IL-1 family members and STAT activators induce cytokine production by Th2, Th17, and Th1 cells

Mast cells contribute to T-cell accumulation in the bronchoalveolar space in mice with IL-33-induced airway inflammation

Interleukin (IL)-33 released from airway epithelial cells plays a vital role in shaping type 2 immune responses by binding to the ST2 receptor present in many immune cells, including mast cells (MCs). Intranasal administration of IL-33 in mice induces type 2 lung inflammation, an increase in lung MC progenitors, and transepithelial migration of leukocytes to the bronchoalveolar space. The aim of this study was to determine the contribution of MCs in IL-33-induced lung pathology. Four daily intranasal administrations of IL-33 reduced spirometry-like lung function parameters, induced airway hyperresponsiveness, and increased leukocytes in bronchoalveolar lavage fluid (BAL) in an ST2-dependent manner. MC-deficient (Cpa3cre/+) mice, which lack MCs, had intact spirometry-like lung function but slightly reduced airway hyperresponsiveness, possibly related to reduced IL-33 or serotonin. Strikingly, Cpa3cre/+ mice exposed to IL-33 had 50% reduction in BAL T-cells, and CXCL1 and IL-33 were reduced in the lung. Intranasal IL-33 induced CXCR2 expression in T-cells in a MC-independent fashion. Furthermore, IL-33-induced lung MCs were immunopositive for CXCL1 and localized in the epithelium of wild-type mice. These results suggest that MCs are required to sustain intact lung IL-33 and CXCL1 levels in mice with IL-33-induced airway inflammation, thereby facilitating T-cell accumulation in the bronchoalveolar space.

The IL-1β/STAT1 Axis inhibits STAT3 function via Sequestration of the transcriptional activator GLIS2, leading to postoperative vascular dysfunction

Surgery-induced endothelial dysfunction is crucial in thrombus formation, driven by the release of inflammatory mediators due to surgical trauma. The STAT family, known for amplifying inflammatory responses via cytokine activation, plays an unclear role in the signaling mechanisms from surgery to molecular activation, and their regulatory effects on inflammation vary. This study aimed to identify key signaling pathways responsible for vascular dysfunction post-surgery and to discover potential targets for predicting or preventing thrombosis. To explore this, endothelial cells were co-cultured with post-surgical trauma serum and analyzed using various assays. Bioinformatics analysis linked surgical trauma with pathways involving thrombosis, interleukins, cytokines, and STAT signaling. Elevated inflammatory mediators were observed in mouse serum post-surgical trauma, with IL-6 activating STAT3 to enhance endothelial proliferation, while IL-1β activated STAT1, inhibiting STAT3's effects. Gli-similar 2 (GLIS2), a novel coactivator of STAT3, was found to regulate STAT transcription. STAT1, however, inhibited GLIS2's interaction with STAT3, suppressing STAT3's role in endothelial proliferation. The study concludes that IL-1β-triggered STAT1 activation impedes GLIS2-STAT3 interaction, reducing STAT3's transcriptional activity and leading to endothelial dysfunction, presenting new targets for preventing post-surgical trauma endothelial dysfunction and thrombosis.

The role of immune cells settled in the bone marrow on adult hematopoietic stem cells

Certain immune cells, including neutrophils, macrophages, dendritic cells, B cells, Breg cells, CD4+ T cells, CD8+ T cells, and Treg cells, establish enduring residency within the bone marrow. Their distinctive interactions with hematopoiesis and the bone marrow microenvironment are becoming increasingly recognized alongside their multifaceted immune functions. These cells play a dual role in shaping hematopoiesis. They directly influence the quiescence, self-renewal, and multi-lineage differentiation of hematopoietic stem and progenitor cells through either direct cell-to-cell interactions or the secretion of various factors known for their immunological functions. Additionally, they actively engage with the cellular constituents of the bone marrow niche, particularly mesenchymal stem cells, endothelial cells, osteoblasts, and osteoclasts, to promote their survival and contribute to tissue repair, thereby fostering a supportive environment for hematopoietic stem and progenitor cells. Importantly, these bone marrow immune cells function synergistically, both locally and functionally, rather than in isolation. In summary, immune cells residing in the bone marrow are pivotal components of a sophisticated network of regulating hematopoiesis.

Molecular mechanisms regulating T helper 2 cell differentiation and function

T helper 2 (TH2) cells orchestrate type 2 immunity during protective antihelminth immunity and help restore tissue homoeostasis. Their misdirected activities against innocuous substances also underlie atopic diseases, such as asthma and allergy. Recent technological advances are uncovering novel insights into the molecular mechanisms governing TH2 cell differentiation and function.

Activin A Promotes Differentiation of a Pathogenic Multicytokine IL-9-secreting CD4+ T Cell Population

The development of Th subsets results from cellular and cytokine cues that are present in the inflammatory environment. The developing T cell integrates multiple signals from the environment that sculpt the cytokine-producing capacity of the effector T cell. Importantly, T cells can discriminate similar cytokine signals to generate distinct outcomes, and that discrimination is critical in Th subset development. IL-9-secreting Th9 cells regulate multiple immune responses, including immunity to pathogens and tumors, allergic inflammation, and autoimmunity. In combination with IL-4, TGF-β or activin A promotes IL-9 production; yet, it is not clear if both TGF-β family members generate Th9 cells with identical phenotype and function. We observed that in contrast to TGF-β that efficiently represses Th2 cytokines in murine Th9 cultures, differentiation with activin A produced a multicytokine T cell phenotype with secretion of IL-4, IL-5, IL-13, and IL-10 in addition to IL-9. Moreover, multicytokine secreting cells are more effective at promoting allergic inflammation. These observations suggest that although TGF-β and IL-4 were identified as cytokines that stimulate optimal IL-9 production, they might not be the only cytokines that generate optimal function from IL-9-producing T cells in immunity and disease.

Cross-talk between ILC2 and Gata3high Tregs locally constrains adaptive type 2 immunity

Regulatory T cells (Tregs) control adaptive immunity and restrain type 2 inflammation in allergic disease. Interleukin-33 promotes the expansion of tissue-resident Tregs and group 2 innate lymphoid cells (ILC2s); however, how Tregs locally coordinate their function within the inflammatory niche is not understood. Here, we show that ILC2s are critical orchestrators of Treg function. Using spatial, cellular, and molecular profiling of the type 2 inflamed niche, we found that ILC2s and Tregs engage in a direct (OX40L-OX40) and chemotaxis-dependent (CCL1-CCR8) cellular dialogue that enforces the local accumulation of Gata3high Tregs, which are transcriptionally and functionally adapted to the type 2 environment. Genetic interruption of ILC2-Treg communication resulted in uncontrolled type 2 lung inflammation after allergen exposure. Mechanistically, we found that Gata3high Tregs can modulate the local bioavailability of the costimulatory molecule OX40L, which subsequently controlled effector memory T helper 2 cell numbers. Hence, ILC2-Treg interactions represent a critical feedback mechanism to control adaptive type 2 immunity.

Innate acting memory Th1 cells modulate heterologous diseases

Through immune memory, infections have a lasting effect on the host. While memory cells enable accelerated and enhanced responses upon rechallenge with the same pathogen, their impact on susceptibility to unrelated diseases is unclear. We identify a subset of memory T helper 1 (Th1) cells termed innate acting memory T (TIA) cells that originate from a viral infection and produce IFN-γ with innate kinetics upon heterologous challenge in vivo. Activation of memory TIA cells is induced in response to IL-12 in combination with IL-18 or IL-33 but is TCR independent. Rapid IFN-γ production by memory TIA cells is protective in subsequent heterologous challenge with the bacterial pathogen Legionella pneumophila. In contrast, antigen-independent reactivation of CD4+ memory TIA cells accelerates disease onset in an autoimmune model of multiple sclerosis. Our findings demonstrate that memory Th1 cells can acquire additional TCR-independent functionality to mount rapid, innate-like responses that modulate susceptibility to heterologous challenges.

