T-bet inhibits both TH2 cell-mediated eosinophil recruitment and TH17 cell-mediated neutrophil recruitment into the airways

Circular RNAs in human diseases

Circular RNAs (circRNAs) are a unique class of RNA molecules formed through back-splicing rather than linear splicing. As an emerging field in molecular biology, circRNAs have garnered significant attention due to their distinct structure and potential functional implications. A comprehensive understanding of circRNAs' functions and potential clinical applications remains elusive despite accumulating evidence of their involvement in disease pathogenesis. Recent research highlights their significant roles in various human diseases, but comprehensive reviews on their functions and applications remain scarce. This review provides an in-depth examination of circRNAs, focusing first on their involvement in non-neoplastic diseases such as respiratory, endocrine, metabolic, musculoskeletal, cardiovascular, and renal disorders. We then explore their roles in tumors, with particular emphasis on exosomal circular RNAs, which are crucial for cancer initiation, progression, and resistance to treatment. By detailing their biogenesis, functions, and impact on disease mechanisms, this review underscores the potential of circRNAs as diagnostic biomarkers and therapeutic targets. The review not only enhances our understanding of circRNAs' roles in specific diseases and tumor types but also highlights their potential as novel diagnostic and therapeutic tools, thereby paving the way for future clinical investigations and potential therapeutic interventions.

Nrf2 Deficiency Accelerates IL-17-Dependent Neutrophilic Airway Inflammation in Asthmatic Mice

Asthma is a heterogeneous disease that can be broadly classified into type 2, which is primarily steroid-sensitive and eosinophilic, and non-type 2, which is primarily steroid-resistant and neutrophilic. While the mechanisms leading to the development of molecular-targeted therapies for type 2 asthma are being elucidated, much remains to be learned about non-type 2 asthma. To investigate the role of oxidative stress in refractory allergic airway inflammation, we compared asthma models generated by immunizing wild-type and nuclear factor erythroid-2-related factor 2 (Nrf2)-deficient mice with the house dust mite antigen. Both asthma models had similar levels of airway inflammation and hyperresponsiveness, but the Nrf2-deficient mice had increased oxidative stress and exacerbated neutrophilic airway inflammation compared with the wild-type mice. Type 2 cytokines and the expression of GATA3, a transcription factor that is important for Th2 cell differentiation, had decreased in Nrf2-deficient mice compared with the wild-type mice, whereas helper T (Th) 17 cytokines and the expression of RORγt, which is important for Th17 cell differentiation, had increased. Furthermore, the neutrophilic airway inflammation caused by Nrf2 deficiency was ameliorated by interleukin (IL)-17 neutralization. We have concluded that the disruption of the Nrf2-mediated antioxidant defense system contributed to the induction of Th17 differentiation and exacerbated allergic neutrophilic airway inflammation.

Circular RNAs: emerging players in asthma and COPD

Circular RNAs (circRNAs) belong to a unique class of endogenously expressed non-protein-coding RNAs with a distinct circularized structure, characterized by the absence of 5'-cap and 3'-polyadenylate ends. They are generally formed through back-splicing from pre-mRNAs. They serve as regulators of transcription and splicing, and act as sponges for microRNAs (miRNAs) and RNA-binding proteins, thereby modulating the expression of target genes. As a result, they exert a substantial impact on a diverse array of cellular and biological processes, including cell proliferation, migration, inflammation, and oxidative stress. Asthma and COPD are chronic airway conditions that currently have no cure. In recent years, emerging evidence suggests that altered expression of circRNAs in airway, bronchial and immune cells is involved in asthma and COPD pathogenesis. Studies exploring circRNA dysregulation in asthma have showcased their involvement in regulating the proliferation, migration, and inflammation of airway smooth muscle and bronchial epithelial cells, as well as impacting goblet cell metaplasia, Th2 cell differentiation, and macrophage activation, primarily through interactions with miRNAs. Similarly, in COPD, circRNAs have shown altered expression patterns in the blood and lungs of patients, and these changes have been linked to modulating inflammation, oxidative stress, and airway remodeling in preclinical models. Furthermore, certain circRNAs have demonstrated promising potential as diagnostic and prognostic biomarkers for both asthma and COPD. This review delves into the current understanding of the function and molecular mechanisms of circRNAs in asthma and COPD, along with exploring their potential as biomarkers in these respiratory conditions.

CRL4B complex-mediated H2AK119 monoubiquitination restrains Th1 and Th2 cell differentiation

CD4+ T helper (Th) cell differentiation is regulated by lineage-specific expression of transcription factors, which is tightly associated with epigenetic modifications, including histone acetylation and methylation. However, the factors regulating histone modifications involved in Th cell differentiation remain largely unknown. We herein demonstrated a critical role of Cullin 4B (CUL4B) in restricting Th1 and Th2 cell differentiation. CUL4B, which is assembled into the CUL4B-RING E3 ligase (CRL4B) complex, participates in various physiological and developmental processes through epigenetic repression of transcription. Depletion of Cul4b in CD4+ T cells enhanced Th1 and Th2 cell differentiation. In vivo, an aggravated Th2 response caused by the absence of CUL4B was observed in a murine asthma model. Mechanistically, the CRL4B complex promoted monoubiquitination at H2AK119 (H2AK119ub1) and polycomb repressive complex 2 (PRC2)-mediated trimethylation at H3K27 (H3K27me3) at Tbx21 and Maf and consequently repressed their expression during Th cell differentiation. Our study suggests that CRL4B complex-mediated H2AK119ub1 deposition functions to prevent the aberrant expression of Th1 and Th2 lineage-specific genes.

The efficacy and safety of Yupingfeng Powder with variation in the treatment of allergic rhinitis: Study protocol for a randomized, double-blind, placebo-controlled trial

Background: Allergic rhinitis (AR) is an upper airways chronic inflammatory disease mediated by IgE, which affects 10%-20% of the population. The mainstay for allergic rhinitis nowadays include steroids and antihistamines, but their effects are less than ideal. Many patients therefore seek Chinese medicine for treatment and Yupingfeng Powder is one of the most common formulae prescribed. In this study, we aim to investigate the efficacy and safety of Yupingfeng Powder with variation for the treatment of allergic rhinitis. Study design: This is a double-blind, randomized, placebo-controlled trial. A 2-week screening period will be implemented, and then eligible subjects with allergic rhinitis will receive interventions of either "Yupingfeng Powder with variation" granules or placebo granules for 8 weeks, followed by post treatment visits at weeks 12 and 16. The change in the Total Nasal Symptom Score (TNSS) will be used as the primary outcome. Discussion: This trail will evaluate the efficacy and safety of Yupingfeng Powder in treating allergic rhinitis. The study may provide the solid evidence of Yupingfeng Powder with variation can produce better clinical efficacy than the placebo granules. Trial registration: ClinicalTrials.gov, identifier NCT04976023.

High Th2 cytokine levels and upper airway inflammation in human inherited T-bet deficiency

We have described a child suffering from Mendelian susceptibility to mycobacterial disease (MSMD) due to autosomal recessive, complete T-bet deficiency, which impairs IFN-γ production by innate and innate-like adaptive, but not mycobacterial-reactive purely adaptive, lymphocytes. Here, we explore the persistent upper airway inflammation (UAI) and blood eosinophilia of this patient. Unlike wild-type (WT) T-bet, the mutant form of T-bet from this patient did not inhibit the production of Th2 cytokines, including IL-4, IL-5, IL-9, and IL-13, when overexpressed in T helper 2 (Th2) cells. Moreover, Herpesvirus saimiri-immortalized T cells from the patient produced abnormally large amounts of Th2 cytokines, and the patient had markedly high plasma IL-5 and IL-13 concentrations. Finally, the patient's CD4+ αβ T cells produced most of the Th2 cytokines in response to chronic stimulation, regardless of their antigen specificities, a phenotype reversed by the expression of WT T-bet. T-bet deficiency thus underlies the excessive production of Th2 cytokines, particularly IL-5 and IL-13, by CD4+ αβ T cells, causing blood eosinophilia and UAI. The MSMD of this patient results from defective IFN-γ production by innate and innate-like adaptive lymphocytes, whereas the UAI and eosinophilia result from excessive Th2 cytokine production by adaptive CD4+ αβ T lymphocytes.

