Background: Severe asthma represents a heterogeneous group of patients whose characteristics of airway inflammation are poorly known.
Objective: To evaluate the sputum cytokine profiles of different phenotypes of severe asthma.
Methods: Severe asthmatic patients (n = 45) were divided into 3 groups: frequent exacerbations, persistent bronchoconstriction, and both features. Two other groups (9 patients with untreated mild asthma and 10 control subjects) were also studied. Selected sputum portions were assayed for differential cell count, supernatant interleukin 5 (IL-5), granulocyte-macrophage colony-stimulating factor, IL-8, and eosinophil cationic protein.
Results: There were no statistically significant differences among the 3 severe asthma groups in terms of sputum inflammatory cell percentages, IL-8 levels, and eosinophil cationic protein levels, although IL-8 levels tended to be higher in patients with persistent bronchoconstriction. Sputum concentrations of granulocyte-macrophage colony-stimulating factor and IL-5 were significantly higher in patients with frequent exacerbations compared with the other 2 groups. Levels of IL-5 and IL-8 were higher in severe asthmatic patients compared with mild asthmatic patients and controls, whereas sputum eosinophil percentages were intermediate between those of mild asthmatic patients and controls.
Conclusions: Proeosinophilic cytokine levels are increased in severe asthmatic patients with frequent exacerbations but not in severe asthmatic patients with persistent bronchoconstriction, suggesting that different cytokine profiles could be associated with different phenotypes of severe asthma.