IL-33/NF-κB/ST2L/Rab37 positive-feedback loop promotes M2 macrophage to limit chemotherapeutic efficacy in lung cancer

IL-33 is a danger signal that binds to its receptor ST2L to promote tumor progression. This study identifies the IL-33/ST2L positive-feedback loop and the trafficking of ST2L membrane presentation in macrophages that contribute to lung tumor progression. Mechanistically, IL-33 induces ST2L upregulation by activating NF-κB, which binds to the promoter region of the ST2L gene. Moreover, Rab37, a small GTPase involved in membrane trafficking, mediates ST2L trafficking to the plasma membrane of M2 macrophages. This IL-33/NF-κB/ST2L/Rab37 axis promotes positive-feedback loops that enhance ST2L expression and membrane trafficking in M2 macrophages. Notably, neutralizing antibodies against IL-33 or ST2L block NF-κB activity, suppress M2 macrophage polarization, and synergistically inhibit tumor growth when combined with cisplatin treatment in vitro/vivo. Clinically, Rab37+/ST2L+/CD206+ tumor-infiltrating M2 macrophages correlate with advanced-stage lung cancer patients with poor response to chemotherapy. These findings unveil a positive-feedback mechanism and provide a basis for IL-33/ST2L-targeting therapy for cancer.

The CD27/CD70 pathway negatively regulates visceral adipose tissue-resident Th2 cells and controls metabolic homeostasis

Adipose tissue homeostasis relies on the interplay between several regulatory lineages, such as type 2 innate lymphoid cells (ILC2s), T helper 2 (Th2) cells, regulatory T cells, eosinophils, and type 2 macrophages. Among them, ILC2s are numerically the dominant source of type 2 cytokines and are considered as major regulators of adiposity. Despite the overlap in immune effector molecules and sensitivity to alarmins (thymic stromal lymphopoietin and interleukin-33) between ILC2s and resident memory Th2 lymphocytes, the role of the adaptive axis of type 2 immunity remains unclear. We show that mice deficient in CD27, a member of the tumor necrosis factor receptor superfamily, are more resistant to obesity and associated disorders. A comparative analysis of the CD4 compartment of both strains revealed higher numbers of fat-resident memory Th2 cells in the adipose tissue of CD27 knockout mice, which correlated with decreased programmed cell death protein 1-induced apoptosis. Our data point to a non-redundant role for Th2 lymphocytes in obesogenic conditions.

Actives from the Micro-Immunotherapy Medicine 2LMIREG® Reduce the Expression of Cytokines and Immune-Related Markers Including Interleukin-2 and HLA-II While Modulating Oxidative Stress and Mitochondrial Function

Introduction

Micro-immunotherapy (MI) is a therapeutic option employing low doses (LD) and ultra-low doses (ULD) of cytokines and immune factors to help the organism at modulating the immune responses. In an overpowering inflammatory context, this strategy may support the restoration of the body's homeostasis, as the active ingredients of MI medicines' (MIM) could boost or slow down the physiological functions of the immune cells. The aim of the study is to evaluate for the first time the in vitro anti-inflammatory properties of some actives employed by the MIM of interest in several human immune cell models.

Methods

In the first part of the study, the effects of the actives from the MIM of interest were assessed from a molecular standpoint: the expression of HLA-II, interleukin (IL)-2, and the secretion of several other cytokines were evaluated. In addition, as mitochondrial metabolism is also involved in the inflammatory processes, the second part of the study aimed at assessing the effects of these actives on the mitochondrial reactive oxygen species (ROS) production and on the mitochondrial membrane potential.

Results

We showed that the tested actives decreased the expression of HLA-DR and HLA-DP in IFN-γ-stimulated endothelial cells and in LPS-treated-M1-macrophages. The tested MIM slightly reduced the intracellular expression of IL-2 in CD4+ and CD8+ T-cells isolated from PMA/Iono-stimulated human PBMCs. Additionally, while the secretion of IL-2, IL-10, and IFN-γ was diminished, the treatment increased IL-6, IL-9, and IL-17A, which may correspond to a "Th17-like" secretory pattern. Interestingly, in PMA/Iono-treated PBMCs, we reported that the treatment reduced the ROS production in B-cells. Finally, in PMA/Iono-treated human macrophages, we showed that the treatment slightly protected the cells from early cell death/apoptosis.

Discussion

Overall, these results provide data about the molecular and functional anti-inflammatory effects of several actives contained in the tested MIM in immune-related cells, and their impact on two mitochondria-related processes.

Association of different cell types and inflammation in early acne vulgaris

Acne vulgaris, one of the most common skin diseases, is a chronic cutaneous inflammation of the upper pilosebaceous unit (PSU) with complex pathogenesis. Inflammation plays a central role in the pathogenesis of acne vulgaris. During the inflammatory process, the innate and adaptive immune systems are coordinately activated to induce immune responses. Understanding the infiltration and cytokine secretion of differential cells in acne lesions, especially in the early stages of inflammation, will provide an insight into the pathogenesis of acne. The purpose of this review is to synthesize the association of different cell types with inflammation in early acne vulgaris and provide a comprehensive understanding of skin inflammation and immune responses.

The dichotomic role of single cytokines: Fine-tuning immune responses

Cytokines are known for their pleiotropic effects. They can be classified by their function as pro-inflammatory, such as tumor necrosis factor (TNF), interleukin (IL) 1 and IL-12, or anti-inflammatory, like IL-10, IL-35 and transforming growth factor β (TGF-β). Though this type of classification is an important simplification for the understanding of the general cytokine's role, it can be misleading. Here, we discuss recent studies that show a dichotomic role of the so-called pro and anti-inflammatory cytokines, highlighting that their function can be dependent on the microenvironment and their concentrations. Furthermore, we discuss how the back-and-forth interplay between cytokines and immunometabolism can influence the dichotomic role of inflammatory responses as an important target to complement cytokine-based therapies.

Activation of the aryl hydrocarbon receptor inhibits neuropilin-1 upregulation on IL-2-responding CD4+ T cells

Neuropilin-1 (Nrp1), a transmembrane protein expressed on CD4+ T cells, is mostly studied in the context of regulatory T cell (Treg) function. More recently, there is increasing evidence that Nrp1 is also highly expressed on activated effector T cells and that increases in these Nrp1-expressing CD4+ T cells correspond with immunopathology across several T cell-dependent disease models. Thus, Nrp1 may be implicated in the identification and function of immunopathologic T cells. Nrp1 downregulation in CD4+ T cells is one of the strongest transcriptional changes in response to immunoregulatory compounds that act though the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor. To better understand the link between AhR and Nrp1 expression on CD4+ T cells, Nrp1 expression was assessed in vivo and in vitro following AhR ligand treatment. In the current study, we identified that the percentage of Nrp1 expressing CD4+ T cells increases over the course of activation and proliferation in vivo. The actively dividing Nrp1+Foxp3- cells express the classic effector phenotype of CD44hiCD45RBlo, and the increase in Nrp1+Foxp3- cells is prevented by AhR activation. In contrast, Nrp1 expression is not modulated by AhR activation in non-proliferating CD4+ T cells. The downregulation of Nrp1 on CD4+ T cells was recapitulated in vitro in cells isolated from C57BL/6 and NOD (non-obese diabetic) mice. CD4+Foxp3- cells expressing CD25, stimulated with IL-2, or differentiated into Th1 cells, were particularly sensitive to AhR-mediated inhibition of Nrp1 upregulation. IL-2 was necessary for AhR-dependent downregulation of Nrp1 expression both in vitro and in vivo. Collectively, the data demonstrate that Nrp1 is a CD4+ T cell activation marker and that regulation of Nrp1 could be a previously undescribed mechanism by which AhR ligands modulate effector CD4+ T cell responses.

Lung group 2 innate lymphoid cells differentially depend on local IL-7 for their distribution, activation, and maintenance in innate and adaptive immunity-mediated airway inflammation

Interleukin-7 (IL-7) is a cytokine critical for the development and maintenance of group 2 innate lymphoid cells (ILC2s). ILC2s are resident in peripheral tissues such as the intestine and lung. However, whether IL-7 produced in the lung plays a role in the maintenance and function of lung ILC2s during airway inflammation remains unknown. IL-7 was expressed in bronchoalveolar epithelial cells and lymphatic endothelial cells (LECs). To investigate the role of local IL-7 in lung ILC2s, we generated two types of IL-7 conditional knockout (IL-7cKO) mice: Sftpc-Cre (SPC-Cre) IL-7cKO mice specific for bronchial epithelial cells and type 2 alveolar epithelial cells and Lyve1-Cre IL-7cKO mice specific for LECs. In steady state, ILC2s were located near airway epithelia, although lung ILC2s were unchanged in the two lines of IL-7cKO mice. In papain-induced airway inflammation dependent on innate immunity, lung ILC2s localized near bronchia via CCR4 expression, and eosinophil infiltration and type 2 cytokine production were reduced in SPC-Cre IL-7cKO mice. In contrast, in house dust mite (HDM)-induced airway inflammation dependent on adaptive immunity, lung ILC2s localized near lymphatic vessels via their CCR2 expression 2 weeks after the last challenge. Furthermore, lung ILC2s were decreased in Lyve1-Cre IL-7cKO mice in the HDM-induced inflammation because of decreased cell survival and proliferation. Finally, administration of anti-IL-7 antibody attenuated papain-induced inflammation by suppressing the activation of ILC2s. Thus, this study demonstrates that IL-7 produced by bronchoalveolar epithelial cells and LECs differentially controls the activation and maintenance of lung ILC2s, where they are localized in airway inflammation.

