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* Department of Immunology, Mayo Clinic, Rochester, MN 55905;
Department of Medicine, University of Utah, Salt Lake City, UT 84148;
Department of Rheumatology, Mayo Clinic, Rochester, MN 55905; and
Summer Student from Berea College, Berea, KY 40604
In humans, HLA-DR alleles sharing amino acids at the third hypervariable region with DRB1*0401(shared epitope) are associated with a predisposition to rheumatoid arthritis, whereas DRB1*0402 is not associated with such a predisposition. Both DRB1*0402 and DRB1*0401 occur in linkage with DQ8 (DQB1*0302). We have previously shown that transgenic (Tg) mice expressing HLA-DRB1*0401 develop collagen-induced arthritis. To delineate the role of "shared epitope" and gene complementation between DR and DQ in arthritis, we generated DRB1*0402, DRB1*0401.DQ8, and DRB1*0402.DQ8 Tg mice lacking endogenous class II molecules, AE°. DRB1*0402 mice are resistant to develop arthritis. In double-Tg mice, the DRB1*0401 gene contributes to the development of collagen-induced arthritis, whereas DRB1*0402 prevents the disease. Humoral response to type II collagen is not defective in resistant mice, although cellular response to type II collagen is lower in *0402 mice compared with *0401 mice. *0402 mice have lower numbers of T cells in thymus compared with *0401 mice, suggesting that the protective effect could be due to deletion of autoreactive T cells. Additionally, DRB1*0402 mice have a higher number of regulatory T cells and show increased activation-induced cell death, which might contribute toward protection. In DRB1*0401.DQ8 mice, activated CD4+ T cells express class II genes and can present DR4- and DQ8-restricted peptides in vitro, suggesting a role of class II+ CD4 T cells locally in the joints. The data suggest that polymorphism in DRB1 genes determines predisposition to develop arthritis by shaping the T cell repertoire in thymus and activating autoreactive or regulatory T cells.
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1 This study was supported by National Institutes of Health Grant AR 30752 and by the Mayo Foundation.
2 Address correspondence and reprint request to Dr. Veena Taneja, Department of Immunology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905. E-mail address: taneja.veena{at}mayo.edu
3 Abbreviations used in this paper: RA, rheumatoid arthritis; AICD, activation-induced cell death; CIA, collagen-induced arthritis; CII, type II collagen; LNC, lymph node cell; RF, rheumatoid factor; Tg, transgenic.
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