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Abstract
The study compares the impact of acute and chronic social confrontation on aspects
of blood cellular immunity in Long-Evans intruder rats. An adult male was introduced
for either 2 h or 48 h into a male-female resident group, which resulted in fights
for dominance. Thirty-eight of the 42 intruders became losers. For immunologic measurements,
blood samples were taken from the intruders before confrontation (baseline) and 2
h or 48 h after the beginning of confrontation. Two h of confrontation resulted in
increased granulocyte (+65%) and decreased lymphocyte numbers (-60%), as well as in
differential reductions in CD4, CD8, and B cell numbers. CD4/CD8 and T/B ratios were
elevated. T cell responsiveness to ConA was markedly suppressed in proliferation assays
using either whole blood (-90%) or PBMC (-50%). The direction of changes in leukocyte
and lymphocyte subsets after 48 h resembled in many aspects the 2 h changes, although
with lower magnitude. In contrast to acute stress, a lowered T/B cells ratio and unaffected
CD4/CD8 ratio was determined after 48 h. Proliferative response of T cells was lowered
by about 25% in the whole blood assay; but unaffected in the PBMC assay. Significant
correlations were found between the amount of submissive behavior displayed by the
losers and several immunologic measures after 2 h of confrontation. The data suggest
that acute and chronic stressful conditions may not necessarily result in similar
effects on immune functioning. This should be considered when evaluating the biologic
and evolutionary consequences of social stress-induced immune alterations.