Role of neutrophils in innate resistance to Entamoeba histolytica liver infection in mice

In order to define the role of neutrophils in the innate resistance to Enta moeba histolytica liver infection in mice, we examined the pattern of liver lesion induced by direct injection of E. histolytica trophozoites in norma l mice and in neutrophil-depleted mice. A variety of histological lesions w ere found, the extent of liver damage was considerably higher in the neutro phil-depleted mice. Livers from neutrophil-depleted mice displayed areas of liquefactive (lytic) necrosis containing a large number of amoebae and abs ence of neutrophils or mononuclear cells. By contrast, in the liver of norm al mice, neutrophils were seen associated to E. histolytica at early stages of infection. In both mouse groups, areas of TUNEL-positive dead hepatocyt es were observed and a characteristic internucleosomal banding pattern of g enomic DNA consistent with apoptosis was detected in DNA harvested from amo ebic liver lesions. These data suggest that neutrophils play an important r ole in the mechanisms of resistance to amoebic liver infection in mice. In addition, our histological analysis suggests that E. histolytica is capable of producing liver damage in the absence of inflammatory cells.