Critical Roles of a Dendritic Cell Subset Expressing a Chemokine Receptor, XCR1

Dendritic cells (DCs) consist of various subsets that play crucial roles in linking innate and adaptive immunity. In the murine spleen, CD8α+ DCs exhibit a propensity to ingest dying/dead cells, produce proinflammatory cytokines, and cross-present Ags to generate CD8+ T cell responses. To track and ablate CD8α+ DCs in vivo, we generated XCR1-venus and XCR1-DTRvenus mice, in which genes for a fluorescent protein, venus, and a fusion protein consisting of diphtheria toxin receptor and venus were knocked into the gene locus of a chemokine receptor, XCR1, which is highly expressed in CD8α+ DCs. In both mice, venus+ cells were detected in the majority of CD8α+ DCs, but they were not detected in any other cells, including splenic macrophages. Venus+CD8α+ DCs were superior to venus−CD8α+ DCs with regard to their cytokine-producing ability in response to TLR stimuli. In other tissues, venus+ cells were found primarily in lymph node (LN)-resident CD8α+, LN migratory and peripheral CD103+ DCs, which are closely related to splenic CD8α+ DCs, although some thymic CD8α−CD11b− and LN CD103−CD11b− DCs were also venus+. In response to dsRNAs, diphtheria toxin–treated XCR1-DTR mice showed impaired CD8+ T cell responses, with retained cytokine and augmented CD4+ T cell responses. Furthermore, Listeria monocytogenes infection and anti–L. monocytogenes CD8+ T cell responses were defective in diphtheria toxin–treated XCR1-DTRvenus mice. Thus, XCR1-expressing DCs were required for dsRNA- or bacteria-induced CD8+ T cell responses. XCR1-venus and XCR1-DTRvenus mice should be useful for elucidating the functions and behavior of XCR1-expressing DCs, including CD8α+ and CD103+ DCs, in lymphoid and peripheral tissues.