T cell co-stimulatory molecules: a co-conspirator in the pathogenesis of eosinophilic esophagitis?

Realigning the LIGHT signaling network to control dysregulated inflammation

Advances in understanding the physiologic functions of the tumor necrosis factor superfamily (TNFSF) of ligands, receptors, and signaling networks are providing deeper insight into pathogenesis of infectious and autoimmune diseases and cancer. LIGHT (TNFSF14) has emerged as an important modulator of critical innate and adaptive immune responses. LIGHT and its signaling receptors, herpesvirus entry mediator (TNFRSF14), and lymphotoxin β receptor, form an immune regulatory network with two co-receptors of herpesvirus entry mediator, checkpoint inhibitor B and T lymphocyte attenuator, and CD160. Deciphering the fundamental features of this network reveals new understanding to guide therapeutic development. Accumulating evidence from infectious diseases points to the dysregulation of the LIGHT network as a disease-driving mechanism in autoimmune and inflammatory reactions in barrier organs, including coronavirus disease 2019 pneumonia and inflammatory bowel diseases. Recent clinical results warrant further investigation of the LIGHT regulatory network and application of target-modifying therapeutics for disease intervention.

Immunologic and pathologic characterization of a novel swine biomedical research model for eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a chronic allergy-mediated condition with an increasing incidence in both children and adults. Despite EoE's strong impact on human health and welfare, there is a large unmet need for treatments with only one recently FDA-approved medication for EoE. The goal of this study was to establish swine as a relevant large animal model for translational biomedical research in EoE with the potential to facilitate development of therapeutics. We recently showed that after intraperitoneal sensitization and oral challenge with the food allergen hen egg white protein (HEWP), swine develop esophageal eosinophilia-a hallmark of human EoE. Herein, we used a similar sensitization and challenge treatment and evaluated immunological and pathological markers associated with human EoE. Our data demonstrate that the incorporated sensitization and challenge treatment induces (i) a systemic T-helper 2 and IgE response, (ii) a local expression of eotaxin-1 and other allergy-related immune markers, (iii) esophageal eosinophilia (>15 eosinophils/0.24 mm²), and (iv) esophageal endoscopic findings including linear furrows and white exudates. Thereby, we demonstrate that our sensitization and oral challenge protocol not only induces the underlying immune markers but also the micro- and macro-pathological hallmarks of human EoE. This swine model for EoE represents a novel relevant large animal model that can drive translational biomedical research to develop urgently needed treatment strategies for EoE.

Increased Production of LIGHT by T Cells in Eosinophilic Esophagitis Promotes Differentiation of Esophageal Fibroblasts Toward an Inflammatory Phenotype

BACKGROUND & AIMS

Eosinophilic esophagitis (EoE) is an antigen-mediated eosinophilic disease of the esophagus that involves fibroblast activation and progression to fibrostenosis. Cytokines produced by T-helper type 2 cells and transforming growth factor beta 1 (TGFβ1) contribute to the development of EoE, but other cytokines involved in pathogenesis are unknown. We investigate the effects of tumor necrosis factor superfamily member 14 (TNFSF14, also called LIGHT) on fibroblasts in EoE.

METHODS

We analyzed publicly available esophageal CD3+ T-cell single-cell sequencing data for expression of LIGHT. Esophageal tissues were obtained from pediatric patients with EoE or control individuals and analyzed by immunostaining. Human primary esophageal fibroblasts were isolated from esophageal biopsy samples of healthy donors or patients with active EoE. Fibroblasts were cultured; incubated with TGFβ1 and/or LIGHT; and analyzed by RNA sequencing, flow cytometry, immunoblots, immunofluorescence, or reverse transcription polymerase chain reaction. Eosinophils were purified from peripheral blood of healthy donors, incubated with interleukin 5, cocultured with fibroblasts, and analyzed by immunohistochemistry.

