CD8+ T Cells Orchestrate pDC-XCR1+ Dendritic Cell Spatial and Functional Cooperativity to Optimize Priming

Adaptive cellular immunity is initiated by antigenspecific interactions between T lymphocytes and dendritic cells (DCs). Plasmacytoid DCs (pDCs) support antiviral immunity by linking innate and adaptive immune responses. Here we examined pDC spatiotemporal dynamics during viral infection to uncover when, where, and how they exert their functions. We found that pDCs accumulated at sites of CD8(+) T cell antigen-driven activation in a CCR5-dependent fashion. Furthermore, activated CD8(+) T cells orchestrated the local recruitment of lymph node-resident XCR1 chemokine receptor-expressing DCs via secretion of the XCL1 chemokine. Functionally, this CD8+ T cell-mediated reorganization of the local DC network allowed for the interaction and cooperation of pDCs and XCR1(+) DCs, thereby optimizing XCR1(+) DC maturation and cross-presentation. These data support a model in which CD8(+) T cells upon activation create their own optimal priming microenvironment by recruiting additional DC subsets to the site of initial antigen recognition.