Interaction Of Dendritic Cells Research Articles

An IL-17A-centric response to Epstein-Barr virus DNA mediated by dendritic Cell-T cell interactions.

Introduction: The Epstein-Barr virus has been associated with a considerable number of autoimmune diseases. We have previously demonstrated that EBV DNA enhances the production of IL-17A, a pro-inflammatory cytokine, via endosomal Toll-like receptor signalling. Methods: We used RNA-seq to analyze the transcriptional profile of mouse immune cells treated with EBV DNA. Results: We observed that EBV DNA upregulates an IL-17A-centric network of mediators. Ensemble Gene Set Enrichment Analysis (EGSEA) showed enriched expression of sets involved in inflammatory responses including IFNγ and TNF-α-associated pathways as well as proinflammatory diseases. On the other hand, while macrophages and B cells were somewhat able to induce an IL-17A response from T cells to EBV DNA, they were less potent than dendritic cells. EBV virions were also capable of eliciting the production of inflammatory mediators from dendritic cell-T cell cultures largely mirroring responses to the viral DNA. Conclusions: Given the wide prevalence of EBV in the population, our analyses reveal a network of mediators and cell types that may serve as therapeutic targets in a large proportion of people affected by autoimmune diseases.

Newcastle disease virus suppresses antigen presentation via inhibiting IL-12 expression in dendritic cells.

As a potential vectored vaccine, Newcastle disease virus (NDV) has been subject to various studies for vaccine development, while relatively little research has outlined the immunomodulatory effect of the virus in antigen presentation. To elucidate the key inhibitory factor in regulating the interaction of infected dendritic cells (DCs) and T cells, DCs were pretreated with the NDV vaccine strain LaSota as an inhibitor and stimulated with lipopolysaccharide (LPS) for further detection by enzyme-linked immunosorbent assay (ELISA), flow cytometry, immunoblotting, and quantitative real-time polymerase chain reaction (qRT-PCR). The results revealed that NDV infection resulted in the inhibition of interleukin (IL)-12p40 in DCs through a p38 mitogen-activated protein kinase (MAPK)‍-dependent manner, thus inhibiting the synthesis of IL-12p70, leading to the reduction in T cell proliferation and the secretion of interferon-γ (IFN-γ), tumor necrosis factor-α (TNF-α), and IL-6 induced by DCs. Consequently, downregulated cytokines accelerated the infection and viral transmission from DCs to T cells. Furthermore, several other strains of NDV also exhibited inhibitory activity. The current study reveals that NDV can modulate the intensity of the innate‍‒‍adaptive immune cell crosstalk critically toward viral invasion improvement, highlighting a novel mechanism of virus-induced immunosuppression and providing new perspectives on the improvement of NDV-vectored vaccine.

Neutrophil-plasmacytoid dendritic cell interaction leads to production of type I IFN in response to Mycobacterium tuberculosis.

Mycobacterium tuberculosis (Mtb) can cause a latent infection that sometimes progresses to clinically active tuberculosis (TB). Type I interferons (IFN-I) have been implicated in initiating the progression from latency to active TB, in part because IFN-I stimulated genes are the earliest genes to be upregulated in patients as they advance to active TB. Plasmacytoid dendritic cells (pDCs) are major producers of IFN-I during viral infections and in response to autoimmune-induced neutrophil extracellular traps. pDCs have also been suggested to be the major producers of IFN-I during Mtb infection of mice and nonhuman primates, but direct evidence has been lacking. Here, we found that Mtb did not stimulate isolated human pDCs to produce IFN-I, but human neutrophils infected with Mtb-activated co-cultured pDCs to do so. Mtb-infected neutrophils produced neutrophil extracellular traps, whose exposed DNA is a well-known mechanism to activate pDCs to secrete IFN-I. We conclude that pDCs contribute to the IFN-I response during Mtb infection by interacting with infected neutrophils which may then promote Mtb pathogenesis.

Tox induces T cell IL-10 production in a BATF-dependent manner.

