(A) Monocyte adhesion to HUVECs under flow conditions. Endothelial cells were stimulated with 0.1 ng/mL IL-1β and monocytes (10⁶/mL) were perfused over the monolayer for 10 minutes at 2 dynes/cm². Total interaction gives a measure of primary adhesion and includes all monocytes interacting with the monolayer for at least 2 seconds. On endothelial cells, MoAb CL2/6 was used to block E-selectin function, whereas MoAb R15.7 binds to the β₂ subunit of CD18 integrins present on monocyte surface, and blocks its function (n = 3 to 19). (B) Adhesion of monocytes to (4 h) IL-1β–stimulated HUVECs at 2 dynes/cm². Dreg-56 was used to block L-selectin function on monocytes. Data is shown as mean ± SEM for 3 to 19 experiments. MoAb Dreg-56 was used to block L-selectin function on monocytes. MoAb HP2/1 binds to VLA-4 on monocytes and is function blocking. To block E- and P-selectin, endothelial cells were treated with MoAbs CL2/6 Fab₂ and GA6, respectively. Sialidase treatment included use of neuraminidase enzyme (0.1 U/mL, 30 minutes incubation at 25°C) to cleave sialyl lewis residues from the monocyte surface. *Statistical significance (P < .05) compared with control with no MoAb treatments.† Statistical significance (P < .05) compared with neuraminidase, anti–L-selectin, and anti–VLA-4 treatment.