Morphology of migrating dendritic cells in 3D collagen gels and concluding scheme. (A) TAMRA-labeled DCs were added to 1.6 mg/mL collagen, followed by fiber assembly for 30 minutes at 37°C. Polymerized gels were overlaid with 0.6 μg/mL CCL19. After 60 minutes, snapshots of DCs migrating at 37°C, 5% CO₂ in the 3D collagen gel toward CCL19 were obtained by spinning disc confocal microscopy. DC morphologies result from 3D reconstruction of confocal stacks (MetaMorph) and Surpass processing with Imaris software. Scale bars represent 5 μm. Objective: Plan-APOCHROMAT 40×/0.95 Korr oil (Zeiss). (B) Concluding scheme about the decisive role of coordinated actin protrusions for leukocyte migration in complex 3D environments.