RESULTS

LIGHT was up-regulated in the esophageal tissues from patients with EoE, compared with control individuals, and expressed by several T-cell populations, including T-helper type 2 cells. TNF receptor superfamily member 14 (TNFRSF14, also called HVEM) and lymphotoxin beta receptor are receptors for LIGHT that were expressed by fibroblasts from healthy donors or patients with active EoE. Stimulation of esophageal fibroblasts with LIGHT induced inflammatory gene transcription, whereas stimulation with TGFβ1 induced transcription of genes associated with a myofibroblast phenotype. Stimulation of fibroblasts with TGFβ1 increased expression of HVEM; subsequent stimulation with LIGHT resulted in their differentiation into cells that express markers of myofibroblasts and inflammatory chemokines and cytokines. Eosinophils tethered to esophageal fibroblasts after LIGHT stimulation via intercellular adhesion molecule-1.

CONCLUSIONS

T cells in esophageal tissues from patients with EoE express increased levels of LIGHT compared with control individuals, which induces differentiation of fibroblasts into cells with inflammatory characteristics. TGFβ1 increases fibroblast expression of HVEM, a receptor for LIGHT. LIGHT mediates interactions between esophageal fibroblasts and eosinophils via ICAM1. This pathway might be targeted for the treatment of EoE.

Management of Eosinophilic Esophagitis: Dietary and Nondietary Approaches

Eosinophilic esophagitis (EoE) is an allergen-driven chronic inflammatory condition, characterized by symptoms related to esophageal dysfunction and confirmed histologically by esophageal mucosal eosinophilia. Since its first description in the 1990s, the incidence and prevalence of EoE have been on the rise. It is known to affect all ages of various ethnic backgrounds and both sexes; however, it is most seen in White males. Children with EoE often present with abdominal pain, nausea, vomiting, and failure to thrive, whereas adults with EoE typically present with dysphagia and food impaction. Diagnosis of EoE requires histologic confirmation of elevated esophageal eosinophils in a symptomatic patient, and only after secondary causes have been excluded. Because EoE is a chronic and progressively fibrostenotic disease, treatment goals include resolution of symptoms, induction and maintenance of disease remission, and prevention and possibly reversal of fibrostenotic complications, while minimizing treatment-related adverse effects and improving quality of life. Treatment strategies include the "3 D's"-drugs, diet, and dilation. Standard drug therapies include proton-pump inhibitors and topical corticosteroids. Dietary therapies include elemental diet, allergy testing-directed elimination diet, and empiric elimination diets. Endoscopic esophageal dilation for EoE strictures can alleviate esophageal symptoms but has no effect on mucosal inflammation. Recent progress in EoE research has made possible evidence-based clinical guidelines. Ongoing pharmacologic trials show promise for novel biologic agents in the treatment of refractory EoE.

Epigenetic Regulation in Early Childhood: A Miniaturized and Validated Method to Assess Histone Acetylation

INTRODUCTION

Chronic inflammatory diseases including allergies and asthma are the result of complex interactions between genes and environmental factors. Epigenetic mechanisms comprise a set of biochemical reactions that regulate gene expression. In order to understand the cause-effect relationship between environmental exposures and disease development, methods capable of assessing epigenetic regulation (also) in large cohorts are needed.

METHODS

For this purpose, we developed and evaluated a miniaturized chromatin immunoprecipitation (ChIP) assay allowing for a cost-effective assessment of histone acetylation of candidate genes in a quantitative fashion. This method was then applied to assess H3 and H4 histone acetylation changes in cord blood (CB) samples from an established cohort of Australian children exposed in the fetal period to either very low or very high levels of maternal folate.

RESULTS

Our ChIP assay was validated for a minimum requirement of 1 × 105 target cells (e.g. CD4+ T cells). Very high levels of maternal folate were significantly associated with increased H3/H4 acetylation at GATA3 and/or IL9 promoter regions in CD4+ T cells in CB.

CONCLUSION

We developed a ChIP method allowing reliable assessment of H3/H4 acetylation using 1 × 105 cells only. Practical application of this assay demonstrated an association between high maternal folate exposure and increased histone acetylation, corresponding to a more transcriptionally permissive chromatin status in the promoter regions of some Th2-related genes.