Tox is a member of the high mobility group (HMG)-Box transcription factors and plays important roles in thymic T cell development. Outside of the thymus, however, Tox is also highly expressed by CD8 and CD4 T cells in various states of activation and in settings of cancer and autoimmune disease. In CD4 T cells, Tox has been primarily studied in T follicular helper (TFH) cells where it, along with Tox2, promotes TFH differentiation by regulating key TFH-associated genes and suppressing CD4 cytotoxic T cell differentiation. However, the role of Tox in other T helper (Th) cell subtypes is less clear. Here, we show that Tox is expressed in several physiologically-activated Th subtypes and its ectopic expression enhances the in vitro differentiation of Th2 and T regulatory (Treg) cells. Tox overexpression in unpolarized Th cells also induced the expression of several genes involved in cell activation (Pdcd1), cellular trafficking (Ccl3, Ccl4, Xcl1) and suppressing inflammation (Il10) across multiple Th subtypes. We found that Tox binds the regulatory regions of these genes along with the transcription factors BATF, IRF4, and JunB and that Tox-induced expression of IL-10, but not PD-1, is BATF-dependent. Based on these data, we propose a model where Tox regulates Th cell chemotactic genes involved in facilitating dendritic cell-T cell interactions and aids in the resolution or prevention of inflammation through the production of IL-10.

Comparative genomics identified TLR-dependent fine tuning of the dendritic cell immune response by melatonin

Abstract Melatonin, a neuro hormone, has been shown to activate human monocytes and induce their cytotoxic properties in addition to the production of IL-1, IL-6, and TNF-α. The molecular mechanisms involved in melatonin and dendritic cell interactions are largely unknown. In this study, we performed a comprehensive RNA sequencing (RNA-seq)-based analysis of monocyte-derived human dendritic cells across different melatonin stimulations. We profiled gene expression changes among naïve DCs along with DCs generated with melatonin (MDCs) and DCs matured with melatonin (DCMs). We found that melatonin significantly promoted the morphological maturation of MDCs and increased the expression of DC-related surface markers. Furthermore, MDCs increased the general immune response by promoting the secretion of IL-12, IL-6 and IFN-γ cytokines and enhancing the proliferation of TH cells, while DCM did not. Genome-wide comparative transcriptomic profiling showed that the expression of 7417 genes was significantly upregulated, and 3325 genes were significantly downregulated in MDCs. We observed the spatiotemporal activity of TLR 2-, 4-, 6- and 8-specific genes in MDCs. Interestingly, we found that the expression of TLR 10-specific signaling genes was significantly higher in DCMs. Further in vitro validation showed that along with TLRs, the upregulation of IRAK, GRB2, CREB and TNFRSF was significantly associated with MDCs. Overall, we found that during the differentiation of dendritic cells, the presence of melatonin generates a unique population of dendritic cells with activated TLR4 signaling. DCs generated through this unique culture process may act as good candidates for immunomodulation during cancer and inflammation. Supported by grants fromDST-SERB, GOI (CRG/2019/001296)

Oral exposure to citrinin significantly exacerbates the pathophysiology of a mouse model of imiquimod-induced psoriasis via direct activation of dendritic cell.

Citrinin, a mycotoxin produced by Penicillium citrinum and Penicillium verrucosum, mainly contaminates cereals. The aim of study was to investigate the novel immunoreactive effect of citrinin using a mouse model of psoriasis. A mouse model of psoriasis was generated by topical application of 5% imiquimod in female BALB/c mice. Standard rodent diet and rice samples with 3ppm of citrinin were mixed to obtain a final citrinin concentration of 0.3ppm, and a citrinin-contaminated diet was fed to mice daily. Skin thickness, scratching behavior, and trans epidermal water loss (TEWL) were monitored continuously during the imiquimod application. Immediately after the final imiquimod application, ear skin and auricular lymph node (LN) were sampled for further analysis. Only a slight increase was observed in skin thickness in the citrinin exposure group; however, citrinin exposure significantly exacerbated hyperkeratinization and inflammatory cell infiltration in histological evaluation. TEWL, which is representative of cutaneous barrier function, was significantly increased by citrinin exposure. In terms of immune function, the number of immune cells in LN (T cells and dendritic cells) and gene expression of interleukin (IL)-17 in skin tissue were significantly increased by citrinin exposure. Direct interaction of dendritic cells (DCs) in citrinin-induced psoriasis development was further examined by proinflammatory cytokine determination in THP-1 cells and murine bone marrow derived DCs. IL-6 and/or tumor necrosis factor α were significantly increased by citrinin exposure. Taken together, our results imply that oral exposure to citrinin exacerbates the symptoms of a mouse model of psoriasis via direct activation of DCs.

