Abstract
Leukocyte elastase and .alpha.1-antitrypsin are implicated in the pathogenesis of pulmonary emphysema. The relationship between these proteins was studied qualitatively and quantitatively in sputum from 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 .alpha.1-antitrypsin concentrations increased, although the enzyme was only partially inactivated. The proportion of .alpha.1-antitrypsin present as complex was smaller in the presence of infection, suggesting damage to the protein by excess enzyme.