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Here, we explore the relationship between dietary fibers, colonic epithelium major histocompatibility complex class II (MHC-II) expression, and immune cell interactions in regulating susceptibility to Clostridioides difficile infection (CDI). We find that a low-fiber diet increases MHC-II expression in the colonic epithelium, which, in turn, worsens CDI by promoting the development of pathogenic CD4 + intraepithelial lymphocytes (IELs). The influence of dietary fibers on MHC-II expression is mediated by its metabolic product, acetate, and its receptor, free fatty acid receptor 2 (FFAR2). While acetate activation of FFAR2 on epithelial cells helps resist CDI, it does not directly regulate MHC-II expression. Instead, MHC-II is regulated by FFAR2 in type 3 innate lymphoid cells (ILC3s). Acetate enhances interleukin-22 (IL-22) production by ILC3s, which then suppresses MHC-II expression on the colonic epithelium. In conclusion, a low-fiber diet reduces acetate-induced IL-22 production by ILC3s, leading to increased MHC-II on the colonic epithelium. This change affects recovery from CDI by expanding the population of pathogenic CD4 + IELs., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2025 The Authors. Published by Elsevier Inc. All rights reserved.)

The upper oesophagogastrointestinal (UEGI) tract histology, intestinal morphometry and lymphocyte subpopulations of healthy people is scarcely known. In research studies of inflammation involving the UEGI tract, there is a lack of adequate healthy controls. Aims: To evaluate the histology of the UEGI tract and the duodenal lymphocyte subpopulations of healthy volunteers and patients with gastroesophageal reflux disease (GERD), the latter to assess if it could replace healthy subjects. Healthy individuals were excluded if they had symptoms, comorbidities, pregnancy, toxics, medications or abnormal blood analysis. Subjects in both groups with abnormal duodenal intraepithelial lymphocyte (IEL) counts were also excluded. A total of 280 subjects were assessed, and 37 were included (23 healthy and 14 with GERD). The GERD group showed a higher IEL count (median [IQR]: 19.5 [17-22]), than healthy group: (15 [12-18]), p = 0.004. Eosinophils, mast cells and intestinal morphometry were similar in both groups. In the lamina propria, CD4+ T cells decreased ( p = 0.008), and CD8+ T cells increased ( p = 0.014). The total innate lymphoid cells (ILC) and CD3- cells decreased ( p = 0.007) in GERD group compared to healthy controls. At the intraepithelial level, NKT cells increased ( p = 0.036) and ILC3 decreased ( p = 0.049) in the GERD group. This is the first study to comprehensively map the histology, morphometry and duodenal subpopulations of healthy volunteers to help define a "gold standard" of normality. The differences found between both groups suggest that, whenever possible, healthy subjects should be included in research studies. Alternatively, we can consider a well-defined homogenous group with GERD to serve as the control group.

Purpose: Conjunctival-resident γδT cells, the predominant ocular source of interleukin-17A (IL-17A), play crucial roles in dry eye disease (DED) pathogenesis. The upstream regulators of these cells are unknown. This study evaluated the role of conjunctival IL-23 expression in mediating γδT cell generation and elucidated its contribution to dry eye inflammatory responses., Methods: Single-cell RNA sequencing (scRNA-seq) was used to identify and quantify conjunctival mRNA molecules in γδT cells in mice. The IL-23 level increased in wild-type (WT) and decreased in γδT-deficient (TCRδ-/-) mice after dry eye was induced via an intelligently controlled environmental system (ICES). Flow cytometry and transcriptome sequencing were used to investigate the impact of the changes in IL-23 expression on human γδT cells., Results: The expression of the IL-23 receptor (IL-23R) was greater in γδT cells than in other conjunctival cell types, such as CD4+ T cells, CD8+ T cells and epithelial cells. An increase in IL-23 led to an increase in γδT cell density, which was proportional to dry eye severity. However, in the TCRδ-/- mice, the upregulation of IL-23 failed to increase the expression level of IL-17A and the severity of dry eye. Furthermore, increases in the expression of IL-23 and the number of γδT cells were evident in the ocular surface cells of patients who developed visual display terminal syndrome., Conclusions: An increase in conjunctival IL-23 expression contributes to the induction of the DED inflammatory response through interactions with its cognate receptor on γδT cells and the promotion of their proliferation. The findings of this study suggest that the suppression of IL-17A through the blockade of IL-23R activation may be a viable target for improving the management of inflammation in DED patients.

Aims: Diagnosis of coeliac disease (CD) with mild mucosal changes is difficult for all parties involved. We aimed to determine the power of T cell receptor (TCR)γδ + intra-epithelial lymphocytes (IELs) in discriminating CD from other causes of intra-epithelial lymphocytosis using a new monoclonal antibody., Methods: A total of 167 cases categorised as coeliac (117 untreated CD, classified according to Marsh, updated by Ensari, including 29 type 1, 29 type 2, 39 type 3 and 20 treated CD), and non-coeliac groups (24 controls and 26 non-coeliac IELosis) based on clinical, serological and histological data were studied for IEL counts enumerated per 100 enterocytes using haematoxylin and eosin, CD3, TCR δ-stains., Results: TCRγδ + IELs were significantly higher in CD (24.83 ± 16.13) compared to non-CD (6.72 ± 6.32) and were correlated with the degree of mucosal damage. Both γδ + IEL count and ratio showed higher performance in differentiating untreated coeliacs from controls, with a sensitivity of 83.76; 85.57 and specificity of 95.83; 79.17, respectively. TCRγδ + IEL counts distinguished type 1 CD (20.41 ± 13.57) from non-coeliac IELosis (9.42 ± 7.28) (p = 0.025). Discriminant analysis revealed that villus/crypt ratio, γδ + and CD3 + IEL counts, γδ + /CD3 + IEL ratio, IEL distribution pattern were potent discriminants and correctly classified 82.3% of cases while the algorithm accurately diagnosed 93.4% of cases., Conclusions: The new antibody detecting γδ + IELs in FFPE sections revealed thresholds of 10.5 for γδ + IELs and 14% for γδ + /CD3 + IEL ratio which distinguished coeliacs from non-coeliacs with high sensitivity and specificity, particularly in cases with normal villus/crypt axis including type 1 CD, non-CD IELosis and controls. A 'coeliac algorithm' based on γδ + IELs is proposed with the hope that it will be used in the histopathological diagnostic approach by the pathology community., (© 2024 The Author(s). Histopathology published by John Wiley & Sons Ltd.)

Intraepithelial type 1 innate lymphoid cells (ieILC1s) are tissue-resident lymphocytes in the microenvironment of head and neck squamous cell carcinoma. Here, we evaluate how these cells influence T-cell trafficking to tumors. We generated cytotoxic ieILC1-like cells from natural killer (NK) cells in vitro. Using an in vivo tumor model, we show that intratumoral ieILC1-like NK cells induce greater T cell trafficking into the tumor. Co-culture of ieILC1-like NK cells with the tumor cells resulted in elevated CXCL10 in the supernatant. Flow cytometry demonstrated that ieILC1-like NK cells produce robust amounts of IFNy, a known CXCL10 inducer, while CXCL10 was produced by tumor cells. These results indicate ieILC1-like NK cells induce tumor production of CXCL10, a proinflammatory chemokine that promotes T cell infiltration into the TME. The role of ieILC1-like NK cells in modulating clinical responses to immune checkpoint blockade warrants investigation., (© 2024 American Academy of Otolaryngology–Head and Neck Surgery Foundation.)

