CD8α+ DCs can be induced in the absence of transcription factors Id2, Nfil3, and Batf3

The role of basic leucine zipper transcription factor E4BP4 in cancer: a review and update

Mutations in the genes of tumor cells and the disorder of immune microenvironment are the main factors of tumor development. The sensitivity of tumor cells to chemotherapy drugs affect the treatment of tumor. Nuclear transcription factor E4BP4 is dysregulated in a variety of malignant tumors. It can suppress the transcription of NFKBIA, RASSF8, SOSTDC1, FOXO-induced genes (TRAIL, FAS, GADD45a and GADD45b) and Hepcidin, up-regulate RCAN1-1 and PRNP, activate mTOR and p38 in cancer cells. Also, E4BP4 can regulate tumor immune microenvironment. TGFb1/Smad3/E4BP4/ IFNγ axis in NK cells plays an important role in antitumor immunotherapy. Over expression of E4BP4 inhibited the development of Th17 cells by directly binding to the RORγt promoter. Moreover, recent studies have shown that E4BP4 inhibited the expression of multidrug resistance genes. In this review, we summarize the molecular mechanism of E4BP4 in cancer cellular process, the effects of E4BP4 in cancer immunotherapy and antitumor drug resistance, to provide theoretical basis for tumor treatment strategies targeting E4BP4.

Mapping the tumor microenvironment in clear cell renal carcinoma by single-cell transcriptome analysis

Introduction: Clear cell renal cell carcinoma (ccRCC) is associated with unfavorable clinical outcomes. To identify viable therapeutic targets, a comprehensive understanding of intratumoral heterogeneity is crucial. In this study, we conducted bioinformatic analysis to scrutinize single-cell RNA sequencing data of ccRCC tumor and para-tumor samples, aiming to elucidate the intratumoral heterogeneity in the ccRCC tumor microenvironment (TME). Methods: A total of 51,780 single cells from seven ccRCC tumors and five para-tumor samples were identified and grouped into 11 cell lineages using bioinformatic analysis. These lineages included tumor cells, myeloid cells, T-cells, fibroblasts, and endothelial cells, indicating a high degree of heterogeneity in the TME. Copy number variation (CNV) analysis was performed to compare CNV frequencies between tumor and normal cells. The myeloid cell population was further re-clustered into three major subgroups: monocytes, macrophages, and dendritic cells. Differential expression analysis, gene ontology, and gene set enrichment analysis were employed to assess inter-cluster and intra-cluster functional heterogeneity within the ccRCC TME. Results: Our findings revealed that immune cells in the TME predominantly adopted an inflammatory suppression state, promoting tumor cell growth and immune evasion. Additionally, tumor cells exhibited higher CNV frequencies compared to normal cells. The myeloid cell subgroups demonstrated distinct functional properties, with monocytes, macrophages, and dendritic cells displaying diverse roles in the TME. Certain immune cells exhibited pro-tumor and immunosuppressive effects, while others demonstrated antitumor and immunostimulatory properties. Conclusion: This study contributes to the understanding of intratumoral heterogeneity in the ccRCC TME and provides potential therapeutic targets for ccRCC treatment. The findings emphasize the importance of considering the diverse functional roles of immune cells in the TME for effective therapeutic interventions.

Transcriptional regulation of dendritic cell development and function

Dendritic cells (DCs) are sentinel immune cells that form a critical bridge linking the innate and adaptive immune systems. Extensive research addressing the cellular origin and heterogeneity of the DC network has revealed the essential role played by the spatiotemporal activity of key transcription factors. In response to environmental signals DC mature but it is only following the sensing of environmental signals that DC can induce an antigen specific T cell response. Thus, whilst the coordinate action of transcription factors governs DC differentiation, sensing of environmental signals by DC is instrumental in shaping their functional properties. In this review, we provide an overview that focuses on recent advances in understanding the transcriptional networks that regulate the development of the reported DC subsets, shedding light on the function of different DC subsets. Specifically, we discuss the emerging knowledge on the heterogeneity of cDC2s, the ontogeny of pDCs, and the newly described DC subset, DC3. Additionally, we examine critical transcription factors such as IRF8, PU.1, and E2-2 and their regulatory mechanisms and downstream targets. We highlight the complex interplay between these transcription factors, which shape the DC transcriptome and influence their function in response to environmental stimuli. The information presented in this review provides essential insights into the regulation of DC development and function, which might have implications for developing novel therapeutic strategies for immune-related diseases.

Signaling pathways involved in the biological functions of dendritic cells and their implications for disease treatment

The ability of dendritic cells (DCs) to initiate and regulate adaptive immune responses is fundamental for maintaining immune homeostasis upon exposure to self or foreign antigens. The immune regulatory function of DCs is strictly controlled by their distribution as well as by cytokines, chemokines, and transcriptional programming. These factors work in conjunction to determine whether DCs exert an immunosuppressive or immune-activating function. Therefore, understanding the molecular signals involved in DC-dependent immunoregulation is crucial in providing insight into the generation of organismal immunity and revealing potential clinical applications of DCs. Considering the many breakthroughs in DC research in recent years, in this review we focused on three basic lines of research directly related to the biological functions of DCs and summarized new immunotherapeutic strategies involving DCs. First, we reviewed recent findings on DC subsets and identified lineage-restricted transcription factors that guide the development of different DC subsets. Second, we discussed the recognition and processing of antigens by DCs through pattern recognition receptors, endogenous/exogenous pathways, and the presentation of antigens through peptide/major histocompatibility complexes. Third, we reviewed how interactions between DCs and T cells coordinate immune homeostasis in vivo via multiple pathways. Finally, we summarized the application of DC-based immunotherapy for autoimmune diseases and tumors and highlighted potential research prospects for immunotherapy that targets DCs. This review provides a useful resource to better understand the immunomodulatory signals involved in different subsets of DCs and the manipulation of these immune signals can facilitate DC-based immunotherapy.

The role of dendritic cells in radiation-induced immune responses

Dendritic cells perform critical functions in bridging innate and adaptive immunity. Their ability to sense adjuvant signals in their environment, migrate on maturation, and cross-present cell-associated antigens enables these cells to carry antigen from tissue sites to lymph nodes, and thereby prime naïve T cells that cannot enter tissues. Despite being an infrequent cell type in tumors, we discuss how dendritic cells impact the immune environment of tumors and their response to cancer therapies. We review how radiation therapy of tumors can impact dendritic cells, through transfer of cell associated antigens to dendritic cells and the release of endogenous adjuvants, resulting in increased antigen presentation in the tumor-draining lymph nodes. We explore how tumor specific factors can result in negative regulation of dendritic cell function in the tumor, and the impact of direct radiation exposure to dendritic cells in the treatment field. These data suggest an important role for dendritic cell subpopulations in activating new T cell responses and boosting existing T cell responses to tumor associated antigens in tumor draining lymph nodes following radiation therapy. It further justifies a focus on the needs of the lymph node T cells to improve systemic anti-immunity following radiation therapy.

