Blocking MoAb to E-selectin inhibits SDF-1–induced transmigration of CD34⁺ cells through IL-1β–activated endothelial cells. Freshly isolated CD34⁺ cells (10⁵ cells) from CB were placed in the upper chamber of 5-μm transwell plates coated with confluent monolayers of IL-1β–stimulated intact BMEC monolayers in the presence or absence of 10 μg/mL blocking MoAb to E-selectin. Immediately, 200 ng/mL of SDF-1 was placed in the lower chamber and the number of migrated cells was evaluated by flow cytometry. After a period of 24 hours, in the absence of SDF-1, there was migration of only 7.0% ± 1.4% of the added CD34⁺ cells to the upper chamber. In the presence of 200 ng/mL SDF-1, there was migration of an additional 23.0% ± 4.4% of the added CD34⁺ cells. In the presence of blocking MoAb to E-selectin (10 μg/mL), there was a 42.0% ± 2.5% inhibition of the SDF-1–induced migration of CD34⁺ cells (N = 4, P < .003). Blocking MoAb to VCAM-1 and ICAM-1 did not significantly influence the SDF-1–induced migration process.