Category: Innate immunity
Cross-presenting dendritic cells (DC) play a critical role in regulating immunity and tolerance. A subset of DC expressing the chemokine receptor XCR1 have superior antigen cross-presentation ability and are crucial for eliciting CD8+ T cell responses. Understanding the importance of cross-priming for generating CD8+ T cell response against tumor-derived, viral, or self-antigens will help elucidate therapeutic targets for intervention. To understand the role XCR1+DC play in cross-presentation, we used genetically modified mice to selectively target XCR1+DC subset. We generated XCR1-RYDL (Rosa-YFP-DTR-Luciferase) mice, which express luciferase for detection of XCR1+ cells and Diphtheria Toxin Receptor (DTR) for deletion of XCR1+ cells to deplete XCR1+DC in vivo. Injection of Diptheria Toxin (DT) resulted in deletion of XCR1+DC in XCR1-RYDL mice. DT treatment resulted in up to 80% reduction of XCR1+DC subset in spleen, thymus, and mesenteric lymph node (MLN), corresponding with no change in conventional T cell or Foxp3+ regulatory T cell pool in vivo. Furthermore, DT-treated mice were defective in generating antigen-specific CD8+ T cell response, exhibiting ~3-fold reduction in ovalbumin-specific CD8+ T cells in response to immunization with ovalbumin and a Toll-like receptor 3 (TLR3) agonist. Most notably, deletion of XCR1+DC prior to tumor implantation resulted in up to 3-fold increase in tumor burden in DT-treated mice. Thus, XCR1+DC are required for CD8+ T cell activation and play a role in generating anti-tumor responses. These findings suggest that XCR1-RYDL mouse model offers a unique ability to study the requirement and function of XCR1+DC in initiation and regulation of anti-tumor immunity.