Social status and immunity

Dominance proved to be beneficial for health

Sofia Dolotovskaya, N+1

An international group of scientists has experimentally shown that the social status of macaques affects their immunity, and this effect is reversible: with an increase in status, the immune response suppressed in low-ranking monkeys returns to normal again. Article by Snyder-Mackler et al. Social status alters immune regulation and response to infection in macaques is published in the journal Science, its summary is given by EurekAlert! (Upward mobility boosts immunity in monkeys).

It is known that in social animals with a hierarchical organization of groups, social status affects health. Low social status is associated with chronic stress, which, in turn, causes disruption of a variety of body systems. Thus, using the example of rhesus macaques and crab-eating macaques, it was shown that low social status is associated with disorders of the cardiovascular system, the hypothalamus-pituitary-adrenal endocrine system (which regulates many processes in the body, including immune reactions, digestion and emotions), inflammation and gene expression in immune cells. However, despite a large number of studies demonstrating a correlation between social status and health, the direct impact of social status on health has never been demonstrated experimentally so far. The authors of the article decided to do this using the example of hierarchy in groups of rhesus monkeys.

In the experiments, the scientists used adult female rhesus monkeys living in a nursery at the Yerkes National Primate Research Center in the USA. In nature, rhesus macaques live in large mixed groups with a stable linear hierarchy, separate for males and females. In females, the hierarchy is more rigid and is inherited from mother to daughter, since females, unlike males, rarely migrate from one group to another. In captivity, however, the social status of macaques can be easily changed experimentally by relocating females from one group to another. At the same time, the earlier a female got into a new group, the higher her social status will be compared to females who got into this group later.

In the first part of the experiment, the researchers distributed 45 unrelated female macaques, who had never met each other before, into 9 groups. In each group, the macaques formed a hierarchy based on the order in which they got into the group. The groups were preserved for one year and then, in order to assess the impact of social status on health, they took a blood test from macaques and evaluated the expression of about 9 thousand genes. It turned out that females of different social status had a different relative number of immune cells of different types and gene expression in cells of different types. Thus, more than 1600 genes, especially in NK lymphocytes (natural killer cells) and T helper cells, were expressed differently depending on social status. This effect was especially noticeable when lipopolysaccharide, a component of the cell wall of gram–negative bacteria that causes a strong inflammatory response, was added to leukocytes taken from females with different social status in a test tube. In response to lipopolysaccharide, pro–inflammatory genes in the cells of subordinate females showed overexpression - in other words, "caused" inflammation. Interestingly, in response to infection, macaques with different social status activated different signaling pathways.

A year later, in the second part of the experiment, the authors redistributed the females into 9 new social groups. At the same time, the females who occupied a subordinate position in the old groups were relocated before everyone else, and the females who previously occupied a dominant position were relocated last. Thus, in the new groups, previously dominant females found themselves in a subordinate position, and previously subordinates – in a dominant position. After that, the authors again evaluated gene expression in macaque cells and the response to lipopolysaccharide.

It turned out that the expression patterns in the cells of females who were previously in a subordinate position and have now become dominant have changed accordingly – and vice versa. The same thing happened with the reaction of leukocytes to lipopolysaccharide.

The authors also traced which behavioral mechanisms were directly related to changes in gene expression in NK cells and T helper cells, where this effect was most pronounced. It turned out that grooming has the most pronounced effect on gene expression in NK cells (and to a lesser extent in T-helper cells). The aggression to which low-ranking monkeys are exposed also affected gene expression, but to a lesser extent. As scientists conclude, this suggests that the lack of positive social interactions is just as (or even more) important than social status as such.

The results of the work suggest that the effect of social status on health in social animals is not permanent, but reversible, at least in adult monkeys. In addition, the results confirm for the first time the direct influence of social status on immunity.

Recently, in experiments on mice, the opposite effect was demonstrated: it turned out that the immune system participates in the regulation of social behavior. In this work, mice with congenital severe combined immunodeficiency (damage to the acquired immunity system), unlike healthy animals, were no more interested in relatives than inanimate objects. This suggests that the link between immunity and social status works both ways.

Portal "Eternal youth" http://vechnayamolodost.ru  29.11.2016