Physical and functional interaction among Irf8 enhancers during dendritic cell differentiation.

The production of type 1 conventional dendritic cells (cDC1s) requires high expression of the transcription factor IRF8. Three enhancers at the Irf8 3' region function in a differentiation stage-specific manner. However, whether and how these enhancers interact physically and functionally remains unclear. Here, we show that the Irf8 3' enhancers directly interact with each other and contact the Irf8 gene body during cDC1 differentiation. The +56 kb enhancer, which functions from multipotent progenitor stages, activates the other 3' enhancers through an IRF8-dependent transcription factor program, that is, in trans. Then, the +32 kb enhancer, which operates in cDC1-committed cells, reversely acts in cis on the other 3' enhancers to maintain the high expression of Irf8. Indeed, mice with compound heterozygous deletion of the +56 and +32 kb enhancers are unable to generate cDC1s. These results illustrate how multiple enhancers cooperate to induce a lineage-determining transcription factor gene during cell differentiation.

Universal recording of immune cell interactions in vivo.

Immune cells rely on transient physical interactions with other immune and non-immune populations to regulate their function1. To study these 'kiss-and-run' interactions directly in vivo, we previously developed LIPSTIC (labelling immune partnerships by SorTagging intercellular contacts)2, an approach that uses enzymatic transfer of a labelled substrate between the molecular partners CD40L and CD40 to label interacting cells. Reliance on this pathway limited the use of LIPSTIC to measuring interactions between CD4+ T helper cells and antigen-presenting cells, however. Here we report the development of a universal version of LIPSTIC (uLIPSTIC), which can record physical interactions both among immune cells and between immune and non-immune populations irrespective of the receptors and ligands involved. We show that uLIPSTIC can be used, among other things, to monitor the priming of CD8+ T cells by dendritic cells, reveal the steady-state cellular partners of regulatory T cells and identify germinal centre-resident T follicular helper cells on the basis of their ability to interact cognately with germinal centre B cells. By coupling uLIPSTIC with single-cell transcriptomics, we build a catalogue of the immune populations that physically interact with intestinal epithelial cells at the steady state and profile the evolution of the interactome of lymphocytic choriomeningitis virus-specific CD8+ T cells in multiple organs following systemic infection. Thus, uLIPSTIC provides a broadly useful technology for measuring and understanding cell-cell interactions across multiple biological systems.

Trail Formation Alleviates Excessive Adhesion and Maintains Efficient Neutrophil Migration.

Migrating neutrophils are found to leave behind subcellular trails in vivo, but the underlying mechanisms remain unclear. Here, an in vitro cell migration test plus an in vivo observation was applied to monitor neutrophil migration on intercellular cell adhesion molecule-1 (ICAM-1) presenting surfaces. Results indicated that migrating neutrophils left behind long-lasting, chemokine-containing trails. Trail formation tended to alleviate excessive cell adhesion enhanced by the trans-binding antibody and maintain efficient cell migration, which was associated with differential instantaneous edge velocity between the cell front and rear. CD11a and CD11b worked differently in inducing trail formation with polarized distributions on the cell body and uropod. Trail release at the cell rear was attributed to membrane ripping, in which ß2-integrin was disrupted from the cell membrane through myosin-mediated rear contraction and integrin-cytoskeleton dissociation, potentiating a specialized strategy of integrin loss and cell deadhesion to maintain efficient migration. Moreover, neutrophil trails left on the substrate served as immune forerunners to recruit dendritic cells. These results provided an insight in elucidating the mechanisms of neutrophil trail formation and deciphering the roles of trail formation in efficient neutrophil migration.

A Morbillivirus Infection Shifts DC Maturation Toward a Tolerogenic Phenotype to Suppress T Cell Activation.

