Neutrophil elastase activity on the surface of sputum neutrophils is associated with severity of airflow obstruction in cystic fibrosis

Introduction: Neutrophilic airway inflammation is a hallmark of cystic fibrosis (CF) and previous studies identified free neutrophil elastase (NE) in bronchoalveolar lavage fluid and sputum as a key risk factor of early bronchiectasis and decline in lung function. However, the relevance of membrane-associated NE activity in the pathophysiology of CF lung disease is not well understood. In this study, we used a ratiometric Foerster resonance energy transfer (FRET) reporter (NEmo-2) to determine NE activity on the surface of sputum neutrophils and correlated NE levels with measurements of pulmonary function. Metho…