Interaction of bloodstream, tissue culture-derived and axenic culture-derived trypomastigotes of Trypanosoma cruzi with macrophages.

Mouse macrophages were infected with bloodstream, tissue culture-derived and axenic culture-derived trypomastigotes of the Y and the CL strains of Trypanosoma cruzi. The percentage of infected cells, the mean number of parasites per cell and the incorporation index were determined after 2 h of interaction. Longer periods of interaction were used to evaluate the fate of the different trypomastigotes inside the macrophage. It was observed that the incorporation of T. cruzi by the macrophages was high for tissue culture-derived trypomastigotes, intermediate for axenic culture-derived trypomastigotes and low for bloodstream trypomastigotes. For the three types of trypomastigotes, a larger number of macrophages were infected with parasites from the Y than the CL strain. These results suggest that the ability to infect macrophages is a basic characteristic of each strain which is maintained when the parasites are transferred from the vertebrate of the invertebrate host to in vitro systems.