Lack of IL-4-induced Th2 response and IgE class switching in mice with disrupted Stat6 gene

John AL. Maternal IgE Influence on Fetal and Infant Health

Immunoglobulin E (IgE) is the most recently discovered and evolved mammalian antibody type, best known for interacting with mast cells (MCs) as immune effectors. IgE-mediated antigen sensing by MC provides protection from parasites, venomous animals, bacteria, and other insults to barrier tissues exposed to the environment. IgE and MCs act as inflammation amplifiers and immune response adjuvants. Thus, IgE production and memory formation are greatly constrained and require specific licensing. Failure of regulation gives rise to allergic disease, one of the top causes of chronic illness. Increasing evidence suggests allergy development often starts early in life, including prenatally, with maternal influence being central in shaping the offspring's immune system. Although IgE often exists before birth, an endogenous source of IgE-producing B cells has not been identified. This review discusses the mechanisms of maternal IgE transfer into the offspring, its interactions with offspring MCs and antigen-presenting cells, and the consequences for allergic inflammation and allergen sensitization development. We discuss the multifaceted effects of pre-existing IgG, IgE, and their glycosylation on maternal IgE transfer and functionality in the progeny. Understanding the IgE-mediated mechanisms predisposing for early life allergy development may allow their targeting with existing therapeutics and guide the development of new ones.

Canthaxanthin ameliorates atopic dermatitis in mice by suppressing Th2 immune response

Atopic dermatitis (AD) is a prevalent chronic inflammatory skin disorder characterized by intense pruritus and complex immunopathogenic mechanisms. Recent evidence has highlighted the critical link between dysregulated intestinal microecology and altered immune responses in AD progression. As essential components of the intestinal microenvironment, metabolites play pivotal roles in various physiological processes. Through metabolomic profiling in an AD mouse model, we identified a significant reduction in canthaxanthin (CTX), a bacterial-derived metabolite naturally present in many foods, in AD mice compared to healthy controls. To investigate the therapeutic potential of CTX, we established an AD model by repeatedly applying 2,4-dinitrochlorobenzene (DNCB) to the ears and dorsal skin of mice, successfully inducing AD-like symptoms and lesions. Notably, oral administration of CTX significantly attenuated skin inflammation and reduced serum IgE levels in this DNCB-induced AD model. Both in vivo and in vitro studies demonstrated that CTX treatment effectively suppressed Th2 immune responses. Mechanistically, we found that CTX significantly inhibited the activation of the JAK2-STAT6 signaling pathway in Th2-polarized T cells. Our findings not only demonstrate the therapeutic efficacy of CTX in AD but also elucidate its molecular mechanism in modulating T helper cell subset balance. These insights suggest that CTX could serve as a promising therapeutic agent for AD and potentially other Th2 response-mediated immune disorders.

CCR2 signaling regulates anti-chlamydia T cell immune responses in the airway

CCR2, a member of the G protein-coupled receptor (GPCR) superfamily, is widely expressed on monocytes, macrophages, activated T cells, and other cell types, and plays a critical role in coordinating the immune response to various infections. Here we demonstrate that CCR2 expression is significantly elevated during Chlamydia muridarum (C. muridarum) respiratory infection, and its absence leads to exacerbated susceptibility, as evidenced by significant weight loss, higher bacterial loads, severe lung pathology, and elevated levels of inflammatory cytokines (il-1β, tnfα, and il-6). The absence of ccr2 impairs both myeloid cell infiltration and T cell responses, which are crucial for effective immune defense. Specifically, ccr2 deficiency disrupts the differentiation and response of Th1 cells, which are the primary effector lineage responsible for clearing chlamydia through secretion of interferon-gamma (IFN-γ). As a result, there is a significant decrease in CD3+CD4+IFN-γ+ T cells in the lung and spleen, accompanied by reduced levels of IFN-γ protein and mRNA, as well as downregulated mRNA expression of Th1-promoting cytokines (il-12p35, il-12p40) and transcription factors (stat4, T-bet), which play crucial roles in Th1 differentiation. Moreover, ccr2 deficiency greatly diminishes STAT1 phosphorylation, a key regulator of IFN-γ secretion by Th1 cells. Meanwhile, we also observed a significant reduction in IFN-γ secretion by CD8+ T cells following ccr2 deficiency. Conversely, ccr2-/- mice exhibit an exaggerated Th2-type immune response, with elevated levels of Th2-promoting cytokines (IL-4), transcription factors (STAT6 and gata3), and il-5, which together lead to more severe lung tissue damage and increased susceptibility to infection. Furthermore, these mice show higher levels of IL-17 along with an enhanced Th17-type immune response, characterized by increased Th17-promoting cytokines TGFB, transcription factors stat3 and RORγt, and il-21, suggesting a compensatory mechanism that drives neutrophil infiltration to exacerbate lung inflammation. These findings underscore the pivotal role of CCR2, a chemokine receptor, in orchestrating the immune response to Chlamydia infection by facilitating Th1 cells differentiation while restraining Th2-type and Th17-type immune responses, thereby alleviating pulmonary inflammation.

Genome-scale spatial mapping of the Hodgkin lymphoma microenvironment identifies tumor cell survival factors

A key challenge in cancer research is to identify the secreted factors that contribute to tumor cell survival. Nowhere is this more evident than in Hodgkin lymphoma, where malignant Hodgkin Reed Sternberg (HRS) cells comprise only 1-5% of the tumor mass, the remainder being infiltrating immune cells that presumably are required for the survival of the HRS cells. Until now, there has been no way to characterize the complex Hodgkin lymphoma tumor microenvironment at genome scale. Here, we performed genome-wide transcriptional profiling with spatial and single-cell resolution. We show that the neighborhood surrounding HRS cells forms a distinct niche involving 31 immune and stromal cell types and is enriched in CD4+ T cells, myeloid and follicular dendritic cells, while being depleted of plasma cells. Moreover, we used machine learning to nominate ligand-receptor pairs enriched in the HRS cell niche. Specifically, we identified IL13 as a candidate survival factor. In support of this hypothesis, recombinant IL13 augmented the proliferation of HRS cells in vitro. In addition, genome-wide CRISPR/Cas9 loss-of-function studies across more than 1,000 human cancer cell lines showed that IL4R and IL13RA1, the heterodimeric partners that constitute the IL13 receptor, were uniquely required for the survival of HRS cells. Moreover, monoclonal antibodies targeting either IL4R or IL13R phenocopied the genetic loss of function studies. IL13-targeting antibodies are already FDA-approved for atopic dermatitis, suggesting that clinical trials testing such agents should be explored in patients with Hodgkin lymphoma.

Translating tissue expression of STAT 1, 3 and 6 in prurigo nodularis to clinical efficacy of oral tofacitinib - A prospective single-arm investigational study

Background Interleukin (IL)-4, IL-13, IL-17, IL-22 and IL-3 are overexpressed in prurigo nodularis (PN). They mediate their action via the Janus Kinase (JAK) Signal transducer and activator of transcription (STAT) pathway. Objectives Our aim was to study the expression of tissue STAT1, STAT3, and STAT6, as well as the efficacy of the JAK-STAT inhibitor, tofacitinib, in PN. Methods A prospective study was conducted in a tertiary care hospital. Patients with PN were recruited after excluding secondary causes. Pruritus was graded using Pruritus Grading System Score (PGSS). All cases underwent histological assessment using immunohistochemical markers for STAT1, STAT3, and STAT6 in both lesional and perilesional skin. Tofacitinib was initiated at a dose of 5 mg twice daily or 11 mg once daily and then tapered to a maintenance dose. The final PGSS at the time of data evaluation, as well as the occurrence of remissions and relapses, was assessed. Results The majority of the 17 patients included in the study had moderate to severe disease. Immunohistochemical analysis revealed marked tissue expression of STAT6 in 13 and STAT3 in 10 patients, while STAT1 expression was seen in only 4 patients [p < 0.05], suggesting a Th2/Th17 tissue response. The mean onset of action of tofacitinib was 11.2 ± 6.44 days and the mean duration of treatment was 5.6 ± 2.2 months. A significant reduction in PGSS was noted after treatment (66.1%, P value 0.0004). Fourteen of the patients maintained remission on low-dose therapy (5 mg OD or A/D) while one patient experienced a relapse. No serious adverse effects were noted. Limitation We could not study the tissue cytokines and the expression of STATs after achieving clinical response on oral tofacitinib. Conclusion The efficacy of tofacitinib in PN is based on its inhibitory effect on Th2 and Th17 cytokines, which is dependent on STAT6 and STAT3.

