【Abstract】 Objective To study the role of house dust mite ( HDM) induced airway epithelium TLR4 expression and T lymphocyte activation in asthmatic inflammation. Methods Thirty BALB/ c mice were randomly divided into an ovalbumin ( OVA) group, a HDMgroup, and a control group. The mice in the OVA group were sensitized with OVA and Al( OH) 3 , and repeatedly exposed to aerosolized OVA. The mice in the HDMgroup and the control group were sensitized and challenged with HDMand saline, respectively.Histopathology changes of pulmonary tissue and airway were observed under light microscope. Levels of IL-4, IL-5, IL-13, IL-17, and IFN-γin BALF were measured by ELISA. Total and differential cell counts in bronchoalveolar lavage fluid ( BALF) were also measured. The mRNA and protein expressions of TLR4 weredetected by quantitative real-time PCR and Western blot, respectively. Th1, Th2, and cells in the peripheral blood were detected by flow cytometry. Results Light microscope revealed eosinophil specific inflammatory cells infiltration around the peribronchovascular region,mucus gland hyperplasia, and airway mucous plug inthe OVA group. The HDM group showed more severe alveolar and intersititial congestion and neutrophils infiltration. The control group showed intact alveolus with few mucous plug and inflammatory cells.Compared with the OVA group, significant increases in the number of total cells and neutrophils, as well as significantly higher expression of IL-4, IL-5, IL-13, and IL-17 were detected in the HDMgroup ( P lt;0. 05) ,while IFN-γexpression had no significant change ( P gt;0. 05) . The expression of TLR4 mRNA and protein significantly increased in the HDMgroup( P lt; 0. 05) , and did not change significantly in the other two groups ( P gt;0. 05) . The percentages of Th2 and Th17 cells in peripheral blood in the HDMgroup were significantly higher than the OVA group ( P lt;0. 05) . Conclusion HDM may induce inflammatory cells infiltration andactivation of Th2 and Th17 lymphocyte cells via up-regulation of TLR4 expression in airway epithelium,which might play an important role in asthmatic inflammation.