Your current social status is influencing more than just your psychological well-being, but it also has physiological effects, determining how healthy you are. Being low on the social ladder can have a negative effect on the immune system. This has long been known, however there have been many questions about the biological mechanisms underlying these effects - until now.
A team of researchers turned to social groups of female rhesus macaques to answer these questions. Rhesus macaques are monkeys that live in hierarchical social groups, and are often used as a model to study the links between social status and physiology. Experimenters manipulated social rank by introducing monkeys into a new social group, and the order in which they were introduced determined their social rank - the first monkey introduced had the highest rank, and the last introduced had the lowest.
The researchers then drew blood from each monkey, and from the blood they purified immune cells called peripheral blood mononuclear cells (PBMCs). They measured gene expression levels in these cells to determine if variation in gene activity can be explained by social rank. They found 987 such genes, 535 of these genes were more highly expressed in higher ranked monkeys, and 452 of them were expressed more highly in lower ranked monkeys. This is significant because it shows that social rank is associated with gene activity in immune cells.
Furthermore, they found that dominance rank changes genes in such a way that just looking at gene expression data alone was enough to predict the monkey’s social rank with 80% accuracy. These findings prove that it is social environment that has an effect on gene expression, and not the other way around. However, they also found that this effect isn’t permanent - when a female monkey switched ranks, her gene expression levels did as well.
These differences in gene activity require certain regulatory mechanisms. The team of researchers found that variation in the expression levels can be partly explained by differences in tissue composition of each monkey. Variation in glucocorticoid (a type of hormone) regulation is another mechanism found that may account for the relationship between social rank and gene expression levels. There were also DNA methylation differences between different social ranks, suggesting that epigenetic changes might also be at work.
These findings are important implications, because they likely apply to human beings as well. This supports the idea that having a negative social environment may increase chances of infection and disease. But again, this effect is reversible - improving your social environment will have a positive impact on your immune system and overall well-being.