Slow, meandering migration of cortical thymocytes expressing diverse T cell receptors (TCRs), visualized by real-time imaging of green fluorescent protein-positive (GFP⁺) thymocytes in the cortices of intact thymic lobes. Green represents the fluorescent signal from GFP⁺ thymocytes; colored lines represent the positions of individual cells over time. This data set has the dimensions 164 μm x 164 μm x 40 μm x 25 min (x x y x z x time). A typical slow meandering thymocyte (black track near center) and a rare rapid directional thymocyte (black track near bottom) are emphasized. Video supplied by Ellen Robey.

Rapid, directional migration of thymocytes expressing a positively selected TCR, visualized by real-time imaging of thymocytes expressing GFP and a positively selected TCR (P14) in the cortices of intact thymic lobes. Green represents the fluorescent signal from GFP⁺ thymocytes; colored lines represent the positions of individual cells over time. This data set has the dimensions 164 μm x 164 μm x 40 μm x 25 min (x x y x z x time). There is a large proportion of rapid, directional thymocytes. Video supplied by Ellen Robey.

CD4⁺ T cell-dendritic cell interactions in the diffuse cortex of a lymph node. Stable contacts form between several T cells (red) and individual dendritic cells (green) during the cluster stage of interaction (approximately 10 h into a priming immune response). Video supplied by Mike Cahalan.

Helper T cell-B cell conjugate pairs are seen 'waltzing'. Stable T cell-B cell conjugates with rapid motility form near the edge of a lymph node follicle approximately 30 h after priming with antigen. B cells (red) 'lead' their T cell (green) partners. Video supplied by Mike Cahalan.

Islet antigen-reactive T helper cells interact with dendritic cells in pancreatic lymph nodes. T cells (red) from nonobese diabetic BDC2.5 TCR-transgenic mice were transferred into nonobese mice expressing a GFP transgene under control of the mouse insulin promoter (NOD.MIP.GFP). Dendritic cells (green) in the draining lymph node acquire GFP from islet β-cells. Images show the interaction of swarming T cells with resident dendritic cells in the pancreatic lymph node 18 h after T cell transfer. This video is generated by the projection of ten images spanning 20 μm in the z direction onto a single plane. The duration of this imaging is 15 min in real time, which is compressed to 5 s in this video. Video supplied by Qizhi Tang and Max Krummel.

Regulatory T cells (T_reg cells) interact with dendritic cells in pancreatic lymph nodes. Nonobese diabetic BDC2.5 TCR-transgenic T_reg cells (red) were transferred into NOD.MIP.GFP-transgenic recipient mice. T_reg cells interact directly with self antigen-presenting dendritic cells (green) in the draining lymph node. Images show interactions in the pancreatic lymph node 18 h after T cell transfer. This video is generated by the projection of ten images spanning 20 μm in the z direction onto a single plane. The duration of the imaging is 10 min in real time, which is compressed to 3 s in this video. Video supplied by Qizhi Tang and Max Krummel.

Intravascular immune surveillance by natural killer T cells in mouse liver. Natural killer T cells (green) 'crawl' along hepatic sinusoids in constant contact with the macrophages (Kupffer cells) and sinusoid-lining endothelial cells that line the hepatic sinusoids. Dim autofluorescence can be seen from the high metabolic activity of hepatocytes, thus demonstrating the liver architecture while simultaneously 'reporting on' tissue health and oxygen concentrations. Natural killer T cells crawl at high speed (10-30 μm/min) regardless of the direction of blood flow. Time-lapse video images were captured over 15 min, during which time the blood volume of the liver had turned over thousands of times. Video supplied by Tom Cameron and Mike Dustin.

Dendritic cells (green) demonstrate divergent motility depending on the niche that they occupy in subsequent phases of their maturation. Dermal dendritic cells have amoeboid morphology and crawl at an average speed of 11 μm/s in the dermis layer of the skin. This probably represents active 'patrolling' of the peripheral tissues. Video supplied by Guy Shakhar and Mike Dustin.

Dendritic cells (green) form an extensive network in the T cell zone of the lymph node. The dendritic cells show extensive probing movements but little crawling. These cells, however, do 'gesticulate' vigorously with their processes, an activity thought to promote interactions with the fast-moving T cells surrounding them. Video supplied by Guy Shakhar and Mike Dustin.