FIG. 1.

T. cruzi-infected human DC. (A and B) DC were incubated with T. cruzi trypomastigotes at different parasite-to-cell ratios (0.1:1 to 20:1). After 24 h, the cultures were washed to remove free parasites and DC were fixed with methanol and stained with Giemsa stain. The percentages of infected DC (A) and mean numbers of amastigotes per infected DC (B) were recorded after microscopy examination of at least 300 cells. Data are from four independent experiments with four different blood donors. (C) In another set of experiments, DC were first incubated with T. cruzi trypomastigotes at a parasite-to-cell ratio of 5:1 for 24 h and then excess parasites were removed by extensive washing. Cultures of DC were continued for an additional incubation time of 24 or 48 h before the cells were fixed and stained with Giemsa stain. Mean numbers of amastigotes per infected DC were recorded after microscopy examination of at least 300 cells. Data are from three independent experiments with three different blood donors.