Increased Serum Levels of IL-28 and IL-29 and the Protective Effect of IL28B rs8099917 Polymorphism in Patients with Hashimoto's Thyroiditis

Hashimoto's thyroiditis (HT) is thought to result from decreased T helper type 2 (Th2) responses, leading to the progressive destruction of thyrocytes. IFN-1, -2, and -3 (also known as IL-29, IL-28A, and IL-28B, respectively) are recently described members of the IFN- family and have been shown to decrease the production of Th2 cytokines in vitro. However, the role and mechanism of IFN-1 in HT remain unknown. The purpose of this study was to examine whether IL29 and IL28B gene polymorphisms are susceptibility genes for the development of HT. Also, we investigated the effects of IL-29 and IL-28 serum levels in the pathogenesis of HT. Using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, single-nucleotide polymorphisms (SNPs) of IL28B rs8099917 (IL28 G/T) and IL29 rs30461 (IL29 T/C) were studied in 99 patients with HT and 100 healthy controls. Considering the allelic distribution of the IL28 G/T polymorphism, a higher frequency of the G allele was observed in the control group versus the HT group. Thus, it was suggested that the G allele may be protective against HT pathogenesis (OR = 0.388, 95% CI = 0.217-0.693; p = 0.001). Our findings also demonstrated that there was a statistically significant difference in serum IL-28 and IL-29 levels between case and control groups (p < 0.001). Increased serum levels of IL-28 and IL-29 were found in patients with HT. However, we did not find a relationship between the IL29 gene polymorphism and HT. In conclusion, the IL28B gene polymorphism and serum IL-28 and IL-29 levels seem to play a role in the pathogenesis of HT.