title: Inhibition of proteinase 3 by ANCA and its correlation with disease activity in Wegener's granulomatosis.
abstract: Detection of circulating antineutrophil cytoplasmic antibodies (ANCA) to the neutrophil serine proteinase, proteinase 3 (PR3), has proven valuable for the diagnosis of Wegener's granulomatosis (WG). However, the importance of these autoantibodies in the pathogenesis of WG remains unknown. It was recently reported that anti-PR3 autoantibodies (PR3-ANCA) from some patients with WG inhibit the proteolytic activity of PR3 and interfere with the inactivation of PR3 by the physiologic inhibitor, alpha 1-proteinase inhibitor (alpha 1-PI). We have studied the effect of PR3-ANCA on the enzymatic activity of PR3 and its correlation with disease activity in patients with WG. We purified IgG from 21 PR3-ANCA positive sera obtained from 17 patients with WG, and determined its effect on the esterolytic and proteolytic activity of purified human PR3 using Boc-Ala-O-Nitrophenyl ester and fluoresceinated-elastin as enzyme substrates. Controls included seven sera containing anti-MPO autoantibodies (MPO-ANCA) from patients with systemic vasculitis and seven ANCA-negative sera obtained from healthy individuals. We found that PR3-ANCA from 9 of the 17 patients significantly inhibited the activity of PR3. There was no correlation between the titers of PR3-ANCA and their inhibitory activity. For one extensively characterized autoantibody, the inhibition reached 70 to 95% at 20-fold molar excess of IgG to enzyme, with an apparent Kiapp of 56.5 microM. This inhibition was non-competitive in nature, and was additive to that produced by alpha 1-PI. A review of the clinical histories of the patients revealed a strong association between active WG and inhibitory autoantibodies.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Leukocyte Biology and Inflammation Program, Massachusetts General Hospital, Charlestown, USA.
authors.forename: G H
authors.initials: GH
authors.lastname: Daouk
authors.forename: R
authors.initials: R
authors.lastname: Palsson
authors.forename: M A
authors.initials: MA
authors.lastname: Arnaout
mesh_terms: D019268:Antibodies, Antineutrophil Cytoplasmic; D001323:Autoantibodies / Q000276:immunology*; D004549:Elastin / Q000378:metabolism; D004952:Esters / Q000378:metabolism; D005260:Female; D014890:Granulomatosis with Polyangiitis / Q000276:immunology / Q000503:physiopathology*; D006706:Homeostasis; D006801:Humans; D007700:Kinetics; D008297:Male; D053146:Myeloblastin; D012697:Serine Endopeptidases / Q000276:immunology* / Q000378:metabolism; D000515:alpha 1-Antitrypsin / Q000494:pharmacology
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D001323:Autoantibodies; D004952:Esters; D000515:alpha 1-Antitrypsin; D004549:Elastin; D012697:Serine Endopeptidases; D053146:Myeloblastin