Heteromeric interactions regulate butyrophilin (BTN) and BTN-like molecules governing γδ T cell biology

Vγ9Vδ2 T cells recognize butyrophilin 2A1 and 3A1 heteromers

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.

Identification of drug targets for Sjögren's syndrome: multi-omics Mendelian randomization and colocalization analyses

Background

Targeted therapy for Sjögren's syndrome (SS) has become an important focus for clinicians. Multi-omics-wide Mendelian randomization (MR) analyses have provided new ideas for identifying potential drug targets.

Methods

We conducted summary-data-based Mendelian randomization (SMR) analysis to evaluate therapeutic targets associated with SS by integrating DNA methylation, gene expression and protein quantitative trait loci (mQTL, eQTL, and pQTL, respectively). Genetic associations with SS were derived from the FinnGen study (discovery) and the GWAS catalog (replication). Colocalization analyses were employed to determine whether two potentially relevant phenotypes share the same genetic factors in a given region. Moreover, to delve deeper into potential regulation among DNA methylation, gene expression, and protein abundance, we conducted MR analysis to explore the causal relationship between candidate gene methylation and expression, as well as between gene expression and protein abundance. Drug prediction and molecular docking were further employed to validate the pharmacological activity of the candidate drug targets.

Results

Upon integrating the multi-omics data, we identified three genes associated with SS risk: TNFAIP3, BTN3A1, and PLAU. The methylation of cg22068371 in BTN3A1 was positively associated with protein levels, consistent with the negative effect of cg22068371 methylation on the risk of SS. Additionally, positive correlations were observed between the gene methylation of PLAU (cg04939496) and expression, as well as between expression and protein levels. This consistency elucidates the promotional effects of PLAU on SS risk at the DNA methylation, gene expression, and protein levels. At the protein level, genetically predicted TNFAIP3 (OR 2.47, 95% CI 1.56-3.92) was positively associated with SS risk, while BTN3A1 (OR 2.96E-03, 95% CI 2.63E-04-3.33E-02) was negatively associated with SS risk. Molecular docking showed stable binding for candidate drugs and target proteins.

Conclusion

Our study reveals promising therapeutic targets for the treatment of SS, providing valuable insights into targeted therapy for SS. However, further validation through future experiments is warranted.

γδ T cells and the PD-1/PD-L1 axis: a love-hate relationship in the tumor microenvironment

Gamma delta (γδ) T cells demonstrate strong cytotoxicity against diverse cancer cell types in an MHC-independent manner, rendering them promising contenders for cancer therapy. Although amplification and adoptive transfer of γδ T cells are being evaluated in the clinic, their therapeutic efficacy remains unsatisfactory, primarily due to the influence of the immunosuppressive tumor microenvironment (TME). Currently, the utilization of targeted therapeutic antibodies against inhibitory immune checkpoint (ICP) molecules is a viable approach to counteract the immunosuppressive consequences of the TME. Notably, PD-1/PD-L1 checkpoint inhibitors are considered primary treatment options for diverse malignancies, with the objective of preserving the response of αβ T cells. However, γδ T cells also infiltrate various human cancers and are important participants in cancer immunity, thereby influencing patient prognosis. Hence, it is imperative to comprehend the reciprocal impact of the PD-1/PD-L1 axis on γδ T cells. This understanding can serve as a therapeutic foundation for improving γδ T cells adoptive transfer therapy and may offer a novel avenue for future combined immunotherapeutic approaches.

Unsynchronized butyrophilin molecules dictate cancer cell evasion of Vγ9Vδ2 T-cell killing

Vγ9Vδ2 T cells are specialized effector cells that have gained prominence as immunotherapy agents due to their ability to target and kill cells with altered pyrophosphate metabolites. In our effort to understand how cancer cells evade the cell-killing activity of Vγ9Vδ2 T cells, we performed a comprehensive genome-scale CRISPR screening of cancer cells. We found that four molecules belonging to the butyrophilin (BTN) family, specifically BTN2A1, BTN3A1, BTN3A2, and BTN3A3, are critically important and play unique, nonoverlapping roles in facilitating the destruction of cancer cells by primary Vγ9Vδ2 T cells. The coordinated function of these BTN molecules was driven by synchronized gene expression, which was regulated by IFN-γ signaling and the RFX complex. Additionally, an enzyme called QPCTL was shown to play a key role in modifying the N-terminal glutamine of these BTN proteins and was found to be a crucial factor in Vγ9Vδ2 T cell killing of cancer cells. Through our research, we offer a detailed overview of the functional genomic mechanisms that underlie how cancer cells escape Vγ9Vδ2 T cells. Moreover, our findings shed light on the importance of the harmonized expression and function of gene family members in modulating T-cell activity.

Effective γδ T-cell clinical therapies: current limitations and future perspectives for cancer immunotherapy

γδ T cells are a unique subset of T lymphocytes, exhibiting features of both innate and adaptive immune cells and are involved with cancer immunosurveillance. They present an attractive alternative to conventional T cell-based immunotherapy due, in large part, to their lack of major histocompatibility (MHC) restriction and ability to secrete high levels of cytokines with well-known anti-tumour functions. To date, clinical trials using γδ T cell-based immunotherapy for a range of haematological and solid cancers have yielded limited success compared with in vitro studies. This inability to translate the efficacy of γδ T-cell therapies from preclinical to clinical trials is attributed to a combination of several factors, e.g. γδ T-cell agonists that are commonly used to stimulate populations of these cells have limited cellular uptake yet rely on intracellular mechanisms; administered γδ T cells display low levels of tumour-infiltration; and there is a gap in the understanding of γδ T-cell inhibitory receptors. This review explores the discrepancy between γδ T-cell clinical and preclinical performance and offers viable avenues to overcome these obstacles. Using more direct γδ T-cell agonists, encapsulating these agonists into lipid nanocarriers to improve their pharmacokinetic and pharmacodynamic profiles and the use of combination therapies to overcome checkpoint inhibition and T-cell exhaustion are ways to bridge the gap between preclinical and clinical success. Given the ability to overcome these limitations, the development of a more targeted γδ T-cell agonist-checkpoint blockade combination therapy has the potential for success in clinical trials which has to date remained elusive.

Diester Prodrugs of a Phosphonate Butyrophilin Ligand Display Improved Cell Potency, Plasma Stability, and Payload Internalization

Activation of Vγ9Vδ2 T cells with butyrophilin 3A1 (BTN3A1) agonists such as (E)-4-hydroxy-3-methyl-but-2-enyl diphosphate (HMBPP) has the potential to boost the immune response. Because HMBPP is highly charged and metabolically unstable, prodrugs may be needed to overcome these liabilities, but the prodrugs themselves may be limited by slow payload release or low plasma stability. To identify effective prodrug forms of a phosphonate agonist of BTN3A1, we have prepared a set of diesters bearing one aryl and one acyloxymethyl group. The compounds were evaluated for their ability to stimulate Vγ9Vδ2 T cell proliferation, increase production of interferon γ, resist plasma metabolism, and internalize into leukemia cells. These bioassays have revealed that varied aryl and acyloxymethyl groups can decouple plasma and cellular metabolism and have a significant impact on bioactivity (>200-fold range) and stability (>10 fold range), including some with subnanomolar potency. Our findings increase the understanding of the structure-activity relationships of mixed aryl/acyloxymethyl phosphonate prodrugs.

