T follicular helper and TH2 cells in allergic responses

T-cell immune profile in blood of systemic mastocytosis: Association with disease features

BACKGROUND

Systemic mastocytosis (SM) is a heterogeneous disease characterized by an expansion of KIT-mutated mast cells (MC). KIT-mutated MC display activated features and release MC mediators that might act on the tumour microenvironment and other immune cells. Here, we investigated the distribution of lymphocyte subsets in blood of patients with distinct subtypes of SM and determined its association with other disease features.

METHODS

We studied the distribution of TCD4+ and TCD4- cytotoxic cells and their subsets, as well as total NK- and B cells, in blood of 115 SM patients-38 bone marrow mastocytosis (BMM), 67 indolent SM (ISM), 10 aggressive SM (ASM)- and 83 age-matched healthy donors (HD), using spectral flow cytometry and the EuroFlow Immunomonitoring panel, and correlated it with multilineage KITD816V, the alpha-tryptasemia genotype (HαT) and the clinical manifestations of the disease.

RESULTS

SM patients showed decreased counts (vs. HD) of TCD4- cytotoxic cells, NK cells and several functional subsets of TCD4+ cells (total Th1, Th2-effector memory, Th22-terminal effector and Th1-like Tregs), together with increased T-follicular-helper and Th1/Th17-like Treg counts, associated with different immune profiles per diagnostic subtype of SM, in multilineal versus MC-restricted KITD816V and in cases with a HαT+ versus HαT- genotype. Unique immune profiles were found among BMM and ISM patients with MC-restricted KITD816V who displayed HαT, anaphylaxis, hymenoptera venom allergy, bone disease, pruritus, flushing and GI symptoms.

CONCLUSION

Our results reveal altered T- and NK-cell immune profiles in blood of SM, which vary per disease subtype, the pattern of involvement of haematopoiesis by KITD816V, the HαT genotype and specific clinical manifestations of the disease.

The role of Interleukin-21 (IL-21) in allergic disorders: Biological insights and regulatory mechanisms

In recent decades, allergic diseases subsequent from an IgE-mediated response to specific allergens have become a progressively public chronic disease worldwide. They have shaped an important medical and socio-economic burden. A significant proportion of allergic disorders are branded via a form 2 immune response relating Th2 cells, type 2 natural lymphoid cells, mast cells and eosinophils. Interleukin-21 (IL-21) is a participant of the type-I cytokine family manufactured through numerous subsets of stimulated CD4+ T cells and uses controlling properties on a diversity of immune cells. Increasingly, experimental sign suggests a character for IL-21 in the pathogenesis of numerous allergic disorders. The purpose of this review is to discuss the biological properties of IL-21 and to summaries current developments in its role in the regulation of allergic disorders.

Aiming to IgE: Drug development in allergic diseases

The incidence of allergic disease significantly increases in recent decades, causing it become a major public health problem all over the world. The common allergic diseases such as allergic dermatitis, allergy rhinitis, allergic asthma and food allergy are mediated, at least in part, by immunoglobulin E (IgE), and so IgE acts as a central role in allergic diseases. IgE can interact with its high-affinity receptor (FcεRⅠ) which is primarily expressed on tissue-resident mast cells and circulating basophils, initiating intracellular signal transduction and then causing the activation and degranulation of mast cells and basophils. On the other hand, IgE interaction with its low-affinity receptor (CD23), can regulate various IgE-mediated immune responses including IgE-allergen complex presentation, IgE synthesis, the growth and differentiation of both B and T cells, and the secretion of pro-inflammatory mediators. With the deeper mechanism research for allergic diseases, new therapeutic strategies for interfering IgE are developed and receive a great attention. In this review, we summarize a current profile of therapeutic strategies for interfering IgE in allergic diseases. Besides, we suggest that targeting memory B cells (including long-lived plasma cells and (or) IgE⁺ memory B cells) may help to completely control allergic diseases, and highlight that the development of drugs synergistically aiming to multiple targets can be a better choice for improving treatment efficacy which results from allergic diseases as the systemic disorders caused by an impaired immune system.

T follicular helper phenotype mycosis fungoides associated with acanthosis nigricans

The association between acanthosis nigricans (AN) and mycosis fungoides (MF) has rarely been described, but it is known that MF may appear as AN-like vegetating and papillomatous plaques in skin folds, or may be associated with paraneoplastic AN. There have also been recent descriptions of a form of "intertriginous MF" that is characterized by skin fold involvement and the expression of T follicular helper (TFH) markers, and that often has an aggressive course. We describe the case of a 48-year-old man affected by MF associated with AN, whose lesions were characterized by a TFH immunophenotype and the expression of the GATA-3 nuclear master regulator that may be related to a TFH-2 subpopulation or possible disease progression.

