T cell homing to epithelial barriers in allergic disease

Costimulatory Molecule CD226 Regulates Atopic Dermatitis in a Mouse Model

This study investigated the role of CD226 in a 2,4-dinitrochlorobenzene (DNCB)-induced mouse model of atopic dermatitis. The results showed that the lack of CD226 (global and CD4+ T-cell specific) significantly increased ear thickness, reddening, swelling, and scaling of the skin as well as inflammatory cell and mast cell infiltration. RT-qPCR results demonstrated that the mRNA expressions of atopic dermatitis-related inflammatory cytokines and chemokines were markedly increased in the draining lymph nodes and lesioned ear skin tissues of global and CD4+ T-cell-specific CD226-deficient mice compared with that in control mice. In vitro assessment revealed that CD226 directly modulates TGFβ-mediated regulatory T (Treg) cell differentiation and proliferation. Notably, Treg cell-specific deletion of CD226 (Cd226fl/flFoxp3cre mice) resulted in more severe dermatitis and epidermal thickening than those observed in littermate mice upon DNCB treatment. Subsequent analysis showed that the infiltration of Treg cells in ear lesions and the number of Tregs in the spleen were significantly reduced in Cd226fl/flFoxp3cre mice after DNCB treatment. In addition, the lack of CD226 induced apoptosis of Treg cells through the activation of caspase 3. Therefore, these results suggest that CD226 has potential efficacy in atopic dermatitis, correlating with Treg cell inhibition.

High-dimensional mass cytometry reveals systemic and local immune signatures in necrotizing enterocolitis

Objective

Patients with necrotizing enterocolitis display severe gastrointestinal complications of prematurity, but the mechanism driving this clinical profile remains unknown. We used mass cytometry time-of-flight to characterize and compare immune cell populations in the blood and intestine tissue from patients with and without (controls) necrotizing enterocolitis at single-cell resolution.

Methods

We completed a deep mapping of the immune system of the peripheral blood mononuclear cells and intestinal mucosa tissue using mass cytometry to evaluate immune cell types, which revealed global immune dysregulation characteristics underlying necrotizing enterocolitis.

Results

Compared with controls, natural killer cells display signs of heightened activation and increased cytotoxic potential in the peripheral blood and mucosa of patients with necrotizing enterocolitis. Furthermore, CD4+ T effector memory cells, non-classical monocytes, active dendritic cells, and neutrophils were specifically enriched in the mucosa, suggesting trafficking from the periphery to areas of inflammation. Moreover, we mapped the systemic and local distinct immune signatures suggesting patterns of cell localization in necrotizing enterocolitis.

Conclusion

We used mass cytometry time-of-flight technology to identify immune cell populations specific to the peripheral blood and intestinal mucosa tissue from patients with necrotizing enterocolitis and controls. This information might be used to develop precise diagnosis and therapies that target specific cell populations in patients with necrotizing enterocolitis.

Mechanistic Insights into Eosinophilic Esophagitis: Therapies Targeting Pathophysiological Mechanisms

Eosinophilic esophagitis (EoE) is a chronic inflammatory disease characterized by eosinophilic infiltration of the esophagus. It arises from a complex interplay of genetic predisposition (susceptibility loci), environmental triggers (allergens and dietary antigens), and a dysregulated immune response, mainly mediated by type 2 T helper cell (Th2)-released cytokines, such as interleukin (IL)-4, IL-5, and IL-13. These cytokines control eosinophil recruitment and activation as well as tissue remodeling, contributing to the characteristic features of EoE. The pathogenesis of EoE includes epithelial barrier dysfunction, mast cell activation, eosinophil degranulation, and fibrosis. Epithelial barrier dysfunction allows allergen penetration and promotes immune cell infiltration, thereby perpetuating the inflammatory response. Mast cells release proinflammatory mediators and promote eosinophil recruitment and the release of cytotoxic proteins and cytokines, causing tissue damage and remodeling. Prolonged inflammation can lead to fibrosis, resulting in long-term complications such as strictures and dysmotility. Current treatment options for EoE are limited and mainly focus on dietary changes, proton-pump inhibitors, and topical corticosteroids. Novel therapies targeting key inflammatory pathways, such as monoclonal antibodies against IL-4, IL-5, and IL-13, are emerging in clinical trials. A deeper understanding of the complex pathogenetic mechanisms behind EoE will contribute to the development of more effective and personalized therapeutic strategies.

Septins Enable T Cell Contact Guidance via Amoeboid-Mesenchymal Switch

Lymphocytes exit circulation and enter in-tissue guided migration toward sites of tissue pathologies, damage, infection, or inflammation. By continuously sensing and adapting to the guiding chemo-mechano-structural properties of the tissues, lymphocytes dynamically alternate and combine their amoeboid (non-adhesive) and mesenchymal (adhesive) migration modes. However, which mechanisms guide and balance different migration modes are largely unclear. Here we report that suppression of septins GTPase activity induces an abrupt amoeboid-to-mesenchymal transition of T cell migration mode, characterized by a distinct, highly deformable integrin-dependent immune cell contact guidance. Surprisingly, the T cell actomyosin cortex contractility becomes diminished, dispensable and antagonistic to mesenchymal-like migration mode. Instead, mesenchymal-like T cells rely on microtubule stabilization and their non-canonical dynein motor activity for high fidelity contact guidance. Our results establish septin's GTPase activity as an important on/off switch for integrin-dependent migration of T lymphocytes, enabling their dynein-driven fluid-like mesenchymal propulsion along the complex adhesion cues.

Analytical Performance of a Novel Latex Turbidimetric Immunoassay, "Nanopia TARC", for TARC/CCL17 Measurement: A Retrospective Observational Study

Thymus- and activation-regulated chemokine (TARC, also known as CCL17) is used as a biomarker for atopic dermatitis. The methods currently used for its measurement are complex, time-consuming, and require large machinery, warranting the need for a method that is simple, has a quick turnaround time, and requires less complex machinery. We evaluated the analytical performance of a novel latex turbidimetric immunoassay method, "Nanopia TARC", on 174 residual serum samples from patients with skin or allergic diseases. This evaluation included the assessment of the limit of blank/detection/quantification (LOB/D/Q), precision, accuracy, linearity, interference, and commutability between Nanopia TARC and "HISCL TARC", based on the chemiluminescent enzyme immunoassay (CLEIA) method. The LOB/D/Q values were 13, 57, and 141 pg/mL, respectively. The coefficient of variation of the repeatability was 0.9-3.8%, and that of the intermediate precision was 2.1-5.4%. The total error of the accuracy was 1.9-13.4%. The linearity was 141 and 19,804 pg/mL for TARC. The correlation coefficient between Nanopia TARC and HISCL TARC determined using the Passing-Bablok regression analysis was 0.999. Furthermore, the concordance of diagnostic criteria with AD was 92%. Nanopia TARC was confirmed to have the same analytical performance for TARC measurement as the existing CLEIA method.

Enforced gut homing of murine regulatory T cells reduces early graft-versus-host disease severity

Damage to the gastrointestinal tract following allogeneic hematopoietic stem cell transplantation is a significant contributor to the severity and perpetuation of graft-versus-host disease. In preclinical models and clinical trials, we showed that infusing high numbers of regulatory T cells reduces graft-versus-host disease incidence. Despite no change in in vitro suppressive function, transfer of ex vivo expanded regulatory T cells transduced to overexpress G protein-coupled receptor 15 or C-C motif chemokine receptor 9, specific homing receptors for colon or small intestine, respectively, lessened graft-versus-host disease severity in mice. Increased regulatory T cell frequency and retention within the gastrointestinal tissues of mice that received gut homing T cells correlated with lower inflammation and gut damage early post-transplant, decreased graft-versus-host disease severity, and prolonged survival compared with those receiving control transduced regulatory T cells. These data provide evidence that enforced targeting of ex vivo expanded regulatory T cells to the gastrointestinal tract diminishes gut injury and is associated with decreased graft-versus-host disease severity.

miRNAs' Cross-Involvement in Skin Allergies: A New Horizon for the Pathogenesis, Diagnosis and Therapy of Atopic Dermatitis, Allergic Contact Dermatitis and Chronic Spontaneous Urticaria

Skin inflammation is a common underlying feature of atopic dermatitis, allergic contact dermatitis and chronic spontaneous urticaria. The pathogenetic mechanisms have not been fully elucidated. The purpose of this study was to examine whether miRNA, by regulating inflammatory mechanisms through the modulation of innate and adaptive immune responses, could play a major role in the pathogenesis of these skin conditions. We conducted a narrative review using the Pubmed and Embase scientific databases and search engines to find the most relevant miRNAs related to the pathophysiology, severity and prognosis of skin conditions. The studies show that miRNAs are involved in the pathogenesis and regulation of atopic dermatitis and can reveal an atopic predisposition or indicate disease severity. In chronic spontaneous urticaria, different miRNAs which are over-expressed during urticaria exacerbations not only play a role in the possible response to therapy or remission, but also serve as a marker of chronic autoimmune urticaria and indicate associations with other autoimmune diseases. In allergic contact dermatitis, miRNAs are upregulated in inflammatory lesions and expressed during the sensitization phase of allergic response. Several miRNAs have been identified as potential biomarkers of these chronic skin conditions, but they are also possible therapeutic targets.

