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Abstract
The present study examines the role of liver macrophages (Kupffer cells), of C57BL/6 mice, as effector cells responsible for the killing of Entamoeba histolytica trophozoites in vitro. Interferon gamma (IFN-$\gamma$) and tumor necrosis factor alpha (TNF) were each shown to endow murine Kupffer cells with significant amoebicidal activity. Interferon gamma alone was not able to activate Kupffer cells to amoebicidal state. However, IFN-$\gamma$ and lipopolysaccharide (LPS) acted synergistically in this phenomenon. It seems that the acquisition of amoebicidal activity is associated with the involvement of hydrogen peroxide, because the addition of catalase partially decreases the killing of this parasite by Kupffer cells. In addition, it appears that the amoebicidal activity of IFN-$\gamma$-treated Kupffer cells is contact-dependent.
In our study, Kupffer cells were also shown to be activated by TNF in vitro to an amoebicidal state and this cytolytic effect depends upon the ratio of Kupffer cells to amoebae, the concentrations of TNF used, and the time of exposure of the cells and the parasites to TNF.
Our results indicate that the immunologic production of IFN-$\gamma$ and TNF is important in the activation of Kupffer cells for controlling this parasite and that Kupffer cells are strong effector cells against the amoebae.
