Binding of FITC-CTB on rat reticulocyte exosomes. Exosomes from rat (•) or human (○) reticulocytes were conjugated to magnetic beads. Increasing amounts of the FITC-CTB were incubated with 100 μL of exosome-bead conjugates and analyzed by flow cytometry as described in Materials and Methods. The fluorescence peak position is plotted as a function of added FITC-CTB.