A partial loss-of-function variant in STAT6 protects against type 2 asthma

BACKGROUND

Signal transducer and activator of transcription 6 (STAT6) is central to type 2 (T2) inflammation, and common noncoding variants at the STAT6 locus associate with various T2 inflammatory traits, including diseases, and its pathway is widely targeted in asthma treatment.

OBJECTIVE

We sought to test the association of a rare missense variant in STAT6, p.L406P, with T2 inflammatory traits, including the risk of asthma and allergic diseases, and to characterize its functional consequences in cell culture.

METHODS

The association of p.L406P with plasma protein levels, white blood cell counts, and the risk of asthma and allergic phenotypes was tested. Significant associations in other cohorts were also tested using a burden test. The effects of p.L406P on STAT6 protein function were examined in cell lines and by comparing CD4+ T-cell responses from carriers and noncarriers of the variant.

RESULTS

p.L406P associated with reduced plasma levels of STAT6 and IgE as well as with lower eosinophil and basophil counts in blood. It also protected against asthma, mostly driven by severe T2-high asthma. p.L406P led to lower IL-4-induced activation in luciferase reporter assays and lower levels of STAT6 in CD4+ T cells. We identified multiple genes with expression that was affected by the p.L406P genotype on IL-4 treatment of CD4+ T cells; the effect was consistent with a weaker IL-4 response in carriers than in noncarriers of p.L406P.

CONCLUSIONS

A partial loss-of-function variant in STAT6 resulted in dampened IL-4 responses and protection from T2-high asthma, implicating STAT6 as an attractive therapeutic target.

T follicular helper and memory B cells in IgE recall responses

IgE antibodies raised against innocuous environmental antigens cause allergic diseases like allergic rhinitis, food allergy, and allergic asthma. While some allergies are often outgrown, others (peanut, shellfish, tree nut) are lifelong in the majority of individuals. Lifelong allergies are the result of persistent production of allergen-specific IgE. However, IgE antibodies and the plasma cells that secrete them tend to be short-lived. Persistent allergen-specific IgE titres are thought to be derived from the continued renewal of IgE plasma cells from memory B cells in response to allergen encounters. The initial generation of allergen-specific IgE is driven by B cell activation by IL-4 producing Tfh cells, but the cellular and molecular mechanisms of the long-term production of IgE are poorly characterized. This review investigates the mechanisms governing IgE production and Tfh activation in the primary and recall responses, towards the objective of identifying molecular targets for therapeutic intervention that durably inactivate the IgE recall response.

Combination of live attenuated and adenovirus-based vaccines completely protects interferon gamma (IFNγ) knockout mice against pneumonic plague

Two live attenuated vaccines (LAVs), LMA and LMP, were evaluated alone or in combination with a trivalent adenoviral vector-based vaccine (Ad5-YFV) for their efficacy and immune responses in wild type (WT) and interferon gamma (IFNγ) knockout (KO) mice in a C57BL/6 background. While LMA and LMP are triple deletion mutants of Yersinia pestis CO92 strain, Ad5-YFV incorporates three protective plague immunogens. An impressive 80-100% protection was observed in all vaccinated animals against highly lethal intranasal challenge doses of parental Y. pestis CO92. All vaccinated mice generated robust humoral and cellular immune responses. The immunized WT mice showed overall better antibody responses in both serum and bronchoalveolar lavage fluid with much higher percentages of polyfunctional T cell populations. On the other hand, vaccinated IFNγ KO mice displayed better B cell activity in germinal centers with higher percentages of activated antigen specific T cells and memory T cells. In addition, depletion of IFNγ and tumor necrosis factor alpha (TNFα) from immunized WT mice prior to and during infection did not reduce protection against pulmonary Y. pestis CO92 challenge. These data demonstrated a dispensable nature of IFNγ in mediating protection by the aforementioned vaccines. This is the first detailed immunogenicity study of two plague LAVs administered either alone or in combination with an Ad5-YFV vaccine in a prime-boost immunization strategy in IFNγ KO mice. Further, by combining advantages of live-attenuated and adenovirus-based vaccines, augmentation of generalized immune responses were observed which could be beneficial in providing long-lasting immunity in the host.

NAB2-STAT6 drives an EGR1-dependent neuroendocrine program in Solitary Fibrous Tumors

The pathogenesis of many rare tumor types is poorly understood, preventing the design of effective treatments. Solitary fibrous tumors (SFTs) are neoplasms of mesenchymal origin that affect 1/1,000,000 individuals every year and are clinically assimilated to soft tissue sarcomas. SFTs can arise throughout the body and are usually managed surgically. However, 30-40% of SFTs will relapse local-regionally or metastasize. There are no systemic therapies with durable activity for malignant SFTs to date. The molecular hallmark of SFTs is a gene fusion between the NAB2 and STAT6 loci on chromosome 12, resulting in a chimeric protein of poorly characterized function called NAB2-STAT6. We use primary samples and an inducible cell model to discover that NAB2-STAT6 operates as a transcriptional coactivator for a specific set of enhancers and promoters that are normally targeted by the EGR1 transcription factor. In physiological conditions, NAB2 is primarily localized to the cytoplasm and only a small nuclear fraction is available to operate as a co-activator of EGR1 targets. NAB2-STAT6 redirects NAB1, NAB2, and additional EGR1 to the nucleus and bolster the expression of neuronal EGR1 targets. The STAT6 moiety of the fusion protein is a major driver of its nuclear localization and further contributes to NAB2's co-activating abilities. In primary tumors, NAB2-STAT6 activates a neuroendocrine gene signature that sets it apart from most sarcomas. These discoveries provide new insight into the pathogenesis of SFTs and reveal new targets with therapeutic potential.

Pathophysiology of Congenital High Production of IgE and Its Consequences: A Narrative Review Uncovering a Neglected Setting of Disorders

Elevated serum IgE levels serve as a critical marker for uncovering hidden immunological disorders, particularly inborn errors of immunity (IEIs), which are often misdiagnosed as common allergic conditions. IgE, while typically associated with allergic diseases, plays a significant role in immune defense, especially against parasitic infections. However, extremely high levels of IgE can indicate more severe conditions, such as Hyper-IgE syndromes (HIES) and disorders with similar features, including Omenn syndrome, Wiskott-Aldrich syndrome, and IPEX syndrome. Novel insights into the genetic mutations responsible for these conditions highlight their impact on immune regulation and the resulting clinical features, including recurrent infections, eczema, and elevated IgE. This narrative review uniquely integrates recent advances in the genetic understanding of IEIs and discusses how these findings impact both diagnosis and treatment. Additionally, emerging therapeutic strategies, such as hematopoietic stem cell transplantation (HSCT) and gene therapies, are explored, underscoring the potential for personalized treatment approaches. Emphasizing the need for precise diagnosis and tailored interventions aims to enhance patient outcomes and improve the quality of care for those with elevated IgE levels and associated immunological disorders.

T follicular regulatory cells in food allergy promote IgE via IL-4

T follicular regulatory (TFR) cells are found in the germinal center (GC) response and, along with T follicular helper (TFH) cells, help to control the development of high-affinity antibodies (Ab). Although TFR cells are generally thought to repress GC B cells and the Ab response, we have previously shown that in a mouse food allergy model, TFR cells produce IL-10 and play an essential helper role such that in the absence of TFR cells, IgE responses are diminished. Here we show that in this food allergy response, TFR cells produced IL-4 that promotes the generation of antigen-specific IgE. We show that food allergy-primed TFR cells specifically upregulate IL-4 gene transcription and produce functional IL-4 that promoted IgE responses both in vitro and in vivo. We determined that IgE responses are dependent on a high level of IL-4 produced by follicular T cells in the GC, explaining the need for IL-4 produced by TFR cells in the food allergy response. Overall, our findings have demonstrated that in food allergy, TFR cells can produce IL-4 and regulate IgE in a manner that augments the role of TFH cells in IgE responses.

Whence and wherefore IgE?

