TNF and periodontitis: It has also been shown that TNFA and COX2 CpG sites are hypermethylated and silenced in chronic periodontitis [110, 111], whilst in another study, hypomethylation at the promoter region of IFNY was demonstrated, which led to increased expression of IFN-γ in biopsies from tissues with periodontitis in comparison to tissues of a healthy periodontium [112].