SS RBCs activated by anti–β1 TS2/16 antibody adhere to HUVECs in a Lu/BCAM-dependent manner under flow conditions. (A) SS RBCs (.005 [0.5%] hematocrit) were either untreated or incubated with 1 μg/mL activating antibody anti–integrin β₁ TS2/16 with or without 10 μg/mL of soluble Lu-Fc for 20 minutes at room temperature. Red cells were then injected for 10 minutes over a HUVEC monolayer at 0.2 dyne/cm². Washouts (5 minutes) were applied sequentially from 0.4 to 4 dyne/cm², and cells were counted in 6 different areas along the microslide centerline after each wash. AA RBCs were used as control. (B) SS RBCs from 5 patients (SS3-SS7; .005 [0.5%] hematocrit) were either untreated or activated by 1 μg/mL activating antibody anti–integrin β₁ TS2/16. Activated RBCs were incubated with 10 μg/mL of Lu-Fc or VCAM-1–Fc, and RBC adhesion was analyzed as in panel A. The figure shows the number of adherent RBCs at 1 dyne/cm². Each value is a mean of 6 measures. (*P < .05; **P < .01; in panel B ▪ is compared with □, and ▧; and ⊡ are compared with ▪). Error bars represent SD.