Low social status 'damages immune function'
"Simply being at the bottom of the social heap directly alters the body," BBC News reports. The headline is based on a study in which researchers used female monkeys to simulate social hierarchies.
Monkeys of low social status were found to have biomarkers indicating poor immune function and possible increased vulnerability to infection.
The researchers arranged the monkeys into social groups and observed behaviours for two years to determine the social hierarchy. They then "mixed-up" the groups so that some of the monkeys were introduced into other groups as the "new girl". This effectively meant that the "newbie monkey" was stripped of all social status.
They then took blood samples to look at any effect this had on the immune system. The study found that social rankings in the monkey groups had an effect on white blood cells involved in fighting off disease. These findings suggested that the stress of a lower social ranking may increase inflammation and reduce resistance to infection and illness.
Although this study was specific to monkeys, the researchers argue that these findings are also applicable to humans. We do, after all, share much of our DNA with them.
Still, social status is a subjective concept not an objective fact. It only matters if you let it matter. As Eleanor Roosevelt famously said: "No one can make you feel inferior without your consent".
Where did the story come from?
The study was carried out by researchers from a number of international institutions in the US, Canada and Kenya, including Duke University, Emory University, the Universite de Montreal, and the Institute of Primate Research in Nairobi.
It was funded by grants, including one from the Canada Research Chairs Program.
The study was published in the peer-reviewed scientific journal Science.
BBC News and the Mail Online's reporting were fairly accurate. Although both outlets were quick to apply the findings to humans without highlighting the fact that social hierarchies, and their resulting influences in primates, may be different to those found in humans.
It could be the case that the primates in question – rhesus monkeys – were more sensitive to loss of social status than humans would be.
What kind of research was this?
This was an animal study which aimed to investigate how social status influences the immune system in captive adult female rhesus macaques.
Evidence has shown that social status is one of the strongest predictors of disease and death in humans. As rhesus macaques naturally form linear hierarchies (social groups where there is a clear pattern of rank), this study wanted to investigate the potential effects of social status by further exploring if and how it alters the immune system on a genetic level.
Animal studies are useful early stage research, especially in primates due to their biological similarity to humans. However, the social hierarchies observed in monkeys are not necessarily representative of those seen in humans.
What did the research involve?
The researchers conducted their investigation using 45 adult female rhesus macaques in captivity. In captivity, it's possible to manipulate the social hierarchies formed in these monkeys by the order in which the monkeys are introduced to new social groups. The monkeys were all unrelated and had never met each other before.
Nine groups containing five monkeys each were formed and these groups were maintained and observed (phase one). The monkeys were ranked where a higher status corresponded to a higher value. Social status was determined by observing whether an individual female was groomed by other monkeys (seen as a sign of high status) or conversely, harassed by other monkeys (a sign of low status).
After a year, these groups were rearranged by introducing the females one-by-one from phase one from either same or adjacent ranks into new groups (phase two). These were again followed for a year.
Alongside this qualitative observation, blood samples from the monkeys were analysed before and after each phase. The blood samples were analysed for any changes in the composition of white blood cells.
What were the basic results?
This study found a positive association between a monkey's rank and the activity of two specific types of white blood cell: T-helper cells and natural killer (NK) cells. T-helper cells play an overall role in regulating the immune system, while NK cells destroy infected or abnormal cells.
The researchers found that improvements in social status were reflected in the gene activity of these cells.
- The gene activity of NK cells was the most responsive to social status. Researchers identified 1,676 genes that were responsive to rank. This was closely followed by the gene activity of T-helper cells (n=284 genes).
- Weaker links were identified between monkey ranks and the activity of B-cells that produce antibodies (n=68 genes), and cytotoxic T-cells, another type of cell that targets and destroys abnormal cells (n=15 genes).
- There was no detectable effect on the expression of purified monocytes – a type of white blood cell that develop into macrophages that "eat" or engulf dead and damaged cells.
Additionally, they found the rate of received harassment contributed a considerable proportion of the gene activity of T-helper and NK cells (17.3% and 7.8% respectively). Grooming rates (how often, or not, an individual monkey was groomed by other monkeys) had more influence on the activity of NK genes (33.4% of all rank-responsive genes).
How did the researchers interpret the results?
The researchers say their results suggest that most effects of social status are immune cell type–specific. They conclude: "Our findings provide insight into the direct biological effects of social inequality on immune function, thus improving our understanding of social gradients in health."
Conclusion
The negative effect of social deprivation on health has long been recognised. This has often been attributed to an increase in unhealthy behaviours such as smoking, drinking too much alcohol, poor diet and being overweight.
However, this study looked at a slightly different aspect – observing the effects of social status through relationships with others – and suggesting this may have wider health effects than just influencing our lifestyle and health behaviours.
They found that a monkey's rank changed the gene activity of specific types of white blood or immune cell, and altered their numbers. Therefore, social status or social deprivation could directly influence the body's resistance to infection and disease.
One of the researchers, Dr. Noah Snyder-Mackler, told the BBC: "It suggests there's something else, not just the behaviours of these individuals, that's leading to poor health.
"Our message brings a positive counter to that – there are these other aspects of low status that are outside of the control of individuals that have negative effects on health."
These findings are interesting, but even though primates are generally quite similar to humans in both genetic make-up and social interactions, they aren't exactly the same.
Nevertheless, these results could help further our understanding of the effects of social factors on health in humans.
If social mobility does impact on human health by lowering feelings of self-esteem, there are other methods of increasing your self-esteem, that don't involve money or status.
These include connecting with others, learning new skills and taking time to help the less fortunate. Read more about boosting your self-esteem.