Viruses have evolved numerous strategies to impair immunity so that they can replicate more efficiently. Among those, the immunosuppressive effects of morbillivirus infection can be particularly problematic, as they allow secondary infections to take hold in the host, worsening disease prognosis. In the present work, we hypothesized that the highly contagious morbillivirus peste des petits ruminants virus (PPRV) could target monocytes and dendritic cells (DC) to contribute to the immunosuppressive effects produced by the infection. Monocytes isolated from healthy sheep, a natural host of the disease, were able be infected by PPRV and this impaired the differentiation and phagocytic ability of immature monocyte-derived DC (MoDC). We also assessed PPRV capacity to infect differentiated MoDC. Ovine MoDC could be productively infected by PPRV, and this drastically reduced MoDC capacity to activate allogeneic T cell responses. Transcriptomic analysis of infected MoDC indicated that several tolerogenic DC signature genes were upregulated upon PPRV infection. Furthermore, PPRV-infected MoDC could impair the proliferative response of autologous CD4+ and CD8+ T cell to the mitogen concanavalin A (ConA), which indicated that DC targeting by the virus could promote immunosuppression. These results shed new light on the mechanisms employed by morbillivirus to suppress the host immune responses. IMPORTANCE Morbilliviruses pose a threat to global health given their high infectivity. The morbillivirus peste des petits ruminants virus (PPRV) severely affects small-ruminant-productivity and leads to important economic losses in communities that rely on these animals for subsistence. PPRV produces in the infected host a period of severe immunosuppression that opportunistic pathogens exploit, which worsens the course of the infection. The mechanisms of PPRV immunosuppression are not fully understood. In the present work, we demonstrate that PPRV can infect professional antigen-presenting cells called dendritic cells (DC) and disrupt their capacity to elicit an immune response. PPRV infection promoted a DC activation profile that favored the induction of tolerance instead of the activation of an antiviral immune response. These results shed new light on the mechanisms employed by morbilliviruses to suppress the immune responses.

Hypoxic human proximal tubular epithelial cells undergo ferroptosis and elicit an NLRP3 inflammasome response in CD1c+ dendritic cells.

Inflammasomes are multiprotein platforms responsible for the release of pro-inflammatory cytokines interleukin (IL)-1ß and IL-18. Mouse studies have identified inflammasome activation within dendritic cells (DC) as pivotal for driving tubulointerstitial fibrosis and inflammation, the hallmarks of chronic kidney disease (CKD). However, translation of this work to human CKD remains limited. Here, we examined the complex tubular cell death pathways mediating inflammasome activation in human kidney DC and, thus, CKD progression. Ex vivo patient-derived proximal tubular epithelial cells (PTEC) cultured under hypoxic (1% O2) conditions modelling the CKD microenvironment showed characteristics of ferroptotic cell death, including mitochondrial dysfunction, reductions in the lipid repair enzyme glutathione peroxidase 4 (GPX4) and increases in lipid peroxidation by-product 4-hydroxynonenal (4-HNE) compared with normoxic PTEC. The addition of ferroptosis inhibitor, ferrostatin-1, significantly reduced hypoxic PTEC death. Human CD1c+ DC activated in the presence of hypoxic PTEC displayed significantly increased production of inflammasome-dependent cytokines IL-1ß and IL-18. Treatment of co-cultures with VX-765 (caspase-1/4 inhibitor) and MCC950 (NLRP3 inflammasome inhibitor) significantly attenuated IL-1ß/IL-18 levels, supporting an NLRP3 inflammasome-dependent DC response. In line with these in vitro findings, in situ immunolabelling of human fibrotic kidney tissue revealed a significant accumulation of tubulointerstitial CD1c+ DC containing active inflammasome (ASC) specks adjacent to ferroptotic PTEC. These data establish ferroptosis as the primary pattern of PTEC necrosis under the hypoxic conditions of CKD. Moreover, this study identifies NLRP3 inflammasome signalling driven by complex tubulointerstitial PTEC-DC interactions as a key checkpoint for therapeutic targeting in human CKD.

Chromatin structure undergoes global and local reorganization during murine dendritic cell development and activation.

