Social isolation disrupts innate immune responses in both male and female prairie voles and enhances agonistic behavior in female prairie voles (Microtus ochrogaster)

Psychosocial stress, specifically social isolation, is an important risk factor for the development of a variety of psychological and physiological disorders. Changes in immune function have been hypothesized to mediate this relationship. The current study used the prairie vole (Microtus ochrogaster) model of isolation-induced depressive-like behavior to test whether social isolation led to changes in innate immune function. Specifically, we used hemolytic complement (CH50) and bacteria killing assays to assess innate immunity, in paired or singly housed male and female prairie voles. Further, in a second experiment we tested whether females exposed to an additional short-term social stressor, a resident-intruder trial, would show changes in immune function as well as enhanced hypothalamic pituitary axis (HPA) activity as indicated by elevated plasma corticosterone levels. Socially isolated animals, regardless of sex, had significantly reduced CH50s and bacteria killing ability. Socially isolated females exposed to a resident-intruder stressor also showed reduced CH50s and bacteria killing ability as well as significant increases in aggressive behavior, however, they did not show elevated circulating corticosterone levels. Collectively, these data will help inform our understanding of the relationship between social isolation and physiological and psychological health.