Uncoupling of macrophage inflammation from self-renewal modulates host recovery from respiratory viral infection

Tissue macrophages self-renew during homeostasis and produce inflammatory mediators upon microbial infection. We examined the relationship between proliferative and inflammatory properties of tissue macrophages by defining the impact of the Wnt/β-catenin pathway, a central regulator of self-renewal, in alveolar macrophages (AMs). Activation of β-catenin by Wnt ligand inhibited AM proliferation and stemness, but promoted inflammatory activity. In a murine influenza viral pneumonia model, β-catenin-mediated AM inflammatory activity promoted acute host morbidity; in contrast, AM proliferation enabled repopulation of reparative AMs and tissue recovery following viral clearance. Mechanistically, Wnt treatment promoted β-catenin-HIF-1α interaction and glycolysis-dependent inflammation while suppressing mitochondrial metabolism and thereby, AM proliferation. Differential HIF-1α activities distinguished proliferative and inflammatory AMs in vivo. This β-catenin-HIF-1α axis was conserved in human AMs and enhanced HIF-1α expression associated with macrophage inflammation in COVID-19 patients. Thus, inflammatory and reparative activities of lung macrophages are regulated by β-catenin-HIF-1α signaling, with implications for the treatment of severe respiratory diseases.

Transcription Factors in the Development and Pro-Allergic Function of Mast Cells

Mast cells (MCs) are innate immune cells of hematopoietic origin localized in the mucosal tissues of the body and are broadly implicated in the pathogenesis of allergic inflammation. Transcription factors have a pivotal role in the development and differentiation of mast cells in response to various microenvironmental signals encountered in the resident tissues. Understanding the regulation of mast cells by transcription factors is therefore vital for mechanistic insights into allergic diseases. In this review we summarize advances in defining the transcription factors that impact the development of mast cells throughout the body and in specific tissues, and factors that are involved in responding to the extracellular milieu. We will further describe the complex networks of transcription factors that impact mast cell physiology and expansion during allergic inflammation and functions from degranulation to cytokine secretion. As our understanding of the heterogeneity of mast cells becomes more detailed, the contribution of specific transcription factors in mast cell-dependent functions will potentially offer new pathways for therapeutic targeting.

Generation of mice with a conditional Il9 allele

Interleukin (IL)-9 is a pleotropic cytokine that induces cell-specific functions associated with asthma, with target cells including T cells, mast cells, eosinophils, and epithelial cells. Previous findings have demonstrated that IL-9 promotes mast cell growth and differentiation, suggesting that IL-9 contributes to mast cell-driven allergic diseases. Although studies have demonstrated the impact of IL-9 in allergic asthma and other allergic diseases, the cellular source of IL-9 in each setting remains unclear. IL-9 can be produced by several cell types including natural killer T cells, innate lymphoid cells, mast cells, and CD4+ T helper cells (Th). We speculate that T helper 9 (Th9) cells are a major source of IL-9 and that Th9-dervied IL-9 promotes mast cell expansion, activity, and function. Our hypothesis is supported by findings in patients with asthma in which IL-9 expression and Th9 cell numbers are significantly elevated. Here, we address the role of T cell–derived IL-9 in mice with an inactivation of the IL-9 gene restricted to T cells generated by CD4-Cre/loxP-mediated targeting of the IL-9 gene. Preliminary results demonstrate efficient deletion of Il9 in T cells. Il9 fl/fl CD4-Cre Th9 cultures have minimal production of IL-9. Ongoing studies will directly examine the contribution and function of TH9-derived IL-9 during models of allergic airway inflammation and future studies will define the requirement for IL-9 in other cell populations during allergic immune responses.

