Fluorescence microscopy analysis of transferrin-AlexaFluor 633 endocytosis by isolated intracellular amastigotes of <i>Trypanosoma cruzi</i>.

<p>Cells were allowed to ingest transferrin-AlexaFluor 633 and were then incubated with anti-transferrin antibody (in red) and anti-cruzipain mAb (CZP-315.D9; in green). (A-B) Isolated intracellular amastigotes incubated without transferrin at 4°C or 37°C, showed no transferrin labeling (negative control), while cruzipain was located at the posterior region of the cell. (C) Isolated intracellular amastigotes incubated with transferrin at 4°C. No co-localization with cruzipain was observed. (D) Isolated intracellular amastigotes incubated with transferrin at 37°C. Co-localization with cruzipain was observed at the posterior region of the cell. (E-F) Isolated intracellular amastigotes incubated with transferrin at 4°C and 37°C and then subjected to acetic acid treatment. No co-localization of transferrin with cruzipain was observed at 4°C (E), while co-localization with cruzipain occurred at the posterior region at 37°C (F). The nucleus (n) and the kinetoplast (k) were stained with Hoechst 33342 (in blue). DIC, differential interference contrast. Scale bars, 2.5 μm.