Objective:To observe the expression of T helper type 17 (Th17) cells and T regulatory (Treg) cells in the peripheral blood from patients with hepatitis B,and study the relationship between Th17,Treg cells,and clinical parameters. Methods:The frequencies of peripheral Treg and Th17 cells of seventeen chronic hepatitis B(CHB) patients,thirteen acute hepatitis B (AHB) patients and fourteen healthy controls(HC) were determined by flow cytometry. Serum concentration of cytokine interleukin (IL)-17 was detected by enzyme-linked immunosorbent assay(ELISA). The HBV DNA loads were measured by Real-time PCR. The level of serum alanine aminotransferase(ALT) was measured by velocity method. Results:In the periphery of CHB and AHB patients,both Th17 frequency and serum level of IL-17 were significantly increased than those in HC subjects(P < 0.05). The peripheral Treg frequency in CHB patients was significantly higher compared with HC subjects (P < 0.01),whereas there was no significant difference between AHB patients and HC subjects(P > 0.05). Compared with HC subjects,the peripheral Th17/Treg ratio of CHB patients was dramatically lower whereas the ratio in AHB patients were significantly higher (P < 0.05). The peripheral Th17 frequency and Th17/Treg ratio were positively correlated with ALT level whereas Treg frequency was positively correlated with HBV-DNA load. Conclusion:In the periphery of patients with hepatitis B,the expression levels of Th17 and Treg cells were both abnormal,meanwhile,there was a relative Th17/Treg imbalance. Futhermore,the peripheral Th17 frequency,Treg frequency as well as the ratio of Th17/Treg were positively correlated with the level of ALT and HBV DNA load. It is suggested that Th17 and Treg cells may play an important role in the pathogenesis of hepatitis B.