 level was negatively correlated with platelet counts（r=-0.464, P<0.01）.CONCLUSION: The IL-23/IL- 17 expression in ITP patients was significantly elevated, indicating IL-23/IL-17 play an important role in the pathogenesis of ITP.