BACKGROUND:Airway eosinophilia is frequently observed during acute exacerbation of asthma. Interleukin-5 (IL-5) and eotaxin are directly involved in the airway eosinophilia found in persistent asthma. Interrelation between these cytokines is expected to occur in acute exacerbation of asthma. Thus, we evaluated the relevance of interaction between eotaxin and IL-5 in the airway inflammation of acute exacerbation. METHODS:We measured the number of inflammatory cells and the amount of eotaxin and IL-5 in sputum from 22 healthy subjects, 21 asthmatics with acute exacerbation and 16 patients with mild persistent asthma, and reassessed these values in 7 subjects with acute exacerbation after 7 days' treatment with systemic steroid (2 mg/kg/day). Sources of IL-5 and eotaxin were investigated by immunohistochemical staining of sputum cells of 4 cases from each group. RESULTS:Both IL-5 and eotaxin levels were higher in patients with acute exacerbation of asthma than in patients with persistent asthma and normal subjects. IL-5 and eotaxin levels were significantly correlated with eosinophil percentages in mild persistent asthma. Eotaxin staining was found mainly on macrophages and occasionally on eosinophils. Steroid treatment markedly decreased eosinophil percentages and IL-5 levels within 7 days but did not alter eotaxin levels. CONCLUSIONS:Both IL-5 and eotaxin are associated with acute exacerbation of asthma. IL-5 rather than eotaxin is effectively decreased by the inhibitory effect of steroid in acute exacerbation.