Cytokine requirements for the differentiation and expansion of IL-17A- and IL-22-producing human Vgamma2Vdelta2 T cells

Key players of immunosuppression in epithelial malignancies: Tumor-infiltrating myeloid cells and γδ T cells

BACKGROUND

The tumor microenvironment of solid tumors governs the differentiation of otherwise non-immunosuppressive macrophages and gamma delta (γδ) T cells into strong immunosuppressors while promoting suppressive abilities of known immunosuppressors such as myeloid-derived suppressor cells (MDSCs) upon infiltration into the tumor beds.

RECENT FINDINGS

In epithelial malignancies, tumor-associated macrophages (TAMs), precursor monocytic MDSCs (M-MDSCs), and gamma delta (γδ) T cells often acquire strong immunosuppressive abilities that dampen spontaneous immune responses by tumor-infiltrating T cells and B lymphocytes against cancer. Both M-MDSCs and γδ T cells have been associated with worse prognosis for multiple epithelial cancers.

CONCLUSION

Here we discuss recent discoveries on how tumor-associated macrophages and precursor M-MDSCs as well as tumor associated-γδ T cells acquire immunosuppressive abilities in the tumor beds, promote cancer metastasis, and perspectives on how possible novel interventions could restore the effective adaptive immune responses in epithelial cancers.

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.

Dominance and improved survivability of human γδT17 cell subset aggravates the immunopathogenesis of pemphigus vulgaris

Human γδ T cells are highly enriched in epithelial cell-dominated compartments like skin. Nonetheless, their function in the pathogenesis of pemphigus vulgaris (PV), an autoimmune skin disorder, is lacking. Therefore, we investigated the functional expression of human γδT cell subsets along with their homing chemokine receptor-ligand and inflammatory cytokines in the immunopathogenesis of PV. Estimation of the frequency of γδT cell subsets by flow cytometry revealed four major subsets of γδ T cells (γδT1, γδT2, γδT17, γδTreg) in both control and PV circulation. The elevated frequency of γδT17 cells producing IL17 and expressing CCR6 receptor suggests their inflammatory and migratory potential in PV. In vitro culture of γδ T cells from patients showed increased mRNA expression of inflammatory cytokines IL17, RORγt, IL23, IL1, and co-stimulatory markers, CD27 and CD70. These findings correlated the role of IL1 and IL23 cytokines that alleviate the Th17 population in PV. Cytotoxic activities of γδ T cells were higher and inflammatory γδT17 cells were localized in the skin of PV whereas γδTreg cells associated TGFβ and FOXP3 were lowered. Hyperinflammatory phenotype of the γδT17 cell subset and its migratory potential might be aiding in the pathogenesis of PV, whereas γδTreg cells fail to suppress these inflammatory responses. Hence, γδT17 cell-associated markers can be targeted for identifying novel therapeutics in PV.

Expansion and Polarization of Human γδT17 Cells in vitro from Peripheral Blood Mononuclear Cells

γδ T cells play a critical role in homeostasis and diseases such as infectious diseases and tumors in both mice and humans. They can be categorized into two main functional subsets: IFN-γ-producing γδT1 cells and IL-17-producing γδT17 cells. While CD27 expression segregates these two subsets in mice, little is known about human γδT17 cell differentiation and expansion. Previous studies have identified γδT17 cells in human skin and mucosal tissues, including the oral cavity and colon. However, human γδ T cells from peripheral blood mononuclear cells (PBMCs) primarily produce IFN-γ. In this protocol, we describe a method for in vitro expansion and polarization of human γδT17 cells from PBMCs. Key Features • Expansion of γδ T cells from peripheral blood mononuclear cells. • Human IL-17A-producing γδ T-cell differentiation and expansion using IL-7 and anti-γδTCR. • Analysis of IL-17A production post γδ T-cell expansion. This protocol is used in: Science Advances (2022), DOI: 10.1126/sciadv.abm9120.

Tyrosine Kinase Inhibition Activates Intratumoral γδ T Cells in Gastrointestinal Stromal Tumor

γδ T cells are a rare but potent subset of T cells with pleiotropic functions. They commonly reside within tumors but the response of γδ T cells to tyrosine kinase inhibition is unknown. To address this, we studied a genetically engineered mouse model of gastrointestinal stromal tumor (GIST) driven by oncogenic Kit signaling that responds to the Kit inhibitor imatinib. At baseline, γδ T cells were antitumoral, as blockade of either γδ T-cell receptor or IL17A increased tumor weight and decreased antitumor immunity. However, imatinib therapy further stimulated intratumoral γδ T cells, as determined by flow cytometry and single-cell RNA sequencing (scRNA-seq). Imatinib expanded a highly activated γδ T-cell subset with increased IL17A production and higher expression of immune checkpoints and cytolytic effector molecules. Consistent with the mouse model, γδ T cells produced IL17A in fresh human GIST specimens, and imatinib treatment increased γδ T-cell gene signatures, as measured by bulk tumor RNA-seq. Furthermore, tumor γδ T cells correlated with survival in patients with GIST. Our findings highlight the interplay between tumor cell oncogene signaling and antitumor immune responses and identify γδ T cells as targets for immunotherapy in GIST.

