Reevaluation of the interaction between HLA–DRB1 shared epitope alleles,PTPN22, and smoking in determining susceptibility to autoantibody‐positive and autoantibody‐negative rheumatoid arthritis in a large UK Caucasian population |
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| Authors: | Wendy Thomson Stephen G. Martin Yorkshire Early Arthritis Register Consortium Angela M. Carter UK Rheumatoid Arthritis Genetics Consortium Henry A. Erlich Anne Barton Lynne Hocking David M. Reid Pille Harrison Paul Wordsworth Sophia Steer Jane Worthington Paul Emery Anthony G. Wilson Jennifer H. Barrett |
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| Affiliation: | 1. University of Manchester, Manchester, UK;2. University of Leeds, Leeds, UK;3. Members of the YEAR Consortium and the UK Rheumatoid Arthritis Genetics Consortium are listed in Appendices A and B, respectively.;4. Roche Molecular Systems, Pleasanton, California;5. University of Aberdeen, Aberdeen, UK;6. University of Oxford, Oxford, UK;7. Kings College Hospital National Health Service Foundation Trust, London, UK;8. University of Sheffield, Sheffield, UK |
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| Abstract: | Objective To define interactions between the HLA–DRB1 shared epitope (SE), PTPN22, and smoking in cyclic citrullinated peptide (CCP) antibody– and rheumatoid factor (RF)–positive and –negative rheumatoid arthritis (RA). Methods Data on ∼5,000 RA patients and ∼3,700 healthy controls recruited from 6 centers in the UK were analyzed; not all centers had both genotype data and smoking data available for study. The magnitude of association was assessed in autoantibody‐positive and ‐negative subgroups. The effect of smoking on antibody status among cases was assessed following adjustment for year of birth and center, using Mantel‐Haenszel analysis. Analyses of the combined effects of PTPN22, HLA–DRB1 SE, and smoking were performed using additive and multiplicative models of interaction within a logistic regression framework. Results The combined effects of PTPN22, HLA–DRB1 SE, and smoking were defined, with no evidence of departure from a multiplicative model. Within the case population, all 3 factors were independently associated with the generation of CCP antibodies (odds ratio [OR] 11.1, P < 0.0001), whereas only HLA–DRB1 SE and smoking were independently associated with RF production (OR 4.4, P < 0.0001). There was some evidence of increasing likelihood of antibody positivity with heavier smoking. Finally, we demonstrated that smoking was associated with the generation of both CCP and RF antibodies (OR 1.7, P = 0.0001). Conclusion PTPN22 appears to be primarily associated with anticitrulline autoimmunity, whereas HLA–DRB1 SE is independently associated with RF. This study has confirmed associations of specific gene–environment combinations with a substantially increased risk of developing RA. Further work is needed to determine how these data can be used to inform clinical practice. |
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