The Journal of immunology : official journal of the American Association of Immunologists
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When administered parenterally, endotoxin stimulates the synthesis of IL-1, TNF-alpha, and IL-6. However, this initial injection induces tolerance; a second injection of endotoxin results in lower levels of circulating cytokines. In our study, five healthy male volunteers between the ages of 18 and 30 were injected with Escherichia coli endotoxin. ⋯ A decrease in cytokine synthesis was also observed using toxic shock syndrome toxin-1 as a stimulus: 57% for IL-1 beta (p = 0.06), 70% for TNF-alpha (p < 0.01), 56% for IL-6 (p < 0.05), and 71% for IL-8 (p = 0.001). When data were expressed as cytokine production per 10(6) PBMC, cells isolated 3 h after endotoxin injection synthesized significantly less stimulus-induced IL-1, TNF-alpha, IL-6, and IL-8 than did PBMC from saline-injected controls. We conclude that endotoxin tolerance is due, in part, to changes in the stimulus-induced cytokine response of circulating CD14+ cells.