DNGR-1-tracing marks an ependymal cell subset with damage-responsive neural stem cell potential

Cells with latent stem ability can contribute to mammalian tissue regeneration after damage. Whether the central nervous system (CNS) harbors such cells remains controversial. Here, we report that DNGR-1 lineage tracing in mice identifies an ependymal cell subset, wherein resides latent regenerative potential. We demonstrate that DNGR-1-lineage-traced ependymal cells arise early in embryogenesis (E11.5) and subsequently spread across the lining of cerebrospinal fluid (CSF)-filled compartments to form a contiguous sheet from the brain to the end of the spinal cord. In the steady state, these DNGR-1-traced cells are quiescent, committed to their ependymal cell fate, and do not contribute to neuronal or glial lineages. However, trans-differentiation can be induced in adult mice by CNS injury or in vitro by culture with suitable factors. Our findings highlight previously unappreciated ependymal cell heterogeneity and identify across the entire CNS an ependymal cell subset wherein resides damage-responsive neural stem cell potential.

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DNGR-1 is expressed early in mouse embryogenesis in a subset of ventricular progenitors

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DNGR-1 tracing shows that those progenitors give rise to a subset of ependymal cells

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DNGR-1-traced ependymal cells have latent regenerative potential

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DNGR-1-traced ependymal cells can be mobilized by local injury

The In Vitro Differentiation of Human CD141+CLEC9A+ Dendritic Cells from Mobilized Peripheral Blood CD34+ Hematopoietic Stem Cells

As shown in various preclinical studies, conventional type-1 dendritic cells, or cDC1s, play a critical role in the immunological rejection of tumors and in the defense against pathogens. This indispensability stems from their potent capacity to activate cytotoxic T cells, especially via the cross-presentation of exogenous antigens. For this reason, cDC1s have become an attractive target for immunotherapy. Here we report a simplified method for generating large numbers of cDC1-like cells in vitro from mobilized human peripheral blood CD34+ hematopoietic stem cells using FMS-like tyrosine kinase 3 ligand (FLT3L) and granulocyte-macrophage colony-stimulating factor (GM-CSF). An important aspect of this Protocol is the growth of cells on a non-tissue culture-treated surface rather than on a tissue culture-treated surface since the latter suppresses cDC1-marker expression. The resulting CD11c+ DCs express high levels of cDC1-specific markers such as CD141, CLEC9A, TLR3, and several DC maturation markers. Compared to alternative differentiation methods, this method generates large numbers of cDC1-like cells without the need for immortalized feeder cells and should prove useful for studying cDC1 immunobiology and clinical applications of this DC subset. © 2022 Wiley Periodicals LLC. Basic Protocol: Generation of human CD141+CLEC9A+ dendritic cells from mobilized peripheral blood CD34+ hematopoietic stem cells Support Protocol: Flow cytometric immunophenotyping of CD141+ dendritic cells.

Upregulation of type 1 conventional dendritic cells implicates antigen cross-presentation in multisystem inflammatory syndrome

Background

Multisystem inflammatory syndrome in children (MIS-C) is an acute, febrile, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-associated syndrome, often with cardiohemodynamic dysfunction. Insight into mechanism of disease is still incomplete.

Objective

Our objective was to analyze immunologic features of MIS-C patients compared to febrile controls (FC).

Methods

MIS-C patients were defined by narrow criteria, including having evidence of cardiohemodynamic involvement and no macrophage activation syndrome. Samples were collected from 8 completely treatment-naive patients with MIS-C (SARS-CoV-2 serology positive), 3 patients with unclassified MIS-C–like disease (serology negative), 14 FC, and 5 MIS-C recovery (RCV). Three healthy controls (HCs) were used for comparisons of normal range. Using spectral flow cytometry, we assessed 36 parameters in antigen-presenting cells (APCs) and 29 in T cells. We used biaxial analysis and uniform manifold approximation and projection (UMAP).

Results

Significant elevations in cytokines including CXCL9, M-CSF, and IL-27 were found in MIS-C compared to FC. Classic monocytes and type 2 dendritic cells (DCs) were downregulated (decreased CD86, HLA-DR) versus HCs; however, type 1 DCs (CD11c⁺CD141⁺CLEC9A⁺) were highly activated in MIS-C patients versus FC, expressing higher levels of CD86, CD275, and atypical conventional DC markers such as CD64, CD115, and CX3CR1. CD169 and CD38 were upregulated in multiple monocyte subtypes. CD56^dim/CD57⁻/KLRG^hi/CD161⁺/CD38⁻ natural killer (NK) cells were a unique subset in MIS-C versus FC without macrophage activation syndrome.

