Publications by authors named "Christiane Ruedl"

52 Publications

Fate mapping analysis reveals a novel murine dermal migratory Langerhans-like cell population.

Elife 2021 Mar 26;10. Epub 2021 Mar 26.

School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.

Dendritic cells residing in the skin represent a large family of antigen presenting cells, ranging from long-lived Langerhans cells (LC) in the epidermis to various distinct classical dendritic cell subsets in the dermis. Through genetic fate mapping analysis and single cell RNA sequencing we have identified a novel separate population of LC-independent CD207CD326 LC cells in the dermis that homed at a slow rate to the LNs. These LC cells are long-lived and radioresistant but, unlike LCs, they are gradually replenished by bone-marrow-derived precursors under steady state. LC cells together with cDC1s are the main migratory CD207CD326 cell fractions present in the LN and not, as currently assumed, LCs, which are barely detectable, if at all. Cutaneous tolerance to haptens depends on LC cells, whereas LCs suppress effector CD8 T cell functions and inflammation locally in the skin during contact hypersensitivity. These findings bring new insights into the dynamism of cutaneous dendritic cells and their function opening novel avenues in the development of treatments to cure inflammatory skin disorders.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.7554/eLife.65412DOI Listing
March 2021

Renal CD169 resident macrophages are crucial for protection against acute systemic candidiasis.

Life Sci Alliance 2021 05 19;4(5). Epub 2021 Feb 19.

School of Biological Sciences, Nanyang Technological University, Singapore, Singapore

Disseminated candidiasis remains as the most common hospital-acquired bloodstream fungal infection with up to 40% mortality rate despite the advancement of medical and hygienic practices. While it is well established that this infection heavily relies on the innate immune response for host survival, much less is known for the protective role elicited by the tissue-resident macrophage (TRM) subsets in the kidney, the prime organ for persistence. Here, we describe a unique CD169 TRM subset that controls growth and inflammation during acute systemic candidiasis. Their absence causes severe fungal-mediated renal pathology. CD169 TRMs, without being actively involved in direct fungal clearance, increase host resistance by promoting IFN-γ release and neutrophil ROS activity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.26508/lsa.202000890DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7918719PMC
May 2021

Group 3 Innate Lymphoid Cells Program a Distinct Subset of IL-22BP-Producing Dendritic Cells Demarcating Solitary Intestinal Lymphoid Tissues.

Immunity 2020 11;53(5):1015-1032.e8

Laboratory of Innate Immunity, Department of Microbiology, Infectious Diseases and Immunology, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, Hindenburgdamm 30, 12203 Berlin, Germany; Berlin Institute of Health (BIH), Anna-Louisa-Karsch Strasse 2, 10117 Berlin, Germany; Mucosal and Developmental Immunology, Deutsches Rheuma-Forschungszentrum (DRFZ), an institute of the Leibniz Association, 10117 Berlin, Germany. Electronic address:

Solitary intestinal lymphoid tissues such as cryptopatches (CPs) and isolated lymphoid follicles (ILFs) constitute steady-state activation hubs containing group 3 innate lymphoid cells (ILC3) that continuously produce interleukin (IL)-22. The outer surface of CPs and ILFs is demarcated by a poorly characterized population of CD11c cells. Using genome-wide single-cell transcriptional profiling of intestinal mononuclear phagocytes and multidimensional flow cytometry, we found that CP- and ILF-associated CD11c cells were a transcriptionally distinct subset of intestinal cDCs, which we term CIA-DCs. CIA-DCs required programming by CP- and ILF-resident CCR6 ILC3 via lymphotoxin-β receptor signaling in cDCs. CIA-DCs differentially expressed genes associated with immunoregulation and were the major cellular source of IL-22 binding protein (IL-22BP) at steady state. Mice lacking CIA-DC-derived IL-22BP exhibited diminished expression of epithelial lipid transporters, reduced lipid resorption, and changes in body fat homeostasis. Our findings provide insight into the design principles of an immunoregulatory checkpoint controlling nutrient absorption.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.immuni.2020.10.012DOI Listing
November 2020

A Multifunctional Role of Leucine-Rich α-2-Glycoprotein 1 in Cutaneous Wound Healing Under Normal and Diabetic Conditions.

Diabetes 2020 11 4;69(11):2467-2480. Epub 2020 Sep 4.

Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore

Delayed wound healing is commonly associated with diabetes. It may lead to amputation and death if not treated in a timely fashion. Limited treatments are available partially due to the poor understanding of the complex disease pathophysiology. Here, we investigated the role of leucine-rich α-2-glycoprotein 1 (LRG1) in normal and diabetic wound healing. First, our data showed that LRG1 was significantly increased at the inflammation stage of murine wound healing, and bone marrow-derived cells served as a major source of LRG1. LRG1 deletion causes impaired immune cell infiltration, reepithelialization, and angiogenesis. As a consequence, there is a significant delay in wound closure. On the other hand, LRG1 was markedly induced in diabetic wounds in both humans and mice. LRG1-deficient mice were resistant to diabetes-induced delay in wound repair. We further demonstrated that this could be explained by the mitigation of increased neutrophil extracellular traps (NETs) in diabetic wounds. Mechanistically, LRG1 mediates NETosis in an Akt-dependent manner through TGFβ type I receptor kinase ALK5. Taken together, our studies demonstrated that LRG1 derived from bone marrow cells is required for normal wound healing, revealing a physiological role for this glycoprotein, but that excess LRG1 expression in diabetes is pathogenic and contributes to chronic wound formation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2337/db20-0585DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7576570PMC
November 2020

Talin1 controls dendritic cell activation by regulating TLR complex assembly and signaling.