Despite the near ubiquitous presence of Ig-based antibodies in vertebrates, IgE is unique to mammals. How and why it emerged remains mysterious. IgE expression is greatly constrained compared to other IgH isotypes. While other IgH isotypes are relatively abundant, soluble IgE has a truncated half-life, and IgE plasma cells are mostly short-lived. Despite its rarity, IgE is consequential and can trigger life-threatening anaphylaxis. IgE production reflects a dynamic steady state with IgG memory B cells feeding short-lived IgE production. Emerging evidence suggests that IgE may also potentially be produced in longer-lived plasma cells as well, perhaps as an aberrancy stemming from its evolutionary roots from an antibody isotype that likely functioned more like IgG. As a late derivative of an ancient systemic antibody system, the benefits of IgE in mammals likely stems from the antibody system's adaptive recognition and response capability. However, the tendency for massive, systemic, and long-lived production, common to IgH isotypes like IgG, were likely not a good fit for IgE. The evolutionary derivation of IgE from an antibody system that for millions of years was good at antigen de-sensitization to now functioning as a highly specialized antigen-sensitization function required heavy restrictions on antibody production-insufficiency of which may contribute to allergic disease.

STAT4 and STAT6, their role in cellular and humoral immunity and in diverse human diseases

Signal transducer and activator of transcription (STAT) 4 and STAT6 play a crucial role in immune cells by transducing signals from specific cytokine receptors, and inducing transcription of genes involved in cell-mediated and humoral immunity. These two different defense mechanisms against pathogens are regulated by two specific CD4+ T helper (Th) cells known as Th1 and Th2 cells. Many studies have shown that several diseases including cancer, inflammatory, autoimmune and allergic diseases are associated with a Th1/Th2 imbalance caused by increased or decreased expression/activity of STAT4 or STAT6 often due to genetic and epigenetic aberrances. An altered expression of STAT4 has been observed in different tumors and autoimmune diseases, while a dysregulation of STAT6 signaling pathway is frequently observed in allergic conditions, such as atopic dermatitis, allergic asthma, food allergy, and tumors such as Hodgkin and non-Hodgkin lymphomas. Recently, dysregulations of STAT4 and STAT6 expression have been observed in SARS-CoV2 and monkeypox infections, which are still public health emergencies in many countries. SARS-CoV-2 can induce an imbalance in Th1 and Th2 responses with a predominant activation of STAT6 in the cytosol and nuclei of pneumocytes that drives Th2 polarization and cytokine storm. In monkeypox infection the virus can promote an immune evasion by inducing a Th2 response that in turn inhibits the Th1 response essential for virus elimination. Furthermore, genetic variations of STAT4 that are associated with an increased risk of developing systemic lupus erythematosus seem to play a role in defense against SARS-CoV-2 infection.

Regulation of T helper cell differentiation by the interplay between histone modification and chromatin interaction

The development and function of the immune system are controlled by temporospatial gene expression programs, which are regulated by cis-regulatory elements, chromatin structure, and trans-acting factors. In this study, we cataloged the dynamic histone modifications and chromatin interactions at regulatory regions during T helper (Th) cell differentiation. Our data revealed that the H3K4me1 landscape established by MLL4 in naive CD4+ T cells is critical for restructuring the regulatory interaction network and orchestrating gene expression during the early phase of Th differentiation. GATA3 plays a crucial role in further configuring H3K4me1 modification and the chromatin interaction network during Th2 differentiation. Furthermore, we demonstrated that HSS3-anchored chromatin loops function to restrict the activity of the Th2 locus control region (LCR), thus coordinating the expression of Th2 cytokines. Our results provide insights into the mechanisms of how the interplay between histone modifications, chromatin looping, and trans-acting factors contributes to the differentiation of Th cells.

The barrier-protective effect of β-eudesmol against type 2-inflammatory cytokine-induced tight junction disassembly in airway epithelial cells

Allergic inflammation, which is the pathogenesis of allergic rhinitis and asthma, is associated with disruption of the airway epithelial barrier due to the effects of type 2 inflammatory cytokines, i.e. interleukin-4 and interleukin-13 (IL-4/13). The anti-allergic inflammatory effect of β-eudesmol (BE) on the tight junction (TJ) of the airway epithelium has not previously been reported. Herein, the barrier protective effect of BE was determined by measurement of transepithelial electrical resistance and by paracellular permeability assay in an IL-4/13-treated 16HBE14o- monolayer. Pre-treatment of BE concentration- and time- dependently inhibited IL-4/13-induced TJ barrier disruption, with the most significant effect observed at 20 μM. Cytotoxicity analyses showed that BE, either alone or in combination with IL-4/13, had no effect on cell viability. Western blot and immunofluorescence analyses showed that BE inhibited IL-4/13-induced mislocalization of TJ components, including occludin and zonula occludens-1 (ZO-1), without affecting the expression of these two proteins. In addition, the mechanism of the TJ-protective effect of BE was mediated by inhibition of IL-4/13-induced STAT6 phosphorylation, in which BE might serve as an antagonist of cytokine receptors. In silico molecular docking analysis demonstrated that BE potentially interacted with the site I pocket of the type 2 IL-4 receptor, likely at Asn-126 and Tyr-127 amino acid residues. It can therefore be concluded that BE is able to prevent IL-4/13-induced TJ disassembly by interfering with cytokine-receptor interaction, leading to suppression of STAT6-induced mislocalization of occludin and ZO-1. BE is a promising candidate for a therapeutic intervention for inflammatory airway epithelial disorders driven by IL-4/13.

Tissue adaptation of CD4 T lymphocytes in homeostasis and cancer

The immune system is traditionally classified as a defense system that can discriminate between self and non-self or dangerous and non-dangerous situations, unleashing a tolerogenic reaction or immune response. These activities are mainly coordinated by the interaction between innate and adaptive cells that act together to eliminate harmful stimuli and keep tissue healthy. However, healthy tissue is not always the end point of an immune response. Much evidence has been accumulated over the years, showing that the immune system has complex, diversified, and integrated functions that converge to maintaining tissue homeostasis, even in the absence of aggression, interacting with the tissue cells and allowing the functional maintenance of that tissue. One of the main cells known for their function in helping the immune response through the production of cytokines is CD4+ T lymphocytes. The cytokines produced by the different subtypes act not only on immune cells but also on tissue cells. Considering that tissues have specific mediators in their architecture, it is plausible that the presence and frequency of CD4+ T lymphocytes of specific subtypes (Th1, Th2, Th17, and others) maintain tissue homeostasis. In situations where homeostasis is disrupted, such as infections, allergies, inflammatory processes, and cancer, local CD4+ T lymphocytes respond to this disruption and, as in the healthy tissue, towards the equilibrium of tissue dynamics. CD4+ T lymphocytes can be manipulated by tumor cells to promote tumor development and metastasis, making them a prognostic factor in various types of cancer. Therefore, understanding the function of tissue-specific CD4+ T lymphocytes is essential in developing new strategies for treating tissue-specific diseases, as occurs in cancer. In this context, this article reviews the evidence for this hypothesis regarding the phenotypes and functions of CD4+ T lymphocytes and compares their contribution to maintaining tissue homeostasis in different organs in a steady state and during tumor progression.

Neuroimmune interplay during type 2 inflammation: Symptoms, mechanisms, and therapeutic targets in atopic diseases

Type 2 inflammation is characterized by overexpression and heightened activity of type 2 cytokines, mediators, and cells that drive neuroimmune activation and sensitization to previously subthreshold stimuli. The consequences of altered neuroimmune activity differ by tissue type and disease; they include skin inflammation, sensitization to pruritogens, and itch amplification in atopic dermatitis and prurigo nodularis; airway inflammation and/or hyperresponsiveness, loss of expiratory volume, airflow obstruction and increased mucus production in asthma; loss of sense of smell in chronic rhinosinusitis with nasal polyps; and dysphagia in eosinophilic esophagitis. We describe the neuroimmune interactions that underlie the various sensory and autonomic pathologies in type 2 inflammatory diseases and present recent advances in targeted treatment approaches to reduce type 2 inflammation and its associated symptoms in these diseases. Further research is needed to better understand the neuroimmune mechanisms that underlie chronic, sustained inflammation and its related sensory pathologies in diseases associated with type 2 inflammation.

