Conserved γδ T cell selection by BTNL proteins limits progression of human inflammatory bowel disease

Andrographolide and its sulfated metabolite alleviated DSS-induced inflammatory bowel disease through regulating inflammation and immune via MAPK/NLRP3 pathways and the balance of Th17/Treg cells

Inflammatory Bowel Disease (IBD), is a chronic illness characterized by severe abdominal pain, diarrhea, and weight loss, seriously diminishing patients' quality of life. Andrographolide (AND), a natural diterpenoid from Andrographis paniculata, and its sulfated metabolite, andrographolide sodium bisulfite (ASB), have showed potential anti-inflammatory effects. However, their mechanism in IBD remains elusive. This study investigated the impact of AND and its sulfated derivative ASB, on inflammatory responses in IBD. Our findings revealed that AND and ASB significantly reduced disease activity index (DAI) scores and enhanced intestinal barrier function in dextran sodium sulfate (DSS)-induced mice, thereby ameliorating the course of IBD. Furthermore, AND and ASB inhibited both the mitogen-activated protein kinase (MAPK) and NLRP3 pathways to reduce the release of inflammatory cytokines IL-6 and TNF-α. This mechanism was accompanied by a restoration of immune balance through the modulation of T-helper 17 (Th17) and regulatory T (Treg) cells. The ability of AND and ASB to mitigate chronic inflammation and maintain immune equilibrium presented a promising therapeutic approach for IBD management. These findings suggested that AND and ASB might provide novel therapeutic approaches for IBD, thereby warranting further investigation into their clinical efficacy for disease treatment and maintenance of remission.

Lentinan mitigates ulcerative colitis via the IL-22 pathway to repair the compromised mucosal barrier and enhance antimicrobial defense

Ulcerative colitis (UC) involves chronic, complex pathology of the intestinal mucosa. Current treatments are limited in efficacy and associated with adverse effects, highlighting the urgent need for improved therapeutic options. Lentinan (LNT), a polysaccharide drug commonly used in clinical immune modulation therapies, shows potential for UC treatment, though its specific targets and mechanisms remain unclear. In this study, LNT administration effectively mitigated DSS-induced colitis in mice, enhanced mucosal barrier function and antimicrobial defense. Specifically, LNT modulated the balance between tissue-resident and infiltrating macrophages, thereby improving pathogen clearance and enhancing the immunological barrier. Notably, we identified a novel effect of LNT in regulating the macrophage Dectin-1-ILC3 axis to increase IL-22 secretion. This led to the modulation of epithelial O-glycan fucosylation, antimicrobial peptides, and epithelial stem cells, thereby strengthening antimicrobial defenses and the physicochemical barrier. Neutralization with anti-IL-22 antibodies diminished the therapeutic effect of LNT in UC, underscoring the critical role of IL-22 in LNT-mediated treatment. Overall, this study highlights the potential of LNT as a novel therapeutic agent for UC, offering new insights into its molecular mechanisms and clinical application.

A Brief Molecular History of Vγ9Vδ2 TCR-Mediated Phosphoantigen Sensing

Vγ9Vδ2 T-cells are universally present in humans and represent one of the most prevalent TCR reactivities, evolutionarily conserved across diverse mammalian species. They are an innate-like subset featuring a semi-invariant TCR repertoire that drives their well-recognized reactivity to small, non-peptidic phosphoantigens (pAg). Crucially, they can distinguish between highly immunostimulatory microbially derived pAg and much less potent host-derived pAg, with the former effectively acting as a pathogen associated molecular pattern (PAMP) and the Vγ9Vδ2 TCR as a surrogate pattern recognition receptor (PRR). Ample evidence supports important Vγ9Vδ2-mediated contributions to immunity against diverse pathogenic bacteria and parasites, mediated by their potent effector and immunoregulatory functions. The molecular basis of the pAg sensing mechanism underpinning such responses has, however, remained highly mysterious. Despite this, past studies have established that pAg sensing is MHC-independent, extremely fast, exquisitely pAg-sensitive, and dependent upon target cell expression of key BTN-family molecules, notably BTN3A and BTN2A1. Here we contextualize these findings and several recent studies addressing pAg sensing. We integrate these into a single unified theory of pAg sensing interpretable from different perspectives, both intracellular and extracellular, biophysical, and topological. We prioritize critical questions to address in the context of this proposed model. Finally, we suggest the model will provide a molecular template for antigen recognition by other related γδ T-cell subsets.