Therapeutic Strategies of Biologics in Chronic Rhinosinusitis: Current Options and Future Targets

Chronic rhinosinusitis is a chronic inflammatory disease of the upper airways, for which treatment options include medical or surgical therapy. However, there are limitations to conservative treatment strategies, such as the relapse of nasal polyps. In this review, we discuss the rising role of biomolecular mechanisms associated with various biologics that have been approved or are undergoing clinical trials to treat chronic rhinosinusitis. We also highlight the potential molecular therapeutic targets for managing and treating chronic rhinosinusitis.

Allergic Rhinitis: A Clinical and Pathophysiological Overview

Allergic rhinitis (AR) represents a global health concern where it affects approximately 400 million people worldwide. The prevalence of AR has increased over the years along with increased urbanization and environmental pollutants thought to be some of the leading causes of the disease. Understanding the pathophysiology of AR is crucial in the development of novel therapies to treat this incurable disease that often comorbids with other airway diseases. Hence in this mini review, we summarize the well-established yet vital aspects of AR. These include the epidemiology, clinical and laboratory diagnostic criteria, AR in pediatrics, pathophysiology of AR, Th2 responses in the disease, as well as pharmacological and immunomodulating therapies for AR patients.

Atopy manifestations in pediatric patients with acute lymphoblastic leukemia: correlation assessment with interleukin-4 (IL-4) and IgE level

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most common type of cancer in the age range of under 15 years old and accounts for 25-30% of all childhood cancers. Although conventional chemotherapy regimens are used to improve the overall survival rate, it has been associated with some complications, amongst which allergic manifestations with unknown mechanisms are more common.

METHODS

Our study compared serum IgE and IL-4 concentration, as a hallmark of allergic responses in pediatric ALL patients before and after 6 months of intensive (high-dose) chemotherapy, to show whether changes in the level of these markers may be associated with atopy. Serum level of IL-4 and IgE was measured using enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

The results showed that the level of IgE and IL-4 increased following chemotherapy in both ALL patients with and without atopy. In addition, post-chemotherapy treatment IgE and IL-4 levels were significantly elevated in patients with atopy compared to those without it. The difference between baseline and post-chemotherapy level of IgE and IL-4 was significantly higher in patients with atopy compared to those without it.

CONCLUSIONS

To the best of our knowledge, this is the first study that showed a connection between post-chemotherapy allergic manifestations in pediatric ALL patients and IL-4 and IgE level. Flow cytometry analysis of the T-helper 2 (Th2) lymphocytes and other allergy-related T cell subsets like Tc2 and Th9 as well as the study of the genetic variations in atopy-related genes like IL-4/IL-4R, IL-5, IL-9, IL-13, and high affinity FcεRI IgE receptor and also HLA genes is necessary to clearly define the underlying mechanism responsible for post-chemotherapy hypersensitivity reaction in pediatric ALL patients.

Bach2: A Key Regulator in Th2-Related Immune Cells and Th2 Immune Response

Th2 immune response is essential for providing protection against pathogens and orchestrating humoral immunity. However, excessive Th2 immune response leads to the pathogenesis of Th2 inflammation diseases, including asthma, allergic rhinitis, and atopic dermatitis. Emerging evidence suggest a critical role of the transcription factor Bach2 in regulating Th2 immune responses. Bach2 serves as a super enhancer and transcriptional repressor to control the differentiation and maturation of Th2-related immune cells such as B cell lineages and T cell lineages. In B cells, Bach2 is required for every stage of B cell development and can delay the class switch recombination and antibody-producing plasma cell differentiation. In T cell lineages, Bach2 suppresses the CD4⁺ T cell differentiation into Th2 cells, restrains Th2 cytokine production, and promotes the generation and function of regulatory T (Treg) cells to balance the immune activity. Furthermore, studies in various animal models show that Bach2 knockout animals spontaneously develop Th2 inflammation in the airway and gastrointestinal tract. Genome-wide association studies have identified various susceptibility loci of Bach2 which are linked with Th2 inflammatory diseases such as asthma and inflammatory bowel disease. Here, we discuss the critical role of Bach2 involved in the Th2 immune response and associated inflammatory diseases.