STAT6 mutations enriched at diffuse large B-cell lymphoma relapse reshape the tumor microenvironment

Diffuse large B-cell lymphoma (DLBCL) relapses in approximately 40% of patients following frontline therapy. We reported that STAT6D419 mutations are enriched in relapsed/refractory DLBCL (rrDLBCL) samples, suggesting that JAK/STAT signaling plays a role in therapeutic resistance. We hypothesized that STAT6D419 mutations can improve DLBCL cell survival by reprogramming the microenvironment to sustain STAT6 activation. Thus, we investigated the role of STAT6D419 mutations on DLBCL cell growth and its microenvironment. We found that phospho-STAT6D419N was retained in the nucleus longer than phospho-STAT6WT following IL-4 stimulation, and STAT6D419N recognized a more restricted DNA-consensus sequence than STAT6WT. Upon IL-4 induction, STAT6D419N expression led to a higher magnitude of gene expression changes, but in a more selective list of gene targets compared with STATWT. The most significantly expressed genes induced by STAT6D419N were those implicated in survival, proliferation, migration, and chemotaxis, in particular CCL17. This chemokine, also known as TARC, attracts helper T-cells to the tumor microenvironment, especially in Hodgkin's lymphoma. To this end, in DLBCL, phospho-STAT6+ rrDLBCL cells had a greater proportion of infiltrating CD4+ T-cells than phospho-STAT6- tumors. Our findings suggest that STAT6D419 mutations in DLBCL lead to cell autonomous changes, enhanced signaling, and altered composition of the tumor microenvironment.

Exploring Novel Frontiers: Leveraging STAT3 Signaling for Advanced Cancer Therapeutics

Signal Transducer and Activator of Transcription 3 (STAT3) plays a significant role in diverse physiologic processes, including cell proliferation, differentiation, angiogenesis, and survival. STAT3 activation via phosphorylation of tyrosine and serine residues is a complex and tightly regulated process initiated by upstream signaling pathways with ligand binding to receptor and non-receptor-linked kinases. Through downstream deregulation of target genes, aberrations in STAT3 activation are implicated in tumorigenesis, metastasis, and recurrence in multiple cancers. While there have been extensive efforts to develop direct and indirect STAT3 inhibitors using novel drugs as a therapeutic strategy, direct clinical application remains in evolution. In this review, we outline the mechanisms of STAT3 activation, the resulting downstream effects in physiologic and malignant settings, and therapeutic strategies for targeting STAT3. We also summarize the pre-clinical and clinical evidence of novel drug therapies targeting STAT3 and discuss the challenges of establishing their therapeutic efficacy in the current clinical landscape.

Transcriptome analysis of turbot (Scophthalmus maximus) kidney responses to inactivated bivalent vaccine against Aeromonas salmonicida and Edwardsiella tarda

Turbot (Scophthalmus maximus) is a commercially important marine flatfish for global aquaculture. With intensive farming, turbot production is limited by several diseases, in which Aeromonas salmonicida and Edwardsiella tarda are two main causative agents. Vaccination is an effective and safe alternative to disease prevention compared to antibiotic treatment. In the previous study, we developed an inactivated bivalent vaccine against A. salmonicida and E. tarda with relative percent survival (RPS) of 77.1 %. To understand the protection mechanism in molecular basis of the inactivated bivalent vaccine against A. salmonicida and E. tarda, we use RNA-seq to analyze the transcriptomic profile of the kidney tissue after immunization. A total of 391,721,176 clean reads were generated in nine libraries by RNA-seq, and 96.35 % of the clean reads were mapped to the reference genome of S. maximus. 1458 (866 upregulated and 592 downregulated) and 2220 (1131 upregulated and 1089 downregulated) differentially expressed genes (DEGs) were obtained at 2 and 4 weeks post-vaccination, respectively. The DEGs were enriched in several important immune-related GO terms, including cytokine activity, immune response, and defense response. In addition, the analysis of several immune-related genes showed upregulation and downregulation, including pattern recognition receptors, complement system, cytokines, chemokines and immune cell surface markers. Eight DEGs (ccr10, calr, casr, mybpha, cd28, thr18, cd20a.3 and c5) were randomly selected for qRT-PCR analysis, which confirmed the validity of the RNA-seq. Our results provide valuable insight into the immune mechanism of inactivated bivalent vaccine against A. salmonicida and E. tarda in Scophthalmus maximus.

High intestinal isoleucine is a potential risk factor for food allergy by regulating the mTOR/AKT pathway in dendritic cells

Food allergy is a global food safety problem with a growing prevalence. People in industrial regions are more susceptible to allergy, but the mechanisms behind this are not fully understood. In this study, the probiotic Lactobacillus casei Zhang (LcZ) was administered to allergic individuals and the impact on allergy-related factors were determined. LcZ alleviated allergenic responses, and there was a significant correlation between the intestinal isoleucine content and IgE concentration. Metagenomics results suggest that the metabolism of the gut microbiota is a source of isoleucine. In a mouse model of food allergy, a high isoleucine diet exacerbated allergic responses and increased the activity of allergenic dendritic cell. In a dendritic cell model, a protein array revealed that the mTOR/AKT pathway mediated the function of isoleucine, and molecular docking suggested that Sestrin2 could be the potential receptor. Overall, this study revealed the role of isoleucine in promoting food allergy, elucidated the underlying mechanisms, and suggested that a high intake of isoleucine could be a potential risk factor for food allergy.

The origins and longevity of IgE responses as indicated by serological and cellular studies in mice and humans

The existence of long-lived IgE antibody-secreting cells (ASC) is contentious, with the maintenance of sensitization by the continuous differentiation of short-lived IgE+ ASC a possibility. Here, we review the epidemiological profile of IgE production, and give an overview of recent discoveries made on the mechanisms regulating IgE production from mouse models. Together, these data suggest that for most individuals, in most IgE-associated diseases, IgE+ ASC are largely short-lived cells. A subpopulation of IgE+ ASC in humans is likely to survive for tens of months, although due to autonomous IgE B cell receptor (BCR) signaling and antigen-driven IgE+ ASC apoptosis, in general IgE+ ASC probably do not persist for the decades that other ASC are inferred to do. We also report on recently identified memory B cell transcriptional subtypes that are the likely source of IgE in ongoing responses, highlighting the probable importance of IL-4Rα in their regulation. We suggest the field should look at dupilumab and other drugs that prohibit IgE+ ASC production as being effective treatments for IgE-mediated aspects of disease in most individuals.

Type 2 immunity in the brain and brain borders

Recent research in neuroimmunology has revolutionized our understanding of the intricate interactions between the immune system and the central nervous system (CNS). The CNS, an "immune-privileged organ", is now known to be intimately connected to the immune system through different cell types and cytokines. While type 2 immune responses have traditionally been associated with allergy and parasitic infections, emerging evidence suggests that these responses also play a crucial role in CNS homeostasis and disease pathogenesis. Type 2 immunity encompasses a delicate interplay among stroma, Th2 cells, innate lymphoid type 2 cells (ILC2s), mast cells, basophils, and the cytokines interleukin (IL)-4, IL-5, IL-13, IL-25, TSLP and IL-33. In this review, we discuss the beneficial and detrimental roles of type 2 immune cells and cytokines in CNS injury and homeostasis, cognition, and diseases such as tumors, Alzheimer's disease and multiple sclerosis.

Galectin-12 Regulates Immune Responses in the Skin through Sebaceous Glands

Sebaceous glands (SGs) are holocrine glands that produce sebum, which primarily contains lipids that help to maintain the barrier function of the skin. Dysregulated lipid production contributes to the progression of some diseases characterized by dry skin, including atopic dermatitis. Although the lipid production of SGs has been well-studied, few studies have assessed their role in skin immune responses. We found that SGs and sebocytes expressed IL-4 receptor and produced high levels of T helper 2-associated inflammatory mediators after IL-4 treatment, suggesting immunomodulatory effects. Galectin-12 is a lipogenic factor expressed in sebocytes that affects their differentiation and proliferation. Using galectin-12-knockdown sebocytes, we showed that galectin-12 regulated the immune response in cells exposed to IL-4 and promoted CCL26 expression by upregulating peroxisome proliferator-activated receptor-γ. Moreover, galectin-12 suppressed the expression of endoplasmic reticulum stress-response molecules, and CCL26 upregulation by IL-4 was reversed after sebocyte treatment with inducers of endoplasmic reticulum stress, suggesting that galectin-12 controls IL-4 signaling by suppressing endoplasmic reticulum stress. Using galectin-12-knockout mice, we showed that galectin-12 positively regulated the IL-4-induced enlargement of SGs and the development of an atopic dermatitis-like phenotype. Thus, galectin-12 regulates the skin immune response by promoting peroxisome proliferator-activated receptor-γ expression and suppressing endoplasmic reticulum stress in SGs.

