Association of interleukin-17A and -17F gene single-nucleotide polymorphisms with autoimmune thyroid diseases

Th17 lymphocyte and its relative cytokines have been shown to play an important role in autoimmune thyroid diseases (AITD). The aim of this study was to investigate the association between IL-17A and IL-17F gene polymorphisms and two main types of AITD, Graves' disease (GD) and Hashimoto's thyroiditis (HT). Whole blood specimens and clinical data were collected from 508 AITD patients (326 with GD and 182 with HT) and 224 age-and gender-matched healthy controls, respectively. IL-17A (rs2275913, rs8193037, rs3819025) polymorphism was determined using DNA sequencing method and IL-17F/rs763780 polymorphism was assayed by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results indicated that the frequencies of IL-17F/rs763780 genotypes in patients with GD and HT differed significantly from their controls (P = 0.013 and P = 0.005, respectively); the G allele frequencies were also significantly higher in the patient groups than the control groups (P = 0.002 and 0.001, respectively). For IL-17A/rs2275913 and rs8193037 SNP, no significant difference was observed in patients with either GD or HT compared to the control groups (P > 0.05). Interestingly, for rs3819025, the frequency of A allele was lower in patients with GD than controls (P = 0.011). The frequencies of haplotype AGGG and GGGG in patients with GD and HT were significantly higher than in controls (P = 0.012, P = 0.019, P = 0.017 and P = 0.029, respectively). In conclusion, the results indicate that IL-17F/rs763780 polymorphisms may affect the susceptibility to AITD, and IL-17A/rs3819025 SNP is likely a protective factor to GD in the Chinese population.