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Conventional dendritic cells (cDC) play key roles in immune induction, but what drives their heterogeneity and functional specialization is still ill-defined. Here we show that cDC-specific deletion of the transcriptional repressor Bcl6 in mice alters the phenotype and transcriptome of cDC1 and cDC2, while their lineage identity is preserved. Bcl6-deficient cDC1 are diminished in the periphery but maintain their ability to cross-present antigen to CD8+ T cells, confirming general maintenance of this subset. Surprisingly, the absence of Bcl6 in cDC causes a complete loss of Notch2-dependent cDC2 in the spleen and intestinal lamina propria. DC-targeted Bcl6-deficient mice induced fewer T follicular helper cells despite a profound impact on T follicular regulatory cells in response to immunization and mounted diminished Th17 immunity to Citrobacter rodentium in the colon. Our findings establish Bcl6 as an essential transcription factor for subsets of cDC and add to our understanding of the transcriptional landscape underlying cDC heterogeneity. [ABSTRACT FROM AUTHOR]

This article is part of the Dendritic Cell Guidelines article series, which provides a collection of state‐of‐the‐art protocols for the preparation, phenotype analysis by flow cytometry, generation, fluorescence microscopy, and functional characterization of mouse and human dendritic cells (DC) from lymphoid organs and various non‐lymphoid tissues. Here, we provide detailed procedures for a variety of multiparameter fluorescence microscopy imaging methods to explore the spatial organization of DC in tissues and to dissect how DC migrate, communicate, and mediate their multiple functional roles in immunity in a variety of tissue settings. The protocols presented here entail approaches to study DC dynamics and T cell cross‐talk by intravital microscopy, large‐scale visualization, identification, and quantitative analysis of DC subsets and their functions by multiparameter fluorescence microscopy of fixed tissue sections, and an approach to study DC interactions with tissue cells in a 3D cell culture model. While all protocols were written by experienced scientists who routinely use them in their work, this article was also peer‐reviewed by leading experts and approved by all co‐authors, making it an essential resource for basic and clinical DC immunologists. [ABSTRACT FROM AUTHOR]

Mononuclear phagocytes (MP), i.e., monocytes, macrophages, and dendritic cells (DCs), are essential for immune homeostasis via their capacities to clear pathogens, pathogen components, and non-infectious particles. However, tissue injury-related changes in local microenvironments activate resident and infiltrating MP towards pro-inflammatory phenotypes that contribute to inflammation by secreting additional inflammatory mediators. Efficient control of injurious factors leads to a switch of MP phenotype, which changes the microenvironment towards the resolution of inflammation. In the same way, MP endorses adaptive structural responses leading to either compensatory hypertrophy of surviving cells, tissue regeneration from local tissue progenitor cells, or tissue fibrosis and atrophy. Under certain circumstances, MP contribute to the reversal of tissue fibrosis by clearance of the extracellular matrix. Here we give an update on the tissue microenvironment-related factors that, upon tissue injury, instruct resident and infiltrating MP how to support host defense and recover tissue function and integrity. We propose that MP are not intrinsically active drivers of organ injury and dysfunction but dynamic amplifiers (and biomarkers) of specific tissue microenvironments that vary across spatial and temporal contexts. Therefore, MP receptors are frequently redundant and suboptimal targets for specific therapeutic interventions compared to molecular targets upstream in adaptive humoral or cellular stress response pathways that influence tissue milieus at a contextual level. [ABSTRACT FROM AUTHOR]

DNGR-1 (CLEC9A) is a receptor for necrotic cells required by DCs to cross-prime CTLs against dead cell antigens in mice. It is currently unknown how DNGR-1 couples dead cell recognition to cross-priming. Here we found that DNGR-1 did not mediate DC activation by dead cells but rather diverted necrotic cell cargo into a recycling endosomal compartment, favoring cross-presentation to CD [8.sup.+] T cells. DNGR-1 regulated cross-priming in non-infectious settings such as immunization with antigen-bearing dead cells, as well as in highly immunogenic situations such as infection with herpes simplex virus type 1. Together, these results suggest that DNGR-1 is a dedicated receptor for cross-presentation of cell-associated antigens. Our work thus underscores the importance of cross-priming in immunity and indicates that antigenicity and adjuvanticity can be decoded by distinct innate immune receptors. The identification of specialized receptors that regulate antigenicity of virus-infected cells reveals determinants of antiviral immunity that might underlie the human response to infection and vaccination., Introduction DCs are central players in the establishment and maintenance of self-tolerance, as well as in the induction of immunity against invading microorganisms (1, 2). In mice and humans, distinct [...]