J Exp Med 2020 08;217(8)

Laboratory of Molecular Immunology & Cell Signalling, School of Biological Sciences, College of Science, Nanyang Technological University, Singapore, Republic of Singapore.

Talin critically controls integrin-dependent cell migration, but its regulatory role in skin dendritic cells (DCs) during inflammatory responses has not been investigated. Here, we show that talin1 regulates not only integrin-dependent Langerhans cell (LC) migration, but also MyD88-dependent Toll-like receptor (TLR)-stimulated DC activation. Talin1-deficient LCs failed to exit the epidermis, resulting in reduced LC migration to skin-draining lymph nodes (sdLNs) and defective skin tolerance induction, while talin1-deficient dermal DCs unexpectedly accumulated in the dermis despite their actomyosin-dependent migratory capabilities. Furthermore, talin1-deficient DCs exhibited compromised chemotaxis, NFκB activation, and proinflammatory cytokine production. Mechanistically, talin1 was required for the formation of preassembled TLR complexes in DCs at steady state via direct interaction with MyD88 and PIP5K. Local production of PIP2 by PIP5K then recruited TIRAP to the preassembled complexes, which were required for TLR signalosome assembly during DC activation. Thus, talin1 regulates MyD88-dependent TLR signaling pathways in DCs through a novel mechanism with implications for antimicrobial and inflammatory immune responses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1084/jem.20191810DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7398162PMC
August 2020

Obesity retunes turnover kinetics of tissue-resident macrophages in fat.

J Leukoc Biol 2020 05 17;107(5):773-782. Epub 2020 Jan 17.

Nanyang Technological University, School of Biological Sciences, Singapore.

Adipose tissue-resident F4/80 macrophages (ATMs) are the main leukocyte population found in the visceral adipose tissue (VAT). These macrophages comprise several phenotypically distinct subpopulations that rapidly shift in abundance during obesity-induced tissue remodeling. Here we used a fate-mapping approach in mouse models to determine the developmental origins and the differential turnover kinetics of ATMs in lean and obese adipose tissue. We found that in lean, murine VAT the majority of ATMs express T cell immunoglobulin and mucin domain containing 4 receptor (Tim-4), lack the expression of CCR2 and can be further subdivided based on their expression of MHC class II and CD11c. We showed that both embryonic-derived Tim-4 MHCII and Tim-4 MHCII ATM subsets are long-lived and only slowly replenished by monocytes over time. Only a minor Tim-4 MHCII CD11c ATM fraction expresses CCR2 and is short-lived. In response to high-fat induced VAT remodeling, the majority of Tim-4 MHCII ATMs maintain their fetal identity as they are moderately displaced by monocytes. Conversely, Tim-4 MHCII ATMs are quickly replaced in a CCR2-dependent manner by bone marrow-derived Tim-4 MHCII ATMs that have significantly higher turnover rates than those in lean mice. In addition, during high-fat diet, the subpopulation of CD11c macrophages invade the VAT with the fastest turnover kinetics of all three ATM subpopulations. Our results suggest that ATM subpopulation frequency is controlled by the VAT microenvironment and that obesity-induced tissue remodeling renders some of the ATM niches accessible and available for rapid monocyte replenishment. Specialized monocyte-derived macrophages, which are rapidly recruited may be contributing to control the excess of adipocyte-released lipids produced during obesity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/JLB.1MA1219-275RDOI Listing
May 2020

Islet macrophages are associated with islet vascular remodeling and compensatory hyperinsulinemia during diabetes.

Am J Physiol Endocrinol Metab 2019 12 1;317(6):E1108-E1120. Epub 2019 Oct 1.

Lee Kong Chian School of Medicine, Nanyang Technological University Singapore, Singapore.

β-Cells respond to peripheral insulin resistance by first increasing circulating insulin during diabetes. Islet remodeling supports this compensation, but its drivers remain poorly understood. Infiltrating macrophages have been implicated in late-stage type 2 diabetes, but relatively little is known on islet resident macrophages, especially during compensatory hyperinsulinemia. We hypothesized that islet resident macrophages would contribute to islet vascular remodeling and hyperinsulinemia during diabetes, the failure of which results in a rapid progression to frank diabetes. We used chemical (clodronate), genetics (CD169-diphtheria toxin receptor mice), or antibody-mediated (colony-stimulating factor 1 receptor α) macrophage ablation methods in diabetic (db/db) and diet-induced models of compensatory hyperinsulinemia to investigate the role of macrophages in islet remodeling. We transplanted islets devoid of macrophages into naïve diabetic mice and assessed the impact on islet vascularization. With the use of the above methods, we showed that macrophage depletion significantly and consistently compromised islet remodeling in terms of size, vascular density, and insulin secretion capacity. Depletion of islet macrophages reduced VEGF-A secretion in both human and mouse islets ex vivo, and this functionally translated to delayed revascularization upon transplantation in vivo. We revealed that islet resident macrophages were associated with islet remodeling and increased insulin secretion during diabetes. This suggests utility in harnessing islet macrophages during this phase to promote islet vascularization, remodeling, and insulin secretion.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpendo.00248.2019DOI Listing
December 2019

