Neuroimmunomodulation: Strain Variation in Immune Response and Behavior Following the Death of Cage Cohorts

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Abstract
Strain differences in both immune function and behavior were observed following exposure of mice to the death of cage-cohorts. AKR/J, BALB/cN, and C3H/HeJ mice were exposed to a dead cohort for two hours at 48 hour intervals for 30 days. During this two hour period, AKR/J mice displayed intense fighting and mounting behavior. In addition, these mice attacked, cannibalized, and buried carcasses. Neither C3H/HeJ nor BALB/cN mice exhibited the complete repertoire of behaviors directed at either carcasses or cage-cohorts observed in AKR/J mice. After 15 exposures to the death of cage-cohorts, allogeneic cytotoxic T-lymphocyte (CTL) response was suppressed in AKR/J mice, but was enhanced or unchanged in C3H/HeJ and BALB/cN mice, respectively. Other immune parameters including natural killer (NK) cell activity, and lipopolysaccharide-stimulated B cell proliferation were unchanged in AKR/J mice but increased in BALB/cN mice exposed to the death of cage-cohorts for thirty days. These results suggest: 1) that both suppression of the CTL response and behaviors indicative of defensive burying in AKR/J mice may specifically be due to the loss of cage-cohorts, since they were not observed following exposure of these mice to the death of contraspecific animals; and 2) that both the behavioral repertoire and immune responses following exposure to the death of cage-cohorts may be strain dependent. This strain dependence may reflect differences in the ability to cope with the intermittent presentation of a stressor, and may explain, at least in part, variability in stress-induced changes in immune functions.