Classical dendritic cells (cDCs) are essential for immune responses and differentiate from hematopoietic stem cells via intermediate progenitors, such as monocyte-DC progenitors (MDPs) and common DC progenitors (CDPs). Upon infection, cDCs are activated and rapidly express host defense-related genes, such as those encoding cytokines and chemokines. Chromatin structures, including nuclear compartments and topologically associating domains (TADs), have been implicated in gene regulation. However, the extent and dynamics of their reorganization during cDC development and activation remain unknown. In this study, we comprehensively determined higher-order chromatin structures by Hi-C in DC progenitors and cDC subpopulations. During cDC differentiation, chromatin activation was initially induced at the MDP stage. Subsequently, a shift from inactive to active nuclear compartments occurred at the cDC gene loci in CDPs, which was followed by increased intra-TAD interactions and loop formation. Mechanistically, the transcription factor IRF8, indispensable for cDC differentiation, mediated chromatin activation and changes into the active compartments in DC progenitors, thereby possibly leading to cDC-specific gene induction. Using an infection model, we found that the chromatin structures of host defense-related gene loci were preestablished in unstimulated cDCs, indicating that the formation of higher-order chromatin structures prior to infection may contribute to the rapid responses to pathogens. Overall, these results suggest that chromatin structure reorganization is closely related to the establishment of cDC-specific gene expression and immune functions. This study advances the fundamental understanding of chromatin reorganization in cDC differentiation and activation.

Ultrasound improved immune adjuvant delivery to induce DC maturation and T cell activation.

Tumor immunotherapy has emerged as a promising approach to tumor treatment. Currently, immune adjuvant-based therapeutic modalities are rarely curative in solid tumors owing to challenges including the low permeability and extremely poor water solubility of these adjuvants, limiting their ability to effectively promote dendritic cell (DC) maturation. Herein, we employed ultrasound-mediated cavitation (UMC) to promote the delivery of Toll-like receptor agonist (R837)-loaded pH-responsive liposomes (PEOz-Lip@R837) to tumors. The tumor-associated antigens (TAAs) produced by UMC treatment exhibited vaccinal activity, particularly in the presence of immune adjuvants, together promoting the maturation of DC and inducing cytokine production. Importantly, UMC can down-regulate immune checkpoint molecules, like Cd274, Foxp3 and Ctla4, synergistically stimulating the activation and proliferation of T cells in the body to facilitate tumor treatment. This UMC-enhanced PEOz-Lip@R837 approach was able to induce a robust antitumor immune response capable of arresting primary and distant tumor growth, while also developing immunological memory, protecting against tumor rechallenge following initial tumor clearance. Overall, these results highlight a promising UMC- and pH-sensitive immune adjuvant delivery-based treatment for tumors with the potential for clinical application.

IL-1ß expression in bone marrow dendritic cells is induced by TLR2 agonists and regulates HSC function.

Hematopoietic stem/progenitor cells (HSPCs) reside in localized microenvironments, or niches, in the bone marrow that provide key signals regulating their activity. A fundamental property of hematopoiesis is the ability to respond to environmental cues such as inflammation. How these cues are transmitted to HSPCs within hematopoietic niches is not well established. Here, we show that perivascular bone marrow dendritic cells (DCs) express a high basal level of Toll-like receptor-1 (TLR1) and TLR2. Systemic treatment with a TLR1/2 agonist induces HSPC expansion and mobilization. It also induces marked alterations in the bone marrow microenvironment, including a decrease in osteoblast activity and sinusoidal endothelial cell numbers. TLR1/2 agonist treatment of mice in which Myd88 is deleted specifically in DCs using Zbtb46-Cre show that the TLR1/2-induced expansion of multipotent HPSCs, but not HSPC mobilization or alterations in the bone marrow microenvironment, is dependent on TLR1/2 signaling in DCs. Interleukin-1ß (IL-1ß) is constitutively expressed in both murine and human DCs and is further induced after TLR1/2 stimulation. Systemic TLR1/2 agonist treatment of Il1r1-/- mice show that TLR1/2-induced HSPC expansion is dependent on IL-1ß signaling. Single-cell RNA-sequencing of low-risk myelodysplastic syndrome bone marrow revealed that IL1B and TLR1 expression is increased in DCs. Collectively, these data suggest a model in which TLR1/2 stimulation of DCs induces secretion of IL-1ß and other inflammatory cytokines into the perivascular niche, which in turn, regulates multipotent HSPCs. Increased DC TLR1/2 signaling may contribute to altered HSPC function in myelodysplastic syndrome by increasing local IL-1ß expression.

