April 10, 2012
Researchers Find Link Between Social Status, Immunity in Monkeys
Changes in a female monkey's social status lead to changes in her immune system, and researchers writing in this week's edition of the Proceedings of the National Academy of Sciences (PNAS) Early Edition suggest that the findings may be applicable to humans as well.
The research, which was led by Jenny Tung, currently a visiting assistant professor in Duke University's evolutionary anthropology department and a postdoctoral researcher at the University of Chicago at the time of the study, is said to be the first to utilize an experimental approach to analyze how gene expression patters across a range of genes correlates with the social dominance of an animal, the Durham, North Carolina-based school said in a press release on Monday.
Emory University, home of the Yerkes National Primate Research Center (where the research was conducted), said that Tung and her colleagues studied 49 female rhesus macaques and could determine the social rank of each macaque, without looking at the animal itself, simply by looking at their pattern of genetic activity.
By examining gene expression levels in their immune cells, the experts could predict whether each animal was high (rank 1 or 2), middle or low (rank 4 or 5) with 80 percent accuracy, they said in a separate media advisory.
"To test how gene expression would differ when a monkey's rank changed, the scientists at Yerkes took the female macaques from their native groups and constructed 10 new social units, where rank was determined based on how early a female was added to her unit," Duke University said.
"Tung and her collaborators then took blood samples from the monkeys and isolated the white blood cells. The results show that lower-ranking monkeys had lower levels of a certain kind of T cell and showed signs of exposure to chronic stress, two findings that helped explain why their genes turned on and off differently than high-ranking monkeys," they added.
The researchers also looked for changes within the macaques DNA, and discovered that the dominance within the group correlated with the presence and/or absence of methyl groups, a substance which helps in turning genes on or off. When a female moved from a lower social rank to a higher one, their immune systems displayed a rapid response, and the once low-ranking animals would quickly genetically resemble higher-ranking ones.
"In the wild, females would not ordinarily leave the social group they were born into. They inherit their social rank from their mothers. But in this unnatural situation, order of introduction determines rank -- the newcomer is generally lower status," Tung in a statement.
"There's a spooky side to this kind of research, in that an individual's social rank is partially determining health status. But there's also a hopeful side," she added. "For the“¦ females that changed ranks, their gene status changed with them. They're not stuck in place, and I think that says something more broadly about the capacity for change."
Tung and her colleagues plan to continue studying the link between social rank and stress in macaques, as well as their impact on the creature's immune systems and their susceptibility to infections. Furthermore, the researchers suggest that their findings could also have implications for how the stress of low socioeconomic conditions could affect the health and wellbeing of people, particularly after a shift in their status, Emory University said.