The Impact of Air Pollution on Atopic Dermatitis

PURPOSE OF REVIEW

Atopic dermatitis (AD) remains a dermatological disease that imposes a significant burden on society. Air pollution has previously been linked to both the onset and severity of atopic dermatitis. As air pollution remains a critical environmental factor impacting human health, this review seeks to provide an overview of the relationship between different air pollutants and AD.

RECENT FINDINGS

AD can develop from multiple causes that can be broadly grouped into epidermal barrier dysfunction and immune dysregulation. Air pollution imposes significant health risks and includes a wide variety of pollutant types. AD has been linked to outdoor air pollutants such as particulate matter (PM), volatile organic compounds (VOC), gaseous compounds, and heavy metals. Exposure to indoor pollutants such as tobacco smoke and fungal molds has also been associated with an increased incidence of AD. While different pollutants impact distinct molecular pathways in the cell, they mostly converge on ROS product, DNA damage, and dysregulated T-cell activity and cytokine production. The presented review suggests a strengthening tie between air pollution and AD. It points to opportunities for further studies to clarify, as well as potential therapeutic opportunities that leverage the mechanistic relationships between air pollution and AD.

Identification of the biological processes, immune cell landscape, and hub genes shared by acute anaphylaxis and ST-segment elevation myocardial infarction

Background: Patients with anaphylaxis are at risk for ST-segment elevation myocardial infarction (STEMI). However, the pathological links between anaphylaxis and STEMI remain unclear. Here, we aimed to explore shared biological processes, immune effector cells, and hub genes of anaphylaxis and STEMI. Methods: Gene expression data for anaphylactic (GSE69063) and STEMI (GSE60993) patients with corresponding healthy controls were pooled from the Gene Expression Omnibus database. Differential expression analysis, enrichment analysis, and CIBERSORT were used to reveal transcriptomic signatures and immune infiltration profiles of anaphylaxis and STEMI, respectively. Based on common differentially expressed genes (DEGs), Gene Ontology analysis, cytoHubba algorithms, and correlation analyses were performed to identify biological processes, hub genes, and hub gene-related immune cells shared by anaphylaxis and STEMI. The robustness of hub genes was assessed in external anaphylactic (GSE47655) and STEMI (GSE61144) datasets. Furthermore, a murine model of anaphylaxis complicated STEMI was established to verify hub gene expressions. The logistic regression analysis was used to evaluate the diagnostic efficiency of hub genes. Results: 265 anaphylaxis-related DEGs were identified, which were associated with immune-inflammatory responses. 237 STEMI-related DEGs were screened, which were involved in innate immune response and myeloid leukocyte activation. M0 macrophages and dendritic cells were markedly higher in both anaphylactic and STEMI samples compared with healthy controls, while CD4⁺ naïve T cells and CD8⁺ T cells were significantly lower. Enrichment analysis of 33 common DEGs illustrated shared biological processes of anaphylaxis and STEMI, including cytokine-mediated signaling pathway, response to reactive oxygen species, and positive regulation of defense response. Six hub genes were identified, and their expression levels were positively correlated with M0 macrophage abundance and negatively correlated with CD4⁺ naïve T cell abundance. In external anaphylactic and STEMI samples, five hub genes (IL1R2, FOS, MMP9, DUSP1, CLEC4D) were confirmed to be markedly upregulated. Moreover, experimentally induced anaphylactic mice developed impaired heart function featuring STEMI and significantly increased expression of the five hub genes. DUSP1 and CLEC4D were screened as blood diagnostic biomarkers of anaphylaxis and STEMI based on the logistic regression analysis. Conclusion: Anaphylaxis and STEMI share the biological processes of inflammation and defense responses. Macrophages, dendritic cells, CD8⁺ T cells, and CD4⁺ naïve T cells constitute an immune cell population that acts in both anaphylaxis and STEMI. Hub genes (DUSP1 and CLEC4D) identified here provide candidate genes for diagnosis, prognosis, and therapeutic targeting of STEMI in anaphylactic patients.

Requirements of IL-4 during the Generation of B Cell Memory

IL-4 has long been established as a key regulator of Th cells and for promoting effective B cell survival and isotype class switching. Yet, despite having been extensively studied, the specific role of IL-4 in generating humoral memory in vivo is unclear. In this review, we explore the recent studies that unravel the cellular sources and spatiotemporal production of IL-4, the relationship between IL-4 and IL-21 during germinal center responses and the formation of Ab-secreting cells, and the current understanding of whether IL-4 promotes or suppresses memory B cell generation in vitro and in vivo.

Transcriptional regulation on effector T cells in the pathogenesis of psoriasis

Psoriasis is one of the most common inflammatory diseases, characterized by scaly erythematous plaques on the skin. The accumulated evidence on immunopathology of psoriasis suggests that inflammatory reaction is primarily mediated by T helper (Th) cells. The differentiation of Th cells plays important roles in psoriatic progression and it is regulated by transcription factors such as T-bet, GATA3, RORγt, and FOXP3, which can convert naïve CD4+ T cells, respectively, into Th1, Th2, Th17 and Treg subsets. Through the activation of the JAK/STAT and Notch signaling pathways, together with their downstream effector molecules including TNF-α, IFN-γ, IL-17, TGF-β, these subsets of Th cells are then deeply involved in the pathogenesis of psoriasis. As a result, keratinocytes are abnormally proliferated and abundant inflammatory immune cells are infiltrated in psoriatic lesions. We hypothesize that modulation of the expression of transcription factors for each Th subset could be a new therapeutic target for psoriasis. In this review, we will focus on the recent literature concerning the transcriptional regulation of Th cells in psoriasis.

A bifurcated role for c-Maf in Th2 and Tfh2 cells during helminth infection

Differences in transcriptomes, transcription factor usage, and function have identified T follicular helper 2 (Tfh2) cells and T helper 2 (Th2) cells as distinct clusters of differentiation 4+",(CD4) T-cell subsets in settings of type-2 inflammation. Although the transcriptional programs driving Th2 cell differentiation and cytokine production are well defined, dependence on these classical Th2 programs by Tfh2 cells is less clear. Using cytokine reporter mice in combination with transcription factor inference analysis, the b-Zip transcription factor c-Maf and its targets were identified as an important regulon in both Th2 and Tfh2 cells. Conditional deletion of c-Maf in T cells confirmed its importance in type-2 cytokine expression by Th2 and Tfh2 cells. However, while c-Maf was not required for Th2-driven helminth clearance or lung eosinophilia, it was required for Tfh2-driven Immunoglobulin E production and germinal center formation. This differential regulation of cell-mediated and humoral immunity by c-Maf was a result of redundant pathways in Th2 cells that were absent in Tfh2 cells, and c-Maf-specific mechanisms in Tfh2 cells that were absent in Th2 cells. Thus, despite shared expression by Tfh2 and Th2 cells, c-Maf serves as a unique regulator of Tfh2-driven humoral hallmarks during type-2 immunity.

JAK/STAT Signaling and Cervical Cancer: From the Cell Surface to the Nucleus

The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway constitutes a rapid signaling module from the cell surface to the nucleus, and activates different cellular responses, such as proliferation, survival, migration, invasion, and inflammation. When the JAK/STAT pathway is altered, it contributes to cancer progression and metastasis. STAT proteins play a central role in developing cervical cancer, and inhibiting the JAK/STAT signaling may be necessary to induce tumor cell death. Several cancers show continuous activation of different STATs, including cervical cancer. The constitutive activation of STAT proteins is associated with a poor prognosis and overall survival. The human papillomavirus (HPV) oncoproteins E6 and E7 play an essential role in cervical cancer progression, and they activate the JAK/STAT pathway and other signals that induce proliferation, survival, and migration of cancer cells. Moreover, there is a crosstalk between the JAK/STAT signaling cascade with other signaling pathways, where a plethora of different proteins activate to induce gene transcription and cell responses that contribute to tumor growth. Therefore, inhibition of the JAK/STAT pathway shows promise as a new target in cancer treatment. In this review, we discuss the role of the JAK/STAT pathway components and the role of the HPV oncoproteins associated with cellular malignancy through the JAK/STAT proteins and other signaling pathways to induce tumor growth.

