The concentration of leukocyte elastase-alpha 1-proteinase inhibitor complex in bronchoalveolar lavage fluids from healthy human subjects.

Although alpha 1-proteinase inhibitor (alpha 1-antitrypsin) is widely thought to protect lung elastin against the elastolytic action of leukocyte elastase, there is only circumstantial evidence for such a protective role. We have demonstrated and quantified elastase-alpha 1-proteinase inhibitor complex in bronchoalveolar lavage fluids from healthy smokers and nonsmokers using a new enzyme-linked immunosorbent assay. The relative concentration of complex is 0.36 +/- 0.48 mmol/mol albumin in nonsmokers and 0.33 +/- 0.29 mmol/mol albumin in smokers. Less than 1% of lavage fluid alpha 1-proteinase inhibitor is complexed with elastase (0.31% in nonsmokers and 0.34% in smokers). This proportion is, however, much higher than in normal plasma where only approximately 0.006% of inhibitor is bound to elastase. Our data confirm that alpha 1-proteinase inhibitor efficiently acts as an antielastase barrier in the lower respiratory tract.