OBJECTIVE: To explore the profiles of Th1, Th2, Th17 and Regulatory T (Treg) cells in patients with chronic idiopathic thrombocytopenic purpura (ITP). METHODS: Samples of peripheral blood were collected from 35 chronic ITP patients (21 in an active stage group, 5 in a non-remission stage group, 9 in a remission stage group) and also from 18 healthy subjects. Flow cytometry was used to measure the intracellular cytokines interferon (IFN)gamma, interleukin (IL)-4 and IL-17 so as to identify the Th1, Th2 and IL-17 cells. Treg cells were identified with CD(4)(+) CD(25)(+) Foxp3(+) cells and uncultured peripheral blood was used to measure the CD(4)(+) CD(+)(25) Foxp3(+) cells with flow cytometry. The concentrations of IFNgamma, IL-4, IL-17 and IL-10 in plasma specimens were detected with ELISA method and its correlation with peripheral platelets counts and megakaryocytes number was analyzed, respectively. RESULTS: There were no statistically significant differences between any two of the three groups for the percentage of Th1 cells, Th17 cells and Th1/Th17 ratio. The percentage of Th2 cells was (1.01 +/- 0.88)% in active stage and (1.22 +/- 1.04)% in non-remission stage, being significantly decreased than those in remission stage (1.93 +/- 1.04)% (P < 0.05) and the controls (1.86 +/- 0.59)% (P < 0.05). Th1/Th2 ratio was 15.04 +/- 9.67 in active stage, 11.65 +/- 9.32 in non-remission stage, which were significantly higher than those in remission stage (7.17 +/- 5.38, P < 0.05) and the controls (7.02 +/- 3.01, P < 0.05). The percentage of Treg cells was (0.89 +/- 0.58)% in active stage and (1.46 +/- 1.27)% in non-remission stage, being significantly decreased than those in remission stage (6.41 +/- 1.86)% (P < 0.01) and the control (5.73 +/- 0.71)% (P < 0.01). There was no statistic difference between any two of the three groups for plasma IFNgamma and IL-17 level. The plasma IL-4 level was (2.25 +/- 2.05) ng/L in active stage and (2.33 +/- 2.14) ng/L in non-remission stage, being significantly decreased than those in remission stage (6.00 +/- 4.57) ng/L (P < 0.05) and the controls (5.54 +/- 4.00) ng/L (P < 0.05). The plasma IL-10 level was (5.07 +/- 4.10) ng/L in active stage and (5.66 +/- 4.35) ng/L in non-remission stage, being significantly decreased than those in remission stage (10.92 +/- 6.17) ng/L (P < 0.01) and the controls (14.21 +/- 7.31) ng/L (P < 0.01). The plasma level of IL-10 in patients in active stage was positively related to the platelet counts (r = 0.16, P = 0.03). CONCLUSION: Deficiency of Treg cells might be one of mechanisms that cause immune regulation dysfunction in chronic ITP. Th17 cells might not play a role in the development of chronic ITP.