Spontaneous adhesion of ATL cells to IL-1β–activated HUVECs. Adhesion of resting or PMA-activated peripheral normal CD4⁺ T cells, ATL cells freshly obtained from 6 representative ATL patients, CD4⁺ leukemic cells from a patient with HTLV-1–negative T-CLL, and 4 ATL cell lines (MT1, MT2, SALT-3, and HUT-102) that were labeled with ⁵¹Cr to IL-1β–activated HUVECs was assessed after 30 minutes of incubation at 37°C. γ-Emission of the lysate of only adherent cells was determined. Data are expressed as the mean percentage of binding of indicated cells from a representative experiment.