Ablation of cDC2 development by triple mutations within the Zeb2 enhancer.

The divergence of the common dendritic cell progenitor1-3 (CDP) into the conventional type 1 and type 2 dendritic cell (cDC1 and cDC2, respectively) lineages4,5 is poorly understood. Some transcription factors act in the commitment of already specified progenitors-such as BATF3, which stabilizes Irf8 autoactivation at the +32 kb Irf8 enhancer4,6-but the mechanisms controlling the initial divergence of CDPs remain unknown. Here we report the transcriptional basis of CDP divergence and describe the first requirements for pre-cDC2 specification. Genetic epistasis analysis7 suggested that Nfil3 acts upstream of Id2, Batf3 and Zeb2 in cDC1 development but did not reveal its mechanism or targets. Analysis of newly generated NFIL3 reporter mice showed extremely transient NFIL3 expression during cDC1 specification. CUT&RUN and chromatin immunoprecipitation followed by sequencing identified endogenous NFIL3 binding in the -165 kb Zeb2 enhancer8 at three sites that also bind the CCAAT-enhancer-binding proteins C/EBPα and C/EBPß. In vivo mutational analysis using CRISPR-Cas9 targeting showed that these NFIL3-C/EBP sites are functionally redundant, with C/EBPs supporting and NFIL3 repressing Zeb2 expression at these sites. A triple mutation of all three NFIL3-C/EBP sites ablated Zeb2 expression in myeloid, but not lymphoid progenitors, causing the complete loss of pre-cDC2 specification and mature cDC2 development in vivo. These mice did not generate T helper 2 (TH2) cell responses against Heligmosomoides polygyrus infection, consistent with cDC2 supporting TH2 responses to helminths9-11. Thus, CDP divergence into cDC1 or cDC2 is controlled by competition between NFIL3 and C/EBPs at the -165 kb Zeb2 enhancer.

Targeting SLC7A11 improves efferocytosis by dendritic cells and wound healing in diabetes.

Chronic non-healing wounds are a major complication of diabetes, which affects 1 in 10 people worldwide. Dying cells in the wound perpetuate the inflammation and contribute to dysregulated tissue repair1-3. Here we reveal that the membrane transporter SLC7A11 acts as a molecular brake on efferocytosis, the process by which dying cells are removed, and that inhibiting SLC7A11 function can accelerate wound healing. Transcriptomics of efferocytic dendritic cells in mouse identified upregulation of several SLC7 gene family members. In further analyses, pharmacological inhibition of SLC7A11, or deletion or knockdown of Slc7a11 using small interfering RNA enhanced efferocytosis in dendritic cells. Slc7a11 was highly expressed in dendritic cells in skin, and single-cell RNA sequencing of inflamed skin showed that Slc7a11 was upregulated in innate immune cells. In a mouse model of excisional skin wounding, inhibition or loss of SLC7A11 expression accelerated healing dynamics and reduced the apoptotic cell load in the wound. Mechanistic studies revealed a link between SLC7A11, glucose homeostasis and diabetes. SLC7A11-deficient dendritic cells were dependent on aerobic glycolysis using glucose derived from glycogen stores for increased efferocytosis; also, transcriptomics of efferocytic SLC7A11-deficient dendritic cells identified increased expression of genes linked to gluconeogenesis and diabetes. Further, Slc7a11 expression was higher in the wounds of diabetes-prone db/db mice, and targeting SLC7A11 accelerated their wound healing. The faster healing was also linked to the release of the TGFß family member GDF15 from efferocytic dendritic cells. In sum, SLC7A11 is a negative regulator of efferocytosis, and removing this brake improves wound healing, with important implications for wound management in diabetes.

R848/TLR7-Mediated Stronger CD8+ T Immunity Is Dependent on DC-NK Cell Interactions.

