Alpha-1-proteinase inhibitor in inflammatory states of humans and laboratory animals.

Alpha-1-proteinase inhibitor (A1PI) was examined in various inflammatory conditions in terms of its capacity to inhibit leukocytic proteases and to act as a monitor of the presence of oxidants generated by stimulated leukocytes. Examination of bronchoalveolar lavage fluid from patients with pulmonary inflammatory disease indicated that oxidants are generated in situ in the inflammatory reaction of the lung; the oxidants could potentially injure tissue directly, and, by virtue of the inactivation of A1PI, prevent inhibition of the neutrophil elastase, potentially allowing unencumbered proteolytic attack of the neutrophil elastase on lung structures. Subsequent examination of leukocytic enzymes and oxidants in experimental pulmonary inflammation in animals also demonstrated the generation of oxidants during development of acute pulmonary inflammation and indicated that the neutrophil is the cell mainly responsible for the release of oxidants.