Association between CTLA-4 polymorphisms and the susceptibility to systemic lupus erythematosus and Graves' disease in Thai population

Abstract

Background: Cytotoxic T-lymphocyte antigen-4 (CTLA-4) is a cell surface molecule involved in the regulation of T cells. Single nucleotide polymorphisms (SNPs) of CTLA-4 gene are known to be associated with susceptibility to several autoimmune diseases, including systemic lupus erythematosus (SLE) and Graves' disease (GD).

Objective: The aim of this study was to determine whether the common SNPs +49A/G on exon1 and CT60A/G in 3'UTR of the CTLA-4 gene are associated with susceptibility to SLE and GD in Thai population.

Methods: Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to analyze these two SNPs in 151 patients with SLE, 132 patients with GD and 153 healthy controls.

Results: Our study showed that there were no statistically significant differences in the allele and genotype frequencies of +49A/G and CT60A/G SNPs between patients with SLE and healthy controls as well as patients with GD vs. healthy controls (P > 0.05). However, the GG genotypes of +49A/G and CT60A/G were likely to be risk factors (OR >1) for GD but not in SLE. The effect of the +49G allele was similar to that of an autosomal recessive gene in the presence of the GG genotype, when compared to AA and AG, with an OR of 1.58 (95% CI = 0.95-2.61, p = 0.061) in GD. We also observed a dose response effect of the CT60G allele on GD susceptibility with an OR of 1.43 for GG homozygous and 1.17 for AG heterozygous subjects, when compared to the AA genotype, although these were not statistically significant (P > 0.05).

Conclusion: We found no association between two functional polymorphisms (+49A/G and CT60A/G) of the CTLA-4 gene and susceptibility to SLE and GD. However, the association study utilizing a larger sample size should be performed to confirm this.