Tracings of the subendothelial migration paths of the transmigrated neutrophils, PBLs, and monocytes in each of the areas under VSF and under static condition. Purified neutrophils, PBLs, and monocytes were perfused over the EC/SMC coculture, and the migration of arrested WBCs was traced for 20 minutes in areas a, b, c, and d under VSF or under static condition after their transmigration across the EC monolayer to the underside. This figure shows the results of a representative experiment containing 8 cells transmigrated in area a and 15 cells transmigrated in areas b, c, and d, as well as under static condition. The positions of the centers of the cells were determined at 20-second intervals from 0 to 20 minutes, and their paths of travel were processed with image analysis software NIH Image 1.60b7. Examples for online microscopic observations of the movements of transmigrated neutrophils, PBLs, and monocytes in areas c and d are provided in Videos S3, S4, and S5, respectively.