Generation of neoantigenic epitopes after posttranslational modification of type II collagen by factors present within the inflamed joint.
OBJECTIVE
Collagen-induced arthritis is a commonly accepted model of rheumatoid arthritis (RA). However, it has been difficult to substantiate the involvement of autoimmunity to type II collagen (CII) in the pathogenesis of RA. The aim of this investigation was to determine if CII, modified by reactive oxidant species present within the inflamed joint, could generate neoantigenic epitopes.


METHODS
Oxidants that play a role in acute and chronic inflammation and are present in the rheumatoid joint (hydroxyl radical, hypochlorous acid, and peroxynitrite) were used for modification of native CII. In addition, CII was glycated with ribose, since nonenzymatic oxidative reactions by glycation are evident in RA. Modifications were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and 3-dimensional fluorescence followed by enzyme-linked immunosorbent assay (ELISA) and Western blotting, using, as probes, sera from patients with RA and from patients with other inflammatory and noninflammatory joint diseases.


RESULTS
Only 1 RA serum sample showed strong binding to native CII. In contrast, binding to modified CII was increased in 14 of 31 RA sera, of which 7 were strong binders and 7 were moderate binders. Among the non-RA serum samples, only 1 yielded a strong reaction to modified CII and 5 of 41 were moderate binders. Samples that showed the strongest binding to modified CII in ELISA also showed strong binding to various fragmented or aggregated forms of CII in Western blots, as well as strong binding to fragmented CII present in RA synovial fluid.


CONCLUSIONS
When modified by conditions found within the inflamed joint, CII acts as an autoantigen in RA.
Nissim
Ahuva
A
Bones and Joint Research Unit, Barts and The London, University of London, London, UK. a.nissim@qmul.ac.uk
Winyard
Paul G
PG
Corrigall
Valerie
V
Fatah
Rewas
R
Perrett
David
D
Panayi
Gabriel
G
Chernajovsky
Yuti
Y
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000918:Antibody Specificity; D001169:Arthritis, Experimental / Q000276:immunology* / Q000378:metabolism; D001172:Arthritis, Rheumatoid / Q000276:immunology* / Q000378:metabolism; D001324:Autoantigens / Q000276:immunology / Q000378:metabolism; D015153:Blotting, Western; D002417:Cattle; D024043:Collagen Type II / Q000032:analysis / Q000276:immunology* / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D000939:Epitopes / Q000276:immunology* / Q000378:metabolism; D005260:Female; D005453:Fluorescence; D006801:Humans; D008297:Male; D051379:Mice; D008811:Mice, Inbred DBA; D008875:Middle Aged; D016877:Oxidants / Q000494:pharmacology; D011499:Protein Processing, Post-Translational; D013582:Synovial Fluid / Q000276:immunology / Q000378:metabolism
D001324:Autoantigens; D024043:Collagen Type II; D000939:Epitopes; D016877:Oxidants