Effects ofin vivo endotoxin infusions onin vitro cellular immune responses in humans

Abstract

Studies of the immune response of patients following major injury have identified significant abnormalities, some of which may be due to the effects of endotoxin. To evaluate the effect of endotoxin on the immune system without conflicting variables, we studied 18 normal, healthy male volunteers each on two occasions. In one study, Escherichia coli endotoxin was administered intravenously at a dose of 4 ng/kg. In the other, saline was given. Blood for immune function studies was obtained at either 0, 4, or 24 hr (seven volunteers), 0, 1, and 4 hr (five volunteers), or 0, 4, and 6 hr (six volunteers) postinfusion. Peripheral blood mononuclear cells (PBMC) were isolated and adjusted to the same concentration. Measurements following endotoxin infusion were compared with those of the same volunteers following saline infusion and with those from normal ambulatory laboratory volunteers. Interleukin 1 (IL-1) production by adherent cells was significantly reduced at 1 hr post endotoxin infusion. Significant decreases in number of mononuclear cells, response to phytohemagglutinin (PHA), and production of IL-2 and IL-1 were observed by 4 hr after endotoxin infusion. No significant changes in percentages of monocytes, lymphocytes, or CD3, CD4, or CD8 lymphocytes were observed at any time. By 24 hr postinfusion all values had returned to normal or, in some cases, supranormal levels. Response to PHA by PBMC from volunteers 4 hr following endotoxin was completely restored by in vitro addition of recombinant human IL-2 but was only marginally improved by IL-1. In vitro addition of indomethacin to PBMC cultures responding to PHA reduced the suppression observed after in vivo endotoxin but also was not as effective as IL-2. In a fourth study, seven volunteers were treated as above either with two doses (800 mg each) of the cyclooxygenase inhibitor ibuprofen before endotoxin infusion or with ibuprofen alone. Ibuprofen pretreatment completely restored the PBMC response to PHA to normal and caused a significant decrease in the endotoxin-induced suppression of IL-2 production. However, the decrease in circulating PBMC number and adherent cell secretion of IL-1 was not affected by inhibition of the cyclooxygenase pathway. These results suggest that endotoxin has immunomodulatory effects on both adherent mononuclear-cell and T-lymphocyte function and that more than one mechanism is involved.

RETRACTED: Low-dose endotoxin elicits variability in the inflammatory response in healthy volunteers

“…Many previous studies have used the traditional model of 4 ng/kg to gain information on inflammatory mediators, the mechanism of cellular activation and the simultaneous administration of agents that may modify inflammation. [8][9][10][11][12][13][14][15][16][17][18][19] However, this dosing regimen might not be the best model in which to test endotoxin and inflammatoryrelated therapies. The primary aim of this study was to characterise endotoxin dosing regimens that could elicit variability in systemic inflammation in some subjects but not in others.…”

Immune Response in Hepatitis B Virus Infection

“…Despite the high level of purity of these preparations, contaminants from bacteria or enzymes cannot be ruled out. For example, the phenomena of lipopolysaccharide (LPS)-induced tolerance of antigen-presenting cells following stimulation with TLR agonists may have influenced the outcome of some experiments (Rodrick et al 1992;Granowitz et al 1993). Moreover, it is important to consider that, in CHB patients with chronic liver disease, the presence of high doses of circulating antigens is often linked with immunosuppressive cytokines (IL-10) (Das et al 2012) or liver enzymes (i.e., arginase), known to alter the function of different components of cellular immunity (Das et al 2008;Sandalova et al 2012).…”

Extended in Vivo Pharmacodynamic Activity of E5564 in Normal Volunteers with Experimental Endotoxemia

“…Expected LPSinduced events occurred in subjects who received placebo and LPS. These include chills, fever, tachycardia, nausea, headache, myalgia, leukopenia followed by leukocytosis, and increased plasma cytokines and C-reactive protein and mild decreases in blood pressure, and alterations in WBC counts Revhaug et al, 1988;Suffredini et al, 1989a,b;Rodrick et al, 1992;Parrillo, 1993;Hochstein et al, 1994;Lynn et al, 2003). LPS-induced alterations in body temperature and heart rate and symptoms resolved within 12 h after dosing and other signs resolved somewhat later.…”

“…Administration of LPS to normal volunteers has been reported to induce a syndrome characterized by signs and symptoms, including chills, fever, tachycardia, myalgia, headache, nausea, and vomiting that occur and resolve within 12 h of receiving 4 ng/kg LPS Suffredini et al, 1989a,b;Parrillo et al, 1990;Rodrick et al, 1992;Parrillo, 1993;Hochstein et al, 1994;von der Mohlen et al, 1995). Occurrence of these and other adverse events were collected by regular elicitation and spontaneous complaints.…”

“…Endotoxin (lipopolysaccharide from Gram negative bacteria, or LPS) has been implicated as a major cause of this syndrome (Suffredini et al, 1989a,b;Parrillo et al, 1990;Danner et al, 1991;Rodrick et al, 1992;Taveira da Silva et al, 1993;Opal et al, 1999). E5564 is a synthetic second generation analog of the lipid A component of LPS (Rossignol et al, 1999) that has demonstrated potent anti-LPS activity in a variety of in vitro and in vivo model systems (Mullarkey et al, 2003).…”