The protective role of endogenous cytokines in host resistance against an intragastric infection with Listeria monocytogenes in mice

It has been demonstrated that endogenous cytokines including gamma-interferon (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6) play a protective role but that IL-4 plays a detrimental role in systemic Listeria monocytogenes infection in mice, The diverse roles of IL-10 have been reported in antilisterial resistance. In this paper, we studied the role of endogenous cytokines in host resistance against an intragastric infection with L. monocytogenes in mice. The expression of cytokine mRNAs including IFN-gamma, TNF-alpha, IL-4, IL-6, or IL-10, which were amplified by reverse transcription-PCR, was observed in intestinal intraepithelial lymphocytes irrespective of L. monocytogenes infection. Increased numbers of L. monocytogenes were detected in the ileal contents of infected mice which received monoclonal antibodies (mAbs) against IFN-gamma, TNF-alpha, IL-4, IL-6, or IL-10. By contrast, mAbs against IL-4 or IL-6 showed little effect on the growth of L. monocytogenes in the mesenteric lymph nodes (MLNs), spleen, and liver, but anti-IFN-gamma mAb and anti-TNF-alpha mAb suppressed the defense in these organs. Anti-IL-10 mAb enhanced bacterial elimination from the MLNs but not from the spleen or liver. These results suggest that the role of endogenous cytokines may differ between systemic and intestinal defenses.