Determination of proteinase 3—α1-antitrypsin complexes in inflammatory fluids

Physiological inhibitors were tested for their in vitro interaction with neutrophil proteinase 3 (PR3). The major plasma proteinase inhibitor of PR3 is α1AT. We have developed a radioimmunoassay (RIA) for quantitative detection of PR3—α1AT complexes formed in vivo in inflammatory exudates such as synovial fluid and plasma from patients with sepsis. Levels of PR3—α1AT complexes correlated significantly with levels of human neutrophil elastase (HNE)—α1AT complexes. Thus, in vivo α1AT not only protects against excessive HNE activity, but also against excessive PR3 activity.