〔Abstract〕 Abstract Objective To explore the central role of interleukin (IL)-25 in allergy of eosinophil asthma. Methods Forty 4 - 5 week-old C57BL/6 mice were used in this study ( n = 10) . Mice were randomly divided into 4 groups : WT + shRNA NT group , WT + HDM group , IL-25 shRNA + IL-25 group , and IL-25 shRNA + IL-25 + HDM group . According to each group ′s treatment requirement , mice were treated with house dust mite and/or IL- 25 by intranasal infusion . HE staining and PAS staining were used for lung tissue section staining and pathological analysis . The levels of type 2 cytokines in bronchoalveolar lavage fluid (BALF) were determined by ELISA . Flow cytometry (FCM) was used to determine the number of type 2 helper T (Th2) cells , the group 2 innate lymphoid cells (ILC2) and eosinophils in lung tissues . Mice were treated with FITC-labeled DQ-ovalbumin (DQ-OVA) by intranasal infusion to determine the antigen presentation ability of eosinophils infiltrated in the lungs . Results HE staining and PAS staining results showed that , compared with WT + shRNA NT group , a large amount of mucus and a large number of eosinophil infiltration were found in the lungs , and subcutaneous thickening of inflammatory air- way were observed in the pulmonary vessels , alveolar ducts and the whole alveoli in IL-25 shRNA + IL-25 + HDM group . In the IL-25 shRNA + IL-25 group , only a small amount of mucus and a small amount of eosinophil infiltra- tion were found in the lungs , and a small amount of subcutaneous thickening of inflammatory airway were observed in pulmonary vessels , alveolar ducts and the whole alveoli . There was no significant difference in WT + HDM group . Compared with WT + shRNA NT group , the levels of IL-25 , IL-4 , IL-5 , IL-13 , IL-33 and interferon-γ (IFN-γ) in BALF significantly increased; the levels of infiltrated Th2 , ILC2 and eosinophils in the lung signifi- cantly increased; the fluorescence levels of FITC-labeled DQ-OVA in eosinophils infiltrated in lungs significantly increased in IL-25 shRNA + IL-25 + HDM group (P < 0. 05) . IL-25 shRNA + IL-25 group mice also showed an in- crease in the above measurements , but the amplitude were limited (P < 0. 05) . WT + HDM group had no signifi- cant difference . Conclusion IL-25 plays an essential role in the allergy and eosinophil antigen presentation processes in eosinophil asthma mice .