Cetaceans exhibit remarkable wound healing capabilities. However, the specific immune mechanisms underlying this process, particularly the role of γδ T cells, remains largely unexplored. In ruminants, pigs, and camelids, which are members of the order Cetartiodactyla alongside cetaceans, γδ T cells express a unique receptor called workshop cluster 1 (WC1). Despite cetaceans also belonging to this order, the presence of WC1 in their γδ T cells has not yet been reported. This study aims to investigate the distribution and potential function of γδ T cells in cetacean skin during homeostasis and wound healing. Using immunofluorescence and immunohistochemical staining, we identified γδ TCR + and WC1 + cells in dolphin skin for the first time. These cells are predominantly located in the dermis and blubber, with an increased presence in healing wounds, suggesting their involvement in wound healing rather than pathogen defense. Furthermore, our findings revealed that γδ TCR + cells constitute a small fraction of CD3 + MHCII + cells in dolphin skin, indicating their intricate role in cetacean immunology. Additionally, the appearance of WC1 + cells in cetaceans highlights unique immunological features within Cetartiodactyla. Comparative analysis demonstrates that γδ T cells in dolphins exhibit distinctive morphological and distributional characteristics compared to those in humans, mice, and ruminants, implying species-specific adaptations. These insights contribute to a deeper understanding of cetacean immunology and underscore the potential evolutionary adaptations that support their exceptional wound healing capabilities. Future research on the genomic and functional aspects of γδ T cells in cetaceans is essential to further elucidate their roles in immune response and wound healing., (Copyright © 2025 Elsevier Ltd. All rights reserved.)

New HIV vaccine approaches are focused on eliciting broadly neutralizing antibodies. We characterized early gamma-delta (γδ) T cell responses starting from pre-acquisition and during acute HIV infection (AHI) in participants previously characterized for neutralization breadth development. We found significant differences in γδ T cell surface marker expression in participants that developed neutralization breadth compared to those that did not. Activation of γδ T cells occurred within the first weeks of HIV acquisition and associated with viral load. Expression of CD16 on Vδ1 T cells and CD57 on Vδ2 T cells were found to be significantly higher in broad neutralizers during AHI, and associated with the development of neutralization breadth years later. In addition, the levels of CD16 on Vδ1 T cells was associated with early production of founder virus Env-specific IgM. Thus, γδ T cells may promote development of neutralization breadth, which has implications for HIV vaccine strategies., Competing Interests: The authors declare no competing interests., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

Background: The small intestine harbors a rich array of intestinal intraepithelial lymphocytes (IELs) that interact with structural cells to collectively sustain gut immune homeostasis. Dysregulation of gut immune homeostasis was implicated in the pathogenesis of multiple autoimmune diseases, however, whether this homeostasis is disrupted in a lupus autoimmune background remains unclear., Methods: We performed single-cell RNA sequencing (scRNA-seq) analyses to elucidate immune and structural milieu in the intestinal epithelium of MRL/Lpr lupus mice (Lpr mice) and MRL/Mpj control mice (Mpj mice). Comprehensive analyses including unsupervised clustering, trajectories, and cellular communication were performed. The primary findings from scRNA-seq were further validated by quantitative polymerase chain reaction (qPCR), flow cytometry, and in vivo experiments including selenium supplementation., Results: We observed a significant reduction in CD8αα + IELs, accompanied by a marked increase in CD8αβ + IELs in Lpr mice. Additionally, subsets of CD8 + IELs exhibiting significantly enhanced effector functions were found to be markedly enriched in Lpr mice. Intercellular communication patterns within intestinal epithelial immune and structural cells were found to be specifically altered in Lpr mice. Moreover, scRNA-seq revealed significantly decreased intestinal TCRγδ T cells (γδT) associated with reduced aryl-hydrocarbon receptor repressor (AHRR) expression and subsequent oxidative stress and ferroptosis in Lpr mice. Antioxidant selenium effectively reversed the loss of γδT in Lpr mice, improved the gut barrier, and alleviated lupus symptoms., Conclusions: Our high-resolution single-cell atlas enhances the understanding of the immune and structural milieu of intestinal epithelium in lupus and provides new insights into lupus pathogenesis mediated by intestinal immune dysregulation., Competing Interests: Declarations. Ethics approval and consent to participate: All experiments adhered to the animal ethical and care guidelines established by the Institute of Dermatology, Chinese Academy of Medical Sciences (2023-DW-031). The research did not use any materials of human subjects. Consent for publication: Not applicable. Competing interests: The authors declare that they have no competing interests., (© 2025. The Author(s).)

Background: γδT cells have been implicated in the pathogenesis of autoimmune diseases. The study aims to investigate the abundance of γδT cells in MRL/lpr mice., Methods: MRL/lpr mice were used as lupus models, while C3H/HeJ mice served as normal controls. The abundance of γδT cells in different organs was examined by flow cytometry. Plasma double-stranded DNA antibody levels, blood urea nitrogen, creatinine, and urinary protein levels were measured. Renal histopathology was observed via H&E staining. The correlations between the abundance of γδT cells and lupus manifestations were analyzed., Results: Compared with C3H/HeJ mice, the number of γδT cells and Vγ6 + γδT cell subset in the peripheral blood of MRL/lpr mice was significantly reduced. However, in the kidney, the number of γδT cells and Vγ6 + γδT cell subset was significantly increased. Additionally, the number of Vγ6 + γδT cells in the kidney was positively correlated with the urinary protein level. The number of IFN-γ + Vγ6 + γδT cells in the kidney was positively correlated with urinary protein level., Conclusion: In MRL/lpr mice, it is likely that peripheral γδT cells, especially the Vγ6 subset, infiltrate the kidney and secrete IFN-γ, which contributes to the development of lupus nephritis., (© 2024 Asia Pacific League of Associations for Rheumatology and John Wiley & Sons Australia, Ltd.)

Human gammadelta (γδ) T cells not only infiltrate or reside in healthy tissues but also enter solid cancers. A large body of evidence suggests that γδ T cells can exert potent anti-tumor effects, although conflicting or unfavorable effects have been reported in some cancer entities. Infiltration patterns are key to understanding the complexity of the tumor microenvironment (TME) and its interplay with γδ T cells. The limited data available describe different γδ T cell subsets that are located in different areas around and within tumors. Tumor-infiltrating γδ lymphocytes (γδ TIL) exert cytotoxicity, for example, via the CD95- or TRAIL-axis, produce high amounts of granzymes, and after their activation, tumor necrosis factor (TNF)-α or IFN-γ and express immune checkpoint receptors. Under certain conditions, γδ T cell subsets can express low amounts of IL-17 and seem to contribute to immune regulation/suppression. A polarization of γδ T cells can be influenced by the TME. Inflammatory cytokines, growth factors, or tumor promoters can suppress γδ T cell functionality or even push them toward tumor promotion. To avoid this and to exploit the unique features of γδ T cell-mediated anti-cancer and immune-orchestrating capabilities in future immune therapy approaches, a growing body of preclinical but also clinical studies can be observed., (© 2024 The Author(s). European Journal of Immunology published by Wiley‐VCH GmbH.)

Background: Gamma-delta (γδ) T cells are a distinct subset of T cells with a receptor composed of γ and δ chains. Their ability to directly recognize stress-induced molecules and non-peptide antigens expressed by cancer cells, along with their capacity to produce cytokines and interact with other immune cells, makes them potentially significant contributors to immune-based treatments., Objective: To investigate the presence and frequency of Tγδ cells in tumor-draining lymph nodes of patients with bladder cancer (BC), and to assess their association with prognostic parameters., Methods: Forty-nine fresh tumor-draining lymph nodes from untreated patients with BC were minced to obtain single cells. The cells were surface-stained with anti-CD3, anti-TCRγδ, and anti-HLA-DR antibodies, then acquired on a four-color FACSCalibur flow cytometer, and analyzed by FlowJo software., Results: On average, 2.07% ± 1.99% of CD3+ lymphocytes in regional nodes of BC exhibited a γδ T phenotype. A considerable percentage of these cells (37.90% ± 24.42%) expressed HLA-DR. Statistical analysis revealed that while the frequency of γδ T cells showed no variation among patients with different prognoses, the HLA-DR+ subset was higher in T4 patients than in T2 patients (p=0.031). These cells also tended to be increased in stage III compared to stage II (p=0.077)., Conclusion: The data collectively indicated an association of HLA-DR expressing γδ T cells with prognostic factors related to tumor progression (higher T-group and stage), suggesting their potential involvement in disease progression. However, future research, including longitudinal studies with larger cohorts, needs to validate these findings and elucidate the functional roles of γδ T cells in the immune response against BC.

