Coculture of ECs with SMCs increased the adhesion of neutrophils, PBLs, and monocytes and their subsequent transmigration under VSF, especially in the vicinity of flow reattachment. ECs were seeded on the collagen gel in the absence (EC/Gel) or presence (EC/SMCs) of SMCs. Purified neutrophils (A,D,G), PBLs (B,E,H), or monocytes (C,F,I) were perfused over the EC monolayers for 20 minutes under the VSF, and their adhesion (A-C) to and transmigration (D-F) across the EC monolayer were counted in each of the areas a, b, c, and d, as described in “Materials and methods.” The transmigration-adherence ratio (G-I) was calculated from the numbers of transmigrated cells relative to adherent cells. As positive controls, EC/Gel and EC/SMC treated with IL-1β (5 ng/mL) for 4 hours caused increases in WBC adhesion and transmigration (data not shown). Data are expressed as mean ± SEM from 3 independent experiments. ^*P < .05 versus control EC/Gel in the same area. ^#P < .05 for comparing area c with areas a, b, and d (P < .05 for each comparison).