Targeting Mutated Plus Germline Epitopes Confers Pre-clinical Efficacy of an Instantly Formulated Cancer Nano-Vaccine.

Front Immunol 2019 15;10:1015. Epub 2019 May 15.

Nuffield Department of Medicine, Jenner Institute, University of Oxford, Oxford, United Kingdom.

Personalized cancer vaccines hold promises for future cancer therapy. Targeting neoantigens is perceived as more beneficial compared to germline, non-mutated antigens. However, it is a practical challenge to identify and vaccinate patients with neoantigens. Here we asked whether two neoantigens are sufficient, and whether the addition of germline antigens would enhance the therapeutic efficacy. We developed and used a personalized cancer nano-vaccine platform based on virus-like particles loaded with toll-like receptor ligands. We generated three sets of multi-target vaccines (MTV) to immunize against the aggressive B16F10 murine melanoma: one set based on germline epitopes (GL-MTV) identified by immunopeptidomics, another set based on mutated epitopes (Mutated-MTV) predicted by whole exome sequencing and a last set combines both germline and mutated epitopes (Mix-MTV). Our results demonstrate that both germline and mutated epitopes induced protection but the best therapeutic effect was achieved with the combination of both. Our platform is based on Cu-free click chemistry used for peptide-VLP coupling, thus enabling bedside production of a personalized cancer vaccine, ready for clinical translation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fimmu.2019.01015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6532571PMC
September 2020

TCR Affinity Biases Th Cell Differentiation by Regulating CD25, Eef1e1, and Gbp2.

J Immunol 2019 05 11;202(9):2535-2545. Epub 2019 Mar 11.

Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN 55455;

Naive CD4 T lymphocytes differentiate into various Th cell subsets following TCR binding to microbial peptide:MHC class II (p:MHCII) complexes on dendritic cells (DCs). The affinity of the TCR interaction with p:MHCII plays a role in Th differentiation by mechanisms that are not completely understood. We found that low-affinity TCRs biased mouse naive T cells to become T follicular helper (Tfh) cells, whereas higher-affinity TCRs promoted the formation of Th1 or Th17 cells. We explored the basis for this phenomenon by focusing on IL-2R signaling, which is known to promote Th1 and suppress Tfh cell differentiation. SIRP⍺ DCs produce abundant p:MHCII complexes and consume IL-2, whereas XCR1 DCs weakly produce p:MHCII but do not consume IL-2. We found no evidence, however, of preferential interactions between Th1 cell-prone, high-affinity T cells and XCR1 DCs or Tfh cell-prone, low-affinity T cells and SIRP⍺ DCs postinfection with bacteria expressing the peptide of interest. Rather, high-affinity T cells sustained IL-2R expression longer and expressed two novel Th cell differentiation regulators, Eef1e1 and Gbp2, to a higher level than low-affinity T cells. These results suggest that TCR affinity does not influence Th cell differentiation by biasing T cell interactions with IL-2-consuming DCs, but instead, directly regulates genes in naive T cells that control the differentiation process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.1801609DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6478541PMC
May 2019

Type 1 Conventional CD103 Dendritic Cells Control Effector CD8 T Cell Migration, Survival, and Memory Responses During Influenza Infection.

Front Immunol 2018 21;9:3043. Epub 2018 Dec 21.

School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.

Type 1 conventional CD103 dendritic cells (cDC1) contribute significantly to the cytotoxic T lymphocyte (CTL) response during influenza virus infection; however, the mechanisms by which cDC1s promote CTL recruitment and viral clearance are unclear. We demonstrate that cDC1 ablation leads to a deficient influenza-specific primary CD8 T cell response alongside severe pulmonary inflammation, intensifying susceptibility to infection. The diminished pulmonary CTL population is not only a consequence of reduced priming in the lymph node (LN), but also of dysregulated CD8 T cell egression from the LN and reduced CD8 T cell viability in the lungs. cDC1s promote S1PR expression on CTLs, a key chemokine receptor facilitating CTL LN egress, and express high levels of the T cell survival cytokine, IL-15, to support CTL viability at the site of infection. Moreover, cDC1 ablation leads to severe impairment of CD8 T cell memory recall and cross-reactive protection, suggesting that cDC1 are not only involved in primary T cell activation, but also in supporting the development of effective memory CD8 T cell precursors. Our findings demonstrate a previously unappreciated and multifaceted role of CD103 DCs in controlling pulmonary T cell-mediated immune responses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fimmu.2018.03043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6308161PMC
October 2019

Organ-Specific Fate, Recruitment, and Refilling Dynamics of Tissue-Resident Macrophages during Blood-Stage Malaria.

