Immune responses following competitive water tests in two species of macaques

A panel of immune parameters (lymphocyte activation by mitogens, natural cytotoxicity, and differential cell counts) was assessed in socially housed pigtail and bonnet macaques 1 and 2 weeks before, 48 h after, and 1 and 2 weeks after a competitive water test. Species differences were found in both baseline measures and the responses to the test: Immune measures observed during baseline periods were lower in pigtail macaques. Furthermore, only the pigtail macaques showed changes in mitogen activation and cytotoxicity at 48 h post-test. Dominance-related behaviors affected these responses both within and across social groups. The species differences may be accounted for by the differences in the behavioral responses of the two species to the test: Pigtail macaques consistently contested access to the water during the test, whereas bonnet macaques did not. These results suggest that the immune system can be modulated by psychosocial behavioral systems, particularly during times of stress.