<i>ICOS</i> gene polymorphisms in systemic lupus erythematosus: A case–control study

Abstract The inducible T‐cell costimulator (ICOS) may play an important role in adaptive immunity by regulating the interaction between T cells and antigen‐presenting cells. Disruption of this molecule can lead to autoimmune diseases, in particular systemic lupus erythematosus (SLE). In this study, we aimed to explore the possible association between ICOS gene polymorphisms and SLE as well as their influence on disease susceptibility and clinical outcomes. A further objective was to assess the potential impact of these polymorphisms on RNA expression. A case–control study, including 151 patients with SLE, and 291 unrelated healthy controls (HC) matched in gender, and geographical origin, was performed to genotype two polymorphisms located in the ICOS gene: rs11889031 (−693 G/A) and rs10932029 (IVS1 + 173 T/C); using the polymerase chain reaction (PCR)‐restriction fragment length polymorphism method. The different genotypes were validated by direct sequencing. The expression level of ICOS mRNA was assessed by quantitative PCR in peripheral blood mononuclear cells of SLE patients and HC. The results were analysed using Shesis and spss .20. Our results revealed a significant association between ICOS gene rs11889031 > CC genotype and SLE disease (codominant genetic model 1, (C/C vs. C/T), p  = .001, odds ratio [OR] = 2.18 IC [1.36–3.49]); codominant genetic model 2, (C/C vs. T/T) p  = .007, OR = 15.29 IC [1.97–118.5]); dominant genetic model, (C/C vs. C/T + T/T) p  = .0001, OR = 2.44 IC [1.53–3.9]). Besides, there was a marginal association between rs11889031 > TT genotype and T allele with a protective role from SLE (recessive genetic model, p  = .016, OR = 0.08 IC [0.01–0.63] and p  = 7.6904E − 05, OR = 0.43 IC = [0.28–0.66], respectively). Moreover, statistical analysis indicated that the rs11889031 > CC genotype was linked with clinical and serological manifestations of SLE, including blood pressure, and anti‐SSA antibodies production in SLE patients. However, the ICOS gene rs10932029 polymorphism was not associated with susceptibility to SLE. On the other side, we did not note any effect of the two selected polymorphisms on the level of ICOS mRNA gene expression. The study showed a significant predisposing association of the ICOS rs11889031 > CC genotype with SLE, in contrast to a protective effect of rs11889031 > TT genotype in Tunisian patients. Our results suggest that ICOS rs11889031 may act as a risk factor for SLE and could be used as a genetic susceptibility biomarker.