CCR7+ activated dendritic cells are essential for spontaneous and immunotherapy-driven anti-tumor immunity.

Single-cell transcriptomics identifies a convergent activation state of conventional dendritic cells (cDCs) shared by type 1 and type 2 cDCs (cDC1s and cDC2s). These activated DCs (actDCs) are characterized by co-expression of T cell-stimulating and inhibitory molecules. Here, we examined the functional contribution of actDCs to anti-tumor immunity by developing mouse models that leverage CCR7 expression to conditionally label or ablate actDCs. The capacity of cDCs to stimulate tumor-specific cytotoxic T lymphocytes (CTLs) was restricted to the actDC state. cDC1- and cDC2-derived actDCs supported CTL priming through cross-presentation and cross-dressing, respectively, with the latter occurring in a cancer type-dependent manner. actDCs were required for the activation of naive CTLs in tumor-draining lymph nodes and for sustaining effector CTL function within tumors. Consequently, ablation of actDCs impaired spontaneous tumor control and responses to immune checkpoint blockade or adoptive T cell therapy. Thus, the actDC state emerges as a critical determinant of cDC-mediated anti-tumor immunity.