Abstract PD9-03: Breast Cancer Microenvironment Change After Neoadjuvant Endocrine Treatment Breast Cancer Microenvironment Change After Neoadjuvant Endocrine Treatment

Abstract Background: Estrogen receptor positive (ER+)/HER-2 negative breast cancer (BC) is considered to be an immunologically cold tumor compared to triple negative breast cancer. Therefore, the tumor microenvironment (TME) of ER+/HER-2 negative BC is understudied. The receptor activator of nuclear factor-kB ligand (RANKL)-RANK pathway was first identified, as mediator of T and dendritic cells interaction, but it is mostly known for its role as key regulator of bone remodeling and pathophysiology of bone metastases. RANK is a member of the tumor necrosis factor receptor (TNFR) superfamily that is activated upon RANKL binding, promoting cell proliferation, survival and differentiation. The RANKL-RANK pathway also emerged as a major mediator of hormone-driven breast carcinogenesis. The aim of this study is to investigate the TME and the immune response during neoadjuvant endocrine therapy (NET) and to correlate this with the treatment response in a real life setting. Methods: Expressions of immune checkpoint receptors and immune cells were examined immunohistochemically in pre- and post- NET on a cohort of 44 ER+/HER-2 negative BC patients. They were treated with tamoxifen (N=8), an aromatase inhibitor (N=36) or a combination of an aromatase inhibitor with a PI3K inhibitor (N= 7) for a median duration of 6 months (range 1-32) months. Monoclonal antibodies for PDL-1, PD-1, TIM-3, LAG-3, CTLA-4, CD4, CD68, FOXP3, RANK and RANKL were used. All staining were done according to validated protocols and scoring was done by a pathologist specialized in breast cancer. Positivity was defined as staining > 1% on TILs. Response to NET was evaluated according to tumor size change on imaging and Ki-67 change. Results: The median age was 62.5 (44–90.3) years. Diameter of tumor size decreased with a mean of 7.818 mm (p < 0.0001) during NET and the value of Ki-67 value decreased significantly after NET (value, p< 0.0004). An increase in PD-L1 expression after NET showed a trend towards significant (p= 0.088) and RANK expression on TILs significantly decreased with a median of 30% (range= -70 to 85) (p= 0.0007) after NET. A good response to NET defined as a decrease in tumor size and/or decrease of Ki-67 was found to be associated with a longer duration of NET, a change of CD4+ T-cells, a change of RANK expression on TILs and a higher number of CD68+ tumor-associated macrophages before the start of NET and also RANK expression on TILs before the start of NET. Conclusion: The immune micro-environment plays an important role in ER+/HER-2 negative BC. NET influences the composition and/or functional state of the infiltrating immune cells. Furthermore, changes in the immune micro-environment are also associated with treatment response. Breast Cancer Microenvironment Change After Neoadjuvant Endocrine Treatment Comparison of continuous and categorical parameters before and after NET. Comparison of the continuous parameters was done using Wilcoxon signed rank test. Comparison of the categorical parameters was done using a Chi-square test. sTIL: stromal tumour infiltrating lymphocytes and NET: neoadjuvant endocrine therapy. Bold values denote statistical significance at the p < 0.05 level. Citation Format: Gizem Oner, Glenn Broeckx, Christophe Van Berckelaer, Sevilay Altintas, Zafer Canturk, Wiebren Tjalma, Karen Zwaenepoel, Zwi Berneman, Marc Peeters, Patrick Pauwels, Peter A van Dam. Breast Cancer Microenvironment Change After Neoadjuvant Endocrine Treatment Breast Cancer Microenvironment Change After Neoadjuvant Endocrine Treatment [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD9-03.