Aging is associated with increased tumor metastasis and poor prognosis. However, how an aging immune system contributes to the process is unclear. Here, single-cell RNA sequencing reveals that in male mice, aging shifts the lung immune microenvironment towards a premetastatic niche, characterized by an increased proportion of IL-17-expressing γδT (γδ17) and neutrophils. Mechanistically, age-dependent downregulation of the immune trafficking receptor S1pr1 drives the expansion of γδ17. Compared to young mice, expanded γδ17 recruit tumor-promoting neutrophils with lower expression levels of CD62L and higher levels of C-kit and CXCR4. These neutrophils suppress the stemness and tumor-killing functions of CD8+ T cells in aged male mice. Accordingly, antibody-mediated depletion of γδT or neutrophils reduces tumor metastatic foci in aged animals, and the administration of the senolytic agent procyanidin C1 reverses the observed immune-mediated, tumor-promoting effects of aging. Thus, we uncover a γδ17-Neutrophil-CD8 axis that promotes aging-driven tumor metastasis in male mice and provides potential insights for managing metastatic tumors., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

During thymic development, most γδ T cells acquire innate-like characteristics that are critical for their function in tumor surveillance, infectious disease, and tissue repair. The mechanisms, however, that regulate γδ T cell developmental programming remain unclear. Recently, we demonstrated that the SLAM/SAP signaling pathway regulates the development and function of multiple innate-like γδ T cell subsets. Here, we used a single-cell proteogenomics approach to identify SAP-dependent developmental checkpoints and to define the SAP-dependent γδ TCR repertoire in mice. SAP deficiency resulted in both a significant loss of an immature Gzma + Blk + Etv5 + Tox2 + γδT17 precursor population and a significant increase in Cd4 + Cd8 + Rorc + Ptcra + Rag1 + thymic γδ T cells. SAP-dependent diversion of embryonic day 17 thymic γδ T cell clonotypes into the αβ T cell developmental pathway was associated with a decreased frequency of mature clonotypes in neonatal thymus, and an altered γδ TCR repertoire in the periphery. Finally, we identify TRGV4/TRAV13-4(DV7)-expressing T cells as a novel, SAP-dependent Vγ4 γδT1 subset. Together, the data support a model in which SAP-dependent γδ/αβ T cell lineage commitment regulates γδ T cell developmental programming and shapes the γδ TCR repertoire., Competing Interests: SM, BH, KH, EA, RS, OD, KH, DG, JR, NS, DM, JB No competing interests declared, (© 2024, Mistri et al.)

Background: Intraepithelial lymphocytes are the first line of defence of the human intestinal immune system. Besides, their composition is altered on patients with coeliac disease (CD), so they are considered as biomarkers with utility on their diagnose and/or monitoring. Our aim is to address their variability through the human gastrointestinal tract in health and characterized them in further depth in the coeliac duodenum., Methods: Intraepithelial lymphocytes were isolated from human gastric, duodenal, ileal and colonic biopsies, then stained with specific antibodies and acquired by flow cytometry., Results: Our results confirmed that the profile of Intraepithelial lymphocytes change through the length of the human gastrointestinal tract. Besides and given the central role that Interleukin-15 (IL-15) elicits on CD pathogenesis; we also assessed the expression of its receptor revealing that there was virtually no functional IL-15 receptor on duodenal Intraepithelial lymphocytes. Nevertheless and contrary to our expectations, the active IL-15 receptor was not increased either on Intraepithelial lymphocytes from CD patients., Conclusions: IL-15 might require additional stimulus to activate intraepithelial lymphocytes. These findings may provide novel tools to aid on a CD diagnosis and/or monitoring, at the time that provide the bases to perform functional studies in order of getting a deeper insight in the specific function that Intraepithelial lymphocytes elicit on CD pathogenesis., (© 2024 The Author(s). European Journal of Clinical Investigation published by John Wiley & Sons Ltd on behalf of Stichting European Society for Clinical Investigation Journal Foundation.)

Introduction: Colorectal cancer (CRC) is the third-most common cancer diagnosed worldwide, with 1.85 million new cases per year. While mortality has significantly decreased due to preventive colonoscopy, only 5% of polyps identified progress to cancer. Studies have found that immunological alterations in other solid tumor microenvironments are associated with worse prognoses., Methods: We applied an immunogenomics approach to assess adaptive immune receptor gene expression changes that were associated with development of adenocarcinoma, utilizing 79 samples that represented normal, tubular, villous, and tumor colorectal tissue for 32 patients., Results: Results indicated that the number of productive TRD and TRG recombination reads, representing gamma-delta (γδ) T-cells, significantly decreased with progression from normal to tumor tissue. A further assessment of two independent CRC datasets was consistent with a decrease in TRD recombination reads with progression to CRC. Further, we identified three physicochemical parameters for immunoglobulin, complementarity determining region-3 (CDR3) amino acids associated with progression from normal to tumor tissue., Conclusions: Overall, this study points towards a need for further investigation of γδ T-cells in relation to CRC development; and indicates immunoglobulin CDR3 physicochemical features as potential CRC biomarkers., Competing Interests: Disclosure The authors declared that they have no conflict of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Gamma delta T cells play a crucial role in anti-tumor immunity due to their cytotoxic properties. However, the role and extent of γδ T cells in production of pro-tumorigenic interleukin-17 (IL-17) within the tumor microenvironment of colorectal cancer (CRC) remains controversial. In this study, we re-analyzed nine published human CRC whole-tissue single-cell RNA sequencing datasets, identifying 18,483 γδ T cells out of 951,785 total cells, in the neoplastic or adjacent normal tissue of 165 human CRC patients. Our results confirm that tumor-infiltrating γδ T cells exhibit high cytotoxicity-related transcription in both tumor and adjacent normal tissues, but critically, none of the γδ T cell clusters showed IL-17 production potential. We also identified various γδ T cell subsets, including poised effector-like T cells, tissue-resident memory T cells, progenitor exhausted-like T cells, and exhausted T cells, and noted an increased expression of cytotoxic molecules in tumor-infiltrating γδ T cells compared to their normal area counterparts. We proposed anti-tumor γδ T effector cells may arise from tissue-resident progenitor cells based on the trajectory analysis. Our work demonstrates that γδ T cells in CRC primarily function as cytotoxic effector cells rather than IL-17 producers, mitigating the concerns about their potential pro-tumorigenic roles in CRC, highlighting the importance of accurately characterizing these cells for cancer immunotherapy research and the unneglectable cross-species discrepancy between the mouse and human immune system in the study of cancer immunology., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024. Published by Elsevier Inc.)

Colorectal cancer (CRC) ranks as the third most prevalent malignancy and second leading cause of cancer‑related fatalities worldwide. Immunotherapy alone or in combination with chemotherapy has a favorable survival benefit for patients with CRC. Unlike αβ T cells, which are prone to drug resistance, γδ T cells do not exhibit major histocompatibility complex restriction and can target tumor cells through diverse mechanisms. Recent research has demonstrated the widespread involvement of Vδ1T, Vδ2T, and γδ T17 cells in tumorigenesis and progression. In the present review, the influence of different factors, including immune checkpoint molecules, the tumor microenvironment and microorganisms, was summarized on the antitumor/protumor effects of these cells, aiming to provide insights for the development of more efficient and less toxic immunotherapy‑based anticancer drugs.