Uncovering the mysteries of human gamma delta T cells: from origins to novel therapeutics

Gamma delta (γδ) T cells represent a unique and distinct population of lymphocytes that bridge the innate and adaptive immune responses. This functional duality positions them as one of the pivotal elements in the evolution and development of the human body's defense mechanisms. This review aims to provide a comprehensive and in-depth overview of γδ T cells, covering their origins, development, classification, and functional roles in immunology. Special attention is given to their involvement in the pathogenesis of autoimmune and cancer-related diseases-areas that remain subjects of intensive research with many unanswered questions. Additionally, this article explores the therapeutic potential of γδ T cells, which hold promise as a novel approach to treating various difficult-to-manage diseases. The review also presents an analysis of the latest clinical studies utilizing γδ T cells, emphasizing their emerging role in modern medicine. The ultimate goal of this work is to offer a holistic perspective on the current state of research on γδ T cells and their prospective applications in immunotherapy and cancer treatment, highlighting their potential to become a groundbreaking tool in future medical interventions.

Epidemiology, pathogenesis, diagnosis, and treatment of inflammatory bowel disease: Insights from the past two years

ABSTRACT

Inflammatory bowel disease (IBD), including ulcerative colitis and Crohn's disease, is a chronic inflammation of the gastrointestinal tract with unknown etiology. The cause of IBD is widely considered multifactorial, with prevailing hypotheses suggesting that the microbiome and various environmental factors contribute to inappropriate activation of the mucosal immune system in genetically susceptible individuals. Although the incidence of IBD has stabilized in Western countries, it is rapidly increasing in newly industrialized countries, particularly China, making IBD a global disease. Significant changes in multiple biomarkers before IBD diagnosis during the preclinical phase provide opportunities for earlier diagnosis and intervention. Advances in technology have driven the development of telemonitoring tools, such as home-testing kits for fecal calprotectin, serum cytokines, and therapeutic drug concentrations, as well as wearable devices for testing sweat cytokines and heart rate variability. These tools enable real-time disease activity assessment and timely treatment strategy adjustments. A wide range of novel drugs for IBD, including interleukin-23 inhibitors (mirikizumab, risankizumab, and guselkumab) and small-molecule drugs (etrasimod and upadacitinib), have been introduced in the past few years. Despite these advancements, approximately one-third of patients remain primary non-responders to the initial treatment, and half eventually lose response over time. Precision medicine integrating multi-omics data, advanced combination therapy, and complementary approaches, including stem cell transplantation, psychological therapies, neuromodulation, and gut microbiome modulation therapy, may offer solutions to break through the therapeutic ceiling.

Microbiota promote enhanced CD39 expression in γδ intraepithelial lymphocytes through the activation of TCR and IL-15 signaling

Intraepithelial lymphocytes expressing the γδ T cell receptor (γδ IEL) provide continuous surveillance of the intestinal epithelium. We report that mice harboring a microbiota-specific hyperproliferative γδ IEL (γδ HYP ) phenotype also upregulate the expression of the ectonucleotidase CD39, a marker of regulatory γδ T cells. Enhanced TCR and IL-15 signaling correlates with a progression from a naïve-like CD39 neg γδ IEL to a more mature, tissue-adapted CD39 hi IEL population. We found that TCRγδ activation drives CD122-mediated CD39 upregulation on γδ HYP IELs and increased mucosal IL-15 further amplifies CD39 expression in these cells. Further investigation revealed that CD39 induction requires sustained exposure to the γδ HYP -associated microbiota. Moreover, CD39 hi γδ IELs exhibit a reduced capacity to produce pro-inflammatory cytokine, which may explain the lack of histopathology in γδ HYP mice. Overall, our study identifies a previously unappreciated mechanism by which an altered microbiota amplifies CD39 expression on γδ HYP IELs, leading to the expansion of γδ IELs with regulatory potential.

