Increase of L-α4β1 cell adhesion to Lu-Fc by TS2/16 anti-β1–activating antibody and by epinephrine under flow conditions. (A) A cell suspension including L-α4β1 and calcein-labeled L-α4β1 or L-WT cells (107 cells/mL; 1:1) was incubated with 1 μg/mL activating antibody anti–integrin β1 (TS2/16) and 1 mM MnCl2 for 20 minutes at room temperature, then injected into a Lu-Fc–coated microslide (0.3 mg/mL) for 10 minutes 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. Untreated cells were injected separately as control. (B) A cell suspension, including L-α4β1 and calcein-labeled L-αLβ2 cells (107 cells/mL; 1:1) was either untreated, or incubated with 20 nM epinephrine (Epi) for 1 minute at room temperature with or without preincubation with 10 μg/mL blocking antibody anti–integrin β1 (mAb 13). Injection and washes were carried out as for panel A. (**P < .01). Error bars represent SD.