T-bet and STAT6 Coordinately Suppress the Development of IL-9-Mediated Atopic Dermatitis-Like Skin Inflammation in Mice

T-bet and signal transducer and activator of transcription (STAT) 6 are critical factors for helper T-cell differentiation in humans and mice. Additionally, polymorphisms in TBX21 (T-bet) and STAT6 are associated with the susceptibility of allergic diseases. However, precise mechanisms of the reciprocal regulation between T-bet and STAT6 in allergy remain unclear. To determine the reciprocal regulation in vivo, we investigated the phenotype of T-bet/STAT6 double-deficient (T-bet^-/- STAT6^-/-) mice. Unexpectedly, T-bet^-/- STAT6^-/- mice but not T-bet^-/- mice or STAT6^-/- mice spontaneously developed severe dermatitis. Not only eosinophils and mast cells but also CD4⁺ T cells infiltrated into the skin of T-bet^-/- STAT6^-/- mice. Adoptive transfer of CD4⁺ T cells of T-bet^-/- STAT6^-/- mice into severe combined immunodeficient mice induced the accumulation of eosinophils and mast cells in the skin, whereas depletion of CD4⁺ T cells ameliorated the dermatitis in T-bet^-/- STAT6^-/- mice. Comprehensive transcriptome analyses revealed that IL-9 expression was enhanced in T-bet^-/- STAT6^-/- CD4⁺ T cells. Indeed, IL-9 neutralization ameliorated the dermatitis in T-bet^-/- STAT6^-/- mice. T-bet^-/- STAT6^-/- CD4⁺ T cells expressed functional thymic stromal lymphopoietin receptors and produced large amounts of IL-9 on thymic stromal lymphopoietin stimulation. These results indicate that T-bet and STAT6 coordinately suppress atopic dermatitis-like skin inflammation, possibly by inhibiting thymic stromal lymphopoietin-dependent IL-9 production in CD4⁺ T cells.

Towards new TB vaccines

Mycobacterium tuberculosis remains the leading cause of death attributed to a single infectious organism. Bacillus Calmette-Guerin (BCG), the standard vaccine against M. tuberculosis, is thought to prevent only 5% of all vaccine-preventable deaths due to tuberculosis, thus an alternative vaccine is required. One of the principal barriers to vaccine development against M. tuberculosis is the complexity of the immune response to infection, with uncertainty as to what constitutes an immunological correlate of protection. In this paper, we seek to give an overview of the immunology of M. tuberculosis infection, and by doing so, investigate possible targets of vaccine development. This encompasses the innate, adaptive, mucosal and humoral immune systems. Though MVA85A did not improve protection compared with BCG alone in a large-scale clinical trial, the correlates of protection this has revealed, in addition to promising results from candidate such as VPM1002, M72/ASO1E and H56:IC31 point to a brighter future in the field of TB vaccine development.

Programmed T cell differentiation: Implications for transplantation

While T cells play a critical role in protective immunity against infection, they are also responsible for graft rejection in the setting of transplantation. T cell differentiation is regulated by both intrinsic transcriptional pathways as well as extrinsic factors such as antigen encounter and the cytokine milieu. Herein, we review recent discoveries in the transcriptional regulation of T cell differentiation and their impact on the field of transplantation. Recent studies uncovering context-dependent differentiation programs that differ in the setting of infection or transplantation will also be discussed. Understanding the key transcriptional pathways that underlie T cell responses in transplantation has important clinical implications, including development of novel therapeutic agents to mitigate graft rejection.

Asthma phenotypes and T-bet protein expression in cells treated with Fluticasone Furoate/Vilanterol

Asthma is a complex disease with diverse clinical manifestations ranging from mild to severe. Despite existing guidelines for asthma recognition and treatment, still a proportion of patients stay uncontrolled. Combinational therapy which comprises inhaled corticosteroids (ICS) and a long acting B2 adrenreceptor agonist (LABA) has been suggested to control asthma. In this study T-bet expression was attested in CD4 T cells treated with Fluticasone Furoate (FF), Vilanterol (V) and FF/V combination in severe asthmatic patients compared to patients with moderate asthma and healthy controls using Immunocytochemistry (ICC). First, CD4 T cells were isolated from PBMCs of 12 patients and controls using CD4 T cell isolation kit. Subsequently, isolated CD4 T cells were cultured with FF, V and FF/V for 1 h. To accomplish ICC, cells were incubated with anti-T-bet antibody, and then stained with HRP-bound secondary antibody. T-bet expression was evaluated using light microscopy. Statistical analyses were performed using R 3.5.2 software and visualized by ggplot2 3.1.0 package. Significant increasing in T-bet expression was seen in CD4 T cells from patients with moderate asthma treated with FF and FF/V. Suggesting conclusion would be distinct mechanisms responsible for severe asthma and moderate asthma in the patients and the needs for novel therapies. Further molecular studies in different asthma phenotypes would be instructive for asthma treatment.

Hsa_circ_0005519 increases IL-13/IL-6 by regulating hsa-let-7a-5p in CD4+ T cells to affect asthma

BACKGROUND

Circular RNAs (circRNAs) are a class of non-coding RNAs that could serve as novel biomarkers for the diagnosis and treatment of diseases. We hypothesized that circRNAs of CD4⁺ T cells are involved in asthma.

OBJECTIVE

In this study, we investigated the circRNA expression profile and the possible mechanism by which hsa_circ_0005519 participates in asthma.

METHODS

The expression profiles of circRNAs in CD4⁺ T cells were revealed by circRNA microarray. Hsa_circ_0005519 expression in CD4⁺ T cells was confirmed in asthmatic patients (n = 65) and healthy subjects (n = 30). Hsa-let-7a-5p, the target of hsa_circ_0005519, was predicted by online algorithms and verified by a dual-luciferase reporter assay. Correlation assays between the expression of hsa_circ_0005519 and hsa-let-7a-5p, the mRNA levels of interleukin (IL)-13 and IL-6 in CD4⁺ T cells, and the clinical characteristics of asthmatic patients were performed. The role of hsa_circ_0005519 in proinflammatory cytokine expression was investigated in CD4⁺ T cells from asthmatic patients in vitro. Hsa_circ_0005519 expression in PBMCs was determined in another cohort including 30 asthmatic patients and 24 controls. Correlation assays of hsa_circ_0005519 expressions between CD4⁺ T cells and PBMCs were performed.

RESULTS

Hsa_circ_0005519 was up-regulated and negatively correlated with hsa-let-7a-5p expression in CD4⁺ T cells of asthmatic patients. Both the fraction of exhaled nitric oxide (FeNO) and the peripheral blood eosinophil ratio were positively correlated with hsa_circ_0005519 expression in CD4⁺ T cells. These outcomes were also different in asthmatic patients with low vs high hsa_circ_0005519 levels. Hsa_circ_0005519 expressions between CD4⁺ T cells and PBMCs were concordant in asthmatic patients. Mechanistically, hsa_circ_0005519 might bind to hsa-let-7a-5p and relieve suppression for IL-13/IL-6 in CD4⁺ T cells.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data suggest that hsa_circ_0005519 may induce IL-13 and IL-6 expression by regulating hsa-let-7a-5p in CD4⁺ T cells to affect asthma. And hsa_circ_0005519 may be a potential biomarker of asthma.

Effect of ginger extract on expression of GATA3, T-bet and ROR-γt in peripheral blood mononuclear cells of patients with Allergic Asthma

INTRODUCTION AND OBJECTIVES

Allergic asthma is a chronic inflammatory disorder of the airways. Th1, Th2 and Th17 cells are the main cells involved in the pathophysiology of asthma. The function of these cells is affected by T-bet, GATA3 and RORγt transcription factors (respectively). Therefore, the aim of this study was to evaluate the effect of ginger (officinal Roscoe) extract on the expression of T-bet, GATA-3 and ROR-γ in peripheral blood mononuclear cells (PBMC) of asthmatic patients, in comparison with healthy volunteers as controls.

MATERIALS AND METHODS

In this case-control study, a total of 50 individuals including 25 patients with severe, moderate and mild allergic asthma and 25 unrelated healthy controls were involved. The PBMCs were isolated and divided into four groups: negative control, two positive controls (Budesonide and PHA) and ginger-extract treated group. After cell treatment and incubation for 48h, PBMCs were isolated and cDNA was synthesized. Gene expressions of T-bet, GATA3 and ROR-γt were evaluated by Real-time PCR.

