To study the regulation of T helper cell 2（TH2）immune response in rats with allergic rhinitis（AR）by Ebushicao（Centipeda minima）extract via mediating Toll-like receptor-nuclear factor kappa B（TLR/NF-κB）signaling pathway.

ARmodels were induced with ovalbumin（OVA），and the rats were divided into model group，positive control group and Ebushicao（Centipeda minima）extract treatment groups（low，middle，high concentrations）.The rats in the positive control group were given loratadine（2 mg/kg）by gavage.The rats in the Ebushicao（Centipeda minima）extract treatment groups were given Ebushicao（Centipeda minima）extracts with the corresponding doses（2 mg/kg，4 mg/kg，8 mg/kg）by gavage，while those in the blank control and model groups were given an equal volume of saline by gavage.The treatment in all groups lasted for 10 days.Weights of nasal secretions were collected from the rats in each group and the scores for nasal symptoms were calculated.HE staining was used to observe the morphological changes of nasal mucosa，and the counts of eosinophils and neutrophils in nasal mucosa were calculated.The levels of interleukin-4（IL-4），interleukin-13（IL-13）and immunoglobulin E（IgE）in peripheral blood of rats in each group were detected by ELISA.The mRNA and protein expression levels of TLR-4 and NF-κB were detected by RT-PCR and Western-blot.In Ebushicao（Centipeda minima）extract treatment groups，the rats received natural TLR4 agonist lipopolysaccharide（LPS）and were observed for morphology of the nasal mucosa and nasal symptoms.

Compared with the blank control group，the rats in the model group had a significant increase in behavioral score of nasal symptoms，the levels of serum IL-4，IL-13 and IgE，the levels of eosinophil and neutrophi in nasal mucosal tissues，and the relative mRNA and protein expressions of TLR4 and NF-κB in nasal mucosal tissues，with statistical difference（P<0.05），while the above increases were notably diminished to varying degrees in the positive control group and Ebushicao（Centipeda minima）extract treatment groups（P<0.05）.Within Ebushicao（Centipeda minima）extract treatment groups，a gradual decline was observed in the above indexes as the concentration increased，with statistical difference in paired comparison（all P<0.05）.HE staining showed that the nasal mucosa of the control rats was normal pseudostratified ciliated columnar epithelium with intact mucosal epithelial structure and there was no obvious inflammatory cell infiltration.The epithelium of the nasal mucosa of the rats in the model group was heavily detached，and a large number of eosinophils and mast cells were observed in the lamina propria of the mucosa.Various degrees of pathological changes were also found in positive control group and Ebushicao（Centipeda minima）extract treatment groups，while the changes were remarkably attenuated compared with those in the model group.The weakening of pathological changes showed a concentration dependent manner within Ebushicao（Centipeda minima）extract treatment groups.After TLR4 agonist treatment，the improved AR symptoms and pathological changes in Ebushicao（Centipeda minima）extract treatment groups were reversed.

The mechanism of Ebushicao（Centipeda minima）extract in the treatment of AR may be related to the inhibition of TLR/NF-κB signaling pathway and alleviation of TH2 immune response.