The Th17 pathway in cystic fibrosis lung disease.

Rationale: Cystic fibrosis (CF) is characterized by bronchoalveolar neutrophilia and submucosal lymphocytosis. We hypothesized that Th17 lymphocytes are part of this submucosal infiltrate.Objectives: Quantification and phenotyping of the lymphocytic infiltrate in the bronchial submucosa of patients with CF (n = 53, of which 20 were newly diagnosed), non-CF bronchiectasis (n = 17), and healthy control subjects (n = 13).Methods: We measured IL-17 levels in bronchoalveolar lavage and CD4+, CD8+, and IL-17+ cell counts in endobronchial biopsies. Correlations were made with infection status and other inflammatory markers. Potential cellular sources of IL-17 were determined by double staining.Measurements and Main Results: IL-17+ cell counts (median [interquartile range] cells/mm2) were significantly higher in patients with established CF (205 [115–551]) and non-CF bronchiectasis (245 [183–436]) than in control subjects (53 [12–82]) (P < 0.01 for both). Patients with newly diagnosed CF had intermediate counts (...