RESULTS

According to the results of this study, hydroalcoholic extract of ginger could reduce the expression of GATA-3, ROR-γt, and T-bet in PBMCs of asthmatic patients in comparison with untreated PBMCs (P values=0.001, 0.001, and 0.002, respectively). It was also shown that the ginger extract could affect T-bet/GATA-3, T-bet/ROR-γt, and ROR-γt/GATA-3 expression ratios.

CONCLUSIONS

This study showed that the use of ginger extract could control asthma and decrease the severity of this disease by affecting the main cells involving the symptoms of asthma in the airways.

Sublingual administration of liposomes enclosing alpha-galactosylceramide as an effective adjuvant of allergen immunotherapy in a murine model of allergic rhinitis

BACKGROUND

Sublingual immunotherapy (SLIT) is an established efficacious approach for the treatment of allergic rhinitis (AR). However, SLIT requires a long administration period to establish stable and adequate responses. This study investigated the efficacy of the sublingual administration of an allergen with liposomes enclosing α-GalCer (α-GC-liposome) as a potential adjuvant in mice with AR.

METHODS

Mice with AR induced by OVA received the sublingual administration of OVA, α-GC-liposomes, or OVA plus α-GC-liposomes for 7 days. After nasal re-challenge with OVA, nasal symptoms were evaluated. The serum levels of OVA-specific Ig, the cytokine production of CD4⁺ T cells in the cultures of cervical lymph node (CLN) cells, and the gene expression of CLNs were analyzed.

RESULTS

Although IL-4, IL-5 and IL-13 production from CD4⁺ T cells in CLN cells was significantly inhibited by the sublingual administration of OVA alone in mice with AR induced by OVA, their nasal symptoms were not significantly diminished. However, the combined sublingual administration of α-GC-liposomes and OVA completely suppressed nasal symptoms, downregulated Th2 and Th17 type cytokine production in CD4⁺ T cells as well as Th2 and Th17 gene expressions, and upregulated Th1 type cytokine production as well as Th1 gene expressions in CLN cells. Additionally, the serum levels of specific IgG2a were promoted, and specific IgE and IgG1 were inhibited.

CONCLUSIONS

Our findings suggest that the sublingual administration of an allergen with α-GC-liposomes as an adjuvant might increase the therapeutic efficacy and effectiveness of this treatment method.

The relationship between IL-17A and IL-22 expression and clinical severity in patients with moderate/severe persistent allergic rhinitis

PURPOSE

Several reactions leading to numerous effects are regulated by IL-22. However, the relationship between IL-22 and immunopathogensis of allergic rhinitis (AR) has been rarely investigated. The aim of the present study was to investigate the levels of IL-22 and IL-17A in AR patients and their association with clinical severity of persistent allergic rhinitis (PAR).

MATERIALS AND METHODS

Thirty mild persistent allergic rhinitis (M PAR) patients, thirty moderate/severe persistent allergic rhinitis (M/S PAR) patients, and thirty healthy controls were enrolled in this study. Local production of IL-22 and IL-17A in PAR patients and healthy controls' nasal mucosa was examined by immunohistochemistry (IHC) and real-time polymerase chain reaction (RT-PCR) techniques. Serum levels of IL-22, IL-17A, specific immunoglobulin E (sIgE), and total IgE (tIgE) in PAR patients and healthy controls were determined by ELISA. In addition, blood eosinophil, nasal eosinophils per field, and total nasal syndrome score (TNSS) were also assessed.

RESULTS

In comparison with healthy controls, production of IL-22 and IL-17A in M/S PAR patients increased significantly. Furthermore, serum levels as well as the mean number of IL-22+ and IL-17A+ cells in nasal mucosa correlated with sIgE, nasal eosinophil count, and TNSS.

CONCLUSION

The results of the present study provide the first evidence that local production of IL-22 might be expressed in PAR patients. The expression of IL-22 and IL-17A, and their correlations with clinical parameters in PAR patients suggest the role of these cytokines in the events involved in the development of PAR.

The Clinical Significance of Changes in the Expression Levels of MicroRNA-1 and Inflammatory Factors in the Peripheral Blood of Children with Acute-Stage Asthma

This study assessed the changes and clinical significance of microRNA-1 (miR-1) and inflammatory factors in the peripheral blood of children with acute-stage asthma. 100 children with acute-stage asthma (study group) and 100 healthy children (control group) were enrolled. For all enrolled children, the peripheral blood levels of miR-1, interleukin-4 (IL-4), IL-5, IL-8, tumor necrosis factor-alpha (TNF-α), and interferon-γ (IFN-γ) were measured. The relative expression levels of miR-1 and IFN-γ in the peripheral blood of children in the study group were significantly lower than those in the control group, whereas expression levels of IL-4, IL-5, IL-8, and TNF-α were significantly higher. Moreover, these levels changed to a greater extent in patients with severe disease (P < 0.05). Further analyses showed that the miR-1 expression level positively correlated with IFN-γ and negatively correlated with IL-4, IL-5, IL-8, and TNF-α expression levels (P < 0.05). ROC curve analysis to identify diagnostic specificity and sensitivity showed that, for diagnosing exacerbation in asthma, the area under the curve (AUC) for miR-1 was the highest (AUC = 0.900, P < 0.05) of all tested markers; this held true for diagnosing severe asthma as well (AUC = 0.977, P < 0.05). Compared to healthy children, children with acute-stage asthma had a low miR-1 expression level and a Th1/Th2 imbalance in their peripheral blood. The changes were closely related, became more exaggerated with an increase in disease severity, and could be used as auxiliary variables for diagnosing asthma exacerbation and evaluating disease severity.

Are ILC2s Jekyll and Hyde in airway inflammation?

Asthma is a complex heterogeneous disease of the airways characterized by lung inflammation, airway hyperreactivity (AHR), mucus overproduction, and remodeling of the airways. Group 2 innate lymphoid cells (ILC2s) play a crucial role in the initiation and propagation of type 2 inflammatory programs in allergic asthma models, independent of adaptive immunity. In response to allergen, helminths or viral infection, damaged airway epithelial cells secrete IL-33, IL-25, and thymic stromal lymphopoietin (TSLP), which activate ILC2s to produce type 2 cytokines such as IL-5, IL-13, and IL-9. Furthermore, ILC2s coordinate a network of cellular responses and interact with numerous cell types to propagate the inflammatory response and repair lung damage. ILC2s display functional plasticity in distinct asthma phenotypes, enabling them to respond to very different immune microenvironments. Thus, in the context of non-allergic asthma, triggered by exposure to environmental factors, ILC2s transdifferentiate to ILC1-like cells and activate type 1 inflammatory programs in the lung. In this review, we summarize accumulating evidence on the heterogeneity, plasticity, regulatory mechanisms, and pleiotropic roles of ILC2s in allergic inflammation as well as mechanisms for their suppression in the airways.

Allergic airway inflammation: key players beyond the Th2 cell pathway

Allergic asthma is characterized by eosinophilic airway inflammation, mucus hyperproduction, and airway hyperreactivity, causing reversible airway obstruction. Accumulating evidence indicates that antigen-specific Th2 cells and their cytokines such as IL-4, IL-5, and IL-13 orchestrate these pathognomonic features of asthma. However, over the past decade, the understanding of asthma pathogenesis has made a significant shift from a Th2 cell-dependent, IgE-mediated disease to a more complicated heterogeneous disease. Recent studies clearly show that not only Th2 cytokines but also other T cell-related cytokines such as IL-17A and IL-22 as well as epithelial cell cytokines such as IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) are involved in the pathogenesis of asthma. In this review, we focus on the roles of these players beyond Th2 pathways in the pathogenesis of asthma.

AMIGO2 modulates T cell functions and its deficiency in mice ameliorates experimental autoimmune encephalomyelitis

The immune function of AMIGO2 is currently unknown. Here, we revealed novel roles of AMIGO2 in modulating T-cell functions and EAE using Amigo2-knockout (AMG2KO) mice. Amigo2 was abundantly expressed by murine T helper (Th) cells. Its deficiency impaired transplanted T-cell infiltration into the secondary lymphoid organs and dampened Th-cell activation, but promoted splenic Th-cell proliferation and abundancy therein. AMG2KO Th cells had respectively elevated T-bet in Th1- and GATA-3 in Th2-lineage during early Th-cell differentiation, accompanied with increased IFN-γ and IL-10 but decreased IL-17A production. AMG2KO mice exhibited ameliorated EAE, dampened spinal T-cell accumulation, decreased serum IL-17A levels and enhanced splenic IL-10 production. Adoptive transfer of encephalitogenic AMG2KO T cells induced milder EAE and dampened spinal Th-cell accumulation and Tnf expression. Mechanistically, Amigo2-overexpression in 293T cells dampened NF-kB transcriptional activity, while Amigo2-deficiency enhanced Akt but suppressed GSK-3β phosphorylation and promoted nuclear translocations of NF-kB and NFAT1 in Th-cells. Collectively, our data demonstrate that AMIGO2 is important in regulating T-cell functions and EAE, and may be harnessed as a potential therapeutic target for multiple sclerosis.

