Decreased interleukin-18 response in asthmatic children with severe Mycoplasma pneumoniae pneumonia

PURPOSE: Mycoplasma pneumoniae (M. pneumoniae) is a common causative agent of pneumonia in children. The aim of this study is to determine whether there is any difference in selected cytokine or chemokines response in asthmatic children compared to non-asthmatic children during acute M. pneumoniae pneumonia. METHODS: Seventy-five children, 6–12 years of age, admitted with M. pneumoniae pneumonia were enrolled. Two patient groups were defined: the children with known asthma (N = 40) and non-asthmatic children (N = 35). Interleukin (IL)-18 and selected chemokines, IL-8, CXCL9, CXCL10, and regulation upon activation normal T-cell expressed and secreted (RANTES) were measured by means of ELISA in the plasma samples of the patients collected on admission. We investigated the values of these mediators in relation to the asthma status and symptom severity of the patients. Twenty age-matched, non-infected controls were also studied. RESULTS: Plasma levels of IL-18 and the chemokines increased significantly in the patients with M. pneumoniae pneumonia compared to non-infected, age-matched controls (P < 0.01). However, the asthmatic patients showed significantly reduced IL-18 and CXCL10 responses (P < 0.01, <0.05, respectively) and had more severe pneumonia symptoms (P < 0.01) compared to non-asthmatic patients. IL-18 was significantly lower in severe pneumonia group than in non-severe group (P < 0.05). CONCLUSIONS: Our study suggests that IL-18 and the chemokines are importantly involved in the pathogenesis of M. pneumoniae pneumonia. It also indicates that some asthmatic children have deficient IL-18 response when affected by M. pneumoniae pneumonia, which might be associated with more severe pneumonia observed in this group of patients.