Cross-reactive murine monoclonal antibodies directed against the core/lipid A region of endotoxin inhibit production of tumor necrosis factor.

Two murine monoclonal antibodies (mAbs) directed against the core/lipid A moiety of lipopolysaccharide (endotoxin, LPS) were derived from mice immunized with either Escherichia coli J5 or Salmonella minnesota Ra, Rb, Rc, or Re heat-killed organisms or LPS. These mAbs were selected on the basis of their ability to cross-react against a panel of gram-negative bacterial LPS using Western immunotransblot analysis. We hypothesized that these anti-LPS mAbs directed against the conserved core region of LPS would inhibit LPS-induced macrophage tumor necrosis factor (TNF) production by neutralizing LPS derived from different gram-negative bacteria. To test this hypothesis, unelicited peritoneal macrophages were treated with either mAb 5G11 (deep core/lipid A specificity, broad LPS cross-reactivity) or mAb 5B11 (intermediate core specificity, limited LPS cross-reactivity). Macrophages were then challenged with a panel of LPS, and TNF activity was measured by the use of the L929 cytotoxicity assay. MAb 5G11 significantly inhibited TNF production against a panel of different types of LPS, but mAb 5B11 did not. In addition, mAb 5G11 did not inhibit TNF production due to isolated lipid A stimulation, suggesting that mAb 5G11 neutralized LPS by binding primarily to the deep core region of LPS. MAb 5G11 was also able to inhibit TNF production if added within 10 min of LPS stimulation but had no effect at 30 min, suggesting that macrophage stimulation may be irreversible during even the early stages of the response to LPS.(ABSTRACT TRUNCATED AT 250 WORDS)