Inflammation and the Social Environment:
Sex differences in social modulation of inflammation
The social environment can markedly affect immune function and morbidity. Lonely individuals have poorer health outcomes. Sex differences exist in immune responses, but whether the social environment impacts the immune system differently in males and females is not well understood. Recent work in our lab has shown that group housing exacerbates inflammatory responses and sickness behaviors in female rats, but attenuates these responses in male rats. These sex differences are mediated in part by differential effects of the social environment on IL1<beta>, TNF<alpha> and IL-2 (pro- and anti-inflammatory cytokine) production. [PubMed]
The acute phase response to infection is reliably accompanied by decreases in social investigation; however, social behavior is commonly assayed in inescapable environments using unfamiliar social stimuli. Work in our lab uses familiar cage mates in a novel, semi-natural arena that affords the Focal animal exclusive control of social exposure, and the ability to avoid social interactions. In such environments, LPS-treated (sick) rats do not decrease the amount of time spent in social contact with cage mates. Rather, they oscillate between intense social interactions and complete social withdrawal. Inflammation gives rise to a transient state of social ambivalence -- characterized by a persistent motivation to engage in social contact, but also by increased avoidance of social environments Sickness behaviors are plastic and depend on the social context. [PubMed]
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