Comparative studies on trypomastigotes of Trypanosoma cruzi from infected mouse blood and infected fibroblast cell (L-cell) culture.

The resistance to phagocytosis by macrophages and the penetration into fibroblast cells of blood form trypomastigotes of Trypanosoma cruzi were compared with those of trypomastigotes grown in fibroblast cell culture. On incubation for 24 h, blood form trypomastigotes were almost completely resistant to phagocytosis, but about 40% of the trypomastigotes from cell culture were phagocytized. On longer incubation, the resistance of both forms of trypomastigotes decreased gradually. The penetrating ability of blood form trypomastigotes was much lower than that of trypomastigotes from cell culture. Infection of mice with blood form trypomastigotes resulted in less proliferation of parasites in the liver and spleen than that with trypomastigotes from cell culture. From these results, the existence of two functionally different forms of trypomastigotes in infected mice and in infected fibroblast cell culture, respectively, is discussed.