Cell Rep 2018 12;25(11):3099-3109.e3

Nanyang Technological University, School of Biological Sciences, 60 Nanyang Drive, Singapore 637551, Singapore. Electronic address:

Inflammation-induced disappearance of tissue-resident macrophages represents a key pathogen defense mechanism. Using a model of systemic blood-stage malaria, we studied the dynamics of tissue-resident macrophages in multiple organs to determine how they are depleted and refilled during the course of disease. We show that Plasmodium infection results in a transient loss of embryonically established resident macrophages prior to the parasitemia peak. Fate-mapping analysis reveals that inflammatory monocytes contribute to the repopulation of the emptied niches of splenic red pulp macrophages and hepatic Kupffer cells, while lung alveolar macrophages refill their niche predominantly through self-renewal. Interestingly, the local microenvironment of the spleen and liver can "imprint" the molecular characteristics of fetal-derived macrophages on newly differentiated bone marrow-derived immigrants with remarkably similar gene expression profiles and turnover kinetics. Thus, the mononuclear phagocytic system has developed distinct but effective tissue-specific strategies to replenish emptied niches to guarantee the functional integrity of the system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.celrep.2018.11.059DOI Listing
December 2018

DTR-mediated conditional cell ablation-Progress and challenges.

Eur J Immunol 2018 07;48(7):1114-1119

Department of Immunology, Weizmann Institute of Science, Rehovot, Israel.

Cell ablation is a valuable complement to mutagenesis for experimentally defining specific cell functions in physiology and pathophysiology in small animal models. One of the most popular ablation strategies involves transgenic expression of a primate diphtheria toxin receptor (DTR) on murine cells that are otherwise resistant to the bacterial exotoxin. The efforts of many laboratories using the DTR approach over the years have yielded numerous valuable insights into specific cell functions. Here, we will discuss the technical aspects of the DTR approach, including the strengths, pitfalls, and future strategies to overcome the shortcomings, highlighting a recent paper published in the European Journal of Immunology [El Hachem et al. Eur. J. Immunol. 2018 https://doi.org/10.1002/eji.201747351]. A particular focus will be given to the application of DTR approach to decipher in vivo functions of the murine myeloid cell compartment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/eji.201847527DOI Listing
July 2018

Clec9A Dendritic Cells Are Not Essential for Antitumor CD8 T Cell Responses Induced by Poly I:C Immunotherapy.

J Immunol 2018 04 5;200(8):2978-2986. Epub 2018 Mar 5.

Malaghan Institute of Medical Research, Wellington 6021, New Zealand;

In the steady state, tumors harbor several populations of dendritic cells (DCs) and myeloid cells that are key regulators of the intratumoral immune environment. Among these cells, migratory CD103 cross-presenting DCs are thought to be critical for tumor-specific CTL responses and tumor resistance. However, it is unclear whether this prominent role also extends to immunotherapy. We used a murine orthotopic mammary tumor model, as well as Clec9A-diphtheria toxin receptor mice that can be depleted of the specialized cross-presenting CD8α and CD103 DC1 subsets, to investigate the role of these DCs in immunotherapy. Treatment with monosodium urate crystals and mycobacteria at the tumor site delayed tumor growth and required DC1s for efficacy. In contrast, treatment with poly I:C was equally effective regardless of DC1 depletion. Neither treatment affected myeloid-derived suppressor cell numbers in the spleen or tumor. Similar experiments using subcutaneous B16 melanoma tumors in BATF3-knockout mice confirmed that CD103 DCs were not necessary for successful poly I:C immunotherapy. Nevertheless, adaptive immune responses were essential for the response to poly I:C, because mice depleted of CD8 T cells or all DC subsets were unable to delay tumor growth. In vivo experiments showed that DC1 and DC2 subsets were able to take up tumor Ags, with DC2s making up the larger proportion of lymph node DCs carrying tumor material. Both DC subsets were able to cross-present OVA to OT-I T cells in vitro. Thus, immunotherapy with poly I:C enables multiple DC subsets to cross-present tumor Ag for effective antitumor immune responses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.1701593DOI Listing
April 2018

The tumour microenvironment creates a niche for the self-renewal of tumour-promoting macrophages in colon adenoma.

Nat Commun 2018 02 8;9(1):582. Epub 2018 Feb 8.

School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.

Circulating CCR2 monocytes are crucial for maintaining the adult tissue-resident F4/80MHCII macrophage pool in the intestinal lamina propria. Here we show that a subpopulation of CCR2-independent F4/80MHCII macrophages, which are the most abundant F4/80 cells in neonates, gradually decline in number in adulthood; these macrophages likely represent the fetal contribution to F4/80 cells. In colon adenomas of Apc mice, F4/80MHCII macrophages are not only preserved, but become the dominant subpopulation among tumour-resident macrophages during tumour progression. Furthermore, these pro-tumoural F4/80MHCII and F4/80MHCII macrophages can self-renew in the tumour and maintain their numbers mostly independent from bone marrow contribution. Analyses of colon adenomas indicate that CSF1 may be a key facilitator of macrophage self-renewal. In summary, the tumour microenvironment creates an isolated niche for tissue-resident macrophages that favours macrophage survival and self-renewal.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41467-018-02834-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5805689PMC
February 2018

Blocking CTLA-4 while priming with a whole cell vaccine reshapes the oligoclonal T cell infiltrate and eradicates tumors in an orthotopic glioma model.