Staphylococcus Infection: Relapsing Atopic Dermatitis and Microbial Restoration

Atopic Dermatitis (AD) skin is susceptible to Staphylococcus aureus (SA) infection, potentially exposing it to a plethora of toxins and virulent determinants, including Panton-Valentine leukocidin (PVL) (α-hemolysin (Hla) and phenol-soluble modulins (PSMs)), and superantigens. Depending on the degree of infection (superficial or invasive), clinical treatments may encompass permanganate (aq) and bleach solutions coupled with intravenous/oral antibiotics such as amoxicillin, vancomycin, doxycycline, clindamycin, daptomycin, telavancin, linezolid, or tigecycline. However, when the skin is significantly traumatized (sheathing of epidermal sections), an SA infection can rapidly ensue, impairing the immune system, and inducing local and systemic AD presentations in susceptible areas. Furthermore, when AD presents systemically, desensitization can be long (years) and intertwined with periods of relapse. In such circumstances, the identification of triggers (stress or infection) and severity of the flare need careful monitoring (preferably in real-time) so that tailored treatments targeting the underlying pathological mechanisms (SA toxins, elevated immunoglobulins, impaired healing) can be modified, permitting rapid resolution of symptoms.

Dose and route of administration determine the efficacy of prophylactic immunotherapy for peanut allergy in a Brown Norway rat model

Introduction

Allergen-specific immunotherapy (IT) is emerging as a viable option for treatment of peanut allergy. Yet, prophylactic IT remains unexplored despite early introduction of peanut in infancy was shown to prevent allergy. There is a need to understand how allergens interact with the immune system depending on the route of administration, and how different dosages of allergen may protect from sensitisation and a clinical active allergy. Here we compared peanut allergen delivery via the oral, sublingual (SL), intragastric (IG) and subcutaneous (SC) routes for the prevention of peanut allergy in Brown Norway (BN) rats.

Methods

BN rats were administered PBS or three different doses of peanut protein extract (PPE) via either oral IT (OIT), SLIT, IGIT or SCIT followed by intraperitoneal (IP) injections of PPE to assess the protection from peanut sensitisation. The development of IgE and IgG1 responses to PPE and the major peanut allergens were evaluated by ELISAs. The clinical response to PPE was assessed by an ear swelling test (EST) and proliferation was assessed by stimulating splenocytes with PPE.

Results

Low and medium dose OIT (1 and 10 mg) and all doses of SCIT (1, 10, 100 µg) induced sensitisation to PPE, whereas high dose OIT (100 mg), SLIT (10, 100 or 1000 µg) or IGIT (1, 10 and 100 mg) did not. High dose OIT and SLIT as well as high and medium dose IGIT prevented sensitisation from the following IP injections of PPE and suppressed PPE-specific IgE levels in a dose-dependent manner. Hence, administration of peanut protein via different routes confers different risks for sensitisation and protection from peanut allergy development. Overall, the IgE levels toward the individual major peanut allergens followed the PPE-specific IgE levels.

Discussion

Collectively, this study showed that the preventive effect of allergen-specific IT is determined by the interplay between the specific site of PPE delivery for presentation to the immune system, and the allergen quantity, and that targeting and modulating tolerance mechanisms at specific mucosal sites may be a prophylactic strategy for prevention of peanut allergy.

Emerging translational strategies and challenges for enhancing regulatory T cell therapy for graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapy for many types of cancer. Genetic disparities between donor and host can result in immune-mediated attack of host tissues, known as graft versus host disease (GVHD), a major cause of morbidity and mortality following HSCT. Regulatory CD4+ T cells (Tregs) are a rare cell type crucial for immune system homeostasis, limiting the activation and differentiation of effector T cells (Teff) that are self-reactive or stimulated by foreign antigen exposure. Adoptive cell therapy (ACT) with Treg has demonstrated, first in murine models and now in patients, that prophylactic Treg infusion can also suppress GVHD. While clinical trials have demonstrated Treg reduce severe GVHD occurrence, several impediments remain, including Treg variability and practical need for individualized Treg production for each patient. Additionally, there are challenges in the use of in vitro expansion techniques and in achieving in vivo Treg persistence in context of both immune suppressive drugs and in lymphoreplete patients being treated for GVHD. This review will focus on 3 main translational approaches taken to improve the efficacy of tTreg ACT in GVHD prophylaxis and development of treatment options, following HSCT: genetic modification, manipulating TCR and cytokine signaling, and Treg production protocols. In vitro expansion for Treg ACT presents a multitude of approaches for gene modification to improve efficacy, including: antigen specificity, tissue targeting, deletion of negative regulators/exhaustion markers, resistance to immunosuppressive drugs common in GVHD treatment. Such expansion is particularly important in patients without significant lymphopenia that can drive Treg expansion, enabling a favorable Treg:Teff ratio in vivo. Several potential therapeutics have also been identified that enhance tTreg stability or persistence/expansion following ACT that target specific pathways, including: DNA/histone methylation status, TCR/co-stimulation signaling, and IL-2/STAT5 signaling. Finally, this review will discuss improvements in Treg production related to tissue source, Treg subsets, therapeutic approaches to increase Treg suppression and stability during tTreg expansion, and potential for storing large numbers of Treg from a single production run to be used as an off-the-shelf infusion product capable of treating multiple recipients.

The Trinity of Skin: Skin Homeostasis as a Neuro-Endocrine-Immune Organ

For a long time, skin was thought to be no more than the barrier of our body. However, in the last few decades, studies into the idea of skin as an independent functional organ have gradually deepened our understanding of skin and its functions. In this review, we gathered evidence that presented skin as a "trinity" of neuro-endocrine-immune function. From a neuro perspective, skin communicates through nerves and receptors, releasing neurotrophins and neuropeptides; from an endocrine perspective, skin is able to receive and secrete most hormones and has the cutaneous equivalent of the hypothalamic-pituitary-adrenal (HPA) axis; from an immune perspective, skin is protected not only by its physical barrier, but also immune cells and molecules, which can also cause inflammation. Together as an organ, skin works bidirectionally by operating peripheral neuro-endocrine-immune function and being regulated by the central nervous system, endocrine system and immune system at the same time, maintaining homeostasis. Additionally, to further explain the "trinity" of cutaneous neuro-endocrine-immune function and how it works in disease pathophysiology, a disease model of rosacea is presented.

Cytokine-Mediated Crosstalk Between Keratinocytes and T Cells in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease characterized by barrier dysfunction, dysregulated immune response, and dysbiosis with increased Staphylococcus aureus colonization. Infiltration of various T helper cell subsets into lesional skin and subsequent cytokine release are a hallmark of AD. Release of cytokines by both T cells and keratinocytes plays a key role in skin inflammation and drives many AD features. This review aims to discuss cytokine-mediated crosstalk between T cells and keratinocytes in AD pathogenesis and the potential impact of virulence factors produced by Staphylococcus aureus on these interactions.

