SNAP-23, syntaxin 3, and TI-VAMP involvement in the apical pathway. (A) Effect on the apical transport of HA of antibodies against SNAP-23 and syntaxin 11, 4, and 3 at the respective concentrations of 1.6, 1.5, 1.5, and 1.3 μM. (B) Distribution of TI-VAMP in polarized MDCK cells. Confocal (x,z) section of fixed cells stained for TI-VAMP (green) and DNA (propidium iodide; red). Cells were observed on a Zeiss LSM 510 confocal microscope. (Bar = 15 μm.) (C) Dose-dependent reduction of TGN to apical surface transport by the anti-TI-VAMP antibody.