Origin, Phenotype, and Function of Mouse Dendritic Cell Subsets

Dendritic cells are cells of hematopoietic origin that are specialized in antigen presentation and instruction of innate and adaptive immune responses. They are a heterogenous group of cells populating lymphoid organs and most tissues. Dendritic cells are commonly separated in three main subsets that differ in their developmental paths, phenotype, and functions. Most studies on dendritic cells were done primarily in mice; therefore, in this chapter, we propose to summarize the current knowledge and recent progress on mouse dendritic cell subsets' development, phenotype, and functions.

The Emerging Role of Tissue-Resident Memory CD8+ T Lymphocytes in Human Digestive Tract Cancers

Malignant digestive tract tumors are a great threat to human public health. In addition to surgery, immunotherapy brings hope for the treatment of these tumors. Tissue-resident memory CD8⁺ T (Trm) cells are a focus of tumor immunology research and treatment due to their powerful cytotoxic effects, ability to directly kill epithelial-derived tumor cells, and overall impact on maintaining mucosal homeostasis and antitumor function in the digestive tract. They are a group of noncirculating immune cells expressing adhesion and migration molecules such as CD69, CD103, and CD49a that primarily reside on the barrier epithelium of nonlymphoid organs and respond rapidly to both viral and bacterial infection and tumorigenesis. This review highlights new research exploring the role of CD8⁺ Trm cells in a variety of digestive tract malignant tumors, including esophageal cancer, gastric cancer, colorectal cancer, and hepatocellular carcinoma. A summary of CD8⁺ Trm cell phenotypes and characteristics, tissue distribution, and antitumor functions in different tumor environments is provided, illustrating how these cells may be used in immunotherapies against digestive tract tumors.

Conventional type 1 dendritic cells protect against age-related adipose tissue dysfunction and obesity

Conventional dendritic cells (cDCs) scan and integrate environmental cues in almost every tissue, including exogenous metabolic signals. While cDCs are critical in maintaining immune balance, their role in preserving energy homeostasis is unclear. Here, we showed that Batf3-deficient mice lacking conventional type 1 DCs (cDC1s) had increased body weight and adiposity during aging. This led to impaired energy expenditure and glucose tolerance, insulin resistance, dyslipidemia, and liver steatosis. cDC1 deficiency caused adipose tissue inflammation that was preceded by a paucity of NK1.1⁺ invariant NKT (iNKT) cells. Accordingly, among antigen-presenting cells, cDC1s exhibited notable induction of IFN-γ production by iNKT cells, which plays a metabolically protective role in lean adipose tissue. Flt3L treatment, which expands the dendritic cell (DC) compartment, mitigated diet-induced obesity and hyperlipidemia in a Batf3-dependent manner. This effect was partially mediated by NK1.1⁺ cells. These results reveal a new critical role for the cDC1-iNKT cell axis in the regulation of adipose tissue homeostasis.

Dendritic Cell-Based Immunotherapy in Multiple Myeloma: Challenges, Opportunities, and Future Directions

Immunotherapeutic approaches, including adoptive cell therapy, revolutionized treatment in multiple myeloma (MM). As dendritic cells (DCs) are professional antigen-presenting cells and key initiators of tumor-specific immune responses, DC-based immunotherapy represents an attractive therapeutic approach in cancer. The past years, various DC-based approaches, using particularly ex-vivo-generated monocyte-derived DCs, have been tested in preclinical and clinical MM studies. However, long-term and durable responses in MM patients were limited, potentially attributed to the source of monocyte-derived DCs and the immunosuppressive bone marrow microenvironment. In this review, we briefly summarize the DC development in the bone marrow niche and the phenotypical and functional characteristics of the major DC subsets. We address the known DC deficiencies in MM and give an overview of the DC-based vaccination protocols that were tested in MM patients. Lastly, we also provide strategies to improve the efficacy of DC vaccines using new, improved DC-based approaches and combination therapies for MM patients.

Stimulation of a subset of natural killer T cells by CD103+ DC is required for GM-CSF and protection from pneumococcal infection

Innate-like T cells, including invariant natural killer T cells, mucosal-associated invariant T cells, and γδ T cells, are present in various barrier tissues, including the lung, where they carry out protective responses during infections. Here, we investigate their roles during pulmonary pneumococcal infection. Following infection, innate-like T cells rapidly increase in lung tissue, in part through recruitment, but T cell antigen receptor activation and cytokine production occur mostly in interleukin-17-producing NKT17 and γδ T cells. NKT17 cells are preferentially located within lung tissue prior to infection, as are CD103⁺ dendritic cells, which are important both for antigen presentation to NKT17 cells and γδ T cell activation. Whereas interleukin-17-producing γδ T cells are numerous, granulocyte-macrophage colony-stimulating factor is exclusive to NKT17 cells and is required for optimal protection. These studies demonstrate how particular cellular interactions and responses of functional subsets of innate-like T cells contribute to protection from pathogenic lung infection.

The AP-1 transcription factors c-Jun and JunB are essential for CD8α conventional dendritic cell identity

Dendritic cell (DC) development is orchestrated by lineage-determining transcription factors (TFs). Although, members of the activator-protein-1 (AP-1) family, including Batf3, have been implicated in conventional (c)DC specification, the role of Jun proteins is poorly understood. Here, we identified c-Jun and JunB as essential for cDC1 fate specification and function. In mice, Jun proteins regulate extrinsic and intrinsic pathways, which control CD8α cDC1 diversification, whereas CD103 cDC1 development is unaffected. The loss of c-Jun and JunB in DC progenitors diminishes the CD8α cDC1 pool and thus confers resistance to Listeria monocytogenes infection. Their absence in CD8α cDC1 results in impaired TLR triggering and antigen cross-presentation. Both TFs are required for the maintenance of the CD8α cDC1 subset and suppression of cDC2 identity on a transcriptional and phenotypic level. Taken together, these results demonstrate the essential role of c-Jun and JunB in CD8α cDC1 diversification, function, and maintenance of their identity.

MMP2 and TLRs modulate immune responses in the tumor microenvironment

The presence of an immunosuppressive tumor microenvironment is a major obstacle in the success of cancer immunotherapies. Because extracellular matrix components can shape the microenvironment, we investigated the role of matrix metalloproteinase 2 (MMP2) in melanoma tumorigenesis. We found that MMP2 signals proinflammatory pathways on antigen presenting cells, and this requires both TLR2 and TLR4. B16 melanoma cells that express MMP2 at baseline have slower kinetics in Tlr2^–/–Tlr4^–/– mice, implicating MMP2 in promoting tumor growth. Indeed, Mmp2 overexpression in B16 cells potentiated rapid tumor growth, which was accompanied by reduced intratumoral cytolytic cells and increased M2 macrophages. In contrast, knockdown of Mmp2 slowed tumor growth and enhanced T cell proliferation and NK cell recruitment. Finally, we found that these effects of MMP2 are mediated through dysfunctional DC–T cell cross-talk as they are lost in Batf3^–/– and Rag2^–/– mice. These findings provide insights into the detrimental role of endogenous alarmins like MMP2 in modulating immune responses in the tumor microenvironment.

