Social stress, dominance and blood cellular immunity.

The impact of chronic social coexistence on distribution and function of blood immune cells was examined in Long Evans rats. At the beginning of a 7 day period of chronic coexistence (confrontation), a wall was removed between two neighboring cages each consisting of a male-female pair. Winner and loser males were classified based on differences in their defensive behavior. On day 2 and 7 of confrontation, losers showed reductions in numbers of blood CD4 and CD8 T cells as well as profound suppression of in vitro NK activity and lymphocyte (LYM) proliferation. Numbers of granulocytes (GRAs) were more than doubled. Winner males showed similar immunological alterations only on day 2 of confrontation. On day 7 most changes were reversed. The persistent changes in loser males may reflect a less favorable state for effective immune response.