Human germline heterozygous gain-of-function STAT6 variants cause severe allergic disease

STAT6 (signal transducer and activator of transcription 6) is a transcription factor that plays a central role in the pathophysiology of allergic inflammation. We have identified 16 patients from 10 families spanning three continents with a profound phenotype of early-life onset allergic immune dysregulation, widespread treatment-resistant atopic dermatitis, hypereosinophilia with esosinophilic gastrointestinal disease, asthma, elevated serum IgE, IgE-mediated food allergies, and anaphylaxis. The cases were either sporadic (seven kindreds) or followed an autosomal dominant inheritance pattern (three kindreds). All patients carried monoallelic rare variants in STAT6 and functional studies established their gain-of-function (GOF) phenotype with sustained STAT6 phosphorylation, increased STAT6 target gene expression, and TH2 skewing. Precision treatment with the anti-IL-4Rα antibody, dupilumab, was highly effective improving both clinical manifestations and immunological biomarkers. This study identifies heterozygous GOF variants in STAT6 as a novel autosomal dominant allergic disorder. We anticipate that our discovery of multiple kindreds with germline STAT6 GOF variants will facilitate the recognition of more affected individuals and the full definition of this new primary atopic disorder.

Distinct Responses to IL4 in Macrophages Mediated by JNK

IL(Interleukin)-4 is the main macrophage M2-type activator and induces an anti-inflammatory phenotype called alternative activation. The IL-4 signaling pathway involves the activation of STAT (Signal Transducer and Activator of Transcription)-6 and members of the MAPK (Mitogen-activated protein kinase) family. In primary-bone-marrow-derived macrophages, we observed a strong activation of JNK (Jun N-terminal kinase)-1 at early time points of IL-4 stimulation. Using selective inhibitors and a knockout model, we explored the contribution of JNK-1 activation to macrophages' response to IL-4. Our findings indicate that JNK-1 regulates the IL-4-mediated expression of genes typically involved in alternative activation, such as Arginase 1 or Mannose receptor, but not others, such as SOCS (suppressor of cytokine signaling) 1 or p21^Waf-1 (cyclin dependent kinase inhibitor 1A). Interestingly, we have observed that after macrophages are stimulated with IL-4, JNK-1 has the capacity to phosphorylate STAT-6 on serine but not on tyrosine. Chromatin immunoprecipitation assays revealed that functional JNK-1 is required for the recruitment of co-activators such as CBP (CREB-binding protein)/p300 on the promoter of Arginase 1 but not on p21^Waf-1. Taken together, these data demonstrate the critical role of STAT-6 serine phosphorylation by JNK-1 in distinct macrophage responses to IL-4.

Class switching is differentially regulated in RBC alloimmunization and vaccination

BACKGROUND

Studies of human patients have shown that most anti-RBC alloantibodies are IgG1 or IgG3 subclasses, although it is unclear why transfused RBCs preferentially drive these subclasses over others. Though mouse models allow for the mechanistic exploration of class-switching, previous studies of RBC alloimmunization in mice have focused more on the total IgG response than the relative distribution, abundance, or mechanism of IgG subclass generation. Given this major gap, we compared the IgG subclass distribution generated in response to transfused RBCs relative to protein in alum vaccination, and determined the role of STAT6 in their generation.

STUDY DESIGN AND METHODS

WT mice were either immunized with Alum/HEL-OVA or transfused with HOD RBCs and levels of anti-HEL IgG subtypes were measured using end-point dilution ELISAs. To study the role of STAT6 in IgG class-switching, we first generated and validated novel STAT6 KO mice using CRISPR/cas9 gene editing. STAT6 KO mice were then transfused with HOD RBCs or immunized with Alum/HEL-OVA, and IgG subclasses were quantified by ELISA.

RESULTS

When compared with antibody responses to Alum/HEL-OVA, transfusion of HOD RBCs induced lower levels of IgG1, IgG2b, and IgG2c but similar levels of IgG3. Class switching to most IgG subtypes remained largely unaffected in STAT6 deficient mice in response to HOD RBC transfusion, with the one exception being IgG2b. In contrast, STAT6 deficient mice showed altered levels of all IgG subtypes following Alum vaccination.

DISCUSSION

Our results show that anti-RBC class-switching occurs via alternate mechanisms when compared with the well-studied immunogen alum vaccination.

Evidence that High-Affinity IgE Can Develop in the Germinal Center in the Absence of an IgG1-Switched Intermediate

High-affinity allergen-specific IgE is essential for the severe allergic anaphylaxis response. High-affinity Abs are formed by successive rounds of selection of Ag-specific B cells in the germinal center (GC); however, several studies have shown that IgE+ GC B cells are impaired in their ability to undergo selection in the GC. A pathway, known as the "indirect switching pathway" for IgE, has been described whereby Ag-specific B cells initially switch to the IgG1 isotype and undergo affinity selection in the GC, with a secondary switch to the IgE isotype after affinity selection. In previous work, using a food allergy model in mice, we investigated how high-affinity IgE develops in the GC, but we did not test the indirect switching model. In this study, we analyzed the importance of the indirect switching pathway by constructing IgG1-cre Bcl6-fl/fl mice. In these mice, once B cells switch to IgG1, they delete Bcl6 and thus cannot enter or persist in the GC. When we tested IgG1-cre Bcl6-fl/fl mice with our food allergy model, we found that, as expected, IgG1 Abs had decreased affinity, but unexpectedly, the affinity of IgE for allergen was unchanged. IgG1-cre Bcl6-fl/fl mice underwent anaphylaxis in response to allergen, consistent with the formation of high-affinity IgE. Thus, in a food allergy response, high-affinity IgE can be efficiently formed in the absence of indirect switching to IgG1, either by direct selection of IgE+ GC B cells or indirect selection of IgM+ GC B cells that later switch to IgE.

Therapeutic modulation of JAK-STAT, mTOR, and PPAR-γ signaling in neurological dysfunctions

The cytokine-activated Janus kinase (JAK)-signal transducer and activator of transcription (STAT) cascade is a pleiotropic pathway that involves receptor subunit multimerization. The mammalian target of rapamycin (mTOR) is a ubiquitously expressed serine-threonine kinase that perceives and integrates a variety of intracellular and environmental stimuli to regulate essential activities such as cell development and metabolism. Peroxisome proliferator-activated receptor-gamma (PPARγ) is a prototypical metabolic nuclear receptor involved in neural differentiation and axon polarity. The JAK-STAT, mTOR, and PPARγ signaling pathways serve as a highly conserved signaling hub that coordinates neuronal activity and brain development. Additionally, overactivation of JAK/STAT, mTOR, and inhibition of PPARγ signaling have been linked to various neurocomplications, including neuroinflammation, apoptosis, and oxidative stress. Emerging research suggests that even minor disruptions in these cellular and molecular processes can have significant consequences manifested as neurological and neuropsychiatric diseases. Of interest, target modulators have been proven to alleviate neuronal complications associated with acute and chronic neurological deficits. This research-based review explores the therapeutic role of JAK-STAT, mTOR, and PPARγ signaling modulators in preventing neuronal dysfunctions in preclinical and clinical investigations.

Class switching is differentially regulated in RBC alloimmunization and vaccination

Background

Studies of human patients have shown that most anti-RBC alloantibodies are IgG1 or IgG3 subclasses, though it is unclear why transfused RBCs preferentially drive these subclasses over others. Though mouse models allow for the mechanistic exploration of class-switching, previous studies of RBC alloimmunization in mice have focused more on the total IgG response than the relative distribution, abundance, or mechanism of IgG subclass generation. Given this major gap, we compared the IgG subclass distribution generated in response to transfused RBCs relative to protein in alum vaccination, and determined the role of STAT6 in their generation.

Study Design and Methods

WT mice were either immunized with Alum/HEL-OVA or transfused with HOD RBCs and levels of anti-HEL IgG subtypes were measured using end-point dilution ELISAs. To study the role of STAT6 in IgG class-switching, we first generated and validated novel STAT6 KO mice using CRISPR/cas9 gene editing. STAT6 KO mice were then transfused with HOD RBCs or immunized with Alum/HEL-OVA, and IgG subclasses were quantified by ELISA.

Results

When compared to antibody responses to Alum/HEL-OVA, transfusion of HOD RBCs induced lower levels of IgG1, IgG2b and IgG2c but similar levels of IgG3. Class switching to most IgG subtypes remained largely unaffected in STAT6 deficient mice in response to HOD RBC transfusion, with the one exception being IgG2b. In contrast, STAT6 deficient mice showed altered levels of all IgG subtypes following Alum vaccination.

