[Role of macrophages and T-lymphocytes: resistance of guinea pigs to amebic liver infection].

The mechanisms of host resistance in hepatic amebiasis are poorly understood. Previous studies in guinea-pigs have shown that amebic liver infection is mild and cures spontaneously in approximately four days, in contrast to hamsters, where amebic liver infection progresses to coalescent abscesses that kill the animals in about one month. To determine the role of macrophages in the resistance of guinea-pigs to hepatic amebic infection, animals were treated with intraportal injection of Entamoeba histolytica, using the same route. Results showed that the amebic hepatic lesions are larger and require longer time to cure in the silica-treated group. This suggests that macrophages play a role in the resistance of the guinea-pig to amebic liver infection. The possible dependence of T lymphocytes in the resistance of guinea pigs to amebic hepatic infection was analyzed using Cyclosporin A. Results showed that resistance to E. histolytica liver infection is not related to circulating T lymphocytes. We conclude that the guinea-pig is a suitable experimental model for the study of natural host resistance mechanisms in hepatic amebiasis. Macrophages, but not T lymphocytes participate as an effective cellular immune response to eradicate amebic infection in the liver of guinea-pigs.