Allergen exposure functionally alters influenza-specific CD4+ Th1 memory cells in the lung

CD4+ lung-resident memory T cells (TRM) generated in response to influenza infection confer effective protection against subsequent viral exposures. Whether these cells can be altered by environmental antigens and cytokines released during heterologous, antigen-independent immune responses is currently unclear. We therefore investigated how influenza-specific CD4+ Th1 TRM in the lung are impacted by a subsequent Th2-inducing respiratory house dust mite (HDM) exposure. Although naïve influenza-specific CD4+ T cells in the lymph nodes do not respond to HDM, influenza-specific CD4+ TRM in the lungs do respond to a subsequent allergen exposure by decreasing expression of the transcription factor T-bet. This functional alteration is associated with decreased IFN-γ production upon restimulation and improved disease outcomes following heterosubtypic influenza challenge. Further investigation revealed that ST2 signaling in CD4+ T cells during allergic challenge is necessary to induce these changes in lung-resident influenza-specific CD4+ TRM. Thus, heterologous antigen exposure or ST2-signaling can drive persistent changes in CD4+ Th1 TRM populations and impact protection upon reinfection.

ATP functions as a primary alarmin in allergen-induced type 2 immunity

Environmental allergens that interact with the airway epithelium can activate cellular stress pathways that lead to the release of danger signals known as alarmins. The mechanisms of alarmin release are distinct from damage-associated molecular patterns (DAMPs), which typically escape from cells after loss of plasma membrane integrity. Oxidative stress represents a form of allergen-induced cellular stress that stimulates oxidant-sensing mechanisms coupled to pathways, which facilitate alarmin mobilization and efflux across the plasma membrane. In this review, we highlight examples of alarmin release and discuss their roles in the initiation of type 2 immunity and allergic airway inflammation. In addition, we discuss the concept of alarmin amplification, where "primary" alarmins, which are directly released in response to a specific cellular stress, stimulate additional signaling pathways that lead to secretion of "secondary" alarmins that include proinflammatory cytokines, such as IL-33, as well as genomic and mitochondrial DNA that coordinate or amplify type 2 immunity. Accordingly, allergen-evoked cellular stress can elicit a hierarchy of alarmin signaling responses from the airway epithelium that trigger local innate immune reactions, impact adaptive immunity, and exacerbate diseases including asthma and other chronic inflammatory conditions that affect airway function.

Over-expression of IL-33 enhances rabies virus early antigen presentations and cellular immune responses in mice

Human inactivated rabies virus (RABV) vaccines have been widely used worldwide over 30 years. The mechanisms of humoral immunity elicited by previously reported rabies candidate vaccines have been fully investigated, but little is known about the cellular immunity profiles. Herein, the recombinant RABV rLBNSE-IL-33 overexpressing the mouse interleukin-33 (IL-33) proliferated well in Neuro-2a cells and had no effects with the parent virus on growth kinetic in vitro and viral pathogenicity in mice. The rLBNSE-IL-33 experienced more antigen presentations by MHC-II on DCs and activated more CD4+ T cells which helped recruit more CD19+CD40+ B cells in blood and promote rapid and robust IgG1 antibodies responses at initial infection stage compared with the parent rLBNSE strain. Simultaneously, the rLBNSE-IL-33 were also presented by MHC-I to CD8+ T cells which contributed to produce high levels of IgG2a. The rLBNSE-IL-33 elicited significantly high levels of RABV-specific IFN-γ secreting memory CD4+ T cells, more RABV-specific IL-4 and IFN-γ secreting memory CD8+ T cells in spleens at early infection stage in mice. Altogether, overexpression of IL-33 in rLBNSE-IL-33 enhanced early antigen presentation, markedly promote CD4+, memory CD4+ and CD8+ T cells-mediated responses and provided a 100 % protection from lethal RABV challenge in mice. These findings provided an alternative novel therapy and vaccine strategy in future.

IL-33 Orchestrated the Interaction and Immunoregulatory Functions of Alternatively Activated Macrophages and Regulatory T Cells In Vitro

Our group has previously demonstrated elevated serum-soluble ST2 in patients with active systemic lupus erythematosus, suggesting a role of IL-33 in the underlying pathogenesis. However, inconsistent results have been reported on the effect of exogenous IL-33 on murine lupus activity, which may be mediated by concerted actions of various immune cells in vivo. This study aimed to examine the function of IL-33 on macrophage polarization and regulatory T cells (Treg) and their interactive effects in the lupus setting by in vitro coculture experiments of macrophages and T cells that were performed in the presence or absence of IL-33-containing medium. Compared to IL-4-polarized bone marrow-derived macrophages (BMDM) from MRL/MpJ mice, adding IL-33 enhanced mRNA expression of markers of alternatively activated macrophages, including CD206 and Arg1. IL-33 and IL-4 copolarized BMDM produced higher TGF-β but not IL-6 upon inflammatory challenge. These BMDM induced an increase in the Foxp3+CD25+ Treg population in cocultured allogeneic T cells from MRL/MpJ and predisease MRL/lpr mice. These copolarized BMDM also showed an enhanced suppressive effect on T cell proliferation with reduced IFN-γ and IL-17 release but increased TGF-β production. In the presence of TGF-β and IL-2, IL-33 also directly promoted inducible Treg that expressed a high level of CD25 and more sustained Foxp3. Unpolarized BMDM cocultured with these Treg displayed higher phagocytosis. In conclusion, TGF-β was identified as a key cytokine produced by IL-4 and IL-33 copolarized alternatively activated macrophages and the induced Treg, which may contribute to a positive feedback loop potentiating the immunoregulatory functions of IL-33.

Activation of the aryl hydrocarbon receptor inhibits neuropilin-1 upregulation on IL-2 responding CD4 + T cells

Neuropilin-1 (Nrp1), a transmembrane protein expressed on CD4 + T cells, is mostly studied in the context of regulatory T cell (Treg) function. More recently, there is increasing evidence that Nrp1 is also highly expressed on activated effector T cells and that increases in these Nrp1-expressing CD4 + T cells correspond with immunopathology across several T cell-dependent disease models. Thus, Nrp1 may be implicated in the identification and function of immunopathologic T cells. Nrp1 downregulation in CD4 + T cells is one of the strongest transcriptional changes in response to immunoregulatory compounds that act though the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor. To better understand the link between AhR and Nrp1 expression on CD4 + T cells, Nrp1 expression was assessed in vivo and in vitro following AhR ligand treatment. In the current study, we identified that the percentage of Nrp1 expressing CD4 + T cells increases over the course of activation and proliferation in vivo . The actively dividing Nrp1 + Foxp3 - cells express the classic effector phenotype of CD44 hi CD45RB lo , and the increase in Nrp1 + Foxp3 - cells is prevented by AhR activation. In contrast, Nrp1 expression is not modulated by AhR activation in non-proliferating CD4 + T cells. The downregulation of Nrp1 on CD4 + T cells was recapitulated in vitro in cells isolated from C57BL/6 and NOD (non-obese diabetic) mice. CD4 + Foxp3 - cells expressing CD25, stimulated with IL-2, or differentiated into Th1 cells, were particularly sensitive to AhR-mediated inhibition of Nrp1 upregulation. IL-2 was necessary for AhR-dependent downregulation of Nrp1 expression both in vitro and in vivo . Collectively, the data demonstrate that Nrp1 is a CD4 + T cell activation marker and that regulation of Nrp1 could be a previously undescribed mechanism by which AhR ligands modulate effector CD4 + T cell responses.

