Host type I IFN signals are required for antitumor CD8⁺ T cell responses through CD8α⁺ dendritic cells

Despite lack of tumor control in many models, spontaneous T cell priming occurs frequently in response to a growing tumor. However, the innate immune mechanisms that promote natural antitumor T cell responses are undefined. In human metastatic melanoma, there was a correlation between a type I interferon (IFN) transcriptional profile and T cell markers in metastatic tumor tissue. In mice, IFN-β was produced by CD11c⁺ cells after tumor implantation, and tumor-induced T cell priming was defective in mice lacking IFN-α/βR or Stat1. IFN signaling was required in the hematopoietic compartment at the level of host antigen-presenting cells, and selectively for intratumoral accumulation of CD8α⁺ dendritic cells, which were demonstrated to be essential using Batf3^-/- mice. Thus, host type I IFNs are critical for the innate immune recognition of a growing tumor through signaling on CD8α⁺ DCs.