BACKGROUND: Toll-like receptor (TLR) 7 agonists are effective candidates for Th1 immune adjuvants, which compensate for the insufficient Th1 immune responses induced by traditional adjuvants. This effect is currently dependent on TLR7-mediated induction of dendritic cell (DC) maturation and increased IL-12 production. METHODS: In vivo, we intraperitoneally injected TLR agonists with OVA, and LNs were collected for detection. In vitro, Activated DCs, natural killer (NK) cells, and CD8+ T cells were tested using flow cytometry for surface expression and enzyme-linked immunosorbent assay for cytokine production. NK cell migration was evaluated using transwell system. All experiments were performed in both C57BL/6 and BALB/C backgrounds. RESULTS: Our findings revealed that the enhanced CD8+ T immunity characterized by CD8+ T accumulation, proliferation, and IFN-γ+CD8+ T induction induced by R848 was attributed to DC-dependent NK cell migration and DC-NK interactions. Our results demonstrated that R848 induced CD8+ T cell accumulation and IFN-γ+CD8+ T cells in lymph nodes (LNs) to a greater degree in vivo than TLR4 agonists (lipopolysaccharide) and TLR9 agonists (Class C CPG). R848-activated DCs enhanced CD8+ T cell proliferation and increased IFN-γ+CD8+ T cells with the assistance of NK cells. In contrast, depletion of NK cell decreased IFN-γ+CD8+ T cell production. Greater NK cell migration to LNs occurred in R848-immunized mice. A similar effect of R848 on NK cell migration was observed in an in vitro transwell study. When co-cultured, NK cells plus R848 could promote DCs maturation, and in turn, DCs in combination of R848 augmented NK cells activation. Further studies demonstrated that among several TLR agonists, R848 produced the largest amount of the chemokine CXCL9 from activated DCs, which is relevant to NK cell migration. CXCL9 blockade reduced the number of migrated NK cells, and the addition of CXCL9 increased the number of NK cells. DISCUSSION: Taken together, R848-mediated stronger CD8+ T cell immunity does not depend on DC activation alone, rather that NK cells must also be considered. By increasing our immunological understanding of the effect of R848/TLR7, these findings provide a new perspective for applying R848 in future clinical studies.

Picturing of the Lung Tumor Cellular Composition by Multispectral Flow Cytometry.

The lung tumor microenvironment plays a critical role in the tumorigenesis and metastasis of lung cancer, resulting from the crosstalk between cancer cells and microenvironmental cells. Therefore, comprehensive identification and characterization of cell populations in the complex lung structure is crucial for development of novel targeted anti-cancer therapies. Here, a hierarchical clustering approach with multispectral flow cytometry was established to delineate the cellular landscape of murine lungs under steady-state and cancer conditions. Fluorochromes were used multiple times to be able to measure 24 cell surface markers with only 13 detectors, yielding a broad picture for whole-lung phenotyping. Primary and metastatic murine lung tumor models were included to detect major cell populations in the lung, and to identify alterations to the distribution patterns in these models. In the primary tumor models, major altered populations included CD324+ epithelial cells, alveolar macrophages, dendritic cells, and blood and lymph endothelial cells. The number of fibroblasts, vascular smooth muscle cells, monocytes (Ly6C+ and Ly6C-) and neutrophils were elevated in metastatic models of lung cancer. Thus, the proposed clustering approach is a promising method to resolve cell populations from complex organs in detail even with basic flow cytometers.

Novel and conventional inhibitors of canonical autophagy differently affect LC3-associated phagocytosis.

In autophagy, LC3-positive autophagophores fuse and encapsulate the autophagic cargo in a double-membrane structure. In contrast, lipidated LC3 (LC3-II) is directly formed at the phagosomal membrane in LC3-associated phagocytosis (LAP). In this study, we dissected the effects of autophagy inhibitors on LAP. SAR405, an inhibitor of VPS34, reduced levels of LC3-II and inhibited LAP. In contrast, the inhibitors of endosomal acidification bafilomycin A1 and chloroquine increased levels of LC3-II, due to reduced degradation in acidic lysosomes. However, while bafilomycin A1 inhibited LAP, chloroquine did not. Finally, EACC, which inhibits the fusion of autophagosomes with lysosomes, promoted LC3 degradation possibly by the proteasome. Targeting LAP with small molecule inhibitors is important given its emerging role in infectious and autoimmune diseases.

