Defective chemokinesis in Rac-deficient T cells. (A) CD4⁺ T cells from mice of the indicated genotypes were cultured in the presence of CXCL12, CCL19, or CCL21 or with no chemokine, and their EYFP fluorescence was recorded by video microscopy. Images on the left show a snapshot from the videos. Flower plots on the right show migration tracks of individual cells, with the starting point of each track placed at the origin (0, 0). (B) Scatter plots of mean velocities of individual cells of the indicated genotypes taken from the videos described in panel A. Red bars indicate the average of these velocities. (C) Mean ± SEM shape index of cells of the indicated genotypes responding to the indicted stimulus derived from the videos described in panel A. A circle has a shape index of 1.0; any distortion from a perfect circle results in a shape index of > 1.0. Data are from 1 representative experiment of 2 independent experiments. *P < .05; **P < .01; ***P < .001.