Autoimmunity against YKL-39, a human cartilage derived protein, in patients with osteoarthritis.
OBJECTIVE
Our previous study revealed that some patients with rheumatoid arthritis (RA) possessed autoantibodies to YKL-39, a cartilage related protein. We investigated whether patients with osteoarthritis (OA) also displayed autoimmunity to YKL-39.


METHODS
Autoantibodies to recombinant YKL-39 as well as human cartilage glycoprotein-39 were detected by ELISA and Western blotting. The tested serum samples were derived from 117 patients with OA, 94 patients with RA, and 2 groups of 50 arthropathy-free healthy donors who matched the OA and RA groups for age and sex. We determined autoepitopes on YKL-39 using 3 overlapping fragments of YKL-39 (designated F1, F2, F3). T cell proliferation response to YKL-39 was analyzed using the 3H-thymidine incorporation assay.


RESULTS
Autoantibodies to YKL-39 were detected in 13 (11.1%) patients with OA and 11 (11.8%) with RA. In the epitope mapping, all the 3 fragments of YKL-39 were found to carry autoepitopes, but F1 was recognized most frequently. Proliferative responses of peripheral blood mononuclear cells against YKL-39 were detected in 6 (46%) of the 13 OA patients who were positive for the anti-YKL-39 autoantibodies and in 2 (17%) of the 11 antibody positive RA patients.


CONCLUSIONS
These results show that autoimmunity to YKL-39 in patients with OA was present at equal or somewhat higher frequency than in patients with RA. The cellular and humoral immune responses to YKL-39 may be involved in the pathological process of OA as well as RA.
Tsuruha
Jun-Ichiro
J
Rheumatology, Immunology and Genetics Program, Institute of Medical Science, St Marianna University School of Medicine, Kawasaki, Japan.
Masuko-Hongo
Kayo
K
Kato
Tomohiro
T
Sakata
Masahiro
M
Nakamura
Hiroshi
H
Sekine
Taichi
T
Takigawa
Masaharu
M
Nishioka
Kusuki
K
D054392:Adipokines; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000917:Antibody Formation / Q000502:physiology; D001323:Autoantibodies / Q000032:analysis*; D015551:Autoimmunity / Q000502:physiology*; D001483:Base Sequence; D015153:Blotting, Western; D002358:Cartilage, Articular / Q000276:immunology / Q000378:metabolism; D000071451:Chitinase-3-Like Protein 1; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006023:Glycoproteins / Q000276:immunology*; D006801:Humans; D007111:Immunity, Cellular / Q000502:physiology; D037102:Lectins; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D010003:Osteoarthritis / Q000276:immunology* / Q000503:physiopathology; D016133:Polymerase Chain Reaction / Q000379:methods; D012016:Reference Values; D012680:Sensitivity and Specificity
D054392:Adipokines; D001323:Autoantibodies; C084533:CHI3L1 protein, human; D000071451:Chitinase-3-Like Protein 1; D006023:Glycoproteins; D037102:Lectins