A distinct topology of BTN3A IgV and B30.2 domains controlled by juxtamembrane regions favors optimal human γδ T cell phosphoantigen sensing

Butyrophilin (BTN)-3A and BTN2A1 molecules control the activation of human Vγ9Vδ2 T cells during T cell receptor (TCR)-mediated sensing of phosphoantigens (PAg) derived from microbes and tumors. However, the molecular rules governing PAg sensing remain largely unknown. Here, we establish three mechanistic principles of PAg-mediated γδ T cell activation. First, in humans, following PAg binding to the intracellular BTN3A1-B30.2 domain, Vγ9Vδ2 TCR triggering involves the extracellular V-domain of BTN3A2/BTN3A3. Moreover, the localization of both protein domains on different chains of the BTN3A homo-or heteromers is essential for efficient PAg-mediated activation. Second, the formation of BTN3A homo-or heteromers, which differ in intracellular trafficking and conformation, is controlled by molecular interactions between the juxtamembrane regions of the BTN3A chains. Finally, the ability of PAg not simply to bind BTN3A-B30.2, but to promote its subsequent interaction with the BTN2A1-B30.2 domain, is essential for T-cell activation. Defining these determinants of cooperation and the division of labor in BTN proteins improves our understanding of PAg sensing and elucidates a mode of action that may apply to other BTN family members.

Vγ9+Vδ2+ T cell control of Listeria monocytogenes growth in infected epithelial cells requires butyrophilin 3A genes

Intracellular bacteria produce antigens, which serve as potent activators of γδ T cells. Phosphoantigens are presented via a complex of butyrophilins (BTN) to signal infection to human Vγ9+Vδ2+ T cells. Here, we established an in vitro system allowing for studies of Vγ9+Vδ2+ T cell activity in coculture with epithelial cells infected with the intracellular bacterial pathogen Listeria monocytogenes. We report that the Vγ9+Vδ2+ T cells efficiently control L. monocytogenes growth in such cultures. This effector function requires the expression of members of the BTN3A family on epithelial cells. Specifically, we observed a BTN3A1-independent BTN3A3 activity to present antigen to Vγ9+Vδ2+ T cells. Since BTN3A1 is the only BTN3A associated with phosphoantigen presentation, our study suggests that BTN3A3 may present different classes of antigens to mediate Vγ9+Vδ2+ T cell effector function against L. monocytogenes-infected epithelia.

Characterization of Bovine Intraepithelial T Lymphocytes in the Gut

Intraepithelial T lymphocytes (T-IELs), which constitute over 50% of the total T lymphocytes in the animal, patrol the mucosal epithelial lining to defend against pathogen invasion while maintaining gut homeostasis. In addition to expressing T cell markers such as CD4 and CD8, T-IELs display T cell receptors (TCR), including either TCRαβ or TCRγδ. Both humans and mice share similar T-IEL subsets: TCRγδ+, TCRαβ+CD8αα+, TCRαβ+CD4+, and TCRαβ+CD8αβ+. Among these subsets, human T-IELs are predominantly TCRαβ+ (over 80%), whereas those in mice are mostly TCRγδ+ (~60%). Of note, the majority of the TCRγδ+ subset expresses CD8αα in both species. Although T-IELs have been extensively studied in humans and mice, their profiles in cattle have not been well examined. Our study is the first to characterize bovine T-IELs using flow cytometry, where we identified several distinct features. The percentage of TCRγδ+ was comparable to that of TCRαβ+ T-IELs (both ~50% of CD3+), and the majority of bovine TCRγδ+ T-IELs did not express CD8 (CD8-) (above 60%). Furthermore, about 20% of TCRαβ+ T-IELs were CD4+CD8αβ+, and the remaining TCRαβ+ T-IELs were evenly distributed between CD4+ and CD8αβ+ (~40% of TCRαβ+ T-IELs each) with no TCRαβ+CD8αα+ identified. Despite these unique properties, bovine T-IELs, similar to those in humans and mice, expressed a high level of CD69, an activation and tissue-retention marker, and a low level of CD62L, a lymphoid adhesion marker. Moreover, bovine T-IELs produced low levels of inflammatory cytokines such as IFNγ and IL17A, and secreted small amounts of the immune regulatory cytokine TGFβ1. Hence, bovine T-IELs' composition largely differs from that of human and mouse, with the dominance of the CD8- population among TCRγδ+ T-IELs, the substantial presence of TCRαβ+CD4+CD8αβ+ cells, and the absence of TCRαβ+CD8αα+ T-IELs. These results provide the groundwork for conducting future studies to examine how bovine T-IELs respond to intestinal pathogens and maintain the integrity of the gut epithelial barrier in animals.

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

Murine intraepithelial γδ T cells include distinct tissue-protective cells selected by epithelial butyrophilin-like (BTNL) heteromers. To determine whether this biology is conserved in humans, we characterized the colonic γδ T cell compartment, identifying a diverse repertoire that includes a phenotypically distinct subset coexpressing T cell receptor Vγ4 and the epithelium-binding integrin CD103. This subset was disproportionately diminished and dysregulated in inflammatory bowel disease, whereas on-treatment CD103+γδ T cell restoration was associated with sustained inflammatory bowel disease remission. Moreover, CD103+Vγ4+cell dysregulation and loss were also displayed by humans with germline BTNL3/BTNL8 hypomorphism, which we identified as a risk factor for penetrating Crohn's disease (CD). Thus, BTNL-dependent selection and/or maintenance of distinct tissue-intrinsic γδ T cells appears to be an evolutionarily conserved axis limiting the progression of a complex, multifactorial, tissue-damaging disease of increasing global incidence.

CRISPR screens decode cancer cell pathways that trigger γδ T cell detection

γδ T cells are potent anticancer effectors with the potential to target tumours broadly, independent of patient-specific neoantigens or human leukocyte antigen background1-5. γδ T cells can sense conserved cell stress signals prevalent in transformed cells2,3, although the mechanisms behind the targeting of stressed target cells remain poorly characterized. Vγ9Vδ2 T cells-the most abundant subset of human γδ T cells4-recognize a protein complex containing butyrophilin 2A1 (BTN2A1) and BTN3A1 (refs. 6-8), a widely expressed cell surface protein that is activated by phosphoantigens abundantly produced by tumour cells. Here we combined genome-wide CRISPR screens in target cancer cells to identify pathways that regulate γδ T cell killing and BTN3A cell surface expression. The screens showed previously unappreciated multilayered regulation of BTN3A abundance on the cell surface and triggering of γδ T cells through transcription, post-translational modifications and membrane trafficking. In addition, diverse genetic perturbations and inhibitors disrupting metabolic pathways in the cancer cells, particularly ATP-producing processes, were found to alter BTN3A levels. This induction of both BTN3A and BTN2A1 during metabolic crises is dependent on AMP-activated protein kinase (AMPK). Finally, small-molecule activation of AMPK in a cell line model and in patient-derived tumour organoids led to increased expression of the BTN2A1-BTN3A complex and increased Vγ9Vδ2 T cell receptor-mediated killing. This AMPK-dependent mechanism of metabolic stress-induced ligand upregulation deepens our understanding of γδ T cell stress surveillance and suggests new avenues available to enhance γδ T cell anticancer activity.