XCR1+ type 1 conventional dendritic cells drive liver pathology in non-alcoholic steatohepatitis

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are prevalent liver conditions that underlie the development of life-threatening cirrhosis, liver failure and liver cancer. Chronic necro-inflammation is a critical factor in development of NASH, yet the cellular and molecular mechanisms of immune dysregulation in this disease are poorly understood. Here, using single-cell transcriptomic analysis, we comprehensively profiled the immune composition of the mouse liver during NASH. We identified a significant pathology-associated increase in hepatic conventional dendritic cells (cDCs) and further defined their source as NASH-induced boost in cycling of cDC progenitors in the bone marrow. Analysis of blood and liver from patients on the NAFLD/NASH spectrum showed that type 1 cDCs (cDC1) were more abundant and activated in disease. Sequencing of physically interacting cDC-T cell pairs from liver-draining lymph nodes revealed that cDCs in NASH promote inflammatory T cell reprogramming, previously associated with NASH worsening. Finally, depletion of cDC1 in XCR1^DTA mice or using anti-XCL1-blocking antibody attenuated liver pathology in NASH mouse models. Overall, our study provides a comprehensive characterization of cDC biology in NASH and identifies XCR1⁺ cDC1 as an important driver of liver pathology.

Programmed Death Ligand 1-Expressing Classical Dendritic Cells MitigateHelicobacter-Induced Gastritis

BACKGROUND & AIMS

Helicobacter pylori has been reported to modulate local immune responses to colonize persistently in gastric mucosa. Although the induced expression of programmed cell death ligand 1 (PD-L1) has been suggested as an immune modulatory mechanism for persistent infection of H pylori, the main immune cells expressing PD-L1 and their functions in Helicobacter-induced gastritis still remain to be elucidated.

METHODS

The blockades of PD-L1 with antibody or PD-L1-deficient bone marrow transplantation were performed in Helicobacter-infected mice. The main immune cells expressing PD-L1 in Helicobacter-infected stomach were determined by flow cytometry and immunofluorescence staining. Helicobacter felis or H pylori-infected dendritic cell (DC)-deficient mouse models including Flt3-/-, Zbtb46-diphtheria toxin receptor, and BDCA2-diphtheria toxin receptor mice were analyzed for pathologic changes and colonization levels. Finally, the location of PD-L1-expressing DCs and the correlation with H pylori infection were analyzed in human gastric tissues using multiplexed immunohistochemistry.

RESULTS

Genetic or antibody-mediated blockade of PD-L1 aggravated Helicobacter-induced gastritis with mucosal metaplasia. Gastric classical DCs expressed considerably higher levels of PD-L1 than other immune cells and co-localized with T cells in gastritis lesions from Helicobacter-infected mice and human beings. H felis- or H pylori-infected Flt3-/- or classical DC-depleted mice showed aggravated gastritis with severe T-cell and neutrophil accumulation with low bacterial loads compared with that in control mice. Finally, PD-L1-expressing DCs were co-localized with T cells and showed a positive correlation with H pylori infection in human subjects.

CONCLUSIONS

The PD-1/PD-L1 pathway may be responsible for the immune modulatory function of gastric DCs that protects the gastric mucosa from Helicobacter-induced inflammation, but allows persistent Helicobacter colonization.

Absence of Batf3 reveals a new dimension of cell state heterogeneity within conventional dendritic cells

Conventional dendritic cells (cDCs) are traditionally subdivided into cDC1 and cDC2 lineages. Batf3 is a cDC1-required transcription factor, and we observed that Batf3−/− mice harbor a population of cDC1-like cells co-expressing cDC2-associated surface molecules. Using single-cell RNA sequencing with integrated cell surface protein expression (CITE-seq), we found that Batf3−/− mitotic immature cDC1-like cells showed reduced expression of cDC1 features and increased levels of cDC2 features. In wild type, we also observed a proportion of mature cDC1 cells expressing surface features characteristic to cDC2 and found that overall cDC cell state heterogeneity was mainly driven by developmental stage, proliferation, and maturity. We detected population diversity within Sirpa+ cDC2 cells, including a Cd33+ cell state expressing high levels of Sox4 and lineage-mixed features characteristic to cDC1, cDC2, pDCs, and monocytes. In conclusion, these data suggest that multiple cDC cell states can co-express lineage-overlapping features, revealing a level of previously unappreciated cDC plasticity.

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Single-cell proteogenomics identifies additional layers of DC heterogeneity

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cDC diversity is driven by proliferation, developmental stage, and maturation

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Lack of Batf3 increases cDCs with lineage-mixed features

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Sox4+ cDCs represent a cell state of lineage-mixed features

Functions of Dendritic Cells and Its Association with Intestinal Diseases

Dendritic cells (DCs), including conventional DCs (cDCs) and plasmacytoid DCs (pDCs), serve as the sentinel cells of the immune system and are responsible for presenting antigen information. Moreover, the role of DCs derived from monocytes (moDCs) in the development of inflammation has been emphasized. Several studies have shown that the function of DCs can be influenced by gut microbes including gut bacteria and viruses. Abnormal changes/reactions in intestinal DCs are potentially associated with diseases such as inflammatory bowel disease (IBD) and intestinal tumors, allowing DCs to be a new target for the treatment of these diseases. In this review, we summarized the physiological functions of DCs in the intestinal micro-environment, their regulatory relationship with intestinal microorganisms and their regulatory mechanism in intestinal diseases.

Genetic models of human and mouse dendritic cell development and function

Dendritic cells (DCs) develop in the bone marrow from haematopoietic progenitors that have numerous shared characteristics between mice and humans. Human counterparts of mouse DC progenitors have been identified by their shared transcriptional signatures and developmental potential. New findings continue to revise models of DC ontogeny but it is well accepted that DCs can be divided into two main functional groups. Classical DCs include type 1 and type 2 subsets, which can detect different pathogens, produce specific cytokines and present antigens to polarize mainly naive CD8+ or CD4+ T cells, respectively. By contrast, the function of plasmacytoid DCs is largely innate and restricted to the detection of viral infections and the production of type I interferon. Here, we discuss genetic models of mouse DC development and function that have aided in correlating ontogeny with function, as well as how these findings can be translated to human DCs and their progenitors.

Dendritic Cells Revisited

Dendritic cells (DCs) possess the ability to integrate information about their environment and communicate it to other leukocytes, shaping adaptive and innate immunity. Over the years, a variety of cell types have been called DCs on the basis of phenotypic and functional attributes. Here, we refocus attention on conventional DCs (cDCs), a discrete cell lineage by ontogenetic and gene expression criteria that best corresponds to the cells originally described in the 1970s. We summarize current knowledge of mouse and human cDC subsets and describe their hematopoietic development and their phenotypic and functional attributes. We hope that our effort to review the basic features of cDC biology and distinguish cDCs from related cell types brings to the fore the remarkable properties of this cell type while shedding some light on the seemingly inordinate complexity of the DC field.