Pulmonary but Not Subcutaneous Delivery of BCG Vaccine Confers Protection to Tuberculosis-Susceptible Mice by an Interleukin 17-Dependent Mechanism

Some of the most promising novel tuberculosis vaccine strategies currently under development are based on respiratory vaccination, mimicking the natural route of infection. In this work, we have compared pulmonary and subcutaneous delivery of BCG vaccine in the tuberculosis-susceptible DBA/2 mouse strain, a model in which parenterally administered BCG vaccine does not protect against tuberculosis. Our data show that intranasally but not subcutaneously administered BCG confers robust protection against pulmonary tuberculosis challenge. In addition, our results indicate that pulmonary vaccination triggers a Mycobacterium tuberculosis-specific mucosal immune response orchestrated by interleukin 17A (IL-17A). Thus, IL-17A neutralization in vivo reduces protection and abrogates M. tuberculosis-specific immunoglobulin A (IgA) secretion to respiratory airways and lung expression of polymeric immunoglobulin receptor induced following intranasal vaccination. Together, our results demonstrate that pulmonary delivery of BCG can overcome the lack of protection observed when BCG is given parenterally, suggesting that respiratory tuberculosis vaccines could have an advantage in tuberculosis-endemic countries, where intradermally administered BCG has inefficient effectiveness against pulmonary tuberculosis.

Phenotypic differences of CD4(+) T cells in response to red blood cell immunization in transfused sickle cell disease patients

Alloimmunization against red blood cells (RBCs) is the main immunological risk associated with transfusion in patients with sickle cell disease (SCD). However, about 50-70% of SCD patients never get immunized despite frequent transfusion. In murine models, CD4(+) T cells play a key role in RBC alloimmunization. We therefore explored and compared the CD4(+) T-cell phenotypes and functions between a group of SCD patients (n = 11) who never became immunized despite a high transfusion regimen and a group of SCD patients (n = 10) who had become immunized (at least against Kidd antigen b) after a low transfusion regimen. We studied markers of CD4(+) T-cell function, including TLR, that directly control lymphocyte function, and their spontaneous cytokine production. We also tested responders for the cytokine profile in response to Kidd antigen b peptides. Low TLR2/TLR3 expression and, unexpectedly, strong expression of CD40 on CD4(+) T cells were associated with the nonresponder status, whereas spontaneous expression of IL-10 by CD4(+) T cells and weak Tbet expression were associated with the responder status. A Th17 profile was predominant in responders when stimulated by Jb(k) . These findings implicate CD4(+) T cells in alloimmunization in humans and suggest that they may be exploited to differentiate responders from nonresponders.

IL-10 and regulatory T cells cooperate in allergen-specific immunotherapy to ameliorate allergic asthma

Human studies demonstrated that allergen-specific immunotherapy (IT) represents an effective treatment for allergic diseases. IT involves repeated administration of the sensitizing allergen, indicating a crucial contribution of T cells to its medicinal benefit. However, the underlying mechanisms of IT, especially in a chronic disease, are far from being definitive. In the current study, we sought to elucidate the suppressive mechanisms of IT in a mouse model of chronic allergic asthma. OVA-sensitized mice were challenged with OVA or PBS for 4 wk. After development of chronic airway inflammation, mice received OVA-specific IT or placebo alternately to airway challenge for 3 wk. To analyze the T cell-mediated mechanisms underlying IT in vivo, we elaborated the role of T-bet-expressing Th1 cells, T cell-derived IL-10, and Ag-specific thymic as well as peripherally induced Foxp3(+) regulatory T (Treg) cells. IT ameliorated airway hyperresponsiveness and airway inflammation in a chronic asthma model. Of note, IT even resulted in a regression of structural changes in the airways following chronic inhaled allergen exposure. Concomitantly, IT induced Th1 cells, Foxp3(+), and IL-10-producing Treg cells. Detailed analyses revealed that thymic Treg cells crucially contribute to the effectiveness of IT by promoting IL-10 production in Foxp3-negative T cells. Together with the peripherally induced Ag-specific Foxp3(+) Treg cells, thymic Foxp3(+) Treg cells orchestrate the curative mechanisms of IT. Taken together, we demonstrate that IT is effective in a chronic allergic disease and dependent on IL-10 and thymic as well as peripherally induced Ag-specific Treg cells.

Wheezing and itching: The requirement for STAT proteins in allergic inflammation

The development of allergic inflammation requires the orchestration of gene expression from the inflamed tissue and from the infiltrating immune cells. Since many of the cytokines that promote allergic inflammation signal through hematopoietin family receptors, the Signal Transducer and Activator of Transcription (STAT) family have obligate roles in pro-allergic cytokine-induced gene regulation in multiple cell types. In this review, we summarize work defining the contribution of each of the STAT family members to the development of allergic inflammation, using data from mouse models of allergic inflammation, studies on patient samples and correlations with single nucleotide polymorphisms in STAT genes.

STAT4 deficiency fails to induce lung Th2 or Th17 immunity following primary or secondary respiratory syncytial virus (RSV) challenge but enhances the lung RSV-specific CD8+ T cell immune response to secondary challenge

Immune-mediated lung injury is a hallmark of lower respiratory tract illness caused by respiratory syncytial virus (RSV). STAT4 plays a critical role in CD4+ Th1 lineage differentiation and gamma interferon (IFN-γ) protein expression by CD4+ T cells. As CD4+ Th1 differentiation is associated with negative regulation of CD4+ Th2 and Th17 differentiation, we hypothesized that RSV infection of STAT4-/- mice would result in enhanced lung Th2 and Th17 inflammation and impaired lung Th1 inflammation compared to wild-type (WT) mice. We performed primary and secondary RSV challenges in WT and STAT4-/- mice and used STAT1-/- mice as a positive control for the development of RSV-specific lung Th2 and Th17 inflammation during primary challenge. Primary RSV challenge of STAT4-/- mice resulted in decreased T-bet and IFN-γ expression levels in CD4+ T cells compared to those of WT mice. Lung Th2 and Th17 inflammation did not develop in primary RSV-challenged STAT4-/- mice. Decreased IFN-γ expression by NK cells, CD4+ T cells, and CD8+ T cells was associated with attenuated weight loss and enhanced viral clearance with primary challenge in STAT4-/- mice compared to WT mice. Following secondary challenge, WT and STAT4-/- mice also did not develop lung Th2 or Th17 inflammation. In contrast to primary challenge, secondary RSV challenge of STAT4-/- mice resulted in enhanced weight loss, an increased lung IFN-γ expression level, and an increased lung RSV-specific CD8+ T cell response compared to those of WT mice. These data demonstrate that STAT4 regulates the RSV-specific CD8+ T cell response to secondary infection but does not independently regulate lung Th2 or Th17 immune responses to RSV challenge.

IMPORTANCE

STAT4 is a protein critical for both innate and adaptive immune responses to viral infection. Our results show that STAT4 regulates the immune response to primary and secondary challenge with RSV but does not restrain RSV-induced lung Th2 or Th17 immune responses. These findings suggest that STAT4 expression may influence lung immunity and severity of illness following primary and secondary RSV infections.

Lymphocyte-based model systems for allergy research: a historic overview

During the last decades, a multitude of studies applying distinct in vitro and in vivo model systems have contributed greatly to our better understanding of the initiation and regulation of inflammatory processes leading to allergic diseases. Over the years, it has become evident that among lymphocytes, not only IgE-producing B cells and allergy-orchestrating CD4(+) helper cells but also cytotoxic CD8(+) T cells, γδ-T cells and innate lymphoid cells, as well as regulatory lymphocytes, might critically shape the immune response towards usually innocuous allergens. In this review, we provide a historic overview of pioneering work leading to the establishment of important lymphocyte-based model systems for allergy research. Moreover, we contrast the original findings with our currently more refined knowledge to appreciate the actual validity of the respective models and to reassess the conclusions obtained from them. Conflicting studies and interpretations are identified and discussed. The tables are intended to provide an easy overview of the field not only for scientists newly entering the field but also for the broader readership interested in updating their knowledge. Along those lines, herein we discuss in vitro and in vivo approaches to the investigation of lymphocyte effector cell activation, polarization and regulation, and describe depletion and adoptive transfer models along with gene knockout and transgenic (tg) methodologies. In addition, novel attempts to establish humanized T cell antigen receptor tg mouse models for allergy research are described and discussed.