Periostin in Allergy and Inflammation

Matricellular proteins are involved in the crosstalk between cells and their environment and thus play an important role in allergic and inflammatory reactions. Periostin, a matricellular protein, has several documented and multi-faceted roles in health and disease. It is differentially expressed, usually upregulated, in allergic conditions, a variety of inflammatory diseases as well as in cancer and contributes to the development and progression of these diseases. Periostin has also been shown to influence tissue remodelling, fibrosis, regeneration and repair. In allergic reactions periostin is involved in type 2 immunity and can be induced by IL-4 and IL-13 in bronchial cells. A variety of different allergic diseases, among them bronchial asthma and atopic dermatitis (AD), have been shown to be connected to periostin expression. Periostin is commonly expressed in fibroblasts and acts on epithelial cells as well as fibroblasts involving integrin and NF-κB signalling. Also direct signalling between periostin and immune cells has been reported. The deposition of periostin in inflamed, often fibrotic, tissues is further fuelling the inflammatory process. There is increasing evidence that periostin is also expressed by epithelial cells in several of the above-mentioned conditions as well as in cancer. Augmented periostin expression has also been associated with chronic inflammation such as in inflammatory bowel disease (IBD). Periostin can be expressed in a variety of different isoforms, whose functions have not been elucidated yet. This review will discuss potential functions of periostin and its different isoforms in allergy and inflammation.

Cellular and molecular mechanisms of allergic asthma

Asthma is a chronic disease of the airways, which affects more than 350 million people worldwide. It is the most common chronic disease in children, affecting at least 30 million children and young adults in Europe. Asthma is a complex, partially heritable disease with a marked heterogeneity. Its development is influenced both by genetic and environmental factors. The most common, as well as the most well characterized subtype of asthma is allergic eosinophilic asthma, which is characterized by a type 2 airway inflammation. The prevalence of asthma has substantially increased in industrialized countries during the last 60 years. The mechanisms underpinning this phenomenon are incompletely understood, however increased exposure to various environmental pollutants probably plays a role. Disease inception is thought to be enabled by a disadvantageous shift in the balance between protective and harmful lifestyle and environmental factors, including exposure to protective commensal microbes versus infection with pathogens, collectively leading to airway epithelial cell damage and disrupted barrier integrity. Epithelial cell-derived cytokines are one of the main drivers of the type 2 immune response against innocuous allergens, ultimately leading to infiltration of lung tissue with type 2 T helper (T_H2) cells, type 2 innate lymphoid cells (ILC2s), M2 macrophages and eosinophils. This review outlines the mechanisms responsible for the orchestration of type 2 inflammation and summarizes the novel findings, including but not limited to dysregulated epithelial barrier integrity, alarmin release and innate lymphoid cell stimulation.

The Lanostane Triterpenoids in Poria cocos Play Beneficial Roles in Immunoregulatory Activity

Poria cocos (Schwein) F.A. Wolf (syn. Wolfiporia cocos) dried sclerotium, called fuling, is an edible, saprophytic fungus commonly used as a tonic and anti-aging traditional Chinese medicine. It is traditionally used in combination with other traditional Chinese medicines to enhance immunity. This study showed that P. cocos extract (Lipucan®) containing lanostane triterpenoids has no immunotoxicity and enhances non-specific (innate) immunity though activating natural killer cells and promotes interferon γ (IFN-γ) secretion by Type 1 T-helper (Th1) cells immune response. In addition, P. cocos extract significantly decreased interleukin (IL-4 and IL-5) secretion by Type 2 T-helper (Th2) cells immune response, which are related to the allergy response. The purified lanostane triterpenoids were first identified as active ingredients of P. cocos with enhanced non-specific immunity by promoting interferon γ (IFN-γ) secretion in a preliminary study. Our findings support that the P. cocos extract plays beneficial roles in immunoregulatory activity.

