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  • Title: IL-17 is increased in asthmatic airways and induces human bronchial fibroblasts to produce cytokines.
    Author: Molet S, Hamid Q, Davoine F, Nutku E, Taha R, Pagé N, Olivenstein R, Elias J, Chakir J.
    Journal: J Allergy Clin Immunol; 2001 Sep; 108(3):430-8. PubMed ID: 11544464.
    Abstract:
    BACKGROUND: IL-17 is a cytokine that has been reported to be produced by T lymphocytes. In vitro, IL-17 activates fibro-blasts and macrophages for the secretion of GM-CSF, TNF-alpha, IL-1beta, and IL-6. A number of these cytokines are involved in the airway remodeling that is observed within the lungs of asthmatic individuals. OBJECTIVE: In this study, we investigated the expression of IL-17 in sputum and bronchoalveolar lavage specimens obtained from asthmatic subjects and from nonasthmatic control subjects. METHODS: IL-17 was detected through use of immunocytochemistry, in situ hybridization, and Western blot. Bronchial fibroblasts were stimulated with IL-17, and cytokine production and chemokine production were detected through use of ELISA and RT-PCR. RESULTS: Using immunocytochemistry, we demonstrated that the numbers of cells positive for IL-17 are significantly increased in sputum and bronchoalveolar lavage fluids of subjects with asthma in comparison with control subjects (P <.001 and P <.005, respectively). We demonstrated that in addition to T cells, eosinophils in sputum and bronchoalveolar lavage fluids expressed IL-17. Peripheral blood eosinophils were also positive for IL-17, and the level of IL-17 in eosinophils purified from peripheral blood was significantly higher in subjects with asthma than in controls (P <.01). To further investigate the mechanism of action of IL-17 in vivo, we examined the effect of this cytokine on fibroblasts isolated from bronchial biopsies of asthmatic and nonasthmatic subjects. IL-17 did enhance the production of pro-fibrotic cytokines (IL-6 and IL-11) by fibroblasts, and this was inhibited by dexamethasone. Similarly, IL-17 increased the level of other fibroblast-derived inflammatory mediators, such as the alpha-chemokines, IL-8, and growth-related oncogene-alpha. CONCLUSION: Our results, which demonstrate for the first time that eosinophils are a potential source of IL-17 within asthmatic airways, suggest that IL-17 might have the potential to amplify inflammatory responses through the release of proinflammatory mediators such as alpha-chemokines.
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