S154 SMAD4-Mediated Interaction of Epithelial and Dendritic Cells

S154 SMAD4-Mediated Interaction of Epithelial and Dendritic Cells

Avatar Mice Underscore the Role of the T Cell-Dendritic Cell Crosstalk in Ebola Virus Disease and Reveal Mechanisms of Protection in Survivors

ABSTRACTEbola virus disease (EVD) is a complex infectious disease characterized by high inflammation, multiorgan failure, the dysregulation of innate and adaptive immune responses, and coagulation abnormalities. Evidence accumulated over the last 2 decades indicates that, during fatal EVD, the infection of antigen-presenting cells (APC) and the dysregulation of T cell immunity preclude a successful transition between innate and adaptive immunity, which constitutes a key disease checkpoint. In order to better understand the contribution of the APC-T cell crosstalk to EVD pathophysiology, we have developed avatar mice transplanted with human, donor-specific APCs and T cells. Here, we show that the transplantation of T cells and APCs from Ebola virus (EBOV)-naive individuals into avatar mice results in severe disease and death and that this phenotype is dependent on T cell receptor (TCR)-major histocompatibility complex (MCH) recognition. Conversely, avatar mice were rescued from death induced by EBOV infection after the transplantation of both T cells and plasma from EVD survivors. These results strongly suggest that protection from EBOV reinfection requires both cellular and humoral immune memory responses.IMPORTANCE The crosstalk between dendritic cells and T cells marks the transition between innate and adaptive immune responses, and it constitutes an important checkpoint in EVD. In this study, we present a mouse avatar model in which T cell and dendritic cell interactions from a specific donor can be studied during EVD. Our findings indicate that T cell receptor-major histocompatibility complex-mediated T cell-dendritic cell interactions are associated with disease severity, which mimics the main features of severe EVD in these mice. Resistance to an EBOV challenge in the model was achieved via the transplantation of both survivor T cells and plasma.

Human surfactant protein D facilitates SARS-CoV-2 pseudotype binding and entry in DC-SIGN expressing cells, and downregulates spike protein induced inflammation.

Lung surfactant protein D (SP-D) and Dendritic cell-specific intercellular adhesion molecules-3 grabbing non-integrin (DC-SIGN) are pathogen recognising C-type lectin receptors. SP-D has a crucial immune function in detecting and clearing pulmonary pathogens; DC-SIGN is involved in facilitating dendritic cell interaction with naïve T cells to mount an anti-viral immune response. SP-D and DC-SIGN have been shown to interact with various viruses, including SARS-CoV-2, an enveloped RNA virus that causes COVID-19. A recombinant fragment of human SP-D (rfhSP-D) comprising of α-helical neck region, carbohydrate recognition domain, and eight N-terminal Gly-X-Y repeats has been shown to bind SARS-CoV-2 Spike protein and inhibit SARS-CoV-2 replication by preventing viral entry in Vero cells and HEK293T cells expressing ACE2. DC-SIGN has also been shown to act as a cell surface receptor for SARS-CoV-2 independent of ACE2. Since rfhSP-D is known to interact with SARS-CoV-2 Spike protein and DC-SIGN, this study was aimed at investigating the potential of rfhSP-D in modulating SARS-CoV-2 infection. Coincubation of rfhSP-D with Spike protein improved the Spike Protein: DC-SIGN interaction. Molecular dynamic studies revealed that rfhSP-D stabilised the interaction between DC-SIGN and Spike protein. Cell binding analysis with DC-SIGN expressing HEK 293T and THP- 1 cells and rfhSP-D treated SARS-CoV-2 Spike pseudotypes confirmed the increased binding. Furthermore, infection assays using the pseudotypes revealed their increased uptake by DC-SIGN expressing cells. The immunomodulatory effect of rfhSP-D on the DC-SIGN: Spike protein interaction on DC-SIGN expressing epithelial and macrophage-like cell lines was also assessed by measuring the mRNA expression of cytokines and chemokines. RT-qPCR analysis showed that rfhSP-D treatment downregulated the mRNA expression levels of pro-inflammatory cytokines and chemokines such as TNF-α, IFN-α, IL-1β, IL- 6, IL-8, and RANTES (as well as NF-κB) in DC-SIGN expressing cells challenged by Spike protein. Furthermore, rfhSP-D treatment was found to downregulate the mRNA levels of MHC class II in DC expressing THP-1 when compared to the untreated controls. We conclude that rfhSP-D helps stabilise the interaction between SARS- CoV-2 Spike protein and DC-SIGN and increases viral uptake by macrophages via DC-SIGN, suggesting an additional role for rfhSP-D in SARS-CoV-2 infection.