Oncoimmunology 2017;7(1):e1376154. Epub 2017 Sep 27.

Malaghan Institute of Medical Research, Wellington, New Zealand.

Vaccine-mediated cancer treatment is unlikely to induce long-term survival unless suppressive mechanisms are overcome. Given the success of antibody-mediated immune checkpoint blockade in relieving regulation of endogenous anti-tumor T cell responses in tumor-burdened hosts, we investigated whether checkpoint blockade could improve the efficacy of responses induced with a whole tumor-cell vaccine. We show that administration of a single dose of blocking antibody was sufficient to significantly enhance antitumor activity of the vaccine, inducing complete radiological regression of established intracranial tumors. The antibody or vaccine alone were ineffective in this setting. The antibody had to be administered before, or close to, vaccine administration, suggesting CTLA-4 blockade had an impact on early priming events. The combined treatment resulted in enhanced trapping of leukocytes in the lymphoid tissues, including T cells that had undergone significant proliferation. There were no obvious changes in the stimulatory function of antigen-presenting cells or the number and function of regulatory T cells, suggesting T cells were the targets of the checkpoint blockade. While tumors regressing under combined treatment were highly infiltrated with a variety of leukocytes, tumor eradication was dependent on CD4 T cells. Analysis of the TCR repertoire showed that the addition of anti-CTLA-4 at priming reshaped the repertoire of tumor infiltrating T cells. In particular, the oligoclonal populations became greater in magnitude and more diverse in specificity. Using anti-CTLA-4 in a restricted way to promote the priming phase of an anti-cancer vaccine may offer a useful way of harnessing clinical benefit from this powerful agent.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/2162402X.2017.1376154DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5739554PMC
September 2017

Toll-Like Receptor 4, but Not Neutrophil Extracellular Traps, Promote IFN Type I Expression to Enhance Th2 Responses to .

Front Immunol 2017 16;8:1575. Epub 2017 Nov 16.

Malaghan Institute of Medical Research, Wellington, New Zealand.

The induction of Th2 responses is thought to be multifactorial, and emerge from specific pathways distinct from those associated with antagonistic antibacterial or antiviral Th1 responses. Here, we show that the recognition of non-viable (Nb) in the skin induces a strong recruitment of monocytes and neutrophils and the release of neutrophil extracellular traps (NETs). Nb also activates toll-like receptor 4 (TLR4) signaling with expression of transcripts in the skin and the development of an IFN type I signature on helminth antigen-bearing dendritic cells in draining lymph nodes. Co-injection of Nb together with about 10,000 Gram-negative bacteria amplified this TLR4-dependent but NET-independent IFN type I response and enhanced the development of Th2 responses. Thus, a limited activation of antibacterial signaling pathways is able to boost antihelminthic responses, suggesting a role for bacterial sensing in the optimal induction of Th2 immunity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fimmu.2017.01575DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5696323PMC
November 2017

A Discrete Subset of Monocyte-Derived Cells among Typical Conventional Type 2 Dendritic Cells Can Efficiently Cross-Present.

Cell Rep 2017 Oct;21(5):1203-1214

Nanyang Technological University, School of Biological Sciences, 60 Nanyang Drive, Singapore 637551, Singapore. Electronic address:

Dendritic cells (DCs) and macrophages (Mϕs) share close developmental pathways and functional features, leading to blurring of the boundaries between these two cell lineages. However, a deeper understanding of DC and Mϕ ontogeny and more refined phenotypic and functional characterizations have helped to delineate pre-DC-derived conventional DCs (cDCs), including cDC1s and cDC2s, from monocyte-derived Mϕs. Here, we further refine DC/Mϕ cell classification and report that classically defined cDC2s contain a discrete population of monocyte-derived migratory antigen-presenting cells with Mϕ phenotype but functional DC features, including cross-presentation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.celrep.2017.10.024DOI Listing
October 2017

Long-Lived Innate IL-17-Producing γ/δ T Cells Modulate Antimicrobial Epithelial Host Defense in the Colon.

J Immunol 2017 11 13;199(10):3691-3699. Epub 2017 Oct 13.