Multi-parametric functional imaging of cell cultures and tissues with a CMOS microelectrode array

Electrode-based impedance and electrochemical measurements can provide cell-biology information that is difficult to obtain using optical-microscopy techniques. Such electrical methods are non-invasive, label-free, and continuous, eliminating the need for fluorescence reporters and overcoming optical imaging's throughput/temporal resolution limitations. Nonetheless, electrode-based techniques have not been heavily employed because devices typically contain few electrodes per well, resulting in noisy aggregate readouts. Complementary metal-oxide-semiconductor (CMOS) microelectrode arrays (MEAs) have sometimes been used for electrophysiological measurements with thousands of electrodes per well at sub-cellular pitches, but only basic impedance mappings of cell attachment have been performed outside of electrophysiology. Here, we report on new field-based impedance mapping and electrochemical mapping/patterning techniques to expand CMOS-MEA cell-biology applications. The methods enable accurate measurement of cell attachment, growth/wound healing, cell-cell adhesion, metabolic state, and redox properties with single-cell spatial resolution (20 μm electrode pitch). These measurements allow the quantification of adhesion and metabolic differences of cells expressing oncogenes versus wild-type controls. The multi-parametric, cell-population statistics captured by the chip-scale integrated device opens up new avenues for fully electronic high-throughput live-cell assays for phenotypic screening and drug discovery applications.

Thymic stromal lymphopoietin controls hair growth

Skin tissue regeneration after injury involves the production and integration of signals by stem cells residing in hair follicles (HFSCs). Much remains unknown about how specific wound-derived factors modulate stem cell contribution to hair growth. We demonstrate that thymic stromal lymphopoietin (TSLP) is produced in response to skin injury and during the anagen phase of the hair cycle. Intradermal injection of TSLP promoted wound-induced hair growth (WIHG), whereas neutralizing TSLP receptor (TSLPR) inhibited WIHG. Using flow cytometry and fluorescent immunostaining, we found that TSLP promoted proliferation of transit-amplifying cells. Lgr5^CreER-mediated deletion of Tslpr in HFSCs inhibited both wound-induced and exogenous TSLP-induced hair growth. Our data highlight a novel function for TSLP in regulation of hair follicle activity during homeostasis and wound healing.

The skin microbiome and the gut-skin axis

The microbiome plays a significant role in human health, homeostasis, immune system, and disease pathogenesis. Disrupted communication between the microbiome and host has been extensively studied in gastrointestinal diseases. To a lesser extent, there is emerging research on the skin microbiome and its connection with the gut, referred to as the gut-skin axis and its effects on dermatologic conditions. A basic overview will be provided of the gut and skin microbiome with a focus on the impact of this connection on cutaneous diseases, such as psoriasis, atopic dermatitis, rosacea, acne vulgaris, photoaging, and cutaneous wounds. In addition, we shall discuss nutrition-based approaches mediated through the gut-skin axis and topical treatments that could serve as potential adjunctive management by manipulation of the microbiome. In particular, there is a growing body of research on oral probiotics, prebiotics, and dietary modifications that may help improve symptoms for a variety of dermatologic conditions in select demographic groups.

Chemokines and Innate Lymphoid Cells in Skin Inflammation

As the outermost barrier, skin plays an important role in protecting our bodies against outside invasion. Under stable conditions or during inflammation, leukocytes migration is essential for restoring homeostasis in the skin. Immune cells trafficking is orchestrated by chemokines; leukocytes express receptors that bind to chemokines and trigger migration. The homeostasis of the immune ecosystem is an extremely complicated dynamic process that requires the cooperation of innate and adaptive immune cells. Emerging studies have been shedding a light on the unique characteristics of skin-resident innate lymphoid cells (ILCs). In this review, we discuss how chemokines orchestrate skin ILCs trafficking and contribute to tissue homeostasis and how abnormal chemokine–chemokine receptor interactions contribute to and augment skin inflammation, as seen in conditions such as contact hypersensitivity, atopic dermatitis, and psoriasis.

CCR4 as a Therapeutic Target for Cancer Immunotherapy

Simple Summary

CCR4 is a chemokine receptor selectively expressed on normal T cell subsets such as type 2 helper T cells, skin-homing T cells and regulatory T cells, and on skin-associated T cell malignancies such as adult T cell leukemia/lymphoma (ATLL), which is etiologically associated with human T lymphocyte virus type 1 (HTLV-1), and cutaneous T cell lymphomas (CTCLs). Mogamulizumab is a fully humanized and glyco-engineered monoclonal anti-CCR4 antibody used for the treatment of refractory/relapsed ATLL and CTCLs, often resulting in complete remission. The clinical applications of Mogamulizumab are now being extended to solid tumors, exploring the therapeutic effect of regulatory T cell depletion. This review overviews the expression of CCR4 in various T cell subsets, HTLV-1-infected T cells, ATLL and CTCLs, and the clinical applications of Mogamulizumab.

Abstract

CCR4 is a chemokine receptor mainly expressed by T cells. It is the receptor for two CC chemokine ligands, CCL17 and CCL22. Originally, the expression of CCR4 was described as highly selective for helper T type 2 (Th2) cells. Later, its expression was extended to other T cell subsets such as regulatory T (Treg) cells and Th17 cells. CCR4 has long been regarded as a potential therapeutic target for allergic diseases such as atopic dermatitis and bronchial asthma. Furthermore, the findings showing that CCR4 is strongly expressed by T cell malignancies such as adult T cell leukemia/lymphoma (ATLL) and cutaneous T cell lymphomas (CTCLs) have led to the development and clinical application of the fully humanized and glyco-engineered monoclonal anti-CCR4 Mogamulizumab in refractory/relapsed ATLL and CTCLs with remarkable successes. However, Mogamulizumab often induces severe adverse events in the skin possibly because of its efficient depletion of Treg cells. In particular, treatment with Mogamulizumab prior to allogenic hematopoietic stem cell transplantation (allo-HSCT), the only curative option of these T cell malignancies, often leads to severe glucocorticoid-refractory graft-versus-host diseases. The efficient depletion of Treg cells by Mogamulizumab has also led to its clinical trials in advanced solid tumors singly or in combination with immune checkpoint inhibitors. The main focus of this review is CCR4; its expression on normal and malignant T cells and its significance as a therapeutic target in cancer immunotherapy.

The Loss of H3K27 Histone Demethylase Utx in T Cells Aggravates Allergic Contact Dermatitis

The pathogenesis of allergic contact dermatitis (ACD) requires the activation of Ag-specific T cells, including effector and regulatory T cells. The differentiation and function of these T cells is epigenetically regulated through DNA methylation and histone modifications. However, the roles of altered histone H3K27 methylation in T cells in the development of ACD remain unknown. Two types of histone H3K27 demethylases, Utx and Jmjd3, have been reported in mammals. To determine the role of the histone H3K27 demethylase expression of T cells in the development of ACD, we generated T cell-specific, Utx-deficient (Utx KO) mice or Jmjd3-deficient (Jmjd3 KO) mice. Unlike control mice, Utx KO mice had severer symptoms of ACD, whereas Jmjd3 KO mice showed symptoms identical to those in control mice. In Utx KO mice with ACD, the massive infiltration of myeloid cells, including neutrophils and dendritic cells, has been observed. In addition, the expression of proinflammatory cytokines in CD4⁺ T cells of the draining lymph nodes (LNs) and in CD8⁺ T cells of the skin was increased in Utx KO mice, whereas the ratio of Foxp3⁺ regulatory CD4⁺ T cells to Foxp3^- conventional CD4⁺ T cells was decreased in both the draining LNs and the skin of Utx KO mice with ACD. Furthermore, Foxp3⁺ regulatory CD4⁺ T cells of Utx KO mice with ACD expressed a decreased level of CCR4 (a skin-tropic chemokine receptor) in comparison with control. Thus, in CD4⁺ T cells, Utx could potentially be involved in the regulation of the pathogenesis of ACD.

An exhausted phenotype of TH 2 cells is primed by allergen exposure, but not reinforced by allergen-specific immunotherapy

BACKGROUND

Studies show that proallergic T_H 2 cells decrease after successful allergen-specific immunotherapy (AIT). It is likely that iatrogenic administration of allergens drives these cells to exhaustion due to chronic T-cell receptor stimulation. This study aimed to investigate the exhaustion of T cells in connection with allergen exposure during AIT in mice and two independent patient cohorts.

METHODS

OVA-sensitized C57BL/6J mice were challenged and treated with OVA, and the development of exhaustion in local and systemic T_H 2 cells was analyzed. In patients, the expression of exhaustion-associated surface markers on T_H 2 cells was evaluated using flow cytometry in a cross-sectional grass pollen allergy cohort with and without AIT. The treatment effect was further studied in PBMC collected from a prospective long-term AIT cohort.