SIRPα - CD47 axis regulates dendritic cell-T cell interactions and TCR activation during T cell priming in spleen.

The SIRPα-CD47 axis plays an important role in T cell recruitment to sites of immune reaction and inflammation but its role in T cell antigen priming is incompletely understood. Employing OTII TCR transgenic mice bred to Cd47-/- (Cd47KO) or SKI mice, a knock-in transgenic animal expressing non-signaling cytoplasmic-truncated SIRPα, we investigated how the SIRPα-CD47 axis contributes to antigen priming. Here we show that adoptive transfer of Cd47KO or SKI Ova-specific CD4+ T cells (OTII) into Cd47KO and SKI recipients, followed by Ova immunization, elicited reduced T cell division and proliferation indices, increased apoptosis, and reduced expansion compared to transfer into WT mice. We confirmed prior reports that splenic T cell zone, CD4+ conventional dendritic cells (cDCs) and CD4+ T cell numbers were reduced in Cd47KO and SKI mice. We report that in vitro derived DCs from Cd47KO and SKI mice exhibited impaired migration in vivo and exhibited reduced CD11c+ DC proximity to OTII T cells in T cell zones after Ag immunization, which correlates with reduced TCR activation in transferred OTII T cells. These findings suggest that reduced numbers of CD4+ cDCs and their impaired migration contributes to reduced T cell-DC proximity in splenic T cell zone and reduced T cell TCR activation, cell division and proliferation, and indirectly increased T cell apoptosis.

Identification and validation of ecto-5' nucleotidase as an immunotherapeutic target in multiple myeloma

Interaction of plasmacytoid dendritic cells (pDCs) with multiple myeloma (MM) cells, T- or NK-effector cells in the bone marrow (BM) microenvironment induces tumor cell growth, as well as inhibits innate and adaptive immune responses. Defining pDC-MM interaction-triggered immunosuppressive mechanism(s) will enable design of interventional therapies to augment anti-MM immunity. In the present study, we show that pDC-MM interactions induce metabolic enzyme Ecto-5' Nucleotidase/CD73 in both pDCs and MM cells. Gene expression database from MM patients showed that CD73 levels inversely correlate with overall survival. Using our pDC-MM coculture models, we found that blockade of CD73 with anti-CD73 Abs: decreases adenosine levels; activates MM patient pDCs; triggers cytotoxic T lymphocytes (CTL) activity against autologous patient MM cells. Combination of anti-CD73 Abs and an immune-stimulating agent TLR-7 agonist enhances autologous MM-specific CD8+ CTL activity. Taken together, our preclinical data suggest that the therapeutic targeting of CD73, alone or in combination with TLR-7 agonist, represents a promising novel strategy to restore host anti-MM immunity.

Interaction of Human Dendritic Cells with Graphene Oxide Nanoparticles In Vitro.

