Interaction of Trypanosoma cruzi with macrophages in vitro: dissociation of the attachment and internalization phases by low temperature and cytochalasin B.

Chicken macrophages, obtained by cultivation of blood monocytes, were infected with epimastigote and bloodstream trypomastigote forms of Trypanosoma cruzi strain Y. The percentage of macrophages containing parasites within parasitophorous vacuoles and of flagellates attached to cell surfaces was determined. By incubation of the macrophages at 4 degrees C or in the presence of cytochalasin B it was possible to dissociate the attachment from the internalization phases in the process of infection of macrophages. Both treatments had a marked effect on the internalization of epimastigote and trypomastigote forms. Cytochalasin B treatment and placement of the macrophages at 4 degrees C before infection inhibited this process by about 99 and 96%, respectively. These results suggest that endocytosis is the principal mechanism of internalization of T. cruzi by macrophages. They show also that epimastigote and trypomastigote forms of T. cruzi have a different rate of adhesion to the macrophage surface.