Fig. 3. Localization of Syt III in RBL cells. RBL cells were processed for immunofluorescent staining and visualized by confocal microscopy, as described under Materials and Methods. Cells were incubated with antibodies directed against Syt III (A,D,G, 1:100 dilution), T7 (B, 1:200 dilution), serotonin (E, 1:25 dilution) followed by rhodamine-conjugated donkey anti-rabbit or FITC-conjugated donkey anti-mouse IgG. To monitor internalized Tfn (H), cells were serum starved for 1 hour before incubation for 10 minutes with FITC-conjugated human Tfn (50 µg/ml). Bars represent 10 µm. Data represent one of three separate expreiments.