Effect of anti-CD31 and anti-vβ3 integrin antibodies on eosinophil adhesion to IL-4–stimulated vascular endothelial cells. HUVEC monolayers grown on the well of 24-well tissue culture plates were stimulated with or without IL-4 (100 ng/mL) for 8 hours at 37°C. IL-4–stimulated (▪) or unstimulated (□) HUVECs were preincubated with anti-CD31 MoAb NIH31-1 (10 μg/mL), anti-vβ3 integrin MoAb LM609 (10 μg/mL), or control mouse IgG (10 μg/mL) for 10 minutes at 37°C, washed, and then incubated with⁵¹Cr-labeled eosinophils (3 × 10⁵) for 10 minutes at 37°C. After HUVECs were gently washed, adherent eosinophils were lysed by the addition of HBSS containing 1% Triton X-100 and the radioactivity of the cells was counted in a gamma counter. Data are the means ± SD for 6 experiments. *Significantly different from the mean value of the control response to unstimulated HUVECs (*P < .001). **Significantly different from the mean value of the control response to IL-4–stimulated HUVECs (**P< .001).