Effect of silica on resistance of mice to Entamoeba histolytica infection.

The role of macrophages in intestinal amoebiasis in mice has been investigated. The effect of injuring host macrophages on the course of infection was examined by using strains selected as being either genetically susceptible (C3H/HeJ, C57BL/6) or genetically resistant (A/J) to amoebiasis. Mice were treated with an intravenous injection of silica particles 1 day before infection with 2.5 X 10(5) or 5 X 10(5) polyxenic trophozoites of Entamoeba histolytica. The animals were killed at various times after infection, and the parasite burden in the cecum was measured. Silica treatment dramatically increased the growth of parasites in the susceptible mice. The same trend was evident, although less marked, in the resistant mice. The effect of silica treatment in experimental amoebiasis was much more pronounced in animals inoculated with 5 X 10(5) amoebae than in those with 2.5 X 10(5) amoebae. These data suggest that macrophages play an important role in host defense against amoebiasis in mice.