We further examined the role of the endogenous IL-9 in hepatic fibrosis and its relationship with other relevant cytokines, including IL-17A, IFN-γ, TGF-β1, IL-6, IL-4, IL-21 and TNF-α in response to hepatic fibrosis, by neutralizing IL-9 in a mouse model. The gene discussed is IL21; the disease is Hepatic fibrosis.