Resistance to Experimental Visceral Leishmaniasis in Mice Infected With Leishmania infantum Requires Batf3

Unveiling the protective immune response to visceral leishmaniasis is critical for a rational design of vaccines aimed at reducing the impact caused by this fatal, if left untreated, vector-borne disease. In this study we sought to determine the role of the basic leucine zipper transcription factor ATF-like 3 (Batf3) in the evolution of infection with Leishmania infantum, the causative agent of human visceral leishmaniasis in the Mediterranean Basin and Latin America. For that, Batf3-deficient mice in C57BL/6 background were infected with an L. infantum strain expressing the luciferase gene. Bioluminescent imaging, as well as in vitro parasite titration, demonstrated that Batf3-deficient mice were unable to control hepatic parasitosis as opposed to wild-type C57BL/6 mice. The impaired microbicide capacities of L. infantum-infected macrophages from Batf3-deficient mice mainly correlated with a reduction of parasite-specific IFN-γ production. Our results reinforce the implication of Batf3 in the generation of type 1 immunity against infectious diseases.

An IL-27-Driven Transcriptional Network Identifies Regulators of IL-10 Expression across T Helper Cell Subsets

Interleukin-27 (IL-27) is an immunoregulatory cytokine that suppresses inflammation through multiple mechanisms, including induction of IL-10, but the transcriptional network mediating its diverse functions remains unclear. Combining temporal RNA profiling with computational algorithms, we predict 79 transcription factors induced by IL-27 in T cells. We validate 11 known and discover 5 positive (Cebpb, Fosl2, Tbx21, Hlx, and Atf3) and 2 negative (Irf9 and Irf8) Il10 regulators, generating an experimentally refined regulatory network for Il10. We report two central regulators, Prdm1 and Maf, that cooperatively drive the expression of signature genes induced by IL-27 in type 1 regulatory T cells, mediate IL-10 expression in all T helper cells, and determine the regulatory phenotype of colonic Foxp3⁺ regulatory T cells. Prdm1/Maf double-knockout mice develop spontaneous colitis, phenocopying ll10-deficient mice. Our work provides insights into IL-27-driven transcriptional networks and identifies two shared Il10 regulators that orchestrate immunoregulatory programs across T helper cell subsets.

Zhang et al. construct a transcriptional network for IL-27-mediated Il10 production in CD4 T cells, characterize the function of 16 Il10 regulators, and uncover the role of two transcription factors, Prdm1 and Maf, in driving Il10 production in all T helper cells and in maintaining immune homeostasis in the colon.

Diurnal Rhythmicity Programs of Microbiota and Transcriptional Oscillation of Circadian Regulator, NFIL3

Circadian rhythms are a very exquisite mechanism to influence on transcriptional levels and physiological activities of various molecules that affect cell metabolic pathways. Long-term alteration of circadian rhythms increases the risk of cardiovascular diseases, hypertension, hypertriglyceridemia, and metabolic syndrome. A drastic change in dietary patterns can affect synchronizing the circadian clock within the metabolic system. Therefore, the interaction between the host and the bacterial community colonizing the mammalian gastrointestinal tract has a great impact on the circadian clock in diurnal programs. Here, we propose that the microbiota regulates body composition through the transcriptional oscillation of circadian regulators. The transcriptional regulator, NFIL3 (also called E4BP4) is a good example. Compositional change of the commensal bacteria influences the rhythmic expression of NFIL3 in the epithelium, which subsequently controls obesity and insulin resistance. Therefore, control of circadian regulators would be a promising therapeutic target for metabolic diseases.

Analysis and Augmentation of the Immunologic Bystander Effects of CAR T Cell Therapy in a Syngeneic Mouse Cancer Model

The therapeutic efficacy of adoptive transfer of T cells transduced with chimeric antigen receptors (CARs) has been limited in the treatment of solid cancers, partly due to tumor antigen heterogeneity. Overcoming lack of universal tumor antigen expression would be achieved if CAR T cells could induce bystander effects. To study this process, we developed a system where CAR T cells targeting mesothelin could cure tumors containing 100% antigen-positive cells in immunocompetent mice. Using this model, we found that the CAR T cells were unable to cure tumors, even when only 10% of the tumor cells were mesothelin negative. A bystander effect was not induced by co-administration of anti-PD-1, anti-CTLA-4, or anti-TGF-β (transforming growth factor β) antibodies; agonistic CD40 antibodies; or an IDO (indoleamine 2,3-dioxygenase) inhibitor. However, pretreatment with a non-lymphodepleting dose of cyclophosphamide (CTX) prior to CAR T cells resulted in cures of tumors with up to 25% mesothelin-negative cells. The mechanism was dependent on endogenous CD8 T cells but not on basic leucine zipper transcription factor ATF-like 3 (BATF3)-dependent dendritic cells. These data suggest that CAR T cell therapy of solid tumors, in which the targeted antigen is not expressed by the vast majority of tumor cells, will not likely be successful unless combination strategies to enhance bystander effects are used.

An Important Role for CD4+ T Cells in Adaptive Immunity to Toxoplasma gondii in Mice Lacking the Transcription Factor Batf3

Immunity to Toxoplasma gondii at early stages of infection in C57BL/6 mice depends on gamma interferon (IFN-γ) production by NK cells, while at later stages it is primarily mediated by CD8 T cells. We decided to explore the requirement for CD4 T cells during T. gondii infection in Batf3-/- mice, which lack CD8α+ dendritic cells (DCs) that are necessary for cross-presentation of cell-associated antigens to CD8 T cells. We show that in this immunodeficient background on a BALB/c background, CD4 T cells become important effector cells and are able to protect Batf3-/- mice from infection with the avirulent strain RHΔku80Δrop5 Independently of the initial NK cell activation, CD4 T cells in wild-type and Batf3-/- mice were the major source of IFN-γ. Importantly, memory CD4 T cells were sufficient to provide protective immunity following transfer into Batf3-/- mice and secondary challenge with the virulent RHΔku80 strain. Collectively, these results show that under situations where CD8 cell responses are impaired, CD4 T cells provide an important alternative immune response to T. gondiiIMPORTANCEToxoplasma gondii is a widespread parasite of animals that causes zoonotic infections in humans. Although healthy individuals generally control the infection with only moderate symptoms, it causes serious illness in newborns and those with compromised immune systems such as HIV-infected AIDS patients. Because rodents are natural hosts for T. gondii, laboratory mice provide an excellent model for studying immune responses. Here, we used a combination of an attenuated mutant strain of the parasite that effectively vaccinates mice, with a defect in a transcriptional factor that impairs a critical subset of dendritic cells, to studying the immune response to infection. The findings reveal that in BALB/c mice, CD4 memory T cells play a dominant role in producing IFN-γ needed to control chronic infection. Hence, BALB/c mice may provide a more appropriate model for declining immunity seen in HIV-AIDS patients where loss of CD4 cells is associated with emergence of opportunistic infections.

Transcriptional regulation of DC fate specification

Dendritic cells function in the immune system to instruct adaptive immune cells to respond accordingly to different threats. While conventional dendritic cells can be subdivided into two main subtypes, termed cDC1s and cDC2s, it is clear that further heterogeneity exists within these subtypes, particularly for cDC2s. Understanding the signals involved in specifying each of these lineages and subtypes thereof is crucial to (i) enable us to determine their specific functions and (ii) put us in a position to be able to target these cells to promote or prevent a specific function in any given disease setting. Although we still have much to learn regarding the specification of these cells, here we review the most recent advances in our understanding of this and highlight some of the next questions for the future.

