One fate of epimastigote forms of Trypanosoma cruzi injected in mice. An ultrastructural study

Recently, we suggested that epimastigote forms of Trypanosoma cruzi are cle ared from circulation of mice by a mechanism independent of lysis and that platelets play an important role in this process. These observations prompt ed us to look at the fate of epimastigotes in the lung, Liver, and spleen o f mice injected intravenously with these parasite forms. Using transmission electron microscopy, we observed clumps of epimastigotes and platelets in direct contact with phagocytes in the lumen of capillaries. However, the pl atelets and parasites were probably separated before phagocytosis because o nly parasites were found inside the phagocytes. Indeed, most of the phagocy tes, although containing epimastigotes in different stages of disintegratio n, contained no platelets. The removal of parasites from platelets was prob ably mediated by phagocytes through a mechanism similar to the removal of b acteria from the surface of erythrocytes in humans. These observations sugg est that the nonvirulence of T. cruzi epimastigotes in mice is not due to l ysis but probably to the inability of these parasite forms to escape destru ction by the phagocytes.