We studied the effect of graphene oxide nanoparticles on the differentiation of human dendritic cells and uptake of nanoparticles by these cells in vitro. The objects of the study were mononuclear cells from healthy donors induced into the phenotype of dendritic cells by cytokines (IL-6 and GM-CSF). We used graphene oxide nanoparticles of different sizes functionalized with linear or branched PEG (P-GO or bP-GO) in concentrations of 5 and 25 μg/ml. It was found that graphene oxide nanoparticles did not affect the viability and percentage of dendritic cells in the culture. However, P-GO nanoparticles (25 μg/ml) suppressed the expression of CD83 on the surface of dendritic cells in cultures, thereby suppressing cell differentiation. Dendritic cells internalized P-GO nanoparticles, particles in high concentration were more actively engulfed, but the size of the particles and the type of PEG did not affect the intensity of this process. In general, P-GO nanoparticles in a concentration of 25 μg/ml can regulate differentiation of dendritic cells by suppressing their maturation.

P-097: Preclinical validation of Ecto-5’ Nucleotidase (NT5E/CD73) as a novel immunotherapeutic target in Multiple Myeloma

<h3>Background</h3> The interaction of plasmacytoid dendritic cells (pDCs) with multiple myeloma (MM) cells, and T- or NK-cells in the bone marrow (BM) microenvironment triggers enhanced tumor growth, as well as inhibits innate and adaptive immune responses. In the present study, we analyzed the genetic changes in MM cells triggered by co-culture with pDCs using next generation sequencing (NGS), and identified that pDC-MM interactions induce metabolic enzyme Ecto-5' Nucleotidase (NT5E/CD73) in both pDCs and MM cells. CD73 has been implicated in cancer metabolism and immunosuppression via nucleotide metabolism pathway. <h3>Methods</h3> Purified MM patient pDCs (n=3) were co-cultured with MM cells (1pDC/5MM; n=3) for 48h, followed by separation of MM cells from pDCs by flow. Total RNA from MM cells was subjected to RNAseq analysis using Illumina NGS. Data were analyzed by VIPER workflow to generate differential expression. The log2FC (fold change) values in co-cultures vs MM alone, with a False Discovery Rate adjusted p value of <0.05, was considered significant. Cytotoxic T lymphocyte (CTL) assay: MM patient BM CD8+ T-cells were co-cultured with autologous pDCs (pDC:T/1:10) in the presence or absence of anti-CD73 Ab (0.5 µg/ml) for 3 days; pre-stained MM cells were added for 24h (10T:1MM), followed by FACS quantification of viable MM cells. <h3>Results</h3> A total of 9200 and 9250 genes were differentially expressed based on negative binomial distribution (DEseq2) and linear (Limma) RNA-seq models, respectively (p<0.05). MM cells cultured with (n=3) or without pDCs (n=3) clustered into two distinct groups, indicating contact-dependent transcriptional changes in MM cells after co-culture. pDC-MM interaction regulates several pathways including DNA replication/repair, cell cycle, and nucleotide metabolism. We showed that: 1) pDC-MM interactions induce transcription of adenosine-signaling pathway enzyme NT5E/CD73 in MM cells (1.34-fold increase after co-culture; p=0.0002); 2) Both pDCs and MM cells express CD73, and pDC-MM interactions further increase CD73 levels in MM cells (p=0.008); 3) pDC-MM interactions increase adenosine generation (5.5-fold), and importantly, CD73 blockade by anti-CD73 Ab decreases adenosine production (p=0.0167); 4) CD73 blockade activates MM pDCs, evidenced by the increased expression of CD40/CD83/CD86/HLA-DR on pDCs, and also restores pDCs ability to activate autologous T cells; 5) Targeting CD73 induces MM-specific CD8+ CTL activity against autologous MM cells; and 6) a combination of anti-CD73 Ab and TLR7 agonist triggers more potent MM-specific CD8+ CTL activity against autologous MM cells than either agent alone (%viable MM: anti-CD73 Ab:70%; TLR7 agonist:60%; combo:30%; p=0.009;n=7). <h3>Conclusions</h3> Our preclinical data therefore suggest that the therapeutic targeting of CD73, alone or in combination with TLR7 agonist, represents a promising novel strategy to restore host anti-MM immunity.

