Exogenous cytokine modulation or neutralization of interleukin‐10 enhance survival in lipopolysaccharide‐hyporesponsive C3H/HeJ mice with Klebsiella infection

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Abstract
Klebsiella pneumoniae has been isolated from liver abscesses in patients with leukaemia or diabetes. The resistance of Klebsiella infection in lipopolysaccharide (LPS)-hyporesponsive mice is unclear. Female C3H/HeJ and C3H/HeN mice, 6–8 weeks old, were intraperitoneally (i.p.) injected with K. pneumoniae. The results showed that C3H/HeJ mice were 24 times more susceptible [lethal dose 50% (LD50) 250 colony-forming units] than C3H/HeN mice to K. pneumoniae infection. C3H/HeJ mice, uninfected or infected with K. pneumoniae, had higher liver interleukin (IL)-10 levels and IL-10 mRNA levels than C3H/HeN mice. Previously, pretreatment with IL-1β and tumour necrosis factor-α (TNF-α) protected C3H/HeJ mice from lethal bacterial infection. Therefore the effects of pretreatment with IL-1β and TNF-α or antimurine IL-10 antibody i.p. 1 hr before this infection in both strains of C3H mice were examined. Pretreatment with TNF-α or anti-IL-10 antibody enhanced the survival of both strains of mice. TNF-α, in combination with IL-1β, enhanced the survival and bacterial clearance better than single pretreatment in C3H/HeJ mice. Anti-IL-10 antibody increased bacterial clearance and significantly reduced liver cytokine mRNA levels in C3H/HeJ mice more than it did in the controls during infection. These results indicate that exogenous cytokine modulation or neutralization of IL-10 enhance the resistance of LD50 infection in C3H/HeJ mice.