Enzyme-Linked Immunoassay for Human Granulocyte Elastase in Complex with α1 -Proteinase Inhibitor

Human polymorphonuclear neutrophilic leukocytes contain large amounts of neutral proteinases which are released when the granulocytes are exposed to a phagocytic stimulus. In inflammatory diseases local imbalance between these proteinases and available proteinase inhibitors may cause tissue injury as well as degradation of plasma proteins (1,2). Granulocyte elastase (E.C.3.4.21.11) is of special pathological interest because of its high concentration and its broad specificity for a variety of connective tissue components (i.e. elastin, collagen, proteoglycans) and plasma proteins (i.e. IgG, C3, C5, various clotting factors). Though it seems obvious that a quantitative determination of elastase in inflamed tissue and in the circulating blood may give information on disease activity, up to now there have been published only few reports on quantitative assays for the detection and quantitation of elastase in biological fluids (3–6). The main antagonizing agent in plasma for elastase is α1-proteinase inhibitor (7). Upon the interaction of elastase with the inhibitor a complex with a molar ratio of 1 to 1 and a molecular weight of approximately 80,000 Daltons is formed (7,8). We developed a solid-phase enzyme-linked immunoassay for the determination of the complex of elastase with α1-proteinase inhibitor (9,10). By using this assay remarkedly elevated levels of the complex were demonstrated in plasma samples of septicemic patients (11) and in synovial fluids of patients with rheumatoid arthritis (12,13).