CD31 stimulation of eosinophils increases eosinophil adhesion to IL-4–stimulated endothelial cells through VLA-4/VCAM-1 interaction. ⁵¹Cr-labeled eosinophils were preincubated with anti-CD31 MoAb or control mouse IgG (10 μg/mL each) for 10 minutes at 37°C. After washing the cells, the adhesion assay of⁵¹Cr-labeled eosinophils to IL-4–stimulated (▪) or unstimulated (□) HUVECs was performed in the presence or absence of anti–VCAM-1 MoAb or anti–VLA-4 MoAb (10 μg/mL each). 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). ***Significantly different from the mean value of the corresponding control response (***P < .001).