The emerging paradigm of Unconventional T cells as a novel therapeutic target for celiac disease

Celiac disease (CD) is an organ-specific autoimmune disorder that occurs in genetically predisposed individuals when exposed to exogenous dietary gluten. This exposure to wheat gluten and related proteins from rye and barley triggers an immune response which leads to the development of enteropathy associated with symptoms of bloating, diarrhea, or malabsorption. The sole current treatment is to follow a gluten-free diet for the rest of one's life. Intestinal barriers are enriched with Unconventional T cells such as iNKT, MAIT, and γδ T cells, which lack or express only a limited range of rearranged antigen receptors. Unconventional T cells play a crucial role in regulating mucosal barrier function and microbial colonization. Unconventional T cell populations are widely represented in diseased conditions, where changes in disease activity related to iNKT and MAIT cell reduction, as well as γδ T cell expansion, are demonstrated. In this review, we discuss the role and potential employment of Unconventional T cells as a therapeutic target in the pathophysiology of celiac disease.

Phosphoantigens glue butyrophilin 3A1 and 2A1 to activate Vγ9Vδ2 T cells

In both cancer and infections, diseased cells are presented to human Vγ9Vδ2 T cells through an 'inside out' signalling process whereby structurally diverse phosphoantigen (pAg) molecules are sensed by the intracellular domain of butyrophilin BTN3A11-4. Here we show how-in both humans and alpaca-multiple pAgs function as 'molecular glues' to promote heteromeric association between the intracellular domains of BTN3A1 and the structurally similar butyrophilin BTN2A1. X-ray crystallography studies visualized that engagement of BTN3A1 with pAgs forms a composite interface for direct binding to BTN2A1, with various pAg molecules each positioned at the centre of the interface and gluing the butyrophilins with distinct affinities. Our structural insights guided mutagenesis experiments that led to disruption of the intracellular BTN3A1-BTN2A1 association, abolishing pAg-mediated Vγ9Vδ2 T cell activation. Analyses using structure-based molecular-dynamics simulations, 19F-NMR investigations, chimeric receptor engineering and direct measurement of intercellular binding force revealed how pAg-mediated BTN2A1 association drives BTN3A1 intracellular fluctuations outwards in a thermodynamically favourable manner, thereby enabling BTN3A1 to push off from the BTN2A1 ectodomain to initiate T cell receptor-mediated γδ T cell activation. Practically, we harnessed the molecular-glue model for immunotherapeutics design, demonstrating chemical principles for developing both small-molecule activators and inhibitors of human γδ T cell function.

Targeting Melanoma-Associated Fibroblasts (MAFs) with Activated γδ (Vδ2) T Cells: An In Vitro Cytotoxicity Model

The tumor microenvironment (TME) has gained considerable scientific attention by playing a role in immunosuppression and tumorigenesis. Besides tumor cells, TME is composed of various other cell types, including cancer-associated fibroblasts (CAFs or MAFs when referring to melanoma-derived CAFs) and tumor-infiltrating lymphocytes (TILs), a subpopulation of which is labeled as γδ T cells. Since the current anti-cancer therapies using γδ T cells in various cancers have exhibited mixed treatment responses, to better understand the γδ T cell biology in melanoma, our research group aimed to investigate whether activated γδ T cells are capable of killing MAFs. To answer this question, we set up an in vitro platform using freshly isolated Vδ2-type γδ T cells and cultured MAFs that were biobanked from our melanoma patients. This study proved that the addition of zoledronic acid (1-2.5 µM) to the γδ T cells was necessary to drive MAFs into apoptosis. The MAF cytotoxicity of γδ T cells was further enhanced by using the stimulatory clone 20.1 of anti-BTN3A1 antibody but was reduced when anti-TCR γδ or anti-BTN2A1 antibodies were used. Since the administration of zoledronic acid is safe and tolerable in humans, our results provide further data for future clinical studies on the treatment of melanoma.

Local γδ T cells: translating promise to practice in cancer immunotherapy

Rapid bench-to-bedside translation of basic immunology to cancer immunotherapy has revolutionised the clinical practice of oncology over the last decade. Immune checkpoint inhibitors targeting αβ T cells now offer durable remissions and even cures for some patients with hitherto treatment-refractory metastatic cancers. Unfortunately, these treatments only benefit a minority of patients and efforts to improve efficacy through combination therapies utilising αβ T cells have seen diminishing returns. Alongside αβ T cells and B cells, γδ T cells are a third lineage of adaptive lymphocytes. Less is known about these cells, and they remain relatively untested in cancer immunotherapy. Whilst preclinical evidence supports their utility, the few early-phase trials involving γδ T cells have failed to demonstrate convincing efficacy in solid cancers. Here we review recent progress in our understanding of how these cells are regulated, especially locally within tissues, and the potential for translation. In particular, we focus on the latest advances in the field of butyrophilin (BTN) and BTN-like (BTNL) regulation of γδ T cells and speculate on how these advances may address the limitations of historical approaches in utilising these cells, as well as how they may inform novel approaches in deploying these cells for cancer immunotherapy.

Mutations to the BTN2A1 Linker Region Impact Its Homodimerization and Its Cytoplasmic Interaction with Phospho-Antigen-Bound BTN3A1

Intracellular binding of small-molecule phospho-Ags to the HMBPP receptor complex in infected cells leads to extracellular detection by T cells expressing the Vγ9Vδ2 TCR, a noncanonical method of Ag detection. The butyrophilin proteins BTN2A1 and BTN3A1 are part of the complex; however, their precise roles are unclear. We suspected that BTN2A1 and BTN3A1 form a tetrameric (dimer of dimers) structure, and we wanted to probe the importance of the BTN2A1 homodimer. We analyzed mutations to human BTN2A1, using internal domain or full-length BTN2A1 constructs, expressed in Escherichia coli or human K562 cells, that might disrupt its structure and/or function. Although BTN2A1 is a disulfide-linked homodimer, mutation of cysteine residues C247 and C265 did not affect the ability to stimulate T cell IFN-γ production by ELISA. Two mutations of the juxtamembrane region (at EKE282) failed to impact BTN2A1 function. In contrast, single point mutations (L318G and L325G) near the BTN2A1 B30.2 domain blocked phospho-Ag response. Size exclusion chromatography and nuclear magnetic resonance (NMR) experiments showed that the isolated BTN2A1 B30.2 domain is a homodimer, even in the absence of its extracellular and transmembrane region. [31P]-NMR experiments confirmed that HMBPP binds to BTN3A1 but not BTN2A1, and binding abrogates signals from both phosphorus atoms. Furthermore, the BTN2A1 L325G mutation but not the L318G mutation prevents both homodimerization of BTN2A1 internal domain constructs in size exclusion chromatography (and NMR) experiments and their binding to HMBPP-bound BTN3A1 in isothermal titration calorimetry experiments. Together, these findings support the importance of homodimerization within the BTN2A1 internal domain for phospho-Ag detection.

Evaluation of the impacts of photodynamic therapy on the prognosis of patients with hrHPV infection based on BTNL8 expression

Objective

The aim of this study was to evaluate the prognostic value of Butyrophilin-like protein 8 (BTNL8) expression in high-risk HPV (hrHPV) infection treated with photodynamic therapy.