RESULTS

The exhaustion-associated surface markers CTLA-4 and PD-1 were significantly upregulated on T_H 2 cells upon OVA aerosol exposure in OVA-allergic compared to non-allergic mice. CTLA-4 and PD-1 decreased after AIT, in particular on the surface of local lung T_H 2 cells. Similarly, CTLA-4 and PD-1 expression was enhanced on T_H 2 cells from patients with allergic rhinitis with an even stronger effect in those with concomitant asthma. Using an unbiased Louvain clustering analysis, we discovered a late-differentiated T_H 2 population expressing both markers that decreased during up-dosing but persisted long term during the maintenance phase.

CONCLUSIONS

This study shows that allergen exposure promotes CTLA-4 and PD-1 expression on T_H 2 cells and that the dynamic change in frequencies of exhausted T_H 2 cells exhibits a differential pattern during the up-dosing versus the maintenance phases of AIT.

Functional Contribution and Targeted Migration of Group-2 Innate Lymphoid Cells in Inflammatory Lung Diseases: Being at the Right Place at the Right Time

During the last decade, group-2 innate lymphoid cells (ILC2s) have been discovered and successfully established as crucial mediators of lung allergy, airway inflammation and fibrosis, thus affecting the pathogenesis and clinical course of many respiratory diseases, like for instance asthma, cystic fibrosis and chronic rhinosinusitis. As an important regulatory component in this context, the local pulmonary milieu at inflammatory tissue sites does not only determine the activation status of lung-infiltrating ILC2s, but also influences their motility and migratory behavior. In general, many data collected in recent murine and human studies argued against the former concept of a very strict tissue residency of innate lymphoid cells (ILCs) and instead pointed to a context-dependent homing capacity of peripheral blood ILC precursors and the inflammation-dependent capacity of specific ILC subsets for interorgan trafficking. In this review article, we provide a comprehensive overview of the so far described molecular mechanisms underlying the pulmonary migration of ILC2s and thereby the numeric regulation of local ILC2 pools at inflamed or fibrotic pulmonary tissue sites and discuss their potential to serve as innovative therapeutic targets in the treatment of inflammatory lung diseases.

Memory Generation and Re-Activation in Food Allergy

Recent evidence has highlighted the critical role of memory cells in maintaining lifelong food allergies, thereby identifying these cells as therapeutic targets. IgG+ memory B cells replenish pools of IgE-secreting cells upon allergen exposure, which contract thereafter due to the short lifespan of tightly regulated IgE-expressing cells. Advances in the detection and highly dimensional analysis of allergen-specific B and T cells from allergic patients have provided insight on their phenotype and function. The newly identified Th2A and Tfh13 populations represent a leap in our understanding of allergen-specific T cell phenotypes, although how these populations contribute to IgE memory responses remains poorly understood. Within, we discuss the mechanisms by which memory B and T cells are activated, integrating knowledge from human systems and fundamental research. We then focus on memory reactivation, specifically, on the pathways of secondary IgE responses. Throughout, we identify areas of future research which will help identify immunotargets for a transformative therapy for food allergy.

What does elevated TARC/CCL17 expression tell us about eosinophilic disorders?

Eosinophilic disorders encompass a large spectrum of heterogeneous diseases sharing the presence of elevated numbers of eosinophils in blood and/or tissues. Among these disorders, the role of eosinophils can vary widely, ranging from a modest participation in the disease process to the predominant perpetrator of tissue damage. In many cases, eosinophilic expansion is polyclonal, driven by enhanced production of interleukin-5, mainly by type 2 helper cells (Th2 cells) with a possible contribution of type 2 innate lymphoid cells (ILC2s). Among the key steps implicated in the establishment of type 2 immune responses, leukocyte recruitment toward inflamed tissues is particularly relevant. Herein, the contribution of the chemo-attractant molecule thymus and activation-regulated chemokine (TARC/CCL17) to type 2 immunity will be reviewed. The clinical relevance of this chemokine and its target, C-C chemokine receptor 4 (CCR4), will be illustrated in the setting of various eosinophilic disorders. Special emphasis will be put on the potential diagnostic, prognostic, and therapeutic implications related to activation of the TARC/CCL17-CCR4 axis.

Immunomodulatory nanosystems for treating inflammatory diseases

Inflammatory disease (ID) is an umbrella term encompassing all illnesses involving chronic inflammation as the central manifestation of pathogenesis. These include, inflammatory bowel diseases, hepatitis, pulmonary disorders, atherosclerosis, myocardial infarction, pancreatitis, arthritis, periodontitis, psoriasis. The IDs create a severe burden on healthcare and significantly impact the global socio-economic balance. Unfortunately, the standard therapies that rely on a combination of anti-inflammatory and immunosuppressive agents are palliative and provide only short-term relief. In contrast, the emerging concept of immunomodulatory nanosystems (IMNs) has the potential to address the underlying causes and prevent reoccurrence, thereby, creating new opportunities for treating IDs. The IMNs offer exquisite ability to precisely modulate the immune system for a therapeutic advantage. The nano-sized dimension of IMNs allows them to efficiently infiltrate lymphatic drainage, interact with immune cells, and subsequently to undergo rapid endocytosis by hyperactive immune cells (HICs) at inflamed sites. Thus, IMNs serve to restore dysfunctional or HICs and alleviate the inflammation. We identified that different IMNs exert their immunomodulatory action via either of the seven mechanisms to modulate; cytokine production, cytokine neutralization, cellular infiltration, macrophage polarization, HICs growth inhibition, stimulating T-reg mediated tolerance and modulating oxidative-stress. In this article, we discussed representative examples of IMNs by highlighting their rationalization, design principle, and mechanism of action in context of treating various IDs. Lastly, we highlighted technical challenges in the application of IMNs and explored the future direction of research, which could potentially help to overcome those challenges.

Innate and Adaptive Immunity: ILC2 and Th2 Cells in Upper and Lower Airway Allergic Diseases

Advances in our understanding of the immune system, with the recent discovery of a parallel set of innate T lymphocytes, the innate lymphocytes (ILCs), have led to a reassessment of the pathogenesis of allergic and eosinophilic airway disorders, including allergic rhinitis (AR), asthma, and chronic rhinosinusitis with nasal polyps. We review current understanding of both elements of type-2 inflammatory responses and their relative influence in these common conditions and consider possible impacts of this on treatment selection.

Novel method to analyze cell kinetics for the rapid diagnosis and determination of the causative agent in allergy

Drug-induced allergy (DIA), an unexpectedly triggered side effect of drugs used for therapeutic purposes, is a serious clinical issue that needs to be resolved because it interrupts the treatment of the primary disease. Since conventional allergy testing is insufficient to accurately predict the occurrence of DIA or to determine the drugs causing it, the development of diagnostic and predictive tools for allergic reactions is important. We demonstrated a novel method, termed high-sensitive allergy test (HiSAT), for the rapid diagnosis of allergy (within 1 hr; with true-positive diagnosis rates of 89% and 9% for patients with and without allergy-like symptoms, respectively). HiSAT analyzes the cell kinetics as an index against chemotactic factors in a patient’s serum, as different from the diagnosis using conventional methods. Once allergy has occurred, HiSAT can be used to determine the causative medicine using culture supernatants incubated with the subject’s lymphocytes and the test allergen. This test is more efficient (60%) than the lymphocyte transformation test (20%). Furthermore, in HiSAT, cell mobility significantly increases in a dose-dependent manner against supernatant incubated with lymphocytes from a subject with pollinosis collected at a time when the subject is without allergic symptoms and the antigen. The result demonstraed that HiSAT might be a promising method to rapidly diagnose DIA or to determine with high accuracy the antigen causing allergy.

