A conserved enhancer regulates Il9 expression in multiple lineages

Functional diversity and regulation of IL-9-producing T cells in cancer immunotherapy

IL-9-producing T cells (T9) regulate immunological responses that affect various cellular biological processes, though their precise function remains fully understood. Previous studies have linked T9 cells to conditions such as allergic disorders, parasitic infection clearance, and various types of cancers. While the functional heterogeneity of IL-9 and T9 cells in cancer development has been documented, these cells present promising therapeutic opportunities for treating solid tumors. This review highlights the roles of IL-9 and T9 cells in cancer progression and treatment responses, focusing on potential discrepancies in IL-9/IL-9R signaling between murine tumors and cancer patients. Additionally, we discuss the regulation of tumor-specific Th9/Tc9 cell differentiation, the therapeutic potential of these cells, and current strategies to enhance their anti-tumor activities.

TL1A priming induces a multi-cytokine Th9 cell phenotype that promotes robust allergic inflammation in murine models of asthma

Multi-cytokine-producing Th9 cells secrete IL-9 and type 2 cytokines and mediate mouse and human allergic inflammation. However, the cytokines that promote a multi-cytokine secreting phenotype have not been defined. Tumor necrosis factor superfamily member TL1A signals through its receptor DR3 to increase IL-9. Here we demonstrate that TL1A increases expression of IL-9 and IL-13 co-expressing cells in murine Th9 cell cultures, inducing a multi-cytokine phenotype. Mechanistically, this is linked to histone modifications allowing for increased accessibility at the Il9 and Il13 loci. We further show that TL1A alters the transcription factor network underlying expression of IL-9 and IL-13 in Th9 cells and increases binding of transcription factors to Il9 and Il13 loci. TL1A-priming enhances the pathogenicity of Th9 cells in murine models of allergic airway disease through the increased expression of IL-9 and IL-13. Lastly, in both chronic and memory-recall models of allergic airway disease, blockade of TL1A signaling decreases the multi-cytokine Th9 cell population and attenuates the allergic phenotype. Taken together, these data demonstrate that TL1A promotes the development of multi-cytokine Th9 cells that drive allergic airway diseases and that targeting pathogenic T helper cell-promoting cytokines could be an effective approach for modifying disease.

Locus of (IL-9) control: IL9 epigenetic regulation in cellular function and human disease

Interleukin-9 (IL-9) is a multifunctional cytokine with roles in a broad cross-section of human diseases. Like many cytokines, IL-9 is transcriptionally regulated by a group of noncoding regulatory elements (REs) surrounding the IL9 gene. These REs modulate IL-9 transcription by forming 3D loops that recruit transcriptional machinery. IL-9-promoting transcription factors (TFs) can bind REs to increase locus accessibility and permit chromatin looping, or they can be recruited to already accessible chromatin to promote transcription. Ample mechanistic and genome-wide association studies implicate this interplay between IL-9-modulating TFs and IL9 cis-REs in human physiology, homeostasis, and disease.

BNIP3 and DAPK1 methylation in peripheral blood leucocytes are noninvasive biomarkers for gastric cancer

OBJECTIVE

The objective of this study is to comprehensively investigate the potential value of BNIP3 and DAPK1 methylation in peripheral blood leukocytes as a non-invasive biomarker for the detection of gastric cancer (GC), prediction of chemotherapy efficacy, and prognosis assessment.

PATIENTS AND METHODS

Initially, multiple bioinformatic analyses were employed to explore the genetic landscape and biological effects of BNIP3 and DAPK1 in GC tissues. Subsequently, case-control and prospective follow-up studies were conducted to compare the differences in BNIP3 and DAPK1 methylation levels in peripheral blood leukocytes among GC patients and healthy controls, as well as between patients exhibiting sensitivity and resistance to platinum plus fluorouracil treatment, and between patients with varying survival outcomes of GC. Additionally, several predictive nomograms were constructed based on the identified CpG sites and relevant clinical parameters to forecast the occurrence of GC, chemotherapy efficacy, and prognosis.

