The network of immune system and nerve system in host defense to bacterial infections

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The network is formed between immune system, nerve system, and endocrine system. We were interested in the interaction between immune system and nerve system in bacterial infections. We chose the neuropeptides such as substance P (SP) and vasoactive intestinal peptide (VIP) as the parameter of nerve system. We investigated the induction of SP and VIP en the livers of mice which were infected intravenously with Listeria monocytogenes or Tsukamullela paurometabolum.In the studies using an immunohistochemical technique, neither SP nor VIP was detected in the livers of uninfected mice. VIP,but not SP was detected around the blood vessels and in the surrounding infiltrating cells of livers obtained from Listeria-infected mice. In contrast, SP,but not VIP,was detected in the granuloma-like lesions of livers obtained from Tsukamullela-infected mice. These result suggest that the selective induction of SP and VIP might occur, depending on bacteria infected, and that the neuropeptides might be secreted by the inflammatory cells. In the studies using reverse transcription-PCR,propre VIP mRNA was induced in parallel with the growth of Listeria cells in the livers.These results demonstrate that the neuropeptides might be involved in the inflammatory process and/or the host defense in bacterial infections.