STAT4 in Conventional Dendritic Cells Regulates Pathogenic T Cell Differentiation and Inflammation in Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) is an inflammatory demyelinating disease affecting the central nervous system (CNS). Signal transducer and activator of transcription 4 (STAT4) is a major regulator of inflammatory in protective immunity and autoimmunity. STAT4 is activated downstream of two cytokines known to mediate the pathogenic T cell differentiation in autoimmune diseases, IL-12 and IL-23. In experimental autoimmune encephalomyelitis (EAE), an animal model of MS, germ-line deletion of STAT4 in mice results in resistance to the development of EAE. In this study, we investigated the contribution of innate myeloid cells to the phenotype observed in STAT4−/− mice in EAE. Using conditional mutant mice, we immunized mice deficient in STAT4 in myeloid cells and found that mice deficient in STAT4 in CD11c+ cells, but not Lyz2 + cells, are resistant to disease. STAT4fl/flCD11cCre mice are resistant to EAE induction and have inefficient differentiation of the pathogenic IL-17A, GM-CSF, and IFN-γ secreting CD4+ T cells. More importantly, STAT4fl/flCD11cCre mice have a significant decrease of migrated MHCIIhigh+ CD11chigh+CD26+ conventional dendritic cells (cDCs) to the CNS, suggesting a critical role of STAT4 on cDC migration to the CNS. Overall, our results identify a functional requirement of STAT4 in cDCs during EAE induction and propose a potential therapeutic target for autoimmune neuroinflammation diseases.

IL-9 regulates type-2 CD4 tissue resident memory cell mediated allergic airway recall responses

Allergic asthma is a chronic inflammatory lung disease with intermittent flares where patients experience symptoms mediated by memory T cells. Allergen-specific CD4+ tissue resistant memory (Trm) cells in peripheral tissues have been reported to facilitate mucosal barrier immunity. However, the precise role of Trm CD4+ T cells in allergic exacerbations is not clearly defined. In this study we identified interleukin-9 (IL-9)-secreting allergen-specific CD4 T cells with a memory phenotype that regulate recall response to Aspergillus fumigatus. Inhibition of circulating T cells by administering FTY720 in the last month of rest, diminished the total CD4 T cells population in the lung, while the IL-9 secreting CD4 tissue resident cells remained stable. Single-cell RNA-seq and ATAC-seq confirmed the presence of multi-cytokine producing IL-9 secreting CD4 Trms in early recall responses to the allergen. Blockade of IL-9 prior to recall challenge phase reduced overall allergic lung inflammation observed through both flow-cytometry and single cell-RNA-seq analysis. IL-9 neutralization reduced cellularity of several populations in the lung including granulocytes and lymphocytes. Moreover, the expression of genes associated with mucus metaplasia including Muc2, Muc5ac, Muc5b, and Bpifb1 were significantly reduced in type-2 alveolar and epithelial cells with anti-IL-9 treatment. These findings demonstrate that IL-9-producing Trms play an important role in mediating allergic memory responses. IL-9 could be a promising therapeutic target specifically in patients showing symptoms of intermittent allergic response.

BATF Regulates T Regulatory Cell Functional Specification and Fitness of Triglyceride Metabolism in Restraining Allergic Responses

Preserving appropriate function and metabolism in regulatory T (Treg) cells is crucial for controlling immune tolerance and inflammatory responses. Yet how Treg cells coordinate cellular metabolic programs to support their functional specification remains elusive. In this study, we report that BATF couples the T_H2-suppressive function and triglyceride (TG) metabolism in Treg cells for controlling allergic airway inflammation and IgE responses. Mice with Treg-specific ablation of BATF developed an inflammatory disorder characterized by T_H2-type dominant responses and were predisposed to house dust mite-induced airway inflammation. Loss of BATF enabled Treg cells to acquire T_H2 cell-like characteristics. Moreover, BATF-deficient Treg cells displayed elevated levels of cellular TGs, and repressing or elevating TGs, respectively, restored or exacerbated their defects. Mechanistically, TCR/CD28 costimulation enhanced expression and function of BATF, which sustained IRF4 activity to preserve Treg cell functionality. Thus, our studies reveal that BATF links Treg cell functional specification and fitness of cellular TGs to control allergic responses, and suggest that therapeutic targeting of TG metabolism could be used for the treatment of allergic disease.