RESULTS

The upregulation of BNIP3 and DAPK1 was found to be associated with the development and poorer survival outcomes of GC. Furthermore, the expression of BNIP3/DAPK1 exhibited an inverse relationship with their DNA methylation levels and demonstrated a positive correlation with immune cell infiltration, as well as the IC50 values of 5-Fluorouracil and Cisplatin in GC tissues. Increased infiltration of macrophages in the high-expression groups was observed to be linked to unfavorable GC survival. In the case-control and follow-up studies, lower methylation levels of BNIP3 and DAPK1 were identified in the peripheral leukocytes of GC patients compared to healthy controls. Hypomethylation was also associated with more aggressive subtypes, diminished chemotherapy efficacy, and poorer survival outcomes in GC.

CONCLUSION

The DNA methylation of BNIP3 and DAPK1 in peripheral blood leukocytes holds promise as a novel non-invasive biomarker for predicting the occurrence of GC, chemotherapy efficacy, and prognosis assessment.

TGF-β1 signaling and Smad7 control T-cell responses in health and immune-mediated disorders

Transforming growth factor (TGF)-β1, a member of the TGF-β superfamily, is produced by many immune and nonimmune cells and has pleiotropic effects on both innate and adaptive immunity, especially in the control of T-cell differentiation and function. Consistently, loss of TGF-β1 function is associated with exacerbated T-cell-dependent inflammatory responses that culminate in pathological processes in allergic and immune-mediated diseases. In this review, we highlight the roles of TGF-β1 in immunity, focusing mainly on its ability to promote differentiation of regulatory T cells, T helper (Th)-17, and Th9 cells, thus contributing to amplifying or restricting T-cell responses in health and human diseases (e.g., inflammatory bowel diseases, type 1 diabetes, asthma, and MS). In addition, we discuss the involvement of Smad7, an inhibitor of TGF-β1 signaling, in immune-mediated disorders (e.g., psoriasis, rheumatoid arthritis, MS, and inflammatory bowel diseases), as well as the discordant results of clinical trials with mongersen, an oral pharmaceutical compound containing a Smad7 antisense oligonucleotide, in patients with Crohn's disease. Further work is needed to ascertain the reasons for such a discrepancy as well as to identify better candidates for treatment with Smad7 inhibitors.

The World according to IL-9

Among the cytokines regulating immune cells, IL-9 has gained considerable attention for its ability to act on multiple cell types as a regulator of beneficial and pathologic immune responses. Yet, it is still not clearly defined how IL-9 impacts immune responses. IL-9 demonstrates a remarkable degree of tissue-specific functionality and has cellular sources that vary by tissue site and the context of the inflammatory milieu. Here, we provide perspective to summarize the biological activities of IL-9 and highlight cell type-specific roles in the immune pathogenesis of diseases. This perspective will be important in defining the diseases where targeting IL-9 as a therapeutic strategy would be beneficial and where it has the potential to complicate clinical outcomes.

Dynamic chromatin accessibility licenses STAT5- and STAT6-dependent innate-like function of TH9 cells to promote allergic inflammation

Allergic diseases are a major global health issue. Interleukin (IL)-9-producing helper T (TH9) cells promote allergic inflammation, yet TH9 cell effector functions are incompletely understood because their lineage instability makes them challenging to study. Here we found that resting TH9 cells produced IL-9 independently of T cell receptor (TCR) restimulation, due to STAT5- and STAT6-dependent bystander activation. This mechanism was seen in circulating cells from allergic patients and was restricted to recently activated cells. STAT5-dependent Il9/IL9 regulatory elements underwent remodeling over time, inactivating the locus. A broader 'allergic TH9' transcriptomic and epigenomic program was also unstable. In vivo, TH9 cells induced airway inflammation via TCR-independent, STAT-dependent mechanisms. In allergic patients, TH9 cell expansion was associated with responsiveness to JAK inhibitors. These findings suggest that TH9 cell instability is a negative checkpoint on bystander activation that breaks down in allergy and that JAK inhibitors should be considered for allergic patients with TH9 cell expansion.

