Monoclonal antibody to endotoxin core protects mice from Escherichia coli sepsis by a mechanism independent of tumor necrosis factor and interleukin-6.

To study the role of cytokines as mediators of endotoxin-induced shock, the serum levels of tumor necrosis factor (TNF) and interleukin-6 (IL-6) were compared in mice receiving either a monoclonal antibody to endotoxin core (clone 20), an irrelevant monoclonal antibody (A1), or culture media (DMEM/FCS) alone before lethal challenge with live Escherichia coli O111:B4. Clone 20 given 1.5 h before the bacterial challenge protected mice from death (mortality at 48 h 3% vs. 87%, P less than .001). The pattern of IL-6 release was indistinguishable in clone 20 recipients and controls: The area under the curve (AUC) for 5 h was 1.22 +/- 0.07 x 10(6), 1.03 +/- 0.17 x 10(6), and 1.22 +/- 0.07 x 10(6) units/ml for clone 20, A1, and DMEM/FCS, respectively. Similarly, the timing and extent of TNF release in the serum was virtually identical in clone 20 recipients that survived and control animals that died. AUC for 5 h was 30.8 +/- 4.0 x 10(3), 28.1 +/- 1.1 x 10(3), and 30.4 +/- 4.7 x 10(3) ng/ml in clone 20, A1, and DMEM/FCS recipients, respectively. Thus, TNF and IL-6 appear insufficient to cause death in this model of experimental gram-negative shock.