Dysregulation of γδ intraepithelial lymphocytes precedes Crohn's disease-like ileitis

Intraepithelial lymphocytes expressing the γδ T cell receptor (γδ IELs) provide immunosurveillance of the intestinal barrier but are reduced in patients with active Crohn's disease (CD). Here, we report an underappreciated role for γδ IELs in maintaining immunological tolerance during the onset and progression of CD-like ileitis using TNFΔARE/+ mice. We found that TNF-induced down-regulation of epithelial hepatocyte nuclear factor 4-gamma/butyrophilin is followed by a loss of ileal Vγ7 IELs and impaired barrier surveillance before the histological onset of disease. A reduction of immunoregulatory CD39+ γδ IELs coincided with the influx of immature, peripheral CD39neg γδ T cells into the epithelium, leading to an expansion of induced IELs, whereas an earlier depletion of γδ IELs correlated with accelerated onset of ileal inflammation. Our findings identify multiple layers of γδ IEL dysregulation before ileitis development, indicating that the loss of steady-state immunoregulatory γδ IELs may contribute to the initiation of ileal CD.

Heterozygous BTNL8 variants in individuals with multisystem inflammatory syndrome in children (MIS-C)

Multisystem inflammatory syndrome in children (MIS-C) is a rare condition following SARS-CoV-2 infection associated with intestinal manifestations. Genetic predisposition, including inborn errors of the OAS-RNAseL pathway, has been reported. We sequenced 154 MIS-C patients and utilized a novel statistical framework of gene burden analysis, "burdenMC," which identified an enrichment for rare predicted-deleterious variants in BTNL8 (OR = 4.2, 95% CI: 3.5-5.3, P < 10-6). BTNL8 encodes an intestinal epithelial regulator of Vγ4+γδ T cells implicated in regulating gut homeostasis. Enrichment was exclusive to MIS-C, being absent in patients with COVID-19 or bacterial disease. Using an available functional test for BTNL8, rare variants from a larger cohort of MIS-C patients (n = 835) were tested which identified eight variants in 18 patients (2.2%) with impaired engagement of Vγ4+γδ T cells. Most of these variants were in the B30.2 domain of BTNL8 implicated in sensing epithelial cell status. These findings were associated with altered intestinal permeability, suggesting a possible link between disrupted gut homeostasis and MIS-C-associated enteropathy triggered by SARS-CoV-2.

Research progress on V delta 1+ T cells and their effect on pathogen infection

The ongoing high occurrence of harmful infectious diseases significantly threatens human health. Existing methods used to control such diseases primarily involve targeting the pathogens, usually neglecting the vital role of host factors in disease advancement. Gamma delta (γδ) T cells act as a bridge between innate and adaptive immunity, playing a crucial role in combating pathogen invasion. Among these γδT cell subsets, which are categorized based on T cell receptor delta variable expression patterns, V delta (δ) 1+ T cells possess unique recognition abilities and regulatory characteristics and actively engage in various immune responses. The differentiation, development, and immune reactivity of Vδ1+ T cells are closely associated with the initial and progressive stages of infectious diseases. This article provides an overview of the classification, distribution, differentiation, and development of Vδ1+ T cells and their mechanisms in combating pathogenic infections, offering new insights for disease diagnosis and treatment.

