Video 10. A region within the pSMAC of a representative primary B cell expressing GFP-F-Tractin (green), engaged with a PLB containing fluorescent anti-IgM (red) and unlabeled ICAM-1, and imaged every 5 s for 400 s using TIRF-SIM.

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The applied white lines mark actin arcs that are sweeping an antigen cluster centripetally, as explained in the text for Figure 4D1–D6. The inward tracks of this cluster and two other clusters are then shown in blue, green, and red, respectively. Played back at 10 fps. Scale bar: 1 μm.