Titanium dioxide particles modulate epithelial barrier protein, Claudin 7 in asthma

Epithelial barrier dysfunction is involved in allergic inflammation and asthma, due to increased exposure of sub-epithelial tissues to inhaled allergens and air pollutants. The tight junction proteins claudins (CLDNs) are important regulators of paracellular permeability. CLDN7 is expressed in the alveolar epithelium; however, its contribution to airway barrier function remains unclear. The aim of this study was to assess the effects of TiO₂ on epithelial barrier function in asthma. Mice were sensitized and challenged with OVA or exposed to TiO₂ on days 21-23. The effect of TiO₂ on CLDN7 was assessed by ELISA, immunoblotting, and immunohistochemical analysis. The levels of CLDN7 in the plasma of patients with asthma and healthy individuals were also examined. CLDN7 levels were lower in plasma from patients with asthma compared with healthy individuals. CLDN7 levels were associated with FEV₁/FVC and the blood eosinophils (%) in patients with asthma. Although CLDN7 expression was elevated in the lungs of mice with asthma and in NHBE cells treated with HDM extracts, its expression was suppressed by exposure to TiO₂. p-AKT and p-ERK was increased in asthmatic mice and decreased in mice with TiO₂ treatment. p-AKT and p-ERK was decreased in NHBE cells treated with TiO₂ and HDM extracts. Trans-epithelial electrical resistance (TEER) was higher in NHBE cells treated with TiO₂ or HDM extracts; however, this was decreased by concurrent TiO₂ and HDM extracts treatment. Our data suggest that particulate matter contributes to airway epithelial barrier dysfunction and results in airway inflammation and responsiveness.

Inhibition of miR-99a-5p prevents allergen-driven airway exacerbations without compromising type-2 memory responses in the intestine following helminth infection

Acute exacerbations (AE) of asthma, remain one of the biggest concerns for patients living with asthma. As such, identifying the causes, the molecular mechanisms involved and new therapeutic interventions to prevent AE is a high priority. Immunity to intestinal helminths involves the reactivation of type-2 immune responses leading to smooth muscle contraction and mucus hypersecretion-physiological processes very similar to acute exacerbations in the airways following allergen exposure. In this study, we employed a murine model of intestinal helminth infection, using Heligmosomoides polygyrus, to identify miRNAs during active expulsion, as a system for the identification of miRNAs that may contribute to AE in the airways. Concomitant with type-2 immunity and expulsion of H. polygyrus, we identified miR-99a-5p, miR-148a-3p and miR-155-5p that were differentially regulated. Systemic inhibition of these miRNAs, alone or in combination, had minimal impact on expulsion of H. polygyrus, but inhibition of miR-99a-5p or miR-155-5p significantly reduced house dust mite (HDM)-driven acute inflammation, modelling human acute exacerbations. Immunological, pathological and transcriptional analysis identified that miR-155-5p or miR-99a-5p contribute significantly to HDM-driven AE and that transient inhibition of these miRNAs may provide relief from allergen-driven AE, without compromising anti-helminth immunity in the gut.

An endothelial microRNA-1-regulated network controls eosinophil trafficking in asthma and chronic rhinosinusitis

BACKGROUND

Airway eosinophilia is a prominent feature of asthma and chronic rhinosinusitis (CRS), and the endothelium plays a key role in eosinophil trafficking. To date, microRNA-1 (miR-1) is the only microRNA known to be regulated in the lung endothelium in asthma models.

OBJECTIVE

We sought to determine the role of endothelial miR-1 in allergic airway inflammation.

METHODS

We measured microRNA and mRNA expression using quantitative RT-PCR. We used ovalbumin and house dust mite models of asthma. Endothelium-specific overexpression of miR-1 was achieved through lentiviral vector delivery or induction of a transgene. Tissue eosinophilia was quantified by using Congo red and anti-eosinophil peroxidase staining. We measured eosinophil binding with a Sykes-Moore adhesion chamber. Target recruitment to RNA-induced silencing complex was assessed by using anti-Argonaute2 RNA immunoprecipitation. Surface P-selectin levels were measured by using flow cytometry.

RESULTS

Serum miR-1 levels had inverse correlations with sputum eosinophilia, airway obstruction, and number of hospitalizations in asthmatic patients and sinonasal tissue eosinophilia in patients with CRS. IL-13 stimulation decreased miR-1 levels in human lung endothelium. Endothelium-specific overexpression of miR-1 reduced airway eosinophilia and asthma phenotypes in murine models and inhibited IL-13-induced eosinophil binding to endothelial cells. miR-1 recruited P-selectin, thymic stromal lymphopoietin, eotaxin-3, and thrombopoietin receptor to the RNA-induced silencing complex; downregulated these genes in the lung endothelium; and reduced surface P-selectin levels in IL-13-stimulated endothelial cells. In our asthma and CRS cohorts, miR-1 levels correlated inversely with its target genes.

CONCLUSION

Endothelial miR-1 regulates eosinophil trafficking in the setting of allergic airway inflammation. miR-1 has therapeutic potential in asthmatic patients and patients with CRS.

Streptococcus pneumoniae aminopeptidase N regulates dendritic cells that attenuates type-2 airway inflammation in murine allergic asthma

BACKGROUND AND PURPOSE

Epidemiological and experimental studies suggest that microbial exposure in early childhood is linked with reduced risk to suffer asthma. Thus microbial components with immunoregulatory capabilities might serve as a preventive strategy for allergic asthma. Recently, it was identified that Streptococcus pneumoniae aminopeptidase N (PepN) could suppress T cell effector function. We sought to investigate the effect of PepN on murine allergic asthma and elucidate the underlying mechanism.

EXPERIMENTAL APPROACH

The effects of intranasal administration of PepN during or before sensitization were examined in ovalbumin (OVA)-induced murine allergic asthma. The roles of CD11b⁺ dendritic cells in PepN treated OVA-induced allergic asthma were evaluated by flow cytometry, cytokines detection and adoptive transfer. Moreover, the numbers of lung type 2 innate lymphoid cells (ILC2s) were also detected.

KEY RESULTS

Administration of PepN during or before sensitization attenuated type-2 airway inflammation (eosinophilia, mucus hypersecretion, Th2 cytokines production and IgE production) in allergic asthma mice. PepN reduced lung accumulation of CD11b⁺ dendritic cells, which was accompanied by diminished dendritic cell-attracting chemokine CCL20 production as well as CCL17 and CCL22, which are Th2-cell chemokines predominantly produced by CD11b⁺ dendritic cells. Adoptive transfer of BM-derived CD11b⁺ dendritic cells abolished the inhibitory effect of PepN on OVA-induced type-2 airway inflammation. The numbers of lung ILC2s were decreased in asthmatic mice receiving PepN.

CONCLUSION AND IMPLICATIONS

PepN alleviated type-2 inflammation in OVA-induced allergic asthma mice, which was mediated by regulation of lung CD11b⁺ dendritic cells. Our study provides a novel strategy for the prevention of allergic asthma.

Amelioration of Autoimmune Diabetes of NOD Mice by Immunomodulating Probiotics

Type 1 autoimmune diabetes is an autoimmune disease characterized by specific destruction of pancreatic β-cells producing insulin. Recent studies have shown that gut microbiota and immunity are closely linked to systemic immunity, affecting the balance between pro-inflammatory and regulatory immune responses. Altered gut microbiota may be causally related to the development of immune-mediated diseases, and probiotics have been suggested to have modulatory effects on inflammatory diseases and immune disorders. We studied whether a probiotic combination that has immunomodulatory effects on several inflammatory diseases can reduce the incidence of diabetes in non-obese diabetic (NOD) mice, a classical animal model of human T1D. When Immune Regulation and Tolerance 5 (IRT5), a probiotic combination comprising Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus reuteri, Bifidobacterium bifidium, and Streptococcus thermophiles, was administered 6 times a week for 36 weeks to NOD mice, beginning at 4 weeks of age, the incidence of diabetes was significantly reduced. Insulitis score was also significantly reduced, and β-cell mass was conversely increased by IRT5 administration. IRT5 administration significantly reduced gut permeability in NOD mice. The proportion of total regulatory T cells was not changed by IRT5 administration; however, the proportion of CCR9⁺ regulatory T (Treg) cells expressing gut-homing receptor was significantly increased in pancreatic lymph nodes (PLNs) and lamina propria of the small intestine (SI-LP). Type 1 T helper (Th1) skewing was reduced in PLNs by IRT5 administration. IRT5 could be a candidate for an effective probiotic combination, which can be safely administered to inhibit or prevent type 1 diabetes (T1D).