Activator protein 1 (AP-1, also known as JUN) transcription factors are dimers of JUN, FOS, MAF and activating transcription factor (ATF) family proteins characterized by basic region and leucine zipper domains (1). Many AP-1 proteins contain defined transcriptional activation domains, but BATF and the closely related BATF3 (refs 2, 3) contain only a basic region and leucine zipper, and are considered to be inhibitors of AP-1 activity (3-8). Here we show that Batf is required for the differentiation of IL17-producing T helper ([T.sub.H]17) cells (9). [T.sub.H]17 cells comprise a [CD4.sup.+] T-cell subset that coordinates inflammatory responses in host defence but is pathogenic in autoimmunity (10-13). [Batf.sup.-/-] mice have normal [T.sub.H]1 and [T.sub.H]2 differentiation, but show a defect in [T.sub.H]17 differentiation, and are resistant to experimental autoimmune encephalomyelitis. [Batf.sup.-/-] T cells fail to induce known factors required for [T.sub.H]17 differentiation, such as RORγt (11) (encoded by Rorc) and the cytokine IL21 (refs 14-17). Neither the addition of IL21 nor the overexpression of RORγt fully restores IL17 production in [Batf.sup.-/-] T cells. The Il17 promoter is BATF-responsive, and after [T.sub.H]17 differentiation, BATF binds conserved intergenic elements in the Il17a-Il17f locus and to the Il17, Il21 and Il22 (ref. 18) promoters. These results demonstrate that the AP-1 protein BATF has a critical role in [T.sub.H]17 differentiation., In a gene expression survey (Supplementary Fig. la), we identified the basic leucine zipper transcription factor ATF-like (7) Batf to be highly expressed in [T.sub.H]1, [T.sub.H]2 and [T.sub.H]17 cells compared [...]

Plasmacytoid and conventional dendritic cells (pDC and cDC) are generated from progenitor cells in the bone marrow and commitment to pDCs or cDC subtypes may occur in earlier and later progenitor stages. Cells within the CD11c+MHCII−/loSiglec-H+CCR9lo DC precursor fraction of the mouse bone marrow generate both pDCs and cDCs. Here we investigate the heterogeneity and commitment of subsets in this compartment by single-cell transcriptomics and high-dimensional flow cytometry combined with cell fate analysis: Within the CD11c+MHCII−/loSiglec-H+CCR9lo DC precursor pool cells expressing high levels of Ly6D and lacking expression of transcription factor Zbtb46 contain CCR9loB220hi immediate pDC precursors and CCR9loB220lo (lo-lo) cells which still generate pDCs and cDCs in vitro and in vivo under steady state conditions. cDC-primed cells within the Ly6DhiZbtb46– lo-lo precursors rapidly upregulate Zbtb46 and pass through a Zbtb46+Ly6D+ intermediate stage before acquiring cDC phenotype after cell division. Type I IFN stimulation limits cDC and promotes pDC output from this precursor fraction by arresting cDC-primed cells in the Zbtb46+Ly6D+ stage preventing their expansion and differentiation into cDCs. Modulation of pDC versus cDC output from precursors by external factors may allow for adaptation of DC subset composition at later differentiation stages. The ontogeny of conventional and plasmacytoid dendritic cells (DC) and how these two cell types are related is not fully known. Here the authors identify a pool of bone marrow precursor cells expressing Ly6D Siglec-H and Zbtb46 that can differentiate into either cDC or pDC and show that type I IFN can limit cDC and favor pDC output from these precursors. [ABSTRACT FROM AUTHOR]

The article informs that according to a study by Hanc et al, nociceptors promote the production of specific inflammatory cytokines in mouse Fms-related tyrosine kinase 3 ligand (FLT3L)–induced bone marrow dendritic cells. It mentions that nociceptors can regulate dendritic cells in the skin by promoting the production of specific inflammatory cytokines, including IL-12p40, IL-6, and IL-23, through electrically mediated membrane depolarization and calcium influx in a contact-dependent manner.

Dendritic cells (DCs) are versatile controllers of immunity, which sense infection or tissue damage and, accordingly, initiate innate and adaptive effector responses. In recent years, it has become evident that DCs exist as an independent hematopoietic lineage comprising several developmentally distinct and functionally specialized subsets that are strategically located in all organs to defend the organism against invading pathogens. Here, we review the diversity of DC subtypes found across tissues and discuss our current understanding of the tissue-specific functions of these cell types. [ABSTRACT FROM AUTHOR]