Mechanisms of natural resistance of Balb/c mice to experimental liver amoebiasis.

Entamoeba histolytica is the parasite responsible for human amoebiasis. The analysis of the natural resistance mechanisms of some rodents to amoebic liver abscess (ALA) may reveal alternative pathogenicity mechanisms to those previously discovered in the experimental model of ALA in hamsters. In this work the natural resistance of BALB/c mice to ALA was explored by performing: (i) in vivo chemotaxis analysis with a specifically designed chamber; (ii) in vitro amoebic survival in fresh and decomplemented serum; (iii) histological temporal course analysis of ALA development in mice with different treatments (hypocomplementemic, hyperimmune and treated with iNOS and NADPH oxidase inhibitors) and (iv) mouse liver amoebic infection by both in situ implantation of ALA from hamsters and inoculation of parasites into the peritoneal cavity. The results show that E. histolytica clearance from the mouse liver is related to a low chemotactic activity of complement, which results in poor inflammatory response and parasite inability to cause tissue damage. Also, the absence of amoebic tropism for the mouse liver is correlated with resistance to experimental liver amoebiasis.