Methods: Total 238 asthmatics (216 never smokers and 22 exsmoker less than 10 pack years) were enrolled and sputum was induced using isotonic saline containing a short-acting bronchodilator. Differential cell count was performed. The concentration of S100A9, IL-1b, -5, -8, -13, -17A, -32 and -33 was determined using ELISA, then normalized with total protein in supernatant of sputum. Statistical analyses, clustering and decision tree analysis were performed using SPSS 12.0.
Results: There were positive correlations between levels of S100A9 with those of IL-1b and IL-13, between IL-8 with IL13 and IL17A, between IL-17A with IL13, IL32 and IL33 and between IL-32 and IL-33 (p<0.05). The level of IL-13 was inversely correlated with IL-33. The subjects were clustered into four major groups according to the sputum level of cytokines; subjects with high level of IL-17A and IL-1b (group 1), with relatively low levels of cytokines with modest increase of IL-33 (group 2), with high IL-8 and IL-13 (group 3) and with highest S100A9 with moderate increase of IL-8 (group 4). The clinical features of the group 1 were younger, high airway hyperreactivity and increased numbers of WBC in blood. While group 2 showed highest % of eosinophils and low neutrophils in sputum, Group 3 showed highest % of neutrophils. Group 4 showed 2ndly highest % of neutrophils in sputum, old age, and relatively normal airway hyperreactivity. However, lung functions and exacerbation status were comparable between groups. In decision tree analysis for exacerbation, the patient were classified into three groups according to the level of cytokines; group 1 with lower IL-17A level (<=1.093 pg/ug), group 2 with higher IL-17A (>1.093 pg/ug) and low IL-32 (<=1.336 pg/ug) and IL-33 levels, and group 3 with higher IL-17A, IL-32 and IL-33 levels. The patient in group 1 was old-age and greatest pack years of smoking. They showed significantly higher serum level of total IgE, and neutrophil% in sputum than those of other groups. The lung function of the group was lowest in spite of treatment with highest dose of inhaled corticosteroid. Patients in group 3 showed significantly frequent exacerbation per year (P = 0.0001).
Conclusion: The level of IL-17A, IL-32 and IL-33 in sputum may be a surrogate set of markers for predicting treatment outcomes in asthmatics and an endotype for refractory asthma.