ERG Functionally Overlaps with Other Ets Proteins in Promoting TH9 Cell Expression of Il9 during Allergic Lung Inflammation

CD4+ TH cells develop into subsets that are specialized in the secretion of particular cytokines to mediate restricted types of inflammation and immune responses. Among the subsets that promote development of allergic inflammatory responses, IL-9-producing TH9 cells are regulated by a number of transcription factors. We have previously shown that the E26 transformation-specific (Ets) family members PU.1 and Ets translocation variant 5 (ETV5) function in parallel to regulate IL-9. In this study we identified a third member of the Ets family of transcription factors, Ets-related gene (ERG), that mediates IL-9 production in TH9 cells in the absence of PU.1 and ETV5. Chromatin immunoprecipitation assays revealed that ERG interaction at the Il9 promoter region is restricted to the TH9 lineage and is sustained during murine TH9 polarization. Knockdown or knockout of ERG during murine or human TH9 polarization in vitro led to a decrease in IL-9 production in TH9 cells. Deletion of ERG in vivo had modest effects on IL-9 production in vitro or in vivo. However, in the absence of PU.1 and ETV5, ERG was required for residual IL-9 production in vitro and for IL-9 production by lung-derived CD4 T cells in a mouse model of chronic allergic airway disease. Thus, ERG contributes to IL-9 regulation in TH9 cells.

IL-9 Producing Tumor-Infiltrating Lymphocytes and Treg Subsets Drive Immune Escape of Tumor Cells in Non-Small Cell Lung Cancer

Although lung cancer is the leading cause of cancer deaths worldwide, the mechanisms how lung cancer cells evade the immune system remain incompletely understood. Here, we discovered IL-9-dependent signaling mechanisms that drive immune evasion in non-small cell lung cancer (NSCLC). We found increased IL-9 and IL-21 production by T cells in the tumoral region of the lung of patients with NSCLC, suggesting the presence of Th9 cells in the lung tumor microenvironment. Moreover, we noted IL-9 producing Tregs in NSCLC. IL-9 target cells in NSCLC consisted of IL-9R+ tumor cells and tumor-infiltrating lymphocytes. In two murine experimental models of NSCLC, and in vitro, IL-9 prevented cell death and controlled growth of lung adenocarcinoma cells. Targeted deletion of IL-9 resulted in successful lung tumor rejection in vivo associated with an induction of IL-21 and reduction of Treg cells. Finally, anti-IL-9 antibody immunotherapy resulted in suppression of tumor development even in established experimental NSCLC and was associated with reduced IL-10 production in the lung. In conclusion, our findings indicate that IL-9 drives immune escape of lung tumor cells via effects on tumor cell survival and tumor infiltrating T cells. Thus, strategies blocking IL-9 emerge as a new approach for clinical therapy of lung cancer.

Calcitriol and Retinoic acid antagonize each other to suppress the production of IL-9 by Th9 cells

Distinct T helper cells, including Th9 cells help maintain homeostasis in the immune system. Vitamins play pivotal role in the immune system through many mechanisms, including regulating the differentiation of T helper cells. Calcitriol (1,25-dihydroxyvitamin D3) and retinoic acid possess hormone-like properties and are the bioactive metabolites of vitamin D and A, respectively, that signal through heterodimers containing the common retinoid X receptor. In contrast to individual treatment with the vitamins that significantly attenuates IL-9 production from Th9 cells, Th9 cells treated with both vitamins demonstrated IL-9 production similar to untreated Th9 cells. This is associated with reciprocal expression of PU.1 and Foxp3. While the recruitment of PU.1 was significantly impaired to the Il9 gene in the presence of calcitriol or retinoic acid in Th9 cells, addition of both vitamins together increased the recruitment of PU.1 to the Il9 gene. Calcitriol and retinoic acid together impaired the recruitment of HDAC1 to the Il9 gene without impacting Gcn5 recruitment. Importantly, retinoic acid negated the effect of calcitriol and impaired the binding of VDR on the Il9 gene by dampened VDR-RXR formation. Collectively, our data show that calcitriol and retinoic acid antagonize each other to regulate the differentiation of Th9 cells.

