Adhesion to ECM and reverse transmigration of DC. (A) Molecules involved in the adhesion of DC to EC-derived matrix (ECM). ECM were prepared by culturing a monolayer of EC on polycarbonate filters for at least 5 days; EC were then stripped by an NH₄OH + Triton solution for 30 seconds. Results are expressed as percent of adherent cells, mean ± SEM of three replicates. **Statistically significant at P < .01 versus medium control. (B) Reverse transmigration of DC. A double-filter system was used. The upper filter was coated with an ECM and the lower filter was coated with a monolayer of EC placed upside down. ⁵¹Cr-labeled DC were seeded in the upper compartment of the chamber and coincubated with EC monolayer for 3 hours at 37°C. Results are expressed as percent of adherent and transmigrated cells (see Materials and Methods), mean ± SEM of three replicates. Two independent experiments are shown.