Conclusion

Orchestrated by complex cytokine signaling, type 1 DC activation and NK dysregulation are key features in the pathophysiology of MIS-C. NK cell findings may suggest a relationship with macrophage activation syndrome, while type 1 DC upregulation implies a role for antigen cross-presentation.

Downregulated Expression of CLEC9A as Novel Biomarkers for Lung Adenocarcinoma

Purpose

Abnormal CLEC9A expression is concerned with carcinogenesis. However, the role of CLEC9A in lung adenocarcinoma (LUAD) remains unknown. The goal of this study was to reveal the role of CLEC9A in LUAD based on bioinformatics and cellular functional experiments.

Materials and methods

Data available from The Cancer Genome Atlas (TCGA) were employed to study CLEC9A expression and mutations in LUAD. Expression and alterations of CLEC9A were analyzed using UALCAN and cBioPortal, respectively. Kaplan-Meier analysis was used to analyze the effect of CLEC9A on the survival of LUAD. Protein-protein interaction (PPI) network was built using GeneMANIA analysis. The similar genes of CLEC9A were obtained using GEPIA analysis, while co-expression genes correlated with CLEC9A were identified using LinkedOmics analysis. The effects of CLEC9A expression on immune cell infiltration was assessed. The effect of CLEC9A on the proliferation, apoptosis, cell cycle distribution, and invasion of human LUAD cells was detected in the LUAD cell line.

Results

CLEC9A was downregulated and the CLEC9A gene was often altered in LUAD. The survival of LUAD patients was correlated with the expression level of CLEC9A. The similar genes of CLEC9A were linked to functional networks involving positive regulation of interleukin-12 production, plasma membrane and CD40 receptor binding, primary immunodeficiency, intestinal immune network for IgA production, and cell adhesion molecules pathways. Cell cycle, apoptosis, EMT, and RAS/MAPK were significantly enriched pathways in positive and negative correlation genes with CLEC9A. A difference in the immune infiltration level of immune cell between the high and low CLEC9A expression groups was observed. Somatic cell copy number alternations (CNAs) of the CLEC9A, including arm-level gain and arm-level deletion, observably changed the infiltration levels of B cells, CD4+ T cells, macrophages, and neutrophils in LUAD. Except for LAG3, the expression of CD274, CTLA4, PDCD1, and TIGIT was positively correlated with the expression level of CLEC9A. After transfection, overexpression and knockdown of CLEC9A could affect the proliferation, apoptosis, cell cycle distribution, and invasion of LUAD cells.

Conclusion

CLEC9A is associated with prognosis and tumor immune microenvironment of LUAD, suggesting that CLEC9A may be considered as a novel biomarker for LUAD.

Secreted gelsolin inhibits DNGR-1-dependent cross-presentation and cancer immunity

Cross-presentation of antigens from dead tumor cells by type 1 conventional dendritic cells (cDC1s) is thought to underlie priming of anti-cancer CD8+ T cells. cDC1 express high levels of DNGR-1 (a.k.a. CLEC9A), a receptor that binds to F-actin exposed by dead cell debris and promotes cross-presentation of associated antigens. Here, we show that secreted gelsolin (sGSN), an extracellular protein, decreases DNGR-1 binding to F-actin and cross-presentation of dead cell-associated antigens by cDC1s. Mice deficient in sGsn display increased DNGR-1-dependent resistance to transplantable tumors, especially ones expressing neoantigens associated with the actin cytoskeleton, and exhibit greater responsiveness to cancer immunotherapy. In human cancers, lower levels of intratumoral sGSN transcripts, as well as presence of mutations in proteins associated with the actin cytoskeleton, are associated with signatures of anti-cancer immunity and increased patient survival. Our results reveal a natural barrier to cross-presentation of cancer antigens that dampens anti-tumor CD8+ T cell responses.

Human CLEC9A antibodies deliver Wilms' tumor 1 (WT1) antigen to CD141+ dendritic cells to activate naïve and memory WT1-specific CD8+ T cells

Objectives

Vaccines that prime Wilms' tumor 1 (WT1)‐specific CD8⁺ T cells are attractive cancer immunotherapies. However, immunogenicity and clinical response rates may be enhanced by delivering WT1 to CD141⁺ dendritic cells (DCs). The C‐type lectin‐like receptor CLEC9A is expressed exclusively by CD141⁺ DCs and regulates CD8⁺ T‐cell responses. We developed a new vaccine comprising a human anti‐CLEC9A antibody fused to WT1 and investigated its capacity to target human CD141⁺ DCs and activate naïve and memory WT1‐specific CD8⁺ T cells.