In search of lost time: Enhancers as modulators of timing in lymphocyte development and differentiation

Proper timing of gene expression is central to lymphocyte development and differentiation. Lymphocytes often delay gene activation for hours to days after the onset of signaling components, which act on the order of seconds to minutes. Such delays play a prominent role during the intricate choreography of developmental events and during the execution of an effector response. Though a number of mechanisms are sufficient to explain timing at short timescales, it is not known how timing delays are implemented over long timescales that may span several cell generations. Based on the literature, we propose that a class of cis-regulatory elements, termed "timing enhancers," may explain how timing delays are controlled over these long timescales. By considering chromatin as a kinetic barrier to state switching, the timing enhancer model explains experimentally observed dynamics of gene expression where other models fall short. In this review, we elaborate on features of the timing enhancer model and discuss the evidence for its generality throughout development and differentiation. We then discuss potential molecular mechanisms underlying timing enhancer function. Finally, we explore recent evidence drawing connections between timing enhancers and genetic risk for immunopathology. We argue that the timing enhancer model is a useful framework for understanding how cis-regulatory elements control the central dimension of timing in lymphocyte biology.

In Activated Murine Mast Cells, NFATc2 Is Critical for the Production of Autocrine IL-3, Thereby Promoting the Expression of IL-9

IL-9 has lent its numerical designation to the Th9 subset of CD4⁺ Th cells, although it is also produced by additional cell types, including mast cells. It is a pleiotropic cytokine involved in allergic reactions, parasitic infections, autoimmune inflammation, and cancer immunity. In this article, we provide evidence that NFATc2 has contradictory functions in the expression of IL-9 in murine Th9 cells and bone marrow-derived mast cells (BMMC). The basis for this is our observation that the production of IL-9 in NFATc2-deficient Th9 cells is increased, whereas it is decreased in BMMC devoid of NFATc2. In addition, NFATc2 deficiency almost completely abrogates the expression of IL-3 in both cell types. However, selectively in BMMC, the production of IL-9 critically depends on autocrine IL-3 acting via the sustained activation of STAT5 on the expression of IL-9. Furthermore, we demonstrate that IL-3 acts independently and synergistically with IL-1β on the production of IL-9. Taken together, we highlight NFATc2-driven production of autocrine IL-3 as a critical and cell type-specific component for IL-9 expression in BMMC.

Crosstalk between the Producers and Immune Targets of IL-9

IL-9 has been reported to play dual roles in the pathogenesis of autoimmune disorders and cancers. The collaboration of IL-9 with microenvironmental factors including the broader cytokine milieu and other cellular components may provide important keys to explain its conflicting effects in chronic conditions. In this review, we summarize recent findings on the cellular sources of, and immunological responders to IL-9, in order to interpret the role of IL-9 in the regulation of immune responses. This knowledge will provide new perspectives to improve clinical benefits and limit adverse effects of IL-9 when treating pathologic conditions.

