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Keywords:

  • airway remodelling;
  • asthma;
  • IgE;
  • interleukin-33;
  • macrophages

Summary

Allergen-specific IgE has long been regarded as a major molecular component of allergic asthma. Additionally, there is increasing evidence of the important roles of interleukin-33 (IL-33) in the disease. Here, we show that IL-33 and alveolar macrophages play essential roles in the exacerbation of IgE-mediated airway inflammation and remodelling. BALB/c mice passively sensitized with ovalbumin (OVA)-specific IgE monoclonal antibody (mAb) were challenged with OVA seven times intratracheally. The seventh challenge exacerbated airway inflammation and remodelling compared with the fourth challenge; furthermore, markedly increased expression of IL-33 in the lungs was observed at the fourth and seventh challenges. When anti-IL-33 or anti-ST2 antibody was administered during the fourth to seventh challenge, airway inflammation and remodelling were significantly inhibited at the seventh challenge. Because increases of IL-33+ and ST2+ alveolar macrophages and ST2+ CD4+ T cells in the lungs were observed at the fourth challenge, the roles of macrophages and CD4+ cells were investigated. Depletion of macrophages by 2-chloroadenosine during the fourth to seventh challenge suppressed airway inflammation and remodelling, and IL-33 production in the lung at the seventh challenge; additionally, anti-CD4 mAb inhibited airway inflammation, but not airway remodelling and IL-33 production. Meanwhile, treatment with 2-chloroadenosine or anti-CD4 mAb decreased IL-33-induced airway inflammation in normal mice; airway remodelling was repressed only by 2-chloroadenosine. These results illustrate that macrophage-derived IL-33 contributes to the exacerbation of IgE-mediated airway inflammation by mechanisms associated with macrophages and CD4+ cells, and airway remodelling through the activation of macrophages.