SOCIAL CONFRONTATION IN MALE GUINEA-PIGS - BEHAVIOR, EXPERIENCE, AND COMPLEMENT ACTIVITY

Because aggressive encounters are known to affect immune function in r odents, we hypothesized that individual behavior and social experience would contribute importantly to the impact of confrontation on the ac tivity of the complement system (CA) in guinea pigs. CA was determined by lysis of Euglena gracilis cells (triggered by alternative pathway mechanisms). Males with different social experience were used: i) indi vidually housed males (IH), ii) socially less-experienced males (LE), raised in large groups in the absence of adult animals; and iii) socia lly experienced males (EX) with additional fighting experience. An IH and LE male, respectively, was introduced into a group of EX residents (consisting of one male and two females). During a 26-day confrontati on period the behavior of all animals was quantitatively recorded. IH and LE males showed a significant and persistent decrease in CA after confrontation (mean +/- SEM lysed cells/100 cells; IH: -16.5 +/- 4.0, LE: -16.5 +/- 3.5), whereas no significant changes from baseline were observed in EX males (-2.5 +/- 3.0). However, in social situations cha racterized by unstable dominance, EX males showed a lowered CA (-11.3 +/- 4.0) as well. Plasma cortisol concentrations determined in LE male s were significantly elevated 4 h after confrontation but did not corr elate with the long-term decrease in CA. The data indicate that the ac tivity of the complement system can be influenced by psychosocial stre ssors, and suggest the importance of prior social experience for the g uinea pig's ability to cope with social conflicts.