Figure 3.

Indirect immunofluorescence with anti-occludin 1B (A, D, and F), preimmune occludin 1B (C), anti-occludin (B and E), and anti-myc (G). Specimens shown are MDCK cells (A–C and G), T84 cells (F), and mouse duodenum (D and E). (A and B) Double labeling of occludin 1B (A) and occludin (B) in MDCK cells. Note colocalization of the immune staining of both occludins at the cell-to-cell contacts. The nuclear labeling observed in A is nonspecific, because it is also detected by the preimmune serum (C). (D and E) Tangential section through the apical area of mouse intestinal epithelial cells double labeled with antiserum to occludin 1B (D) and with affinity-purified polyclonal anti-occludin (E). The staining for occludin 1B and occludin colocalized at the junctional complexes between intestinal epithelial cells. (F) T84 cells labeled with anti-occludin 1B. The staining is at the cell-to-cell contacts, most likely at the tight junction. (G) MDCK cells expressing myc-tagged full-length occludin 1B are labeled with anti-myc antibody. Transfected occludin 1B is targeted to the cell-to-cell contacts. Bars, 10 μm for A–C, F, and G; 5 μm for D and E.