Fig. 7. Confocal microscopy of mixed CEACAM1-transfected and untransfected MDCK cells. Untransfected MDCK cells were mixed 50:50 with either CEACAM1-L-transfected or CEACAM1-S-transfected MDCK cells and grown to confluence on permeable filters. The cells were treated with or without hyperosmotic sucrose, fixed with 3% paraformaldehyde and permeabilized by methanol for 2 minutes at room temperature. Some cultures were stained with anti-CEACAM1 mAb 5.4/Alexa488-conjugated secondary antibodies (green colour), and some cultures were double-stained with anti-CEACAM1 CC16/Alexa 546-conjugated secondary antibodies (red colour) and antioccludin/Alexa488-conjugated secondary antibodies (green colour). The horizontal lines in the xy-composites indicate the plane for the z-reconstructions. Note that lateral expression of CEACAM1-L is only found in the borders between CEACAM1-L expressing cells but not in the borders between CEACAM1-L expressing cells and untransfected cells. CEACAM1-S was not stained by mAb 5.4. Bars: 20 µm.