The microtubule network is involved in rituximab-mediated CD20 polarization. (A) Fluorescent and bright-field images of Daudi/CD20-GFP cells incubated with rituximab and labeled for α-tubulin (red). The MTOC is identified as the brightest spot in the red channel. Scale bar represents 10 μm. (B, left) Schematic representation of a cell in which MTOC polarization toward the CD20-enriched region was assessed by calculating the polarity index values corresponding to the ratio between the distance from the MTOC to the CD20 cap (a) and the cell diameter (b). Distribution of polarity indexes in primary B cells (B, top right) and Daudi cells (B, bottom right) incubated with rituximab is shown. A total of 74 Daudi and 84 primary B cells were analyzed. Proportion of Daudi (C) and primary B cells (D) with polarized CD20 in untreated cells or after incubation with rituximab and nocodazole. Graphs represent mean ± SEM of 3 independent experiments. More than 100 cells were analyzed per condition. Data were analyzed by 1-way ANOVA with Bonferroni post-test. *P < .05; **P < .01; ***P < .001.