Background: Rheumatoid arthritis (RA) is currently thought to be an immune-mediated disease where the host's genes and environmental factors interact. Some of the immuno-regulatory genes that are responsible for an individual's susceptibility to RA have been identified. The co-stimulatory receptor gene cluster on chromosome 2q33 encodes for both the positive T-cell regulators CD28 molecule (CD28) and inducible T-cell co-stimulator (ICOS), and the negative regulator cytotoxic T-lymphocyte-associated protein 4 (CTLA4). The CTLA4 gene has been implicated in several immune-mediated diseases, but it is not known whether RA is associated with any of these genes.
Methods: We conducted single nucleotide polymorphism (SNP) genotyping with direct sequencing and restriction fragment length polymorphism for 308 Korean patients with RA and 412 healthy control subjects. For the case-control analysis, SNPStats, SNPAnalyzer and Helixtree programs were used.
Results: Although none of the polymorphisms in CTLA4 showed a significant association with RA, CD28 and ICOS showed a significant association with RA [rs2140148 in CD28, p = 0.022, odds ratio (OR) = 1.60, 95% confidence interval (CI) = 1.07-2.40 in the dominant model, rs6726035 in ICOS, p = 0.032, OR = 1.28, 95% CI = 1.02-1.60 in the codominant model].
Conclusions: Our results suggest that CD28 and ICOS genes may be associated with a risk of RA in Koreans.