Induced sputum levels of soluble receptor ST-2 in adult patients suffering from allergic asthma or allergic rhinitis

Abstract

Background The epithelial-produced cytokine IL-33 is now recognized as an important contributor to Th2 type inflammation. The soluble form of its specific ligand, the receptor ST-2 (sST-2) has been reported to act as a negative regulator of Th2 cytokine production by the IL-33 signaling. Increased sST-2 levels have been documented in supernatants of induced sputum (IS) collected from asthmatic children. Aim This study aimed to detect the presence of sST2 in induced sputa from an adult population suffering from asthma or allergic rhinitis in comparison to healthy controls. Methods sST2 levels were measured by ELISA (Quantikine®, RD 15 with uncontrolled and 10 with controlled asthma as defined by GINA guidelines) or seasonal allergic rhinitis (n=7) and compared to sST2 levels from healthy controls (n=7). Results IS sST2 levels were higher in asthmatics (22 pg/ml, p=0.004 in controlled asthma, 49 pg/ml, p=0.013 in uncontrolled asthma) compared to healthy controls ( Conclusion This study shows that sST-2 can be detected in IS of most adult asthma patients, regardless of the level of asthma control, but not in IS from subjects suffering from allergic rhinitis or in IS from healthy controls. This suggests that the epithelium-derived IL-33 signaling pathway is not (or less) activated in Th2 disease not associated with asthma (i.e. allergic rhinitis). The trend towards higher IS sST-2 levels in uncontrolled asthma patients suggests that the negative regulation of IL-33-derived Th2 inflammation is further activated when asthma control worsens.