Fig. 1. Tracer and subcellular marker distribution in DC macropinosomes. Panel A shows the accumulation of FITC latex Bds into DCs, revealed by FACS histograms of cell preparations incubated with the tracer, from left to right, for 0, 5, 10, 20 and 60 minutes. The conversion in time-dependent curves of the FACS data, obtained in three experiments with either Bds or Dex, is shown in panel B. Panels C and D show merged confocal images of DCs exposed for 10 minutes to the styryl dye FM4-64 (red), alone (C) or together with FITC-conjugated Bds (green, D). The almost complete negativity of C shows that without the Bds endocytosis is weak, whereas with the Bds the labelled puncta are numerous, mostly positive for both the dye and the tracer (yellow). The merged images of panels E and F show the two tracers (green), Bds (E) and Dex (F), administered for 10 minutes, localized mostly in a fraction of the puncta positive for the early endosome marker EEA1 (red). Panel G illustrates the co-localization of Bds and Dex administered together for 10 minutes to DCs. Bar, 10 µm (C), also valid for D. Bar, 10 µm (E), also valid for F and G. Panels H and I show the ultrastructure of two cytoplasmic areas in DCs loaded with Bds for 10 minutes. Vacuoles of variable size and shape packed with the tracer (macropinosomes) are indicated by arrows. Bar, 0.5 µm (H).