PD-L1 Reverse Signaling in Dermal Dendritic Cells Promotes Dendritic Cell Migration Required for Skin Immunity

Area of Science:

• Immunology
• Cell Biology

Background:

• The extracellular domain of programmed death ligand 1 (PD-L1) and its interaction with PD-1 on T cells are well-characterized.
• The intracellular signaling functions of PD-L1 remain largely unexplored, particularly its role in immune cell trafficking.

Purpose of the Study:

• To investigate the role of the intracellular domain of PD-L1 in dendritic cell (DC) migration.
• To identify specific signaling motifs within PD-L1 that regulate DC trafficking and immune responses.

Main Methods:

• Utilized a mutant mouse model lacking a functional PD-L1 intracellular signaling motif.
• Analyzed DC migration from skin to draining lymph nodes (dLNs) during inflammatory conditions.
• Assessed T-cell priming and chemokine receptor signaling pathways in DCs.

Main Results:

• Identified a critical TSS signaling motif within the intracellular domain of PD-L1.
• Demonstrated that this motif is essential for chemokine-mediated DC migration to the dLN during inflammation.
• Observed a significant reduction in T-cell priming in the absence of functional PD-L1 intracellular signaling due to impaired DC migration.

Conclusions:

• The intracellular domain of PD-L1 plays a major role in controlling DC migration.
• The identified TSS motif is vital for chemokine receptor signaling, ERK phosphorylation, and actin polymerization in DCs, thereby regulating T-cell priming.