Induced sputum levels of IL-33 and soluble ST2 in young asthmatic children

Objective: Interleukin-33 is an IL-1 family cytokine which signals via its T1/ST2 receptor, and acts as a key regulator of inflammation, notably the type-2 response implicated in asthma. This study aims to measure the expression of soluble ST2 (sST2) and IL-33 in asthmatic children, depending on disease activity. Methods: Thirty-seven children with well-defined asthma (20 moderate and 17 mild asthmatics) were studied. IL-33 and sST2 were measured by ELISA in serum and induced sputum (IS) samples, and compared with 22 age-and sex-matched healthy controls. Real-time quantitative PCR was used to determine IL-33 and TNF-alpha mRNA expression in IS. Results: sST2 and IL-33 levels in IS and serum were significantly higher in patients compared with healthy controls (p = 0.0001). The increase in sST2 and IL33 was significantly more important in moderate cases than in mild asthma. A significant correlation was observed between serum and IS IL-33 levels (r = 0.497; p = 0.0018). Higher levels of IL-33 mRNA were detected in IS from asthmatics than those observed in controls. A significant correlation was found between TNF-alpha and IL-33 mRNA expression in the asthmatic subjects (r = 0.772, p = 0.0001). Conclusions: Values of sST2 and IL-33 observed in IS were found to correlate with disease activity. Elevated IL-33 mRNA expression in IS and its correlation with TNF-alpha reflected the inflammatory process observed in the lung of young asthmatics.