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Smoking, the HLA-DRB1 shared epitope and ACPA fine-specificity in Koreans with rheumatoid arthritis: evidence for more than one pathogenic pathway linking smoking to disease
  1. Benjamin A Fisher1,
  2. So-Young Bang2,
  3. Muslima Chowdhury3,
  4. Hye-Soon Lee2,
  5. Jae-Hoon Kim2,
  6. Peter Charles3,
  7. Patrick Venables3,
  8. Sang-Cheol Bae2
  1. 1Rheumatology Research Group, University of Birmingham, Birmingham, UK
  2. 2Department of Rheumatology, Hanyang University Hospital for Rheumatic Diseases, Seoul, Republic of Korea
  3. 3Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Kennedy Institute of Rheumatology, University of Oxford, London, UK
  1. Correspondence to Dr Benjamin A Fisher, Rheumatology Research Group, Centre for Translational Inflammation Research, School of Immunity and Infection, College of Medical and Dental Sciences, University of Birmingham Research Laboratories, New Queen Elizabeth Hospital, Birmingham, B15 2WB, UK; b.fisher{at}bham.ac.uk. Prof Sang-Cheol Bae, Department of Rheumatology, Hanyang University Hospital for Rheumatic Diseases, Seoul 133-792, Korea

Abstract

Objectives Data from North European rheumatoid arthritis (RA) populations has suggested a particularly strong association of gene-environment interaction between smoking and HLA-DRB1 shared epitope (SE) with antibodies to citrullinated α-enolase (CEP-1) and vimentin (cVim) peptides. We investigated this further by examining antibodies to citrullinated peptides/proteins (ACPA) ‘fine specificity’ in a Korean We investigated this further by examining anticitrullinated peptide/protein antibody (ACPA) fine specificity cohort, where there are notable differences in the RA-associated HLA-DRB1 alleles.

Methods Antibodies to fibrinogen (cFib), α-enolase (CEP-1) and vimentin (cVim) peptides and cyclic citrullinated peptide (CCP) were measured in 513 cases. The Mann-Whitney U test was used to compare antibody levels. Logistic regression generated ORs for RA in a case-control analysis with 1101 controls. Association of ACPA status and erosion in patients with RA was examined by logistic regression.

Results Anti-CCP, CEP-1, cVim and fibrinogen peptides were found in 86.7%, 63.9%, 45.5% and 74.7%, respectively. The number of ACPA and their levels were associated with SE, with evidence of a gene-dosage effect. There was a particular association of smoking with levels of anti-CEP-1. However, a gene-environment interaction was associated with all the ACPA positive subgroups, albeit the highest OR was seen with the anti-CCP+/cVim+ subset. In the absence of SE, smoking only conferred risk for anti-CCP negative subsets. The presence of erosions was not associated with the number of positive ACPA or specificity.

Conclusions The SE governed the magnitude and diversity of the ACPA response, but its interaction with smoking did not exclusively segregate with any of the ACPA specificities studied here. Smoking was associated with RA by SE-dependent and independent effects.

  • Ant-CCP
  • Rheumatoid Arthritis
  • Epidemiology

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