TRAF4 is crucial for ST2+ memory Th2 cell expansion in IL-33-driven airway inflammation

Tumor necrosis factor receptor-associated factor 4 (TRAF4) is an important regulator of type 2 responses in the airway; however, the underlying cellular and molecular mechanisms remain elusive. Herein, we generated T cell-specific TRAF4-deficient (CD4-cre Traf4fl/fl) mice and investigated the role of TRAF4 in memory Th2 cells expressing IL-33 receptor (ST2, suppression of tumorigenicity 2) (ST2+ mTh2 cells) in IL-33-mediated type 2 airway inflammation. We found that in vitro-polarized TRAF4-deficient (CD4-cre Traf4fl/fl) ST2+ mTh2 cells exhibited decreased IL-33-induced proliferation as compared with TRAF4-sufficient (Traf4fl/fl) cells. Moreover, CD4-cre Traf4fl/fl mice showed less ST2+ mTh2 cell proliferation and eosinophilic infiltration in the lungs than Traf4fl/fl mice in the preclinical models of IL-33-mediated type 2 airway inflammation. Mechanistically, we discovered that TRAF4 was required for the activation of AKT/mTOR and ERK1/2 signaling pathways as well as the expression of transcription factor Myc and nutrient transporters (Slc2a1, Slc7a1, and Slc7a5), signature genes involved in T cell growth and proliferation, in ST2+ mTh2 cells stimulated by IL-33. Taken together, the current study reveals a role of TRAF4 in ST2+ mTh2 cells in IL-33-mediated type 2 pulmonary inflammation, opening up avenues for the development of new therapeutic strategies.

A Deep View of the Biological Property of Interleukin-33 and Its Dysfunction in the Gut

Intestinal diseases have always posed a serious threat to human health, with inflammatory bowel disease (IBD) being one of them. IBD is an autoimmune disease characterized by chronic inflammation, including ulcerative colitis (UC) and Crohn's disease (CD). The "alarm" cytokine IL-33, which is intimately associated with Th2 immunity, is a highly potent inflammatory factor that is considered to have dual functions-operating as both a pro-inflammatory cytokine and a transcriptional regulator. IL-33 has been shown to play a crucial role in both the onset and development of IBD. Therefore, this review focuses on the pathogenesis of IBD, the major receptor cell types, and the activities of IL-33 in innate and adaptive immunity, as well as its underlying mechanisms and conflicting conclusions in IBD. We have also summarized different medicines targeted to IL-33-associated diseases. Furthermore, we have emphasized the role of IL-33 in gastrointestinal cancer and parasitic infections, giving novel prospective therapeutic utility in the future application of IL-33.

Pyroptosis: A road to next-generation cancer immunotherapy

The goal of cancer immunotherapy is to clear tumor cells by activating antitumor immunity, especially by mobilizing tumor-reactive CD8+T cells. Pyroptosis, programmed lytic cell death mediated by gasdermin (GSDM), results in the release of cellular antigens, damage-associated molecular patterns (DAMPs) and cytokines. Therefore, pyroptotic tumor cell-derived tumor antigens and DAMPs not only reverse immunosuppression of the tumor microenvironment (TME) but also enhance tumor antigen presentation by dendritic cells, leading to robust antitumor immunity. Exploring nanoparticles and other approaches to spatiotemporally control tumor pyroptosis by regulating gasdermin expression and activation is promising for next-generation immunotherapy.

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.

Aberrant inflammasome activation as a driving force of human autoimmune skin disease

Autoimmune skin diseases are understood as conditions in which the adaptive immune system with autoantigen-specific T cells and autoantibody-producing B cells reacting against self-tissues plays a crucial pathogenic role. However, there is increasing evidence that inflammasomes, which are large multiprotein complexes that were first described 20 years ago, contribute to autoimmune disease progression. The inflammasome and its contribution to the bioactivation of interleukins IL-1β and IL-18 play an essential role in combating foreign pathogens or tissue damage, but may also act as a pathogenic driver of myriad chronic inflammatory diseases when dysfunctionally regulated. Inflammasomes containing the NOD-like receptor family members NLRP1 and NLRP3 as well as the AIM2-like receptor family member AIM2 have been increasingly investigated in inflammatory skin conditions. In addition to autoinflammatory diseases, which are often associated with skin involvement, the aberrant activation of the inflammasome has also been implied in autoimmune diseases that can either affect the skin besides other organs such as systemic lupus erythematosus and systemic sclerosis or are isolated to the skin in humans. The latter include, among others, the T-cell mediated disorders vitiligo, alopecia areata, lichen planus and cutaneous lupus erythematosus as well as the autoantibody-driven blistering skin disease bullous pemphigoid. Some diseases are characterized by both autoinflammatory and autoimmune responses such as the chronic inflammatory skin disease psoriasis. Further insights into inflammasome dysregulation and associated pathways as well as their role in forming adaptive immune responses in human autoimmune skin pathology could potentially offer a new field of therapeutic options in the future.

Steady-state memory-phenotype conventional CD4+ T cells exacerbate autoimmune neuroinflammation in a bystander manner via the Bhlhe40/GM-CSF axis

Memory-phenotype (MP) CD4⁺ T cells are a substantial population of conventional T cells that exist in steady-state mice, yet their immunological roles in autoimmune disease remain unclear. In this work, we unveil a unique phenotype of MP CD4⁺ T cells determined by analyzing single-cell transcriptomic data and T cell receptor (TCR) repertoires. We found that steady-state MP CD4⁺ T cells in the spleen were composed of heterogeneous effector subpopulations and existed regardless of germ and food antigen exposure. Distinct subpopulations of MP CD4⁺ T cells were specifically activated by IL-1 family cytokines and STAT activators, revealing that the cells exerted TCR-independent bystander effector functions similar to innate lymphoid cells. In particular, CCR6^high subpopulation of MP CD4⁺ T cells were major responders to IL-23 and IL-1β without MOG_35-55 antigen reactivity, which gave them pathogenic Th17 characteristics and allowed them to contribute to autoimmune encephalomyelitis. We identified that Bhlhe40 in CCR6^high MP CD4⁺ T cells as a key regulator of GM-CSF expression through IL-23 and IL-1β signaling, contributing to central nervous system (CNS) pathology in experimental autoimmune encephalomyelitis. Collectively, our findings reveal the clearly distinct effector-like heterogeneity of MP CD4⁺ T cells in the steady state and indicate that CCR6^high MP CD4⁺ T cells exacerbate autoimmune neuroinflammation via the Bhlhe40/GM-CSF axis in a bystander manner.

Osteoimmunology in Periodontitis and Orthodontic Tooth Movement

PURPOSE OF REVIEW

To review the role of the immune cells and their interaction with cells found in gingiva, periodontal ligament, and bone that leads to net bone loss in periodontitis or bone remodeling in orthodontic tooth movement.

RECENT FINDINGS

Periodontal disease is one of the most common oral diseases causing inflammation in the soft and hard tissues of the periodontium and is initiated by bacteria that induce a host response. Although the innate and adaptive immune response function cooperatively to prevent bacterial dissemination, they also play a major role in gingival inflammation and destruction of the connective tissue, periodontal ligament, and alveolar bone characteristic of periodontitis. The inflammatory response is triggered by bacteria or their products that bind to pattern recognition receptors that induce transcription factor activity to stimulate cytokine and chemokine expression. Epithelial, fibroblast/stromal, and resident leukocytes play a key role in initiating the host response and contribute to periodontal disease. Single-cell RNA-seq (scRNA-seq) experiments have added new insight into the roles of various cell types in the response to bacterial challenge. This response is modified by systemic conditions such as diabetes and smoking. In contrast to periodontitis, orthodontic tooth movement (OTM) is a sterile inflammatory response induced by mechanical force. Orthodontic force application stimulates acute inflammatory responses in the periodontal ligament and alveolar bone stimulated by cytokines and chemokines that produce bone resorption on the compression side. On the tension side, orthodontic forces induce the production of osteogenic factors, stimulating new bone formation. A number of different cell types, cytokines, and signaling/pathways are involved in this complex process. Inflammatory and mechanical force-induced bone remodeling involves bone resorption and bone formation. The interaction of leukocytes with host stromal cells and osteoblastic cells plays a key role in both initiating the inflammatory events as well as inducing a cellular cascade that results in remodeling in orthodontic tooth movement or in tissue destruction in periodontitis.

Transcriptional control of ILC identity

Innate lymphoid cells (ILCs) are heterogeneous innate immune cells which participate in host defense, mucosal repair and immunopathology by producing effector cytokines similarly to their adaptive immune cell counterparts. The development of ILC1, 2, and 3 subsets is controlled by core transcription factors: T-bet, GATA3, and RORγt, respectively. ILCs can undergo plasticity and transdifferentiate to other ILC subsets in response to invading pathogens and changes in local tissue environment. Accumulating evidence suggests that the plasticity and the maintenance of ILC identity is controlled by a balance between these and additional transcription factors such as STATs, Batf, Ikaros, Runx3, c-Maf, Bcl11b, and Zbtb46, activated in response to lineage-guiding cytokines. However, how interplay between these transcription factors leads to ILC plasticity and the maintenance of ILC identity remains hypothetical. In this review, we discuss recent advances in understanding transcriptional regulation of ILCs in homeostatic and inflammatory conditions.

