OBJECTIVE: To observe the changes of interferon-γ (IFN-γ) and interleukin-4 (IL-4), factors related to T helper 1/T helper 2 (Th1/Th2), in airway inflammation in an asthmatic model of mice and the effects of Pingchuan Formula (PCF), a compound traditional Chinese herbal medicine.METHODS: Eighty BALB/c mice were randomly divided into normal group, model group, dexamethasone group and PCF group, with 20 mice in each group. For inducing asthma, the BALB/c mice were sensitized by intraperitoneal injection of mixed ovalbumin, and then activated by inhaling ovalbumin. After 2 weeks of sensitizing, asthmatic mice were intragastrically administered with the drugs once a day for four weeks. Bronchoalveolar lavage fluid (BALF) and lung tissue were collected respectively after 7-day activation or 2 weeks after activation. The general histological changes were observed by hematoxylin and eosin staining and collagen staining, meanwhile the levels of IFN-γ and IL-4 in BALF were detected by enzyme-linked immunosorbent assay.RESULTS: After 7 d of activation, compared with the normal group, significant decrease in IFN-γ and increase in IL-4 were detected in the model group; compared with the model group, IL-4 level of the two treated groups was decreased and the IFN-γ/IL-4 ratio was increased significantly; no significant difference was found between the two treated groups. Two weeks after activation, compared with the normal group, IFN-γ was decreased, IL-4 was increased, and the IFN-γ/IL-4 ratio was decreased in the model group; compared with the model group, IL-4 level in the dexamethasone group was significantly decreased and IFN-γ/IL-4 ratio was significantly elevated, while the level of IL-4 in the PCF group was significantly decreased, the level of IFN-γ was increased simultaneously, and the IFN-γ/IL-4 ratio was significantly elevated. There was no significant difference between the two treated groups in IFN-γ and IL-4 levels, nor in the IFN-γ/IL-4 ratio. The area of collagen fiber in airway wall epithelium in the model group was smaller than that in the normal group, and those in the treated groups were lower than that in the model group; there was no significant difference between the two treated groups.CONCLUSION: PCF has regulating function in correcting the imbalance of Th1/Th2 so as to improve airway inflammation. The therapeutic effects of PCF are basically similar to dexamethasone.