DF internalization by SK cells. Merged confocal images of all individual channels (red staining with wheat germ agglutinin for membranes, blue with Hoechst for nuclei, and green with Alexa 488 for DF), and Z projection (narrow images in the right and in the bottom of the main picture) show that DF remains in the cytoplasm displaying vesicular staining and does not enter into the nuclei, at least after 24 hours of incubation. Confocal images were taken using a Leica TCS SP5 microscope and a 63× oil immersion objective. Optical sections (z) were performed each 2 μm. Image analysis was performed using Fiji software (National Institutes of Health).