Transcriptional control of dendritic cell development and functions

Dendritic cells (DCs) are major regulators of adaptive immunity, as they are not only capable to induce efficient immune responses, but are also crucial to maintain peripheral tolerance and thereby inhibit autoimmune reactions. DCs bridge the innate and the adaptive immune system by presenting peptides of self and foreign antigens as peptide MHC complexes to T cells. These properties render DCs as interesting target cells for immunomodulatory therapies in cancer, but also autoimmune diseases. Several subsets of DCs with special properties and functions have been described. Recent achievements in understanding transcriptional programs on single cell level, together with the generation of new murine models targeting specific DC subsets, advanced our current understanding of DC development and function. Thus, DCs arise from precursor cells in the bone marrow with distinct progenitor cell populations splitting the monocyte populations and macrophage populations from the DC lineage, which upon lineage commitment can be separated into conventional cDC1, cDC2, and plasmacytoid DCs (pDCs). The DC populations harbor intrinsic programs enabling them to react for specific pathogens in dependency on the DC subset, and thereby orchestrate T cell immune responses. Similarities, but also varieties, between human and murine DC subpopulations are challenging, and will require further investigation of human specimens under consideration of the influence of the tissue micromilieu and DC subset localization in the future.

Origin and development of classical dendritic cells

Classical dendritic cells (cDCs) are mononuclear phagocytes of hematopoietic origin specialized in the induction and regulation of adaptive immunity. Initially defined by their unique T cell activation potential, it became quickly apparent that cDCs would be difficult to distinguish from other phagocyte lineages, by solely relying on marker-based approaches. Today, cDCs definition increasingly embed their unique ontogenetic features. A growing consensus defines cDCs on multiple criteria including: (1) dependency on the fms-like tyrosine kinase 3 ligand hematopoietic growth factor, (2) development from the common DC bone marrow progenitor, (3) constitutive expression of the transcription factor ZBTB46 and (4) the ability to induce, after adequate stimulation, the activation of naïve T lymphocytes. cDCs are a heterogeneous cell population that contains two main subsets, named type 1 and type 2 cDCs, arising from divergent ontogenetic pathways and populating multiple lymphoid and non-lymphoid tissues. Here, we present recent knowledge on the cellular and molecular pathways controlling the specification and commitment of cDC subsets from murine and human hematopoietic stem cells.

Shared Transcriptional Control of Innate Lymphoid Cell and Dendritic Cell Development

Innate immunity and adaptive immunity consist of highly specialized immune lineages that depend on transcription factors for both function and development. In this review, we dissect the similarities between two innate lineages, innate lymphoid cells (ILCs) and dendritic cells (DCs), and an adaptive immune lineage, T cells. ILCs, DCs, and T cells make up four functional immune modules and interact in concert to produce a specified immune response. These three immune lineages also share transcriptional networks governing the development of each lineage, and we discuss the similarities between ILCs and DCs in this review.

The crucial role of ZEB2: From development to epithelial-to-mesenchymal transition and cancer complexity

Zinc finger E-box binding homeobox 2 (ZEB2) is a DNA-binding transcription factor, which is mainly involved in epithelial-to-mesenchymal transition (EMT). EMT is a conserved process during which mature and adherent epithelial-like state is converted into a mobile mesenchymal state. Emerging data indicate that ZEB2 plays a pivotal role in EMT-induced processes such as development, differentiation, and malignant mechanisms, for example, drug resistance, cancer stem cell-like traits, apoptosis, survival, cell cycle arrest, tumor recurrence, and metastasis. In this regard, the understanding of mentioned subjects in the development of normal and cancerous cells could be helpful in cancer complexity of diagnosis and therapy. In this study, we review recent findings about the biological properties of ZEB2 in healthy and cancerous states to find new approaches for cancer treatment.

Cryptic activation of an Irf8 enhancer governs cDC1 fate specification

Induction of the transcription factor Irf8 in the common dendritic cell progenitor (CDP) is required for classical type 1 dendritic cell (cDC1) fate specification, but the mechanisms controlling this induction are unclear. In the present study Irf8 enhancers were identified via chromatin profiling of dendritic cells and CRISPR/Cas9 genome editing was used to assess their roles in Irf8 regulation. An enhancer 32 kilobases (kb) downstream of the Irf8 transcriptional start site (+32-kb Irf8) that was active in mature cDC1s was required for the development of this lineage, but not for its specification. Instead, a +41-kb Irf8 enhancer, previously thought to be active only in plasmacytoid dendritic cells, was found to also be transiently accessible in cDC1 progenitors, and deleting this enhancer prevented the induction of Irf8 in CDPs and abolished cDC1 specification. Thus, cryptic activation of the +41-kb Irf8 enhancer in dendritic cell progenitors is responsible for cDC1 fate specification.

An Nfil3-Zeb2-Id2 pathway imposes Irf8 enhancer switching during cDC1 development

Classical type 1 dendritic cells (cDC1s) are required for antiviral and antitumor immunity, which necessitates an understanding of their development. Development of the cDC1 progenitor requires an E-protein-dependent enhancer located 41 kilobases downstream of the transcription start site of the transcription factor Irf8 (+41-kb Irf8 enhancer), but its maturation instead requires the Batf3-dependent +32-kb Irf8 enhancer. To understand this switch, we performed single-cell RNA sequencing of the common dendritic cell progenitor (CDP) and identified a cluster of cells that expressed transcription factors that influence cDC1 development, such as Nfil3, Id2 and Zeb2. Genetic epistasis among these factors revealed that Nfil3 expression is required for the transition from Zeb2hi and Id2lo CDPs to Zeb2lo and Id2hi CDPs, which represent the earliest committed cDC1 progenitors. This genetic circuit blocks E-protein activity to exclude plasmacytoid dendritic cell potential and explains the switch in Irf8 enhancer usage during cDC1 development.

IL-10-Dependent Crosstalk between Murine Marginal Zone B Cells, Macrophages, and CD8α+ Dendritic Cells Promotes Listeria monocytogenes Infection

Type 1 CD8α⁺ conventional dendritic cells (cDC1s) are required for CD8⁺ T cell priming but, paradoxically, promote splenic Listeria monocytogenes infection. Using mice with impaired cDC2 function, we ruled out a role for cDC2s in this process and instead discovered an interleukin-10 (IL-10)-dependent cellular crosstalk in the marginal zone (MZ) that promoted bacterial infection. Mice lacking the guanine nucleotide exchange factor DOCK8 or CD19 lost IL-10-producing MZ B cells and were resistant to Listeria. IL-10 increased intracellular Listeria in cDC1s indirectly by reducing inducible nitric oxide synthase expression early after infection and increasing intracellular Listeria in MZ metallophilic macrophages (MMMs). These MMMs trans-infected cDC1s, which, in turn, transported Listeria into the white pulp to prime CD8⁺ T cells. However, this also facilitated bacterial expansion. Therefore, IL-10-mediated crosstalk between B cells, macrophages, and cDC1s in the MZ promotes both Listeria infection and CD8⁺ T cell activation.