STAT4 Is Largely Dispensable for Systemic Lupus Erythematosus-like Autoimmune- and Foreign Antigen-Driven Antibody-Forming Cell, Germinal Center, and Follicular Th Cell Responses

Genome-wide association studies identified variants in the transcription factor STAT4 gene and several other genes in the STAT4 signaling pathway, such as IL12A, IL12B, JAK2, and TYK2, which are associated with an increased risk of developing systemic lupus erythematosus (SLE) and other autoimmune diseases. Consistent with the genome-wide association studies data, STAT4 was shown to play an important role in autoimmune responses and autoimmunity development in SLE mouse models. Despite such important role for STAT4 in SLE development in mice and humans, little is known whether and how STAT4 may regulate extrafollicular Ab-forming cell (AFC) and follicular germinal center (GC) responses, two major pathways of autoreactive B cell development and autoantibody production. To our surprise, we found STAT4 to be largely dispensable for promoting autoimmune AFC and GC responses in various autoimmune- and SLE-prone mouse models, which strongly correlated with autoantibody production, and immune complex deposition and immune cell infiltration in the kidney. We further observed that STAT4 deficiency had no effects on AFC, GC, and Ag-specific Ab responses during protein Ag immunization or influenza virus infection. Additionally, CD4+ effector and follicular Th cell responses in autoimmune- and SLE-prone mice and protein Ag-immunized and influenza virus-infected mice were intact in the absence of STAT4. Together, our data demonstrate a largely dispensable role for STAT4 in AFC, GC, and Ab responses in SLE mouse models and in certain foreign Ag-driven responses.

Tissue-resident CD4+ T helper cells assist the development of protective respiratory B and CD8+ T cell memory responses

Much remains unknown about the roles of CD4⁺ T helper cells in shaping localized memory B cell and CD8⁺ T cell immunity in the mucosal tissues. Here, we report that lung T helper cells provide local assistance for the optimal development of tissue-resident memory B and CD8⁺ T cells after the resolution of primary influenza virus infection. We have identified a population of T cells in the lung that exhibit characteristics of both follicular T helper and T_RM cells, and we have termed these cells as resident helper T (T_RH) cells. Optimal T_RH cell formation was dependent on transcription factors involved in T follicular helper and resident memory T cell development including BCL6 and Bhlhe40. We show that T_RH cells deliver local help to CD8⁺ T cells through IL-21-dependent mechanisms. Our data have uncovered the presence of a tissue-resident helper T cell population in the lung that plays a critical role in promoting the development of protective B cell and CD8⁺ T cell responses.

Helminth-induced regulation of T-cell transfer colitis requires intact and regulated T cell Stat6 signaling in mice

Infection with parasitic worms (helminths) alters host immune responses and can inhibit pathogenic inflammation. Helminth infection promotes a strong Th2 and T regulatory response while suppressing Th1 and Th17 function. Th2 responses are largely dependent on transcriptional programs directed by Stat6-signaling. We examined the importance of intact T cell Stat6 signaling on helminth-induced suppression of murine colitis that results from T cell transfer into immune-deficient mice. Colonization with the intestinal nematode Heligmosomoides polygyrus bakeri resolves WT T cell transfer colitis. However, if the transferred T cells lack intact Stat6 then helminth exposure failed to attenuate colitis or suppress MLN T cell IFN-γ or IL17 production. Loss of Stat6 signaling resulted in decreased IL10 and increased IFN-γ co-expression by IL-17⁺ T cells. We also transferred T cells from mice with constitutive T cell expression of activated Stat6 (Stat6VT). These mice developed a severe eosinophilic colitis that also was not attenuated by helminth infection. These results show that T cell expression of intact but regulated Stat6 signaling is required for helminth infection-associated regulation of pathogenic intestinal inflammation.

Granzyme A-producing T helper cells are critical for acute graft-versus-host disease

Acute graft-versus-host disease (aGVHD) can occur after hematopoietic cell transplant in patients undergoing treatment for hematological malignancies or inborn errors. Although CD4+ T helper (Th) cells play a major role in aGVHD, the mechanisms by which they contribute, particularly within the intestines, have remained elusive. We have identified a potentially novel subset of Th cells that accumulated in the intestines and produced the serine protease granzyme A (GrA). GrA+ Th cells were distinct from other Th lineages and exhibited a noncytolytic phenotype. In vitro, GrA+ Th cells differentiated in the presence of IL-4, IL-6, and IL-21 and were transcriptionally unique from cells cultured with either IL-4 or the IL-6/IL-21 combination alone. In vivo, both STAT3 and STAT6 were required for GrA+ Th cell differentiation and played roles in maintenance of the lineage identity. Importantly, GrA+ Th cells promoted aGVHD-associated morbidity and mortality and contributed to crypt destruction within intestines but were not required for the beneficial graft-versus-leukemia effect. Our data indicate that GrA+ Th cells represent a distinct Th subset and are critical mediators of aGVHD.