FABP5 as a possible biomarker in atopic march: FABP5-induced Th17 polarization, both in mouse model and human samples

Background

While the incidence of patients with atopic dermatitis (AD) with atopic march (AM) showing respiratory allergy is steadily rising, the pathomechanism is still unknown. There are currently no biomarkers to predict progression of AM.

Methods

To explore the mechanism of AM, patients with AD and AM and healthy controls were recruited and RNA microarray, flow cytometry, quantitative real-time polymerase chain reaction, and immunofluorescence staining were performed. We also co-cultured dendritic cells and CD4⁺T cells with various Dermatophagoides farinae allergen fractions. Cytokine levels were evaluated using enzyme-linked immunosorbent assay.

Findings

Both fatty-acid-binding protein 5 (FABP5) and Th17-related genes were more highly expressed in AM. FABP5 knockdown significantly decreased Th17-inducing cytokines in keratinocytes and IL-17A in T cells from AM patients. Further confirmation was obtained using an AM mice model compared to mice without AM. Der f 1, a major D. farinae allergen, increased FABP5 and IL-17A expression in T cells from AM patients. Higher serum FABP5 levels from AM patients were positively correlated with serum IL-17A levels.

Interpretation

FABP5 expression, possibly enhanced by higher epicutaneous and respiratory sensitization to Der f 1, may directly promote Th17 responses in AD patients with AM. Thus, AM progression can be explained by Th17 reaction induced by FABP5. FABP5 was identified as a potential biomarker in AM.

Funding

This study was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (Ministry of Science and ICT; No. NRF-2017R1A2B4009568), grants of the Korean Health Technology R&D Project, Ministry for Health, Welfare & Family Affairs, and the Republic of Korea (HI13C0010, HI14C1324, HI14C1799).

Relationship between chemokines and T lymphocytes in the context of respiratory allergies (Review)

Allergic diseases have been classified in the last decades using various theories. The main classes of the newest classification in allergic respiratory diseases focus on the characterization of the endotype (which takes into account biomarkers related to determinant pathophysiological mechanisms) and of the phenotype (based on the description of the disease). Th2, Th1 and Th17 lymphocytes and the type of inflammatory response mediated by them represent the basis for Th2 and non-Th2 endotype classification. In addition, new lymphocytes were also used to characterize allergic diseases: Th9 lymphocytes, Th22 lymphocytes, T follicular helper cells (T_FH) lymphocytes and invariant natural killer T (iNKT) lymphocytes. In the last decade, a growing body of evidence focused on chemokines, chemoattractant cytokines, which seems to have an important contribution to the pathogenesis of this pathology. This review presents the interactions between chemokines and Th lymphocytes in the context of Th2/non-Th2 endotype classification of respiratory allergies.

Lack of interleukin-33 and its receptor does not prevent calcipotriol-induced atopic dermatitis-like inflammation in mice

Current studies addressing the influence of interleukin-33 or its receptor (IL-33R/ST2) on development of atopic dermatitis-like inflammation in mice have reported conflicting results. We compared the response in single- and double-deficient IL-33^−/−/ST2^−/− C57BL/6J BomTac mice in the well-established calcipotriol-induced model of atopic dermatitis. All genotypes (groups of up to 14 mice) developed atopic dermatitis-like inflammation yet we observed no biologically relevant difference between groups in gross anatomy or ear thickness. Moreover, histological examination of skin revealed no differences in mononuclear leukocyte and granulocyte infiltration nor Th2 cytokine levels (IL-4 and IL-13). Finally, skin CD45+ cells and CD3+ cells were found at similar densities across all groups. Our findings indicate that lack of interleukin-33 and its receptor ST2 does not prevent the development of AD-like skin inflammation.

TSLP drives acute TH2-cell differentiation in lungs

BACKGROUND

Thymic stromal lymphopoietin (TSLP) is an epithelial-derived cytokine that is important for the development of type 2 inflammatory responses at mucosal surfaces.

OBJECTIVE

In humans, TSLP level has been found to be elevated in the lungs of patients with asthma, and in mouse models, TSLP can promote type 2 airway inflammation, primarily through the activation of dendritic cells. However, the mechanisms underlying its role remain unclear. The objective of this study was to provide a mechanistic analysis of TSLP-mediated type 2 airway inflammation METHODS: To dissect the mechanisms of TSLP-mediated type 2 responses, mice were treated with TSLP and antigen to evaluate cellular immune responses. Flow cytometric analyses were used to follow responses in the airways, and conditional deletion of TSLP receptor and adoptive transfer were used to identify the cellular subsets involved in this inflammatory response.

RESULTS

We showed that TSLP can directly promote T_H2-cell differentiation in the lung, independent of the draining lymph nodes. We also identified a population of patrolling monocytes/interstitial macrophages (IMs) (CD11c-expressing IMs) that are both necessary and sufficient for TSLP-mediated T_H2-cell differentiation and airway inflammation. T_H2-cell-driven airway eosinophilia is attenuated by ablation of CD11c-expressing IMs or by selective deficiency of TSLP receptor signaling in these cells. More importantly, CD11c-expressing IMs are sufficient for the induction of acute T_H2-cell responses in the lungs that is independent of dendritic cells and T-cell priming in the draining lymph nodes.

CONCLUSION

These findings indicate a novel mechanistic role for TSLP and CD11c-expressing IMs in the development of acute T_H2-cell-dependent allergic airway inflammation. This work also demonstrates a new role for TSLP in promoting type 2 responses directly in the lung.

Oral Administration of Flavonifractor plautii Strongly Suppresses Th2 Immune Responses in Mice

The bacterium Flavonifractor plautii (FP), which is found in human feces, has been reported to participate in catechin metabolism in the gut, but this bacterium's effects on immune function are unclear. We assessed the effect of oral administration of FP on the immune response in ovalbumin (OVA) -sensitized mice. We demonstrated that the FP treatment suppressed interleukin (IL)-4 in splenocytes and OVA-specific IgE production in serum from OVA-sensitized mice. Moreover, oral administration of FP augmented CD4⁺CD25⁺ T cells and CD103⁺CD11c⁺ DCs. In animals of the FP group, the proportion of FP was increased in the mesenteric lymph nodes (MLNs), as was the proportion of Deferribacteres in the cecum. Oral administration of FP may inhibit the Th2 immune response by incorporation into the MLNs and/or by inducing changes in the gut microbiota. Thus, FP may be useful in alleviating antigen-induced Th2 immune responses.

CCR5 attenuates neutrophilic airway inflammation exacerbated by infection with rhinovirus

Human rhinovirus (hRV) is the most common cause of asthma exacerbation characterized by clinical and pathophysiological heterogeneity. Steroid-sensitive, Th2 type-eosinophilic asthma has been somewhat studied, but hRV-induced neutrophilic asthma exacerbation is poorly understood. Here, CCR5 was found to play a role in attenuating neutrophilic airway inflammation in hRV-induced asthma exacerbation using chicken ovalbumin (OVA)-based model. CCR5 deficiency resulted in exacerbated neutrophilic asthmatic responses in airways following hRV infection. CCR5-deficient mice showed enhanced mucus expression and altered expression of tight junction proteins in lung tissues. CCR5-deficient mice were also manifested with influx of CD45⁺CD11b⁺Siglec-F⁺Gr-1⁺ neutrophils, along with enhanced production of IL-17A, IFN-γ, IL-6, IL-1β cytokines in inflamed tissues. In contrast, CCR5-deficient mice elicited down-regulation of Th2-related cytokine proteins following hRV infection. More interestingly, the lack of CCR5 altered the equilibrium of CD4⁺FoxP3⁺ Tregs and IL-17⁺CD4⁺ Th17 in inflamed tissues. CCR5-deficient mice showed increased frequency and absolute number of IL-17-producing CD4⁺ Th17 cells in lung tissues compared to wild-type mice, whereas the reduced infiltration of CD4⁺FoxP3⁺ Treg cells was observed. CCR5 deficiency resulted in the skewed production of Th17 and Th1 cytokines in lymph nodes and lungs upon OVA stimulation. Likewise, CCR5-deficient mice showed enhanced expression of Th17-inducing cytokines (IL-1β, IL-6, and TNF-α) in lung tissues. These results imply that CCR5 deficiency facilitates Th17 airway inflammation during hRV-induced asthma exacerbation, along with suppressing Th2 responses. Furthermore, our results suggest that CCR5 attenuates hRV-induced neutrophilic airway inflammation through conserving the equilibrium of CD4⁺Foxp3⁺ Treg cells and IL-17⁺CD4⁺ Th17 cells in hRV-induced asthma exacerbation.