Methods

A total of 93 patients with hrHPV infection were enrolled as research study subjects, along with 69 healthy women who served as controls. Serum samples were obtained from each participant, and BTNL8 levels were quantified. The patients were divided into high- and low-expression groups (n = 45 and n = 48, respectively), and both groups underwent photodynamic therapy. We recorded the following data: BTNL8 expression pre-treatment and at 3/6 months post-treatment, HPV negative conversion ratio, regression rate of low-grade squamous intraepithelial lesions (LSIL), incidence of adverse reactions, complication rate, serum inflammatory factors, persistence of HPV positivity, LSIL residue or recurrence, and incidence of high-grade cervical intraepithelial lesions (HCIL).

Results

Patients with HPV infection exhibited higher BTNL8 expression than healthy individuals. Compared to the low-expression group, the high-expression group showed increased HPV negative conversion ratios, LSIL regression rates, and levels of IL-17 and IL-23. This group also demonstrated decreased total complication rate, HPV positivity persistence, LSIL residue or recurrence, and IL-10 levels. Additionally, there was no significant difference between the two groups in terms of the number of adverse reactions and cases with LSIL residue/recurrence.

Conclusion

Serum BTNL8 expression may serve as a valuable tool for early screening and prognosis monitoring of patients with hrHPV infection.

γδ T cells in immunotherapies for B-cell malignancies

Despite the advancements in therapy for B cell malignancies and the increase in long-term survival of patients, almost half of them lead to relapse. Combinations of chemotherapy and monoclonal antibodies such as anti-CD20 leads to mixed outcomes. Recent developments in immune cell-based therapies are showing many encouraging results. γδ T cells, with their potential of functional plasticity and their anti-tumoral properties, emerged as good candidates for cancer immunotherapies. The representation and the diversity of γδ T cells in tissues and in the blood, in physiological conditions or in B-cell malignancies such as B cell lymphoma, chronic lymphoblastic leukemia or multiple myeloma, provides the possibility to manipulate them with immunotherapeutic approaches for these patients. In this review, we summarized several strategies based on the activation and tumor-targeting of γδ T cells, optimization of expansion protocols, and development of gene-modified γδ T cells, using combinations of antibodies and therapeutic drugs and adoptive cell therapy with autologous or allogenic γδ T cells following potential genetic modifications.

Butyrophilins: Dynamic Regulators of Protective T Cell Immunity in Cancer

The efficacy of current immunotherapies remains limited in many solid epithelial malignancies. Recent investigations into the biology of butyrophilin (BTN) and butyrophilin-like (BTNL) molecules, however, suggest these molecules are potent immunosuppressors of antigen-specific protective T cell activity in tumor beds. BTN and BTNL molecules also associate with each other dynamically on cellular surfaces in specific contexts, which modulates their biology. At least in the case of BTN3A1, this dynamism drives the immunosuppression of αβ T cells or the activation of Vγ9Vδ2 T cells. Clearly, there is much to learn regarding the biology of BTN and BTNL molecules in the context of cancer, where they may represent intriguing immunotherapeutic targets that could potentially synergize with the current class of immune modulators in cancer. Here, we discuss our current understanding of BTN and BTNL biology, with a particular focus on BTN3A1, and potential therapeutic implications for cancer.

Phosphoantigen sensing combines TCR-dependent recognition of the BTN3A IgV domain and germline interaction with BTN2A1

Vγ9Vδ2 T cells play critical roles in microbial immunity by detecting target cells exposed to pathogen-derived phosphoantigens (P-Ags). Target cell expression of BTN3A1, the "P-Ag sensor," and BTN2A1, a direct ligand for T cell receptor (TCR) Vγ9, is essential for this process; however, the molecular mechanisms involved are unclear. Here, we characterize BTN2A1 interactions with Vγ9Vδ2 TCR and BTN3A1. Nuclear magnetic resonance (NMR), modeling, and mutagenesis establish a BTN2A1-immunoglobulin V (IgV)/BTN3A1-IgV structural model compatible with their cell-surface association in cis. However, TCR and BTN3A1-IgV binding to BTN2A1-IgV is mutually exclusive, owing to binding site proximity and overlap. Moreover, mutagenesis indicates that the BTN2A1-IgV/BTN3A1-IgV interaction is non-essential for recognition but instead identifies a molecular surface on BTN3A1-IgV essential to P-Ag sensing. These results establish a critical role for BTN3A-IgV in P-Ag sensing, in mediating direct or indirect interactions with the γδ-TCR. They support a composite-ligand model whereby intracellular P-Ag detection coordinates weak extracellular germline TCR/BTN2A1 and clonotypically influenced TCR/BTN3A-mediated interactions to initiate Vγ9Vδ2 TCR triggering.

Archaic humans have contributed to large-scale variation in modern human T cell receptor genes

Human T cell receptors (TCRs) are critical for mediating immune responses to pathogens and tumors and regulating self-antigen recognition. Yet, variations in the genes encoding TCRs remain insufficiently defined. Detailed analysis of expressed TCR alpha, beta, gamma, and delta genes in 45 donors from four human populations-African, East Asian, South Asian, and European-revealed 175 additional TCR variable and junctional alleles. Most of these contained coding changes and were present at widely differing frequencies in the populations, a finding confirmed using DNA samples from the 1000 Genomes Project. Importantly, we identified three Neanderthal-derived, introgressed TCR regions including a highly divergent TRGV4 variant, which mediated altered butyrophilin-like molecule 3 (BTNL3) ligand reactivity and was frequent in all modern Eurasian population groups. Our results demonstrate remarkable variation in TCR genes in both individuals and populations, providing a strong incentive for including allelic variation in studies of TCR function in human biology.

Gamma delta T-cell-based immune checkpoint therapy: attractive candidate for antitumor treatment

As a nontraditional T-cell subgroup, γδT cells have gained popularity in the field of immunotherapy in recent years. They have extraordinary antitumor potential and prospects for clinical application. Immune checkpoint inhibitors (ICIs), which are efficacious in tumor patients, have become pioneer drugs in the field of tumor immunotherapy since they were incorporated into clinical practice. In addition, γδT cells that have infiltrated into tumor tissues are found to be in a state of exhaustion or anergy, and there is upregulation of many immune checkpoints (ICs) on their surface, suggesting that γδT cells have a similar ability to respond to ICIs as traditional effector T cells. Studies have shown that targeting ICs can reverse the dysfunctional state of γδT cells in the tumor microenvironment (TME) and exert antitumor effects by improving γδT-cell proliferation and activation and enhancing cytotoxicity. Clarification of the functional state of γδT cells in the TME and the mechanisms underlying their interaction with ICs will solidify ICIs combined with γδT cells as a good treatment option.

Division of labor and cooperation between different butyrophilin proteins controls phosphoantigen-mediated activation of human γδ T cells

Butyrophilin (BTN)-3A and BTN2A1 molecules control TCR-mediated activation of human Vγ9Vδ2 T-cells triggered by phosphoantigens (PAg) from microbes and tumors, but the molecular rules governing antigen sensing are unknown. Here we establish three mechanistic principles of PAg-action. Firstly, in humans, following PAg binding to the BTN3A1-B30.2 domain, Vγ9Vδ2 TCR triggering involves the V-domain of BTN3A2/BTN3A3. Moreover, PAg/B30.2 interaction, and the critical γδ-T-cell-activating V-domain, localize to different molecules. Secondly, this distinct topology as well as intracellular trafficking and conformation of BTN3A heteromers or ancestral-like BTN3A homomers are controlled by molecular interactions of the BTN3 juxtamembrane region. Finally, the ability of PAg not simply to bind BTN3A-B30.2, but to promote its subsequent interaction with the BTN2A1-B30.2 domain, is essential for T-cell activation. Defining these determinants of cooperation and division of labor in BTN proteins deepens understanding of PAg sensing and elucidates a mode of action potentially applicable to other BTN/BTNL family members.

