Autoantibodies in Juvenile Idiopathic Arthritis: Glucose-6-Phosphate Isomerase Is Not a Specific Target

CARSTEN P. SCHEPP, LUCIANA DANNECKER, MARKUS HAUG, JASMIN KÜMMERLE-DESCHNER, HERMANN BECK, INA KÖTTER, URSULA HOLZER, and GUENTHER E. DANNECKER

ABSTRACT.

Objective. Antibodies recognizing the ubiquitous cytosolic enzyme glucose-6-phosphate isomerase (GPI) cause arthritis in the K/BxN mouse model. Studies have shown that these antibodies are not specific for rheumatoid arthritis (RA) in humans. We evaluated GPI as a target of autoantibodies in juvenile idiopathic arthritis (JIA).

Methods. We studied 324 serum and 48 synovial fluid (SF) samples from 103 patients with JIA, 36 with RA, and 8 with arthralgia and 11 controls. Anti-GPI antibodies were assessed by densitometrically evaluating immunoblots and ELISA using native and recombinant GPI. We determined the GPI activity of the soluble antigen in serum and SF.

Results. Although several samples contained anti-GPI-IgG antibodies, this was not specific for JIA or its subgroups, or for RA. Other proteins in the GPI preparation were also frequently recognized by antibodies. Additionally, we observed increased GPI activity in patients with the systemic manifestation of JIA, but not in other patients. Neither anti-GPI concentrations nor GPI activity were associated with disease activity.

Conclusion. In addition to the findings in RA, our results indicate that GPI is not a general target of autoantibodies in JIA. (J Rheumatol 2004;31:1630-8)

Key Indexing Terms:

JUVENILE IDIOPATHIC ARTHRITIS
GLUCOSE-6-PHOSPHATE ISOMERASE
AUTOIMMUNITY
AUTOANTIBODIES

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From the University Children's Hospital, Eberhard Karls University, Tuebingen; Department of Internal Medicine II, University Hospital, Eberhard Karls University, Tuebingen; Department of Nephrology and Rheumatology, Georg-August-University, Goettingen; and the Department of Pediatrics, Olgahospital, Stuttgart, Germany.

Supported by a grant from the Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 510).

C.P. Schepp, Biochemist; L. Dannecker, Technical Assistant; M. Haug, Pharmacist; J. Kümmerle-Deschner, MD, Pediatric Rheumatologist; U. Holzer, MD, Pediatric Rheumatologist, University Children's Hospital; G.E. Dannecker, MD, Professor of Pediatrics, University Children's Hospital, current address: Olgahospital, Department of Pediatrics, Stuttgart, Germany; H. Beck, PhD, Research Assistant, Department of Nephrology and Rheumatology, Georg-August-University, current address: F. Hoffmann-La Roche Ltd., Basel, Switzerland; I. Kötter, MD, Rheumatologist, Department of Internal Medicine II, University Hospital, Eberhard Karls University.

Address reprint requests to Dr. G.E. Dannecker, Department of Pediatrics I, Olgahospital, Bismarckstrasse 8, 70176 Stuttgart, Germany. E-mail: g.dannecker@olgahospital.de

Submitted October 29, 2003; revision accepted January 15, 2004.

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