Langerin+CD8+ Dendritic Cells in the Splenic Marginal Zone: Not So Marginal After All

Dendritic cells (DC) fulfill an essential sentinel function within the immune system, acting at the interface of innate and adaptive immunity. The DC family, both in mouse and man, shows high functional heterogeneity in order to orchestrate immune responses toward the immense variety of pathogens and other immunological threats. In this review, we focus on the Langerin⁺CD8⁺ DC subpopulation in the spleen. Langerin⁺CD8⁺ DC exhibit a high ability to take up apoptotic/dying cells, and therefore they are essential to prime and shape CD8⁺ T cell responses. Next to the induction of immunity toward blood-borne pathogens, i.e., viruses, these DC are important for the regulation of tolerance toward cell-associated self-antigens. The ontogeny and differentiation pathways of CD8⁺CD103⁺ DC should be further explored to better understand the immunological role of these cells as a prerequisite of their therapeutic application.

Flow Cytometry Data Preparation Guidelines for Improved Automated Phenotypic Analysis

Advances in flow cytometry (FCM) increasingly demand adoption of computational analysis tools to tackle the ever-growing data dimensionality. In this study, we tested different data input modes to evaluate how cytometry acquisition configuration and data compensation procedures affect the performance of unsupervised phenotyping tools. An analysis workflow was set up and tested for the detection of changes in reference bead subsets and in a rare subpopulation of murine lymph node CD103⁺ dendritic cells acquired by conventional or spectral cytometry. Raw spectral data or pseudospectral data acquired with the full set of available detectors by conventional cytometry consistently outperformed datasets acquired and compensated according to FCM standards. Our results thus challenge the paradigm of one-fluorochrome/one-parameter acquisition in FCM for unsupervised cluster-based analysis. Instead, we propose to configure instrument acquisition to use all available fluorescence detectors and to avoid integration and compensation procedures, thereby using raw spectral or pseudospectral data for improved automated phenotypic analysis.

Negligible Role for Deletion Mediated by cDC1 in CD8+ T Cell Tolerance

Deletion of CD8⁺ T cells by dendritic cells (DCs) is recognized as a critical mechanism of immune tolerance to self-antigens. Although DC-mediated peripheral deletion of autoreactive CD8⁺ T cells has been demonstrated using T cells reactive to model Ags, its role in shaping the naturally occurring polyclonal CD8⁺ T cell repertoire has not been defined. Using Batf3^-/- mice lacking cross-presenting CD8α⁺ and CD103⁺ DCs (also known as type 1 conventional [cDC1]), we demonstrate that peripheral deletion of CD8⁺ T cells reactive to a model tissue Ag is dependent on cDC1. However, endogenous CD8⁺ T cells from the periphery of Batf3^-/- mice do not exhibit heightened self-reactivity, and deep TCR sequencing of CD8⁺ T cells from Batf3^-/- and Batf3^+/+ mice reveals that cDC1 have a minimal impact on shaping the peripheral CD8⁺ T cell repertoire. Thus, although evident in reductionist systems, deletion of polyclonal self-specific CD8⁺ T cells by cDC1 plays a negligible role in enforcing tolerance to natural self-ligands.

Batf3-Dependent Genes Control Tumor Rejection Induced by Dendritic Cells Independently of Cross-Presentation

The BATF3-dependent cDC1 lineage of conventional dendritic cells (cDC) is required for rejection of immunogenic sarcomas and for rejection of progressive sarcomas during checkpoint blockade therapy. One unique function of the cDC1 lineage is the efficient cross-presentation of tumor-derived neoantigens to CD8+ T cells, but it is not clear that this is the only unique function of cDC1 required for tumor rejection. We previously showed that BATF3 functions during cDC1 lineage commitment to maintain IRF8 expression in the specified cDC1 progenitor. However, since cDC1 progenitors do not develop into mature cDC1s in Batf3 -/- mice, it is still unclear whether BATF3 has additional functions in mature cDC1 cells. A transgenic Irf8-Venus reporter allele increases IRF8 protein concentration sufficiently to allow autonomous cDC1 development in spleens of Batf3 -/- mice. These restored Batf3 -/- cDC1s are transcriptionally similar to control wild-type cDC1s but have reduced expression of a restricted set of cDC1-specific genes. Restored Batf3 -/- cDC1s are able to cross-present cell-associated antigens both in vitro and in vivo However, Batf3 -/- cDC1 exhibit altered characteristics in vivo and are unable to mediate tumor rejection. These results show that BATF3, in addition to regulating Irf8 expression to stabilize cDC1 lineage commitment, also controls expression of a small set of genes required for cDC1-mediated tumor rejection. These BATF3-regulated genes may be useful targets in immunotherapies aimed at promoting tumor rejection.

Suppression of Th1 Priming by TLR2 Agonists during Cutaneous Immunization Is Mediated by Recruited CCR2+ Monocytes

Effective subunit vaccines require the incorporation of adjuvants that stimulate cells of the innate immune system to generate protective adaptive immune responses. Pattern recognition receptor agonists are a growing class of potential adjuvants that can shape the character of the immune response to subunit vaccines by directing the polarization of CD4 T cell differentiation to various functional subsets. In the current study, we applied a high-throughput in vitro screen to assess murine CD4 T cell polarization by a panel of pattern recognition receptor agonists. This identified lipopeptides with TLR2 agonist activity as exceptional Th1-polarizing adjuvants. In vivo, we demonstrated that i.v. administration of TLR2 agonists with Ag in mice replicated the findings from in vitro screening by promoting strong Th1 polarization. In contrast, TLR2 agonists inhibited priming of Th1 responses when administered cutaneously in mice. This route-specific suppression was associated with infiltrating CCR2⁺ cells in the skin-draining lymph nodes and was not uniquely dependent on any of the well characterized subsets of dendritic cells known to reside in the skin. We further demonstrated that priming of CD4 T cells to generate Th1 effectors following immunization with the Mycobacterium bovis bacillus Calmette-Guérin (BCG) strain, a lipoprotein-rich bacterium recognized by TLR2, was dependent on the immunization route, with significantly greater Th1 responses with i.v. compared with intradermal administration of BCG. A more complete understanding of route-dependent TLR2 responses may be critical for informed design of novel subunit vaccines and for improvement of BCG and other vaccines based on live-attenuated organisms.

The role of inhibitor of binding or differentiation 2 in the development and differentiation of immune cells

Inhibitor of binding or differentiation 2 (Id2), a member of helix-loop-helix (HLH) transcriptional factors, is recently reported as an important regulator of the development or differentiation of immune cells. It has been demonstrated that Id2 plays a critical role in the early lymphopoiesis. However, it has been discovered recently that Id2 displays new functions in different immune cells. In the adaptive immune cells, Id2 is required for determining T-cell subsets and B cells. In addition, Id2 is also involved in the development of innate immune cells, including dendritic cells (DCs), natural killer (NK) cells, and other innate lymphoid cells (ILCs). Here, we review the current reports about the role of Id2 in the development or differentiation of main immune cells.

