CXCL13 induces actin polymerization in CLL B cells, but not in multiple myeloma cells. Intracellular F-actin was measured using FITC-labeled phalloidin after addition of 200 ng/mL CXCL13 at time 0 second, as indicated by the arrow. Results are displayed as percentage of intracellular F-actin relative to that prior to the addition of CXCL13, as indicated on the vertical axis. ■ represent data points that are the mean (± SD) relative F-actin content of CLL cell samples from 12 different patients at the time points displayed on the horizontal axis. □ and ◆ represent F-actin content in multiple myeloma cells from 2 different patients after stimulation with CXCL13. In contrast to CLL cells, myeloma cells did not display a transient increase in F-actin that is a characteristic cellular response to stimulation with a chemokine.