Tracking the migration of dendritic cells by in vivo optical imaging.

We report herein a method to track the migration of dendritic cells (DCs) using optical imaging. With the assistance of the delivery module, fluorescein isothiocyanate (FITC) could internalize inside DCs within 15 minutes of incubation. The fluorescent signal was mostly cytoplasmic and could be detected using in vivo imaging. Furthermore, we observed that the probe did not interfere with the DCs maturation as we assessed the expression of several surface markers. The labeled DCs secreted interleukin-12 (IL-12) and tumor necrosis factor-alpha (TNF-alpha) and stimulated the proliferation of CD4+ T lymphocytes responding to lipopolysaccharide (LPS) stimulation. We have systematically compared the probe uptake between mature and immature DCs. The study showed that the latter phagocytosed the probe slightly better than the former. Intravital imaging of treated mice showed the migration of DCs to lymph nodes (LNs), which is confirmed by immunohistochemistry. Taken together, we demonstrated the potential use of optical imaging for tracking the migration of DCs and homing in vivo. The delivery molecules could also be used on other imaging modalities or for delivery of antigens.