Characteristics of Asthmatic Patients with IL18R1 Differential Expression in Induced Sputum

Introduction: Interleukin 18 receptor 1 (IL18R1) is involved in the pathogenesis of asthma and atopic phenotypes. However, IL18R1 expression level in induced sputum supernatant of asthma remains unclear. Methods: IL18R1, IL-4, IL-5, IL-13, IFN-r, and MUC5AC level in induced sputum supernatant was detected by ELISA in patients with asthma, and the correlation of IL18R1 expression with clinical parameters (FeNO, peripheral blood eosinophil count, serum IgE, and lung function), Th1 cytokine (IFN-r), T helper cell 2 (Th2) cytokine (IL-4, IL-5, and IL-13), and mucus (MUC5AC) were analyzed. Asthma subjects were categorized as IL18R1low and IL18R1high (below or above the upper quartile of the control group, respectively). Clinical features were compared between the IL18R1low and IL18R1high asthma subgroups. Subjects with asthma underwent a 4-week treatment with inhaled budesonide. Results: We found that IL18R1 level in induced sputum increased and was correlated with FeNO, peripheral blood eosinophil count, serum IgE, FEV1 (%predicted), FEV1/FVC%, and Th2 cytokine (IL-4, IL-5, and IL-13) in patients with asthma. IL18R1 expression was not correlated with Th1 cytokine IFN-r and MUC5AC in induced sputum. IL18R1high asthma had higher FeNO levels, higher peripheral blood eosinophil counts, lower FEV1/FVC%, and higher Th2 cytokine (IL-4, IL-5, and IL-13) expression than IL18R1low subgroup or controls. IL18R1high asthma had a significant decrease in FeNO and more improvement in FEV1 during inhaled corticosteroid (ICS) treatment compared with patients having the IL18R1low subgroup. Conclusions: IL18R1 level in induced sputum was increased. IL18R1low and IL18R1high asthma subgroups had different clinical features and responses to ICS treatment. IL18R1 level in induced sputum may be a novel marker of Th2-high asthma and has potential application in predicting treatment response.