EOSINOPHIL APOPTOSIS AND THE RESOLUTION OF AIRWAY INFLAMMATION IN ASTHMA

Asthma is accompanied by the accumulation of potentially damaging eosi nophils within inflamed airways. How eosinophils may be removed from t he airways is not clear. The phagocytic removal of eosinophils in vitr o requires that they undergo apoptosis, a form of cell death. We postu lated that eosinophil apoptosis may occur in vivo, promoting the remov al of airway eosinophils and the resolution of inflammation in asthma. We examined eosinophil apoptosis in sputum samples obtained from 11 s ubjects during an asthma exacerbation and 2 wk after corticosteroid tr eatment of the exacerbation. Airway function improved following cortic osteroid treatment, and eosinophilic inflammation subsided, with signi ficant decreases occurring in the number of airway eosinophils and the percentage of activated eosinophils. The proportion of apoptotic airw ay eosinophils increased significantly following corticosteroid treatm ent, and eosinophil products were apparent within macrophages. Our fin dings indicate that eosinophil apoptosis is clinically relevant in ast hma. Apoptosis may represent a mechanism that promotes the resolution of eosinophilic inflammation in asthma.