RÉSUMÉ
Resistance to facultative intracellular bacterial pathogens depends on acquired cell-mediated immunity and activation of macrophages by T- lymphocytes. Gamma interferon (IFN-gamma) is believed to be an important mediator of acquired cell-mediated immunity. In the present study, we evaluated the effect of Hochu-ekki-to (HET) on the survival rate and cytokine production with <i>Salmonella</i> infection model by using EL-4-bearing C57BL/6 mice. 1) When HET was administered orally to the tumor-bearing mice, it extended the survival time compared with non-treated controls in experimental infection by virulent strain 116-54. 2) The effect of HET on production of IFN-gamma in cultured splenocytes was tested by using the tumorbearing mice immunized with attenuated live SER strain. Spleen cells prepared from the mice treated with HET produced high levels of IFN-gamma compared with non-treated controls.<br>The results indicated that orally administered-HET enhanced protective ability to primary <i>Salmonella</i> infection and production of IFN-gamma accompanied by vaccination in EL-4-bearing C57BL/6 mice.