It is well known that sensitization against fungi is closely associated with severity of asthma. Dectin-1 (gene symbol Clec7a), a C-type lectin receptor, recognizes the fungal cell wall component β-glucan, as well as some component(s) in house dust mite (HDM) extract. However, the roles of Dectin-1 in HDM-induced allergic airway inflammation remain unclear. In this study, we used Dectin-1-deficient (Clec7a) mice to examine whether Dectin-1 is involved in HDM-induced allergic airway inflammation. We found that HDM-induced eosinophil and neutrophil recruitment into the airways was significantly attenuated in Clec7a mice compared with that in wild-type mice. In addition, HDM-induced IL-5, IL-13, and IL-17 production from mediastinum lymph node cells was reduced in HDM-sensitized Clec7a mice. Dectin-1 was expressed on CD11b dendritic cells (DCs), an essential DC subset for the development of allergic inflammation, but not on CD103 DCs, plasmacytoid DCs, or lung epithelial cells. Transcriptome analysis revealed that the expression of chemokine/chemokine receptors, including CCR7, which is indispensable for DC migration to draining lymph nodes, was decreased in Clec7a DCs. In accordance with these results, the number of HDM-labeled CD11b DCs in mediastinum lymph nodes was significantly reduced in Clec7a mice compared with wild-type mice. Taken together, these results suggest that Dectin-1 expressed on CD11b DCs senses some molecule(s) in HDM extract and plays a critical role in the induction of HDM-induced allergic airway inflammation by inducing the expression of chemokine/chemokine receptors in DCs.
Ito et al. show that IL-22, which is produced mainly by CD4+ T cells, induces Reg3γ expression from lung epithelial cells through STAT3 activation and suppresses allergic airway inflammation via the inhibition of epithelial cytokine production.
Although potential benefit of AZA maintenance therapy in preventing relapse of EGPA was suggested by the proportional hazards model, there was a discrepancy in the results between the models. Eosinophil counts and IgE levels at onset were also identified as candidates of factors associated with relapse in EGPA.
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