Intestinal intraepithelial T lymphocytes (IEL) constitutively express high amounts of the cytotoxic proteases Granzymes (Gzm) A and B and are therefore thought to protect the intestinal epithelium against infection by killing infected epithelial cells. However, the role of IEL granzymes in a protective immune response has yet to be demonstrated. We show that GzmA and GzmB are required to protect mice against oral, but not intravenous, infection with Salmonella enterica serovar Typhimurium, consistent with an intestine-specific role. IEL-intrinsic granzymes mediate the protective effects by controlling intracellular bacterial growth and aiding in cell-intrinsic pyroptotic cell death of epithelial cells. Surprisingly, we found that both granzymes play non-redundant roles. GzmB -/- mice carried significantly lower burdens of Salmonella, as predominant GzmA-mediated cell death effectively reduced bacterial translocation across the intestinal barrier. Conversely, in GzmA -/- mice, GzmB-driven apoptosis favored luminal Salmonella growth by providing nutrients, while still reducing translocation across the epithelial barrier. Together, the concerted actions of both GzmA and GzmB balance cell death mechanisms at the intestinal epithelium to provide optimal control that Salmonella cannot subvert., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The neuroimmune axis has been the focus of many studies, with special emphasis on the interactions between the central nervous system and the different immune cell subsets. T cells are namely recognized to play a critical role due to their interaction with nerves, by secreting cytokines and neurotrophins, which regulate the development, function, and survival of neurons. In this context, γδ T cells are particularly relevant, as they colonize specific tissues, namely the meninges, and have a wide variety of complex functions that balance physiological systems. Notably, γδ T cells are not only key components for maintaining brain homeostasis but are also responsible for triggering or preventing inflammatory responses in various pathologies, including neurodegenerative diseases as well as neuropsychiatric and developmental disorders. Here, we provide an overview of the current state of the art on the contribution of γδ T cells in neuropathophysiology and delve into the molecular mechanisms behind it. We aim to shed light on γδ T cell functions in the central nervous system while highlighting upcoming challenges in the field and providing new clues for potential therapeutic strategies., (© 2024 The Author(s). European Journal of Immunology published by Wiley‐VCH GmbH.)

Immune-mediated kidney diseases, including glomerulonephritis (GN), represent a diverse spectrum of disorders characterized by inflammation within the glomerulus and other renal compartments. Despite recent advances, the immunopathogenesis of these diseases remains incompletely understood. Current therapeutic approaches based on nonspecific immunosuppression often result in suboptimal outcomes and significant side effects, highlighting the need for tailored interventions. The complexity of the immune system extends beyond classical T-cell immunity, with the emergence of unconventional T cells - γδ T cells, NKT cells, and MAIT cells - that exhibit a semi-invariant nature and unique functions that bridge innate and adaptive immunity. γδ T cells exhibit unique homing and activation mechanisms and respond to different ligands, implying a multifaceted role in immune regulation. The understanding of γδ T-cell involvement in kidney disease lags behind conventional T-cell research. However, advances in immune cell analysis technologies offer promising avenues for elucidating their precise functions. This review synthesizes the current knowledge on γδ T cells in renal diseases, explores potential therapeutic strategies, and presents a roadmap for future research directions., (© 2024 The Author(s). European Journal of Immunology published by Wiley‐VCH GmbH.)

The impact of dietary fiber on intestinal T cell development is poorly understood. Here we show that a low fiber diet reduces MHC-II antigen presentation by small intestinal epithelial cells (IECs) and consequently impairs development of CD4 + CD8αα + intraepithelial lymphocytes (DP IELs) through changes to the microbiota. Dietary fiber supports colonization by Segmented Filamentous Bacteria (SFB), which induces the secretion of IFNγ by type 1 innate lymphoid cells (ILC1s) that lead to MHC-II upregulation on IECs. IEC MHC-II expression caused either by SFB colonization or exogenous IFNγ administration induced differentiation of DP IELs. Finally, we show that a low fiber diet promotes overgrowth of Bifidobacterium pseudolongum, and that oral administration of B. pseudolongum reduces SFB abundance in the small intestine. Collectively we highlight the importance of dietary fiber in maintaining the balance among microbiota members that allow IEC MHC-II antigen presentation and define a mechanism of microbiota-ILC-IEC interactions participating in the development of intestinal intraepithelial T cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

The correlation between clinical, serological, and endoscopic findings and histological response after a gluten-free diet (GFD) is limited in adult celiac (CD) patients. This study aims to evaluate the effects of GFD on intraepithelial lymphocyte (IEL) localization by comparing the histopathological, clinical, serological, and endoscopic findings of adult CD patients. The patients (n = 131) were divided into three groups: those with good (CDgc) (n = 23) and poor (CDpc) (n = 21) GFD compliance and newly diagnosed ones (nCD) (n = 87). Total and supranuclear IELs were counted per 100 enterocytes and divided into three groups: apical, mixed, and basal, according to ROC (Receiver operating characteristic) analysis. The roles of clinicopathological parameters in predicting good dietary compliance were calculated using the multivariable logistic regression model. CDgc group predominantly (78.3 %) exhibited a basal pattern, and none exhibited an apical. Conversely, most CDpc and nCD patients showed mixed (66.7 % and 73.6 %, respectively) and apical (9.5 % and 25.3 %) patterns. Non-atrophic Marsh types (p = 0.040) and basal pattern (p = 0.043) were independent parameters predicting good dietary compliance. This study first showed that IEL localizations can indicate GFD compliance in samples from CD patients. Localization-based examination of IELs can be an additional histological indicator in monitoring GFD compliance and signs of recovery, especially in adult CD patients., Competing Interests: Declaration of competing interest The authors declare no competing interest., (Copyright © 2025 Elsevier Inc. All rights reserved.)

An age-dependent increase in interferon (IFN)-γ expression by intestinal intraepithelial lymphocytes (IELs) contributes to the acquisition of resistance to infection by pathogens. However, how IELs acquire the ability to produce IFN-γ remains to be elucidated. Here, we report that IELs in the small intestine acquire the ability to rapidly produce IFN-γ at two distinct life stages. TCRαβ+ IELs (αβIELs) started producing IFN-γ at 4 weeks of age, within 1 week after weaning. In contrast, TCRγδ+ IELs (γδIELs) started producing IFN-γ at 7 weeks of age. In mice lacking Eγ4, an enhancer of the TCRγ locus (Eγ4-/- mice), Thy-1+ Vγ5+ γδIELs, a major subpopulation of γδIELs, were specifically reduced and their ability to produce IFN-γ was severely impaired, whereas Vγ2+ γδIELs normally produced IFN-γ. In Eγ4-/- mice, TCR expression levels were reduced in Vγ5+ γδIEL precursors in the thymus but unchanged in the Vγ5+ IELs. Nevertheless, TCR responsiveness in Vγ5+ γδIELs was impaired in Eγ4-/- mice, suggesting that the TCR signal received in the thymus may determine TCR responsiveness and the ability to produce IFN-γ in the gut. These results suggest that αβIELs and γδIELs start producing IFN-γ at different life stages and that the ability of Vγ5+ γδIELs to produce IFN-γ in the gut may be predetermined by TCR signalling in IEL precursors in the thymus., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Japanese Society for Immunology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Purpose: To determine whether γδ T cells regulate natural killer (NK) cells in the herpes simplex virus 1 (HSV-1)-infected cornea., Methods: CD57Bl/6 (wild-type [WT]), TCRδ-/-, and IFN-γ-/- mice were infected intracorneally with HSV-1. TCR-/- mice were treated with IL-17A at 24 hours post-infection (PI), and the WT mice received treatments of fingolimod (FTY720) and anti-IL-17A. At 48 hours PI, corneas were excised, and intracellular staining flow cytometry was performed, as well as multiplex analysis. Additionally, single-cell RNA sequencing (scRNAseq) was done to analyze the transcriptome of NK cells from WT and TCRδ-/- mice., Results: In mice lacking γδ T cells, there were significantly fewer NK cells following ocular HSV-1 infection. This reduction of NK cells corresponded with lower levels of cytokines and chemokines associated with the antiviral response. Furthermore, NK cells from WT mice had enriched IL-17A signaling compared to those from TCRδ-/- mice. The NK cell response was partially rescued in TCRδ-/- mice by administration of IL-17A. Correspondingly, the NK cell response could be blunted in WT mice by administration of anti-IL-17A. Finally, IFN-γ-/- mice had significantly less IL-17A production compared to WT mice., Conclusions: γδ T17 cells promote NK cell accumulation in HSV-1-infected corneas. In turn, NK cells secrete IFN-γ, which negatively regulates further IL-17A production by γδ T cells.

