Hypermethylation of IL-10 gene is responsible for its low mRNA expression in Behçet's disease.

Interleukin-10 (IL-10), produced generally by monocyte, T helper type 2 (Th2), and regulatory T cells (Treg), plays a central role in controlling inflammatory responses and regulating the immune response of the IL-10 mRNA expression. It is significantly down-regulated in many autoimmune diseases such as Behçet's disease; this is mostly associated with more aggressive complications. Nevertheless, the essential molecular process for its low expression has not been completely realized. The aim of this project was attempted to estimate the gene expression, promoter methylation, and protein levels to IL-10's down-regulated expression. In this study, blood samples from 51 (4 missed) patients and 63 (2 missed) healthy controls were taken, with the mononuclear cells isolated by the Ficoll Protocol. DNA and RNA were then subsequently extracted. Promoter methylation levels were evaluated by MeDIP-qPCR. Following this, the extracted RNA was converted to cDNA using the RT-PCR method, with the expression of IL-10 later evaluated by Real-time PCR. And then, serum levels of IL-10 were measured using ELISA method. As we expected, the expression level of the IL-10 gene was seen to significantly decline in the patient group in comparison to the control. Also, the rate of promoter methylation was significantly higher in the IL-10 mRNA low expression group (patient group) compared to its high expression group (healthy group) (P < 0.001). We revealed that hypermethylation of promoter region was the principal defect for the IL-10 mRNA low expression in patients with Behçet's disease.