EFFECTS OF ACUTE AND CHRONIC SOCIAL STRESS ON BLOOD CELLULAR-IMMUNITYIN RATS

The study compares the impact of acute and chronic social confrontatio n on aspects of blood cellular immunity in Long-Evans intruder rats. A n 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 o f 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 confron tation resulted in increased granulocyte (+65%) and decreased lymphocy te 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 respo nsiveness to ConA was markedly suppressed in proliferation assays usin g either whole blood (-90%) or PBMC (-50%). The direction of changes i n leukocyte and lymphocyte subsets after 48 h resembled in many aspect s 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 de termined 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 b ehavior displayed by the losers and several immunologic measures after 2 h of confrontation. The data suggest that acute and chronic stressf ul conditions may not necessarily result in similar effects on immune functioning. This should be considered when evaluating the biologic an d evolutionary consequences of social stress-induced immune alteration s. (C) 1998 Elsevier Science Inc.