Discussion

Our results show that anti-RBC class-switching occurs via alternate mechanisms when compared to the well-studied immunogen alum vaccination.

Bacillus subtilis Provides Long-Term Protection in a Murine Model of Allergic Lung Disease by Influencing Bacterial Composition

Probiotics are an attractive target for reducing the incidence of allergic disease. Bacillus subtilis is a gut-associated probiotic bacteria that can suppress allergic lung disease; however, it is not clear for how long this protection lasts. We exposed C57Bl/6 mice to B. subtilis via oral gavage and challenged them with intranasal house-dust mite for up to 8 weeks. We found that B. subtilis treatment was able to provide protection from eosinophil infiltration of the airways for 3 weeks. This loss of protection correlated with an increase in the eosinophil chemoattractant CCL24. Additionally, we demonstrate that B. subtilis treatment altered the bacterial composition by increasing the phylum Bacteroidetes and Verrucomicorbiota. The phylum Verrucomicorbiota was reduced in B. subtilis-treated mice at 8 weeks when protection was lost. These results support B. subtilis as a prophylactic for preventing the production of allergic lung disease and highlights that protection can last up to 3 weeks. This work also expands our understanding of how B. subtilis mediates protection and that in addition to modifying the immune system it is also altering the host microbiota.

Increased circulating T follicular helper 13 subset correlates with high IgE levels in pediatric allergic asthma

We found an elevation of circulating TFH13 cell subset in asthmatic children and the frequency of TFH13 cells positively correlated with the plasma dust mite-specific IgE levels. These results indicated that TFH13 cell subset may be responsible for the immunopathogenesis of excessive IgE accumulation in children with allergic asthma.

Immunology of allergen immunotherapy

Allergen immunotherapy (AIT) is the only disease-modifying therapy for allergic disease. Through repeated inoculations of low doses of allergen-either as whole proteins or peptides-patients can achieve a homeostatic balance between inflammatory effectors induced and/or associated with allergen contact, and mediators of immunologic non-responsiveness, potentially leading to sustained clinical improvements. AIT for airborne/respiratory tract allergens and insect venoms have traditionally been supplied subcutaneously, but other routes and modalities of administration can also be effective. Despite differences of allergen administration, there are some similarities of immunologic responses across platforms, with a general theme involving the restructuring and polarization of adaptive and innate immune effector cells. Here we review the immunology of AIT across various delivery platforms, including subcutaneous, sublingual, epicutaneous, intradermal, and intralymphatic approaches, emphasizing shared mechanisms associated with achieving immunologic non-responsiveness to allergen.

Transgenic overexpression of α7 integrin in smooth muscle attenuates allergen-induced airway inflammation in a murine model of asthma

Asthma is a chronic inflammatory disorder of the lower airways characterized by modulation of airway smooth muscle (ASM) function. Infiltration of smooth muscle by inflammatory mediators is partially regulated by transmembrane integrins and the major smooth muscle laminin receptor α7β1 integrin plays a critical role in the maintenance of ASM phenotype. The goal of the current study was to investigate the role of α7 integrin in asthma using smooth muscle-specific α7 integrin transgenic mice (TgSM-Itgα7) using both acute and chronic OVA sensitization and challenge protocols that mimic mild to severe asthmatic phenotypes. Transgenic over-expression of the α7 integrin in smooth muscle resulted in a significant decrease in airway resistance relative to controls, reduced the total number of inflammatory cells and substantially inhibited the production of crucial Th2 and Th17 cytokines in airways. This was accompanied by decreased secretion of various inflammatory chemokines such as eotaxin/CCL11, KC/CXCL3, MCP-1/CCL2, and MIP-1β/CCL4. Additionally, α7 integrin overexpression significantly decreased ERK1/2 phosphorylation in the lungs of TgSM-Itgα7 mice and affected proliferative, contractile, and inflammatory downstream effectors of ERK1/2 that drive smooth muscle phenotype in the lung. Taken together, these results support the hypothesis that enhanced expression of α7 integrin in vivo inhibits allergic inflammation and airway resistance. Moreover, we identify ERK1/2 as a potential target by which α7 integrin signals to regulate airway inflammation. We conclude that identification of therapeutics targeting an increase in smooth muscle α7 integrin expression could serve as a potential novel treatment for asthma.

A Narrative Review of STAT Proteins in Diabetic Retinopathy: From Mechanisms to Therapeutic Prospects

Diabetic retinopathy (DR), a blinding disease, is one of the high-incidence chronic complications of diabetes. However, the current treatment for DR is mainly based on advanced pathological changes, which cannot reverse pre-existing retinal tissue damage and visual impairment. Signal transducer and activator of transcription (STAT) proteins are essential in DR through early and late stages. They participate in the early stage of DR through multiple mechanisms and have a strong proangiogenic effect in the late stage. Inhibiting STAT proteins activity has also achieved a significant effect in reversing the pathological changes of DR. Thus, STAT proteins are expected to be an effective therapeutic target in the early stage of DR and can make up for inadequate late treatment. This review introduces the structure, signal transduction mode, and biological functions of STAT proteins in detail and focuses on their role in the mechanism of DR. We also summarize the current research on STAT-related biological agents in DR, aiming to provide a theoretical basis for the treatment of DR.

Emerging Roles of T Helper Cells in Non-Infectious Neuroinflammation: Savior or Sinner

CD4⁺ T cells, also known as T helper (Th) cells, contribute to the adaptive immunity both in the periphery and in the central nervous system (CNS). At least seven subsets of Th cells along with their signature cytokines have been identified nowadays. Neuroinflammation denotes the brain’s immune response to inflammatory conditions. In recent years, various CNS disorders have been related to the dysregulation of adaptive immunity, especially the process concerning Th cells and their cytokines. However, as the functions of Th cells are being discovered, it’s also found that their roles in different neuroinflammatory conditions, or even the participation of a specific Th subset in one CNS disorder may differ, and sometimes contrast. Based on those recent and contradictory evidence, the conflicting roles of Th cells in multiple sclerosis, Alzheimer’s disease, Parkinson’s disease, epilepsy, traumatic brain injury as well as some typical mental disorders will be reviewed herein. Research progress, limitations and novel approaches concerning different neuroinflammatory conditions will also be mentioned and compared.

Development of allergen-specific IgE in a food-allergy model requires precisely timed B cell stimulation and is inhibited by Fgl2

Immunoglobulin E (IgE) responses are a central feature of allergic disease. Using a well-established food-allergy model in mice, we show that two sensitizations with cognate B cell antigen (Ag) and adjuvant 7 days apart promotes optimal development of IgE+ germinal center (GC) B cells and high-affinity IgE production. Intervals of 3 or 14 days between Ag sensitizations lead to loss of IgE+ GC B cells and an undetectable IgE response. The immunosuppressive factors Fgl2 and CD39 are down-regulated in T follicular helper (TFH) cells under optimal IgE-sensitization conditions. Deletion of Fgl2 in TFH and T follicular regulatory (TFR) cells, but not from TFR cells alone, increase Ag-specific IgE levels and IgE-mediated anaphylactic responses. Overall, we find that Ag-specific IgE responses require precisely timed stimulation of IgE+ GC B cells by Ag. Furthermore, we show that Fgl2 is expressed by TFH cells and represses IgE. This work has implications for the development and treatment of food allergies.

Using a mouse food-allergy model, Chen et al. find that allergen-specific IgE responses require precisely timed stimulation of IgE+ germinal center B cells. The authors further show that Fgl2 expressed by T follicular helper cells represses IgE. This work has implications for the development and treatment of food allergy.