Mitochondria: An Integrative Hub Coordinating Circadian Rhythms, Metabolism, the Microbiome, and Immunity

There is currently some understanding of the mechanisms that underpin the interactions between circadian rhythmicity and immunity, metabolism and immune response, and circadian rhythmicity and metabolism. In addition, a wealth of studies have led to the conclusion that the commensal microbiota (mainly bacteria) within the intestine contributes to host homeostasis by regulating circadian rhythmicity, metabolism, and the immune system. Experimental studies on how these four biological domains interact with each other have mainly focused on any two of those domains at a time and only occasionally on three. However, a systematic analysis of how these four domains concurrently interact with each other seems to be missing. We have analyzed current evidence that signposts a role for mitochondria as a key hub that supports and integrates activity across all four domains, circadian clocks, metabolic pathways, the intestinal microbiota, and the immune system, coordinating their integration and crosstalk. This work will hopefully provide a new perspective for both hypothesis-building and more systematic experimental approaches.

Dissecting the Heterogeneity in T-Cell Mediated Inflammation in IBD

Infiltration of the lamina propria by inflammatory CD4+ T-cell populations is a key characteristic of chronic intestinal inflammation. Memory-phenotype CD4+ T-cell frequencies are increased in inflamed intestinal tissue of IBD patients compared to tissue of healthy controls and are associated with disease flares and a more complicated disease course. Therefore, a tightly controlled balance between regulatory and inflammatory CD4+ T-cell populations is crucial to prevent uncontrolled CD4+ T-cell responses and subsequent intestinal tissue damage. While at steady state, T-cells display mainly a regulatory phenotype, increased in Th1, Th2, Th9, Th17, and Th17.1 responses, and reduced Treg and Tr1 responses have all been suggested to play a role in IBD pathophysiology. However, it is highly unlikely that all these responses are altered in each individual patient. With the rapidly expanding plethora of therapeutic options to inhibit inflammatory T-cell responses and stimulate regulatory T-cell responses, a crucial need is emerging for a robust set of immunological assays to predict and monitor therapeutic success at an individual level. Consequently, it is crucial to differentiate dominant inflammatory and regulatory CD4+ T helper responses in patients and relate these to disease course and therapy response. In this review, we provide an overview of how intestinal CD4+ T-cell responses arise, discuss the main phenotypes of CD4+ T helper responses, and review how they are implicated in IBD.

Oesophageal eosinophilia accompanies food allergy to hen egg white protein in young pigs

BACKGROUND

Esophagitis with eosinophilia, inflammation, and fibrosis represent a chronic condition in humans with food allergies.

OBJECTIVE

In this investigation, we asked whether esophagitis with an eosinophilic component is observed in young pigs rendered allergic to hen egg white protein (HEWP).

METHODS

Food allergy was induced in young pigs using two protocols. In one protocol, sensitized pigs were challenged by gavage with a single dose of HEWP. Clinical signs were monitored for 24 hours, and then, gastrointestinal (GI) tissues were collected for histological examination. The phenotype of circulating, ovalbumin (OVA)-specific T cells also was examined in HEWP challenged animals. In the second protocol, sensitized animals were fed HEWP for 28 days. Animals were then examined by endoscopy and gastrointestinal tissues collected for histological examination.

RESULTS

In pigs challenged by gavage with HEWP, clinical signs were noted in 5/6 pigs including diarrhoea, emesis, and skin rash. Clinical signs were not seen in any control group. Histological analysis revealed significant levels of oesophageal eosinophilic infiltration (P < .05) in 4/6 of these animals, with two also displaying eosinophilic infiltration in the stomach. Eosinophils were not increased in ileum or colon samples. Increased numbers of circulating, OVA-specific CD4+ T cells also were observed in pigs that received HEWP by gavage. In the group of animals fed HEWP, endoscopy revealed clinical signs of esophagitis including oedema, granularity, white spots, and furrowing, while histology revealed oedema, immune cell infiltration, and basal zone hyperplasia.

CONCLUSIONS AND CLINICAL RELEVANCE

Food allergy in the pig can be associated with esophagitis based on histological and endoscopic findings, including eosinophilic infiltration. The young pig may, therefore, be a useful large animal model for the study of eosinophilic esophagitis in humans.

Foxo in T Cells Regulates Thermogenic Program through Ccr4/Ccl22 Axis

Crosstalk between immunity and the thermogenic program has provided insight into metabolic energy regulation. Here, we generated thermogenic program-accelerating mice (T-QKO), in which Foxo1 is knockout and Foxo3 is hetero-knockout in CD4⁺ T cells. T-QKO exhibit lean phenotype under HFD due to increased energy expenditure. Cold exposure significantly increased expression of the thermogenic genes (Ppargc1a and Ucp1), Th2 cytokines (Il4 and Il13), and Th2 marker gene (Gata3) in subcutaneous adipose tissue (SC) of T-QKO. Furthermore, Ccr4 expression was significantly increased in Th2 cells of T-QKO, and cold exposure induced Ccl22 expression in SC, leading to increased accumulation of Th2 cell population in SC of T-QKO. These data reveal a mechanism by which cold exposure induces selective recruitment of Th2 cells into SC, leading to regulation of energy expenditure by generating beige adipocyte and suggest that inhibition of Foxo in T cells may support a strategy to prevent and treat obesity.

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T-QKO increases Gata3 and Ccr4 expression in CD4⁺ T cells

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Cold exposure increases Ccl22 expression in subcutaneous adipose tissue

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Cold exposure increases SC-specific recruitment of Th2 cells in T-QKO

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Recruited Th2 cells secrete IL-4 and IL-13 and increase beiging of adipocytes

Modulation of CRTh2 expression on allergen-specific T cells following peptide immunotherapy

Background

Allergen immunotherapy using synthetic peptide T‐cell epitopes (Cat‐PAD) from the major cat allergen Fel d 1 has been shown, in allergen exposure studies, to significantly reduce symptoms of allergic rhinoconjunctivitis in cat‐allergic subjects. However, the immunological mechanisms underlying clinical benefit remain only partially understood. Since previous studies of whole allergen immunotherapy demonstrated a reduction in the frequency of allergen‐specific (MHC II tetramer⁺) CD4⁺ T cells expressing the chemokine receptor CRTh2, we assessed the impact of Cat‐PAD on the frequency and functional phenotype of Fel d 1‐specific CD4⁺ T cells.

Methods

Using before and after treatment samples from subjects enrolled in a randomized, double‐blind, placebo‐controlled trial of Cat‐PAD, we employed Fel d 1 MHC II tetramers and flow cytometry to analyze the expression of chemokine receptors CCR3, CCR4, CCR5, CXCR3, and CRTh2, together with markers of memory phenotype (CD27 and CCR7) on Fel d 1‐specific CD4⁺ T cells.

Results

No statistically significant change in the frequency of Fel d 1‐specific CD4⁺ T cells, nor in their expression of chemokine receptors or memory phenotype, was observed. However, a significant reduction in cell surface expression of CRTh2 was observed between the placebo and active groups (P = 0.047).

Conclusions

Peptide immunotherapy with Cat‐PAD does not significantly alter the frequency or phenotype of Fel d 1‐CD4⁺ T cells, but may decrease their expression of CRTh2.

Chronic Inflammation Directs an Olfactory Stem Cell Functional Switch from Neuroregeneration to Immune Defense

Although olfactory mucosa possesses long-lived horizontal basal stem cells (HBCs) and remarkable regenerative capacity, the function of human olfactory neuroepithelium is significantly impaired in chronic inflammatory rhinosinusitis. Here, we show that, while inflammation initially damages olfactory neurons and activates HBC-mediated regeneration, continued inflammation locks HBCs in an undifferentiated state. Global gene expression in mouse HBCs reveals broad upregulation of NF-κB-regulated cytokines and chemokines including CCL19, CCL20, and CXCL10, accompanied by enhancement of "stemness"-related transcription factors. Loss-of-function studies identify an NF-κB-dependent role of HBCs in amplifying inflammatory signaling, contributing to macrophage and T cell local proliferation. Chronically activated HBCs signal macrophages to maintain immune defense and prevent Treg development. In diseased human olfactory tissue, activated HBCs in a P63⁺ undifferentiated state similarly contribute to inflammation through chemokine production. These observations establish a mechanism of chronic rhinosinusitis-associated olfactory loss, caused by a functional switch of neuroepithelial stem cells from regeneration to immune defense.