STAT5 promotes accessibility and is required for BATF-mediated plasticity at the Il9 locus

T helper cell differentiation requires lineage-defining transcription factors and factors that have shared expression among multiple subsets. BATF is required for development of multiple Th subsets but functions in a lineage-specific manner. BATF is required for IL-9 production in Th9 cells but in contrast to its function as a pioneer factor in Th17 cells, BATF is neither sufficient nor required for accessibility at the Il9 locus. Here we show that STAT5 is the earliest factor binding and remodeling the Il9 locus to allow BATF binding in both mouse and human Th9 cultures. The ability of STAT5 to mediate accessibility for BATF is observed in other Th lineages and allows acquisition of the IL-9-secreting phenotype. STAT5 and BATF convert Th17 cells into cells that mediate IL-9-dependent effects in allergic airway inflammation and anti-tumor immunity. Thus, BATF requires the STAT5 signal to mediate plasticity at the Il9 locus.

BATF is a transcription factor that is needed for IL-9 production by T helper 9 cells. Here the authors show that STAT5 is needed at the Il9 locus to enable BATF to function in this manner and that this interaction can reprogram other T helper subsets into IL-9 producing cells, thus regulating the immune response to disease.

Expression Efficiency of Multiple Il9 Reporter Alleles Is Determined by Cell Lineage

Generation of allelic gene reporter mice has provided a powerful tool to study gene function in vivo. In conjunction with imaging technologies, reporter mouse models facilitate studies of cell lineage tracing, live cell imaging, and gene expression in the context of diseases. Although there are several advantages to using reporter mice, caution is important to ensure the fidelity of the reporter protein representing the gene of interest. In this study, we compared the efficiency of two Il9 reporter strains Il9^citrine and Il9^GFP in representing IL-9-producing CD4⁺ T_H9 cells. Although both alleles show high specificity in IL-9-expressing populations, we observed that the Il9^GFP allele visualized a much larger proportion of the IL-9-producing cells in culture than the Il9^citrine reporter allele. In defining the mechanistic basis for these differences, chromatin immunoprecipitation and chromatin accessibility assay showed that the Il9^citrine allele was transcriptionally less active in T_H9 cells compared with the wild-type allele. The Il9^citrine allele also only captured a fraction of IL-9-expressing bone marrow-derived mast cells. In contrast, the Il9 ^citrine reporter detected Il9 expression in type 2 innate lymphoid cells at a greater percentage than could be identified by IL-9 intracellular cytokine staining. Taken together, our findings demonstrate that the accuracy of IL-9 reporter mouse models may vary with the cell type being examined. These studies demonstrate the importance of choosing appropriate reporter mouse models that are optimal for detecting the cell type of interest as well as the accuracy of conclusions.

The protective effect of the TSPO ligands 2,4-Di-Cl-MGV-1, CB86, and CB204 against LPS-induced M1 pro-inflammatory activation of microglia

We have shown previously, that the 18 ​kDa translocator protein (TSPO) synthetic ligands quinazoline derivatives (2-Cl-MGV-1 and MGV-1) can inhibit activation of in BV-2 microglial cells. In the present study we assessed the impact of novel TSPO ligands on lipopolysaccharide (LPS)-induced microglial activation as expressed by release of pro-inflammatory molecules, including cytokines [interleukin-6 (IL-6), IL-1β, interferon- γ (IFN-γ)] nitric oxide (NO), CD8, and cyclo-oxygenase-2 (COX-2). The TSPO ligands 2,4-Di-Cl-MGV-1, CB86, and CB204 counteracted with the LPS-induced microglial activation. Exposure to LPS along with the TSPO ligand 2,4-Di-Cl-MGV-1 (25 ​μM) reduced significantly the release of NO by 24-, IL-6 by 14-, IL-β by 14-, IFN- γ by 6-, and TNF-α by 29-folds, respectively. In contrast to the anti-neuroinflammatory effect of the TSPO ligands, the effect of diclofenac sodium (DS; 25 ​μM) did not reach statistical significance. No alterations in IL-10 and IL-13 were detected (M2 anti-inflammatory pathway) during the inhibition of M1 pro-inflammatory pathway.

