The effect of splenectomy on resistance of mice to Entamoeba histolytica infection.

The role of the spleen in amoebic infection was examined in mice, using strains selected as being either genetically-susceptible (C57BL/6) or genetically-resistant (A/J) to amoebiasis. Splenectomized and sham-operated animals were inoculated intracaecally with 2.5 X 10(5) polyxenic trophozoites of E. histolytica at 6, 12 and 15 days post-splenectomy. The animals were killed 6 or 12 days after infection and the parasite burden was evaluated. Removal of the spleen in both susceptible and resistant mouse strains rendered these hosts extremely resistant to amoebic infection by this criterion. Gross examination of the caeca of non-splenectomized, genetically-susceptible mice showed numerous ulcers over the mucosal surface when compared to the splenectomized group which had superficial lesions or none. These observations suggest that the spleen plays a suppressive role in early anti-amoebic resistance.