Batf3-Dependent Dendritic Cells Promote Optimal CD8 T Cell Responses against Respiratory Poxvirus Infection

Respiratory infection with vaccinia virus (VacV) elicits robust CD8⁺ T cell responses that play an important role in host resistance. In the lung, VacV encounters multiple tissue-resident antigen-presenting cell (APC) populations, but which cell plays a dominant role in priming of virus-specific CD8⁺ effector T cell responses remains poorly defined. We used Batf3^-/- mice to investigate the impact of CD103⁺ and CD8α⁺ dendritic cell (DC) deficiency on anti-VacV CD8⁺ T cell responses. We found that Batf3^-/- mice were more susceptible to VacV infection, exhibiting profound weight loss, which correlated with impaired accumulation of gamma interferon (IFN-γ)-producing CD8⁺ T cells in the lungs. This was largely due to defective priming since early in the response, antigen-specific CD8⁺ T cells in the draining lymph nodes of Batf3^-/- mice expressed significantly reduced levels of Ki67, CD25, and T-bet. These results underscore a specific role for Batf3-dependent DCs in regulating priming and expansion of effector CD8⁺ T cells necessary for host resistance against acute respiratory VacV infection.IMPORTANCE During respiratory infection with vaccinia virus (VacV), a member of Poxviridae family, CD8⁺ T cells play important role in resolving the primary infection. Effector CD8⁺ T cells clear the virus by accumulating in the infected lungs in large numbers and secreting molecules such as IFN-γ that kill virally infected cells. However, precise cell types that regulate the generation of effector CD8⁺ T cells in the lungs are not well defined. Dendritic cells (DCs) are a heterogeneous population of immune cells that are recognized as key initiators and regulators of T-cell-mediated immunity. In this study, we reveal that a specific subset of DCs that are dependent on the transcription factor Batf3 for their development regulate the magnitude of CD8⁺ T cell effector responses in the lungs, thereby providing protection during pulmonary VacV infection.

Genealogy, Dendritic Cell Priming, and Differentiation of Tissue-Resident Memory CD8+ T Cells

Tissue-resident memory CD8⁺ T (Trm) cells define a distinct non-recirculating subset. Trm cells constitute a first line of defense against local infections in barrier tissues, but they are also found in non-barrier tissues and play a role in antitumor immunity. Their differentiation in tissues and their phenotypical, transcriptional, and functional characteristics are the object of active research. Herein, we will discuss the potential existence of committed CD8⁺ Trm precursors and the genealogy of memory CD8⁺ T cell subsets. In addition to the priming of naive T cells, there is some plasticity of antigen-experienced effector and memory T cell subsets to generate Trm precursors. Local inflammation, antigen presentation, and cytokines drive Trm differentiation. It is of prime interest how specific dendritic cell subsets modulate priming and differentiation of Trm cells, as well as their reactivation within tissues. Research on how we can manipulate generation of memory T cells subsets is key for improved vaccination strategies.

Antigen cross-presentation and T-cell cross-priming in cancer immunology and immunotherapy

Dendritic cells (DCs) are the main professional antigen-presenting cells for induction of T-cell adaptive responses. Cancer cells express tumor antigens, including neoantigens generated by nonsynonymous mutations, but are poor for antigen presentation and for providing costimulatory signals for T-cell priming. Mounting evidence suggests that antigen transfer to DCs and their surrogate presentation on major histocompatibility complex class I and II molecules together with costimulatory signals is paramount for induction of viral and cancer immunity. Of the great diversity of DCs, BATF3/IRF8-dependent conventional DCs type 1 (cDC1) excel at cross-presentation of tumor cell-associated antigens. Location of cDC1s in the tumor correlates with improved infiltration by CD8+ T cells and tumor-specific T-cell immunity. Indeed, cDC1s are crucial for antitumor efficacy using checkpoint inhibitors and anti-CD137 agonist monoclonal antibodies in mouse models. Enhancement and exploitation of T-cell cross-priming by cDC1s offer opportunities for improved cancer immunotherapy, including in vivo targeting of tumor antigens to internalizing receptors on cDC1s and strategies to increase their numbers, activation and priming capacity within tumors and tumor-draining lymph nodes.

Flt-3L Expansion of Recipient CD8α+ Dendritic Cells Deletes Alloreactive Donor T Cells and Represents an Alternative to Posttransplant Cyclophosphamide for the Prevention of GVHD

Purpose: Allogeneic bone marrow transplantation (BMT) provides curative therapy for leukemia via immunologic graft-versus-leukemia (GVL) effects. In practice, this must be balanced against life threatening pathology induced by graft-versus-host disease (GVHD). Recipient dendritic cells (DC) are thought to be important in the induction of GVL and GVHD.Experimental Design: We have utilized preclinical models of allogeneic BMT to dissect the role and modulation of recipient DCs in controlling donor T-cell-mediated GVHD and GVL.Results: We demonstrate that recipient CD8α⁺ DCs promote activation-induced clonal deletion of allospecific donor T cells after BMT. We compared pretransplant fms-like tyrosine kinase-3 ligand (Flt-3L) treatment to the current clinical strategy of posttransplant cyclophosphamide (PT-Cy) therapy. Our results demonstrate superior protection from GVHD with the immunomodulatory Flt-3L approach, and similar attenuation of GVL responses with both strategies. Strikingly, Flt-3L treatment permitted maintenance of the donor polyclonal T-cell pool, where PT-Cy did not.Conclusions: These data highlight pre-transplant Flt-3L therapy as a potent new therapeutic strategy to delete alloreactive T cells and prevent GVHD, which appears particularly well suited to haploidentical BMT where the control of infection and the prevention of GVHD are paramount. Clin Cancer Res; 24(7); 1604-16. ©2018 AACR.

Effective Priming of Herpes Simplex Virus-Specific CD8+ T Cells In Vivo Does Not Require Infected Dendritic Cells

Resolution of virus infections depends on the priming of virus-specific CD8⁺ T cells by dendritic cells (DC). While this process requires major histocompatibility complex (MHC) class I-restricted antigen presentation by DC, the relative contribution to CD8⁺ T cell priming by infected DC is less clear. We have addressed this question in the context of a peripheral infection with herpes simplex virus 1 (HSV). Assessing the endogenous, polyclonal HSV-specific CD8⁺ T cell response, we found that effective in vivo T cell priming depended on the presence of DC subsets specialized in cross-presentation, while Langerhans cells and plasmacytoid DC were dispensable. Utilizing a novel mouse model that allows for the in vivo elimination of infected DC, we also demonstrated in vivo that this requirement for cross-presenting DC was not related to their infection but instead reflected their capacity to cross-present HSV-derived antigen. Taking the results together, this study shows that infected DC are not required for effective CD8⁺ T cell priming during a peripheral virus infection.IMPORTANCE The ability of some DC to present viral antigen to CD8⁺ T cells without being infected is thought to enable the host to induce killer T cells even when viruses evade or kill infected DC. However, direct experimental in vivo proof for this notion has remained elusive. The work described in this study characterizes the role that different DC play in the induction of virus-specific killer T cell responses and, critically, introduces a novel mouse model that allows for the selective elimination of infected DC in vivo Our finding that HSV-specific CD8⁺ T cells can be fully primed in the absence of DC infection shows that cross-presentation by DC is indeed sufficient for effective CD8⁺ T cell priming during a peripheral virus infection.

