Transmigration of ATL cells through IL-1–activated HUVECs. Transmigration of ATL cells was assessed in 3-μm pore, 12-well microchemotaxis chambers precoated by IL-1β–activated HUVECs for 48 hours at 37°C. An ATL cell line MT1 (a) and ATL cells from patients (b), both labeled with ⁵¹Cr, were placed in the insert wells. After incubation for 2 hours at 37°C, cells that have migrated into each of the lower wells were retrieved and dissolved and γ-emissions of the well contents were determined. Data are expressed as the mean percentage of transmigrated cells from a representative experiment.