[Host defense and endogenous interferon-gamma in the intestines during an oral infection with Listeria monocytogenes].

It is well known that IFN-gamma is crucial in the host defense against an intravenous infection with Listeria monocytogenes in mice. Recent studies have shown that listeriosis is caused by a food-born infection. Therefore, the production and role of IFN-gamma in the small intestines of intragastric infected-mice were investigated. On day 1 of infection, the number of bacteria cells in the feces peaked and endogenous IFN-gamma was detected in the small intestines by the immunohistochemical method, suggesting that host responses involving IFN-gamma production might occur in the early phase of infection in the small intestines. By FACS analysis, intraepithelial lymphocytes (IEL) were mainly CD3+CD8+ T cells and TCR-gamma delta+ cells were observed frequently in IEL. IFN-gamma producing cells could be detected in intestinal IEL of mice by ELISPOT assay. The analysis by reverse transcription-polymerase chain reaction analysis showed that IFN-gamma mRNA was detected in IEL of the infected mice, whereas the expression of IFN-gamma mRNA was suppressed in IEL of the mice treated with anti-CD8 mAb or anti-Thy1.2 mAb. These results suggested that Thy-1+CD+TCR-gamma delta+ T cells might be the principal source of IFN-gamma production in IEL of the infected mice. Administration of anti-IFN-gamma mAb resulted in suppression of anti-listerial resistance in the intestines. Furthermore, administration of anti-CD 8 mAb resulted in suppression of the local anti-listerial resistance on day 1 of infection. These results suggest that IFN-gamma is produced in IEL and might play a protective role in Listeria monocytogenes in the small intestines.