IL-9 and IL-9-producing cells in tumor immunity

Abstract

Interleukin (IL)-9 belongs to the IL-2Rγc chain family and is a multifunctional cytokine that can regulate the function of many kinds of cells. It was originally identified as a growth factor of T cells and mast cells. In previous studies, IL-9 was mainly involved in the development of allergic diseases, autoimmune diseases and parasite infections. Recently, IL-9, as a double-edged sword in the development of cancers, has attracted extensive attention. Since T-helper 9 (Th9) cell-derived IL-9 was verified to play a powerful antitumor role in solid tumors, an increasing number of researchers have started to pay attention to the role of IL-9-skewed CD8⁺ T (Tc9) cells, mast cells and Vδ2 T cell-derived IL-9 in tumor immunity. Here, we review recent studies on IL-9 and several kinds of IL-9-producing cells in tumor immunity to provide useful insight into tumorigenesis and treatment.

Calcitriol Regulates the Differentiation of IL-9-Secreting Th9 Cells by Modulating the Transcription Factor PU.1

Vitamin D can modulate the innate and adaptive immune system. Vitamin D deficiency has been associated with various autoimmune diseases. Th9 cells are implicated in the pathogenesis of numerous autoimmune diseases. Thus, we investigated the role of calcitriol (active metabolite of vitamin D) in the regulation of Th9 cell differentiation. In this study, we have unraveled the molecular mechanisms of calcitriol-mediated regulation of Th9 cell differentiation. Calcitriol significantly diminished IL-9 secretion from murine Th9 cells associated with downregulated expression of the Th9-associated transcription factor, PU.1. Ectopic expression of VDR in Th9 cells attenuated the percentage of IL-9-secreting cells. VDR associated with PU.1 in Th9 cells. Using a series of mutations, we were able to dissect the VDR domain involved in the regulation of the Il9 gene. The VDR-PU.1 interaction prevented the accessibility of PU.1 to the Il9 gene promoter, thereby restricting its expression. However, the expression of Foxp3, regulatory T cell-specific transcription factor, was enhanced in the presence of calcitriol in Th9 cells. When Th9 cells are treated with both calcitriol and trichostatin A (histone deacetylase inhibitor), the level of IL-9 reached to the level of wild-type untreated Th9 cells. Calcitriol attenuated specific histone acetylation at the Il9 gene. In contrast, calcitriol enhanced the recruitment of the histone modifier HDAC1 at the Il9 gene promoter. In summary, we have identified that calcitriol blocked the access of PU.1 to the Il9 gene by reducing its expression and associating with it as well as regulated the chromatin of the Il9 gene to regulate expression.

BATF-Interacting Proteins Dictate Specificity in Th Subset Activity

The basic leucine zipper (bZIP) transcription factor BATF is expressed in multiple Th subsets and cooperates with other factors to regulate gene transcription. BATF activates lineage-specific cytokines in Th subsets, activating IL-9 in Th9 cells and IL-17 in Th17 cells, but not IL-9 or IL-17 in the reciprocal subset. The mechanism for this restricted activity is unclear. In this report, we define BATF binding partners that contribute to Th subset-specific functions. Although BATF and IRF4 are expressed in greater amounts in Th9 than Th17, increased expression of both factors is not sufficient to induce IL-9 in Th17 cells. BATF also requires heterodimer formation with Jun family members to bind DNA and induce gene expression. Using primary mouse T cell culture, we observed that JunB and c-Jun, but not JunD, promote IL-9 production in Th9 cells. Ectopic expression of BATF with either JunB or c-Jun generates modest, but significant, increases in IL-9 production in Th17 cells, suggesting that the low expression of Jun family members is one factor limiting the ability of BATF to induce IL-9 in Th17 cells. We further identified that Bach2 positively regulates IL-9 production by directly binding to the Il9 gene and by increasing transcription factor expression in Th9 cells. Strikingly, cotransduction of Bach2 and BATF significantly induces IL-9 production in both Th9 and Th17 cells. Taken together, our results reveal that JunB, c-Jun, and Bach2 cooperate with BATF to contribute to the specificity of BATF-dependent cytokine induction in Th subsets.

