Objective: Tumor necrosis factor (TNF) is a powerful mediator of inflammation in rheumatoid arthritis (RA). In vivo, its acute effects are limited by binding to soluble receptors (TNFR), suggesting that TNFR genes could be important candidate risk factors. The present study was undertaken to investigate association of polymorphisms of TNFRI and TNFRII with RA in subjects in the UK.
Methods: Unrelated Caucasian RA patients (n = 291) and healthy Caucasian controls (n = 143) were genotyped for A/G polymorphism in exon 1 of TNFRI. From this sample, 240 of the patients and 137 controls were also typed for a single-nucleotide polymorphism (SNP) in exon 6 of the TNFRII gene. In followup studies, DNA samples from UK Caucasian RA patients with a positive family history (n = 149) and UK Caucasian patients with sporadic RA (n = 208) were also typed for the exon 6 TNFRII polymorphism.
Results: TNFRI polymorphism was not associated with RA (odds ratio [OR] for GG genotype 0.93, 95% confidence interval [95% CI] 0.54-1.60). For TNFRII, in the initial study group, patients with RA were significantly more likely to be positive for both the G allele and GG genotype than were controls (OR for GG genotype 2.55, 95% CI 1.11-5.86). The association appeared to be confined to those with a family history of RA. This finding was replicated in an independent cohort of patients with familial RA.
Conclusion: The results of this study provide evidence of association between an SNP in the TNFRII gene and RA, the strongest association being observed in patients with a family history. No evidence of association between RA and TNFRI was demonstrated.