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  • Clinical, immunological, and immunogenetic aspects of autoantibody production against Ro/SSA, La/SSB and their linear epitopes in primary Sjögren's syndrome (pSS): a European multicentre study

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Clinical, immunological, and immunogenetic aspects of autoantibody production against Ro/SSA, La/SSB and their linear epitopes in primary Sjögren's syndrome (pSS): a European multicentre study
  1. A G Tzioufas1,
  2. R Wassmuth2,
  3. U G Dafni3,
  4. A Guialis4,
  5. H-J Haga5,
  6. D A Isenberg6,
  7. R Jonsson5,
  8. J R Kalden2,
  9. H Kiener7,
  10. C Sakarellos8,
  11. J S Smolen7,
  12. N Sutcliffe6,
  13. C Vitali9,
  14. E Yiannaki1,
  15. H M Moutsopoulos1
  1. 1Department of Pathophysiology, School of Medicine, University of Athens, Greece
  2. 2Department of Medicine III, Institute for Clinical Immunology, University of Erlangen-Nürnberg, Germany
  3. 3Faculty of Nursing, School of Health Sciences, University of Athens, Greece
  4. 4Institute of Biological Research and Biotechnology, The National Hellenic Research Foundation, Athens, Greece
  5. 5University of Bergen, Bergen, Norway
  6. 6University College, London, UK
  7. 7University of Vienna and Lainz Hospital, Vienna, Austria
  8. 8Laboratory of Organic Chemistry, Ioannina, Greece
  9. 9University of Pisa, Pisa, Italy
  1. Correspondence to:
    Dr A G Tzioufas, Department of Pathophysiology, School of Medicine, University of Athens, 75 M Asias St 11527 Athens, Greece;
    agtzi{at}med.uoa.gr

Abstract

Objectives: To investigate the clinical and immunogenetic aspects of antibody formation against Ro/SSA and La/SSB as well as their linear B cell epitopes in patients with primary Sjögren's syndrome (pSS) from different European countries.

Patients and methods: Ninety patients with pSS from six European centres were studied. Serum samples from all patients were tested in a control laboratory for anti-Ro/SSA and anti-La/SSB autoantibodies by RNA precipitation assay and autoantibodies to the previously reported B cell linear epitopes of Ro 60 kDa (p169–190aa and p211–232aa) and La/SSB (p147–154aa, p291–302aa, p301–318aa, and p349–364aa). DNA from 88 patients was used for the determination of HLA-DRB1, -DQA1, and -DQB1 genotypes. Analysis of the results was performed in the 88 patients who were genotyped and tested also for antipeptide antibodies.

Results: Antibodies to B cell epitopes of Ro 60 kDa were detected at a low frequency (range 10–37%). In contrast, B cell epitopes of La/SSB were detected frequently (range 58–86%) among the anti-La/SSB positive sera. Autoantibodies to the La/SSB epitope, p349–364aa, were significantly positively associated with longer disease duration (p<0.05), recurrent or permanent parotid gland enlargement (p<0.005), and a higher proportion of non-exocrine manifestations (p<0.005), compared with patients without autoantibodies. The presence of anti-Ro/SSA and anti-La/SSB autoantibodies was significantly associated with the presence of HLA-DRB1*03 and DQB1*02 (p=0.038 and p=0.034, respectively). This association was even more prominent and extended to HLA-DQA1*0501 when patients were stratified according the presence of autoantibodies to discrete La/SSB B cell epitopes in comparison with autoantibody negative patients (p<0.01). They were found also to be highly associated with the alleles HLA-DQB1*02 and HLA-DQA1*0501 as well as the presence of a shared amino acid motif in the region 59–69aa of DQB1 first domain (p<0.01, respectively).

Conclusions: Autoantibodies against La/SSB, binding to four synthetic peptides, derived from the sequence of the La protein were identified with increased frequency in sera of patients with pSS. The formation of autoantibodies against B cell epitope analogues of La/SSB in European patients with pSS may be dependent on the presence of a permissive HLA-DQ heterodimer, most prominently represented by the HLA-DQA1*0501/DQB1*0201 heterodimer, suggesting that a model of HLA restricted presentation of La/SSB peptide determinants is crucial for the autoimmune response against La/SSB.

  • Sjögren's syndrome
  • anti-Ro/SSA
  • anti-La/SSB
  • B cell epitopes
  • immunogenetic studies
  • BSA, bovine serum albumin
  • MHC, major histocompatibility complex
  • OR, odds ratio
  • PBS, phosphate buffered saline
  • pSS, primary Sjögren' syndrome
  • SLE, systemic lupus erythematosus

https://doi.org/10.1136/ard.61.5.398

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    Footnotes

    • Dr R Wassmuth is currently with the Institute for Transplantation Diagnostics and Cell Therapeutics, University Medical Centre of Duesseldorf, Germany.