The way of interaction between Vγ9Vδ2 T cells and tumor cells

Immunotherapy has been a promising, emerging treatment for various cancers. Gamma delta (γδ) T cells own a T cell receptor composed of γ- and δ- chain and act as crucial players in the anti-tumor immune effect. Currently, Vγ9Vδ2 T cells, the predominate γδ T cell subset in human peripheral blood, has been shown to exert multiple biological functions. In addition, a growing body of evidence notes that Vγ9Vδ2 T cells interact with tumor cells in many ways, such as TCR-mediated nonpeptidic-phosphorylated phosphoantigens (pAgs) recognization, NKG2D/NKG2D ligand (NKG2DL) pathway, Fas-FasL axis and antibody-dependent cellular cytotoxicity (ADCC) as well as exosome. More importantly, clinical studies with Vγ9Vδ2 T cells in cancers have propelled several clinical applications to investigate their safety and efficacy. Herein, this review summarized the underlying ways and mechanisms of interplay cancer cells and Vγ9Vδ2 T cells, which may help us to generate new strategies for tumor immunotherapy in the future.

Vγ9Vδ2 T-cell immunotherapy in blood cancers: ready for prime time?

In the last years, the tumor microenvironment (TME) has emerged as a promising target for therapeutic interventions in cancer. Cancer cells are highly dependent on the TME to growth and evade the immune system. Three major cell subpopulations are facing each other in the TME: cancer cells, immune suppressor cells, and immune effector cells. These interactions are influenced by the tumor stroma which is composed of extracellular matrix, bystander cells, cytokines, and soluble factors. The TME can be very different depending on the tissue where cancer arises as in solid tumors vs blood cancers. Several studies have shown correlations between the clinical outcome and specific patterns of TME immune cell infiltration. In the recent years, a growing body of evidence suggests that unconventional T cells like natural killer T (NKT) cells, mucosal-associated invariant T (MAIT) cells, and γδ T cells are key players in the protumor or antitumor TME commitment in solid tumors and blood cancers. In this review, we will focus on γδ T cells, especially Vγ9Vδ2 T cells, to discuss their peculiarities, pros, and cons as potential targets of therapeutic interventions in blood cancers.

BTN3A: A Promising Immune Checkpoint for Cancer Prognosis and Treatment

Butyrophilin-3A (BTN3A) subfamily members are a group of immunoglobulins present on the surface of different cell types, including innate and cancer cells. Due to their high similarity with the B7 family members, different studies have been conducted and revealed the involvement of BTN3A molecules in modulating T cell activity within the tumor microenvironment (TME). However, a great part of this research focused on γδ T cells and how BTN3A contributes to their functions. In this review, we will depict the roles and various aspects of BTN3A molecules in distinct tumor microenvironments and review how BTN3A receptors modulate diverse immune effector functions including those of CD4+ (Th1), cytotoxic CD8+ T cells, and NK cells. We will also highlight the potential of BTN3A molecules as therapeutic targets for effective immunotherapy and successful cancer control, which could represent a bright future for patient treatment.

A novel chromatin regulator-related immune checkpoint related gene prognostic signature and potential candidate drugs for endometrial cancer patients

Background

Endometrial cancer (EC) is the most common gynecologic malignancy in developed countries and its prevalence is increasing. As an emerging therapy with a promising efficacy, immunotherapy has been extensively applied in the treatment of solid tumors. In addition, chromatin regulators (CRs), as essential upstream regulators of epigenetics, play a significant role in tumorigenesis and cancer development.

Methods

CRs and immune checkpoint-related genes (ICRGs) were obtained from the previous top research. The Genome Cancer Atlas (TCGA) was utilized to acquire the mRNA expression and clinical information of patients with EC. Correlation analysis was utilized for screen CRs-related ICRGs (CRRICRGs). By Cox regression and least absolute shrinkage and selection operator (LASSO) analysis, prognosis related CRRICRGs were screened out and risk model was constructed. The Kaplan–Meier curve was used to estimate the prognosis between high- and low-risk group. By comparing the IC50 value, the drugs sensitivity difference was explored. We obtained small molecule drugs for the treatment of UCEC patients based on CAMP dataset.

Results

We successfully constructed a 9 CRRICRs-based prognostic signature for patients with UCEC and found the riskscore was an independent prognostic factor. The results of functional analysis suggested that CRRICRGs may be involved in immune processes associated with cancer. Immune characteristics analysis provided further evidence that the CRRICRGs-based model was correlated with immune cells infiltration and immune checkpoint. Eight small molecule drugs that may be effective for the treatment of UCEC patients were screened. Effective drugs identified by drug sensitivity profiling in high- and low-risk groups.

Conclusion

In summary, our study provided novel insights into the function of CRRICRGs in UCEC. We also developed a reliable prognostic panel for the survival of patients with UCEC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-022-00253-w.

Positron Emission Tomography Probes for Imaging Cytotoxic Immune Cells

Non-invasive positron emission tomography (PET) imaging of immune cells is a powerful approach for monitoring the dynamics of immune cells in response to immunotherapy. Despite the clinical success of many immunotherapeutic agents, their clinical efficacy is limited to a subgroup of patients. Conventional imaging, as well as analysis of tissue biopsies and blood samples do not reflect the complex interaction between tumour and immune cells. Consequently, PET probes are being developed to capture the dynamics of such interactions, which may improve patient stratification and treatment evaluation. The clinical efficacy of cancer immunotherapy relies on both the infiltration and function of cytotoxic immune cells at the tumour site. Thus, various immune biomarkers have been investigated as potential targets for PET imaging of immune response. Herein, we provide an overview of the most recent developments in PET imaging of immune response, including the radiosynthesis approaches employed in their development.

Long noncoding RNA profiling reveals that LncRNA BTN3A2 inhibits the host inflammatory response to Eimeria tenella infection in chickens

Coccidiosis is a widespread parasitic disease that causes serious economic losses to the poultry industry every year. Long noncoding RNAs (lncRNAs) play important roles in transcriptional regulation and are involved in a variety of diseases and immune responses. However, the lncRNAs associated with Eimeria tenella (E. tenella) resistance have not been identified in chickens. In addition, the expression profiles and functions of lncRNAs during E. tenella infection remain unclear. In the present study, high-throughput sequencing was applied to identify lncRNAs in chicken cecal tissues from control (JC), resistant (JR), and susceptible (JS) groups on day 4.5 post-infection (pi), and functional tests were performed. A total of 564 lncRNAs were differentially expressed, including 263 lncRNAs between the JS and JC groups, 192 between the JR and JS groups, and 109 between the JR and JC groups. Functional analyses indicated that these differentially expressed lncRNAs were involved in pathways related to E. tenella infection, including the NF-kappa B signaling, B cell receptor signaling and natural killer cell-mediated cytotoxicity pathways. Moreover, through cis regulation network analysis of the differentially expressed lncRNAs, we found that a novel lncRNA termed lncRNA BTN3A2 was significantly increased in both cecum tissue and DF-1 cells after coccidia infection or sporozoite stimulation. Functional test data showed that the overexpression of lncRNA BTN3A2 reduced the production of inflammatory cytokines, including IL-6, IL-1β, TNF-α and IL-8, while lncRNA BTN3A2 knockdown promoted the production of these inflammatory cytokines. Taken together, this study identify the differentially expressed lncRNAs during E. tenella infection in chickens for the first time and provide the direct evidence that lncRNA BTN3A2 regulates the host immune response to coccidia infection.

