Previous research has revealed increased expression of IFIT1, IRF7, MX1, OAS1, USP18, and RSAD2 in one or more of the four autoimmune diseases, which is consistent with an inverse correlation between gene expression and methylation (Wilson et al., 2007), thus providing further evidence for DNA methylation’s involvement in the regulation of these genes. Here, USP18 is linked to autoimmune disease.