The γc Family of Cytokines: Basic Biology to Therapeutic Ramifications

The common cytokine receptor γ chain, γ_c, is a component of the receptors for interleukin-2 (IL-2), IL-4, IL-7, IL-9, IL-15, and IL-21. Mutation of the gene encoding γ_c results in X-linked severe combined immunodeficiency in humans, and γ_c family cytokines collectively regulate development, proliferation, survival, and differentiation of immune cells. Here, we review the basic biology of these cytokines, highlighting mechanisms of signaling and gene regulation that have provided insights for immunodeficiency, autoimmunity, allergic diseases, and cancer. Moreover, we discuss how studies of this family stimulated the development of JAK3 inhibitors and present an overview of current strategies targeting these pathways in the clinic, including novel antibodies, antagonists, and partial agonists. The diverse roles of these cytokines on a range of immune cells have important therapeutic implications.

The Il9 CNS-25 Regulatory Element Controls Mast Cell and Basophil IL-9 Production

IL-9 is an important mediator of allergic disease that is critical for mast cell-driven diseases. IL-9 is produced by many cell types, including T cells, basophils, and mast cells. Yet, how IL-9 is regulated in mast cells or basophils is not well characterized. In this report, we tested the effects of deficiency of a mouse Il9 gene regulatory element (Il9 CNS-25) in these cells in vivo and in vitro. In mast cells stimulated with IL-3 and IL-33, the Il9 CNS-25 enhancer is a potent regulator of mast cell Il9 gene transcription and epigenetic modification at the Il9 locus. Our data show preferential binding of STAT5 and GATA1 to CNS-25 over the Il9 promoter in mast cells and that T cells and mast cells have differing requirements for the induction of IL-9 production. Il9 CNS-25 is required for IL-9 production from T cells, basophils, and mast cells in a food allergy model, and deficiency in IL-9 expression results in decreased mast cell expansion. In a Nippostrongylus brasiliensis infection model, we observed a similar decrease in mast cell accumulation. Although decreased mast cells correlated with higher parasite egg burden and delayed clearance in vivo, T cell deficiency in IL-9 also likely contributes to the phenotype. Thus, our data demonstrate IL-9 production in mast cells and basophils in vivo requires Il9 CNS-25, and that Il9 CNS-25-dependent IL-9 production is required for mast cell expansion during allergic intestinal inflammation.

Transcription factor networks in aged naïve CD4 T cells bias lineage differentiation

With reduced thymic activity, the population of naïve T cells in humans is maintained by homeostatic proliferation throughout adult life. In young adults, naïve CD4 T cells have enormous proliferative potential and plasticity to differentiate into different lineages. Here, we explored whether naïve CD4 T-cell aging is associated with a partial loss of this unbiased multipotency. We find that naïve CD4 T cells from older individuals have developed a propensity to develop into TH9 cells. Two major mechanisms contribute to this predisposition. First, responsiveness to transforming growth factor β (TGFβ) stimulation is enhanced with age due to an upregulation of the TGFβR3 receptor that results in increased expression of the transcription factor PU.1. Secondly, aged naïve CD4 T cells display altered transcription factor profiles in response to T-cell receptor stimulation, including enhanced expression of BATF and IRF4 and reduced expression of ID3 and BCL6. These transcription factors are involved in TH9 differentiation as well as IL9 transcription suggesting that the aging-associated changes in the transcription factor profile favor TH9 commitment.