Toxoplasma gondii Co-opts the Unfolded Protein Response To Enhance Migration and Dissemination of Infected Host Cells

Toxoplasma gondii is an intracellular parasite that reconfigures its host cell to promote pathogenesis. One consequence of Toxoplasma parasitism is increased migratory activity of host cells, which facilitates dissemination. Here, we show that Toxoplasma triggers the unfolded protein response (UPR) in host cells through calcium release from the endoplasmic reticulum (ER). We further identify a novel role for the host ER stress sensor protein IRE1 in Toxoplasma pathogenesis. Upon infection, Toxoplasma activates IRE1, engaging its noncanonical role in actin remodeling through the binding of filamin A. By inducing cytoskeletal remodeling via IRE1 oligomerization in host cells, Toxoplasma enhances host cell migration in vitro and dissemination of the parasite to host organs in vivo Our study has identified novel mechanisms used by Toxoplasma to induce dissemination of infected cells, providing new insights into strategies for treatment of toxoplasmosis.IMPORTANCE Cells that are infected with the parasite Toxoplasma gondii exhibit heightened migratory activity, which facilitates dissemination of the infection throughout the body. In this report, we identify a new mechanism used by Toxoplasma to hijack its host cell and increase its mobility. We further show that the ability of Toxoplasma to increase host cell migration involves not the enzymatic activity of IRE1 but rather IRE1 engagement with actin cytoskeletal remodeling. Depletion of IRE1 from infected host cells reduces their migration in vitro and significantly hinders dissemination of Toxoplasma in vivo Our findings reveal a new mechanism underlying host-pathogen interactions, demonstrating how host cells are co-opted to spread a persistent infection around the body.

T follicular regulatory cells and IL-10 promote food antigen-specific IgE

Food allergies are a major clinical problem and are driven by IgE antibodies (Abs) specific for food antigens (Ags). T follicular regulatory (Tfr) cells are a specialized subset of FOXP3+ T cells that modulate Ab responses. Here, we analyzed the role of Tfr cells in regulating Ag-specific IgE using a peanut-based food allergy model in mice. Peanut-specific IgE titers and anaphylaxis responses were significantly blunted in Tfr cell-deficient Foxp3-Cre Bcl6fl/fl mice. Loss of Tfr cells led to greatly increased nonspecific IgE levels, showing that Tfr cells have both helper and suppressor functions in IgE production in the germinal center (GC) that work together to facilitate the production of Ag-specific IgE. Foxp3-Cre Ptenfl/fl mice with augmented Tfr cell responses had markedly higher levels of peanut-specific IgE, revealing an active helper function by Tfr cells on Ag-specific IgE. The helper function of Tfr cells for IgE production involves IL-10, and the loss of IL-10 signaling by B cells led to a severely curtailed peanut-specific IgE response, decreased GCB cell survival, and loss of GC dark zone B cells after peanut sensitization. We thus reveal that Tfr cells have an unexpected helper role in promoting food allergy and may represent a target for drug development.

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.

PD-1hi CD8+ resident memory T cells balance immunity and fibrotic sequelae

CD8⁺ tissue-resident memory T (T_RM) cells provide frontline immunity in mucosal tissues. The mechanisms regulating CD8⁺ T_RM maintenance, heterogeneity, and protective and pathological functions are largely elusive. Here, we identify a population of CD8⁺ T_RM cells that is maintained by major histocompatibility complex class I (MHC-I) signaling, and CD80 and CD86 costimulation after acute influenza infection. These T_RM cells have both exhausted-like phenotypes and memory features and provide heterologous immunity against secondary infection. PD-L1 blockade after the resolution of primary infection promotes the rejuvenation of these exhausted-like T_RM cells, restoring protective immunity at the cost of promoting postinfection inflammatory and fibrotic sequelae. Thus, PD-1 serves to limit the pathogenic capacity of exhausted-like T_RM cells at the memory phase. Our data indicate that T_RM cell exhaustion is the result of a tissue-specific cellular adaptation that balances fibrotic sequelae with protective immunity.

