Antineutrophil elastase activity in cystic fibrosis serum.

The antigenic concentrations of alpha-1-antitrypsin (alpha 1AT) were measured in 13 patients with cystic fibrosis (CF) and in 11 healthy subjects. Serum alpha 1AT was purified by immunoaffinity chromatography and the antielastase activity of the purified alpha 1AT was determined by measuring the molar ratio necessary to inhibit human neutrophil elastase (HNE). The association rate constant of alpha 1AT with HNE was determined in a timed assay. The capacity of CF serum alpha 1AT to form complexes with porcine pancreatic elastase was studied by polyacrylamide gel electrophoresis. Antigenic concentrations of alpha 1AT mumol/L were markedly increased in the serum of all patients with CF (61.9 +/- 4.3 mumol/L) in comparison to a reference standard (36.7 +/- 1.8 mumol/L; P less than 0.0001). CF serum alpha 1AT was fully active against HNE, and its association rate constant in the presence of HNE was similar to that of healthy subjects. In addition, CF serum alpha 1AT formed complexes with porcine pancreatic elastase that were electrophoretically indistinguishable from those of normal serum alpha 1AT. These results indicate that patients with CF have increased serum alpha 1AT concentrations and that this antiprotease, when purified from serum, functions normally.