Alpha1-Antitrypsin and Leukocyte Elastase in Infected and Noninfected Sputum1–3

Leukocyte elastase and alpha1-antitrypsin have been implicated in the pathogenesis of pulmonary emphysema. The relationship between these proteins has been studied in sputum both qualitatively and quantitatively in bronchitic patients with and without chest infections. Leukocyte elastase was found in 75 % of the noninfected samples but was enzymatically inactive, suggesting complete inhibition. During infection, leukocyte elastase and alpha1-antitrypsin concentrations increased, although the enzyme was only partially inactivated. The proportion of alpha1-antitrypsin present as “complex” was smaller in the presence of infection, suggesting damage of the protein by excess enzyme.