Mutual inhibition between Prkd2 and Bcl6 controls T follicular helper cell differentiation

T follicular helper cells (T_FH) participate in germinal center (GC) development and are necessary for B cell production of high-affinity, isotype-switched antibodies. In a forward genetic screen, we identified a missense mutation in Prkd2, encoding the serine/threonine kinase protein kinase D2, which caused elevated titers of immunoglobulin E (IgE) in the serum. Subsequent analysis of serum antibodies in mice with a targeted null mutation of Prkd2 demonstrated polyclonal hypergammaglobulinemia of IgE, IgG1, and IgA isotypes, which was exacerbated by the T cell-dependent humoral response to immunization. GC formation and GC B cells were increased in Prkd2^-/- spleens. These effects were the result of excessive cell-autonomous T_FH development caused by unrestricted Bcl6 nuclear translocation in Prkd2^-/- CD4⁺ T cells. Prkd2 directly binds to Bcl6, and Prkd2-dependent phosphorylation of Bcl6 is necessary to constrain Bcl6 to the cytoplasm, thereby limiting T_FH development. In response to immunization, Bcl6 repressed Prkd2 expression in CD4⁺ T cells, thereby committing them to T_FH development. Thus, Prkd2 and Bcl6 form a mutually inhibitory positive feedback loop that controls the stable transition from naïve CD4⁺ T cells to T_FH during the adaptive immune response.

Generation of a novel CD30+ B cell subset producing GM-CSF and its possible link to the pathogenesis of systemic sclerosis

Systemic sclerosis (SSc) is a T helper type 2 (Th2)-associated autoimmune disease characterized by vasculopathy and fibrosis. Efficacy of B cell depletion therapy underscores antibody-independent functions of B cells in SSc. A recent study showed that the Th2 cytokine interleukin (IL)-4 induces granulocyte-macrophage colony-stimulating factor (GM-CSF)-producing effector B cells (GM-Beffs ) in humans. In this study, we sought to elucidate the generation mechanism of GM-Beffs and also determine a role of this subset in SSc. Among Th-associated cytokines, IL-4 most significantly facilitated the generation of GM-Beffs within memory B cells in healthy controls (HCs). In addition, the profibrotic cytokine transforming growth factor (TGF)-β further potentiated IL-4- and IL-13-induced GM-Beffs . Of note, tofacitinib, a Janus kinase (JAK) inhibitor, inhibited the expression of GM-CSF mRNA and protein in memory B cells induced by IL-4, but not by TGF-β. GM-Beffs were enriched within CD20+ CD30+ CD38-/low cells, a distinct population from plasmablasts, suggesting that GM-Beffs exert antibody-independent functions. GM-Beffs were also enriched in a CD30+ fraction of freshly isolated B cells. GM-Beffs generated under Th2 conditions facilitated the differentiation from CD14+ monocytes to DC-SIGN+ CD1a+ CD14- CD86+ cells, which significantly promoted the proliferation of naive T cells. CD30+ GM-Beffs were more pronounced in patients with SSc than in HCs. A subpopulation of SSc patients with the diffuse type and concomitant interstitial lung disease exhibited high numbers of GM-Beffs . Together, these findings suggest that human GM-Beffs are enriched in a CD30+ B cell subset and play a role in the pathogenesis of SSc.

T follicular helper cells are elevated in a rat model of autoimmune myocarditis

Myocarditis is an inflammatory disease of the myocardium that is associated with immune dysfunction. Earlier studies have suggested that T helper 1/2 cell imbalance plays an important role in the development of myocarditis, but the role of T follicular helper (Tfh) cells in the development of autoimmune myocarditis has not previously been reported. Here, we investigated this involvement by using a rat model of experimental autoimmune myocarditis (EAM). Inflammatory cell infiltration, myocardial structure destruction and tissue necrosis were observed in EAM myocardial tissues, and the percentages of CD4⁺ CXCR5⁺ Tfh cells and CD19⁺ B cells were both significantly higher in spleen and myocardial tissues of the EAM model as compared with the control group. Furthermore, the expression levels of interleukin-21, CXCL13 and myosin antibody were significantly higher in the serum of rats with EAM compared with the control group on days 14 and 35 after immunization. Fourteen or 35 days after immunization, the expression levels of interleukin-21 and CXCL13 were both significantly higher in myocardial tissues of rats with EAM as compared with the control group. Our findings suggest that Tfh cell balance is disrupted during the pathological process of autoimmune myocarditis.