Quantifying corneal immune cells from human in vivo confocal microscopy images: Can manual quantification be improved with observer training?

Manually quantifying immune cells (ICs), commonly considered dendritic cells, in the corneal epithelium from in vivo confocal microscopy (IVCM) images can be influenced by observer bias. This study sought to evaluate the repeatability of manual IC quantification. Cell counts were first performed for 184 non-overlapping IVCM images by a single observer. Quantifications were undertaken to establish the total cell numbers per image, and the numbers of three cell morphological subtypes: mature ICs (with elongated dendrites), immature ICs (with short- or non-discernible dendrites) and globular cells (with large bodies and no visible dendrites). Cell counts were then repeated by the same observer, and independently undertaken by a second observer. Prior to these counts, both observers undertook an agreement 'training' process to define IC appearance and delineate the morphological subtypes. Total IC counts demonstrated excellent intra- and inter-observer reliability (intraclass correlation coefficients (ICC) > 0.90). Bland-Altman plots showed that interobserver measurement bias increased as a function of the total IC number in the image prior to consensus training. For total IC counts after the observer training process, there was no significant interobserver measurement bias. For IC morphological subtypes, there was a positive relationship between the mean inter-observer difference and average cell count for mature ICs and globular cells, but not immature ICs. In conclusion, higher variability in manual corneal IC counts exists when more cells are present in an IVCM image. Implementing an observer training process reduced inter-observer variability and minimised systematic measurement error.

Heme-stress activated NRF2 skews fate trajectories of bone marrow cells from dendritic cells towards red pulp-like macrophages in hemolytic anemia.

Heme is an erythrocyte-derived toxin that drives disease progression in hemolytic anemias, such as sickle cell disease. During hemolysis, specialized bone marrow-derived macrophages with a high heme-metabolism capacity orchestrate disease adaptation by removing damaged erythrocytes and heme-protein complexes from the blood and supporting iron recycling for erythropoiesis. Since chronic heme-stress is noxious for macrophages, erythrophagocytes in the spleen are continuously replenished from bone marrow-derived progenitors. Here, we hypothesized that adaptation to heme stress progressively shifts differentiation trajectories of bone marrow progenitors to expand the capacity of heme-handling monocyte-derived macrophages at the expense of the homeostatic generation of dendritic cells, which emerge from shared myeloid precursors. This heme-induced redirection of differentiation trajectories may contribute to hemolysis-induced secondary immunodeficiency. We performed single-cell RNA-sequencing with directional RNA velocity analysis of GM-CSF-supplemented mouse bone marrow cultures to assess myeloid differentiation under heme stress. We found that heme-activated NRF2 signaling shifted the differentiation of bone marrow cells towards antioxidant, iron-recycling macrophages, suppressing the generation of dendritic cells in heme-exposed bone marrow cultures. Heme eliminated the capacity of GM-CSF-supplemented bone marrow cultures to activate antigen-specific CD4 T cells. The generation of functionally competent dendritic cells was restored by NRF2 loss. The heme-induced phenotype of macrophage expansion with concurrent dendritic cell depletion was reproduced in hemolytic mice with sickle cell disease and spherocytosis and associated with reduced dendritic cell functions in the spleen. Our data provide a novel mechanistic underpinning of hemolytic stress as a driver of hyposplenism-related secondary immunodeficiency.

DNMT1 Deficiency Impacts on Plasmacytoid Dendritic Cells in Homeostasis and Autoimmune Disease.

