ABSTRACT
An immune response to Entamoeba histolytica appears to occur only as a result of tissue invasion by the parasite. Once trophozoites have invaded the intestinal mucosa, a conventional immune response ensues. Skin tests to determine delayed-type hypersensitivity against Entamoeba histolytica antigens have been performed with antigens such as sonicates of axenically grown amebas or amebas grown with other microorganisms. Blast transformation of lymphocytes obtained from patients with amebic liver abscess, specifically stimulated by aqueous extracts of Entamoeba histolytica and measured by the incorporation of tritiated thymidine, is greater than that observed in lymphocytes of healthy individuals. The role of macrophages in host defense against experimental infection with Entamoeba histolytica has also been explored in hamsters and mice by either enhancing or blocking their function.