Transmigration across a Steady-State Blood-Brain Barrie Induces Activation of Circulating Dendritic Cells Partly Mediated by Actin Cytoskeletal Reorganization.

The central nervous system (CNS) is considered to be an immunologically unique site, in large part given its extensive protection by the blood–brain barrier (BBB). As our knowledge of the complex interaction between the peripheral immune system and the CNS expands, the mechanisms of immune privilege are being refined. Here, we studied the interaction of dendritic cells (DCs) with the BBB in steady–state conditions and observed that transmigrated DCs display an activated phenotype and stronger T cell-stimulatory capacity as compared to non-migrating DCs. Next, we aimed to gain further insights in the processes underlying activation of DCs following transmigration across the BBB. We investigated the interaction of DCs with endothelial cells as well as the involvement of actin cytoskeletal reorganization. Whereas we were not able to demonstrate that DCs engulf membrane fragments from fluorescently labelled endothelial cells during transmigration across the BBB, we found that blocking actin restructuring of DCs by latrunculin-A significantly impaired in vitro migration of DC across the BBB and subsequent T cell-stimulatory capacity, albeit no effect on migration-induced phenotypic activation could be demonstrated. These observations contribute to the current understanding of the interaction between DCs and the BBB, ultimately leading to the design of targeted therapies capable to inhibit autoimmune inflammation of the CNS.

IgG-Complexed Adenoviruses Induce Human Plasmacytoid Dendritic Cell Activation and Apoptosis.

Following repeat exposure to many human adenoviruses (HAdVs), most adults harbour long-lived B- and T-cell responses. Combined, this response typically protects us for years from re-infection by the same HAdV type. In spite of these immune responses, some HAdV types are associated with persistent infections that constitute a life-threatening risk when an individual’s T-cell response is compromised. By contrast, patients with B-cell deficiencies do not appear to be at a greater risk of HAdV disease. This dichotomy begs the question of the secondary role of anti-HAdV antibodies during host defence. In this study, we explored IgG-complexed (IC)-HAdV5 and primary human plasmacytoid dendritic cell (pDC) interactions. We found that IC-HAdV5 are efficiently internalized in pDCs, stimulate their activation through TLR9 signalling, and cause apoptosis. These data may help reconcile the enigma of robust immune response to HAdVs, while concurrently allowing persistence.

CD97 stabilises the immunological synapse between dendritic cells and T cells and is targeted for degradation by the Salmonella effector SteD.

The Salmonella enterica effector SteD depletes mature MHC class II (mMHCII) molecules from the surface of infected antigen-presenting cells through ubiquitination of the cytoplasmic tail of the mMHCII β chain. This requires the Nedd4 family HECT E3 ubiquitin ligase Wwp2 and a tumor-suppressing transmembrane protein adaptor Tmem127. Here, through a proteomic screen of dendritic cells, we found that SteD targets the plasma membrane protein CD97 for degradation by a similar mechanism. SteD enhanced ubiquitination of CD97 on K555 and mutation of this residue eliminated the effect of SteD on CD97 surface levels. We showed that CD97 localises to and stabilises the immunological synapse between dendritic cells and T cells. Removal of CD97 by SteD inhibited dendritic cell-T cell interactions and reduced T cell activation, independently of its effect on MHCII. Therefore, SteD suppresses T cell immunity by two distinct processes.

Helicobacter pylori infected gastric epithelial cells drive dendritic cells towards a tolerogenic phenotype.

