Dendritic cells maintain anti-tumor immunity by positioning CD8 resident memory T cells in the skin through the CXCL16-CXCR6 axis

Tissue-resident memory (TRM) T cells are emerging as critical components of the immune response to cancer; yet, requirements for their ongoing function and maintenance remain unclear. Antigen presenting cells (APC) promote TRM cell differentiation and re-activation but have not been implicated in sustaining TRM cell responses. Here, we identified a novel role for dendritic cells in supporting tissue resident memory to melanoma. We showed that CD8 TRM cells remain in close proximity to dendritic cells in the skin. Depletion of CD11c+ cells results in rapid disaggregation and eventual loss of melanoma-specific TRM cells. Additionally, we determined that TRM migration and/or persistence requires chemotaxis and adhesion mediated by the CXCR6/CXCL16 axis. The interaction between CXCR6-expressing TRM cells and CXCL16-expressing APCs was found to be critical for sustaining TRM cell-mediated tumor protection. These findings substantially expand our knowledge of APC functions in tissue resident memory T cell homeostasis and longevity. comparing CD8 T cells, CD11c+CD11bneg and CD11c+CD11b+ monocytes from melanoma associated vitiligo skin of mice