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

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 (FEV 1%) 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 FEV 1 (MCh PC 20) was measured at 24 h. Results: There was a significant negative correlation between the baseline methacholine PC 20 and baseline sputum eosinophils (r = -0.512, P = 0.0001). Allergen-induced changes in methacholine PC 20 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 PC 20, but not the late asthmatic responses. © 2011 John Wiley & Sons A/S.