ZAP-70⁺ CLL cells are more responsive to CCL19 and CCL21, but not CXCL12, when compared with ZAP-70^– CLL. CLL B cells were treated for 0, 15, 30, 45, and 60 seconds with 100 ng/mL CCL19 (A), CCL21 (B), or CXCL12 (C). Changes in intracellular F-actin were measured using FITC-labeled phalloidin in CD19, CD5-prelabeled CLL cells. Results are shown as the percent change in intracellular F-actin relative to the level observed in untreated cells. Results for each chemokine are the mean ± SEM of at least 13 independent experiments. Student paired t test; *P < .05.