BTN3A2 Expression Is Connected With Favorable Prognosis and High Infiltrating Immune in Lung Adenocarcinoma

Background: Butyrophilin subfamily 3 member A2 (BTN3A2) is an important mediator in immune activation, and it is reported to be linked to many cancer progresses. However, the relation with infiltrating immune and prognosis of BTN3A2 in lung adenocarcinoma are not clear.

Methods: In our study, we checked the mRNA expression and protein expression profile of BTN3A2 in lung adenocarcinoma (LUAD) and its relation to clinical outcomes using TIMER and UALCAN databases. In addition, we analyzed the survival of BTN3A2 in LUAD using the Kaplan–Meier Plotter database and PrognoScan database. Moreover, we analyzed gene set enrichment analysis (GSEA) of the BTN3A2. Next, we explored the relation of BTN3A2 expression with the immune infiltration by TIMER. At last, in order to enrich the regulatory mechanism of BTN3A2, we used miRarbase, starbase, and miRDB databases to look for miRNA targets of BTN3A2.

Results: The mRNA along with the protein expression of BTN3A2 in the LUAD group was lower than that in the normal group. In addition, high BTN3A2 expression was connected with good first progression (FP) and overall survival (OS) in LUAD. Then, the GSEA analysis demonstrated that T-cell receptor signaling cascade, B-cell receptor signaling cascade, natural killer cell–mediated cytotoxicity, immune receptor activity, immunological synapse, and T-cell activation were enriched differentially in the BTN3A2 high expression phenotype of LUAD. Moreover, BTN3A2 expression is a remarkable positive correlation with invading levels of tumor purity, B cells, neutrophils, CD4+ T cells, dendritic cells, macrophages, and CD8+ T cells in LUAD, and B cells and dendritic cells were linked with a good prognosis of LUAD. To further enrich the possible regulatory mechanisms of BTN3A2, we analyzed the miRNA targets. The results showed that hsa-miR-17-5p may be miRNA targets of BTN3A2.

Conclusion: Taking together, we provide evidence of BTN3A2 as possible prognosis biomarkers of LUAD. In addition, high BTN3A2 expression in LUAD may influence the prognosis because of immune invasion. Moreover, our findings provide a potential mechanism that hsa-miR-17-5p may be miRNA targets of BTN3A2.

Controversial role of γδ T cells in pancreatic cancer

γδ T cells are rare lymphocytes with cogent impact on immune responses. These cells are one of the earliest cells to be recruited in the sites of infection or tumors and play a critical role in coordinating innate and adaptive immune responses. The anti-tumor activity of γδ T cells have been numerously reported; nonetheless, there is controversy among published studies regarding their anti-tumor vs pro-tumor effect- especially in pancreatic cancer. A myriad of studies has confirmed that activated γδ T cells can potently lyse a broad variety of solid tumors and leukemia/lymphoma cells and produce an array of cytokines; however, early γδ T cell-based clinical trials did not lead to optimal efficacy, despite acceptable safety. Depending on the local micromilieu, γδ T cells can differentiate into tumor promoting or suppressing cells such as Th1-, Th2-, or Th17-like cells and produce prototypical cytokines such as interferon-γ (IFNγ) and interleukin (IL)-4/-10, IL-9, or IL-17. In an abstruse tumor such as pancreatic cancer- also known as immunologically cold tumor- γδ T cells are more likely to switch to their immunosuppressive phenotype. In this review we will adduce the accumulated knowledge on these two controversial aspects of γδ T cells in cancers- with a focus on solid tumors and pancreatic cancer. In addition, we propose strategies for enhancing the anti-tumor function of γδ T cells in cancers and discuss the potential future directions.

Involvement of the Intestinal Microbiota in the Appearance of Multiple Sclerosis: Aloe vera and Citrus bergamia as Potential Candidates for Intestinal Health

Multiple sclerosis (MS) is a neurological and inflammatory autoimmune disease of the Central Nervous System in which selective activation of T and B lymphocytes prompts a reaction against myelin, inducing demyelination and axonal loss. Although MS is recognized to be an autoimmune pathology, the specific causes are many; thus, to date, it has been considered a disorder resulting from environmental factors in genetically susceptible individuals. Among the environmental factors hypothetically involved in MS, nutrition seems to be well related, although the role of nutritional factors is still unclear. The gut of mammals is home to a bacterial community of about 2000 species known as the “microbiota”, whose composition changes throughout the life of each individual. There are five bacterial phylas that make up the microbiota in healthy adults: Firmicutes (79.4%), Bacteroidetes (16.9%), Actinobacteria (2.5%), Proteobacteria (1%) and Verrucomicrobia (0.1%). The diversity and abundance of microbial populations justifies a condition known as eubiosis. On the contrary, the state of dysbiosis refers to altered diversity and abundance of the microbiota. Many studies carried out in the last few years have demonstrated that there is a relationship between the intestinal microflora and the progression of multiple sclerosis. This correlation was also demonstrated by the discovery that patients with MS, treated with specific prebiotics and probiotics, have greatly increased bacterial diversity in the intestinal microbiota, which might be otherwise reduced or absent. In particular, natural extracts of Aloe vera and bergamot fruits, rich in polyphenols and with a high percentage of polysaccharides (mostly found in indigestible and fermentable fibers), appear to be potential candidates to re-equilibrate the gut microbiota in MS patients. The present review article aims to assess the pathophysiological mechanisms that reveal the role of the microbiota in the development of MS. In addition, the potential for supplementing patients undergoing early stages of MS with Aloe vera as well as bergamot fibers, on top of conventional drug treatments, is discussed.

Comparing Mouse and Human Tissue-Resident γδ T Cells

Circulating immune cell compartments have been extensively studied for decades, but limited access to peripheral tissue and cell yield have hampered our understanding of tissue-based immunity, especially in γδ T cells. γδ T cells are a unique subset of T cells that are rare in secondary lymphoid organs, but enriched in many peripheral tissues including the skin, uterus, and other epithelial tissues. In addition to immune surveillance activities, recent reports have revealed exciting new roles for γδ T cells in homeostatic tissue physiology in mice and humans. It is therefore important to investigate to what extent the developmental rules described using mouse models transfer to human γδ T cells. Besides, it will be necessary to understand the differences in the development and biogenesis of human and mouse γδ T cells; to understand how γδ T cells are maintained in physiological and pathological circumstances within different tissues, as well as characterize the progenitors of different tissue-resident γδ T cells. Here, we summarize current knowledge of the γδ T phenotype in various tissues in mice and humans, describing the similarities and differences of tissue-resident γδ T cells in mice and humans.

