AIM:To investigate the effect of T helper(Th)17/T regulatory(Treg)cells on hepatic fibrosis in mice and its possible mechanism.METHODS:Hepatic fibrosis was induced by intraperitoneal injection of carbon tetrachloride.Hepatic pathological changes were observed by hematoxylin and eosin staining;the protein levels of interleukin(IL)-6,transforming growth factor(TGF)-βandα-smooth muscle actin(SMA)in liver tissue were determined by Western blotting;and the frequency of Th17 and Treg cells in the liver was estimated by flow cytometry.In addition,hepatic stellate cells were isolated from healthy mouse liver and co-cultured with Th17 or Treg cells.Immunofluorescence staining and Western blotting were performed to determine the change in HSC activation.RESULTS:In the model group,there were different degrees of fibroplasia,degeneration and necrosis.The protein levels of IL-6,TGF-βandα-SMA in liver tissue were significantly higher than those in the control group at 12 wk(P<0.05).Compared with the control group,the frequency of Th17 cells in the model group was increased but the frequency of Treg cells decreased gradually.Furthermore,at 4,8 and 12 wk,there were significant differences in the number of Th17 cells(0.52%±0.16%,1.46%±0.24%,and2.60%±0.41%,respectively,P<0.05)and Treg cells(2.99%±0.40%,2.16%±0.50%,and 1.49%±0.34%,respectively,P<0.05).In vitro,Th17 cells promoted,whereas Treg cells inhibited the expression ofα-SMA,both in a dose-dependent manner,compared with the control group.CONCLUSION:Th17/Treg imbalance exists in mice with liver fibrosis,which potentially promotes liver fibrosis via HSC activation. AIM: To investigate the effect of T helper (Th) 17 / T regulatory (Treg) cells on hepatic fibrosis in mice and its possible mechanism. METHODS: Hepatic fibrosis was induced by intraperitoneal injection of carbon tetrachloride. Hepatatic pathological changes were observed by hematoxylin and the protein levels of interleukin (IL) -6, in transforming growth factor-β and α-smooth muscle actin (SMA) in liver tissue were determined by Western blotting; and the frequency of Th17 and Treg cells in the liver was estimated by flow cytometry. In addition, hepatic stellate cells were isolated from healthy mouse liver and co-cultured with Th17 or Treg cells. Immunofluorescence staining and Western blotting were performed to determine the change in HSC activation .RESULTS: In the model group, there were different degrees of fibroplasia, degeneration and necrosis.The protein levels of IL-6, TGF-βandα-SMA in liver tissue were significantly higher than those in the control group at 12 wk (P <0.05) .Compared with the control group, the frequency of Th17 cells in the model group was increased but the frequency of Treg cells decreased gradually. Morerther, at 4,8 and 12 wk, there were significant differences in the number of Th17 cells (0.52% ± 0.16% , 1.46% ± 0.24%, and 2.60% ± 0.41% respectively, P <0.05) and Treg cells (2.99% ± 0.40%, 2.16% ± 0.50%, and 1.49% ± 0.34% In vitro, Th17 cells promoted, whereas Treg cells inhibited the expression of alpha-SMA, both in a dose-dependent manner, compared with the control group. CONCLUSION: Th17 / Treg imbalance exists in mice with liver fibrosis, which potentially promoted liver fibrosis via HSC activation.