Cancer immunotherapy by γδ T cells

The premise of cancer immunotherapy is that cancers are specifically visible to an immune system tolerized to healthy self. The promise of cancer immunotherapy is that immune effector mechanisms and immunological memory can jointly eradicate cancers and inoperable metastases and de facto vaccinate against recurrence. For some patients with hitherto incurable diseases, including metastatic melanoma, this promise is being realized by game-changing immunotherapies based on αβ T cells. Today's challenges are to bring benefit to greater numbers of patients of diverse ethnicities, target more cancer types, and achieve a cure while incurring fewer adverse events. In meeting those challenges, specific benefits may be offered by γδ T cells, which compose a second T cell lineage with distinct recognition capabilities and functional traits that bridge innate and adaptive immunity. γδ T cell-based clinical trials, including off-the-shelf adoptive cell therapy and agonist antibodies, are yielding promising results, although identifiable problems remain. In addressing those problems, we advocate that immunotherapies be guided by the distinctive biology of γδ T cells, as elucidated by ongoing research.

Illuminating the impact of γδ T cells in man and mice in spondylarthritides

Spondylarthritides (SpA) are a group of autoinflammatory diseases affecting the spine, peripheral joints, and entheses, including axial spondyloarthritis (axSpA) and psoriatic arthritis. AxSpA has a multifactorial etiology that involves genetic predispositions, such as HLA-B27 and IL-23R. Although HLA-B27 is strongly associated with axSpA, its role remains unclear. GWAS studies have demonstrated that genetic polymorphisms related to the IL-23 pathway occur throughout the spectrum of SpA, including but not limited to axSpA and PsA. IL-23 promotes the production of IL-17, which drives inflammation and tissue damage. This pathway contributes not only to peripheral enthesitis but also to spinal inflammation. γδ T cells in axSpA express IL-23R and RORγt, crucial for their activation, although specific pathogenic cells and factors remain elusive. Despite drug efficacy in PsA, IL-23R inhibition is ineffective in axSpA. Murine models provide valuable insights into the intricate cellular and molecular interactions that contribute to the development and progression of SpA. Those models are useful tools to elucidate the dynamics of γδ T cell involvement, offering insights into disease mechanisms and potential therapeutic targets. This review aims to illuminate the complex interplay between IL-23 and γδ T cells in SpA pathogenesis, emphasizing their roles in chronic inflammation, tissue damage, and disease heterogeneity.

Human organoids with an autologous tissue-resident immune compartment

The intimate relationship between the epithelium and immune system is crucial for maintaining tissue homeostasis, with perturbations therein linked to autoimmune disease and cancer1-3. Whereas stem cell-derived organoids are powerful models of epithelial function4, they lack tissue-resident immune cells that are essential for capturing organ-level processes. We describe human intestinal immuno-organoids (IIOs), formed through self-organization of epithelial organoids and autologous tissue-resident memory T (TRM) cells, a portion of which integrate within the epithelium and continuously survey the barrier. TRM cell migration and interaction with epithelial cells was orchestrated by TRM cell-enriched transcriptomic programs governing cell motility and adhesion. We combined IIOs and single-cell transcriptomics to investigate intestinal inflammation triggered by cancer-targeting biologics in patients. Inflammation was associated with the emergence of an activated population of CD8+ T cells that progressively acquired intraepithelial and cytotoxic features. The appearance of this effector population was preceded and potentiated by a T helper-1-like CD4+ population, which initially produced cytokines and subsequently became cytotoxic itself. As a system amenable to direct perturbation, IIOs allowed us to identify the Rho pathway as a new target for mitigation of immunotherapy-associated intestinal inflammation. Given that they recapitulate both the phenotypic outcomes and underlying interlineage immune interactions, IIOs can be used to study tissue-resident immune responses in the context of tumorigenesis and infectious and autoimmune diseases.

