Background: Interleukin (IL)-17A is a highly inflammatory cytokine with a robust effect on stromal cells in many tissues. Although IL-17A is known to be associated with inflammatory lung disorders by triggering an accumulation of neutrophils, the effect of IL-17A on the upper airway is still uncertain. The expression of IL-17A and its role were investigated in the nasal polyps of chronic rhinosinusitis associated with asthma. Methods: IL-17A was detected by immunohistochemistry and quantitative real-time RT-PCR. The cellular source of IL-17A was examined by double staining with EG2, CD4 and neutrophil elastase. The tissue remodeling of the nasal polyps was evaluated by assessing the epithelial damage and basement membrane thickness. Results: Both the immunoreactivity and mRNA of IL-17A were significantly detected in the nasal polyps in comparison with control normal sinus mucosa. The localization of IL-17A expression predominantly coincided with eosinophils and CD4-positive lymphocytes. Furthermore, the number of IL-17A-positive cells correlated with tissue eosinophils, but not with neutrophils. The degree of epithelial damage and basement membrane thickness was dependent on the number of infiltrated IL-17A-positive cells. Conclusion: The present study suggests, for the first time, that IL-17A plays an important role in the eosinophil accumulation in the nasal polyps and the remodeling of the nasal polyps of chronic rhinosinusitis associated with asthma.

Objectives The link between nasal and bronchial disease has been studied extensively for chronic rhinosinusitis and asthma. The concept of “united airway allergy” has become widely accepted in the past decade. We evaluated the relationship between the upper and lower airways during follow-up after endoscopic sinus surgery by monitoring sinonasal and pulmonary functions. Methods Thirty-nine subjects with chronic rhinosinusitis associated with bronchial asthma were entered in this study. A self smell test using stick-type odorant materials was carried out daily to evaluate postoperative recurrence of sinonasal disease. Each patient was assessed for peak expiratory flow (PEF) 3 times daily. Results The average (±SD) scores of initial symptoms were 8.3 ± 2.2, which was significantly decreased to 1.5 ± 1.4 by 3 months after operation. During postoperative follow-up, 25 of 39 patients showed no decrease in PEF, whereas the other 14 patients had at least 1 episode of a significant decline in PEF. In the postoperative course, with respect to the self smell test, 24 patients showed no aggravation of smell, but 15 patients had episode(s) of decreased olfaction. Twelve patients demonstrated worsening on the smell test concomitant with a decreased PEF. A discrepancy between olfactory acuity and pulmonary function was recognized in 5 patients. There were 22 patients with a good prognosis of parameters of both the upper and lower airways. Conclusions Daily monitoring of both upper and lower respiratory tract functions clearly revealed dual relationships, indicating that worsening of sinusitis accompanies asthma exacerbation. Appropriate measures of the upper and lower airways following endoscopic sinus surgery can be used to predict patient outcome.