Role of Interleukin-25 in allergic airway inflammation and vascular damage

T helper 2 (Th2) cells induce allergic inflammation through the production of Th2 cytokines such as IL-4, IL-5, and IL-13. In addition, it has been demonstrated that IL-25 (IL-17E) is a product of activated Th2 cells and initiates and augments Th2-type immune responses. Moreover, recent studies have shown that IL-25 is produced by a number of cell type including, epithelial cells, mast cells, eosinophils, and macrophages. It has also been shown that IL-25 induces Th2-type immune responses through the activation not only of Th2 cells but also of NKT cells and innate cells including MHC IIhigh CD11clow cells, multipotent progenitor cells, natural helper cells, and nuocytes. In vivo, we and others have shown that IL-25 is expressed in the airways in murine asthma models and is involved in the induction of antigen-induced airway inflammation. In human, IL-25 is suggested to be involved in the pathogenesis of asthma and Churg-Strauss syndrome.