Identification of splice isoforms in T helper cells using Nanopore-based cDNA sequencing

The T helper (Th) cell compartment of the adaptive immune response provides a central mechanism of balance between inflammation and immune tolerance. The differentiation of naïve Th cells into both regulatory and effector Th subsets is regulated through complex gene regulatory networks that lead to distinct transcriptomes. Alternative RNA splicing is a major component of cellular differentiation that allows protein heterogeneity and mechanistic diversity across cell types. However, our understanding of alternative splicing control is still limited. Here we show differential expression of RNA binding Proteins (RBP) genes among Th cell subsets suggesting a regulatory role of RBPs in RNA splicing and Th differentiation. In order to interrogate the regulatory gene network, we utilized innovative Nanopore-based sequencing to generate a single molecule transcriptome map of naïve CD4 T cells, and differentiated Treg and Th1 cells to characterize full-length cDNA transcripts and alternatively spliced isoforms. Gene expression was compared across four major gene categories; RBPs, Transcription Factors (TFs), Other Protein Coding (OPC) and LncRNA. Our study revealed that RBPs exhibited high splicing potential while LncRNA exhibited relatively less splicing potential in comparison to other gene categories in all cell types. Overall, we identify RBPs that are both differentially expressed in Th subsets and differentially spliced themselves. This might represent an important control mechanism of functional protein diversity in regulating immune responses.

IL-9 Represses Intestinal Granzyme A Positive CD4 T Cells in Mice with Allergic Airway Inflammation

Mediated by immune responses in the airways, symptoms of allergic airway diseases include shortness of breath, difficulty breathing, and wheezing. Responses in distant tissues, such as increased lymphocyte proliferation and cytokine secretion, are also exhibited. How airway sensitization mediates these distant effects is unclear. We recently described the development and function of granzyme A-expressing T cells that control intestinal inflammation. Using models of chronic and memory allergic airway inflammation, we now show that a granzyme A expressing CD4 T cell population in the intestine increases during these diseases. This response is amplified in mice that lack IL-9 signaling through a deficiency in IL-9 receptor levels (IL9RKO) or receive an IL-9 antibody blockade. In a chronic intranasal allergen challenge model, we saw elevated levels of granzyme A expressing CD4 T cells in IL9RKO mice when compared to wild-type controls. In a memory internasal allergen model using wild-type mice (chronic allergen exposure, followed by an allergen-free rest period, and an allergen re-exposure), granzyme A expressing cells in the intestine were increased upon IL-9 antibody blockade. Blocking IL-9 or administering IL-9 to naïve mice or cell cultures that generate granzyme A expressing T cells did not affect cell prevalence. Therefore, concurrent allergic airway inflammation seems to be required for the proliferation of these granzyme A expressing T cells. Together, these studies suggest that allergic airway inflammation increases granzyme A expressing CD4 T cells in the intestine and that IL-9 attenuates this effect. Moreover, these results show that allergic airway inflammation impacts immunity at a distant mucosal site.

STAT4 promotes critical neutrophil functions and is required for antimicrobial immunity in mice

