Granular Insights: Neutrophil Predominance and Elastase Release in Severe Asthma Exacerbations in a Pediatric Cohort

Abstract

The chronic inflammatory component of asthma is propagated by granulocytes, including neutrophils and eosinophils, in the peripheral circulation and airway. Previous studies have suggested that these cells have an altered expression of adhesion-related molecules and a propensity for the release of granule contents that may contribute to tissue damage and enhance inflammatory complications in patients with status asthmaticus. The goal of this prospective cohort study at a tertiary care pediatric hospital with a large population of asthma patients was to assess the role of granulocyte-based inflammation in the development of asthma exacerbation. Subjects were enrolled from two patient populations: those with mild-to-moderate asthma exacerbations seen in the emergency department and those with severe asthma admitted to the intensive care unit (PICU). Clinical data were collected, and blood was drawn. Granulocytes were immediately purified, and the phenotype was assessed, including the expression of cell surface markers, elastase release, and cytokine production. Severe asthmatics admitted to the PICU displayed a significantly higher total neutrophil count when compared with healthy donors. Moreover, little to no eosinophils were found in granulocyte preparations from severe asthmatics. Circulating neutrophils from severe asthmatics admitted to the PICU displayed significantly increased elastase release ex vivo when compared with the PMN from healthy donors. These data suggest that the neutrophil-based activation and release of inflammatory products displayed by severe asthmatics may contribute to the propagation of asthma exacerbations.