['It was recently reported that serum interleukin (IL)-17 levels increased in liver fibrosis associated with human alcoholic liver disease. However, the role of IL-17 in liver fibrosis has not yet been elucidated. Therefore, the aim of this study was to evaluate the role of IL-17 on cholestatic liver fibrosis.', 'IL-17A knockout (KO) and wild-type (WT) mice were subjected to bile duct ligation. Animals were sacrificed at designated times, and serum and liver tissues were collected. The mRNA expression of hepatic fibrotic markers was assessed, and distribution of activated hepatic stellate cells (HSCs) was determined by immunohistochemical staining. In an in\xa0vitro study, Kupffer cells (KCs) and HSCs were isolated from WT mice. KCs were cultured with IL-17A or IL-17F, and production of tumor necrosis factor α (TNF-α) and transforming growth factor β1 (TGF-β1) was measured. HSCs were cultured with IL-17A or IL-17F, and morphologic changes were assessed by immunohistochemical staining.', 'Liver damage observed in the WT mice was significantly improved in the KO mice. Serum TNF-α and TGF-β1 levels were significantly decreased in the KO compared with the WT mice. The hepatic mRNA expression of TNF-α, TGF-β1, and collagen 1α1, which increased in the WT mice, also significantly decreased in the KO mice. Increased hepatic fibrosis in the WT mice was significantly improved in the KO mice. Cytokine production was increased in IL-17A-treated KCs. The most remarkable myofibroblast-like changes were observed in isolated HSCs in the presence of IL-17A.'] Does interleukin-17A play a pivotal role in cholestatic liver fibrosis in mice?