In addition to activating T and B lymphocytes, interleukin 1 (IL-1) induces several hematologic and metabolic changes typical of host responses to infection and injury. We now report a new biological property, namely, the induction of hypotension. Rabbits given a single intravenous injection of recombinant human IL-I-beta (5 isg/kg) rapidly developed decreased systemic arterial pressure, which reached the lowest levels after 50-60 min and slowly returned to pre-IL-I values after 3 h. Associated with the hypotension, systemic vascular resistance and central venous pressure fell, while cardiac output and heart rate increased. These responses were prevented by ibuprofen given 15 min before the IL-i. A bolus injection of IL-I followed by a 2-h infusion sustained the hypotension and was associated with leukopenia and thrombocytopenia. Ibuprofen given at the mid-point of the infusion reversed the changes in all hemodynamic parameters, but had no effect on the leukopenia or thrombocytopenia. Tumor necrosis factor (TNF) also induced a shock-like state in rabbits. When the dose of IL-1 or TNF was reduced to 1 ,ug/kg, no hemodynamic changes were observed; however, the combination of these low doses of both cytokines resulted in a profound shock-like state including histological evidence of severe pulmonary edema and hemorrhage. Pretreatment with ibuprofen prevented the hemodynamic, leukocyte, and platelet changes induced by the low-dose cytokine combination, and ameliorated the pulmonary tissue damage.These results demonstrate that IL-1, like TNF, possesses the ability to induce hemodynamic and hematological changes typical of septic shock, and that the combination of IL-I and TNF is more potent than either agent alone. These effects seem to require cyclooxygenase products, and suggest that intravenous cyclooxygenase inhibitors may be of therapeutic value in patients with IL-i/TNF-mediated shock.

We have demonstrated that purified C5a is a potent stimulus to human PBMC secretion of TNF-alpha, IL-1 beta, and IL-1 alpha, which proceeds in a dose-dependent fashion. At a given concentration of C5a, TNF-alpha and IL-1 beta secretion did not differ significantly; both were secreted in significantly greater quantity than IL-1 alpha. Clinical conditions such as Gram-positive and Gram-negative bacterial infections, trauma, and immune complex diseases activate complement. Through the mediation of TNF and IL-1 secreted in response to C5a, these diverse disorders can share common features of fever, coagulopathy, acute phase protein production, and disordered metabolism.

US is reliable for the detection of injuries and the identification of solid-organ injuries despite its poor sensitivity for intestinal injuries.

Recombinant human interleukin-1 (IL-1), injected into rabbits, induces the synthesis of endogenous IL-1. Also, IL-1 induces its own gene expression and synthesis in human peripheral blood mononuclear cells (PBMC). In this study, tumor necrosis factor-alpha (TNF-alpha) production by PBMC of 40 individuals stimulated with IL-1 alpha or IL-1 beta was determined by specific radioimmunoassay (RIA). After 3 h of PBMC incubation with IL-1, TNF-alpha mRNA was detected. IL-1 alpha stimulated both IL-1 beta and TNF-alpha, but there was no correlation in the amount of TNF-alpha or IL-1 beta synthesized in the PBMC of 29 individuals. IL-1-stimulated adherent cells produced approximately 50% more TNF-alpha than did unfractionated PBMC. Coincubation with interferon-gamma (IFN-gamma) did not change the amount of IL-1-induced TNF-alpha, whereas in the same culture IFN-gamma inhibited (greater than 70%) IL-1-induced IL-1 production. Endogenous pyrogen and TNF-like activity were detected in the sera of rabbits 3.5 h after injection of either IL-1 alpha or -1 beta. These studies demonstrate that IL-1 induced TNF-alpha production in vivo and in vitro.