Shaping the diversity of Th2 cell responses in epithelial tissues and its potential for allergy treatment

Th2 cells have evolved to protect from large helminth infections and to exert tissue protective functions in response to nonmicrobial noxious stimuli. The initiation, maintenance, and execution of these functions depend on the integration of diverse polarizing cues by cellular sensors and molecular programs as well as the collaboration with cells that are coopted for signal exchange. The complexity of input signals and cellular collaboration generates tissue specific Th2 cell heterogeneity and specialization. In this review, we aim to discuss the advances and recent breakthroughs in our understanding of Th2 cell responses and highlight developmental and functional differences among T cells within the diversifying field of type 2 immunity. We will focus on factors provided by the tissue microenvironment and highlight factors with potential implications for the pathogenesis of allergic skin and lung diseases. Especially new insights into the role of immunometabolism, the microbiota and ionic signals enhance the complexity of Th2 cell regulation and warrant a critical evaluation. Finally, we will discuss how this ensemble of established knowledge and recent breakthroughs about Th2 immunobiology advance our understanding of the pathogenesis of allergic diseases and how this could be exploited for future immunotherapies.

Retinoic Acid Receptor Alpha Represses a Th9 Transcriptional and Epigenomic Program to Reduce Allergic Pathology

CD4⁺ T helper (Th) differentiation is regulated by diverse inputs, including the vitamin A metabolite retinoic acid (RA). RA acts through its receptor RARα to repress transcription of inflammatory cytokines, but is also essential for Th-mediated immunity, indicating complex effects of RA on Th specification and the outcome of the immune response. We examined the impact of RA on the genome-wide transcriptional response during Th differentiation to multiple subsets. RA effects were subset-selective and were most significant in Th9 cells. RA globally antagonized Th9-promoting transcription factors and inhibited Th9 differentiation. RA directly targeted the extended Il9 locus and broadly modified the Th9 epigenome through RARα. RA-RARα activity limited murine Th9-associated pulmonary inflammation, and human allergic inflammation was associated with reduced expression of RA target genes. Thus, repression of the Th9 program is a major function of RA-RARα signaling in Th differentiation, arguing for a role for RA in interleukin 9 (IL-9) related diseases.

CBP/p300 Drives the Differentiation of Regulatory T Cells through Transcriptional and Non-Transcriptional Mechanisms

Regulatory T cells (Treg) are immunosuppressive and negatively impact response to cancer immunotherapies. CREB-binding protein (CBP) and p300 are closely related acetyltransferases and transcriptional coactivators. Here, we evaluate the mechanisms by which CBP/p300 regulate Treg differentiation and the consequences of CBP/p300 loss-of-function mutations in follicular lymphoma. Transcriptional and epigenetic profiling identified a cascade of transcription factors essential for Treg differentiation. Mass spectrometry analysis showed that CBP/p300 acetylates prostacyclin synthase, which regulates Treg differentiation by altering proinflammatory cytokine secretion by T and B cells. Reduced Treg presence in tissues harboring CBP/p300 loss-of-function mutations was observed in follicular lymphoma. Our findings provide novel insights into the regulation of Treg differentiation by CBP/p300, with potential clinical implications on alteration of the immune landscape. SIGNIFICANCE: This study provides insights into the dynamic role of CBP/p300 in the differentiation of Tregs, with potential clinical implications in the alteration of the immune landscape in follicular lymphoma.

Th9 Cells in Allergic Disease

PURPOSES OF REVIEW

Th9 cells are recognized as a novel subset of effector T helper cells that preferentially produce IL-9. Here, we provide a current update on the reports related to the function of Th9 cells in allergic inflammatory diseases.

RECENT FINDINGS

The effector Th9 cells differentiating from naïve T helper cells have recently been identified. Because of accumulating findings of Th9 cells in many inflammatory diseases, including allergic diseases, diverse functions of Th9 cells in regulating immune responses have been suggested. Related reports indicate multiple sources of IL-9 besides Th9 cells and their association with the pathogenesis of allergic rhinitis, asthma, atopic dermatitis, contact dermatitis, and food allergy. More recently, elements of the epigenetic landscape involving in the regulation of IL-9 by Th9 cells have been identified to be the potential target for allergic inflammation. This review provides the most recent information about Th9 cells and their contribution in airway allergic disease, skin, and food allergy.