Methods

WT1 was genetically fused to antibodies specific for human CLEC9A, DEC‐205 or β‐galactosidase (untargeted control). Activation of WT1‐specific CD8⁺ T‐cell lines following cross‐presentation by CD141⁺ DCs was quantified by IFNγ ELISPOT. Humanised mice reconstituted with human immune cell subsets, including a repertoire of naïve WT1‐specific CD8⁺ T cells, were used to investigate naïve WT1‐specific CD8⁺ T‐cell priming.

Results

The CLEC9A‐WT1 vaccine promoted cross‐presentation of WT1 epitopes to CD8⁺ T cells and mediated priming of naïve CD8⁺ T cells more effectively than the DEC‐205‐WT1 and untargeted control‐WT1 vaccines.

Conclusions

Delivery of WT1 to CD141⁺ DCs via CLEC9A stimulates CD8⁺ T cells more potently than either untargeted delivery or widespread delivery to all Ag‐presenting cells via DEC‐205, suggesting that cross‐presentation by CD141⁺ DCs is sufficient for effective CD8⁺ T‐cell priming in humans. The CLEC9A‐WT1 vaccine is a promising candidate immunotherapy for malignancies that express WT1.

Large-Scale Human Dendritic Cell Differentiation Revealing Notch-Dependent Lineage Bifurcation and Heterogeneity

The ability to generate large numbers of distinct types of human dendritic cells (DCs) in vitro is critical for accelerating our understanding of DC biology and harnessing them clinically. We developed a DC differentiation method from human CD34⁺ precursors leading to high yields of plasmacytoid DCs (pDCs) and both types of conventional DCs (cDC1s and cDC2s). The identity of the cells generated in vitro and their strong homology to their blood counterparts were demonstrated by phenotypic, functional, and single-cell RNA-sequencing analyses. This culture system revealed a critical role of Notch signaling and GM-CSF for promoting cDC1 generation. Moreover, we discovered a pre-terminal differentiation state for each DC type, characterized by high expression of cell-cycle genes and lack of XCR1 in the case of cDC1. Our culture system will greatly facilitate the simultaneous and comprehensive study of primary, otherwise rare human DC types, including their mutual interactions.

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A CD34⁺ cell culture protocol yields large numbers of human pDCs and cDC1/2s

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Notch signaling is critical for cDC1 generation and GM-CSF has a synergistic effect

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scRNAseq confirms homology of in-vitro-derived DC types to their blood counterparts

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CLEC9A-positive XCR1-negative cells were identified as immediate precursors of cDC1s

Myosin II Synergizes with F-Actin to Promote DNGR-1-Dependent Cross-Presentation of Dead Cell-Associated Antigens

Conventional type 1 DCs (cDC1s) excel at cross-presentation of dead cell-associated antigens partly because they express DNGR-1, a receptor that recognizes exposed actin filaments on dead cells. In vitro polymerized F-actin can be used as a synthetic ligand for DNGR-1. However, cellular F-actin is decorated with actin-binding proteins, which could affect DNGR-1 recognition. Here, we demonstrate that myosin II, an F-actin-associated motor protein, greatly potentiates the binding of DNGR-1 to F-actin. Latex beads coated with F-actin and myosin II are taken up by DNGR-1⁺ cDC1s, and antigen associated with those beads is efficiently cross-presented to CD8⁺ T cells. Myosin II-deficient necrotic cells are impaired in their ability to stimulate DNGR-1 or to serve as substrates for cDC1 cross-presentation to CD8⁺ T cells. These results provide insights into the nature of the DNGR-1 ligand and have implications for understanding immune responses to cell-associated antigens and for vaccine design.

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Myosin II amplifies the activity of the DNGR-1 ligand F-actin

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Lack of myosin II in donor cells reduces DNGR-1-dependent cross-presentation

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Beads with F-actin and myosin II can target antigens to cDC1 for CD8 T cell priming

Exposure to the antimicrobial peptide LL-37 produces dendritic cells optimized for immunotherapy

Immunization of patients with autologous, ex vivo matured dendritic cell (DC) preparations, in order to prime antitumor T-cell responses, is the focus of intense research. Despite progress and approval of clinical approaches, significant enhancement of these personalized immunotherapies is urgently needed to improve efficacy. We show that immunotherapeutic murine and human DC, generated in the presence of the antimicrobial host defense peptide LL-37, have dramatically enhanced expansion and differentiation of cells with key features of the critical CD103⁺/CD141⁺ DC subsets, including enhanced cross-presentation and co-stimulatory capacity, and upregulation of CCR7 with improved migratory capacity. These LL-37-DC enhanced proliferation, activation and cytokine production by CD8⁺ (but not CD4⁺) T cells in vitro and in vivo. Critically, tumor antigen-presenting LL-37-DC increased migration of primed, activated CD8⁺ T cells into established squamous cell carcinomas in mice, and resulted in tumor regression. This advance therefore has the potential to dramatically enhance DC immunotherapy protocols.

