Methods: Hypertonic saline induced sputum was obtained from asthma in stable state (n=143) and in exacerbated state (n=48). Differential cell count of induced sputum was done. IL-1β was measured using sandwich ELISA in induced sputum. The levels were analyzed in terms of airway obstruction (FEV1%) and inflammation (neutrophil % and eosinophil % of induced sputum) and exacerbation frequency and lung function over 1 year or longer follow up.
Results: IL-1β levels were significantly correlated with the neutrophil cell counts of induced sputum (r=0.186, p=0.010), but not with initial FEV1% in total asthmatics (p>0.05). The correlations of IL-1β levels with neutrophil % (r=0.188, p=0.025) and eosinophil % (r=-0.178, p=0.033) were observed in stable asthmatics. In the exacerbation group, IL-1β levels were inversely correlated with FEV1% (r=-0.326, p=0.024). In long term follow up of stable asthmatics (n=71) over more than 1 year, IL-1β levels were correlated with the follow up FEV1/FVC (r=-0.318 p=0.007). Annual average exacerbation rate was also well correlated with the IL-1β levels in the subjects with neutrophilic inflammation (>70%) in sputum.
Conclusion: Sputum IL-1β may be related with neutrophilc inflammation. In exacerbated state and long - term follow up of asthma, sputum IL-1β may also be related with the extent of airway obstruction. These data suggest the IL-1β may participate to airway obsturction and exacerbation frequecy, especially in neutrophilic inflammation.