Lipopolysaccharide (LPS)-reactive monoclonal antibodies fail to inhibit LPS-induced tumor necrosis factor secretion by mouse-derived macrophages.
Murine monoclonal antibodies (MAbs) reactive with epitopes on the O-side chain, core oligosaccharide, or lipid A of Escherichia coli and Salmonella minnesota lipopolysaccharide (LPS) were evaluated for their ability to inhibit LPS-induced tumor necrosis factor (TNF) secretion by mouse-derived RAW 264.7 macrophages. As little as 50 ng of purified LPS or lipid A stimulated macrophages to produce TNF detectable as cytotoxic activity in an L-929 fibroblast assay. None of 13 MAbs (concentration range, 0.1-1,000 micrograms/mL) blocked LPS- or lipid A (0.025-0.1 micrograms/mL)-induced TNF secretion by RAW 264.7 cells. Rabbit antiserum to synthetic lipid A also failed to block lipid A-induced TNF activity. Similar negative results were obtained when intact bacteria or membrane vesicles were used as TNF inducers. In contrast, polymyxin B, but not the less hydrophobic polymyxin B nonapeptide, produced almost complete inhibition of macrophage TNF secretion induced by LPS, lipid A, membrane vesicles, and intact bacteria. Thus, antibody reactivity with predominantly hydrophilic elements of LPS or lipid A may not affect hydrophobic interactions between lipid A and target cell membranes necessary and sufficient for the induction of TNF. These findings raise doubts concerning the existence of true endotoxin-neutralizing antibodies.
Chia
J K
JK
Department of Medicine, Uniformed Services, University of the Health Sciences, F. Edward Hebert School of Medicine, Bethesda, MD 20814.
Pollack
M
M
Guelde
G
G
Koles
N L
NL
Miller
M
M
Evans
M E
ME
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D004926:Escherichia coli; D007106:Immune Sera / Q000276:immunology; D008050:Lipid A / Q000276:immunology; D008070:Lipopolysaccharides / Q000276:immunology*; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D011112:Polymyxin B / Q000031:analogs & derivatives / Q000276:immunology; D012475:Salmonella; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000276:immunology
D000911:Antibodies, Monoclonal; D007106:Immune Sera; D008050:Lipid A; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; C038934:polymyxin B nonapeptide; D011112:Polymyxin B