Leptin deficiency impairs maturation of dendritic cells and enhances induction of regulatory T and Th17 cells

Leptin is an adipose-secreted hormone that plays an important role in both metabolism and immunity. Leptin has been shown to induce Th1-cell polarization and inhibit Th2-cell responses. Additionally, leptin induces Th17-cell responses, inhibits regulatory T (Treg) cells and modulates autoimmune diseases. Here, we investigated whether leptin mediates its activity on T cells by influencing dendritic cells (DCs) to promote Th17 and Treg-cell immune responses in mice. We observed that leptin deficiency (i) reduced the expression of DC maturation markers, (ii) decreased DC production of IL-12, TNF-α, and IL-6, (iii) increased DC production of TGF-β, and (iv) limited the capacity of DCs to induce syngeneic CD4(+) T-cell proliferation. As a consequence of this unique phenotype, DCs generated under leptin-free conditions induced Treg or TH 17 cells more efficiently than DCs generated in the presence of leptin. These data indicate important roles for leptin in DC homeostasis and the initiation and maintenance of inflammatory and regulatory immune responses by DCs.

Genome-wide regulatory analysis reveals that T-bet controls Th17 lineage differentiation through direct suppression of IRF4

The complex relationship between Th1 and Th17 cells is incompletely understood. The transcription factor T-bet is best known as the master regulator of Th1 lineage commitment. However, attention is now focused on the repression of alternate T cell subsets mediated by T-bet, particularly the Th17 lineage. It has recently been suggested that pathogenic Th17 cells express T-bet and are dependent on IL-23. However, T-bet has previously been shown to be a negative regulator of Th17 cells. We have taken an unbiased approach to determine the functional impact of T-bet on Th17 lineage commitment. Genome-wide analysis of functional T-bet binding sites provides an improved understanding of the transcriptional regulation mediated by T-bet, and suggests novel mechanisms by which T-bet regulates Th cell differentiation. Specifically, we show that T-bet negatively regulates Th17 lineage commitment via direct repression of the transcription factor IFN regulatory factor-4 (IRF4). An in vivo analysis of the pathogenicity of T-bet-deficient T cells demonstrated that mucosal Th17 responses were augmented in the absence of T-bet, and we have demonstrated that the roles of T-bet in enforcing Th1 responses and suppressing Th17 responses are separable. The interplay of the two key transcription factors T-bet and IRF4 during the determination of T cell fate choice significantly advances our understanding of the mechanisms underlying the development of pathogenic T cells.

The helminth product, ES-62, protects against airway inflammation by resetting the Th cell phenotype

We previously demonstrated inhibition of ovalbumin-induced allergic airway hyper-responsiveness in the mouse using ES-62, a phosphorylcholine-containing glycoprotein secreted by the filarial nematode, Acanthocheilonema viteae. This inhibition correlated with ES-62-induced mast cell desensitisation, although the degree to which this reflected direct targeting of mast cells remained unclear as suppression of the Th2 phenotype of the inflammatory response, as measured by eosinophilia and IL-4 levels in the lungs, was also observed. We now show that inhibition of the lung Th2 phenotype is reflected in ex vivo analyses of draining lymph node recall cultures and accompanied by a decrease in the serum levels of total and ovalbumin-specific IgE. Moreover, ES-62 also suppresses the lung infiltration by neutrophils that is associated with severe asthma and is generally refractory to conventional anti-inflammatory therapies, including steroids. Protection against Th2-associated airway inflammation does not reflect induction of regulatory T cell responses (there is no increased IL-10 or Foxp3 expression) but rather a switch in polarisation towards increased Tbet expression and IFNγ production. This ES-62-driven switch in the Th1/Th2 balance is accompanied by decreased IL-17 responses, a finding in line with reports that IFNγ and IL-17 are counter-regulatory. Consistent with ES-62 mediating its effects via IFNγ-mediated suppression of pathogenic Th2/Th17 responses, we found that neutralising anti-IFNγ antibodies blocked protection against airway inflammation in terms of pro-inflammatory cell infiltration, particularly by neutrophils, and lung pathology. Collectively, these studies indicate that ES-62, or more likely small molecule analogues, could have therapeutic potential in asthma, in particular for those subtypes of patients (e.g. smokers, steroid-resistant) who are refractory to current treatments.

An inhibitory role for Sema4A in antigen-specific allergic asthma

PURPOSE

The class IV semaphorin Sema4A is critical for efficient Th1 differentiation and Sema4a (-/-) mice exhibit impaired Th1 immune responses. However, the role of Sema4A in Th2 cell-mediated allergic diseases has not been fully studied. The aim of this study was to clarify the regulatory role possessed by Sema4A in mouse models of allergic diseases, particularly allergic asthma.

METHODS

Sema4a (-/-) mice on a BALB/c background were examined for the development of allergic diseases. To induce experimental asthma, mice were sensitized with ovalbumin (OVA) followed by intranasal challenges with OVA. After challenge, airway hyperreactivity (AHR) and airway inflammation were evaluated. The role of Sema4A in asthma was examined using Sema4a (-/-) mice and Sema4A-Fc fusion proteins. The direct effects of Sema4A-Fc on antigen-specific effector CD4(+) T cells were also examined.

RESULTS

A fraction of Sema4a (-/-) BALB/c mice spontaneously developed skin lesions that resembled atopic dermatitis (AD) in humans. Furthermore, AHR, airway inflammation, and Th2-type immune responses were enhanced in Sema4a (-/-) mice compared to wild type (WT) mice when immunized and challenged with OVA. In vivo systemic administration of Sema4A-Fc during the challenge period ameliorated AHR and lung inflammation and reduced the production of Th2-type cytokines in WT mice. The inhibitory effects of Sema4A on airway inflammation were also observed in mice deficient in Tim-2, a Sema4A receptor. Finally, we showed that Sema4A-Fc directly inhibited IL-4-producing OVA-specific CD4(+) T cells.

CONCLUSION

These results demonstrate that Sema4A plays an inhibitory role in Th2-type allergic diseases, such as allergic asthma.

A distinct regulatory role of Th17 cytokines IL-17A and IL-17F in chemokine secretion from lung microvascular endothelial cells

Th17 cytokines IL-17A and IL-17F play a critical role in the activation and recruitment of neutrophils at airway inflammation mainly through the induction of CXC chemokines in the lungs. Vascular endothelial cells belong to the category of major CXC chemokine-producing cells. However, until now, the precise role of Th17 cytokines in CXC chemokine secretion in lung microvascular endothelial cells (LMVECs) has not been fully elucidated. In this study, we examined the biological effects of Th17 cytokines IL-17A and IL-17F on CXCL1, CXCL5, and CXCL8 release in LMVECs. Both IL-17 receptor A (IL-17RA) and IL-17RC are expressed on the surface of LMVECs. In contrast to IL-17F, IL-17A significantly upregulated CXCL1 mRNA expression and protein release, whereas both IL-17A and IL-17F did not have the ability to induce CXCL5 and CXCL8 secretion in LMVECs. IL-17A and IL-17F displayed positive regulatory effects on IL-1β-induced CXCL1, CXCL5, and CXCL8 secretion. On the other hand, IL-17A enhanced the upregulating effect of TNF-α on CXCL1, CXCL5, and CXCL8 release, whereas IL-17F had a negative regulatory effect on TNF-α-mediated secretion. Th2 cytokines IL-4 and IL-13 showed an inhibitory effect on IL-1β plus IL-17A-induced CXCL1, CXCL5, and CXCL8 secretion, but displayed a positive regulatory effect on TNF-α plus IL-17A-induced secretion. These results provide evidence that Th17 cytokines IL-17A and IL-17F have a distinct regulatory role in CXCL1, CXCL5, and CXCL8 expression in LMVECs stimulated either with IL-1β or with TNF-α. Our findings also suggest that CXC chemokine secretion in LMVECs may be complicatedly regulated by Th17 cytokines, Th2 cytokines, and macrophage-associated cytokines in pathological conditions such as bronchial asthma.