Decoding lymphomyeloid divergence and immune hyporesponsiveness in G-CSF-primed human bone marrow by single-cell RNA-seq

Granulocyte colony-stimulating factor (G-CSF) has been widely used to mobilize bone marrow hematopoietic stem/progenitor cells for transplantation in the treatment of hematological malignancies for decades. Additionally, G-CSF is also accepted as an essential mediator in immune regulation, leading to reduced graft-versus-host disease following transplantation. Despite the important clinical roles of G-CSF, a comprehensive, unbiased, and high-resolution survey into the cellular and molecular ecosystem of the human G-CSF-primed bone marrow (G-BM) is lacking so far. Here, we employed single-cell RNA sequencing to profile hematopoietic cells in human bone marrow from two healthy donors before and after 5-day G-CSF administration. Through unbiased bioinformatics analysis, our data systematically showed the alterations in the transcriptional landscape of hematopoietic cells in G-BM, and revealed that G-CSF-induced myeloid-biased differentiation initiated from the stage of lymphoid-primed multipotent progenitors. We also illustrated the cellular and molecular basis of hyporesponsiveness of T cells and natural killer (NK) cells caused by G-CSF stimulation, including the potential direct mechanisms and indirect regulations mediated by ligand–receptor interactions. Taken together, our data extend the understanding of lymphomyeloid divergence and potential mechanisms involved in hyporesponsiveness of T and NK cells in human G-BM, which might provide basis for optimization of stem cell transplantation in hematological malignancy treatment.

Natural Flavonoids Derived From Fruits Are Potential Agents Against Atherosclerosis

Atherosclerosis, as a chronic inflammatory response, is one of the main causes of cardiovascular diseases. Atherosclerosis is induced by endothelial cell dysfunction, migration and proliferation of smooth muscle cells, accumulation of foam cells and inflammatory response, resulting in plaque accumulation, narrowing and hardening of the artery wall, and ultimately leading to myocardial infarction or sudden death and other serious consequences. Flavonoid is a kind of natural polyphenol compound widely existing in fruits with various structures, mainly including flavonols, flavones, flavanones, flavanols, anthocyanins, isoflavones, and chalcone, etc. Because of its potential health benefits, it is now used in supplements, cosmetics and medicines, and researchers are increasingly paying attention to its role in atherosclerosis. In this paper, we will focus on several important nodes in the development of atherosclerotic disease, including endothelial cell dysfunction, smooth muscle cell migration and proliferation, foam cell accumulation and inflammatory response. At the same time, through the classification of flavonoids from fruits, the role and potential mechanism of flavonoids in atherosclerosis were reviewed, providing a certain direction for the development of fruit flavonoids in the treatment of atherosclerosis drugs.

Siglec-F Promotes IL-33-Induced Cytokine Release from Bone Marrow-Derived Eosinophils Independently of the ITIM and ITIM-like Motif Phosphorylation

Eosinophils are potent innate effector cells associated mainly with type 2 immune responses elicited by helminths and allergens. Their activity needs to be tightly controlled to prevent severe inflammation and tissue damage. Eosinophil degranulation and secretion of inflammatory effector molecules, including cytokines, chemokines, and lipid mediators, can be regulated by activating and inhibitory receptors on the cell surface. In this study, we investigated the modulation of proliferation, apoptosis, gene expression, and cytokine/chemokine secretion from IL-33-activated Mus musculus eosinophils on cross-linking of the transmembrane receptor Sialic acid-binding Ig-like lectin F (Siglec-F). Siglec-F contains an ITIM plus an ITIM-like motif in its intracellular tail and is mainly regarded as an inhibitory and apoptosis-inducing receptor. In vitro costimulation of bone marrow-derived eosinophils with anti-Siglec-F and IL-33 compared with treatment with either alone led to enhanced STAT6 phosphorylation, stronger induction of hypoxia/glycolysis-related proinflammatory genes, and elevated secretion of type 2 cytokines (IL-4, IL-13) and chemokines (CCL3, CCL4) with only minor effects on proliferation and apoptosis. Using a competitive mixed bone marrow chimera approach with wild-type and Siglec-F-deficient eosinophils, we observed no evidence for Siglec-F-regulated inhibition of Aspergillus fumigatus-elicited lung eosinophilia. Truncation of the Siglec-F cytoplasmic tail, but not mutation of the ITIM and ITIM-like motifs, ablated the effect of enhanced cytokine/chemokine secretion. This provides evidence for an ITIM phosphorylation-independent signaling pathway from the cytoplasmic tail of the Siglec-F receptor that enhances effector molecule release from activated eosinophils.

Inhalant Mammal-Derived Lipocalin Allergens and the Innate Immunity

A major part of important mammalian respiratory allergens belongs to the lipocalin family of proteins. By this time, 19 respiratory mammalian lipocalin allergens have been registered in the WHO/IUIS Allergen Nomenclature Database. Originally, lipocalins, small extracellular proteins (molecular mass ca. 20 kDa), were characterized as transport proteins but they are currently known to exert a variety of biological functions. The three-dimensional structure of lipocalins is well-preserved, and lipocalin allergens can exhibit high amino acid identities, in several cases more than 50%. Lipocalins contain an internal ligand-binding site where they can harbor small principally hydrophobic molecules. Another characteristic feature is their capacity to bind to specific cell-surface receptors. In all, the physicochemical properties of lipocalin allergens do not offer any straightforward explanations for their allergenicity. Allergic sensitization begins at epithelial barriers where diverse insults through pattern recognition receptors awaken innate immunity. This front-line response is manifested by epithelial barrier-associated cytokines which together with other components of immunity can initiate the sensitization process. In the following, the crucial factor in allergic sensitization is interleukin (IL)-4 which is needed for stabilizing and promoting the type 2 immune response. The source for IL-4 has been searched widely. Candidates for it may be non-professional antigen-presenting cells, such as basophils or mast cells, as well as CD4+ T cells. The synthesis of IL-4 by CD4+ T cells requires T cell receptor engagement, i.e., the recognition of allergen peptides, which also provides the specificity for sensitization. Lipocalin and innate immunity-associated cell-surface receptors are implicated in facilitating the access of lipocalin allergens into the immune system. However, the significance of this for allergic sensitization is unclear, as the recognition by these receptors has been found to produce conflicting results. As to potential adjuvants associated with mammalian lipocalin allergens, the hydrophobic ligands transported by lipocalins have not been reported to enhance sensitization while it is justified to suppose that lipopolysaccharide plays a role in it. Taken together, type 2 immunity to lipocalin allergens appears to be a harmful immune response resulting from a combination of signals involving both the innate and adaptive immunities.

T Helper Cell Lineage-Defining Transcription Factors: Potent Targets for Specific GVHD Therapy?

Allogenic hematopoietic stem cell transplantation (allo-HSCT) represents a potent and potentially curative treatment for many hematopoietic malignancies and hematologic disorders in adults and children. The donor-derived immunity, elicited by the stem cell transplant, can prevent disease relapse but is also responsible for the induction of graft-versus-host disease (GVHD). The pathophysiology of acute GVHD is not completely understood yet. In general, acute GVHD is driven by the inflammatory and cytotoxic effect of alloreactive donor T cells. Since several experimental approaches indicate that CD4 T cells play an important role in initiation and progression of acute GVHD, the contribution of the different CD4 T helper (Th) cell subtypes in the pathomechanism and regulation of the disease is a central point of current research. Th lineages derive from naïve CD4 T cell progenitors and lineage commitment is initiated by the surrounding cytokine milieu and subsequent changes in the transcription factor (TF) profile. Each T cell subtype has its own effector characteristics, immunologic function, and lineage specific cytokine profile, leading to the association with different immune responses and diseases. Acute GVHD is thought to be mainly driven by the Th1/Th17 axis, whereas Treg cells are attributed to attenuate GVHD effects. As the differentiation of each Th subset highly depends on the specific composition of activating and repressing TFs, these present a potent target to alter the Th cell landscape towards a GVHD-ameliorating direction, e.g. by inhibiting Th1 and Th17 differentiation. The finding, that targeting of Th1 and Th17 differentiation appears more effective for GVHD-prevention than a strategy to inhibit Th1 and Th17 cytokines supports this concept. In this review, we shed light on the current advances of potent TF inhibitors to alter Th cell differentiation and consecutively attenuate GVHD. We will focus especially on preclinical studies and outcomes of TF inhibition in murine GVHD models. Finally, we will point out the possible impact of a Th cell subset-specific immune modulation in context of GVHD.

The JAK/STAT signaling pathway: from bench to clinic

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway was discovered more than a quarter-century ago. As a fulcrum of many vital cellular processes, the JAK/STAT pathway constitutes a rapid membrane-to-nucleus signaling module and induces the expression of various critical mediators of cancer and inflammation. Growing evidence suggests that dysregulation of the JAK/STAT pathway is associated with various cancers and autoimmune diseases. In this review, we discuss the current knowledge about the composition, activation, and regulation of the JAK/STAT pathway. Moreover, we highlight the role of the JAK/STAT pathway and its inhibitors in various diseases.