Interleukin-33 Ameliorates Murine Systemic Lupus Erythematosus and Is Associated with Induction of M2 Macrophage Polarisation and Regulatory T Cells

The innate cytokine IL-33 is increasingly recognised to possess biological effects on various immune cells. We have previously demonstrated elevated serum level of soluble ST2 in patients with active systemic lupus erythematosus suggesting involvement of IL-33 and its receptor in the lupus pathogenesis. This study sought to examine the effect of exogenous IL-33 on disease activity of pre-disease lupus-prone mice and the underlying cellular mechanisms. Recombinant IL-33 was administered to MRL/lpr mice for 6 weeks, whereas control group received phosphate-buffered saline. IL-33-treated mice displayed less proteinuria, renal histological inflammatory changes, and had lower serum levels of pro-inflammatory cytokines including IL-6 and TNF-α. Renal tissue and splenic CD11b+ extracts showed features of M2 polarisation with elevated mRNA expression of Arg1, FIZZI, and reduced iNOS. These mice also had increased IL-13, ST2, Gata3, and Foxp3 mRNA expression in renal and splenic tissues. Kidneys of these mice displayed less CD11b+ infiltration, had downregulated MCP-1, and increased infiltration of Foxp3-expressing cells. Splenic CD4+ T cells showed increased ST2-expressing CD4+Foxp3+ population and reduced IFN-γ+ population. There were no differences in serum anti-dsDNA antibodies and renal C3 and IgG2a deposit in these mice. Exogenous IL-33 was found to ameliorate disease activity in lupus-prone mice with induction of M2 polarisation, Th2 response, and expansion of regulatory T cells. IL-33 likely orchestrated autoregulation of these cells through upregulation of ST2 expression.

The Differentially Expressed Genes Responsible for the Development of T Helper 9 Cells From T Helper 2 Cells in Various Disease States: Immuno-Interactomics Study

BACKGROUND

T helper (Th) 9 cells are a novel subset of Th cells that develop independently from Th2 cells and are characterized by the secretion of interleukin (IL)-9. Studies have suggested the involvement of Th9 cells in variable diseases such as allergic and pulmonary diseases (eg, asthma, chronic obstructive airway disease, chronic rhinosinusitis, nasal polyps, and pulmonary hypoplasia), metabolic diseases (eg, acute leukemia, myelocytic leukemia, breast cancer, lung cancer, melanoma, pancreatic cancer), neuropsychiatric disorders (eg, Alzheimer disease), autoimmune diseases (eg, Graves disease, Crohn disease, colitis, psoriasis, systemic lupus erythematosus, systemic scleroderma, rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, atopic dermatitis, eczema), and infectious diseases (eg, tuberculosis, hepatitis). However, there is a dearth of information on its involvement in other metabolic, neuropsychiatric, and infectious diseases.

OBJECTIVE

This study aims to identify significant differentially altered genes in the conversion of Th2 to Th9 cells, and their regulating microRNAs (miRs) from publicly available Gene Expression Omnibus data sets of the mouse model using in silico analysis to unravel various pathogenic pathways involved in disease processes.

METHODS

Using differentially expressed genes (DEGs) identified from 2 publicly available data sets (GSE99166 and GSE123501) we performed functional enrichment and network analyses to identify pathways, protein-protein interactions, miR-messenger RNA associations, and disease-gene associations related to significant differentially altered genes implicated in the conversion of Th2 to Th9 cells.

RESULTS

We extracted 260 common downregulated, 236 common upregulated, and 634 common DEGs from the expression profiles of data sets GSE99166 and GSE123501. Codifferentially expressed ILs, cytokines, receptors, and transcription factors (TFs) were enriched in 7 crucial Kyoto Encyclopedia of Genes and Genomes pathways and Gene Ontology. We constructed the protein-protein interaction network and predicted the top regulatory miRs involved in the Th2 to Th9 differentiation pathways. We also identified various metabolic, allergic and pulmonary, neuropsychiatric, autoimmune, and infectious diseases as well as carcinomas where the differentiation of Th2 to Th9 may play a crucial role.

CONCLUSIONS

This study identified hitherto unexplored possible associations between Th9 and disease states. Some important ILs, including CCL1 (chemokine [C-C motif] ligand 1), CCL20 (chemokine [C-C motif] ligand 20), IL-13, IL-4, IL-12A, and IL-9; receptors, including IL-12RB1, IL-4RA (interleukin 9 receptor alpha), CD53 (cluster of differentiation 53), CD6 (cluster of differentiation 6), CD5 (cluster of differentiation 5), CD83 (cluster of differentiation 83), CD197 (cluster of differentiation 197), IL-1RL1 (interleukin 1 receptor-like 1), CD101 (cluster of differentiation 101), CD96 (cluster of differentiation 96), CD72 (cluster of differentiation 72), CD7 (cluster of differentiation 7), CD152 (cytotoxic T lymphocyte-associated protein 4), CD38 (cluster of differentiation 38), CX3CR1 (chemokine [C-X3-C motif] receptor 1), CTLA2A (cytotoxic T lymphocyte-associated protein 2 alpha), CTLA28, and CD196 (cluster of differentiation 196); and TFs, including FOXP3 (forkhead box P3), IRF8 (interferon regulatory factor 8), FOXP2 (forkhead box P2), RORA (RAR-related orphan receptor alpha), AHR (aryl-hydrocarbon receptor), MAF (avian musculoaponeurotic fibrosarcoma oncogene homolog), SMAD6 (SMAD family member 6), JUN (Jun proto-oncogene), JAK2 (Janus kinase 2), EP300 (E1A binding protein p300), ATF6 (activating transcription factor 6), BTAF1 (B-TFIID TATA-box binding protein associated factor 1), BAFT (basic leucine zipper transcription factor), NOTCH1 (neurogenic locus notch homolog protein 1), GATA3 (GATA binding protein 3), SATB1 (special AT-rich sequence binding protein 1), BMP7 (bone morphogenetic protein 7), and PPARG (peroxisome proliferator-activated receptor gamma, were able to identify significant differentially altered genes in the conversion of Th2 to Th9 cells. We identified some common miRs that could target the DEGs. The scarcity of studies on the role of Th9 in metabolic diseases highlights the lacunae in this field. Our study provides the rationale for exploring the role of Th9 in various metabolic disorders such as diabetes mellitus, diabetic nephropathy, hypertensive disease, ischemic stroke, steatohepatitis, liver fibrosis, obesity, adenocarcinoma, glioblastoma and glioma, malignant neoplasm of stomach, melanoma, neuroblastoma, osteosarcoma, pancreatic carcinoma, prostate carcinoma, and stomach carcinoma.

Bystander activation of Bordetella pertussis-induced nasal tissue-resident memory CD4 T cells confers heterologous immunity to Klebsiella pneumoniae

Tissue-resident memory CD4 T (T_RM ) cells induced by infection with Bordetella pertussis persist in respiratory tissues and confer long-term protective immunity against reinfection. However, it is not clear how they are maintained in respiratory tissues. Here, we demonstrate that B. pertussis-specific CD4 T_RM cells produce IL-17A in response to in vitro stimulation with LPS or heat-killed Klebsiella pneumoniae (HKKP) in the presence of dendritic cells. Furthermore, IL-17A-secreting CD4 T_RM cells expand in the lung and nasal tissue of B. pertussis convalescent mice following in vivo administration of LPS or HKKP. Bystander activation of CD4 T_RM cells was suppressed by anti-IL-12p40 but not by anti-MHCII antibodies. Furthermore, purified respiratory tissue-resident, but not circulating, CD4 T cells from convalescent mice produced IL-17A following direct stimulation with IL-23 and IL-1β or IL-18. Intranasal immunization of mice with a whole-cell pertussis vaccine induced respiratory CD4 T_RM cells that were reactivated following stimulation with K. pneumoniae. Furthermore, the nasal pertussis vaccine conferred protective immunity against B. pertussis but also attenuated infection with K. pneumoniae. Our findings demonstrate that CD4 T_RM cells induced by respiratory infection or vaccination can undergo bystander activation and confer heterologous immunity to an unrelated respiratory pathogen.

