Objective: To explore roles of triptolide in the regulation of T cell subsets in the asthma.Methods: C57BL/6J mice exposed to chicken egg ovalbumin to induce asthma were treated with triptolide or dexamethasone.The lungs were processed for immunohistochemical analysis of leucocyte infiltration.Sera and bronchoalveolar lavage fluid (BALF) were sampled to quantify IgE and cytokines by ELISA.The master transcription factors for the CD4+ T cell subsets in the lung were measured in the quantitative RT-PCR.In addition, CD4+ T cells in the lung were stained and evaluated using flow cytometry analysis.Results: Triptolide significantly inhibited the inflammatory response in the airway and serum IgE in the mice with asthma.Both eosinophils and neutrophils in the BALF were significantly decreased by triptolide.Triptolide up-regulated IFN-γbut significantly down-regulated IL-4, IL-5, IL-10, IL-13, IL-17, TNF-α, and TGF-β in the BALF.The key transcription factor for Thl cells, T-bet, was significantly augmented in the lung upon triptolide treatment, while those Gata-3 (Th2), RORγt (Th17) and Foxp3 (Treg) were significantly decreased by triptolide.In accordance with the shift in transcription factors, administration of triptolide significantly increased Th1 but suppressed Th2 and Th1 7 cells in the lungs from asthmatic mice.Conclusions: Findings presented here suggest that the anti-asthmatic effects of triptolide may be due to its regulatory effects on Th1/Th2 balance and on Th17/Treg equilibrium in asthma.