Abstract The interactions of dendritic cells (DCs) with the gastric epithelium are thought to play a role in shaping DC function and thus the adaptive immune response to Helicobacter pylori (H. pylori) infection. We have shown that DCs are recruited to the H. pylori-infected gastric epithelium, positioning them for uptake of bacterial antigen from the gastric lumen. Using a gastric organoid model of H. pylori infection, we sought to define how the interactions between gastric epithelial cells and DCs regulate the antigen-presenting cell capacity of DCs. Supernatants were collected from organoids microinjected with H. pylori (infected) or PBS (mock), and monocyte-derived dendritic cells (MoDCs) were incubated with these supernatants. Flow cytometry data showed that the supernatant from infected organoids drove the DCs toward a tolerogenic state, as the expression of CD40, CD83, and CD86 was significantly decreased compared to incubation with supernatants from mock infected organoids, whereas CCR7 expression was increased consistent with a more tolerogenic phenotype. DCs treated with supernatants from infected, but not mock-infected organoids suppressed the proliferation of naïve autologous T cells. We also assessed T cell polarization using a cytokine array and found an increase in Th1, Th17 and Treg cytokines, but a decrease in Th2 cytokines in T cells that were challenged with DCs pre-treated with supernatants from infected organoids compared to mock-infected organoids. In summary, we have shown that H. pylori-infected gastric epithelium drives the DCs toward a tolerogenic state, resulting in reduced expression of maturation markers and CD4+ T cell proliferation while maintaining the DCs’ ability to induce T cell cytokine secretion.

Natural Killer-Dendritic Cell Interactions in Liver Cancer: Implications for Immunotherapy.

Simple SummaryThe reciprocal crosstalk between dendritic cells (DCs) and natural killer (NK) cells plays a pivotal role in regulating immune defense against viruses and tumors. The Th-cell polarizing ability, cytokine-producing capacity, chemokine expression, and migration of DCs are regulated by activated NK cells. Conversely, the effector functions including lysis and cytokine production, proliferation, and migration of NK cells are influenced by close interactions with activated DCs. In this review, we explore the impact of DC–NK cell crosstalk and its therapeutic potential in immune control of liver malignances.Natural killer (NK) and dendritic cells (DCs) are innate immune cells that play a crucial role in anti-tumor immunity. NK cells kill tumor cells through direct cytotoxicity and cytokine secretion. DCs are needed for the activation of adaptive immune responses against tumor cells. Both NK cells and DCs are subdivided in several subsets endowed with specialized effector functions. Crosstalk between NK cells and DCs leads to the reciprocal control of their activation and polarization of immune responses. In this review, we describe the role of NK cells and DCs in liver cancer, focusing on the mechanisms involved in their reciprocal control and activation. In this context, intrahepatic NK cells and DCs present unique immunological features, due to the constant exposure to non-self-circulating antigens. These interactions might play a fundamental role in the pathology of primary liver cancer, namely hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC). Additionally, the implications of these immune changes are relevant from the perspective of improving the cancer immunotherapy strategies in HCC and ICC patients.

Expansion of dysfunctional CD56-CD16+ NK cells in chronic hepatitis B patients.

Natural killer (NK) cells are primary innate effector cells that play an important role in the control of human viral infections. During chronic viral infection, NK cells undergo significant changes in phenotype, function and subset distribution, including the appearance of CD56-CD16+ (CD56-) NK cells, previously identified in chronic human immunodeficiency virus (HIV) and hepatitis C virus infection. However, the presence of CD56- NK cells in the pathogenesis of chronic hepatitis B (CHB) remains unknown. Phenotype and function of CD56- NK cells from patients with CHB (n=28) were assessed using flow cytometry and in vitro stimulation with HBV antigen. CHB patients had a higher frequency of CD56- NK cells compared to healthy controls in peripheral blood (6.2% vs 1.4%, P<.0001). Compared to CD56+ NK cells, CD56- NK cells had increased expression of inhibitory receptors, and reduced expression of activating receptors, as measured by MFI and qPCR. CD56- NK cells were less responsive to target cell and cytokine stimulation compared to their CD56+ counterparts. In addition, CD56- NK cells demonstrated defective dendritic cells (DCs) interactions resulting in reduced DCs maturation, lower expression of NK CD69 and impaired capacity of NK cells to eliminate immature DCs in co-culture studies. Finally, frequency of CD56- NK cells was positively correlated with serum HBV DNA levels. Chronic HBV infection induces the expansion of highly dysfunctional of CD56- NK cells that likely contribute to inefficient innate and adaptive antiviral immune response in chronic HBV infection.