Pulmonary melioidosis is a severe tropical infection caused by Burkholderia pseudomallei and is associated with high mortality, despite early antibiotic treatment. γδ T cells have been increasingly implicated as drivers of the host neutrophil response during bacterial pneumonia, but their role in pulmonary melioidosis is unknown. Here, we report that in patients with melioidosis, a lower peripheral blood γδ T-cell concentration is associated with higher mortality, even when adjusting for severity of illness. γδ T cells were also enriched in the lung and protected against mortality in a mouse model of pulmonary melioidosis. γδ T-cell deficiency in infected mice induced an early recruitment of neutrophils to the lung, independent of bacterial burden. Subsequently, γδ T-cell deficiency resulted in increased neutrophil-associated inflammation in the lung as well as impaired bacterial clearance. In addition, γδ T cells influenced neutrophil function and subset diversity in the lung after infection. Our results indicate that γδ T cells serve a novel protective role in the lung during severe bacterial pneumonia by regulating excessive neutrophil-associated inflammation.

Intraepithelial lymphocytes (IELs) expressing the TCRγδ survey the intestinal epithelium to limit the invasion of microbial pathogens. The production of type I IFN is a central component of an antiviral immune response, yet how these proinflammatory cytokines contribute to γδ IEL effector function remains unclear. Based on the unique activation status of IELs and their ability to bridge innate and adaptive immunity, we investigated the extent to which type I IFN signaling modulates γδ IEL function. Using an ex vivo culture model, we find that type I IFN alone is unable to drive IFN-γ production, yet low-level TCR activation synergizes with type I IFN to induce IFN-γ production in murine γδ IELs. Further investigation into the underlying molecular mechanisms of costimulation revealed that TCRγδ-mediated activation of NFAT and JNK is required for type I IFN to promote IFN-γ expression in a STAT4-dependent manner. Whereas type I IFN rapidly upregulates antiviral gene expression independent of a basal TCRγδ signal, neither tonic TCR triggering nor the presence of a TCR agonist was sufficient to elicit type I IFN-induced IFN-γ production in vivo. However, bypassing proximal TCR signaling events synergized with IFNAR/STAT4 activation to induce γδ IEL IFN-γ production. These findings indicate that γδ IELs contribute to host defense in response to type I IFN by mounting a rapid antimicrobial response independent of TCRγδ signaling, and may produce IFN-γ in a TCR-dependent manner under permissive conditions., (Copyright © 2024 by The American Association of Immunologists, Inc.)

The intestinal epithelium harbours a unique lymphocyte population, the intraepithelial lymphocytes (IELs). A large fraction of IELs is represented by γδ T cells. Their role in epithelial homeostasis and immune response is well documented, but a conclusive view of their developmental pathway is still missing. In this review, we discuss the existing literature as well as recent advances regarding the tissue adaptation of γδ IELs, both for the characteristic cytotoxic subset and the newly described noncytotoxic subset. We particularly highlight the environmental cues and the transcriptional regulation that equip γδ T cells with their IEL phenotype., (© 2024 The Author(s). European Journal of Immunology published by Wiley‐VCH GmbH.)

Gamma delta T cells (γδT cells) play crucial roles in the immune response against tumors, yet their functional dynamics under different cancer therapies remain poorly understood. Laser Ablative Immunotherapy (LAIT) is a novel cancer treatment modality combining local photothermal therapy (PTT) and intratumoral injection of an immunostimulant, N-dihydrogalactochitosan (glycated chitosan, GC). LAIT has been shown to induce systemic antitumor immune responses in pre-clinical studies and clinical trials, eradicating both treated local tumors and untreated distant metastases. In this study, we used LAIT to treat breast tumors in a mouse model and investigated the effects of LAIT on tumor-infiltrating γδT cells using single-cell RNA sequencing (scRNAseq). We characterized the γδT cells from tumors in control, PTT, GC, and LAIT (PTT + GC) groups, by identifying six distinct subtypes: activated, cytotoxic, cycling cytotoxic, IFN-enriched, antigen-presenting, and IL17-producing γδT cells. Differential gene expression analysis revealed that LAIT significantly upregulated genes associated with T cell activation, leukocyte adhesion, and interferon signaling in treated tumor tissues while downregulating genes involved in protein folding and stress responses. LAIT also uniquely increased the proportion of IL17-producing γδT cells, which correlated with prolonged survival in breast cancer patients, as analyzed using TCGA data. Furthermore, the transcriptomic profiles of γδT cells in LAIT-treated tumors closely resembled those in immune checkpoint inhibitor (ICI)-treated patients, suggesting potential synergistic effects. Our findings indicate that LAIT modulates the γδT cell transcriptome, enhancing their antitumor capabilities and providing a basis for combining LAIT with ICI therapy to improve cancer treatment outcomes., Competing Interests: Declaration of competing interest Wei R. Chen is co-founder and an unpaid member of the Board of Directors of Immunophotonics, Inc. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Gamma-delta T cells (γδ T cells) play a crucial role in both innate and adaptive immunity within tumors, yet their presence and prognostic value in cancer remain underexplored. This study presents a large-scale analysis of γδ T cell receptor (γδ TCR) reads from 11,000 tumor samples spanning 33 cancer types, utilizing the TRUST4 algorithm. Our findings reveal extensive diversity in γδ TCR clonality and gene expression, underscoring the potential of γδ T cells as prognostic biomarkers in various cancers. We further demonstrate the utility of TCR gamma (TRG) and delta (TRD) gene expression from standard RNA-sequencing (RNA-seq) data. This comprehensive dataset offers a valuable resource for advancing γδ T cell research, with implications for enhanced immunotherapy approaches or alternative therapeutic strategies. Additionally, our centralized database supports translational research into the therapeutic significance of γδ T cells., Competing Interests: Declaration of interests J.R.C.-G. is a consultant for Anixa Biosciences and Alloy Therapeutics; holds stock options in Compass Therapeutics, Anixa Biosciences, and Alloy Therapeutics; has a patent licensed by Anixa Biosciences; owns intellectual property filed with Compass Therapeutics; and is a co-founder of Cellepus Therapeutics, a CAR T cell company., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

γδT cells represent a group of immune cells that are understudied but whose utility has been recognized for cancer immunotherapy purposes. Recent studies have highlighted a critical role for these cells in tumor initiation, growth, and metastasis and revealed an increasingly complex biology of γδT cell subsets that is context and tissue specific. We discuss here how γδT cell subsets are regulated, their interaction with cancer and other immune cells, and the implications from these latest discoveries for people with cancer., Competing Interests: Declaration of interests The authors declare no conflict of interests., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Intraepithelial lymphocytes (IELs) reside in the epithelial layer and protect against foreign pathogens, maintaining the epithelial barrier function in the intestine. Interactions between IEL and epithelial cells are required for IELs to function effectively; however, the underlying molecular machinery remains to be elucidated. In this study, we found that intestinal epithelium-specific deficiency of the clathrin adaptor protein (AP)-1B, which regulates basolateral protein sorting, led to a massive reduction in IELs. Quantitative proteomics demonstrated that dozens of proteins, including known IEL-interacting proteins (E-cadherin, butyrophilin-like 2, and plexin B2), were decreased in the basolateral membrane of AP-1B-deficient epithelial cells. Among these proteins, CD166 interacted with CD6 on the surface of induced IEL. CD166 knockdown, using shRNA in intestinal organoid cultures, significantly inhibited IEL recruitment to the epithelial layer. These findings highlight the essential role of AP-1B-mediated basolateral sorting in IEL maintenance and survival within the epithelial layer. This study reveals a novel function of AP-1B in the intestinal immune system., (© 2024. The Author(s).)

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.

