Project description:Lung-resident conventional dendritic cells (cDCs) coordinate immune responses to respiratory viruses in the respiratory tract or after migration to mediastinal lymph nodes (mLN). Migratory DCs include cDC1s (CD103+XCR1+CD24hi) expressing IRF8 or cDC2s (CD11b+SIRPa+CD24+) expressing IRF4. IRF4+ cDC2s are divided into a CD24hi subset that requires IRF4 for differentiation and a CD24int subset that is present in the absence of IRF4. During influenza A virus (IAV) infection of mice, we characterized the kinetics of cDC2 subset accumulation in the lung and mLN and their differences in IRF4-dependent gene expression and function. We found that the two IRF4-expressing cDC2 subsets upregulated CD86 to high levels, produced IL-12p40 and the chemokines CCL17 and CCL2, and were capable of acquiring antigen in vivo and activating antigen-specific CD8+ T cells. Notably, the CD11b+CD24int cDC2 subset expressed canonical cDC markers and transcription factors and expanded to high numbers in the lung and mLN by day 6 post-infection. Transcriptome analyses on day 5 post-infection revealed that the CD11b+CD24int cDC2 subset expressed both IRF4 and IRF8 and harbored an elevated interferon response signature compared to the CD11b+CD24hi subset. Analyses of mice lacking Irf4 in CD11c+ cells showed that IRF4 promoted the function of CD11b+CD24int cDC2s, including the capacity to migrate to mLN and to produce CCL17 and CCL22, consistent with their altered gene expression profile in the absence of IRF4. In sum, our data show that the two lung-resident CD11b+ cDC2 subsets present in naïve mice elaborated distinct and common functional responses regulated by IRF4 during IAV infection.
Project description:DNA topoisomerase II-binding protein 1 (TopBP1) plays a vital role in V(D)J recombination during B and T cell development. However, its role in the development of conventional dendritic cells (cDCs) remains unexplored. Mice with DC-specific depletion of TopBP1 (TopBP1cKO) showed accelerated tumor progression due to impaired anti-tumor immunity, characterized by cDC deficiency and pre-DC accumulation. Notably, Flt3 ligand (Flt3L)-mediated tumor immunotherapy was ineffective in TopBP1cKO tumor-bearing mice. Our study demonstrates that TopBP1 is required not only for the steady-state differentiation of total cDCs, including both cDC1 and cDC2, but also for the terminal differentiation of XCR1⁻CD24⁺ emergency progenitors (EPs; CD11c⁺cKit⁺) into XCR1⁺CD24⁺ cDC1s in response to Flt3L. Furthermore, we revealed that TopBP1 directly interacts with PU.1 and IRF8, key transcription factors (TFs) required for cDC development, triggering the expression of their downstream target genes. These findings identify TopBP1 as a crucial factor for cDC development and Flt3L-driven EP differentiation into cDC1s, revealing that the function of key TFs for cDC development is mediated via interaction with TopBP1. Our work underscores the importance of TopBP1 in promoting cDC development and the therapeutic efficacy of Flt3L-mediated tumor immunotherapy.
Project description:Conventional dendritic cells (cDC) consist of two functionally and phenotypically distinct subsets, cDC1 and cDC2, whose development is dependent on distinct sets of transcription factors. Interferon regulatory factor 8 (IRF8) is required at multiple stages of cDC1 development, but its role in mature cDC1 remains unclear. Here we used XCR1-cre to delete Irf8 in committed cDC1 and demonstrate that Irf8 is required for maintaining the identify of cDC1 but not their survival. In the absence of Irf8, committed cDC1 (“ex-cDC1”) acquired the transcriptional, functional and chromatin accessibility properties of cDC2. This conversion was independent on Irf4 and was associated with decreased accessibility in putative IRF8, Batf3 and composite AP-1-IRF (AICE) binding elements, together with increased accessibility of cDC2 associated transcription factor binding elements. Thus, IRF8 expression by committed cDC1 is required for preventing their conversion into cDC2.
Project description:ChIP-seq analysis was performed in an adult T-cell leukemia/lymphoma cell line (TL-Om1) to analyze DNA bindings of IRF4 in TL-Om1 cells.
Project description:Conventional type 2 Dendritic Cells (cDC2) in the skin are cell subsets primarily responsible for the priming of T-helper type 2 (TH2) responses in the draining LN. The local inflammatory milieu has been demonstrated to condition cDC2 to promote such responses. To characterise the cDC2 response to the cytokine IFN-I, we performed bulk RNAseq on sorted cDC2 subsets from IFNAR∆CD11c and IFNARWT mice following treatment with an allergen.
Project description:Flt3 ligand (Flt3L) promotes an increased generation of type 1 conventional dendritic cells (cDC1s), resulting in enhanced immunity against infections and cancer. Here, we employ cellular barcoding to understand how Flt3L regulates single haematopoietic stem and progenitor cell (HSPC) fate. Our results demonstrate that although Flt3L stimulation can recruit some additional cDC1-generating HSPCs, the major contributing factor to higher cDC1 numbers is through enhanced clonal expansion. This selective cDC1 expansion occurs primarily via multi-/oligo-potent clones, without compromising their clonal output to other lineages. We then develop Divi-Seq to simultaneously profile division history, surface phenotype and the transcriptional state of single HSPCs during the early phase of the response. We discover that Flt3L-responsive HSPCs maintain a proliferative ‘early progenitor’-like state, which leads to a selective emergence of CD11c+cKit+ transitional precursors with high cellular output to cDC1s. These findings inform the mechanistic action of Flt3L in natural immunity and immunotherapy.