IL10 and rheumatoid arthritis: However, DNA methylation levels are reported to be lower in RA patients with peripheral blood mononuclear cells (PBMC).309 Furthermore, in PBMC, abnormal cytosine methylation occurs in the promoter regions of IL-6 and IL-10, affecting transcription.310,311 Indeed, studies have shown that DNA methylation levels in T cells and monocytes in RA patients are lower than those in healthy subjects.312,313 Hypermethylation of the promoter region act as a marker of heterochromatin, which affects the binding of DNA to transcription factors and inhibits gene transcription.