Fig. 10. Fusion of HRP-loaded late endosomes/lysosomes with parasite-containing compartments as observed by electron microscopy. IFN--treated macrophages were incubated with HRP for 30 minutes. After extensive washings, they were chased for 160 minutes before infection with L. amazonensis metacyclic promastigotes. Thirty minutes after infection, macrophages were fixed and processed for peroxidase cytochemistry. (A) HRP is located in numerous late endosomes/lysosomes (arrows) as well as in the lumen of the tight promastigote-harbouring compartment (arrowheads). (B,C) Details of A showing the fusion of HRP-containing late endosomes/lysosomes with the phagolysosomal compartment (arrows). The presence of HRP in the flagellar pocket of the parasite is also observed (arrowheads). Bars, 1 µm (A), 0.2 µm (B,C).