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Autoantibodies to Proteinase 3 and Myeloperoxidase in Systemic Sclerosis
AMELIA RUFFATTI, RENATO ALBERTO SINICO, ANTONELLA RADICE, ELENA OSSI, FRANCO COZZI, MARTA TONELLO, PANAGIOTIS GRYPIOTIS, and SILVANO TODESCO
ABSTRACT.
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. Conclusion. 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. (J Rheumatol 2002;29:918-23) Key Indexing Terms:
ANTIBODIES TO PROTEINASE 3
From the Department of Medical and Surgical Sciences, Division of Rheumatology and I Chair of Internal Medicine, University of Padova, Padova; and the Renal Unit and Center of Clinical Immunology, San Carlo Borromeo Hospital, Milano, Italy. A. Ruffatti, MD, Assistant Professor of Rheumatology; R.A. Sinico, MD, Assistant Professor of Nephrology; A. Radice, PhD, Research Biologist; E. Ossi, MD, Associate Professor of Internal Medicine; F. Cozzi, MD, Assistant Professor of Rheumatology; M. Tonello, PhD, Research Biologist; P. Grypiotis, PhD, Research Fellow; S. Todesco, MD, Professor of Rheumatology. Address reprint requests to Dr. A. Ruffatti, Divisione di Reumatologia, Policlinico Universitario, Via Giustiniani 2, 35128 Padova, Italy. E-mail: amelia.ruffatti@unipd.it Submitted May 28, 2001; revision accepted November 30, 2001. |