The Electrophoretic Mobility of α1-Antitrypsin in Sputum and Its Relationship to Protease Inhibitory Capacity, Leucocyte Elastase Concentrations and Acute Respiratory Infection

Abstract

The electrophoretic mobility of uncomplexed .alpha.1-antitrypsin was studied in the sol phase of sputum from 14 patients with chronic bronchitis. The mobility of .alpha.1-antitrypsin in the sputum of each subject was reduced compared to the mobility in serum (mean sputum value = 71.1% of albumin mobility; mean serum value = 78.5% of albumin mobility). This reduction in .alpha.1-antitrypsin mobility was most significant in the sputum samples of patients with chest infections which contained free elastolytic activity (mean value in cases where no enzyme activity was found, 74.9%; in cases with enzyme activity, 66.1%, 2P < 0.01). There was a significant inverse relationship between .alpha.1-antitrypsin mobility in sputum and concentration of immunoreactive leukocyte elastase (r = -0.739, 2P < 0.01). The addition of trypsin (EC 3.4.21.4) to the sputum samples did not inhibit the enzyme despite the apparent presence of sufficient uncomplexed .alpha.1-antitrypsin in these samples, suggesting that this .alpha.1-antitrypsin was non-functional. Proteolytic enzymes can inactivate .alpha.1 antitrypsin with a reduction in its electrophoretic mobility. The .alpha.1-antitrypsin in sputum may be inactivated by lysosomal proteases including elastase.