School of Biological Sciences, Nanyang Technological University, Singapore 637551, Singapore

Intestinal IL-17-producing cells, including Th17, γ/δ T, and innate lymphoid cells, are differentially distributed along the gastrointestinal tract. In this study, we show that the gut IL-17-producing γ/δ T (γ/δ T17) cells develop before birth and persist in the tissue as long-lived cells with minimal turnover. Most colon γ/δ T17 cells express, together with Vγ4 and CCR6, the scavenger receptor 2 and are mainly restricted to innate lymphoid follicles in the colon. Colon γ/δ T cells in mice that lack conventional dendritic cells 2 produced increased amounts of IL-17 with concomitant heightened epithelial antimicrobial response, such as the C-type lectins Reg3γ and Reg3β. In the absence of γ/δ T cells or after IL-17 neutralization, this epithelial response was dramatically reduced, underlining the protective role of this unique subpopulation of innate γ/δ T17 cells in the colonic mucosa.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.1701053DOI Listing
November 2017

Role and contribution of pulmonary CD103 dendritic cells in the adaptive immune response to Mycobacterium tuberculosis.

Tuberculosis (Edinb) 2017 01 8;102:34-46. Epub 2016 Dec 8.

Department of Microbiology, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore; Immunology Programme, Life Sciences Institute, NUS, Singapore. Electronic address:

Despite international control programmes, the global burden of tuberculosis remains enormous. Efforts to discover novel drugs have largely focused on targeting the bacterium directly. Alternatively, manipulating the host immune response may represent a valuable approach to enhance immunological clearance of the bacilli, but necessitates a deeper understanding of the immune mechanisms associated with protection against Mycobacterium tuberculosis infection. Here, we examined the various dendritic cells (DC) subsets present in the lung and draining lymph nodes (LN) from mice intra-tracheally infected with M. tuberculosis. We showed that although limited in number, pulmonary CD103 DCs appeared to be involved in the initial transport of mycobacteria to the draining mediastinal LN and subsequent activation of T cells. Using CLEC9A-DTR transgenic mice enabling the inducible depletion of CD103 DCs, we established that this DC subset contributes to the control of mycobacterial burden and plays a role in the early activation of T cells, in particular CD8 T cells. Our findings thus support a previously unidentified role for pulmonary CD103 DCs in the rapid mobilization of mycobacteria from the lungs to the draining LN soon after exposure to M. tuberculosis, which is a critical step for the development of the host adaptive immune response.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.tube.2016.12.003DOI Listing
January 2017

Tissue-Resident CD169(+) Macrophages Form a Crucial Front Line against Plasmodium Infection.

Cell Rep 2016 08 28;16(6):1749-1761. Epub 2016 Jul 28.

Nanyang Technological University, School of Biological Sciences, 60 Nanyang Drive, Singapore 637551, Singapore. Electronic address:

Tissue macrophages exhibit diverse functions, ranging from the maintenance of tissue homeostasis, including clearance of senescent erythrocytes and cell debris, to modulation of inflammation and immunity. Their contribution to the control of blood-stage malaria remains unclear. Here, we show that in the absence of tissue-resident CD169(+) macrophages, Plasmodium berghei ANKA (PbA) infection results in significantly increased parasite sequestration, leading to vascular occlusion and leakage and augmented tissue deposition of the malarial pigment hemozoin. This leads to widespread tissue damage culminating in multiple organ inflammation. Thus, the capacity of CD169(+) macrophages to contain the parasite burden and its sequestration into different tissues and to limit infection-induced inflammation is crucial to mitigating Plasmodium infection and pathogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.celrep.2016.07.010DOI Listing
August 2016

Analysis of Dendritic Cell Function Using Clec9A-DTR Transgenic Mice.

Methods Mol Biol 2016 ;1423:275-89

School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore, 637551, Singapore.

The Clec9A-diphtheria toxin receptor (DTR) transgenic mouse strain provides a robust animal model to study the function of lymphoid organ-resident CD8(+) dendritic cells (DCs) and nonlymphoid organ-specific CD103(+) DCs in infectioous diseases and inflammation. Here we describe some basic protocols for CD8(+)/CD103(+) DC isolation, for their in vivo depletion, and for their characterization by multi-color flow cytometry analysis. As an example for in vivo functional characterization of this DC subset, we present here the experimental cerebral malaria model. Furthermore, we illustrate advantages and pitfalls of the Clec9A-DTR system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/978-1-4939-3606-9_20DOI Listing
December 2017

Fetal HSCs versus EMP2s.

Immunity 2015 Dec;43(6):1025

School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore. Electronic address:

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.immuni.2015.11.023DOI Listing
December 2015

Most Tissue-Resident Macrophages Except Microglia Are Derived from Fetal Hematopoietic Stem Cells.

Immunity 2015 Aug;43(2):382-93

School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore. Electronic address:

Macrophages are one of the most diverse cell populations in terms of their anatomical location and functional specialization during both homeostasis and disease. Although it has been shown in different fate mapping models that some macrophages present in adult tissues are already established during fetal development, their exact origins are still under debate. In the current study, we developed a fate mapping strain, based on the Kit locus, which allowed us to readdress "the origins" question. Different types of macrophages from various adult tissues were traced to their fetal or adult sources by inducing labeling in precursors at several time points either during fetal development or in adult mice. We show that all adult macrophages, resident or infiltrating, are progenies of classical hematopoietic stem cells (HSC) with the exception of microglia and, partially epidermal Langerhans cells, which are yolk sac (YS)-derived.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.immuni.2015.07.016DOI Listing
August 2015

Activated NKT Cells Can Condition Different Splenic Dendritic Cell Subsets To Respond More Effectively to TLR Engagement and Enhance Cross-Priming.

