Bidirectional effects of interleukin-1 on immune responses in rhesus monkeys.
Physiological and pharmacological doses of recombinant human interleukin-1 (IL-1) were administered intravenously to juvenile rhesus monkeys in order to evaluate its effects on immune and endocrine activity. Mitogen-induced lymphocyte proliferation was increased following 1-ng and 1-microgram doses of IL-1, but decreased following 10- and 50-micrograms doses. Natural killer cell cytotoxicity was also significantly reduced at the 10-micrograms dose and tended to be below baseline at the 50-micrograms dose. These changes were associated with marked neutrophilia observed after administration of IL-1. These results indicate that peripheral administration of IL-1 can either enhance or inhibit the numbers and responses of immune cells in rhesus monkeys depending on the dose administered. These responses may have been the result of differential activation of the endocrine system, because levels of pituitary hormones in plasma increased progressively with increasing doses of IL-1. Thus, the extent to which a particular dose of IL-1 induces the release of pituitary-adrenal hormones may be related to the direction and magnitude of the resulting changes in immune activity.