DCs dilate BM perforations. (A) Spinning disk confocal images (maximum projection of z-stack, 10 planes, 0.5 µm distance) of DCs (red) in close vicinity of an initial lymphatic vessel (BM staining: collagen IV, green; blood capillary also visible). Bar, 20 µm. (B) Inset of A showing the initial events of a single DC (red) entering the vessel lumen via a preexisting perforation (arrow; maximum projection of z-stack, 5 planes, 0.5 µm distance). Top row shows the top view onto vessel BM (collagen IV), the bottom row the corresponding sectional XZ-view (BM green; DC red). Bar, 5 µm. (C) Representative spinning disk confocal images of an initial lymphatic vessel showing the enlargement of perforations (BM staining: collagen IV) over a period of 1.5 h. Bar, 10 µm. Enlargements of insets 1–3 are shown on the right. Overlay images show perforation size at t = 0 h (green) and t = 1.5 h (red). Bar, 2 µm. A histogram plot of the line section across the perforation shows fluorescence intensity of collagen IV at t = 0 h in green and at t = 1.5 h in red. Images are representatives of one of at least nine independently performed crawl-in assays.