Polymorphisms of interleukin-21 and interleukin-21-receptor genes confer risk for autoimmune thyroid diseases

Abstract

Background: The abnormality of interleukin-21 (IL-21)-IL-21-receptor (IL-21R) system has been found in many autoimmune diseases including autoimmune thyroid diseases (AITDs). In this study, we investigated whether polymorphisms of the IL-21 and IL-21R are associated with Graves' disease (GD) and Hashimoto's thyroiditis (HT), two major forms of AITDs, among a Chinese population.Methods: Rs907715, rs4833837, rs2221903 and rs2055979 of the IL-21 gene and rs3093301 and rs2285452 of the IL-21R gene were explored in a case-control study including 405 GD, 228 HT patients and 242 controls. These genes were genotyped by the PCR and restriction fragment length polymorphism (RFLP) analysis and the MASS spectrometry method.Results: For IL-21 gene, we identified and confirmed a higher prevalence of A alleles of rs2221903 (P = 0.018, OR = 1.50 95% CI = 1.07-2.09) in GD patients. We also found a significant association between rs2221903 and HT (allele: P = 0.009, OR = 1.69 95% CI = 1.13-2.51; genotype: recessive P = 0.021, OR = 11.72 95% CI = 1.46-94.13). For the IL-21R gene, compared with controls, the genotype frequencies of rs3093301 and rs2285452 were significantly different in HT patients using dominant genetic model (P = 0.023, OR = 1.61 95% CI = 1.07-2.42; P = 0.031, OR = 1.71 95% CI = 1.05-2.80, respectively). Furthermore, the haplotype AA containing the major alleles of rs4833837 and rs2221903 was associated with increased susceptibility to GD with an OR of 1.50(95% CI =1.08-2.09, P = 0.016), and to HT with an OR of 1.69(95% CI =1.14-2.52, P = 0.009).Conclusion: Our results indicated that the SNPs of the IL-21 gene is associated with the development of GD. In addition, we found that individuals with the SNPs of the common IL-21 and IL-21R may have higher risk of HT. © 2013 Zhang et al.; licensee BioMed Central Ltd.