Sputum inflammatory cells and allergen‐induced airway responses in allergic asthmatic subjects

To cite this article: Imaoka H, Gauvreau GM, Watson RM, Strinich T, Obminksi GL, Howie K, Killian KJ, O’Byrne PM. Sputum inflammatory cells and allergen‐induced airway responses in allergic asthmatic subjects. Allergy 2011; 66: 1075–1080. Background: Allergen inhalation causes early and late bronchoconstrictor responses, airway hyperresponsiveness and airway inflammation in allergic asthmatics. The role of airway inflammatory cells in causing allergen‐induced bronchoconstriction and airway hyperresponsiveness is controversial. The objective of this study was to examine the relationships between allergen‐induced increases in airway inflammatory cells, early and late bronchoconstrictor responses and methacholine airway hyperresponsiveness. Methods: Allergen inhalation challenge was conducted in 50 allergic asthmatics. Changes in the forced expired volume in 1 s (FEV1%) were followed for 7 h, induced sputum was obtained at 7 and 24 h, and the provocative concentration of methacholine causing a 20% fall in FEV1 (MCh PC20) was measured at 24 h. Results: There was a significant negative correlation between the baseline methacholine PC20 and baseline sputum eosinophils (r = −0.512, P = 0.0001). Allergen‐induced changes in methacholine PC20 were also significantly negatively correlated to allergen‐induced change in sputum eosinophils at 24 h (r = −0.434, P = 0.002), but not to changes in any other inflammatory cells. There were no significant correlations between sputum eosinophils or other inflammatory cells and the allergen‐induced early or late asthmatic responses. Conclusion: Allergen‐induced increases in airway eosinophils in asthmatic dual responders may contribute to allergen‐induced changes in methacholine PC20, but not the late asthmatic responses.