Dupilumab: Basic aspects and applications to allergic diseases

Interleukin (IL)-4 and IL-13, signature type 2 cytokines, exert their actions by binding to two types of receptors sharing the IL-4R α chain (IL-4Rα). Since IL-4 and IL-13 play important and redundant roles in the pathogenesis of allergic diseases, blocking both the IL-4 and IL-13 signals would be a powerful and effective strategy for treating allergic diseases. Dupilumab (Dupixent®) is a fully human monoclonal antibody recognizing IL-4Rα and blocking both the IL-4 and IL-13 signals. Dupilumab was first prescribed for atopic dermatitis (AD) patients and has been widely approved for adult patients with moderate to severe AD since 2018. Dupilumab has since been used for asthma, receiving approval for uncontrolled asthma in 2019. A phase 3 study using dupilumab for chronic rhinosinusitis with nasal polyps (CRSwNP) has been just completed, with positive results. Several clinical trials of dupilumab for other diseases in which type 2 inflammation is dominant are now underway. It is hoped that dupilumab will open the door to a new era for treating allergic patients with AD, asthma, and CRSwNP, and for more patients with type 2 inflammations.

Regulation of IgE by T follicular helper cells

Allergies to food and environmental antigens have steeply grown to epidemic proportions. IgE antibodies are key mediators of allergic disease, including life-threatening anaphylaxis. There is now compelling evidence that one of the hallmarks of anaphylaxis-inducing IgE molecules is their high affinity for allergen, and the cellular pathway to high-affinity IgE is typically through sequential switching of IgG B cells. Further, in contrast to the previously held paradigm that a subset of CD4⁺ T cells called Th2 cells promotes IgE responses, recent studies suggest that T follicular helper cells are crucial for inducing anaphylactic IgE. Here we discuss recent studies that have enabled us to understand the nature, induction, and regulation of this enigmatic antibody isotype in allergic sensitization.

T Follicular Helper Cell Subsets and the Associated Cytokine IL-21 in the Pathogenesis and Therapy of Asthma

For many decades, T helper 2 (T_H2) cells have been considered to predominantly regulate the pathogenic manifestations of allergic asthma, such as IgE-mediated sensitization, airway hyperresponsiveness, and eosinophil infiltration. However, recent discoveries have significantly shifted our understanding of asthma from a simple T_H2 cell-dependent disease to a heterogeneous disease regulated by multiple T cell subsets, including T follicular helper (T_FH) cells. T_FH cells, which are a specialized cell population that provides help to B cells, have attracted intensive attention in the past decade because of their crucial role in regulating antibody response in a broad range of diseases. In particular, T_FH cells are essential for IgE antibody class-switching. In this review, we summarize the recent progress regarding the role of T_FH cells and their signature cytokine interleukin (IL)-21 in asthma from mouse studies and clinical reports. We further discuss future therapeutic strategies to treat asthma by targeting T_FH cells and IL-21.

Obesity affects peripheral lymphoid organs immune response in murine asthma model

Asthma and obesity present rising incidence, and their concomitance is a reason for concern, as obese individuals are usually resistant to conventional asthma treatments and have more exacerbation episodes. Obesity affects several features in the lungs during asthma onset, shifting the T helper type 2 (Th2)/eosinophilic response towards a Th17/neutrophilic profile. Moreover, those individuals can present reduced atopy and delayed cytokine production. However, the impact of obesity on follicular helper T (Tfh) cells and B cells that could potentially result in antibody production disturbances are still unclear. Therefore, we aimed to assess the peripheral response to ovalbumin (OVA) in a concomitant model of obesity and asthma. Pulmonary allergy was induced, in both lean and obese female BALB/c mice, through OVA sensitizations and challenges. Mediastinal lymph nodes (MLNs) and spleen were processed for immunophenotyping. Lung was used for standard allergy analysis. Obese-allergic mice produced less anti-OVA IgE and more IgG2a than lean-allergic mice. Dendritic cells (CD11c⁺  MHCII^high ) expressed less CD86 and more PDL1 in obese-allergic mice compared with lean-allergic mice, in the MLNs. Meanwhile, B cells (CD19⁺  CD40⁺ ) were more frequent and the amount of PDL1/PD1⁺ cells was diminished by obesity, with the opposite effects in the spleen. Tfh cells (CD3⁺  CD4⁺  CXCR5⁺  PD1⁺ ) expressing FoxP3 were more frequent in obese mice, associated with the predominance of Th (CD3⁺  CD4⁺ ) cells expressing interleukin-4/GATA3 in the MLNs and interleukin-17A/RORγT in the spleen. Those modifications to the main components of the germinal centers could be resulting in the increased IgG2a production, which - associated with the Th17/neutrophilic profile - contributes to asthma worsening and represents an important target for future treatment strategies.

