Different sensitivity of complement to Salmonella typhimurium accounts for the difference in natural resistance to murine typhoid between A/J and C57BL/6 mice.
The difference in natural resistance to Salmonella typhimurium between S. typhimurium-resistant A/J mice and S. typhimurium-susceptible C57BL/6 mice was analyzed. In both strains, the growth of S. typhimurium was controlled in the spleen until 48 hr of infection, while serum C3b levels were increased in A/J mice immediately after infection but not in C57BL/6 mice. Incubation of A/J mouse serum with S. typhimurium or its lipopolysaccharide (LPS) generated sufficient amounts of C3b, but that of C57BL/6 mouse serum with them did not. A/J macrophages had higher intracellular killing activity in vitro than did C57BL/6 cells against S. typhimurium pre-opsonized with each corresponding fresh serum. However, the cells from both mice exhibited a similar level of killing activity against S. typhimurium pre-opsonized with fresh A/J serum or rabbit complement. The resistance of C57BL/6 mice was significantly increased by opsonizing S. typhimurium with fresh A/J serum or rabbit complement before inoculation. The serum level of interferon-gamma (IFN-gamma) in A/J mice was 2.7 times as high as in C57BL/6 mice at 48 hr post-infection. Recombinant murine IFN-gamma enhanced the intracellular killing activity of macrophages from both mice when S. typhimurium was pre-opsonized with fresh A/J serum but not with fresh C57BL/6 serum. These findings suggest that A/J macrophages exhibit maximal killing activity against A/J serum-opsonized S. typhimurium in vivo when the cells are activated with IFN-gamma. Therefore, the rapid and sufficient activation of complement by Salmonella LPS may render A/J mice more resistant against murine typhoid.
Nakano
A
A
Department of Bacteriology, Nara Medical University, Japan.
Kita
E
E
Kashiba
S
S
D000818:Animals; D003167:Complement Activation / Q000276:immunology; D003179:Complement C3b / Q000276:immunology*; D003602:Cytotoxicity, Immunologic / Q000276:immunology; D005260:Female; D007113:Immunity, Innate; D007371:Interferon-gamma / Q000097:blood; D008070:Lipopolysaccharides; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008805:Mice, Inbred A; D008810:Mice, Inbred C57BL; D010587:Phagocytosis / Q000276:immunology; D012481:Salmonella Infections, Animal / Q000276:immunology*; D012486:Salmonella typhimurium / Q000254:growth & development / Q000276:immunology*; D013047:Specific Pathogen-Free Organisms; D013154:Spleen / Q000276:immunology / Q000382:microbiology; D014435:Typhoid Fever / Q000276:immunology*
D008070:Lipopolysaccharides; D003179:Complement C3b; D007371:Interferon-gamma