Objective: Idiopathic pulmonary fibrosis (IPF) is a progressive and lethal interstitial lung disease with high mortality.The pivotal role of Th1/Th2 immunological balance in the development and progression of IPF has been demonstrated previously.This study aimed to evaluate the effect of Jinbei Oral Liquid (JBOL) on IPF and its relationship with Th1/Th2 shift.Methods: Rats were divided into six groups: control group,model group (bleomycin),pirfenidone group (positive group,54 mg/kg,i.g.) and JBOL (5.4,10.8 and 21.6 mL/kg,i.g.) groups.The rat model was established by an intratracheal instillation of bleomycin (BLM,5 mg/kg).One day after injection of BLM,pirfenidone or JBOL was given to rats once daily within 28 consecutive days,respectively.Positron emission tomography/computed tomography (PET/CT) was performed on the treated rats.The extent of alveolitis and fibrosis was observed by H&E and Masson trichrome staining.The contents of TGF-β1,TNF-α,IL-4 and IFN-γ were further quantified by ELISA assay.Results: PET/CT and histopathological evidence showed the ability of JBOL to attenuate bleomycininduced alveolitis and fibrosis extent,and the alveolitis lesion score was markedly decreased compared with the model group.The increased expression of inflammatory cytokines TGF-β1 and TNF-α induced by bleomycin was also suppressed by JBOL.The Th1 response was limited by the reduced IFN-γ after BLM administration,and the Th2 response predominated significantly marked by the increased IL-4.JBOL could increase the level of IFN-γ and markedly increased the ratio of IFN-γ/IL-4.Conclusion: These findings suggested that JBOL may attenuate BLM-induced idiopathic pulmonary fibrosis via reducing inflammatory cell infiltration,pro-inflammatory cytokine release and excessive collagen deposition in rats.One of the mechanisms is the reversion of Th1/Th2 shift caused by BLM.