CD81 is not required for CCL19-induced BM-DC chemotaxis in 3-dimensional collagen gels. Chemotactic migration of BM-DCs from CD81^−/− and wild-type mice in 3-dimensional collagen type I gels (1.6 μg/mL) in response to a stable CCL19 gradient (600 ng/mL). (A) Migration plots of 60 cells/sample monitored by time-lapse videomicroscopy over a period of 3 hours by capturing digital images every 5 minutes. Quantification of average migratory speed (velocity; B) and y-forward migration index (y-FMI, which means directional persistence toward the chemokine; C) of migrating BM-DCs after manual tracking of motile cells. Results are representative for 1 experiment of 3. Error bars indicate ± SD. ns, not significant. ***P ≤ .001.