LAUSR

To clarify the association between the genetic producibility of IL‐15, a pro‐inflammatory cytokine, and the pathogenesis of autoimmune thyroid diseases (AITDs), we genotyped +96522 A>T and +82889 A>G polymorphisms in the IL15 gene using 127 patients with Hashimoto's disease (HD), including 55 patients with severe HD and 48 patients with mild HD; 130 patients with Graves’ disease (GD), including 52 patients with intractable GD and 44 patients with GD in remission; and 79 healthy volunteers. Both the IL15 +96522 A allele and AA genotype were more frequent in patients with severe HD than in those with mild HD. The serum levels of IL‐15 were higher in individuals with the IL15 +96522 AA genotype than in those with the T allele, and they were also higher in patients with severe HD than in those with mild HD. On the other hand, the mRNA levels of IL‐15 were not significantly different among individuals with each genotype of both SNPs. After incubation with recombinant human IL‐15, the proportions of Th17 cells in CD4+ cells were increased, and those of Treg cells in CD4+ cells were maintained. Our study indicates that the IL15 +96522A/C polymorphism correlates with the severity of HD, most likely by increasing Th17 cells.