Poly(I:C) promotes the production of IL-17A by murine CD1d-driven invariant NKT cells in airway inflammation

BACKGROUND

IL-17A is associated with different asthma phenotypes as virus-associated or steroid-resistant asthma. Invariant natural killer T (iNKT) cells play an important role in the pathogenesis of asthma. The aim of the study was to evaluate the activity of polyinosinic-polycytidylic acid [poly(I:C)] on IL-17A production by CD1d-activated iNKT cells.

METHODS

We analysed the in vitro effect of poly(I:C) on the release of IL-17A by spleen and lung CD1d-activated iNKT cells with α-galactosylceramide (α-GalCer). Its activity was also investigated in an α-GalCer-induced murine models, including lung inflammation. The inhibition of IL-17A by Toll-like receptor (TLR) 7 agonists in the same in vitro and in vivo models has been analysed.

RESULTS

Poly(I:C) upregulated the in vitro IL-17A production by CD1d-activated NK1.1- CD4- iNKT subset, without modifying type 1 and type 2 cytokines. The two stimuli selectively upregulated IL-17A serum levels in vivo. Their intratracheal administration resulted in increased airway hyper-reactivity (AHR), neutrophilia in bronchoalveolar lavage and airway inflammation, which were inhibited by anti-IL-17A antibody. Poly(I:C) effects were attributable to IL1β and IL-23 release from dendritic cells, as showed by inhibition with neutralizing antibodies. TLR7 agonists inhibited the IL-17A production by poly(I:C) plus α-GalCer in the same models. Such effect was associated with the increased production by DC of IL-17A-inhibiting cytokines and the dampening of IL-1β and IL-23.

CONCLUSIONS

Synthetic dsRNA selectively expand a CD1d-driven IL-17A-producing iNKT cell subset, thus explaining the worsening of airway inflammation by some viral infections. TLR3- and TLR7-triggering viral sequences can exert variable and opposite effects on adaptive immune response.

Epicutaneous exposure to staphylococcal superantigen enterotoxin B enhances allergic lung inflammation via an IL-17A dependent mechanism

Atopic dermatitis (AD) is the initial step of the atopic march: the progression from AD to allergic rhinitis and asthma. There is a close association between skin barrier abnormalities and the development of AD and the atopic march. One of cardinal features of AD is that the lesional skin of the majority of AD patients is chronically colonized with Staphylococcus aureus with half isolates producing superantigen enterotoxin B (SEB). Although diverse roles of SEB in the pathogenesis and severity of AD have been recognized, whether SEB contributes to the dermal inflammation that drives lung inflammation and airway hyperresponsiveness (AHR) has not been examined. Here we show a novel role of S. aureus superantigen SEB in augmenting allergen ovalbumin (Ova) induced atopic march through an IL-17A dependent mechanism. When mice epicutaneously (EC) sensitized with allergen Ova, addition of topical SEB led to not only augmented systemic Th2 responses but also a markedly exaggerated systemic Th17/IL-17 immune environment. The ability of SEB in enhancing Th17/IL-17 was mediated through stimulating lymphocytes in spleen and draining lymph nodes to promote IL-6 production. Epicutaneous sensitization of mice with a combination of Ova and SEB significantly enhanced Ova-induced AHR and granulocytic lung inflammation than Ova allergen alone. When IL-17A was deleted genetically, the effects of SEB on augmenting lung inflammation and AHR were markedly diminished. These findings suggest that chronic heavy colonization of enterotoxin producing S. aureus in the skin of patients with atopic dermatitis may have an important role in the development of atopic march via an IL-17A dependent mechanism.

Complement C3a-induced IL-17 plays a critical role in an IgE-mediated late-phase asthmatic response and airway hyperresponsiveness via neutrophilic inflammation in mice

Allergen-specific IgE plays an essential role in the pathogenesis of allergic asthma. Although there has been increasing evidence suggesting the involvement of IL-17 in the disease, the relationship between IL-17 and IgE-mediated asthmatic responses has not yet been defined. In this study, we attempted to elucidate the contribution of IL-17 to an IgE-mediated late-phase asthmatic response and airway hyperresponsiveness (AHR). BALB/c mice passively sensitized with an OVA-specific IgE mAb were challenged with OVA intratracheally four times. The fourth challenge caused a late-phase increase in airway resistance associated with elevated levels of IL-17(+)CD4(+) cells in the lungs. Multiple treatments with a C3a receptor antagonist or anti-C3a mAb during the challenges inhibited the increase in IL-17(+)CD4(+) cells. Meanwhile, a single treatment with the antagonist or the mAb at the fourth challenge suppressed the late-phase increase in airway resistance, AHR, and infiltration by neutrophils in bronchoalveolar lavage fluid. Because IL-17 production in the lungs was significantly repressed by both treatments, the effect of an anti-IL-17 mAb was examined. The late-phase increase in airway resistance, AHR, and infiltration by neutrophils in bronchoalveolar lavage fluid was inhibited. Furthermore, an anti-Gr-1 mAb had a similar effect. Collectively, we found that IgE mediated the increase of IL-17(+)CD4(+) cells in the lungs caused by repeated Ag challenges via C3a. The mechanisms leading to the IgE-mediated late-phase asthmatic response and AHR are closely associated with neutrophilic inflammation through the production of IL-17 induced by C3a.

Increased immunosuppressive function of CD4(+)CD25(+)Foxp3(+)GITR+ T regulatory cells from NFATc2((-/-)) mice controls allergen-induced experimental asthma

The expansion of effector T cells is tightly controlled by transcription factors like nuclear factor of activated T cells (NFAT) family members that mediate early intracellular responses to T cell receptor-mediated signals. In this study we show that, after allergen challenge, NFATc2((-/-)) mice had augmented number of functionally intact CD4(+)CD25(++)GITR(++) T regulatory (T regs) cells in the lung. Anti-GITR antibody treatment inhibited T regulatory cell function and enhanced the number of activated lung CD4(+) T cells associated with increased IL-2 and pSTAT-5 in the airways of NFATc2((-/-)) mice in experimental allergic asthma. This agonistic treatment led to increased inflammation in the lung of NFATc2((-/-)) treated mice. These data indicate that NFATc2((-/-)) mice have increased number of CD4(+)CD25(+)Foxp3(+) T regulatory cells with induced immunosuppressive function that control allergen-induced experimental asthma.

IL-33 induces Th17-mediated airway inflammation via mast cells in ovalbumin-challenged mice

Allergic asthma is characterized by infiltration of eosinophils, elevated Th2 cytokine levels, airway hyperresponsiveness, and IgE. In addition to eosinophils, mast cells, and basophils, a variety of cytokines are also involved in the development of allergic asthma. The pivotal role of eosinophils in the progression of the disease has been a subject of controversy. To determine the role of eosinophils in the progression of airway inflammation, we sensitized and challenged BALB/c wild-type (WT) mice and eosinophil-deficient ΔdblGATA mice with ovalbumin (OVA) and analyzed different aspects of inflammation. We observed increased eosinophil levels and a Th2-dominant response in OVA-challenged WT mice. In contrast, eosinophil-deficient ΔdblGATA mice displayed an increased proportion of mast cells and a Th17-biased response following OVA inhalation. Notably, the levels of IL-33, an important cytokine responsible for Th2 immune deviation, were not different between WT and eosinophil-deficient mice. We also demonstrated that mast cells induced Th17-differentiation via IL-33/ST2 stimulation in vitro. These results indicate that eosinophils are not essential for the development of allergic asthma and that mast cells can skew the immune reaction predominantly toward Th17 responses via IL-33 stimulation.