Navigating commensal dysbiosis: Gastrointestinal host-pathogen interplay orchestrating opportunistic infections

The gut commensals, which are usually symbiotic or non-harmful bacteria that live in the gastrointestinal tract, have a positive impact on the health of the host. This review, however, specifically discuss distinct conditions where commensals aid in the development of pathogenic opportunistic infections. We discuss that the categorization of gut bacteria as either pathogens or non-pathogens depends on certain circumstances, which are significantly affected by the tissue microenvironment and the dynamic host-microbe interaction. Under favorable circumstances, commensals have the ability to transform into opportunistic pathobionts by undergoing overgrowth. These conditions include changes in the host's physiology, simultaneous infection with other pathogens, effective utilization of nutrients, interactions between different species of bacteria, the formation of protective biofilms, genetic mutations that enhance pathogenicity, acquisition of genes associated with virulence, and the ability to avoid the host's immune response. These processes allow commensals to both initiate infections themselves and aid other pathogens in populating the host. This review highlights the need of having a detailed and sophisticated knowledge of the two-sided nature of gut commensals. Although commensals mostly promote health, they may also become harmful in certain changes in the environment or the body's functioning. This highlights the need of acknowledging the intricate equilibrium in interactions between hosts and microbes, which is crucial for preserving intestinal homeostasis and averting diseases. Finally, we also emphasize the further need of research to better understand and anticipate the behavior of gut commensals in different situations, since they play a crucial and varied role in human health and disease.

The Evolving Portrait of γδ TCR Recognition Determinants

In αβ T cells, immunosurveillance is enabled by the αβ TCR, which corecognizes peptide, lipid, or small-molecule Ags presented by MHC- and MHC class I-like Ag-presenting molecules, respectively. Although αβ TCRs vary in their Ag recognition modes, in general they corecognize the presented Ag and the Ag-presenting molecule and do so in an invariable "end-to-end" manner. Quite distinctly, γδ T cells, by way of their γδ TCR, can recognize ligands that extend beyond the confines of MHC- and MHC class I-like restrictions. From structural studies, it is now becoming apparent that γδ TCR recognition modes can break the corecognition paradigm and deviate markedly from the end-to-end docking mechanisms of αβ TCR counterparts. This brief review highlights the emerging portrait of how γδ TCRs can recognize diverse epitopes of their Ags in a manner reminiscent to how Abs recognize Ags.

From immunomodulation to therapeutic prospects: Unveiling the biology of butyrophilins in cancer

Butyrophilin (BTN) proteins are a type of membrane protein that belongs to the Ig superfamily. They exhibit a high degree of structural similarity to molecules in the B7 family. They fulfill a complex function in regulating immune responses, including immunomodulatory roles, as they influence γδ T cells. The biology of BTN molecules indicates that they are capable of inhibiting the immune system's ability to detect antigens within tumors. A dynamic association between BTN molecules and cellular surfaces is also recognized in specific contexts, influencing their biology. Notably, the dynamism of BTN3A1 is associated with the immunosuppression of T cells or the activation of Vγ9Vδ2 T cells. Cancer immunotherapy relies heavily on T cells to modulate immune function within the intricate interaction of the tumor microenvironment (TME). A significant interaction between the TME and antitumor immunity involves the presence of BTN, which should be taken into account when developing immunotherapy. This review explores potential therapeutic applications of BTN molecules, based on the current understanding of their biology.

Challenges in IBD Research 2024: Precision Medicine

Precision medicine is part of 5 focus areas of the Challenges in IBD Research 2024 research document, which also includes preclinical human IBD mechanisms, environmental triggers, novel technologies, and pragmatic clinical research. Building on Challenges in IBD Research 2019, the current Challenges aims to provide a comprehensive overview of current gaps in inflammatory bowel diseases (IBDs) research and deliver actionable approaches to address them with a focus on how these gaps can lead to advancements in interception, remission, and restoration for these diseases. The document is the result of multidisciplinary input from scientists, clinicians, patients, and funders, and represents a valuable resource for patient-centric research prioritization. In particular, the precision medicine section is focused on the main research gaps in elucidating how to bring the best care to the individual patient in IBD. Research gaps were identified in biomarker discovery and validation for predicting disease progression and choosing the most appropriate treatment for each patient. Other gaps were identified in making the best use of existing patient biosamples and clinical data, developing new technologies to analyze large datasets, and overcoming regulatory and payer hurdles to enable clinical use of biomarkers. To address these gaps, the Workgroup suggests focusing on thoroughly validating existing candidate biomarkers, using best-in-class data generation and analysis tools, and establishing cross-disciplinary teams to tackle regulatory hurdles as early as possible. Altogether, the precision medicine group recognizes the importance of bringing basic scientific biomarker discovery and translating it into the clinic to help improve the lives of IBD patients.