J Immunol 2015 Aug 15;195(3):821-31. Epub 2015 Jun 15.

Malaghan Institute of Medical Research, Wellington 6242, New Zealand; School of Biological Sciences, Victoria University of Wellington, Wellington 6012, New Zealand;

The function of dendritic cells (DCs) can be modulated through multiple signals, including recognition of pathogen-associated molecular patterns, as well as signals provided by rapidly activated leukocytes in the local environment, such as innate-like T cells. In this article, we addressed the possibility that the roles of different murine DC subsets in cross-priming CD8(+) T cells can change with the nature and timing of activatory stimuli. We show that CD8α(+) DCs play a critical role in cross-priming CD8(+) T cell responses to circulating proteins that enter the spleen in close temporal association with ligands for TLRs and/or compounds that activate NKT cells. However, if NKT cells are activated first, then CD8α(-) DCs become conditioned to respond more vigorously to TLR ligation, and if triggered directly, these cells can also contribute to priming of CD8(+) T cell responses. In fact, the initial activation of NKT cells can condition multiple DC subsets to respond more effectively to TLR ligation, with plasmacytoid DCs making more IFN-α and both CD8α(+) and CD8α(-) DCs manufacturing more IL-12. These results suggest that different DC subsets can contribute to T cell priming if provided appropriately phased activatory stimuli, an observation that could be factored into the design of more effective vaccines.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.1401751DOI Listing
August 2015

Genome-wide analysis in Plasmodium falciparum reveals early and late phases of RNA polymerase II occupancy during the infectious cycle.

BMC Genomics 2014 Nov 6;15:959. Epub 2014 Nov 6.

School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.

Background: Over the course of its intraerythrocytic developmental cycle (IDC), the malaria parasite Plasmodium falciparum tightly orchestrates the rise and fall of transcript levels for hundreds of genes. Considerable debate has focused on the relative importance of transcriptional versus post-transcriptional processes in the regulation of transcript levels. Enzymatically active forms of RNAPII in other organisms have been associated with phosphorylation on the serines at positions 2 and 5 of the heptad repeats within the C-terminal domain (CTD) of RNAPII. We reasoned that insight into the contribution of transcriptional mechanisms to gene expression in P. falciparum could be obtained by comparing the presence of enzymatically active forms of RNAPII at multiple genes with the abundance of their associated transcripts.

Results: We exploited the phosphorylation state of the CTD to detect enzymatically active forms of RNAPII at most P. falciparum genes across the IDC. We raised highly specific monoclonal antibodies against three forms of the parasite CTD, namely unphosphorylated, Ser5-P and Ser2/5-P, and used these in ChIP-on-chip type experiments to map the genome-wide occupancy of RNAPII. Our data reveal that the IDC is divided into early and late phases of RNAPII occupancy evident from simple bi-phasic RNAPII binding profiles. By comparison to mRNA abundance, we identified sub-sets of genes with high occupancy by enzymatically active forms of RNAPII and relatively low transcript levels and vice versa. We further show that the presence of active and repressive histone modifications correlates with RNAPII occupancy over the IDC.

Conclusions: The simple early/late occupancy by RNAPII cannot account for the complex dynamics of mRNA accumulation over the IDC, suggesting a major role for mechanisms acting downstream of RNAPII occupancy in the control of gene expression in this parasite.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/1471-2164-15-959DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4232647PMC
November 2014

High-dimensional analysis of the murine myeloid cell system.

Nat Immunol 2014 Dec 12;15(12):1181-9. Epub 2014 Oct 12.

Agency for Science, Technology and Research (A*STAR), Singapore Immunology Network (SIgN), Singapore.

Advances in cell-fate mapping have revealed the complexity in phenotype, ontogeny and tissue distribution of the mammalian myeloid system. To capture this phenotypic diversity, we developed a 38-antibody panel for mass cytometry and used dimensionality reduction with machine learning-aided cluster analysis to build a composite of murine (mouse) myeloid cells in the steady state across lymphoid and nonlymphoid tissues. In addition to identifying all previously described myeloid populations, higher-order analysis allowed objective delineation of otherwise ambiguous subsets, including monocyte-macrophage intermediates and an array of granulocyte variants. Using mice that cannot sense granulocyte macrophage-colony stimulating factor GM-CSF (Csf2rb(-/-)), which have discrete alterations in myeloid development, we confirmed differences in barrier tissue dendritic cells, lung macrophages and eosinophils. The methodology further identified variations in the monocyte and innate lymphoid cell compartment that were unexpected, which confirmed that this approach is a powerful tool for unambiguous and unbiased characterization of the myeloid system.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/ni.3006DOI Listing
December 2014

Type I IFN signaling in CD8- DCs impairs Th1-dependent malaria immunity.

J Clin Invest 2014 Jun 1;124(6):2483-96. Epub 2014 May 1.

