Sputum Interleukin-32 in childhood asthma: correlation with IL-1β

Abstract

_Background:_ Asthma is an airway disorder where inflammatory cytokines are partly responsible for exacerbating the disease. Interleukin (IL)-32, generally referred to as natural killer cell (NK4) transcript 4, is described as an immunoregulator involved in the stimulation of anti-/pro-inflammatory cytokines. The abnormal presence of IL-32 has been observed during inflammatory diseases, particularly in asthma. This study aims to characterize IL-32 in the inflammatory process in patients with severe asthma. _Methods:_ IL-32 and IL-1β levels in the supernatant of induced sputum obtained from 59 asthma patients (mild: 20 patients; moderate: 20 patients; severe: 19 patients) were measured using ELISA. Sputum IL-32 mRNA expression was measured by RT- PCR. _Results:_ Sputum IL-32 was significantly elevated at the protein (_p= 0.00019_) and mRNA expression (_p < 0.0001_) in asthmatics compared to non-asthmatic controls. IL-32 was elevated in severe asthmatic patients (_p < 0.0001_) compared to mild-moderate asthma. Severe asthmatics allergic to house dust mites expressed higher sputum IL-32 levels than severe asthmatics without allergy (_p = 0.0001_). A significant association was found between sputum IL-32 and IL-32 mRNA (r =0.531_; p = 0.0159_) in severe asthma. In the same way, sputum IL-1β and IL-32 were significantly correlated (r = 0.476; _p = 0.0337_). _Conclusion:_ The level of IL-32 in induced sputum may be associated with asthma severity.