Adhesion of U937 cells to HUVECs under flow conditions. (A) Non-, sense-, and antisense-transfected U937 cells were added to wells coated with HUVECs, which were stimulated with TNF-α (100 U/mL) for 4 hours and fixed afterward. Bound U937 cells were analyzed as described in the legend to Figure 1B. (B) Non-, sense-, and antisense-transfected U937 cells (2 × 10⁶ cells/mL) were perfused for 10 minutes with a wall shear stress of 0.8 dyne/cm² over a glass coverslip confluently covered with HUVECs, which were stimulated with TNF-α (100 U/mL) for 4 hours before perfusion. Where indicated, cells were preincubated with anti-β2-integrin or anti-α₄ antibodies (20 μg/mL) or GST-RAP (50 μg/mL) for 15 minutes. The number of firmly adhered cells per square millimeter was obtained from video-image analysis. Data represent the mean ± SD of 3 to 8 perfusions.