Increases in eotaxin-positive cells in induced sputum from atopic asthmatic subjects after inhalational allergen challenge

Background: Eosinophils are believed to be critical proinflammatory cells i n airway mucosal damage in asthma. Eotaxin is a C-C chemokine with selectiv e activity for eosinophils and basophils. Previous studies have shown incre ased expression of eotaxin in the airways of asthmatics at baseline. We aim ed to investigate eotaxin expression during the late-phase reaction to alle rgen inhalation in atopic asthmatics. Methods: Sputum induction was performed before and 24h after inhalational a llergen challenge in atopic asthmatics, and eotaxin protein was detected im munocytochemically. Results: Thirteen patients with a mean decrease in forced expiratory Volume in 1s of 28% (+/-1.5) during the early asthmatic reaction, and 39% (+/-4.7 ) during the late asthmatic reaction produced sufficient sputum for study. The percentage of eosinophils in sputum was increased 24h after allergen ch allenge (P<0.004), and eosinophil percentages in sputum after challenge cor related with the magnitude of the late-phase reaction (r=0.56, P=0.05). The percentage of eotaxin-positive cells increased from 12.6% (range 2-43.8) t o 24.3% (8.1-47.1, P<0.005). Allergen-induced increases in eotaxin-positive cells correlated with increases in eosinophils (r=0.63, P<0.01). Conclusions: These findings suggest that eotaxin may contribute to allergen -induced recruitment of eosinophils to the airway in asthmatic subjects.