In Vivo Tracking of Dendritic Cell Migration.

Dendritic cells (DCs) in peripheral tissue serve as a sentinel to invasion and maintain tolerance. They ingest and carry antigens to the draining lymph nodes and present antigens to antigen-specific T cells to initiate acquired immune responses. Thus, understanding DC migration from peripheral tissues and function is critical for understanding DCs' roles in immune homeostasis. Here, we introduced the KikGR in vivo photolabeling system, an ideal tool for monitoring precise cellular movements and related functions in vivo under physiological conditions and during various immune responses that occur in pathologic condition. Using a mouse line expressing photoconvertible fluorescent protein KikGR, we can label DCs in peripheral tissues by changing the color of KikGR from green to red after exposure to violet light and accurately track DC migration from each peripheral tissue to its respective draining lymph nodes.

Near-infrared photoimmunotherapy induced tumor cell death enhances tumor dendritic cell migration.

Near-infrared photoimmunotherapy (NIR-PIT) selectively kills tumor cells to which the photo-absorber dye IR700DX-conjugated antibodies are bound and induces a systemic anti-tumor immune response. NIR-PIT induces immunogenic cell death (ICD), releases damage-associated molecular patterns (DAMPs) molecules from dying tumor cells, and activates dendritic cells (DCs). However, it is unclear whether NIR-PIT affects migration of tumor-infiltrating (Ti)-DCs to draining lymph nodes (dLNs), where a systemic anti-tumor response is induced. Here, we utilized in vivo photolabeling of Ti-DCs in tumors in photoconvertible protein Kikume Green-Red (KikGR) mice to show that NIR-PIT enhanced migration of Ti-DCs including cDC1s, cDC2s, and CD326+ DCs to dLNs. This effect was abolished by blocking adenosine triphosphate (ATP), one of the DAMPs molecules, as well as by inhibition of Gαi signaling by pertussis toxin. Thus, ICD induction by NIR-PIT stimulates Ti-DC migration to dLNs via ATP-P2X7 receptor and Gαi protein-coupled receptor signaling pathways and may augment tumor antigen presentation to induce anti-tumor T cells in dLNs.