Increased number of regulatory T cells in esophageal tissue of patients with eosinophilic esophagitis in comparison to gastro esophageal reflux disease and control groups

BACKGROUND

Eosinophilic esophagitis (EoE) is a primarily polygenic allergic disorder. Although most patients have IgE sensitization, it seems that non-IgE mediated responses mainly contribute to the pathogenesis of EoE. Regulatory T cells (Tregs) may have an important role in allergies. There are limited data on the association of Tregs and EoE. In this study, we enumerated and compared T lymphocytes and Tregs in esophageal tissue of patients with EoE, gastroesophageal reflux disease (GERD) and normal controls.

METHODS

Ten patients with EoE, ten patients with GERD and eight normal controls were included. Immunohistochemistry staining was used to enumerate T lymphocytes and Tregs. CD3+ cells were considered as T cells and FOXP3+, CD3+ cells were considered as Tregs. T cells and Tregs were counted in 10 high power fields (HPF) (×400) for each patient and the average of 10 HPFs was recorded.

RESULTS

The mean±SEM of Tregs in esophageal tissue of patients with EoE (10.90±2.14cells/HPF) was significantly higher than the GERD (2.77±0.66cells/HPF) and control groups (0.37±0.08cells/HPF) (P<0.001). Additionally, the mean±SEM of T lymphocytes in esophageal tissue of patients with EoE (24.39±3.86cells/HPF) were increased in comparison to the GERD (10.07±2.65cells/HPF) and control groups (3.17±0.93cells/HPF) (P<0.001).

CONCLUSION

There is an increase in the number of esophageal T lymphocytes and regulatory T cells in patients with EoE compared to the GERD and control groups.

Low-molecular-weight-heparin increases Th1- and Th17-associated chemokine levels during pregnancy in women with unexplained recurrent pregnancy loss: a randomised controlled trial

Low-molecular-weight heparin (LMWH) is widely used to treat recurrent pregnancy loss (RPL) because of its anti-coagulant effects. Although in vitro studies have suggested additional immunological effects, these are debated. We therefore investigated whether LMWH could modulate immune responses in vivo during pregnancy of women with unexplained RPL. A Swedish open multi-centre randomised controlled trial included 45 women treated with tinzaparin and 42 untreated women. Longitudinally collected plasma samples were obtained at gestational weeks (gw) 6, 18, 28 and 34 and analysed by multiplex bead technology for levels of 11 cytokines and chemokines, chosen to represent inflammation and T-helper subset-associated immunity. Mixed linear models test on LMWH-treated and untreated women showed differences during pregnancy of the Th1-associated chemokines CXCL10 (p = 0.01), CXCL11 (p < 0.001) and the Th17-associated chemokine CCL20 (p = 0.04), while CCL2, CCL17, CCL22, CXCL1, CXCL8, CXCL12, CXCL13 and IL-6 did not differ. Subsequent Student's t-test showed significantly higher plasma levels of CXCL10 and CXCL11 in treated than untreated women at gw 28 and 34. The consistent increase in the two Th1-associated chemokines suggests a potential proinflammatory and unfavourable effect of LMWH treatment during later stages of pregnancy, when Th1 immunity is known to disrupt immunological tolerance.

Programming of Distinct Chemokine-Dependent and -Independent Search Strategies for Th1 and Th2 Cells Optimizes Function at Inflamed Sites

T-helper (Th) cell differentiation drives specialized gene programs that dictate effector T cell function at sites of infection. Here, we have shown Th cell differentiation also imposes discrete motility gene programs that shape Th1 and Th2 cell navigation of the inflamed dermis. Th1 cells scanned a smaller tissue area in a G protein-coupled receptor (GPCR) and chemokine-dependent fashion, while Th2 cells scanned a larger tissue area independent of GPCR signals. Differential chemokine reliance for interstitial migration was linked to STAT6 transcription-factor-dependent programming of integrin α_Vβ₃ expression: Th2 cell differentiation led to high α_Vβ₃ expression relative to Th1 cells. Th1 and Th2 cell modes of motility could be switched simply by manipulating the amount of α_Vβ₃ on the cell surface. Deviating motility modes from those established during differentiation impaired effector function. Thus, programmed expression of α_Vβ₃ tunes effector T cell reliance on environmental cues for optimal exploration of inflamed tissues.

Temporary Reduction of Membrane CD4 with the Antioxidant MnTBAP Is Sufficient to Prevent Immune Responses Induced by Gene Transfer

Unexpectedly, the synthetic antioxidant MnTBAP was found to cause a rapid and reversible downregulation of CD4 on T cells in vitro and in vivo. This effect resulted from the internalization of membrane CD4 T cell molecules into clathrin-coated pits and involved disruption of the CD4/p56^Lck complex. The CD4 deprivation induced by MnTBAP had functional consequences on CD4-dependent infectious processes or immunological responses as shown in various models, including gene therapy. In cultured human T cells, MnTBAP-induced downregulation of CD4 functionally suppressed gp120- mediated lentiviral transduction in a model relevant for HIV infection. The injection of MnTBAP in mice reduced membrane CD4 on lymphocytes in vivo within 5 days of treatment, preventing OVA peptide T cell immunization while allowing subsequent immunization once treatment was stopped. In a mouse gene therapy model, MnTBAP treatment at the time of adenovirus-associated virus (AAV) vector administration, successfully controlled the induction of anti-transgene and anti-capsid immune responses mediated by CD4⁺ T cells, enabling the redosing mice with the same vector. These functional data provide new avenues to develop alternative therapeutic immunomodulatory strategies based on temporary regulation of CD4. These could be particularly useful for AAV gene therapy in which novel strategies for redosing are needed.

CD26 and Asthma: a Comprehensive Review

Asthma is a heterogeneous and chronic inflammatory family of disorders of the airways with increasing prevalence that results in recurrent and reversible bronchial obstruction and expiratory airflow limitation. These diseases arise from the interaction between environmental and genetic factors, which collaborate to cause increased susceptibility and severity. Many asthma susceptibility genes are linked to the immune system or encode enzymes like metalloproteases (e.g., ADAM-33) or serine proteases. The S9 family of serine proteases (prolyl oligopeptidases) is capable to process peptide bonds adjacent to proline, a kind of cleavage-resistant peptide bonds present in many growth factors, chemokines or cytokines that are important for asthma. Curiously, two serine proteases within the S9 family encoded by genes located on chromosome 2 appear to have a role in asthma: CD26/dipeptidyl peptidase 4 (DPP4) and DPP10. The aim of this review is to summarize the current knowledge about CD26 and to provide a structured overview of the numerous functions and implications that this versatile enzyme could have in this disease, especially after the detection of some secondary effects (e.g., viral nasopharyngitis) in type II diabetes mellitus patients (a subset with a certain risk of developing obesity-related asthma) upon CD26 inhibitory therapy.

The Applicability of Mouse Models to the Study of Human Disease

The laboratory mouse Mus musculus has long been used as a model organism to test hypotheses and treatments related to understanding the mechanisms of disease in humans; however, for these experiments to be relevant, it is important to know the complex ways in which mice are similar to humans and, crucially, the ways in which they differ. In this chapter, an in-depth analysis of these similarities and differences is provided to allow researchers to use mouse models of human disease and primary cells derived from these animal models under the most appropriate and meaningful conditions.

Although there are considerable differences between mice and humans, particularly regarding genetics, physiology, and immunology, a more thorough understanding of these differences and their effects on the function of the whole organism will provide deeper insights into relevant disease mechanisms and potential drug targets for further clinical investigation. Using specific examples of mouse models of human lung disease, i.e., asthma, chronic obstructive pulmonary disease, and pulmonary fibrosis, this chapter explores the most salient features of mouse models of human disease and provides a full assessment of the advantages and limitations of these models, focusing on the relevance of disease induction and their ability to replicate critical features of human disease pathophysiology and response to treatment. The chapter concludes with a discussion on the future of using mice in medical research with regard to ethical and technological considerations.