association of -475 and -631 interleukin-2 gene polymorphism with multiple sclerosis in Iranian patients

ABSTRACT

Multiple sclerosis [MS] is a chronic autoimmune disease due to demyelination of the central nervous system. It is believed that cytokines are involved in the pathogenesis of MS. The interleukin-2 [IL2] gene is powerful functional candidate that is involved in immune regulation and operation. In this study, for the first time, we investigated the effect of -475 A/T and -631 G/A IL2 polymorphisms on MS disease in Iranian patients. In this case-control study, 100 MS patients [mean age 32.95 +/- 6.51 years, age range 20-42 years] selected according to McDonald criteria, and 100 ethnically, sex and age matched healthy controls [mean age 29 +/- 7.8 years, age range 20-52 years] with no personal or family history of autoimmune diseases were studied. The restriction fragment length polymorphism-polymerase chain reaction [RFLP-PCR] method was applied to define different alleles and genotypes of IL2 promoter single nucleotide polymorphism -475 A/T as well as -631 G/A among individuals. chi [2] was calculated and Fisher's exact test was applied to analyze the obtained data. The value of p <0.05 was considered significantly. Evaluation of the -475 IL2 revealed that T allele and A/T genotype are present in 2% and 4% of MS patients, respectively, whereas T allele was absent in control samples. The comparison between alleles and genotypes in MS patients and healthy controls was not significant [p=0.1]. For the -631 position, 1% and 2% of MS patients carried A allele and A/G heterozygote genotypes, respectively. All control samples had G allele and G/G genotype. The differences between patients and controls were not significant [p=0.4]. Moreover, our results showed a very low frequency of T at -475 and A at -631 IL2 position in each of the two groups. Both -475 and -631 IL2 polymorphisms were higher in MS patients as compared to controls, but the frequency differences were not significant. Based on these data, it is suggested that the -475 and -631 IL2 polymorphisms as functional promoter position may be involved in IL2 expression and regulation. To find out the exact effect of the mentioned SNPs on susceptibility to MS, study on a larger sample size is suggested