Skin γδ T Cells and Their Function in Wound Healing

For the skin immune system, γδ T cells are important components, which help in defensing against damage and infection of skin. Compared to the conventional αβ T cells, γδ T cells have their own differentiation, development and activation characteristics. In adult mice, dendritic epidermal T cells (DETCs), Vγ4 and Vγ6 γδ T cells are the main subsets of skin, the coordination and interaction among them play a crucial role in wound repair. To get a clear overview of γδ T cells, this review synopsizes their derivation, development, colonization and activation, and focuses their function in acute and chronic wound healing, as well as the underlining mechanism. The aim of this paper is to provide cues for the study of human epidermal γδ T cells and the potential treatment for skin rehabilitation.

Butyrophilins: γδ T Cell Receptor Ligands, Immunomodulators and More

Butyrophilins (BTN) are relatives of the B7 family (e.g., CD80, PD-L1). They fulfill a wide range of functions including immunomodulation and bind to various receptors such as the γδ T cell receptor (γδTCR) and small molecules. One intensively studied molecule is BTN3A1, which binds via its cytoplasmic B30.2 domain, metabolites of isoprenoid synthesis, designated as phosphoantigen (PAg), The enrichment of PAgs in tumors or infected cells is sensed by Vγ9Vδ2 T cells, leading to the proliferation and execution of effector functions to remove these cells. This article discusses the contribution of BTNs, the related BTNL molecules and SKINT1 to the development, activation, and homeostasis of γδ T cells and their immunomodulatory potential, which makes them interesting targets for therapeutic intervention.

Identification of T cell antigens in the 21st century, as difficult as ever

Identifying antigens recognized by T cells is still challenging, particularly for innate like T cells that do not recognize peptides but small metabolites or lipids in the context of MHC-like molecules or see non-MHC restricted antigens. The fundamental reason for this situation is the low affinity of T cell receptors for their ligands coupled with a level of degeneracy that makes them bind to similar surfaces on antigen presenting cells. Herein we will describe non-exhaustively some of the methods that were used to identify peptide antigens and briefly mention the high throughput methods more recently proposed for that purpose. We will then present how the molecules recognized by innate like T cells (NKT, MAIT and γδ T cells) were discovered. We will show that serendipity was instrumental in many cases.

γδ T cell costimulatory ligands in antitumor immunity

Antitumor immunity relies on the ability of T cells to recognize and kill tumor targets. γδ T cells are a specialized subset of T cells that predominantly localizes to non-lymphoid tissue such as the skin, gut, and lung where they are actively involved in tumor immunosurveillance. γδ T cells respond to self-stress ligands that are increased on many tumor cells, and these interactions provide costimulatory signals that promote their activation and cytotoxicity. This review will cover costimulatory molecules that are known to be critical for the function of γδ T cells with a specific focus on mouse dendritic epidermal T cells (DETC). DETC are a prototypic tissue-resident γδ T cell population with known roles in antitumor immunity and are therefore useful for identifying mechanisms that may control activation of other γδ T cell subsets within non-lymphoid tissues. This review concludes with a brief discussion on how γδ T cell costimulatory molecules can be targeted for improved cancer immunotherapy.

Defining the caprine γδ T cell WC1 multigenic array and evaluation of its expressed sequences and gene structure conservation among goat breeds and relative to cattle

Workshop cluster 1 (WC1) molecules are part of the scavenger receptor cysteine-rich (SRCR) superfamily and act as hybrid co-receptors for the γδ T cell receptor and as pattern recognition receptors for binding pathogens. These members of the CD163 gene family are expressed on γδ T cells in the blood of ruminants. While the presence of WC1⁺ γδ T cells in the blood of goats has been demonstrated using monoclonal antibodies, there was no information available about the goat WC1 gene family. The caprine WC1 multigenic array was characterized here for number, structure and expression of genes, and similarity to WC1 genes of cattle and among goat breeds. We found sequence for 17 complete WC1 genes and evidence for up to 30 SRCR a1 or d1 domains which represent distinct signature domains for individual genes. This suggests substantially more WC1 genes than in cattle. Moreover, goats had seven different WC1 gene structures of which 4 are unique to goats. Caprine WC1 genes also had multiple transcript splice variants of their intracytoplasmic domains that eliminated tyrosines shown previously to be important for signal transduction. The most distal WC1 SRCR a1 domains were highly conserved among goat breeds, but fewer were conserved between goats and cattle. Since goats have a greater number of WC1 genes and unique WC1 gene structures relative to cattle, goat WC1 molecules may have expanded functions. This finding may impact research on next-generation vaccines designed to stimulate γδ T cells.

A blend of broadly-reactive and pathogen-selected Vγ4 Vδ1 T cell receptors confer broad bacterial reactivity of resident memory γδ T cells

Although murine γδ T cells are largely considered innate immune cells, they have recently been reported to form long-lived memory populations. Much remains unknown about the biology and specificity of memory γδ T cells. Here, we interrogated intestinal memory Vγ4 Vδ1 T cells generated after foodborne Listeria monocytogenes (Lm) infection to uncover an unanticipated complexity in the specificity of these cells. Deep TCR sequencing revealed that a subset of non-canonical Vδ1 clones are selected by Lm infection, consistent with antigen-specific clonal expansion. Ex vivo stimulations and in vivo heterologous challenge infections with diverse pathogenic bacteria revealed that Lm-elicited memory Vγ4 Vδ1 T cells are broadly reactive. The Vγ4 Vδ1 T cell recall response to Lm, Salmonella enterica serovar Typhimurium (STm) and Citrobacter rodentium was largely mediated by the γδTCR as internalizing the γδTCR prevented T cell expansion. Both broadly-reactive canonical and pathogen-selected non-canonical Vδ1 clones contributed to memory responses to Lm and STm. Interestingly, some non-canonical γδ T cell clones selected by Lm infection also responded after STm infection, suggesting some level of cross-reactivity. These findings underscore the promiscuous nature of memory γδ T cells and suggest that pathogen-elicited memory γδ T cells are potential targets for broad-spectrum anti-infective vaccines.

The Contribution of Human Herpes Viruses to γδ T Cell Mobilisation in Co-Infections

γδ T cells are activated in viral, bacterial and parasitic infections. Among viruses that promote γδ T cell mobilisation in humans, herpes viruses (HHVs) occupy a particular place since they infect the majority of the human population and persist indefinitely in the organism in a latent state. Thus, other infections should, in most instances, be considered co-infections, and the reactivation of HHV is a serious confounding factor in attributing γδ T cell alterations to a particular pathogen in human diseases. We review here the literature data on γδ T cell mobilisation in HHV infections and co-infections, and discuss the possible contribution of HHVs to γδ alterations observed in various infectious settings. As multiple infections seemingly mobilise overlapping γδ subsets, we also address the concept of possible cross-protection.

Our evolving understanding of the role of the γδ T cell receptor in γδ T cell mediated immunity

The γδ T cell immune cell lineage has remained relatively enigmatic and under-characterised since their identification. Conversely, the insights we have, highlight their central importance in diverse immunological roles and homeostasis. Thus, γδ T cells are considered as potentially a new translational tool in the design of new therapeutics for cancer and infectious disease. Here we review our current understanding of γδ T cell biology viewed through a structural lens centred on the how the γδ T cell receptor mediates ligand recognition. We discuss the limited knowledge of antigens, the structural basis of such reactivities and discuss the emerging trends of γδ T cell reactivity and implications for γδ T cell biology.

