Isolation of a protein complex from purulent sputum consisting of proteinase-3 and alpha 1-antitrypsin reactive with anti neutrophil cytoplasmic antibodies.

The detection of ANCA (anti-neutrophil cytoplasmic antibodies) is of importance in the diagnosis of Wegener's granulomatosis (WG) and solid-phase assays for the detection of c-ANCA have been set up by various groups, using purified proteinase-3 (PR-3) in an ELISA or RIA. For the isolation of PR-3 large numbers of PMNs are needed. We therefore examined the possibility of isolating PR-3 from the purulent sputum of patients with chronic bronchitis or cystic fibrosis, since large numbers of PMNs and their degranulation products are present in such material. By a three-step chromatographic procedure (4-phenylbutylamine affinity chromatography, Biorex 70 cation exchange chromatography and monoclonal antibody anti-PR-3 affinity chromatography) we isolated a 53 kDa protein that was recognized on immunoblot by MoAbs directed against PR-3 and alpha 1-antitrypsin (alpha 1AT). We show that the 53 kDa protein is a complex of PR-3 and alpha 1AT. This complex is reactive with a selected set of c-ANCA positive sera from patients with Wegener's granulomatosis.