Therapeutic induction of antigen-specific immune tolerance

The development of therapeutic approaches for the induction of robust, long-lasting and antigen-specific immune tolerance remains an important unmet clinical need for the management of autoimmunity, allergy, organ transplantation and gene therapy. Recent breakthroughs in our understanding of immune tolerance mechanisms have opened new research avenues and therapeutic opportunities in this area. Here, we review mechanisms of immune tolerance and novel methods for its therapeutic induction.

γδ T cell antigen receptor polyspecificity enables T cell responses to a broad range of immune challenges

γδ T cells are essential for immune defense and modulating physiological processes. While they have the potential to recognize large numbers of antigens through somatic gene rearrangement, the antigens which trigger most γδ T cell response remain unidentified, and the role of antigen recognition in γδ T cell function is contentious. Here, we show that some γδ T cell receptors (TCRs) exhibit polyspecificity, recognizing multiple ligands of diverse molecular nature. These ligands include haptens, metabolites, neurotransmitters, posttranslational modifications, as well as peptides and proteins of microbial and host origin. Polyspecific γδ T cells are enriched among activated cells in naive mice and the responding population in infection. They express diverse TCR sequences, have different functional potentials, and include the innate-like γδ T cells, such as the major IL-17 responders in various pathological/physiological conditions. We demonstrate that encountering their antigenic microbiome metabolite maintains their homeostasis and functional response, indicating that their ability to recognize multiple ligands is essential for their function. Human γδ T cells with similar polyspecificity also respond to various immune challenges. This study demonstrates that polyspecificity is a prevalent feature of γδ T cell antigen recognition, which enables rapid and robust T cell responses to a wide range of challenges, highlighting a unique function of γδ T cells.

Colonic mucosal associated invariant T cells in Crohn's disease have a diverse and non-public T cell receptor beta chain repertoire

OBJECTIVES

Mucosal-Associated Invariant T (MAIT) cells are T cells with a semi-invariant T cell receptor (TCR), recognizing riboflavin precursors presented by a non-polymorphic MR1 molecule. As these precursors are produced by the gut microbiome, we characterized the frequency, phenotype and clonality of MAIT cells in human colons with and without Crohn's disease (CD).

METHODS

The transcriptome of MAIT cells sorted from blood and intestinal lamina propria cells from colectomy recipients were compared with other CD8+ T cells. Colon biopsies from an additional ten CD patients and ten healthy controls (HC) were analyzed by flow cytometry. TCR genes were sequenced from individual MAIT cells from these biopsies and compared with those of MAIT cells from autologous blood.

RESULTS

MAIT cells in the blood and colon showed a transcriptome distinct from other CD8 T cells, with more expression of the IL-23 receptor. MAIT cells were enriched in the colons of CD patients, with less NKG2D in inflamed versus uninflamed segments. Regardless of disease, most MAIT cells expressed integrin α4β7 in the colon but not in the blood, where they were enriched for α4β7 expression. TCR sequencing revealed heterogeneity in the colon and blood, with few public sequences associated with cohorts.

CONCLUSION

MAIT cells are enriched in the colons of CD patients and disproportionately express molecules (IL-23R, integrin α4β7) targeted by CD therapeutics, to suggest a pathogenic role for them in CD. Public TCR sequences were neither common nor sufficiently restricted to a cohort to suggest protective or pathogenic antigen-specificities.

Protection from inflammatory bowel disease

Immunomodulation of lymphocytes by intestinal epithelial cells could lead to new therapies.