Autoantibodies in juvenile idiopathic arthritis: glucose-6-phosphate isomerase is not a specific target.
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.


CONCLUSIONS
In addition to the findings in RA, our results indicate that GPI is not a general target of autoantibodies in JIA.
Schepp
Carsten P
CP
University Children's Hospital, Eberhard Karls University, Tuebingen, Germany.
Dannecker
Luciana
L
Haug
Markus
M
Kümmerle-Deschner
Jasmin
J
Beck
Hermann
H
Kötter
Ina
I
Holzer
Ursula
U
Dannecker
Guenther E
GE
D000293:Adolescent; D018771:Arthralgia / Q000276:immunology; D001171:Arthritis, Juvenile / Q000097:blood / Q000276:immunology* / Q000503:physiopathology; D001172:Arthritis, Rheumatoid / Q000276:immunology; D001323:Autoantibodies / Q000097:blood / Q000276:immunology*; D016022:Case-Control Studies; D002648:Child; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005956:Glucose-6-Phosphate Isomerase / Q000276:immunology*; D006801:Humans; D015151:Immunoblotting; D007074:Immunoglobulin G / Q000378:metabolism; D008297:Male; D009994:Osmolar Concentration; D011506:Proteins / Q000276:immunology; D011994:Recombinant Proteins / Q000276:immunology; D012720:Severity of Illness Index; D013582:Synovial Fluid / Q000276:immunology
D001323:Autoantibodies; D007074:Immunoglobulin G; D011506:Proteins; D011994:Recombinant Proteins; D005956:Glucose-6-Phosphate Isomerase