Differential regulation of lineage-determining transcription factor expression in innate lymphoid cell and adaptive T helper cell subsets

CD4 T helper (Th) cell subsets, including Th1, Th2 and Th17 cells, and their innate counterparts innate lymphoid cell (ILC) subsets consisting of ILC1s, ILC2s and ILC3s, display similar effector cytokine-producing capabilities during pro-inflammatory immune responses. These lymphoid cell subsets utilize the same set of lineage-determining transcription factors (LDTFs) for their differentiation, development and functions. The distinct ontogeny and developmental niches between Th cells and ILCs indicate that they may adopt different external signals for the induction of LDTF during lineage commitment. Increasing evidence demonstrates that many conserved cis-regulatory elements at the gene loci of LDTFs are often preferentially utilized for the induction of LDTF expression during Th cell differentiation and ILC development at different stages. In this review, we discuss the functions of lineage-related cis-regulatory elements in inducing T-bet, GATA3 or RORγt expression based on the genetic evidence provided in recent publications. We also review and compare the upstream signals involved in LDTF induction in Th cells and ILCs both in vitro and in vivo. Finally, we discuss the possible mechanisms and physiological importance of regulating LDTF dynamic expression during ILC development and activation.

Setd2 supports GATA3+ST2+ thymic-derived Treg cells and suppresses intestinal inflammation

Treg cells acquire distinct transcriptional properties to suppress specific inflammatory responses. Transcription characteristics of Treg cells are regulated by epigenetic modifications, the mechanism of which remains obscure. Here, we report that Setd2, a histone H3K36 methyltransferase, is important for the survival and suppressive function of Treg cells, especially those from the intestine. Setd2 supports GATA3⁺ST2⁺ intestinal thymic-derived Treg (tTreg) cells by facilitating the expression and reciprocal relationship of GATA3 and ST2 in tTreg cells. IL-33 preferentially boosts Th2 cells rather than GATA3⁺ Treg cells in Foxp3^Cre-YFPSetd2 ^flox/flox mice, corroborating the constraint of Th2 responses by Setd2 expression in Treg cells. SETD2 sustains GATA3 expression in human Treg cells, and SETD2 expression is increased in Treg cells from human colorectal cancer tissues. Epigenetically, Setd2 regulates the transcription of target genes (including Il1rl1) by modulating the activity of promoters and intragenic enhancers where H3K36me3 is typically deposited. Our findings provide mechanistic insights into the regulation of Treg cells and intestinal immunity by Setd2.

Gata3 ZsG and Gata3 ZsG-fl: Novel murine Gata3 reporter alleles for identifying and studying Th2 cells and ILC2s in vivo

T helper-2 (Th2) cells and type 2 innate lymphoid cells (ILC2s) play crucial roles during type 2 immune responses; the transcription factor GATA3 is essential for the differentiation and functions of these cell types. It has been demonstrated that GATA3 is critical for maintaining Th2 and ILC2 phenotype in vitro; GATA3 not only positively regulates type 2 lymphocyte-associated genes, it also negatively regulates many genes associated with other lineages. However, such functions cannot be easily verified in vivo because the expression of the markers for identifying Th2 and ILC2s depends on GATA3. Thus, whether Th2 cells and ILC2s disappear after Gata3 deletion or these Gata3-deleted "Th2 cells" or "ILC2s" acquire an alternative lineage fate is unknown. In this study, we generated novel GATA3 reporter mouse strains carrying the Gata3 ZsG or Gata3 ZsG-fl allele. This was achieved by inserting a ZsGreen-T2A cassette at the translation initiation site of either the wild type Gata3 allele or the modified Gata3 allele which carries two loxP sites flanking the exon 4. ZsGreen faithfully reflected the endogenous GATA3 protein expression in Th2 cells and ILC2s both in vitro and in vivo. These reporter mice also allowed us to visualize Th2 cells and ILC2s in vivo. An inducible Gata3 deletion system was created by crossing Gata3 ZsG-fl/fl mice with a tamoxifen-inducible Cre. Continuous expression of ZsGreen even after the Gata3 exon 4 deletion was noted, which allows us to isolate and monitor GATA3-deficient "Th2" cells and "ILC2s" during in vivo immune responses. Our results not only indicated that functional GATA3 is dispensable for regulating its own expression in mature type 2 lymphocytes, but also revealed that GATA3-deficient "ILC2s" might be much more stable in vivo than in vitro. Overall, the generation of these novel GATA3 reporters will provide valuable research tools to the scientific community in investigating type 2 immune responses in vivo.

Epithelial cell alarmin cytokines: Frontline mediators of the asthma inflammatory response

The exposure of the airway epithelium to external stimuli such as allergens, microbes, and air pollution triggers the release of the alarmin cytokines IL-25, IL-33 and thymic stromal lymphopoietin (TSLP). IL-25, IL-33 and TSLP interact with their ligands, IL-17RA, IL1RL1 and TSLPR respectively, expressed by hematopoietic and non-hematopoietic cells including dendritic cells, ILC2 cells, endothelial cells, and fibroblasts. Alarmins play key roles in driving type 2-high, and to a lesser extent type 2-low responses, in asthma. In addition, studies in which each of these three alarmins were targeted in allergen-challenged mice showed decreased chronicity of type-2 driven disease. Consequently, ascertaining the mechanism of activity of these upstream mediators has implications for understanding the outcome of targeted therapies designed to counteract their activity and alleviate downstream type 2-high and low effector responses. Furthermore, identifying the factors which shift the balance between the elicitation of type 2-high, eosinophilic asthma and type-2 low, neutrophilic-positive/negative asthma by alarmins is essential. In support of these efforts, observations from the NAVIGATOR trial imply that targeting TSLP in patients with tezepelumab results in reduced asthma exacerbations, improved lung function and control of the disease. In this review, we will discuss the mechanisms surrounding the secretion of IL-25, IL-33, and TSLP from the airway epithelium and how this influences the allergic airway cascade. We also review in detail how alarmin-receptor/co-receptor interactions modulate downstream allergic inflammation. Current strategies which target alarmins, their efficacy and inflammatory phenotype will be discussed.

Dual Immune Regulatory Roles of Interleukin-33 in Pathological Conditions

Interleukin-33 (IL-33), a member of the IL-1 cytokine family and a multifunctional cytokine, plays critical roles in maintaining host homeostasis and in pathological conditions, such as allergy, infectious diseases, and cancer, by acting on multiple types of immune cells and promoting type 1 and 2 immune responses. IL-33 is rapidly released by immune and non-immune cells upon stimulation by stress, acting as an “alarmin” by binding to its receptor, suppression of tumorigenicity 2 (ST2), to trigger downstream signaling pathways and activate inflammatory and immune responses. It has been recognized that IL-33 displays dual-functioning immune regulatory effects in many diseases and has both pro- and anti-tumorigenic effects, likely depending on its primary target cells, IL-33/sST2 expression levels, cellular context, and the cytokine microenvironment. Herein, we summarize our current understanding of the biological functions of IL-33 and its roles in the pathogenesis of various conditions, including inflammatory and autoimmune diseases, infections, cancers, and cases of organ transplantation. We emphasize the nature of context-dependent dual immune regulatory functions of IL-33 in many cells and diseases and review systemic studies to understand the distinct roles of IL-33 in different cells, which is essential to the development of more effective diagnoses and therapeutic approaches for IL-33-related diseases.

Upregulation of interleukin-19 in saliva of patients with COVID-19

Cytokines are major players in orchestrating inflammation, disease pathogenesis and severity during COVID-19 disease. However, the role of IL-19 in COVID-19 pathogenesis remains elusive. Herein, through the analysis of transcriptomic datasets of SARS-CoV-2 infected lung cells, nasopharyngeal swabs, and lung autopsies of COVID-19 patients, we report that expression levels of IL-19 and its receptor, IL-20R2, were upregulated following SARS-CoV-2 infection. Of 202 adult COVID-19 patients, IL-19 protein level was significantly higher in blood and saliva of asymptomatic patients compared to healthy controls when adjusted for patients’ demographics (P < 0.001). Interestingly, high saliva IL-19 level was also associated with COVID-19 severity (P < 0.0001), need for mechanical ventilation (P = 0.002), and/or death (P = 0.010) within 29 days of admission, after adjusting for patients’ demographics, diabetes mellitus comorbidity, and COVID-19 serum markers of severity such as D-dimer, C-reactive protein, and ferritin. Moreover, patients who received interferon beta during their hospital stay had lower plasma IL-19 concentrations (24 pg mL⁻¹) than those who received tocilizumab (39.2 pg mL⁻¹) or corticosteroids (42.5 pg mL⁻¹). Our findings indicate that high saliva IL-19 level was associated with COVID-19 infectivity and disease severity.

