Administration of bacterial lipopolysaccharide elicits circulating tumor necrosis factor-alpha in neonatal calves

The presence of tumor necrosis factor-alpha (TNF-alpha) during endotoxemia in ruminants has not been reported previously. In this study, we detected the in vivo release of bovine TNF-alpha by using WEHI-164 murine fibrosarcoma cells as targets in an 18-h cytotoxicity assay. Treatment of the WEHI-164 cells with 1 microgram of actinomycin D (dactinomycin) enhanced approximately twofold the susceptibility of the cells to TNF-alpha activity. TNF-alpha activity in sera from neonatal calves injected intravenously with 2.7 micrograms of Escherichia coli lipopolysaccharide (LPS) increased rapidly within the first 2 h postinjection and then declined until it was undetectable by 4 h postinjection. Sera taken before LPS administration had no TNF-alpha activity. LPS (10 micrograms/ml) and fetal, newborn, and pooled adult bovine sera alone and in combination had no direct cytotoxic effects on WEHI-164 cells. TNF-alpha cytotoxic activity is probably not due to the presence of interleukin-1 (IL-1), alpha interferon, or gamma interferon in the sera since recombinant human IL-1, natural bovine IL-1, and recombinant bovine alpha and gamma interferons had no direct cytotoxic effects on WEHI-164 cells. A monoclonal antibody that neutralizes recombinant human TNF-alpha significantly reduced the cytotoxic activity of sera from LPS-injected calves.