The prevalence of obesity in the United States has continued to increase over the past several decades. Understanding how diet-induced obesity modulates mucosal immunity is of clinical relevance. We previously showed that consumption of a high fat, high sugar "Western" diet (WD) reduces the density and function of small intestinal Paneth cells, a small intestinal epithelial cell type with innate immune function. We hypothesized that obesity could also result in repressed gut adaptive immunity. Using small intestinal intraepithelial lymphocytes (IEL) as a readout, we found that in non-inflammatory bowel disease (IBD) subjects, high body mass index correlated with reduced IEL density. We recapitulated this in wild type (WT) mice fed with WD. A 4-week WD consumption was able to reduce IEL but not splenic, blood, or bone marrow lymphocytes, and the effect was reversible after another 2 weeks of standard diet (SD) washout. Importantly, WD-associated IEL reduction was not dependent on the presence of gut microbiota, as WD-fed germ-free mice also showed IEL reduction. We further found that WD-mediated Farnesoid X Receptor (FXR) activation in the gut triggered IEL reduction, and this was partially mediated by intestinal phagocytes. Activated FXR signaling stimulated phagocytes to secrete type I IFN, and inhibition of either FXR or type I IFN signaling within the phagocytes prevented WD-mediated IEL loss. Therefore, WD consumption represses both innate and adaptive immunity in the gut. These findings have significant clinical implications in the understanding of how diet modulates mucosal immunity., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: T. Stappenbeck advises Janssen, Boehringer Ingelheim, Kallyope, Takada, and Roche. T.C. Liu has research contracts with Denali Therapeutics and Interline Therapeutics. All other authors declare no relevant competing interests., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Injuries to the retinal pigment epithelium (RPE) trigger immune responses, orchestrating interactions within the innate and adaptive immune systems in the outer retina and choroid. We previously reported that interleukin 17 (IL-17) is a pivotal signaling molecule originating from choroidal γδ T cells, exerting protective effects by mediating functional connections between the RPE and subretinal microglia. In this current study, we generated mice with aryl hydrocarbon receptor (AhR) knockout specifically in IL-17-producing cells. These animals had deficiency in IL-17 production from γδ T cells, and exhibited increased sensitivity to both acute and chronic insults targeting the RPE. These findings imply that IL-17 plays a crucial role as a signaling cytokine in preserving the homeostasis of the outer retina and choroid., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Jiyang Cai reports was provided by The University of Oklahoma Health Sciences Center. Jiyang Cai reports was provided by The University of Oklahoma Health Sciences Center. Jiyang Cai reports a relationship with The University of Oklahoma Health Sciences Center that includes: Jiyang Cai has patent pending to NA. NA If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The PD-1-PD-L1 immune checkpoint helps to maintain self-tolerance and prevent the development of autoimmune diseases. Immune checkpoint inhibitors are successful immunotherapeutics for several cancers, but responding patients can develop immune-mediated adverse events. It is well established that PD-1 regulates CD4 and CD8 T-cell responses, but its role in controlling the activation of pathogenic γδ T cells is less clear. Here we examined the role of PD-1 in regulating γδ T cells in experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis. We found that PD-1 was highly expressed on CD27 - Vγ4 γδ T cells in the lymph node (LN) and CNS of mice with EAE. Treatment of mice with anti-PD-1 significantly augmented IL-17A-producing CD27 - Vγ4 γδ T cells in the LN and CNS and enhanced the severity of EAE. The exacerbating effect of anti-PD-1 on EAE was lost in Tcrd -/- mice. Conversely, ligation of PD-1 suppressed Il17a and Rorc gene expression and IL-17A production by purified Vγ4 γδ T cells stimulated via the TCR, but not with IL-1β and IL-23. Our study demonstrates that PD-1 regulates TCR-activated CD27 - Vγ4 γδ T cells, but that cytokine-activated IL-17A producing γδ T cells escape the regulatory effects of the PD-1-PD-L1 pathway., (© 2024 The Author(s). European Journal of Immunology published by Wiley‐VCH GmbH.)

Oral squamous cell carcinoma (OSCC) arises in the oral epithelium, a tissue in which immune surveillance is mediated by its primary resident leukocytes, Langerhans cells (LCs), and γδT cells. Under steady-state conditions, LCs and γδT cells play a critical role in maintaining oral mucosal homeostasis. As antigen-presenting cells of stratified epithelia, LCs respond to various challenges faced by the epithelium, orchestrating innate, and adaptive immune responses in order to resolve them. γδT cells also sense diverse epithelial insults and react rapidly through cytokine production and cytolytic activity. These epithelial sentinels are also considered to be the first leukocytes in the oral epithelium to encounter early carcinogenic events that have the potential of becoming OSCC. As evident in many malignancies, leukocyte populations help prevent cancer development although they also promote tumor progression. OSCC is no exception, as studies have reported both anti- and pro-tumor roles of LCs and γδT cells. In this review, we summarize the ontogeny of LCs and γδT cells in the oral epithelium and discuss their role in OSCC., (© 2024 The Authors. Periodontology 2000 published by John Wiley & Sons Ltd.)

In naive individuals, sensory neurons directly detect and respond to allergens, leading to both the sensation of itch and the activation of local innate immune cells, which initiate the allergic immune response 1,2 . In the setting of chronic allergic inflammation, immune factors prime sensory neurons, causing pathologic itch 3-7 . Although these bidirectional neuroimmune circuits drive responses to allergens, whether immune cells regulate the set-point for neuronal activation by allergens in the naive state is unknown. Here we describe a γδ T cell-IL-3 signalling axis that controls the allergen responsiveness of cutaneous sensory neurons. We define a poorly characterized epidermal γδ T cell subset 8 , termed GD3 cells, that produces its hallmark cytokine IL-3 to promote allergic itch and the initiation of the allergic immune response. Mechanistically, IL-3 acts on Il3ra-expressing sensory neurons in a JAK2-dependent manner to lower their threshold for allergen activation without independently eliciting itch. This γδ T cell-IL-3 signalling axis further acts by means of STAT5 to promote neuropeptide production and the initiation of allergic immunity. These results reveal an endogenous immune rheostat that sits upstream of and governs sensory neuronal responses to allergens on first exposure. This pathway may explain individual differences in allergic susceptibility and opens new therapeutic avenues for treating allergic diseases., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease. Elevated serum immunoglobulin G (IgG) levels, autoantibodies, and histopathological interface hepatitis are the hallmarks of AIH. Autoantibodies and pathological findings, clinical and biochemical features, typical immunoglobulin levels, and exclusion of other diseases are used to diagnose the condition. Gamma-delta (γδ) T cells are a unique population of unconventional T cells with γ and δ glycoprotein chains. γδ T cells have been shown to play a crucial role in autoimmune diseases by producing interleukin (IL)-17. However, its role in AIH remains to be further elucidated. In this study, we aimed to examine the role of γδ T cells and IL-17 in the pathogenesis of AIH, by working on biopsy samples. Paraffin blocks of 18 patients with type 1 AIH and 18 control liver tissues were analyzed. qRT-PCR assessed IL-17 gene expression. Immunofluorescence double staining of CD3 + TCRγδ + was performed to reveal tissue-resident γδ T cells' role in AIH. When comparing AIH to the control, there was a substantial increase in the ratio of CD3 + TCRγδ + cells in total inflammatory cells (p = 0.01). IL-17 gene expression was lowered in AIH when compared to the control (p = 0.01). This study provides evidence for the involvement of γδ T cells and IL-17 in the pathogenesis of AIH. The ratio of γδ T cells and IL-17 gene expression showed a significant difference in AIH suggesting a potential role for γδ T cells in driving liver inflammation in A fIH., Competing Interests: Declarations Ethical approval This study was approved by the Ethical Committee of Kartal Dr. Lutfi Kirdar City Hospital (Ethics No: 2022/514/236/9), School of Medicine, University of Health Sciences, Istanbul, Turkey. Informed consent None Consent to participate The participants have already given informed consent. Consent for publication All authors provide this consent. Conflict of interest The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Gamma/delta T (γδ T)cells possess a unique mechanism for killing tumors, making them highly promising and distinguished among various cell therapies for tumor treatment. This review focuses on the major histocompatibility complex (MHC)-independent recognition of antigens and the interaction between γδ T cells and solid tumor cells. A comprehensive review is provided regarding the classification of human gamma-delta T cell subtypes, the characteristics and mechanisms underlying their functions, as well as their r545egulatory effects on tumor cells. The involvement of γδ T cells in tumorigenesis and migration was also investigated, encompassing potential therapeutic targets such as apoptosis-related molecules, the TNF receptor superfamily member 6(FAS)/FAS Ligand (FASL) pathways, butyrophilin 3A-butyrophilin 2A1 (BTN3A-BTN2A1) complexes, and interactions with CD4, CD8, and natural killer (NK) cells. Additionally, immune checkpoint inhibitors such as programmed cell death protein 1/Programmed cell death 1 ligand 1 (PD-1/PD-L1) have the potential to augment the cytotoxicity of γδ T cells. Moreover, a review on gamma-delta T cell therapy products and their corresponding clinical trials reveals that chimeric antigen receptor (CAR) gamma-delta T therapy holds promise as an approach with encouraging preclinical outcomes. However, practical issues pertaining to manufacturing and clinical aspects need resolution, and further research is required to investigate the long-term clinical side effects of CAR T cells. In conclusion, more comprehensive studies are necessary to establish standardized treatment protocols aimed at enhancing the quality of life and survival rates among tumor patients utilizing γδ T cell immunotherapy., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zhu, Ren, Xie, Chen, Liang, Jiang, Wang and Zheng.)