Signal transducer and activator of transcription 4 (STAT4) is a transcription factor mainly associated with Th1 development, yet its role in neutrophil biology is unknown. We are the first to demonstrate that in vitro murine neutrophils stimulated with IL-12 directly activate STAT4 in a JAK2-dependent manner resulting in distinct transcriptional changes in antimicrobial response genes. STAT4-deficiency also impairs several neutrophil functions in vitro. Interestingly, IL-12 directly induces STAT4-dependent ROS formation at 14 hours, which is not due to cell death. Neutrophil extracellular trap (NET) formation in response to either LPS or heat-killed Pseudomonas aeruginosa results in decreased nuclear translocation of myeloperoxidase, decreased neutrophil elastase release, and decreased DNA release in STAT4-deficient neutrophils. In vivo neutrophil migration to the peritoneal cavity is blunted in Stat4−/− mice following either thioglycollate, CXCL1, or GM-CSF injections. Finally, we have generated Stat4floxLysMCre and Stat4floxS100A8Cre mice which are deficient in STAT4 in either myeloid cells or specifically neutrophils, respectively. Following in vivo infection with methicillin-resistant S. aureus, bacterial burden is increased in the blood and peritoneal cavity of Stat4floxLysMCre and Stat4floxS100A8Cre mice. Gene expression analysis of peritoneal exudate cells from infected mice show decreased expression of Ly6G/CD11b, further highlighting defective homing of Stat4−/− neutrophils in vivo. All together these data reveal an undiscovered role of STAT4 in neutrophil functions and a subsequent role of STAT4 in innate immunity and antimicrobial defense mechanisms.

Biomarker prediction of pediatric atopic dermatitis severity

Atopic dermatitis (AD) is a chronic inflammatory skin disease that affects 25% of children and 1–3% of adults worldwide, and has increased 2- to 3-fold over the past several decades. The pathogenesis of AD may result from complex interactions between environmental and genetic factors, barrier defects and immune dysregulation resulting in epidermal hyperplasia and increased penetration of allergens and microbial pathogens. Although most cases of AD are transient, and AD is often thought of as the first step of the atopic march, some AD patients have active disease throughout life. In this study, we analyzed a population of infants that were at high risk for atopic disease and sampled serum, analyzed peripheral blood mononuclear cells, and clinical parameters upon entry (mean age 10.3 months) and five years later. We tested 161 serum analytes using a combination of single-plex, multiplex, Olink, and Quanterix assays. Broadly, the concentration of many analytes fell over time, while SDF and sCD40L concentration increased at the later time point. Several analytes correlated with AD severity as assessed by SCORAD, and most significantly, IL-13 and MCP-4 correlated with SCORAD at both time points. Subsets of cytokines were significantly correlated with each other, consistent with early disease skewing toward type 2 immune response, and two subsets were correlated with percentages of NKT cells or Th2 cells in the peripheral blood. Importantly, forward selection modeling identified 33 infant serum analytes that could be used to predict AD severity five years later (r2=0.85, p=0.042). This dataset will likely have predictive value for AD persistence past infancy and will be useful in further defining the pathogenesis of atopic disease.

T helper differentiation of CAR T cells augments function and target cell killing

Chimeric antigen receptor (CAR) T cell therapy involves genetically manipulating T cells to express an antigen receptor specific for tumor protein, resulting in a powerful anti-cancer therapeutic. However, trafficking to tumor sites and the suppressive nature of the tumor microenvironment have prevented effective treatment of solid tumors. Previous work has shown that antigen specific T helper (Th) subsets have variable tumor killing capabilities, however, it is not completely defined how different transcriptional differentiation programs effect the fitness and function of CAR T cells. It was hypothesized that differentiation of T cells transduced with CAR improves cancer cell killing in an antigen specific manner. To test this hypothesis, splenic CD4+ and CD8+ T cells were cultured under T cell activating (T0), Th2 (T2), or Th9 (T9) cell differentiation conditions and transduced with a 2nd generation CD19-specific CAR. Control cells were transduced with CD19-specific CAR lacking the intracellular domain. CAR T cells were co-cultured with CD19+ B cells and target cell killing was measured by flow cytometry. Preliminary results show that CAR T9 cells, but not T2 cells, kill target cells similar to the clinic relevant T0 cells. FACS analysis of T cells after co-culture with target cells revealed antigen-experience promoted production of lineage specific cytokines as well as granzymes A and B. T9 conditions maintained a larger proportion of CD8+ T cells than T2 conditions, suggesting that T9 conditions promote expansion of effector CD8+ T cells. These results suggest that the Th9 transcriptional program promotes target cell killing, transduction efficiency, and generates a better ratio of CD4:CD8 T cells for adoptive cell therapy.

