RESUMO
A series of descriptions in the literature points to the fact that an interaction between host-derived cytokines and protozoan parasites can play a role in the natural history of a disease. In this paper those examples are reviewed and discussed. In most cases, the host-derived molecules act as growth factors for the parasites, and in one case, protect the infective form from heatinduced death. Since the molecules described act as growth factores or as protectors from death when acting on cells from the host, it is suggested that their mechanism of action is the same, when targeting mammalian cells or protozoan parasites. A hypothesis is formulated that protozoan parasites might adapt to their mammalian host by "mimicking" a host cytokine-dependent system of cell growth and differentiation.