title: Autoantibodies to proteinase 3 and myeloperoxidase in systemic sclerosis.
abstract: OBJECTIVE
  We evaluated the prevalence and clinical significance of proteinase 3 (PR3-) and myeloperoxidase (MPO-) antineutrophil cytoplasmic antibodies (ANCA) in 115 patients with systemic sclerosis (SSc, scleroderma).
  
  
  METHODS
  Sera were assayed by 2 independent centers, which used indirect immunofluorescence (IIF) and direct ELISA as screening tests. Inhibition-ELISA for PR3- and MPO-ANCA and PR3 capture-ELISA experiments were also performed. The clinical features of the ANCA positive were compared with those of the ANCA negative scleroderma patients.
  
  
  RESULTS
  The IIF test revealed 5 P-ANCA positive sera (4.34%). Surprisingly, by ELISA 2 of these were PR3-ANCA positive, one was MPO-ANCA positive, and 2 were both PR3- and MPO-ANCA positive. In addition, 3 IIF negative sera were ELISA positive, 2 for PR3- and one for MPO-ANCA. ELISA results were confirmed by fluid phase inhibition experiments. Only 2 out of the 6 PR3-direct ELISA positive sera were positive by PR3-capture ELISA at low titers. Neither PR3- nor MPO-ANCA were significantly associated to any clinical feature of patients with SSc.
  
  
  CONCLUSIONS
  As well as the previously described MPO-ANCA, even PR3-ANCA may be detected in some sera from patients with SSc. The IIF pattern and the negative results obtained with PR3-capture ELISA suggest that different epitopes from those recognized by vasculitis sera might be involved with PR3-ANCA in SSc, and show the importance of combining IIF and ELISA tests for ANCA detection.
authors.affiliation: Department of Medical and Surgical Sciences, University of Padova, Italy. amelia.ruffatti@unipd.it
authors.forename: Amelia
authors.initials: A
authors.lastname: Ruffatti
authors.forename: Renato Alberto
authors.initials: RA
authors.lastname: Sinico
authors.forename: Antonella
authors.initials: A
authors.lastname: Radice
authors.forename: Elena
authors.initials: E
authors.lastname: Ossi
authors.forename: Franco
authors.initials: F
authors.lastname: Cozzi
authors.forename: Marta
authors.initials: M
authors.lastname: Tonello
authors.forename: Panagiotis
authors.initials: P
authors.lastname: Grypiotis
authors.forename: Silvano
authors.initials: S
authors.lastname: Todesco
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood; D000918:Antibody Specificity; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes / Q000276:immunology; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D008297:Male; D008875:Middle Aged; D053146:Myeloblastin; D009195:Peroxidase / Q000276:immunology*; D012595:Scleroderma, Systemic / Q000453:epidemiology / Q000276:immunology*; D012697:Serine Endopeptidases / Q000276:immunology*; D016036:Seroepidemiologic Studies
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D000939:Epitopes; D009195:Peroxidase; D012697:Serine Endopeptidases; D053146:Myeloblastin