TF localization on polarized Caco-2 cells. Cells were processed for indirect immunofluorescence with polyclonal rabbit anti-human TF IgG antibody followed by FITC-conjugated goat anti-rabbit antibody. Images were acquired by confocal microscopy as described in Materials and Methods. Cells were sectioned in the X-Y plane from the apical to basal membrane surfaces at 0.5-μm increments. Panels (A) through (G) represent nonpermeabilized cells. Panels (A) and (B) represent single focal X-Y planes at 2-μm increments around the apical membrane domain. Panels (C) and (D) represent single focal X-Y planes at 2-μm increments through the center of the cells. Panel (E) represents the basal membrane. Panels (F) and (G) show representative X-Z confocal views of nonpermeabilized cells. In panels (H) through (J), cells were permeabilized with 0.2% saponin. Panel (H) represents TF-specific staining of the apical membrane domain. Panel (I) represents mainly basolateral TF staining, 6 μm from plane in panel (H). Panel (J) represents TF staining of the basal membrane, 14 μm from plane in panel (H). Bars, 10 μm.