The levels of DNGR-1 and its ligand-bearing cells were altered after human and simian immunodeficiency virus infection

Dendritic cell NK lectin Group Receptor-1 (DNGR-1), also known as C-type lectin domain family 9, member A (CLEC9A), is a member of C-type lectin receptor superfamily expressed primarily on dendritic cells (DC) that excel in cross-presentation of exogenous antigens. To find out whether and how it is affected in human immunodeficiency virus infections or acquired immunodeficiency syndromes (HIV/AIDS), DNGR-1 expression and DNGR-1-binding cells in simian/human immunodeficiency virus (SHIV) and simian immunodeficiency virus (SIV)-infected rhesus macaques and antiretroviral therapy (ART)-treated AIDS patients were examined by real-time RT-PCR, flow cytometry, and confocal microscopy. DNGR-1 expression was observed in both lymphoid and non-lymphoid tissues including gut-associated lymphoid tissues (GALT) of rhesus macaques. DNGR-1 mRNA levels were significantly reduced in the blood while significantly elevated in the GALT of SHIV/SIV-infected rhesus macaques. DNGR-1 transcription levels were also significantly reduced in the blood of ART-treated AIDS patients irrespective of viral status. White blood cells with exposed DNGR-1 ligands were significantly increased in ART-treated AIDS patients, while significantly decreased in SIV-infected rhesus macaques. These data indicate that DNGR-1 expression, and by extension, the function of cross-presentation of antigens associated with dead/damaged cells might be compromised in HIV/SIV infection, which might play a role in HIV/AIDS pathogenesis and should be taken into consideration in therapeutic AIDS vaccine development.

Molecular cloning and characterization of DNGR-1 in rhesus macaques

DC, NK lectin group receptor-1 (DNGR-1), also known as C-type lectin domain family 9 member A (CLEC9A), is a promising target for immunological therapeutics and vaccination against tumors and viruses. However, little is known about its property in rhesus macaques. In this study, we cloned rhesus macaque DNGR-1 cDNA, and found that its coding region could encode a 241-amino acid polypeptide with 91.7% sequence identity and similar antigenicity to that of humans. Both free and cell surface rhesus macaque DNGR-1 expressed in vitro could bind to apoptotic/dead cells induced by serum deprivation or freeze-thaw, and to pyroptotic cells stimulated with PMA and LPS. We also demonstrated that rhesus macaque DNGR-1 mRNA was present in all the examined tissues, with the highest in lymph nodes, spleen, blood, and thymus. The expression of DNGR-1 that is highly similar to that of humans warranted the usefulness of rhesus macaques in testing human therapeutics and vaccines targeting DNGR-1, especially those for HIV/AIDS.

CD141⁺ myeloid dendritic cells are enriched in healthy human liver

BACKGROUND & AIMS

Extensive populations of liver immune cells detect and respond to homeostatic perturbation caused by damage, infection or malignancy. Dendritic cells (DCs) are central to these activities, governing the balance between tolerance and immunity. Most of our knowledge about human liver DCs is derived from studies on peritumoral tissue. Little is known about the phenotype and function of DCs, in particular the recently described CD141(+) subset, in healthy human liver and how this profile is altered in liver disease.

METHODS

During liver transplantation, healthy donor and diseased explant livers were perfused and hepatic mononuclear cells isolated. Dendritic cell subset frequency and phenotype were characterised in liver perfusates by flow cytometry and the function of CD141(+) DCs was evaluated by mixed lymphocyte reactions (MLRs) and measuring cytokine secretion.

RESULTS

Almost one third of liver CD11c(+) myeloid DCs (mDCs) expressed CD141 compared to <5% of circulating mDCs. Hepatic CD141(+) DCs demonstrated pro-inflammatory function in allogeneic MLRs, inducing T cell production of interferon gamma (IFN-γ) and interleukin (IL)-17. While CD123(+) plasmacytoid DCs (pDCs) and CD1c(+) mDCs were expanded in diseased liver perfusates, CD141(+) DCs were significantly depleted. Despite their depletion, CD141(+) DCs from explant livers produced markedly increased poly(I:C)-induced IFN lambda (IFN-λ) compared with donor DCs.

CONCLUSIONS

Accumulation of CD141(+) DCs in healthy liver, which are significantly depleted in liver disease, suggests differential involvement of mDC subsets in liver immunity.