Investigation of fascin1, a marker of mature dendritic cells, reveals a New role for IL-6 signaling in chemotaxis.

Migration of mature dendritic cells (DCs) to lymph nodes is critical for the initiation of adaptive immunity. While CCR7, a a G-protein-coupled receptor for CCL19/21 chemokines, is known to be essential for chemotaxis of mature DCs, the molecular mechanism linking inflammation to chemotaxis remains unclear. We previously demonstrated that fascin1, an actin-bundling protein, increases chemotaxis of mature DCs. In this paper we showed that fascin1 enhanced Interleukin (IL)-6 secretion and signaling. Furthermore, we demonstrated that IL-6 signaling is required for chemotaxis. Blockage of IL-6 signaling in WT DCs with an anti-IL-6 receptorα (IL-6Rα) antibody inhibited chemotaxis toward CCL19. Likewise, knockout (KO) of IL-6Rα inhibited chemotaxis of BMDCs. The addition of soluble IL-6Rα and IL-6 rescued chemotaxis of IL-6Rα KO BMDCs, underscoring the role of IL-6 signaling in chemotaxis. We found that IL-6 signaling is required for internalization of CCR7, the initial step of CCR7 recycling. CCR7 recycling is known to be essential for CCR7-mediated chemotaxis, explaining why IL-6 signaling is needed for chemotaxis of mature DCs. Our results have identified IL-6 signaling as a new regulatory pathway for CCR7/CCL19-mediated chemotaxis, and suggest that rapid migration of mature DCs to lymph nodes depends on inflammation-associated IL-6 signaling.