Do We Know What Causes Eosinophilic Esophagitis? A Mechanistic Update

The mechanisms underlying eosinophilic esophagitis (EoE) have been intensely investigated, and significant advances have been made in understanding the pathogenesis of EoE. EoE is defined as a chronic immune/antigen-mediated disease, characterized clinically by symptoms of esophageal dysfunction and histologically by an esophageal eosinophilic infiltrate. In this paper, we will review the current knowledge of EoE pathophysiology based on both animal and human data and discuss possible etiologic mechanisms from the genetic and environmental perspectives. EoE is a Th2-predominant inflammatory process triggered by allergens. Proinflammatory cytokines and chemokines recruit eosinophils and other effector cells, such as mast cells, into the esophageal epithelium, where they cause direct damage and promote esophageal remodeling. The genetic expression profile of EoE has been described, and several single nucleotide polymorphisms have been identified and associated with EoE. While this genetic contribution is important, it is difficult to postulate that EoE is primarily a genetic disease. Given the rapid epidemiologic changes in the incidence and prevalence of EoE over the past two decades, environmental factors may be the driving force. While it is not known what causes EoE in an individual patient at a specific time, the current hypothesis is that there is a complex interaction between genetic factors and environmental exposures that remains to be elucidated.

Topical corticosteroids do not revert the activated phenotype of eosinophils in eosinophilic esophagitis but decrease surface levels of CD18 resulting in diminished adherence to ICAM-1, ICAM-2, and endothelial cells

Swallowed topical corticosteroids are the standard therapy for eosinophilic esophagitis (EoE) in adults. Eosinophils in the blood of untreated EoE patients have an activated phenotype. Our aim was to determine if corticosteroids restore the phenotype of eosinophils to a healthy phenotype and if certain cell-surface molecules on blood eosinophils correlate with eosinophilic infiltration of the esophagus. Levels of eight surface markers on eosinophils from treated and untreated EoE patients were determined by flow cytometry and analyzed using multivariate methods of pattern recognition. Corticosteroid-treated EoE patients' eosinophils had decreased levels of CD18 compared to both untreated patients and healthy controls, but maintained their activated phenotype. CD18 expression correlated positively with eosinophil numbers in the esophagus and promoted the adherence of eosinophils to ICAM-1, ICAM-2, and to endothelial cells. The diminished expression of CD18 may be one mechanism behind the reduced entry of eosinophils into the esophagus in corticosteroid-treated EoE patients.

Abnormal interactions between perifollicular mast cells and CD8+ T-cells may contribute to the pathogenesis of alopecia areata

Alopecia areata (AA) is a CD8+ T-cell dependent autoimmune disease of the hair follicle (HF) in which the collapse of HF immune privilege (IP) plays a key role. Mast cells (MCs) are crucial immunomodulatory cells implicated in the regulation of T cell-dependent immunity, IP, and hair growth. Therefore, we explored the role of MCs in AA pathogenesis, focusing on MC interactions with CD8+ T-cells in vivo, in both human and mouse skin with AA lesions. Quantitative (immuno-)histomorphometry revealed that the number, degranulation and proliferation of perifollicular MCs are significantly increased in human AA lesions compared to healthy or non-lesional control skin, most prominently in subacute AA. In AA patients, perifollicular MCs showed decreased TGFβ1 and IL-10 but increased tryptase immunoreactivity, suggesting that MCs switch from an immuno-inhibitory to a pro-inflammatory phenotype. This concept was supported by a decreased number of IL-10+ and PD-L1+ MCs, while OX40L+, CD30L+, 4–1BBL+ or ICAM-1+ MCs were increased in AA. Lesional AA-HFs also displayed significantly more peri- and intrafollicular- CD8+ T-cells as well as more physical MC/CD8+ T-cell contacts than healthy or non-lesional human control skin. During the interaction with CD8+ T-cells, AA MCs prominently expressed MHC class I and OX40L, and sometimes 4–1BBL or ICAM-1, suggesting that MC may present autoantigens to CD8+ T-cells and/or co-stimulatory signals. Abnormal MC numbers, activities, and interactions with CD8+ T-cells were also seen in the grafted C3H/HeJ mouse model of AA and in a new humanized mouse model for AA. These phenomenological in vivo data suggest the novel AA pathobiology concept that perifollicular MCs are skewed towards pro-inflammatory activities that facilitate cross-talk with CD8+ T-cells in this disease, thus contributing to triggering HF-IP collapse in AA. If confirmed, MCs and their CD8+ T-cell interactions could become a promising new therapeutic target in the future management of AA.