Th2 single-cell heterogeneity and clonal distribution at distant sites in helminth-infected mice

Th2 cells provide effector functions in type 2 immune responses to helminths and allergens. Despite knowledge about molecular mechanisms of Th2 cell differentiation, there is little information on Th2 cell heterogeneity and clonal distribution between organs. To address this, we performed combined single-cell transcriptome and T-cell receptor (TCR) clonotype analysis on murine Th2 cells in mesenteric lymph nodes (MLNs) and lung after infection with Nippostrongylus brasiliensis (Nb) as a human hookworm infection model. We find organ-specific expression profiles, but also populations with conserved migration or effector/resident memory signatures that unexpectedly cluster with potentially regulatory Il10^posFoxp3^neg cells. A substantial MLN subpopulation with an interferon response signature suggests a role for interferon signaling in Th2 differentiation or diversification. Further RNA-inferred developmental directions indicate proliferation as a hub for differentiation decisions. Although the TCR repertoire is highly heterogeneous, we identified expanded clones and CDR3 motifs. Clonal relatedness between distant organs confirmed effective exchange of Th2 effector cells, although locally expanded clones dominated the response. We further cloned an Nb-specific TCR from an expanded clone in the lung effector cluster and describe surface markers that distinguish transcriptionally defined clusters. These results provide insights in Th2 cell subset diversity and clonal relatedness in distant organs.

BACH2 in TRegs Limits the Number of Adipose Tissue Regulatory T Cells and Restrains Type 2 Immunity to Fungal Allergens

FoxP3+ regulatory T cells (Tregs) are essential for self-tolerance and moderating tissue-damaging inflammation. Tregs that develop and mature in the thymus are classified as central Tregs or effector Tregs based on whether Tregs predominately inhabit secondary lymphoid organs (central Tregs) or tissues (effector Tregs). By generating mice that are conditionally deficient for Bach2 in peripheral Tregs, we have examined the role of Bach2 in regulating Treg homeostasis and effector functions. Unlike global and T cell-specific Bach2-deficient mice, Treg-specific Bach2 ablation did not result in unprovoked TH2 inflammation in the lungs. However, Bach2 deficiency in Tregs led to augmented expressions of IRF4, BATF, and GATA3 and a significant increase in the accumulation of ST2 (IL-33R)+ve effector Tregs in the spleen and visceral adipose tissue (VAT) but not in the lungs. Enhanced Bach2-deficient Treg numbers in VAT was not linked to hyperresponsiveness to exogenous IL-33 in vivo. Most strikingly, Treg-specific Bach2 deficiency resulted in enhanced fungal protease-induced Type 2 allergic inflammation in the lungs, with no detectable effects on Type 1 responses to systemic or respiratory viral infections. In summary, we ascribe vital roles for Bach2 in peripheral Tregs: as a transcriptional checkpoint to limit precocious differentiation into effector Tregs in lymphoid tissues and as a regulator of the functional program that restrains Type 2 but not Type 1 inflammation in lungs. Results presented in this manuscript implicate dysregulated Tregs in the pathogenesis of airway hypersensitivities, asthma, and other allergic disorders.

Superkine IL-2 and IL-33 Armored CAR T Cells Reshape the Tumor Microenvironment and Reduce Growth of Multiple Solid Tumors

Chimeric-antigen receptor (CAR) T-cell therapy has shown remarkable efficacy against hematologic tumors. Yet, CAR T-cell therapy has had little success against solid tumors due to obstacles presented by the tumor microenvironment (TME) of these cancers. Here, we show that CAR T cells armored with the engineered IL-2 superkine Super2 and IL-33 were able to promote tumor control as a single-agent therapy. IFNγ and perforin were dispensable for the effects of Super2- and IL-33-armored CAR T cells. Super2 and IL-33 synergized to shift leukocyte proportions in the TME and to recruit and activate a broad repertoire of endogenous innate and adaptive immune cells including tumor-specific T cells. However, depletion of CD8+ T cells or NK cells did not disrupt tumor control, suggesting that broad immune activation compensated for loss of individual cell subsets. Thus, we have shown that Super2 and IL-33 CAR T cells can promote antitumor immunity in multiple solid tumor models and can potentially overcome antigen loss, highlighting the potential of this universal CAR T-cell platform for the treatment of solid tumors.

Signaling and functions of interleukin-33 in immune regulation and diseases

Interleukin-33 (IL-33) which belongs to the interleukin-1 (IL-1) family is an alarmin cytokine with critical roles in tissue homeostasis, pathogenic infection, inflammation, allergy and type 2 immunity. IL-33 transmits signals through its receptor IL-33R (also called ST2) which is expressed on the surface of T helper 2 (Th2) cells and group 2 innate lymphoid cells (ILC2s), thus inducing transcription of Th2-associated cytokine genes and host defense against pathogens. Moreover, the IL-33/IL-33R axis is also involved in development of multiple types of immune-related diseases. In this review, we focus on current progress on IL-33-trigggered signaling events, the important functions of IL-33/IL-33R axis in health and diseases as well as the promising therapeutic implications of these findings.

AIM2-inflammasome role in systemic lupus erythematous and rheumatoid arthritis

The inflammasome AIM2 regulates multiple aspects of innate immune functions and serves as a critical mediator of inflammatory responses. AIM2 inflammasome activation leads to the production of pro-inflammatory cytokines, IL-1β and IL-18 and participates triggering a pyroptosis response needed to counteract excessive cell proliferation. In addition, AIM2 expression and activation is wide regulated since alteration in its activity may derived in pathological consequences. Consequently, deregulated AIM2 activation contributes to the pathogenic processes of various inflammatory diseases. In this review, we will discuss the activation and function of AIM2 inflammasome, as well as its contribution in rheumatoid arthritis and systemic lupus erythematous pathology. Finally, we highlight the participation of the AIM2-inflammasome at the level of joint in rheumatoid arthritis and at kidney in systemic lupus erythematous. The development of therapeutic strategies based on modulation of AIM2-inflammasome activity should have a tissue-specific focus.

Ciclopirox inhibits NLRP3 inflammasome activation via protecting mitochondria and ameliorates imiquimod-induced psoriatic inflammation in mice

The maturation and secretion of interleukin-1β (IL-1β) mediated by NLRP3 inflammasome activation plays an important role in the progression of many inflammatory diseases. Inhibition of NLRP3 inflammasome activation may be a promising strategy to treat these inflammation-driven diseases, such as psoriasis. As a broad-spectrum antifungal agent, ciclopirox (CPX) is widely used in the treatment of dermatomycosis. Although CPX has been reported to have anti-inflammatory effects in many studies, there has been little research into its underlying mechanisms. In our study, CPX reduced lipopolysaccharide (LPS)/nigericin-induced NLRP3 inflammasome activation (IC₅₀: 1.684 μM). Mechanistically, CPX upregulated peroxisome proliferator-activated receptor-γ coactivator-1α expression (by 82.7% at 5 μM and 87.5% at 10 μM) to protect mitochondria. Our studies showed that CPX reduced mitochondrial reactive oxygen species production, increased mitochondrial membrane potential, elevated mitochondrial biosynthesis, and up-regulated intracellular adenosine triphosphate level. Furthermore, treatment with CPX promoted the up-regulation of mRNA expression, which involved mitochondrial biosynthesis (NRF1, NRF2, TFAM) and antioxidation (SOD1 and CAT). In addition, CPX ameliorated inflammatory response in imiquimod-induced psoriasis mice. This study provides a potential pharmacological mechanism for CPX to treat psoriasis and other NLRP3-driven inflammatory diseases.

What Is IL-1 for? The Functions of Interleukin-1 Across Evolution

Interleukin-1 is a cytokine with potent inflammatory and immune-amplifying effects, mainly produced by macrophages during defensive reactions. In mammals, IL-1 is a superfamily of eleven structurally similar proteins, all involved in inflammation or its control, which mainly act through binding to specific receptors on the plasma membrane of target cells. IL-1 receptors are also a family of ten structurally similar transmembrane proteins that assemble in heterocomplexes. In addition to their innate immune/inflammatory effects, the physiological role of IL-1 family cytokines seems to be linked to the development of adaptive immunity in vertebrates. We will discuss why IL-1 developed in vertebrates and what is its physiological role, as a basis for understanding when and how it can be involved in the initiation and establishment of pathologies.

IL-37 regulates allergic inflammation by counterbalancing pro-inflammatory IL-1 and IL-33

BACKGROUND

Children with asthma have impaired production of interleukin (IL) 37; in mice, IL-37 reduces hallmarks of experimental allergic asthma (EAA). However, it remains unclear how IL-37 exerts its inhibitory properties in asthma. This study aimed to identify the mechanism(s) by which IL-37 controls allergic inflammation.

