The role of interleukin 2 in hemorrhage-induced abnormalities of lymphocyte proliferation.

Depression of lymphocyte proliferative response occurs after trauma and hemorrhage. Because abnormalities in production or utilization of interleukin 2 (IL-2) can result in depression of mitogen-induced lymphocyte proliferation, we investigated the effects of unanesthetized hemorrhage on the generation of IL-2 by rat peripheral blood lymphocytes and the response of these cells to exogenous IL-2. Two hours after loss of 30% of total blood volume, IL-2 production was reduced by greater than 90%. Return to normal levels of IL-2 generation occurred by 48 hr after hemorrhage. Addition of purified rat IL-2 to cultures of phytohemagglutin-stimulated peripheral blood lymphocytes obtained from normal animals resulted in suppression of the proliferative response. Exogenous IL-2 produced a similar degree of suppression in the proliferation of cells obtained from hemorrhaged animals. These results show a profound hemorrhage-induced suppression of IL-2 generation, but no benefits of exogenous IL-2 in improving the depressed lymphocyte proliferative response that exists after hemorrhage.