Eotaxin Level in Induced Sputum Is Increased in Patients with Bronchial Asthma and in Smokers

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Abstract
Background: Airway eosinophilia is one of the hallmarks of asthma. Eotaxin may play an important role in eosinophil recruitment. Objectives: To examine the relationship between eotaxin levels in the sputum and eosinophilic inflammation. Methods: The sputum was obtained from 11 non-smokers, 14 smokers and 13 asthmatic patients using a sputum induction method. Eotaxin and interleukin (IL)-5 levels in the sputum were determined by ELISA and immunocytochemical analysis. Results: Asthmatic patients had eosinophilia and smokers showed neutrophilia in their sputum. The eotaxin level in the sputum was significantly higher in smokers (median 412.5, range 91.1–872.2 pg/ml) and asthmatic patients (351.0, 185.0–928.0 pg/ml) compared with non-smokers (123.2, 0–369.0 pg/ml; both p < 0.05). IL-5 was detected in the sputum of 1 non-smoker, none of the smokers and 4 asthmatic patients. The percentage of eotaxin-positive cells was higher in smokers and asthmatic patients than in non-smokers, but the percentage of IL-5-positive cells was significantly higher only in asthmatic patients (p < 0.05). Conclusions: These findings suggest that the elevated eotaxin level in the sputum does not always accompany the increase in eosinophils, and cooperation with another cytokine such as IL-5 may be required for the recruitment of eosinophils.

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