Dectin-2 Induces Allergic Asthma By Activating CDC2s In Lung

OBJECTIVEAllergic asthma is an eosinophil disease,characterized as Th2 immune response.Dectin-2?coded by Clec4n?is a C-type lectin receptor,interacting with allergens,such as house dust mite,to induce an allergic asthma.Using Clec4n^-/-mice,we aimed to investigate the role of Dectin-2 in HDM induced allergic asthma from in vivo and in vitro experiments,with a view to seek a new way for clinical asthma treatment.METHODThe mouse asthma model was constructed by using HDM nasal drip.HE staining,ELISA,flow cytometry,quantitative PCR,western blotting and other methods were used to detect the inflammatory cells infiltration in lung tissue,serum total IgE and HDM-specific IgE production and,expression level of Th1/Th2/Th17 cytokines,IL-33,TSLP and other cytokines or chemokines in bronchoalveolar lavage fluid.Counts and proportions of eosinophils neutrophils,dendritic cells,CD4⁺T cells from lung tissue,mediastinal lymph nodes,and bronchoalveolar lavage fluid.And many other aspects were taken to investigate the role of Dectin-2 in HDM-induced allergic inflammatory responses.Moreover,cDC2s isolated from WT and Clec4n^-/-mice after completion of intratracheal adoptive asthma model were further verified that Dectin-2 promoted the occurrence and development of asthma by regulating the activation of DCs.Finally,Bone marrow derived dendritic cells were cultured in vitro,an effects of dectin-2 on the expression of co-stimulating molecules,antigen presentation function and signal pathway on DCs were observed by flow cytometry,quantitative PCR and western blot.RESULTSAn allergic asthma model was successfully induced in mice.After HDM stimulation,the expression of Clec4n in lung dendritic cells increased significantly.Compared to WT mice,lung eosinophils,neutrophils,and other inflammatory cells infiltration were considerably reduced in Dectin-2 deficient mice(Clecc4n^-/-),all of which were statistically significant.We found that Th2 related cytokines in the BALF of the Clec4n^-/-disease group were significant lower than those in the WT model group,and the recruitment of IL-33,TSLP and chemokine CCL were significantly reduced.This indicates that Dectin-2 may aggravate allergic asthma by promoting Th2 response and cDCs aggregation.Importantly,the number of cDCs in the lungs of the Clec4n^-/-mice model group was significantly lower than that of WT mice,and cDC2s was the dominant type.This indicates that cDC2s may aggravate allergic asthma by promoting lung cDC2s aggregation.Intratracheal administration of WT-cDC2s and Clec4n^-/--cDC2s after HDM challenge was used to sensitize WT mice,and then continuous stimulation with HDM for five consecutive days.We found that the infiltrated inflammatory cells in the alveolar lavage fluid of mice receiving Clec4n^-/--cDC2s was significantly less than receiving WT-cDC2s,which confirmed that cDC2s were the key cells in Dectin-2 affecting the allergic inflammatory response.In vitro experiments,after HDM stimulation,the expression level of co-stimulating molecules and the ability of stimulating T cell proliferation of bone marrow-derived Clec4n^-/--DCs were significantly lower than those of WT-DCs,indicating that Dectin-2affects the activation and antigen presentation ability of DCs.Importantly,after the pretreatment with recombinant IL-33,the expression of CD80 and CD40 of Clec4n^-/--DCs was considerably enhanced.Similarly,after the pretreatment with anti-IL-33 antibody,DCs activation was significantly weakened following HDM stimulation.The phosphorylation level of Syk,P65,IKK?/?,JNK,and P38 of Clec4n^-/--DCs were significantly lower than those of WT-DCs,suggesting that Dectin-2 may promote the activation of DCs induced by HDM through Syk,NF-k B and MAPK pathways.CONCLUSIONDectin-2 exacerbates HDM-induced allergic asthma by promoting cDC2s activation and maturation.