Tumefactive Inflammatory Diseases of the Pancreas

Advances in the past two decades have resulted in the recognition of several tumefactive pancreatic lesions that, on histologic evaluation, show a varying combination of inflammation and fibrosis. Autoimmune pancreatitis, the prototypic tumefactive pancreatic fibroinflammatory lesion, is composed of two distinct diseases, type 1 autoimmune pancreatitis and the less common type 2 autoimmune pancreatitis. Although designated as autoimmune pancreatitis, the two diseases show little morphologic or pathogenic overlap. In type 1 disease, subsets of T lymphocytes (type 2 helper T cells, regulatory T cells, and T follicular helper 2 cells) are hypothesized to drive the inflammatory reaction. The B-cell response is characterized by an oligoclonal expansion of plasmablasts, with dominant clones that vary among patients and distinct clones that emerge at the time of relapse. Although the precise role of IgG4 in this condition remains uncertain, recent studies suggest that other IgG subclasses (eg, IgG1) may mediate the immune reactions, whereas IgG4 represents a response to dampen excessive inflammation. A recent study of type 2 autoimmune pancreatitis highlights the role of CXCL8 (alias IL-8), with duct epithelium and infiltrating T lymphocytes expressing this chemokine; the latter may contribute to the distinct form of neutrophilic inflammation in this disease. The review also highlights other forms of mass-forming chronic pancreatitis: follicular pancreatitis, groove pancreatitis, and those associated with rheumatologic diseases.

Microneedles coated with peanut allergen enable desensitization of peanut sensitized mice

The prevalence of peanut allergies has escalated over the last 20 years, yet there are no FDA approved treatments for peanut allergies. In this study we evaluated the potential of microneedles to deliver peanut protein extract (PE) into skin and assessed if the ensuing immune responses could desensitize mice that were sensitized to peanuts. Peanut sensitized mice were either treated through cutaneous immunotherapy using PE-coated microneedles or not treated, and then orally challenged with PE. After oral challenge, the clinical symptoms of peanut-induced anaphylaxis were significantly lower in the microneedle treated mice as compared to untreated mice, and this was accompanied by down-regulation of systemic anaphylaxis mediators such as histamine and mast cell protease-1 (MCPT-1) in the microneedles treated group. Overall, there was an up-regulation of Th1 cytokines (IL-2 and IFN-γ) as compared to Th2 cytokines (IL-4 and IL-5) in splenocyte culture supernatants of the microneedle treated group as compared to untreated group, suggesting that microneedles promoted immune modulation towards the Th1 pathway. Furthermore, mice treated with PE-coated microneedles were observed to retain integrity of their small intestine villi and had reduced eosinophilic infiltration as compared to the untreated but peanut sensitized mice, which further confirmed the desensitization capability of peanut cutaneous immunotherapy using coated microneedles. Thus, our current study represents a novel minimally invasive microneedle based cutaneous immunotherapy, which may provide a novel route of desensitization for the treatment of peanut allergies.

Identification of a T follicular helper cell subset that drives anaphylactic IgE

Cross-linking of high-affinity immunoglobulin E (IgE) results in the life-threatening allergic reaction anaphylaxis. Yet the cellular mechanisms that induce B cells to produce IgE in response to allergens remain poorly understood. T follicular helper (T_FH) cells direct the affinity and isotype of antibodies produced by B cells. Although T_FH cell-derived interleukin-4 (IL-4) is necessary for IgE production, it is not sufficient. We report a rare population of IL-13-producing T_FH cells present in mice and humans with IgE to allergens, but not when allergen-specific IgE was absent or only low-affinity. These "T_FH13" cells have an unusual cytokine profile (IL-13^hiIL-4^hiIL-5^hiIL-21^lo) and coexpress the transcription factors BCL6 and GATA3. T_FH13 cells are required for production of high- but not low-affinity IgE and subsequent allergen-induced anaphylaxis. Blocking T_FH13 cells may represent an alternative therapeutic target to ameliorate anaphylaxis.

Exploring the Science behind Bifidobacterium breve M-16V in Infant Health

Probiotics intervention has been proposed as a feasible preventative approach against adverse health-related complications in infants. Nevertheless, the umbrella concept of probiotics has led to a massive application of probiotics in a range of products for promoting infant health, for which the strain-specificity, safety and efficacy findings associated with a specific probiotics strain are not clearly defined. Bifidobacterium breve M-16V is a commonly used probiotic strain in infants. M-16V has been demonstrated to offer potential in protecting infants from developing the devastating necrotising enterocolitis (NEC) and allergic diseases. This review comprehends the potential beneficial effects of M-16V on infant health particularly in the prevention and treatment of premature birth complications and immune-mediated disorders in infants. Mechanistic studies supporting the use of M-16V implicated that M-16V is capable of promoting early gut microbial colonisation and may be involved in the regulation of immune balance and inflammatory response to protect high-risk infants from NEC and allergies. Summarised information on M-16V has provided conceptual proof of the use of M-16V as a potential probiotics candidate aimed at promoting infant health, particularly in the vulnerable preterm population.