Expressions of IL-17, IL-21 and IL-23 in the Serum of Allergic Rhinitis Patients

The present study aimed to investigate the expressions of interleukin-17 (IL-17), IL-21 and IL-23 in the serum of allergic rhinitis (AR) patients and to explore their relationship with special IgE (sFgE) in the serum. AR patients (n=24) and healthy subjects (n=12) were recruited and serum samples were collected. The serum level of IgE specific for inhalant allergens was determined using the automatic quantitative immunofluorescence analysis system, and the contents of IL-17, IL-21 and IL-23 in the serum were detected using ELISA. The level of serum IgE in the healthy individuals was categorized as grade 0 and that in the AR patients as grade 2-6. The mean contents of IL-17, IL-21 and IL-23 were 164.71 ±39.37 pg/mL, 199±97.86 pg/mL and 78.94±26.33 pg/mL, respectively, in the AR patients, and 67.75±18.24 pg/mL, 7.58±5.49 pg/mL and 13.58± 3.93 pg/mL, respectively, in the healthy subjects. Statistical analysis showed the serum levels of IL-17 and IL-23 in the AR patients were markedly higher than those in the healthy subjects, however, no significant difference was noted in the content of IL-21. Furthermore, the IL-17 level was positively related to the levels of IL-23 and IgE and the IL-23 level was positively related to the IgE level among AR patients, but no relations were observed between the IL-21 level and levels of IL-17, IL-23 and IgE. Our study indicates IL-17 and IL-23 may play an important role in the pathogenesis of AR and maybe IL-21 is not involved in the occurrence of AR.

Interleukin-17 Accelerates Allograft Rejection by Suppressing Regulatory T Cell Expansion

Background—

Interleukin-17 (IL-17), which is predominantly produced by T helper 17 cells distinct from T helper 1 or T helper 2 cells, participates in the pathogenesis of infectious, autoimmune, and allergic disorders. However, the precise role in allograft rejection remains uncertain. In the present study, we investigated the role of IL-17 in acute allograft rejection using IL-17-deficient mice.

Methods and Results—

Donor hearts from FVB mice were heterotopically transplanted into either C57BL/6J-IL-17-deficient (IL-17 − / − ) or -wild-type mice. Allograft survival was significantly prolonged in IL-17 − / − recipient mice due to reduced local inflammation accompanied by decreased inflammatory cell recruitment and cytokine/chemokine expression. IL-17 − / − recipient mice exhibited decreased IL-6 production and reciprocally enhanced regulatory T cell expansion, suggesting a contribution of regulatory T cells to prolonged allograft survival. Indeed, allografts transplanted into anti-CD25 mAb-treated IL-17 − / − recipient mice (regulatory T cell-depleted) developed acute rejection similar to wild-type recipient mice. Surprisingly, we found that gamma delta T cells rather than CD4 + and CD8 + T cells were key IL-17 producers in the allografts. In support, equivalent allograft rejection was observed in Rag-2 −/− recipient mice engrafted with either wild-type or IL-17 − / − CD4 + and CD8 + T cells. Finally, hearts transplanted into gamma delta T cell-deficient mice resulted in decreased allograft rejection compared with wild-type controls.

Conclusions—

During heart transplantation, (1) IL-17 is crucial for acceleration of acute rejection; (2) IL-17-deficiency enhances regulatory T cell expansion; and (3) gamma delta T cells rather than CD4 + and CD8 + T cells are a potential source of IL-17. IL-17 neutralization may provide a potential target for novel therapeutic treatment for cardiac allograft rejection.

T-cell subset regulation in atopy

Presentation of processed allergen by antigen-presenting cells to T-helper (Th) lymphocytes, which is influenced costimulatory signals, cytokines, chemokines, and regulatory T cells (Tregs), determines the development of different types of T-cell immunity. The discovery of Tregs revolutionized the primary concepts of immune regulation interpreted within the framework of a binary Th1/Th2 paradigm. Tregs play a central role in the maintenance of peripheral homeostasis, the establishment of controlled immune responses, and the inhibition of allergen-specific effector cells. Recently, some other T-cell subsets appeared, including Th17 and Th9 cells, which control local tissue inflammation through upregulation of proinflammatory cytokines and chemokines. This review aims to discuss our understanding of the T-cell subset reciprocal interaction in atopy.

The cellular orchestra in skin allergy; are differences to lung and nose relevant?

PURPOSE OF REVIEW

It has been a long lasting question that although a similar peripheral allergen-specific immune response has been observed, why some patients show only atopic dermatitis, rhinitis and asthma alone or their combinations. The answer resides in the propensity of resident tissue cells and local antigen-presenting cells and T cells for developing an allergic inflammatory immune response. Antigen-presenting cells introduce processed allergens to T helper lymphocytes, where a decision of developing different types of T cell immunity is given under the influence of several cytokines, chemokines, costimulatory signals and regulatory T cells.

RECENT FINDINGS

We focused in this review article on effector T cell subsets, which have been recently described such as Th9, Th17 cells and Th22 cells, which are characterized by their IL-9 and IL-10, IL-17 (or IL-17A) and IL-22 expression, respectively together with other proinflammatory cytokines, which coordinate local tissue inflammation. Both naturally occurring CD4+CD25+ regulatory T (Treg) cells and inducible populations of allergen-specific, IL-10-secreting Treg type 1 cells inhibit allergen-specific effector cells and have been shown to play a central role in the maintenance of peripheral homeostasis and the establishment of controlled immune responses in allergic inflammatory tissues.

SUMMARY

Better understanding and characterization of newly described effector cell subsets and their interaction between antigen presenting cells and resident tissue cells will enlighten our knowledge on the mechanisms of allergic diseases.

The TLR7 ligand 9-benzyl-2-butoxy-8-hydroxy adenine inhibits IL-17 response by eliciting IL-10 and IL-10-inducing cytokines

This study evaluates the ability of a novel TLR7 ligand (9-benzyl-2-butoxy-8-hydroxy adenine, called SA-2) to affect IL-17 response. The SA-2 activity on the expression of IL-17A and IL-17-related molecules was evaluated in acute and chronic models of asthma as well as in in vivo and in vitro α-galactosyl ceramide (α-GalCer)-driven systems. SA-2 prepriming reduced neutrophils in bronchoalveolar lavage fluid and decreased methacoline-induced airway hyperresponsiveness in murine asthma models. These results were associated with the reduction of IL-17A (and type 2 cytokines) as well as of molecules favoring Th17 (and Th2) development in lung tissue. The IL-17A production in response to α-GalCer by spleen mononuclear cells was inhibited in vitro by the presence of SA-2. Reduced IL-17A (as well as IFN-γ and IL-13) serum levels in mice treated with α-GalCer plus SA-2 were also observed. The in vitro results indicated that IL-10 produced by B cells and IL-10-promoting molecules such as IFN-α and IL-27 by dendritic cells are the major player for SA-2-driven IL-17A (and also IFN-γ and IL-13) inhibition. The in vivo experiments with anti-cytokine receptor Abs provided evidence of an early IL-17A inhibition essentially due to IL-10 produced by resident peritoneal cells and of a delayed IL-17A inhibition sustained by IFN-α and IL-27, which in turn drive effector T cells to IL-10 production. These findings suggest that such TLR7 agonist downregulating Th17 (as well as Th2) response has to be considered a valid candidate for novel vaccine formulations in allergy.

What's new in asthma pathophysiology and immunopathology?

Research on asthma pathophysiology over the past decade has expanded the complex repertoire involved in the pathophysiology of asthma to include inflammatory, immune and structural cells, as well as a wide range of mediators. Studies have identified a role for connective and other mesenchymal tissues involved in airway remodeling. Recent findings have implicated the innate immune response in asthma and have revealed interesting patterns of interaction between the innate and adaptive immune response and the associated complex chronic inflammatory reaction. New immune cell populations have also been added to this repertoire, including Tregs, natural killer T cells and Th17 cells. The role of the eosinophil, a prominent pathological feature in most asthma phenotypes, has also been expanding to include roles such as tissue modifiers and immune regulators via a number of fascinating and hitherto unexplored mechanistic pathways. In addition, new and significant roles have been proposed for airway smooth muscle cells, fibroblasts, epithelial and endothelial cells. Tissue remodeling is now considered an integral element of asthma pathophysiology. Finally, an intricate network of mediators, released from both immune and inflammatory cells, including thymus stromal lymphopoietin and matrix metalloproteinases, have added to the complex milieu of asthma immunity and inflammation. These findings have implications for therapy and the search for novel strategies towards better disease management. Sadly, and perhaps due to the complex nature of asthma, advances in therapeutic discoveries and developments have been limited. Thus, understanding the precise roles played by the numerous dramatis personae in this odyssey, both individually and collectively within the context of asthma pathophysiology, continues to pose new challenges. It is clear that the next stage in this saga is to embark on studies that transcend reductionist approaches to involve system analysis of the complex and multiple variables involved in asthma, including the need to narrow down the phenotypes of this condition based on careful analysis of the organs (lung and airways), cells, mediators and other factors involved in bronchial asthma.

