T cells and NK cells use different modes of interactions with stimulatory DCs. Ncr1^GFP/+ mice were adoptively transferred with SNARF-labeled naive OT-I CD8 T cells. Unpulsed or peptide-pulsed DCs purified from CD11c-YFP mice were injected in the footpad of recipients in the presence or absence of poly I:C. Popliteal LNs were subjected to 2-photon imaging 20 hours after DC transfer. (A left) Representative image showing DCs (green), NK cells (red), and T cells (blue). NK cells and T cells trajectories in the presence of DCs pulsed with OVA peptide and poly I:C (middle). The figure shows that T cells but not NK cells are arrested, as reflected by their highly constrained trajectories. (Right) Image sequence showing the same peptide-pulsed DC forming a stable contact with 2 OT-I T cells and a transient interaction with an NK cell. Scale bar, 10 μm. (B) Individual OT-I T cells and NK cells were assessed for their interactions with peptide-pulsed DCs in the presence of poly I:C. The periods during which T cells and NK cells are in contact with a DC are colored in blue and red, respectively. Each square corresponds to a time interval of 30 seconds. (C) Graph shows the overall percentage of time spent by individual T cells (left) or NK cells (right) in contact with the indicated DC populations. Mean values are shown as black bars. The duration of individual contacts is also plotted for T cell–DC (left) and NK cell–DC interactions (right).