Role of allergen-specific T-follicular helper cells in immunotherapy

PURPOSE OF REVIEW

The discovery of novel T-cell subsets including follicular helper T (Tfh) cells has broadened our knowledge on the complex immune networks in allergic diseases. This review summarizes the evidence for Tfh cells in controlling immune responses to allergens with a particular focus on immunoglobulin E (IgE) production and discusses the implication of such regulation in allergen-specific immunotherapy.

RECENT FINDINGS

Tfh cells support the production of IgE in animal models for allergic diseases. Among Tfh cells, the type 2 subset (Tfh2) is considered as the major player that secretes IL-4 and promotes the isotype switching to IgE. In human inflammatory airway diseases, including allergic rhinitis, asthma, and nasal polyps, the increased frequencies of circulating or tissue Tfh2 cells have been reported. Notably, the frequencies of Dermatophagoides pteronyssinus group 1 (Der p 1)-specific IL-4 Tfh cells in blood positively correlated with serum Der p-specific IgE levels in allergic rhinitis patients. After allergen immunotherapy (AIT), Der p 1-specific IL-4 Tfh cells declined in allergic rhinitis patients, which associated with the remission of clinical symptoms.

SUMMARY

Allergen-specific IL-4 Tfh cells contribute to the production of allergen-specific IgE and correlate with clinical efficacy of AIT in allergic rhinitis patients, which suggest allergen-specific Tfh cells as a promising therapeutic target and biomarker for AIT in allergic rhinitis.

Single-cell RNA-Seq analysis identifies a noncoding interleukin 4 (IL-4) RNA that post-transcriptionally up-regulates IL-4 production in T helper cells

High-throughput sequencing has revealed a tremendous complexity of cellular transcriptomes, which is partly due to the generation of multiple alternative transcripts from a single gene locus. Because alternative transcripts often have low abundance in bulk cells, the functions of most of these transcripts and their relationship with their canonical counterparts remain unclear. Here we applied single-cell RNA-Seq to analyze the transcriptome complexity of in vitro-differentiated, murine type 2 T helper (Th2) cells. We found that cytokine gene transcripts contribute most of the intercellular heterogeneity, with a group of universal cytokines, including interleukins 1a, 2, 3, and 16, being bimodally expressed. At the single-cell level, use of alternative promoters prevalently generated alternative transcripts. For instance, although undetectable in bulk cells, a noncoding RNA isoform of IL-4 (IL4nc), which was driven by an intronic promoter in the IL-4 locus, was predominantly expressed in a subset of Th2 cells. IL4nc displayed distinct temporal expression patterns compared with the canonical IL-4 mRNA and post-transcriptionally promoted the production of IL-4 protein in Th2 cells. In conclusion, our findings reveal a mechanism whereby minor noncanonical transcripts post-transcriptionally regulate expression of their cognate canonical genes.

Hierarchical control of interleukin 13 (IL-13) signals in lung fibroblasts by STAT6 and SOX11

Interleukin (IL)-13 is a signature cytokine of type 2 inflammation important for the pathogenesis of various diseases, including allergic diseases. Signal transducer and activator of transcription (STAT) 6 is a critical transcriptional factor for the IL-13 signals; however, it remains unknown how expression of the IL-13-induced genes is differentiated by the transcriptional machineries. In this study, we identified IL-13-induced transcriptional factors in lung fibroblasts using DNA microarrays in which SOX11 was included. Knockdown of SOX11 down-regulated expression of periostin and CCL26, both of which are known to be downstream molecules of IL-13, whereas enforced expression of SOX11 together with IL-13 stimulation enhanced expression of periostin. Moreover, we found that in DNA microarrays combining IL-13 induction and SOX11 knockdown there exist both SOX11-dependent and -independent molecules in IL-13-inducible molecules. In the former, many inflammation-related and fibrosis-related molecules, including periostin and CCL26, are involved. These results suggest that SOX11 acts as a trans-acting transcriptional factor downstream of STAT6 and that in lung fibroblasts the IL-13 signals are hierarchically controlled by STAT6 and SOX11.