METHODS

IL-37 target cells were identified by single-cell RNA-seq of IL-1R5 and IL-1R8. Airway tissues were isolated by laser-capture microdissection and examined by microarray-based gene expression analysis. Mononuclear cells (MNC) and airway epithelial cells (AECs) were isolated and stimulated with allergen, IL-1β, or IL-33 together with recombinant human (rh) IL-37. Wild-type, IL-1R1- and IL-33-deficient mice with EAA were treated with rhIL-37. IL-1β, IL-33, and IL-37 levels were determined in sputum and nasal secretions from adult asthma patients without glucocorticoid therapy.

RESULTS

IL-37 target cells included AECs, T cells, and dendritic cells. In mice with EAA, rhIL-37 led to differential expression of >90 genes induced by IL-1β and IL-33. rhIL-37 reduced production of Th2 cytokines in allergen-activated MNCs from wild-type but not from IL-1R1-deficient mice and inhibited IL-33-induced Th2 cytokine release. Furthermore, rhIL-37 attenuated IL-1β- and IL-33-induced pro-inflammatory mediator expression in murine AEC cultures. In contrast to wild-type mice, hIL-37 had no effect on EAA in IL-1R1- or IL-33-deficient mice. We also observed that expression/production ratios of both IL-1β and IL-33 to IL-37 were dramatically increased in asthma patients compared to healthy controls.

CONCLUSION

IL-37 downregulates allergic airway inflammation by counterbalancing the disease-amplifying effects of IL-1β and IL-33.

TLR3-driven IFN-β antagonizes STAT5-activating cytokines and suppresses innate type 2 response in the lung

BACKGROUND

Group 2 innate lymphoid cells (ILC2s) are involved in type 2 immune responses in mucosal organs and are associated with various allergic diseases in humans. Studies are needed to understand the molecules and pathways that control ILC2s.

OBJECTIVE

The aims of this study were to develop a mouse model that limits the innate type 2 immune response in the lung and to investigate the immunologic mechanisms involved in regulation of lung ILC2s.

METHODS

Naive BALB/c mice were administered various Toll-like receptor agonists and exposed intranasally to the fungal allergen Alternaria alternata. The mechanisms were investigated using gene knockout mice as well as cultures of lung cells and isolated lung ILC2s.

RESULTS

Polyinosinic-polycytidylic acid, or poly (I:C), effectively inhibited innate type 2 response to A alternata. Poly (I:C) promoted production of IFNα, -β, and -γ, and its inhibitory effects were dependent on the IFN-α/β receptor pathway. IFN-β was 100 times more potent than IFN-α at inhibiting type 2 cytokine production by lung ILC2s. Signal transducer and activator of transcription 5 (STAT5)-activating cytokines, including IL-2, IL-7, and thymic stromal lymphopoietin, but not IL-33, promoted survival and proliferation of lung ILC2s in vitro, while IFN-β blocked these effects. Expression of the transcription factor GATA3, which is critical for differentiation and maintenance of ILC2s, was inhibited by IFN-β.

CONCLUSIONS

IFN-β blocks the effects of STAT5-activating cytokines on lung ILC2s and inhibits their survival and effector functions. Administration of IFN-β may provide a new strategy to treat diseases involving ILC2s.

Emerging role of bystander T cell activation in autoimmune diseases

Autoimmune disease is known to be caused by unregulated self-antigen-specific T cells, causing tissue damage. Although antigen specificity is an important mechanism of the adaptive immune system, antigen non-related T cells have been found in the inflamed tissues in various conditions. Bystander T cell activation refers to the activation of T cells without antigen recognition. During an immune response to a pathogen, bystander activation of self-reactive T cells via inflammatory mediators such as cytokines can trigger autoimmune diseases. Other antigen-specific T cells can also be bystander-activated to induce innate immune response resulting in autoimmune disease pathogenesis along with self-antigen-specific T cells. In this review, we summarize previous studies investigating bystander activation of various T cell types (NKT, γδ T cells, MAIT cells, conventional CD4⁺, and CD8⁺ T cells) and discuss the role of innate-like T cell response in autoimmune diseases. In addition, we also review previous findings of bystander T cell function in infection and cancer. A better understanding of bystander-activated T cells versus antigen-stimulated T cells provides a novel insight to control autoimmune disease pathogenesis.

A novel imatinib-upregulated long noncoding RNA plays a critical role in inhibition of tumor growth induced by Abl oncogenes

BACKGROUND

Dysregulation of long noncoding RNAs (lncRNAs) has been linked to various human cancers. Bcr-Abl oncogene that results from a reciprocal translocation between human chromosome 9 and 22, is associated with several hematological malignancies. However, the role of lncRNAs in Bcr-Abl-induced leukemia remains largely unexplored.

METHODS

LncRNA cDNA microarray was employed to identify key lncRNAs involved in Bcr-Abl-mediated cellular transformation. Abl-transformed cell survival and xenografted tumor growth in mice were evaluated to dissect the role of imatinib-upregulated lncRNA 1 (IUR1) in Abl-induced tumorigenesis. Primary bone marrow transformation and in vivo leukemia transplant using lncRNA-IUR1 knockout (KO) mice were further conducted to address the functional relevance of lncRNA-IUR1 in Abl-mediated leukemia. Transcriptome RNA-seq and Western blotting were performed to determine the mechanisms by which lncRNA-IUR1 regulates Bcr-Abl-induced tumorigenesis.

RESULTS

We identified lncRNA-IUR1 as a critical negative regulator of Bcr-Abl-induced tumorigenesis. LncRNA-IUR1 expressed in a very low level in Bcr-Abl-positive cells from chronic myeloid leukemia patients. Interestingly, it was significantly induced in Abl-positive leukemic cells treated by imatinib. Depletion of lncRNA-IUR1 promoted survival of Abl-transformed human leukemic cells in experiments in vitro and xenografted tumor growth in mice, whereas ectopic expression of lncRNA-IUR1 sensitized the cells to apoptosis and suppressed tumor growth. In concert, silencing murine lncRNA-IUR1 in Abl-transformed cells accelerated cell survival and the development of leukemia in mice. Furthermore, lncRNA-IUR1 deficient mice were generated, and we observed that knockout of murine lncRNA-IUR1 facilitated Bcr-Abl-mediated primary bone marrow transformation. Moreover, animal leukemia model revealed that lncRNA-IUR1 deficiency promoted Abl-transformed cell survival and development of leukemia in mice. Mechanistically, we demonstrated that lncRNA-IUR1 suppressed Bcr-Abl-induced tumorigenesis through negatively regulating STAT5-mediated GATA3 expression.

CONCLUSIONS

These findings unveil an inhibitory role of lncRNA-IUR1 in Abl-mediated cellular transformation, and provide new insights into molecular mechanisms underlying Abl-induced leukemogenesis.

Significance of bystander T cell activation in microbial infection

During microbial infection, pre-existing memory CD8⁺ T cells that are not specific for the infecting pathogens can be activated by cytokines without cognate antigens, termed bystander activation. Studies in mouse models and human patients demonstrate bystander activation of memory CD8⁺ T cells, which exerts either protective or detrimental effects on the host, depending on the infection model or disease. Research has elucidated mechanisms underlying the bystander activation of CD8⁺ T cells in terms of the responsible cytokines and the effector mechanisms of bystander-activated CD8⁺ T cells. In this Review, we describe the history of research on bystander CD8⁺ T cell activation as well as evidence of bystander activation. We also discuss the mechanisms and immunopathological roles of bystander activation in various microbial infections.

Innate control of adaptive immunity and adaptive instruction of innate immunity: bi-directional flow of information

The ability of the innate and adaptive immune systems to communicate with each other is central to protective immune responses and maintenance of host health. Myeloid cells of the innate immune system are able to sense microbial ligands, perturbations in cellular homeostasis, and virulence factors, thereby allowing them to relay distinct pathogen-specific information to naïve T cells in the form of pathogen-derived peptides and a unique cytokine milieu. Once primed, effector T helper cells produce lineage-defining cytokines to help combat the original pathogen, and a subset of these cells persist as memory or effector-memory populations. These memory T cells then play a dual role in host protection by not only responding rapidly to reinfection, but by also directly instructing myeloid cells to express licensing cytokines. This means there is a bi-directional flow of information first from the innate to the adaptive immune system, and then from the adaptive back to innate immune system. Here, we focus on how signals, first from pathogens and then from primed effector and memory T cells, are integrated by myeloid cells and its consequences for protective immunity or systemic inflammation.