Tissue invasion and disease associated with the protozoanEntamoeba histolytica has long been connected with suppression of host cellular immunity. Dampening of the host's defences may facilitate survival of amoebae in extra-intestinal sites and development of the characteristic amoebic abscesses. In recent years, several studies have begun to clarify, at the cellular level, the specific effects E. histolyticahas on immune cell accessory and effector cell functions. Here, Darren Campbell and Kris Chadee discuss the parasite's multiple modulatory effects on macrophages and T cells and how this manipulation of immune defences may enable the parasite to remain viable in the host. They suggest the putative amoebic molecules involved and potential modulation by the cytokines: interleukins IL-4 and IL-10 and transforming growth factor-β.