[Modes of entry of Toxoplasma gondii trophozoites into normal mouse peritoneal macrophage and HeLa cell monolayers. A phase-contrast microcinematographic study (author's transl)].

The mode of entry of living trophozoites of Toxoplasma gondii (RH strain) into normal mouse peritoneal macrophage and HeLa cell monolayers was studied by phase-contrast microcinematography. The results have shown that Toxoplasma can enter into macrophages either by phagocytosis (Figs. 1 and 2) and/or by active penetration (Fig. 3). Only the latter process was observed with normally non-phagocytic HeLa cells (Fig. 4). During this process the parasites actively moved towards the host-cells by flexion and penetrated them always through their sharpest end. Active penetration was a rapid phenomenon (about 20 s at 37 degrees C) and was accompanied by a series of morphological changes, i.e., elongation of the anterior end, contraction and swelling of the parasite body. Contrasting with phagocytosis, toxoplasmas which had penetrated into the cell were not immediately isolated from the host-cytoplasm by a microscopically discernable vacuole. The nature of the process of penetration (pressure and/or perforation of the plasma membrane) is discussed.