The role of IL-9 secreting CD4+ T helper cells in promoting mast cell expansion in pulmonary models of inflammation

Mast cells are tissue resident cells with granules that contain histamine and other proinflammatory mediators. Mast cells are important effectors in immediate type I hypersensitivity reactions. In severe allergic reactions, immunoglobulin E (IgE)-mediated mast cell degranulation triggers localized and systemic anaphylaxis. In allergic asthma, mast cells and T cells interact in the generation of long-lasting inflammation. The molecular mechanisms responsible for mast cell expansion has not been fully elucidated. Because T cells are an important source of the mast cell growth factor IL-9, we are interested in understanding the role of IL-9, and IL-9-producing T cells in mast cell expansion and recruitment. We have identified a role of T helper 9 (Th9) cells in influencing mast cell number and function in pulmonary models of inflammation. Using adoptive transfer models, we have defined a contribution of Th9 cells in immediate hypersensitivity. We have demonstrated that IL-9 expands mast cell progenitor numbers in bone marrow and lung, suggesting that there are systemic effects of local IL-9 production. We hypothesize that increased mature mast cells in the pulmonary system are from recruitment and expansion of progenitor cells rather than expansion of mature cells in situ. Ongoing studies will directly examine the relative contribution and function of the two populations during models of allergic airway inflammation.

IL-9 promotes allergic lung inflammation by differentially affecting macrophage populations

IL-9 promotes to the development of allergic lung disease through several responsive populations including mast cells, lymphocytes and eosinophils. However, it is not known if these represent the entire IL-9-responsive cell repertoire. In this study, we detected high IL-9R expression on macrophages and these cells occupied a large proportion of IL-9R+ cells in allergic lung. Allergic inflammation leads to a decrease in the number of alveolar macrophages (AM) in wild type mice. However, in Il9r−/− mice, the AM population is not diminished as greatly, suggesting that IL-9 represses AM self-renewal. The level of the IL-9R expression on blood monocyte is corelated with CCR2 expression, which is required for blood monocyte migration to the inflammatory site. In the chronic allergic airway disease model, the circulating monocyte population decreased coincident with an increase in the number of interstitial macrophages in the control mice compared to the Il9r−/− mice, suggesting IL-9 promotes monocyte migration and differentiation in the lung. Interestingly, IL-9 also induces a CD11c+ interstitial macrophage population in the allergic lung. Adoptive transfer of CD11c+ wild type macrophages to the Il9r−/− mice increased the inflammatory response. Thus, our study demonstrated that macrophages are important IL-9-responsive populations in allergic lung disease, and that IL-9 inhibits AM numbers as it promotes the development of pro-inflammatory CD11c+ and CD11c− interstitial macrophages. This balance is important in determining the level of allergic inflammation in the lung.

WNT/β-catenin directed metabolic choice uncouples lung-resident alveolar macrophage inflammatory activity from self-renewal

Fetal-derived tissue-resident macrophages exhibit stem cell-like features of self-renewal in adulthood to maintain macrophage population during homeostasis and/or various insults. However, little is known about the cellular and molecular mechanisms modulating proliferative and inflammatory fate decisions of tissue-resident macrophages in vivo. Here, we show that WNT-β-catenin signaling inhibited lung-resident alveolar macrophage (AM) self-renewal, while simultaneously promoted AM inflammatory activities in vitro and in vivo during influenza virus infection. Mechanistically, WNT engagement facilitated the binding of β-catenin with HIF-1α over its conventional binding partner TCF-4. Such a binding choice led to the elevated macrophage inflammation in a glycolysis-dependent manner, while inhibited AM self-renewal by causing mitochondrial damage and impairing oxidative phosphorylation. Thus, AM self-renewal and inflammatory activity are uncoupled by WNT-β-catenin signaling through HIF-1α-mediated cellular metabolic choice. Importantly, we showed that AM with high HIF-1α activity had limited proliferative capacity and produced inflammatory cytokines, while AM with low HIF-1α activity were highly proliferative and expressed genes associated with tissue repair function in vivo during influenza virus infection. In accordance, we demonstrated that AM proliferation and repopulation were needed for optimal lung repair following the clearance of influenza virus in the respiratory tract. Our results have revealed key mechanisms modulating macrophage fate choice between progeny production versus inflammatory effector activity, and subsequent effects on tissue inflammation and repair.