This 2016 German review focused on how epigenetic processes affected the natural killer cell part of the immune system:

“Natural killer (NK) cells recognize and eliminate tumor- and virus-infected cells, parasites as well as certain types of bacteria. NK cell activity is related to a complex interaction of activating and inhibiting receptors on the NK cell surface.

During the development of HPCs [hemopoietic progenitor cells] to mature NK cells, the DNA demethylation of KIR [killer cell immunoglobin-like receptors] genes leads to KIR expression. But DNA methylation does not just determine which KIR gene is expressed, it also determines which allele expresses the KIR gene. KIR genes are also regulated by microRNA.

KIR genes exhibit highly similar histone acetylation signatures, which are typically found in expressed genes. This fact puts the KIR genes into a state of readiness for transcription which is depending on the DNA methylation as critical epigenetic modification in the regulation of KIR gene expression.

Epigenetic modifications have been reported to be involved in the expression of NKG2D, which is one the most important activating NK cell receptor.”

The reviewers included a section on NK cell activity and external stimuli. They summarized:

“The significance of the described findings is limited by study designs. Although human NK cells were frequently used, in most cases treatment took place in ex vivo experiments.”

The reviewers also provided a good three-paragraph explanation of general epigenetic mechanisms.

http://www.mdpi.com/1422-0067/17/3/326/htm “Natural Killer Cells—An Epigenetic Perspective of Development and Regulation”