Allergic patients with and without allergen-specific immunotherapy mount protective immune responses to tick-borne encephalitis vaccination in absence of enhanced side effects or propagation of their Th2 bias

BACKGROUND

Allergic diseases are caused by Th2-driven immune responses and their treatment with specific immunotherapy (SIT) leads to immunomodulation via IL10, TGF-ß and Th1/Tr1 shift. This phase IV, open-label clinical trial investigated whether allergies and SIT treatment influenced immune responses to routine vaccination.

METHODS

We studied three groups: 49 allergic patients (allergic group), 21 allergic patients receiving maintenance doses of SIT (SIT group), and 49 non-allergic controls. All subjects received tick-borne encephalitis (TBE) booster vaccines and humoral and cellular immune responses were evaluated after one week, four weeks and six months.

RESULTS

The levels and kinetics of neutralizing TBE-specific antibodies, reflecting protection against TBE, were not significantly different in the three groups. The allergic group showed Th2 polarization pre-booster as indicated by increased TBE-specific IgG1 and elevated mitogen-induced IL5 production. Alum-adjuvanted TBE vaccine led to Th2 biased immune responses in the controls, but to no further enhancement of Th2 polarization in the allergic and SIT group. Furthermore, in the SIT group cellular parameters reflected the induction of immunomodulation due to increased Tregs, elevated baseline IL10 and lack of TBE-specific IL5. Importantly, these cellular regulatory responses did not limit the ability to mount sufficient TBE-specific antibodies after the booster. All groups tolerated the vaccine well with no exacerbation of allergic symptoms.

CONCLUSION

TBE booster vaccinations were immunogenic and safe in both the allergic and SIT group and contributed to balanced immune responses. Our data indicate that all allergic patients, even when undergoing SIT, should be vaccinated without hesitation and at regular intervals according to standard recommendations. ClinicalTrials.gov (NCT02511535).

Periostin in inflammation and allergy

We found for the first time that IL-4 and IL-13, signature type 2 cytokines, are able to induce periostin expression. We and others have subsequently shown that periostin is highly expressed in chronic inflammatory diseases-asthma, atopic dermatitis, eosinophilc chronic sinusitis/chronic rhinosinusitis with nasal polyp, and allergic conjunctivitis-and that periostin plays important roles in the pathogenesis of these diseases. The epithelial/mesenchymal interaction via periostin is important for the onset of allergic inflammation, in which periostin derived from fibroblasts acts on epithelial cells or fibroblasts, activating their NF-κB. Moreover, the immune cell/non-immune cell interaction via periostin may be also involved. Now the significance of periostin has been expanded into other inflammatory or fibrotic diseases such as scleroderma and pulmonary fibrosis. The cross-talk of periostin with TGF-β or pro-inflammatory cytokines is important for the underlying mechanism of these diseases. Because of its pathogenic importance and broad expression, diagnostics or therapeutic drugs can be potentially developed to target periostin as a means of treating these diseases.

The Significance of Hypothiocyanite Production via the Pendrin/DUOX/Peroxidase Pathway in the Pathogenesis of Asthma

Inhaled corticosteroids (ICSs) are used as first-line drugs for asthma, and various novel antiasthma drugs targeting type 2 immune mediators are now under development. However, molecularly targeted drugs are expensive, creating an economic burden on patients. We and others previously found pendrin/SLC26A4 as a downstream molecule of IL-13, a signature type 2 cytokine critical for asthma, and showed its significance in the pathogenesis of asthma using model mice. However, the molecular mechanism of how pendrin causes airway inflammation remained elusive. We have recently demonstrated that hypothiocyanite (OSCN⁻) produced by the pendrin/DUOX/peroxidase pathway has the potential to cause airway inflammation. Pendrin transports thiocyanate (SCN⁻) into pulmonary lumens at the apical side. Peroxidases catalyze SCN⁻ and H₂O₂ generated by DUOX into OSCN⁻. Low doses of OSCN⁻ activate NF-κB in airway epithelial cells, whereas OSCN⁻ in high doses causes necrosis of the cells, inducing the release of IL-33 and accelerating inflammation. OSCN⁻ production is augmented in asthma model mice and possibly in some asthma patients. Heme peroxidase inhibitors, widely used as antithyroid agents, diminish asthma-like phenotypes in mice, indicating the significance of this pathway. These findings suggest the possibility of repositioning antithyroid agents as antiasthma drugs.