TIM-3 Regulates CD103+ Dendritic Cell Function and Response to Chemotherapy in Breast Cancer

Intratumoral CD103⁺ dendritic cells (DCs) are necessary for anti-tumor immunity. Here we evaluated the expression of immune regulators by CD103⁺ DCs in a murine model of breast cancer and identified expression of TIM-3 as a target for therapy. Anti-TIM-3 antibody improved response to paclitaxel chemotherapy in models of triple-negative and luminal B disease, with no evidence of toxicity. Combined efficacy was CD8⁺ T cell dependent and associated with increased granzyme B expression; however, TIM-3 expression was predominantly localized to myeloid cells in both human and murine tumors. Gene expression analysis identified upregulation of Cxcl9 within intratumoral DCs during combination therapy, and therapeutic efficacy was ablated by CXCR3 blockade, Batf3 deficiency, or Irf8 deficiency.

Interleukin-12 from CD103+ Batf3-Dependent Dendritic Cells Required for NK-Cell Suppression of Metastasis

Several host factors may affect the spread of cancer to distant organs; however, the intrinsic role of dendritic cells (DC) in controlling metastasis is poorly described. Here, we show in several tumor models that although the growth of primary tumors in Batf3-deficient mice, which lack cross-presenting DCs, was not different from primary tumors in wild-type (WT) control mice, Batf3-deficient mice had increased experimental and spontaneous metastasis and poorer survival. The increased metastasis was independent of CD4⁺ and CD8⁺ T lymphocytes, but required NK cells and IFNγ. Chimeric mice in which Batf3-dependent DCs uniformly lacked the capacity to produce IL12 had metastatic burdens similar to the Batf3-deficient mice, suggesting that Batf3⁺ DCs were the only cell type whose IL12 production was critical for controlling metastasis. We found that IL12-YFP reporter mice, whose lungs were injected with B16F10 melanoma, had increased numbers of IL12-expressing CD103⁺ DCs with enhanced CD86 expression. Bone-marrow-derived DCs from WT, but not Batf3-deficient, mice activated NK cells to produce IFNγ in an IL12-dependent manner and therapeutic injection of recombinant mouse IL12 decreased metastasis in both WT and Batf3-deficient mice. Analysis of TCGA datasets revealed an association between high expression of BATF3 and IRF8 and improved survival of breast cancer patients; BATF3 expression also significantly correlated with NK-cell receptor genes, IL12, and IFNG Collectively, our findings show that IL12 from CD103⁺ DCs is critical for NK cell-mediated control of tumor metastasis. Cancer Immunol Res; 5(12); 1098-108. ©2017 AACR.

Dendritic Cells in Sepsis: Pathological Alterations and Therapeutic Implications

Sepsis is the leading cause of death for critically ill patients in recent years. Dendritic cells (DCs) are important antigen-presenting cells and play a key role in immune response by regulating the innate and adaptive immunity. The number of DCs, the differentiation of monocytes into DCs, and the levels of surface molecules associated with the function of DCs are changed in the development of sepsis. There are many mechanisms involved in the alterations of DCs during sepsis, including the induction of apoptosis, reactive oxygen species generation, activation of the Wnt signaling pathway, epigenetic regulation, and variation in Toll-like receptor-dependent signaling. In this review, we present the classifications of DC subsets and mechanisms involved in the alterations of DCs in sepsis, as well as further discuss the therapeutic strategies targeting DCs in sepsis to improve the aberrant immune response and prolong the life during sepsis progression.

Absence of Batf3 results in reduced liver pathology in mice infected with Schistosoma japonicum

Background

The involvement of CD8⁺T cells in schistosomiasis is being increasingly appreciated, but the underlying mechanism is not well defined.

Results

In this study, we showed that the absence of Batf3 alleviated liver damage in Batf3^−/− mice infected with S. japonicum. We found alleviated liver granulomatous inflammation in Batf3^−/− mice with schistosomiasis japonica could not be attributed to the difference in schistosome egg or worm burden. The stronger Tc1 cell responses observed in Batf3^−/− mice suggested that the deletion of Batf3 resulted in more activation of CD8⁺T cells unexpectedly during the natural infection of schistosomes. We detected a small amount of CD8α⁺ DCs in the spleen of Batf3^−/− mice at 9w post-infection. This small amount of newly generated CD8α⁺ DCs might contribute to enhanced activation of CD8⁺T cells via cross-presentation and activation which then attenuate hepatic pathological damage found in Batf3^−/− mice.

Conclusions

Our study provides evidence that Batf3 is associated with the immunoregulation of the liver granuloma formation, which may confer a new options for schistosomiasis treatment.

Lung CD103+ dendritic cells restrain allergic airway inflammation through IL-12 production

DCs are necessary and sufficient for induction of allergic airway inflammation. CD11b+ DCs direct the underlying Th2 immunity, but debate surrounds the function of CD103+ DCs in lung immunity and asthma after an allergic challenge. We challenged Batf3-/- mice, which lacked lung CD103+ DCs, with the relevant allergen house dust mite (HDM) as a model to ascertain their role in asthma. We show that acute and chronic HDM exposure leads to defective Th1 immunity in Batf3-deficient mice. In addition, chronic HDM challenge in Batf3-/- mice results in increased Th2 and Th17 immune responses and exacerbated airway inflammation. Mechanistically, Batf3 absence does not affect induction of Treg or IL-10 production by lung CD4+ T cells following acute HDM challenge. Batf3-dependent CD103+ migratory DCs are the main source of IL-12p40 in the mediastinal lymph node DC compartment in the steady state. Moreover, CD103+ DCs selectively increase their IL-12p40 production upon HDM administration. In vivo IL-12 treatment reverts exacerbated allergic airway inflammation upon chronic HDM challenge in Batf3-/- mice, restraining Th2 and Th17 responses without triggering Th1 immunity. These results suggest a protective role for lung CD103+ DCs to HDM allergic airway inflammation through the production of IL-12.

The role of basic leucine zipper transcription factor E4BP4 in the immune system and immune-mediated diseases

Basic leucine zipper transcription factor E4BP4 (also known as NFIL3) has been implicated in the molecular and cellular mechanisms of functions and activities in mammals. The interactions between E4BP4 and major regulators of cellular processes have triggered significant interest in the roles of E4BP4 in the pathogenesis of certain chronic diseases. Indeed, novel discoveries have been emerging to illustrate the involvement of E4BP4 in multiple disorders. It is recognized that E4BP4 is extensively involved in some immune-mediated diseases, but the mechanisms of E4BP4 involvement in these complex diseases remain poorly defined. Here we review the regulatory mechanisms of E4BP4 engaging in not only the biological function but also the development of immune-mediated diseases, paving the way for future therapies.