Effect of VEGF and α₄ blockade on integrin clustering on CLL and normal B cells. (A) Quantitative data from the experiments illustrated in Figure 5 involving CLL cells incubated on HUVECs. (B) Results for similar experiments performed with normal B cells motile on HUVECs. (C) Results of experiments where CLL cells were cultured on VCAM-1 (+ CCL21). In all 3 panels, for the experiments involving VEGF inhibition, more than 98% of cells showed copolarization of both α₄ and α_L and the results therefore show the percentage of copolarized cells. However, when the effect of α₄ inhibition was examined the cells were stained with α_L only, and the percentages given represent the number of cells in which this integrin was clustered. All data were obtained after 5 minutes of incubation.