Histograms show the quantifications of the polymerized tubulin and filamentous F-actin at the centrosome (dashed outline on the image, values correspond to the fraction of fluorescence in a 2-micron-wide area around the centrosome relative to the total fluorescence in the cell) and the total amount of polymerized fluorescent tubulin (bottom right, values were normalized with respect to the mean of control condition). Measurements were pooled from 3 independent experiments; IgM (BCR-ligand-): n= 88; IgG (BCR-ligand+): n= 93. Error bars correspond to standard deviations. P values were calculated with Mann-Whitney test. Scale bar: 2 µm. 