Journal
ANNALS OF THE RHEUMATIC DISEASES
Volume 78, Issue 3, Pages 380-390Publisher
BMJ PUBLISHING GROUP
DOI: 10.1136/annrheumdis-2018-214125
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Funding
- National Institutes of Health
- National Institute of Arthritis and Skin and Musculoskeletal Diseases [R01 AR047988]
- National Institute of Diabetes and Kidney Diseases [R01 DK105833]
- Alliance for Lupus Research [TIL332615]
- Lupus Research Alliance [DIA481517]
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Objectives The generation of systemic lupus erythematosus (SLE)-related autoantibodies have been shown to be T cell dependent and antigen driven with HLA-DR restriction. In this study, the initiating antigen(s) and the mechanism of autoantibody diversification were investigated. Methods T cell epitopes (T-epitopes) of SmD1 (SmD) were mapped by T-T hybridomas generated from DR3(+)AE(0) mice immunised with SmD and with SmD overlapping peptides. TCRs from the reactive hybridomas were sequenced. The core epitopes were determined. Bacterial mimics were identified by bioinformatics. Sera from DR3(+)AE(0) mice immunised with SmD peptides and their mimics were analysed for their reactivity by ELISA and immunohistochemistry. Samples of blood donors were analysed for HLA-DR and autoantibody specificities. Results Multiple HLA-DR3 restricted T-epitopes within SmD were identified. Many T-T hybridomas reacted with more than one epitope. Some of them were cross-reactive with other snRNP peptides and with proteins in the Ro60/La/Ro52 complex. The reactive hybridomas used unique TCRs. Multiple T-epitope mimics were identified in commensal and environmental bacteria. Certain bacterial mimics shared both T and B cell epitopes with the related SmD peptide. Bacterial mimics induced autoantibodies to lupus-related antigens and to different tissues. HLA-DR3(+) blood donors made significantly more SLE-related autoantibodies. Conclusions The unique antigenic structures of the lupus-related autoantigens provide the basis for being targeted and for T and B cell epitope spreading and autoantibody diversification with unique patterns. SLE-related autoantibodies are likely generated from responses to commensal and/or environmental microbes due to incomplete negative selection for autoreactive T cells. The production of SLE-related antibodies is inevitable in normal individuals. The findings in this investigation have significant implications in autoimmunity in general.
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