Many pathogens, including viruses, bacteria, and protozoan parasites, suppress cellular immune responses through activation of type I IFN signaling. Recent evidence suggests that immune suppression and susceptibility to the malaria parasite, Plasmodium, is mediated by type I IFN; however, it is unclear how type I IFN suppresses immunity to blood-stage Plasmodium parasites. During experimental severe malaria, CD4+ Th cell responses are suppressed, and conventional DC (cDC) function is curtailed through unknown mechanisms. Here, we tested the hypothesis that type I IFN signaling directly impairs cDC function during Plasmodium infection in mice. Using cDC-specific IFNAR1-deficient mice, and mixed BM chimeras, we found that type I IFN signaling directly affects cDC function, limiting the ability of cDCs to prime IFN-γ-producing Th1 cells. Although type I IFN signaling modulated all subsets of splenic cDCs, CD8- cDCs were especially susceptible, exhibiting reduced phagocytic and Th1-promoting properties in response to type I IFNs. Additionally, rapid and systemic IFN-α production in response to Plasmodium infection required type I IFN signaling in cDCs themselves, revealing their contribution to a feed-forward cytokine-signaling loop. Together, these data suggest abrogation of type I IFN signaling in CD8- splenic cDCs as an approach for enhancing Th1 responses against Plasmodium and other type I IFN-inducing pathogens.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1172/JCI70698DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4038565PMC
June 2014

Transient ablation of alveolar macrophages leads to massive pathology of influenza infection without affecting cellular adaptive immunity.

Eur J Immunol 2014 Jul 29;44(7):2003-12. Epub 2014 Apr 29.

School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.

Alveolar macrophages (AMs), localized at the pulmonary air-tissue interface, are one of the first lines of defense that interact with inhaled airborne pathogens such as influenza viruses. By using a new CD169-DTR transgenic mouse strain we demonstrate that specific and highly controlled in vivo ablation of this myeloid cell subset leads to severe impairment of the innate, but not adaptive, immune responses and critically affects the progression of the disease. In fact, AM-ablated mice, infected with a normally sublethal dose of PR8 influenza virus, showed dramatically increased virus load in the lungs, severe airway inflammation, pulmonary edema and vascular leakage, which caused the death of the infected animals. Our data highlight the possibilities for new therapeutic strategies focusing on modulation of AMs, which may efficiently boost innate responses to influenza infections.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/eji.201344359DOI Listing
July 2014

Cell depletion in mice that express diphtheria toxin receptor under the control of SiglecH encompasses more than plasmacytoid dendritic cells.

J Immunol 2014 May 28;192(9):4409-16. Epub 2014 Mar 28.

Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110;

Plasmacytoid dendritic cells (pDC) produce IFN-I in response to viruses and are routinely identified in mice by SiglecH expression. SiglecH is a sialic acid-binding Ig-like lectin that has an immunomodulatory role during viral infections. In this study, we evaluated the impact of SiglecH deficiency on cytokine responses in the presence and absence of pDC. We found that lack of SiglecH enhanced IFN-I responses to viral infection, regardless of whether pDC were depleted. We also examined the expression pattern of SiglecH and observed that it was expressed by specialized macrophages and progenitors of classical dendritic cells and pDC. Accordingly, marginal zone macrophages and pDC precursors were eliminated in newly generated SiglecH-diphtheria toxin receptor (DTR)-transgenic (Tg) mice but not in CLEC4C-DTR-Tg mice after diphtheria toxin (DT) treatment. Using two bacterial models, we found that SiglecH-DTR-Tg mice injected with DT had altered bacterial uptake and were more susceptible to lethal Listeria monocytogenes infection than were DT-treated CLEC4C-DTR-Tg mice. Taken together, our findings suggest that lack of SiglecH may affect cytokine responses by cell types other than pDC during viral infections, perhaps by altering viral distribution or burden, and that cell depletion in SiglecH-DTR-Tg mice encompasses more than pDC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.1303135DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4194082PMC
May 2014

Cutting edge: Clec9A+ dendritic cells mediate the development of experimental cerebral malaria.

J Immunol 2012 Aug 25;189(3):1128-32. Epub 2012 Jun 25.

School of Biological Sciences, Nanyang Technological University, Singapore 637551.

Plasmodium infections trigger strong innate and acquired immune responses, which can lead to severe complications, including the most feared and often fatal cerebral malaria (CM). To begin to dissect the roles of different dendritic cell (DC) subsets in Plasmodium-induced pathology, we have generated a transgenic strain, Clec9A-diphtheria toxin receptor that allows us to ablate in vivo Clec9A(+) DCs. Specifically, we have analyzed the in vivo contribution of this DC subset in an experimental CM model using Plasmodium berghei, and we provide strong evidence that the absence of this DC subset resulted in complete resistance to experimental CM. This was accompanied with dramatic reduction of brain CD8(+) T cells, and those few cerebral CD8(+) T cells present had a less activated phenotype, unlike their wildtype counterparts that expressed IFN-γ and especially granzyme B. This almost complete absence of local cellular responses was also associated with reduced parasite load in the brain.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.4049/jimmunol.1201171DOI Listing
August 2012