Another important aspect with stressful environment there is evident release of neuroendocrine stress hormones that signal epigenetic modification in the immune system. For example, Krukowski et al. (2011) evaluated epigenetic mechanisms that may underlie the effect of stress hormones specifically glucocorticoids on natural killer cells cells. They found glucocorticoids significantly dysregulated NK cell function through an epigenetic mechanism, modification of histone acetylation status. This epigenetic modification decreases the expression of effector proteins necessary immune function of the activity of NK cells (Krukowski et al., 2011).
These finding demonstrate that on o fthe MZ twins could experience epigenetic modifications triggered by stressful environment. There is little evaluation of stress and epigenetic modification in humans; however, preliminary evidence revealed that for individuals with posttraumatic stress disorder externally experienced traumatic event induces downstream alterations in immune function by reducing methylation levels of immune-related genes (Udin et al., 2010).
These results propose that traumatic event to trigger long-lasting epigenetic modification in immune function through brain-immune interactions. Thus, this could be further explored in MZ twins by controlling for genetic differences and investigating comparisons among MZ twin pairs. Taken together, the evidence are highlight the need for more research in stress models in human that relate to the effect of the environment and increases susceptibility to disease related to stress in vulnerable populations.
Additionally, the stress of low socio-economic status s associated with a shortened life expectancy and appears to have an impact on telomere length. Cherkas et al. (2006) tested the hypothesis that socio-economic status is associated with telomere attrition independent of known risk factors influencing the aging process in 1552 female MZ twins. They measured the rate of white-blood-cell telomere attrition as a biological indicator of human aging. Then, a discordant twin analysis was completes on a subset to verify findings, which revealed that WBC telomere length was highly variable but significantly shorter in lower socio-economic status groups (Cherkas et al., 2006).