Introduction: B lymphocyte activating factor (BAFF), a member of the tumour necrosis factor family, is essential for B cell activation, differentiation and survival. It promotes autoantibody production and as Graves disease is caused by thyroid stimulating autoantibodies, it is an excellent functional candidate gene. Indeed, elevated serum BAFF levels have been found in patients with several autoimmune diseases, including Graves disease (GD). The T allele of the BAFF promoter SNP (rs9514828; -871C/T) has been associated with susceptibility to the autoimmune conditions systemic lupus erythematous (SLE) in Egyptians, and immune thrombocytopenic purpura in Chinese and German cohorts.
Aim: To investigate whether variants in the BAFF gene are associated with GD in a cohort of UK patients.
Methodology: A case-control association study was performed. rs9514828 was genotyped in 486 UK GD patients using Taqman chemistry (Life Technologies) and results compared to genotype data from 5158 healthy individuals available from the Wellcome Trust (WTCCC2). Statistical association analysis was performed using PLINK.
Results: There was no significant difference between the frequency of the T allele in UK GD subjects (491/972; 51%) compared to controls (5046/10316; 49%: P 0.34, OR 1.07 [95% CI 0.931.21]). Similarly, there was no difference in genotype frequencies between the UK GD cases and controls. The TT genotype was present in 113/486 (23%) cases compared to 1220/5158 (24%) controls, while 265/486 (55%) of cases were heterozygous compared to 2606/5158 (50%) controls (P 0.16).
Interpretation and Conclusion: The rs9514828 SNP is not associated with GD in a UK cohort. This could be related to allelic heterogeneity, with different BAFF SNPs contributing to autoimmune susceptibility in Caucasians, compared to other populations. It is also possible that the genetic variants contributing to multisystem autoimmune diseases, such as SLE, may be distinct from those in single organ-specific autoimmune conditions such as GD.