Effect of DNA methylation at the CTLA4 gene on the clinical status of autoimmune thyroid diseases

The pathogenesis and manifestation of autoimmune thyroid diseases (AITDs), Graves' disease (GD), and Hashimoto's disease (HD) are associated with T cell activation. Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) plays a crucial role in the regulation of T cell activation. DNA methylation levels of eight CpG sites in the CTLA4 gene and expression levels of soluble CTLA-4 were examined. Methylation levels of +22 CpG and CT60 CpG-SNPs in patients with GD and HD with the CT60 GG genotype were lower than those in control subjects. Methylation levels of the-15 CpG sites were lower in patients with intractable GD than those in GD patients in remission. These results suggest that demethylation of +22 CpG and CT60 CpG-SNPs may be associated with susceptibility to GD and HD in subjects with the CTLA4 CT60 GG genotype, and that demethylation of −15 CpG may be associated with the intractability of GD.