Expression of eotaxin in induced sputum of atopic and nonatopic asthmatics

Background: The chemokine eotaxin has been implicated in airway eosinophili a in atopic asthma. We have compared airway eosinophils and eotaxin express ion in induced sputum from well-matched atopic and nonatopic asthmatics. Methods: Eosinophil numbers, eosinophil cationic protein (ECP), and the exp ression of eotaxin were examined in induced sputum from atopic asthmatics ( AA = 11), nonatopic asthmatics (NAA = 11), and atopic (AC = 12) and normal (NC = 10) controls. Slides were prepared for differential cell counts by Ro manowsky stain, and ECP levels were measured by RIA. Eotaxin expression was detected by in situ hybridization, with S-35-labelled riboprobes and immun ocytochemistry. Results: The numbers of eosinophils and ECP concentration were increased in the sputum of AA and NAA compared with AC and NC (P < 0.05). The numbers o f eotaxin mRNA (+) and immunoreactive cells were increased in NAA, but not AA, when compared with controls (P < 0.05). Eotaxin immunoreactive cells in NAA were significantly higher than in AA (P < 0.05). Eotaxin was expressed predominantly by macrophages, eosinophils, and epithelial cells. In NAA, b ut not AA, the numbers of eotaxin mRNA (+) cells were correlated with hista mine PC20 (r = -0.81, P < 0.01) and eosinophil numbers in sputum (r = 0.7, P < 0.05). Conclusions: Eotaxin production by macrophages, eosinophils, and epithelial cells may play a more pronounced role in airway eosinophilia in nonatopic than in atopic asthma.