The Association of Single Nucleotide Polymorphism of Interleukin-21 Gene and Serum Interleukin-21 Levels in Egyptian Systemic Lupus Erythematosus Patients

Abstract

Background: Systemic lupus erythematosus (SLE) is a common autoimmune disorder which commonly results from the combined effects of a large number of genes. Variations in the DNA sequence in the Interleukin-21 (IL-21) gene may lead to altered IL-21 production and/or activity which can affect an individual’s susceptibility to SLE. IL-21 is a novel class I cytokine produced by activated CD4+ T cells, natural killer T cells and T helper (Th) cells. There is increasing evidence that IL-21 contributes to the pathogenesis of SLE due to its biological activity. Aim of the study: To investigate the association between single nucleotide polymorphism (SNP) of IL-21 rs2221903 gene and serum IL-21 levels with SLE and to detect the possible association between IL-21 serum levels and the pathogenesis of the disease. Subjects and methods: This study was conducted on 30 SLE patients and 20 age and sex matched healthy controls. Serum IL-21 levels were measured using enzyme-linked immunosorbent assay (ELISA) technique and SNP of IL-21 rs2221903 gene was detected by genotyping assay, using real time polymerase chain reaction (RT-PCR). Results: Serum Il-21 levels were significantly higher in patients compared with controls (p<0.001). Patients with high activity index of SLE had significantly higher levels of serum IL-21 (p value < 0.001). A statistically significant association was found between the T allele of SNP rs2221903 and SLE, but; no association between SNP of IL-21 rs2221903 genotypes and SLE or serum IL-21 levels could be detected. Conclusion: IL-21 plays an important role in the immune-pathogenesis of SLE and could be used as a possible target for novel immunotherapy. The T allele of SNP rs2221903 suggests that the IL-21 gene may contribute to an inherited predisposition to SLE. Key words: SLE, IL-21, single nucleotide polymorphism, T allele, Genotypes.