Marek's disease virus (MDV) is an oncogenic alphaherpesvirus that causes deadly lymphomas in chickens. In chickens, up to 50% of all peripheral T cells are gamma delta (γδ) T cells. Until now, their role in MDV pathogenesis and tumor formation remains poorly understood. To investigate the role of γδ T cells in MDV pathogenesis, we infected recently generated γδ T cell knockout chickens with very virulent MDV. Strikingly, disease and tumor incidence were highly increased in the absence of γδ T cells, indicating that γδ T cells play an important role in the immune response against MDV. In the absence of γδ T cells, virus replication was drastically increased in the thymus and spleen, which are potential sites of T cell transformation. Taken together, our data provide the first evidence that γδ T cells play an important role in the pathogenesis and tumor formation of this highly oncogenic herpesvirus.IMPORTANCEGamma delta (γδ) T cells are the most abundant T cells in chickens, but their role in fighting pathogens remains poorly understood. Marek's disease virus (MDV) is an important veterinary pathogen, that causes one of the most frequent cancers in animals and is used as a model for virus-induced tumor formation. Our study revealed that γδ T cells play a crucial role in combating MDV, as disease and tumor incidence drastically increased in the absence of these cells. γδ T cells restricted virus replication in the key lymphoid organs, thereby decreasing the likelihood of causing tumors and disease. This study provides novel insights into the role of γδ T cells in the pathogenesis of this highly oncogenic virus., Competing Interests: The authors declare no conflict of interest.

Cholangiocarcinoma (CCA) is a rare disease characterized by malignant cells derived from the epithelial cells of the biliary duct system. Despite extensive treatments, the prognosis for CCA remains poor, emphasizing the critical need for the development of novel treatments. Considerable attention has been directed towards innate immune effector cells, which can recognize tumor cells independently of the major histocompatibility complex, laying the foundation for the development of off-the-shelf drugs. In this study, we cultured innate immune cells obtained from the peripheral blood of healthy adults and conducted a comparative analysis of the effector functions against CCA cell lines by Vδ2 γδ T cells and NK cells. This analysis was performed using standard short- and long-term cytotoxicity assays, as well as ELISA for IFN-γ. Vδ2 γδ T cells demonstrated cytotoxicity and IFN-γ production in response to CCA cells in a TCR-dependent manner, particularly in the presence of tetrakis-pivaloyloxymethyl 2-(thiazole-2-ylamino)ethylidene-1,1-bisphosphonate, a bisphosphonate prodrug. In contrast, direct killing and antibody-dependent cellular cytotoxicity were relatively slow and weak. Conversely, NK cells displayed potent, direct cytotoxicity against CCA cells. In summary, both Vδ2 γδ T cells and NK cells show promise as innate immune effector cells for adoptive transfer therapy in the context of CCA.

Sepsis is a critical global health concern linked to high mortality rates, often due to acute lung injury (ALI)/acute respiratory distress syndrome (ARDS). While the gut-lung axis involvement in ALI is recognized, direct migration of gut immune cells to the lung remains unclear. Our study reveals sepsis-induced migration of γδ T17 cells from the small intestine to the lung, triggering an IL-17A-dominated inflammatory response in mice. Wnt signaling activation in alveolar macrophages drives CCL1 upregulation, facilitating γδ T17 cell migration. CD44 + Ly6C - IL-7R high CD8 low cells are the primary migratory subtype exacerbating ALI. Esketamine attenuates ALI by inhibiting pulmonary Wnt/β-catenin signaling-mediated migration. This work underscores the pivotal role of direct gut-to-lung memory γδ T17 cell migration in septic ALI and clarifies the importance of localized IL-17A elevation in the lung., (© 2024. The Author(s).)

Background: Oral lichen planus (OLP) is a common T cell-mediated oral mucosal immune inflammatory disease. Intraepithelial lymphocytes (IELs) are a unique subset of T cells that play an important role in regulating immune response. This study aims to investigate the phenotype and the differentiation mechanism of IELs in OLP., Methods: The expression of CD4, CD8α, CD8β, T-helper-inducing POZ/Krueppel-like factor (ThPOK), and RUNX family transcription factor 3 (Runx3) in the epithelium and peripheral blood mononuclear cells (PBMCs) of OLP was determined by immunofluorescence and immunohistochemistry. Then, the correlations among them were analyzed. Naïve CD4 + T cells were sorted from blood of OLP patients and stimulated with retinoic acid (RA) and transforming growth factor-β 1 (TGF-β 1 ). Then the expression of CD4, CD8α, CD8β, ThPOK, and Runx3 was investigated by immunocytochemistry., Results: CD8α expression and CD8αα + cells were upregulated in the epithelium of OLP, whereas they were downregulated in PBMCs of OLP. CD8β was not expressed in the epithelium of OLP. CD4, CD8α, and Runx3 expression and CD4 + CD8α + cells were increased, whereas ThPOK expression was decreased in the epithelium of OLP. CD8α expression was positively correlated with Runx3 expression, whereas ThPOK expression was negatively correlated with Runx3 expression. After RA and TGF-β 1 stimulation, CD8α and Runx3 expression was upregulated, and ThPOK expression was downregulated in naïve CD4 + T cells., Conclusion: CD4 + CD8αα + IELs may be the dominant phenotype of IELs in OLP, and the differentiation of CD4 + CD8αα + IELs in OLP is negatively regulated by ThPOK and positively regulated by Runx3., (© 2024 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Butyrophilin (BTN) molecules are emerging as key regulators of T cell immunity; however, how they trigger cell-mediated responses is poorly understood. Here, the crystal structure of a gamma-delta T cell antigen receptor (γδTCR) in complex with BTN2A1 revealed that BTN2A1 engages the side of the γδTCR, leaving the apical TCR surface bioavailable. We reveal that a second γδTCR ligand co-engages γδTCR via binding to this accessible apical surface in a BTN3A1-dependent manner. BTN2A1 and BTN3A1 also directly interact with each other in cis, and structural analysis revealed formation of W-shaped heteromeric multimers. This BTN2A1-BTN3A1 interaction involved the same epitopes that BTN2A1 and BTN3A1 each use to mediate the γδTCR interaction; indeed, locking BTN2A1 and BTN3A1 together abrogated their interaction with γδTCR, supporting a model wherein the two γδTCR ligand-binding sites depend on accessibility to cryptic BTN epitopes. Our findings reveal a new paradigm in immune activation, whereby γδTCRs sense dual epitopes on BTN complexes., (© 2024. The Author(s), under exclusive licence to Springer Nature America, Inc.)

