Steady state behavior of endogenous NK cells in the LN. Ncr1^GFP/+ × CD11c-YFP mice were adoptively transferred with 6 × 10⁶ SNARF-labeled OT-I CD8 T cells. A day later, popliteal LNs were subjected to 2-photon imaging. Time-lapse videos were processed to fully discriminate GFP from YFP signals and were subjected to 3-dimensional cell tracking. (A) A representative image of a time-lapse video (left) with NK cells (red), CD8 T cells (blue), and DCs (green) is shown together with the corresponding trajectories (right). (B) The mean 3-dimensional velocity and the straightness index is plotted for individual NK cells and T cells in the same field of view. Low straightness indexes correspond to constrained trajectories. (C) Dynamic scanning of the DC network by LN NK cells at steady state. Representative time-lapse sequence showing NK cells crawling in the vicinity of the DC network. Scale bar, 10 μm. (D) Instantaneous velocities of 3 representative NK cells are graphed over time. The period during which NK cells are in contact with the DC network are indicated in red. Results are representative of 3 independent experiments.