Interaction of lysosomes with endocytic vacuoles in macrophages simultaneously infected with Trypanosoma cruzi and Toxoplasma gondii.

Macrophages with lysosomes previously labelled with acridine orange or horseradish peroxidase were simultaneously incubated in the presence of epimastigotes of Trypanosoma cruzi and tachyzoites of Toxoplasma gondii. Light microscopic observations indicate that although a large number of macrophages were infected by the parasites very few contained both parasites. Fusion of the macrophage's lysosomes with vacuoles containing T. cruzi were seen both by fluorescence (acridine orange) and electron (horseradish peroxidase) microscopy. No fusion of lysosomes was seen with vacuoles containing T. gondii. These results were observed in macrophages infected by only one or by the two parasites simultaneously.