PGE₂ is essential for migration of vaccine DCs. (A) Random migration on fibronectin. cDCs, vaccine DCs, and vaccine PGE₂ DCs were added to a fibronectin-coated plate, and migration of individual cells was monitored for 60 minutes. Data represent the percentage of migrating cells (mean ± SEM) of 3 experiments with cells from different donors. For each experiment, migration of 50 cells per condition was monitored. *P < .05. **P < .01. (B) The expression of CCR7 (bold line) on cDCs, vaccine DCs, and vaccine PGE₂ DCs was measured by flow cytometry. The thin line represents the isotype control. (C) CCR7-mediated chemotaxis of cDCs, vaccine DCs, and vaccine PGE₂ DCs was determined by the number of cells that had migrated into the lower compartment of a transwell system containing 10 or 100 ng/mL CCL21, counted by flow cytometry. To measure spontaneous migration, cells were incubated in a transwell without CCL21 in the upper and lower compartment (medium) or with 100 ng/mL CCL21 in both compartments (kinesis). Migration of cDCs in the presence of 100 ng/mL CCL21 was regarded as 100% (100% corresponds to 26 190 ± 10 636 migrated cells). The graph represents means ± SEM from 3 experiments (with cells from different donors) performed in duplicate. *Significant difference (P < .05) compared with medium. #Significant difference (P < .05) compared with vaccine DCs.