Alpha-1-Antitrypsin-Human Leukocyte Elastase Complexes in Blood: Quantification by an Enzyme-Linked Differential Antibody Immunosorbent Assay and Comparison With Alpha-2-Plasmin Inhibitor-Plasmin Complexes

An enzyme-linked immunosorbent assay (ELISA) has been developed for the quantification of cr,-antitrypsin-human leukocyte elastase (a,AT-E) complexes. In the ELISA, the a,AT-E complex is bound to a surface by rabbit antileuko-cyte elastase antibody, and the inhibitor-proteinase corn-plex is quantified by a second antibody, rabbit anti-a1-antitrypsin F(ab’)2. labeled with alkaline phosphatase. a1AT-E complexes were detected when a final concentra-tion of 2.2 nrnole/liter of leukocyte elastase was added to plasma. The concentration of these complexes increased with additional elastase. In clotting blood, a1AT-E corn-plexes were generated in parallel with the conversion of ‘251-flbrinogen to fibrin, whereas a2-plasmin inhibitor-plas-mm (a2Pl-P) complexes were not formed. The concentra-T HE RESPONSE of blood or of other tissues to injury frequently involves the activation of pro-tein-cleaving enzymes. ’ The direct measurement of the activity of these proteinases in blood currently is not feasible because these enzymes rapidly become bound to cell surfaces or to plasma proteinase inhibitors. Recently, a methodology was developed for the detec-tion and quantification of a2-plasmin inhibitor-plas-mm and a2-macroglobulin-plasmin complexes in pun-fled systems as well as in the plasma of patients with disseminated intravascular coagulation.2 This tech-nique employs an enzyme-linked immunosorbent assay utilizing two different antibodies to specifically recog-nize both the pnoteinase inhibitor and the proteinase within the inhibitor-enzyme complex. In the present study, this method has been applied to the quantification of ct,-antitrypsin-human leukocyte elastase complexes. Human polymorphonuclean leuko