Resident memory T cell precursors in tumor draining lymph nodes require type-1 IFN for optimal differentiation

Resident memory (Trm) cells play an essential role in anti-tumor immunity. However, little is known about the precursors that differentiate into protective Trm populations against cancer. Here we employed an established model of B16 melanoma neoadjuvant anti-CD4 therapy, to track tumor antigen-specific CD8+ T cells through tissues and across time; from their priming as effectors to their differentiation into Trm. We show that tumor-draining lymph nodes (TDLNs) contain Teff cells that begin to express canonical Trm markers CD103 and CD69. These tumor-specific Teff cells seeded skin and tumor during the effector phase of the response, although egress from these tissues was not required Trm development in LNs. Paired scRNAseq/scTCRseq was used to identify Teff clonotypes in TDLNs and trace their differentiation, in real-time, into Trm populations. We found that expanded clonotypes favored the Trm fate and were unlikely to co-differentiate into other lineages. Precursors of Trm (pre-Trm) clonotypes that subsequently seeded populations throughout tumors, LNs, and skin, were characterized by early expression of tissue residency, stemness, and type-1 IFN sensing genes. These multipotent pre-Trm cells sensed plasmacytoid dendritic cell-derived type-1 interferons in TDLNs, and their expression of interferon alpha receptor was required for their formation of Trm populations in LNs but not in skin. These findings reveal the defining features of pre-Trm cells in response to tumor antigens, and reveal a previously unappreciated role for type-1 IFNs in programming regional Trm immunity to cancer. One Sentence SummaryAnti-tumor effector CD8 T cells adopt early characteristics of tissue residency and stemness, and rely on the sensing of type-1 interferons for their local differentiation into resident memory T cells.