Molecular origins and outcomes of status and stress in primates

Social dominance hierarchies are common in human and nonhuman animals and profoundly affect the behavior, health, and well-being of every member of a community. Research on diverse species has expanded our understanding of how ecological and social forces shape interactions influencing social status, behavior, and the underlying biology (1, 2). Across vertebrates, repeated social subordination (equivalent to low status) has been shown to result in depression-like phenotypes (3⇓⇓–6). It has also been suggested that the gene modules controlling responses to repeated social defeat are evolutionarily conserved (7, 8). The use of a comparative framework combined with genome-scale approaches provides an unparalleled opportunity to examine the effects of social status on behavior and health. In PNAS, two new studies (9, 10) use advanced genomic methods to investigate the effects of social status on immunity and stress physiology by examining gene regulation in blood cells of two different primate species.

To uncover the molecular mechanisms involved in social status and stress, Snyder-Mackler et al. (9) examine social interactions in 45 captive, unrelated female rhesus macaques. Female rhesus macaques exhibit stable, linear social hierarchies (based on kin-directed nepotism). Low-ranking females receive increased harassment and decreased social support (e.g., grooming) and exhibit elevated levels of circulating glucocorticoids (GCs) (e.g., cortisol). Previous research by Snyder-Mackler et al. (11) demonstrated that low-ranking females exhibit a proinflammatory profile in their blood cells compared with high-ranking females (Fig. 1A). Importantly, when these animals received an immune challenge in the form of the bacterial stimulant of infection [lipopolysaccharide (LPS)], rank differences in gene expression were amplified (Fig. 1B). In their new study, Snyder-Mackler et al. (9) evaluate GC signaling using in vitro treatment with the synthetic GC dexamethasone (Dex). Peripheral blood mononuclear cells collected from individual rhesus macaques were incubated with or …

↵¹To whom correspondence should be addressed. Email: hans{at}utexas.edu.