The role of lipopolysaccharide binding protein in resistance to Salmonella infections in mice.
Polymorphonuclear leukocytes (PMN) and LPS-binding protein (LBP) are both components of the innate immune system. LBP is a plasma protein that binds to lipid A and enhances the biological activity of LPS 100- to 1000-fold. Recently it was reported that LBP-deficient mice are more susceptible to Salmonella typhimurium infection. Here we report that LBP KO mice are more susceptible to Salmonella peritonitis, but not to oral or i.v. infection. LBP knockout (KO) mice responded normally to i.p. injections of Staphylococcus aureus and casein, but not to i.p. injection of S. typhimurium or Salmonella LPS. Mice with a mutation in Toll-like receptor 4 (C3H/HeJ) have a similar defect in PMN chemotaxis. In normal mice S. typhimurium stimulated production of the CXC chemokines macrophage inflammatory protein-2 and cytokine-induced neutrophil chemoattractant, but levels of cytokine-induced neutrophil chemoattractant and macrophage inflammatory protein-2 were greatly reduced in the LBP KO mice. LBP KO mice pretreated with casein to attract PMN in an LBP-independent manner were more resistant to Salmonella infection, but neutropenic mice were not protected by casein. Splenic TNF-alpha mRNA levels were also lower in LBP KO than in control mice infected with Salmonella. Since TNF-alpha can activate PMN, LBP KO mice may have both fewer and less active PMN in the first few hours after Salmonella are injected, making LBP KO mice more susceptible. This work confirms the importance of PMN in resistance to Salmonella infections and shows that this is facilitated by LBP.
Fierer
Joshua
J
Infectious Diseases Section, Veterans Affairs Healthcare System, San Diego, CA 92161, USA. jfierer@ucsd.edu
Swancutt
Mark A
MA
Heumann
Didier
D
Golenbock
Douglas
D
D000209:Acute-Phase Proteins; D000284:Administration, Oral; D000818:Animals; D000942:Antigens, Bacterial / Q000008:administration & dosage / Q000276:immunology; D001202:Ascitic Fluid / Q000276:immunology / Q000473:pathology; D002352:Carrier Proteins / Q000096:biosynthesis / Q000097:blood / Q000235:genetics / Q000502:physiology*; D004751:Enteritis / Q000235:genetics / Q000276:immunology; D020022:Genetic Predisposition to Disease; D007113:Immunity, Innate / Q000235:genetics; D007274:Injections, Intraperitoneal; D007275:Injections, Intravenous; D008070:Lipopolysaccharides / Q000378:metabolism*; D008562:Membrane Glycoproteins; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D018345:Mice, Knockout; D009503:Neutropenia / Q000235:genetics / Q000276:immunology; D010538:Peritonitis / Q000235:genetics / Q000276:immunology / Q000473:pathology; D012481:Salmonella Infections, Animal / Q000235:genetics / Q000276:immunology* / Q000401:mortality; D012486:Salmonella typhimurium / Q000276:immunology; D000099231:Lipopolysaccharide-Binding Protein
D000209:Acute-Phase Proteins; D000942:Antigens, Bacterial; D002352:Carrier Proteins; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D000099231:Lipopolysaccharide-Binding Protein