P-selectin, VCAM-1, and 4-integrins together mediate eosinophil tethering on IL-4–stimulated HUVECs. Monolayers of HUVECs were treated as described in Fig 1. Before assembly of the flow chamber, HUVECs were treated for 10 minutes at 37°C with HBSS/A alone; HBSS/A containing 5 μg/mL of 1.G11B1, an MoAb directed against VCAM-1; 5 μg/mL of either a nonblocking (S12) or blocking (G1) MoAb directed against P-selectin; or 5 μg/mL of both anti–VCAM-1 and G1 MoAbs. In some experiments, eosinophils were also pretreated for 10 minutes at 37°C with 2 μg/mL of H2/1, an anti–4-integrin MoAb, before perfusion over IL-4–stimulated HUVECs. The flow chamber was assembled and eosinophils also containing the specified MoAbs were perfused through the chamber. Tethering of eosinophils was determined at 2 dyn/cm², as described in Materials and Methods. The data represent the mean and SEM of at least three independent experiments. *P ≤ .05; **P ≤ .01.