Innate immune genes of the chicken MHC and related regions

Compared to the major histocompatibility complex (MHC) of typical mammals, the chicken BF/BL region is small and simple, with most of the genes playing central roles in the adaptive immune response. However, some genes of the chicken MHC are almost certainly involved in innate immunity, such as the complement component C4 and the lectin-like receptor/ligand gene pair BNK and Blec. The poorly expressed classical class I molecule BF1 is known to be recognised by natural killer (NK) cells and, analogous to mammalian immune responses, the classical class I molecules BF1 and BF2, the CD1 homologs and the butyrophilin homologs called BG may be recognised by adaptive immune lymphocytes with semi-invariant receptors in a so-called adaptate manner. Moreover, the TRIM and BG regions next to the chicken MHC, along with the genetically unlinked Y and olfactory/scavenger receptor regions on the same chromosome, have multigene families almost certainly involved in innate and adaptate responses. On this chicken microchromosome, the simplicity of the adaptive immune gene systems contrasts with the complexity of the gene systems potentially involved in innate immunity.

Development of ICT01, a first-in-class, anti-BTN3A antibody for activating Vγ9Vδ2 T cell-mediated antitumor immune response

[Figure: see text].

BTN2A2 protein negatively regulates T cells to ameliorate collagen-induced arthritis in mice

Rheumatoid arthritis (RA) is an autoimmune disorder characterized by persistent inflammatory responses in target tissues and organs, resulting in the destruction of joints. Collagen type II (CII)-induced arthritis (CIA) is the most used animal model for human RA. Although BTN2A2 protein has been previously shown to inhibit T cell functions in vitro, its effect on autoimmune arthritis has not been reported. In this study, we investigate the ability of a recombinant BTN2A2-IgG2a Fc (BTN2A2-Ig) fusion protein to treat CIA. We show here that administration of BTN2A2-Ig attenuates established CIA, as compared with control Ig protein treatment. This is associated with reduced activation, proliferation and Th1/Th17 cytokine production of T cells in BTN2A2-Ig-treated CIA mice. BTN2A2-Ig also inhibits CII-specific T cell proliferation and Th1/Th17 cytokine production. Although the percentage of effector T cells is decreased in BTN2A2-Ig-treated CIA mice, the proportions of naive T cells and regulatory T cells is increased. Furthermore, BTN2A2-Ig reduces the percentage of proinflammatory M1 macrophages but increases the percentage of anti-inflammatory M2 macrophages in the CIA mice. Our results suggest that BTN2A2-Ig protein has the potential to be used in the treatment of collagen-induced arthritis models.

Listeria monocytogenes-infected human monocytic derived dendritic cells activate Vγ9Vδ2 T cells independently of HMBPP production

Gamma-delta (γδ) T cells express T cell receptors (TCR) that are preconfigured to recognize signs of pathogen infection. In primates, γδ T cells expressing the Vγ9Vδ2 TCR innately recognize (E)-4-hydroxy-3-methyl-but- 2-enyl pyrophosphate (HMBPP), a product of the 2-C-methyl-D-erythritol 4- phosphate (MEP) pathway in bacteria that is presented in infected cells via interaction with members of the B7 family of costimulatory molecules butyrophilin (BTN) 3A1 and BTN2A1. In humans, Listeria monocytogenes (Lm) vaccine platforms have the potential to generate potent Vγ9Vδ2 T cell recognition. To evaluate the activation of Vγ9Vδ2 T cells by Lm-infected human monocyte-derived dendritic cells (Mo-DC) we engineered Lm strains that lack components of the MEP pathway. Direct infection of Mo-DC with these bacteria were unchanged in their ability to activate CD107a expression in Vγ9Vδ2 T cells despite an inability to synthesize HMBPP. Importantly, functional BTN3A1 was essential for this activation. Unexpectedly, we found that cytoplasmic entry of Lm into human dendritic cells resulted in upregulation of cholesterol metabolism in these cells, and the effect of pathway regulatory drugs suggest this occurs via increased synthesis of the alternative endogenous Vγ9Vδ2 ligand isoprenyl pyrophosphate (IPP) and/or its isomer dimethylallyl pyrophosphate (DMAPP). Thus, following direct infection, host pathways regulated by cytoplasmic entry of Lm can trigger Vγ9Vδ2 T cell recognition of infected cells without production of the unique bacterial ligand HMBPP.

New Insights into Asthma Inflammation: Focus on iNKT, MAIT, and γδT Cells

Asthma is a chronic immunological disease affecting all age groups, but often starting in childhood. Although it has long been ascribed to a single pathology, recent studies have highlighted its heterogeneity due to the potential involvement of various pathogenic mechanisms. Here, we present our current understanding of the role of innate-like T (ILT) cells in asthma pathogenesis. These cells constitute a specific family mainly comprising γδT, invariant natural killer (iNKT) and mucosal-associated invariant (MAIT) T cells. They all share the ability to massively secrete a wide range of cytokines in a T-cell receptor (TCR)-dependent or -independent manner. ILT cells are prevalent in mucosal tissues, including airways, where their innate and adaptive immune functions consist primarily in protecting tissue integrity. However, ILT cells may also have detrimental effects leading to asthma symptoms. The immune mechanisms through which this pathogenic effect occurs will be discussed in this overview.

Butyrophilin-like 2 regulates site-specific adaptations of intestinal γδ intraepithelial lymphocytes

Tissue-resident γδ intraepithelial lymphocytes (IELs) orchestrate innate and adaptive immune responses to maintain intestinal epithelial barrier integrity. Epithelia-specific butyrophilin-like (Btnl) molecules induce perinatal development of distinct Vγ TCR⁺ IELs, however, the mechanisms that control γδ IEL maintenance within discrete intestinal segments are unclear. Here, we show that Btnl2 suppressed homeostatic proliferation of γδ IELs preferentially in the ileum. High throughput transcriptomic characterization of site-specific Btnl2-KO γδ IELs reveals that Btnl2 regulated the antimicrobial response module of ileal γδ IELs. Btnl2 deficiency shapes the TCR specificities and TCRγ/δ repertoire diversity of ileal γδ IELs. During DSS-induced colitis, Btnl2-KO mice exhibit increased inflammation and delayed mucosal repair in the colon. Collectively, these data suggest that Btnl2 fine-tunes γδ IEL frequencies and TCR specificities in response to site-specific homeostatic and inflammatory cues. Hence, Btnl-mediated targeting of γδ IEL development and maintenance may help dissect their immunological functions in intestinal diseases with segment-specific manifestations.

Panea et al showed that epithelia-specific butyrophilinlike 2 (Btnl2) suppressed homeostatic proliferation of γδ intraepithelial lymphocytes (IELs) preferentially in the ileum and used high throughput transcriptomic characterization of Btnl2-deficient γδ IELs to demonstrate that Btnl2 impacts γδ TCR specificities and repertoire diversity of ileal γδ IELs. In addition, they showed that Btnl2-deficient mice exhibited increased inflammation and delayed mucosal repair in the colon, suggesting that it plays a key immunological function in intestinal diseases.