STAT6 expression in multiple cell types mediates the cooperative development of allergic airway disease

Th2 cells induce asthma through the secretion of cytokines. Two such cytokines, IL-4 and IL-13, are critical mediators of many features of this disease. They both share a common receptor subunit, IL-4Rα, and signal through the STAT6 pathway. STAT6(-/-) mice have impaired Th2 differentiation and reduced airway response to allergen. Transferred Th2 cells were not able to elicit eosinophilia in response to OVA in STAT6(-/-) mice. To clarify the role of STAT6 in allergic airway inflammation, we generated mouse bone marrow (BM) chimeras. We observed little to no eosinophilia in OVA-treated STAT6(-/-) mice even when STAT6(+/+) BM or Th2 cells were provided. However, when Th2 cells were transferred to STAT6×Rag2(-/-) mice, we observed an eosinophilic response to OVA. Nevertheless, the expression of STAT6 on either BM-derived cells or lung resident cells enhanced the severity of OVA-induced eosinophilia. Moreover, when both the BM donor and recipient lacked lymphocytes, transferred Th2 cells were sufficient to induce the level of eosinophilia comparable with that of wild-type (WT) mice. The expression of STAT6 in BM-derived cells was more critical for the enhanced eosinophilic response. Furthermore, we found a significantly higher number of CD4(+)CD25(+)Foxp3(+) T cells (regulatory T cells [Tregs]) in PBS- and OVA-treated STAT6(-/-) mouse lungs compared with that in WT animals suggesting that STAT6 limits both naturally occurring and Ag-induced Tregs. Tregs obtained from either WT or STAT6(-/-) mice were equally efficient in suppressing CD4(+) T cell proliferation in vitro. Taken together, our studies demonstrate multiple STAT6-dependent and -independent features of allergic inflammation, which may impact treatments targeting STAT6.

Transcriptional regulation of the mucosal immune system mediated by T-bet

The immune system faces the arduous task of defending the mucosal surfaces from invading pathogens, but must simultaneously repress responses against commensal organisms and other inert antigens that are abundant in the external environment, as inappropriate immune activation might expose the host to increased risk of autoimmunity. The behavior of individual immune cells is governed by the expression of transcription factors that are responsible for switching immune response genes on and off. T-bet (T-box expressed in T cells) has emerged as one of the key transcription factors responsible for controlling the fate of both innate and adaptive immune cells, and its expression in different immune cells found at mucosal surfaces is capable of dictating the critical balance between permitting robust host immunity and limiting susceptibility to autoimmunity and allergy.

Epinephrine-primed murine bone marrow-derived dendritic cells facilitate production of IL-17A and IL-4 but not IFN-γ by CD4+ T cells

Sympathetic activation leading to the release of epinephrine and norepinephrine, is known as an important regulatory circuit related to immune-mediated diseases. However, questions still remain on the behavior of antigen presenting cells (APC) dictated by stress-induced sympathetic neurotransmitters. The purpose of this study was to examine the fate of bone marrow-derived dendritic cell (BMDC)-associated influences on resting CD4(+) T cell activation. We hypothesize that pre-exposure of dendritic cells (DCs) can modify the intensity of cytokine production, leading to preference in resting CD4(+) T cell activation. BMDCs were pre-treated with epinephrine for 2h followed by subsequent treatment of lipopolysaccharide (LPS). Subsequently, BMDCs were cocultured with purified CD4(+) T cells from mouse spleen in the absence or presence of anti-CD3 stimulation in epinephrine-free media. Epinephrine pre-treatment enhanced surface expression of MHCII, CD80 and CD86. Quantitative RT-PCR showed that epinephrine pre-treatment induced a significant transcriptional decrease of IL-12p40 and a significant increase of IL-12p35 and IL-23p19. In addition, β2-adrenergic-blockade was shown to reverse these effects. Epinephrine pre-treatment also induced a significant decrease of IL-12p70 and a significant increase of IL-23 and IL-10 cytokine production. Importantly, these changes corresponded with increased IL-4 and IL-17A, but not IFN-g cytokine production by CD4(+) T cells in a b2-adrenergic receptor-dependent manner. These results suggest that exposure to stress-derived epinephrine dictates dendritic cells to generate a dominant Th2/Th17 phenotype in the context of subsequent exposure to a pathogenic stimulus.

In vivo tumor suppression activity by T cell-specific T-bet restoration

T-box-containing protein expressed in T cells (T-bet) is a master transcription factor for the development of interferon (IFN) gamma-producing T helper 1 (Th1) cells and also functions in other immune cells including natural killer (NK), cytotoxic T lymphocytes and dendritic cells. T-bet-deficient mice increased susceptibility to viral infection and tumor development due to the defective functions of immune cells. T-bet is known to play a key role in NK-mediated antimetastatic response; however, it remains to be characterized whether T-bet is essential for in vivo tumor suppression mediated by T cells. Here, we have investigated in vivo tumor suppression effect of T-bet-restored T cells using T cell-specific and inducible T-bet transgenic mice generated in a T-bet-deficient background. T-bet-null mice increased susceptibility to tumor development, whereas induction of T cell-specific T-bet expression upon melanoma cell injection substantially suppressed tumor development by inducing IFNgamma production in T cells and tumor cell apoptosis. Late induction of T-bet expression in tumor-bearing mice produced comparable amounts of IFNgamma with control and significantly decreased tumor volume. In addition, increased melanoma lung metastasis in T-bet-deficient mice was strikingly inhibited by T-bet restoration in T cells. Intravenous injection of activated Th1 cells, not T-bet-null Th1 cells, attenuated metastatic melanoma progression, in addition, restoration of T-bet in T-bet-null Th1 cells certainly retrieved antimetastatic activity. These results suggest that T-bet expression in T cells is crucial for the control of tumor development and antimetastatic activity.

Emerging roles of T helper subsets in the pathogenesis of asthma

The cardinal features of asthma include pulmonary inflammation and airway hyperresponsiveness (AHR). Classically, asthma, specifically allergic asthma, has been attributed to a hyperactive Th2 cell immune response. However, the Th2 cell-mediated inflammation model has failed to adequately explain many of the clinical and molecular aspects of asthma. In addition, the outcomes of Th2-targeted therapeutic trials have been disappointing. Thus, asthma is now believed to be a complex and heterogeneous disorder, with several molecular mechanisms underlying the airway inflammation and AHR that is associated with asthma. The original classification of Th1 and Th2 pathways has recently been expanded to include additional effector Th cell subsets. These include Th17, Th9 and Treg cells. Emerging data highlight the involvement of these new Th cell subsets in the initiation and augmentation of airway inflammation and asthmatic responses. We now review the roles of these recently classified effector Th cell subsets in asthmatic inflammation and the insights they may provide in addition to the traditional Th2 paradigm. The hope is that a clearer understanding of the inflammatory pathways involved and the mediators of inflammation will yield better targeted therapeutics.

Th-17 cells in the lungs?

Naive CD4 cells are capable of integrating signals from antigen-activated cells of the innate immune system and differentiating into effector CD4 cells, also termed T helper (Th) cells. According to the traditional paradigm explaining adaptive CD4 cell responses, there are two subsets of Th cells: the Th-1 and Th-2 subset. Each of these subsets undergoes a distinct differentiation pathway (a pathway that is characterized by a unique profile of cytokine production and has specific immunoregulatory functions). However, recent studies in mouse models have forwarded evidence of a third subset of Th cells: the Th-17 subset. As indicated predominantly in studies on mice, the Th-17 subset is characterized by an ability to produce the neutrophil-mobilizing cytokine IL-17 in response to stimulation with the cytokine IL-23, an IL-12-related cytokine released from antigen-presenting cells. There is now a growing body of evidence from animal models that the Th-17 subset plays an important role in host defence in the lungs and other organs. Altered IL-17 levels have also been demonstrated in human patients with asthma, exacerbations of cystic fibrosis or following lung transplantation. There is now also evidence that the Th-17 subset is functionally distinct from the Th-2 subset but little is known of the functional inter-relationship between the Th-1 and Th-17 cell subsets; this is particularly true in human lungs. It has been proposed that the Th-17 subset plays a unique role by linking the arms of innate and adaptive immunity. Thus, an improved understanding of the human correlate to the Th-17 subset may reveal new targets for pharmacotherapy against lung disorders that are characterized by aberrant innate responses in host defense.