CLIP-170 moves towards the periphery of B cells spreading on immobilized anti-Ig. A20 cells that had been transfected with CLIP-170-GFP to mark the plus ends of microtubules were allowed to spread on anti-IgG-coated coverslips for 10 min and then imaged by TIRF microscopy with a 100-nm TIRF depth. Images were acquired every 30 ms. The video is played back at 75 frames per second (2.25X real time). The CLIP-170-GFP fluorescence signal is shown as a heat map in which low fluorescence intensity is purple and high fluorescence intensity is white.