Effect of maternal separation on the complement system and antibody responses in infant primates

Hemolytic complement activity and complement protein levels were evaluated before and after psychological disturbance in the squirrel monkey. Significant increases in hemolytic complement activity were observed following separation of 6-month-old infants from their mothers. Complement protein levels were generally correlated with hemolytic activity, but did not show the same pattern of change. C3 levels did not change consistently after maternal separation, while C4 decreased significantly on Day 7, and then began to return toward basal levels by Day 14. The alterations in complement activity were associated with elevated adrenal hormone secretion, but were not directly correlated with plasma cortisol levels. A second experiment showed that increased hemolytic complement activity also occurred in juvenile squirrel monkeys following 4-hour to 7-day removals from a peer group. The effect of maternal separation on antibody responses to viral challenge was evaluated in a third experiment. Separated infant squirrel monkeys mounted a smaller antibody response than did control infants that remained with their mothers. A similar decline in antibody responses was observed in separated rhesus macaque infants, but the effect was less marked in this species. Thus, the strong effect of psychological disturbance on immunity in the squirrel monkey is probably related to its prolonged endocrine responses.