Dendritic cells (DCs) are heterogeneous immune regulators involved in autoimmune diseases. Epigenomic mechanisms orchestrating DC development and DC subset diversification remain insufficiently understood but could be important to modulate DC fate for clinical purposes. By combining whole-genome methylation assessment with the analysis of mice expressing reduced DNA methyltransferase 1 levels, we show that distinct DNA methylation levels and patterns are required for the development of plasmacytoid DC and conventional DC subsets. We provide clonal in vivo evidence for DC lineage establishment at the stem cell level, and we show that a high DNA methylation threshold level is essential for Flt3-dependent survival of DC precursors. Importantly, reducing methylation predominantly depletes plasmacytoid DC and alleviates systemic lupus erythematosus in an autoimmunity mouse model. This study shows how DNA methylation regulates the production of DC subsets and provides a potential rationale for targeting autoimmune disease using hypomethylating agents.

Transition from cMyc to L-Myc during dendritic cell development coordinated by rising levels of IRF8.

During dendritic cell (DC) development, Myc expression in progenitors is replaced by Mycl in mature DCs, but when and how this transition occurs is unknown. We evaluated DC development using reporters for MYC, MYCL, and cell cycle proteins Geminin and CDT1 in wild-type and various mutant mice. For classical type 1 dendritic cells (cDC1s) and plasmacytoid DCs (pDCs), the transition occurred upon their initial specification from common dendritic cell progenitors (CDPs) or common lymphoid progenitors (CLPs), respectively. This transition required high levels of IRF8 and interaction with PU.1, suggesting the use of EICEs within Mycl enhancers. In pDCs, maximal MYCL induction also required the +41kb Irf8 enhancer that controls pDC IRF8 expression. IRF8 also contributed to repression of MYC. While MYC is expressed only in rapidly dividing DC progenitors, MYCL is most highly expressed in DCs that have exited the cell cycle. Thus, IRF8 levels coordinate the Myc-Mycl transition during DC development.

Effect of topical application of lipopolysaccharide on contact hypersensitivity.

Lipopolysaccharide (LPS) is the principal component of the outer membrane of gram-negative bacteria. The prior oral administration of LPS attenuates inflammatory responses, such as intestinal injury and atopic dermatitis, in mouse models; however, the underlying mechanism remains unclear. Here, we examined the effect of topical LPS application on allergic contact dermatitis and its mechanism of action using a murine contact hypersensitivity (CHS) model. Prolonged LPS application to the skin significantly suppressed 2,4-dinitrofluorobenzene (DNFB)-induced CHS. LPS application to the skin also reduced the phagocytosis of fluorescein isothiocyanate (FITC)-dextran by Langerhans and dendritic cells. Cutaneous cell migration into the skin-draining lymph nodes (LNs) induced by FITC painting was reduced by LPS application. During the CHS response, DNFB application induced T-cell proliferation and inflammatory cytokine production in skin-draining LNs, whereas prolonged LPS application inhibited DNFB-induced T-cell growth and interferon gamma production, indicating suppression of DNFB-induced sensitization. These results suggest that prolonged LPS application suppressed DNFB-induced sensitization and subsequently CHS response. Our findings imply that topical application of LPS may prevent allergic dermatitis such as CHS.

Interferon Signaling in Estrogen Receptor-positive Breast Cancer: A Revitalized Topic.

Cancer immunology is the most rapidly expanding field in cancer research, with the importance of immunity in cancer pathogenesis now well accepted including in the endocrine-related cancers. The immune system plays an essential role in the development of ductal and luminal epithelial differentiation in the mammary gland. Originally identified as evolutionarily conserved antipathogen cytokines, interferons (IFNs) have shown important immune-modulatory and antineoplastic properties when administered to patients with various types of cancer, including breast cancer. Recent studies have drawn attention to the role of tumor- and stromal-infiltrating lymphocytes in dictating therapy response and outcome of breast cancer patients, which, however, is highly dependent on the breast cancer subtype. The emerging role of tumor cell-inherent IFN signaling in the subtype-defined tumor microenvironment could influence therapy response with protumor activities in breast cancer. Here we review evidence with new insights into tumor cell-intrinsic and tumor microenvironment-derived IFN signaling, and the crosstalk of IFN signaling with key signaling pathways in estrogen receptor-positive (ER+) breast cancer. We also discuss clinical implications and opportunities exploiting IFN signaling to treat advanced ER+ breast cancer.