Association of functional polymorphisms in promoter regions of IL5, IL6 and IL13 genes with development and prognosis of autoimmune thyroid diseases
To clarify the association of genetic producibility of interleukin (IL)‐5, IL‐6 and IL‐13, which are secreted by T helper type 2 (Th2), with the development and prognosis of autoimmune thyroid disease (AITD), we genotyped IL5−746C/T, IL6−572C/G and IL13−1112C/T polymorphisms, which are functional polymorphisms in the promoter regions of the genes regulating these cytokines. Fifty‐seven patients with intractable Graves' disease (GD), 52 with GD in remission, 52 with severe Hashimoto's disease (HD), 56 with mild HD and 91 healthy controls were examined in this study. The IL13−1112T allele, which correlates with higher producibility of IL‐13, was more frequent in patients with GD in remission than in those with intractable GD [P = 0·009, odds ratio (OR) = 3·52]. The IL5−746T allele, which may correlate with lower levels of IL‐5, was more frequent in patients with GD in remission than controls (P = 0·029, OR = 2·00). The IL6−572G allele carriers (CG and GG genotypes), which have higher producibility of IL‐6, were more frequent in AITD patients (P = 0·033, OR = 1·75), especially in GD in remission (P = 0·031, OR = 2·16) and severe HD (P = 0·031, OR = 2·16) than in controls. Interestingly, both allele and genotype frequencies of Th2 cytokine genes were similar between GD and HD patients. In conclusion, functional polymorphisms in the genes encoding Th2 cytokines are associated differently with the development and prognosis of AITD from each other.