Therapeutic strategies targeting non-adaptive immune cells are currently in clinical development. γδT cells are a small subtype of T cells (1-10% of total T cells) that mediate their effector function without the necessity of the antigen presenting machinery, and also share functional properties with innate cells. Among the different γδT subtypes, antibodies against Vγ9Vδ2T have reported signs of clinical efficacy in early clinical studies. In this review we describe the biology of this subtype of non-conventional T cells and provide insights into the mechanism of action of novel antibodies that activate these cells. We will focus on antibodies targeting the BTN3A ligand and bi-specific γδT cell engagers. We will review in detail the advantages of these strategies including the potential for overcoming mechanisms of resistance to check point inhibitors, or the much more adequate safety profile compared with agents activating classical T cells. Limitations identified during the first studies in humans and strategies to overcome them will be revised and discussed. Finally, clinical options for future clinical development will be suggested., Competing Interests: AO has provided in the last 5 years consultant services for NMS, Servier, Worldwide International Trials and CancerAppy. Has been a former employee of Symphogen. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Paniagua-Herranz, Díaz-Tejeiro, Sanvicente, Bartolomé, Nieto-Jiménez and Ocana.)

Background: Gamma-delta (γδ) T cells are a major immune cell subset in pigs. Approximately 50% of circulating T cells are γδ T cells in young pigs and up to 30% in adult sows. Despite this abundance, the functions of porcine γδ T cells are mostly unidentified. In humans and mice, activated γδ T cells exhibit broad innate cytotoxic activity against a wide variety of stressed, infected, and cancerous cells through death receptor/ligand-dependent and perforin/granzyme-dependent pathways. However, so far, it is unknown whether porcine γδ T cells have the ability to perform cytotoxic functions., Methods: In this study, we conducted a comprehensive phenotypic characterization of porcine γδ T cells isolated from blood, lung, and nasal mucosa. To further analyze the cytolytic potential of γδ T cells, in vitro cytotoxicity assays were performed using purified γδ T cells as effector cells and virus-exposed or mock-treated primary porcine alveolar macrophages as target cells., Results: Our results show that only CD2 + γδ T cells express cytotoxic markers (CD16, NKp46, perforin) with higher perforin and NKp46 expression in γδ T cells isolated from lung and nasal mucosa. Moreover, we found that γδ T cells can exhibit cytotoxic functions in a cell-cell contact and degranulation-dependent manner. However, porcine γδ T cells did not seem to specifically target Porcine Reproductive and Respiratory Syndrome Virus or swine Influenza A Virus-infected macrophages, which may be due to viral escape mechanisms., Conclusion: Porcine γδ T cells express cytotoxic markers and can exhibit cytotoxic activity in vitro. The specific mechanisms by which porcine γδ T cells recognize target cells are not fully understood but may involve the detection of cellular stress signals., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Bettin, Darbellay, van Kessel, Dhar and Gerdts.)

Gamma delta (γδ) T cells are a heterogeneous population of cells that play roles in inflammation, host tissue repair, clearance of viral and bacterial pathogens, regulation of immune processes, and tumor surveillance. Recent research suggests that these are the main skin cells that produce interleukin-17 (I-17). Furthermore, γδ T cells exhibit memory-cell-like characteristics that mediate repeated episodes of psoriatic inflammation. γδ T cells are found in epithelial tissues, where many cancers develop. There, they participate in antitumor immunity as cytotoxic cells or as immune coordinators. γδ T cells also participate in host defense, immune surveillance, and immune homeostasis. The aim of this review is to present the importance of γδ T cells in physiological and pathological diseases, such as psoriasis, atopic dermatitis, autoimmune diseases, cancer, and lymphoma.

The Bacillus Calmette Guerin (BCG) vaccine has been shown to induce non-specific protection against diseases other than tuberculosis in vaccinated individuals, attributed to the induction of trained immunity. We have previously demonstrated that BCG administration induces innate immune training in mixed peripheral blood mononuclear cells and monocytes in calves. Gamma Delta (γδ) T cells are non-conventional T cells that exhibit innate and adaptive immune system features. They are in higher proportion in the peripheral blood of cattle than humans or rodents and play an essential role in bovine immune response to pathogens. In the current study, we determined if BCG administration induced innate immune training in bovine γδ T cells. A group of 16 pre-weaned Holstein calves (2-4 d age) were enrolled in the study and randomly assigned to vaccine and control groups (n=8/group). The vaccine group received two doses of 10 6 colony forming units (CFU) BCG Danish strain subcutaneously, separated by 2 weeks. The control group remained unvaccinated. Gamma delta T cells were purified from peripheral blood using magnetic cell sorting three weeks after receiving the 1 st BCG dose. We observed functional changes in the γδ T cells from BCG-treated calves shown by increased IL-6 and TNF-α cytokine production in response to in vitro stimulation with Escherichia coli LPS and PAM3CSK4. ATAC-Seq analysis of 78,278 regions of open chromatin (peaks) revealed that γδ T cells from BCG-treated calves had an altered epigenetic status compared to cells from the control calves. Differentially accessible peaks (DAP) found near the promoters of innate immunity-related genes like Siglec14 , Irf4 , Ifna2 , Lrrfip1 , and Tnfrsf10d were 1 to 4-fold more accessible in cells from BCG-treated calves. MOTIF enrichment analysis of the sequences within DAPs, which explores transcription factor binding motifs (TFBM) upstream of regulatory elements, revealed TFBM for Eomes and IRF-5 were among the most enriched transcription factors. GO enrichment analysis of genes proximal to the DAPs showed enrichment of pathways such as regulation of IL-2 production, T-cell receptor signaling pathway, and other immune regulatory pathways. In conclusion, our study shows that subcutaneous BCG administration in pre-weaned calves can induce innate immune memory in the form of trained immunity in γδ T cells. This memory is associated with increased chromatin accessibility of innate immune response-related genes, thereby inducing a functional trained immune response evidenced by increased IL-6 and TNF-α cytokine production., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Samuel, Diaz, Maina, Corbett, Tuggle and McGill.)

Background: The differential diagnosis between patients with celiac disease (CD) and non-celiac gluten sensitivity (NCGS) is difficult when a gluten-free diet (GFD) has been initiated before the diagnostic work-up. Isolated increases in TCRγδ+ and celiac lymphogram (increased TCRγδ+ plus decreased CD3-) may enable differential diagnosis in this challenging clinical setting. This study evaluated: (1) the accuracy of %TCRγδ+ and celiac lymphogram for diagnosing CD before and after GFD and for differentiation with NCGS; (2) TCRγδ+ kinetics at baseline and after starting GFD in both CD and NCGS., Methods: The inclusion criteria were patients with CD (n = 104), NCGS (n = 37), and healthy volunteers (n = 18). An intestinal biopsy for intraepithelial lymphogram by flow cytometry was performed at baseline and after GFD. The optimal cutoff for CD diagnostic accuracy was established by maximizing the Youden index and via logistic regression., Results: %TCRγδ+ showed better diagnostic accuracy than celiac lymphogram for identifying CD before and after GFD initiation. With a cutoff > 13.31, the accuracy for diagnosing CD in patients under GFD was 0.88 [0.80-0.93], whereas the accuracy for diagnosing NCGS (%TCRγδ+ ≤ 13.31) was 0.84 [0.76-0.89]. The percentage of TCRγδ+ cells showed differential kinetics between CD (baseline 22.7% [IQR, 16.4-33.6] vs. after GFD 26.4% [IQR, 17.8-36.8]; p = 0.026) and NCGS (baseline 9.4% [IQR, 4.1-14.6] vs. after GFD 6.4% [IQR, 3.2-11]; p = 0.022)., Conclusion: TCRγδ+ T cell assessment accurately diagnoses CD before and after a GFD. Increased TCRγδ+ was maintained in the long term after GFD in CD but not in NCGS. Altogether, this suggests the potential usefulness of this marker for the differential diagnosis of these two entities in patients on a GFD.