The role of γδ T cells in the immunopathogenesis of inflammatory diseases: from basic biology to therapeutic targeting

The γδ T cells are lymphocytes with an innate-like phenotype that can distribute to different tissues to reside and participate in homeostatic functions such as pathogen defense, tissue modeling, and response to stress. These cells originate during fetal development and migrate to the tissues in a TCR chain-dependent manner. Their unique manner to respond to danger signals facilitates the initiation of cytokine-mediated diseases such as spondyloarthritis and psoriasis, which are immune-mediated diseases with a very strong link with mucosal disturbances, either in the skin or the gut. In spondyloarthritis, γδ T cells are one of the main sources of IL-17 and, therefore, the main drivers of inflammation and probably new bone formation. Remarkably, this population can be the bridge between gut and joint inflammation.

CXCL10 Recruitment of γδ T Cells into the Hypoxic Bone Marrow Environment Leads to IL17 Expression and Multiple Myeloma Progression

In multiple myeloma (MM), bone marrow stromal cells (BMSC) shape a unique niche within the bone marrow, promoting T-cell dysfunction and driving MM progression; however, the precise underlying mechanisms remain elusive. Here, we show that BMSC-mediated reprogramming of MM cells led to heightened production of CXCL10. CXCL10 orchestrated the recruitment of γδ T cells into the bone marrow, and this was observed in both the Vk*MYC and 5TGM1 mouse models of MM, as well as in patients experiencing refractory or relapsed MM. Furthermore, the dysfunctional γδ T cells in the MM bone marrow niche exhibited increased PD-1 expression and IL17 production. In the Vk*MYC mouse model, MM-associated bone lesions and mortality were markedly alleviated in Tcrd-/- mice, and MM disease progression could be rescued in these mice upon transplantation of γδ T cells expanded from wild-type mice, but not from Il17-/- mice. Mechanistically, the hypoxic microenvironment prevailing in the MM bone marrow niche stimulated the expression of steroid receptor coactivator 3 (SRC-3) in γδ T cells, which in turn interacted with the transcriptional factor RORγt, promoting Il17 transcription. Pharmacologic inhibition of SRC-3 utilizing SI-2 effectively suppressed Il17A expression in γδ T cells, leading to alleviation of MM progression in the murine models and enhancing the anti-multiple myeloma efficacy of bortezomib. Our results illuminated the bone marrow microenvironment's involvement in provoking γδ T-cell dysfunction throughout MM progression and suggest SRC-3 inhibition as a promising strategy to enhance the effectiveness of immunotherapies targeting γδ T cells.

The tumor microenvironment generated by Marek's disease virus suppresses interferon-gamma-producing gamma delta T cells

The tumor microenvironment (TME) is generated by the cross-talk among tumor cells, immune system cells, and stromal cells. The TME generated by Marek's disease virus (MDV) is suggested to display an immunosuppressive milieu due to immune inhibitory molecules and cytokines which are possibly induced by MDV-transformed cells and regulatory T cells. Both anti-tumor and pro-tumor gamma delta (γδ) T cells are reported in human cancer. Although anti-tumor like and pro-tumor like γδ T cells are found in MDV-infected chickens at the later phase of infection, how the TME affects circulating and tissue-resident γδ T cells has not been investigated. Here, we demonstrated that the supernatant of the cultured splenocytes derived from MDV-challenegd chickens inhibited interferon (IFN)-γ production and CD25 expression by T cell receptor (TCR)γδ-stimulated tissue-resident γδ T cells, but the supernatant of the cultured MDV-transformed cell line did not affect γδ T cell activation. TCRγδ-stimulated circulating γδ T cells were influenced neither by the supernatant of the cultured splenocytes derived from MDV-challenegd chickens nor by the supernatant of the cultured MDV-transformed cell line. Taken together, activation and IFN-γ production by tissue-resident γδ T cells can be inhibited in the TME generated by MDV while tumor attracted circulating γδ T cells may not be influenced in activation and IFN-γ production by the TME generated by MDV.

Human gamma-delta (γδ) T cell therapy for glioblastoma: A novel alternative to overcome challenges of adoptive immune cell therapy

Glioblastoma is the most common brain malignancy with devastating prognosis. Numerous clinical trials using various target therapeutic agents have failed and recent clinical trials using check point inhibitors also failed to provide survival benefits for glioblastoma patients. Adoptive T cell transfer is suggested as a novel therapeutic approach that has exhibited promise in preliminary clinical studies. However, the clinical outcomes are inconsistent, and there are several limitations of current adoptive T cell transfer strategies for glioblastoma treatment. As an alternative cell therapy, gamma-delta (γδ) T cells have been recently introduced for several cancers including glioblastoma. Since the leading role of γδ T cells is immune surveillance by recognizing a broad range of ligands including stress molecules, phosphoantigens, or lipid antigens, recent studies have suggested the potential benefits of γδ T cell transfer against glioblastomas. However, γδ T cells, as a small subset (1-5%) of T cells in human peripheral blood, are relatively unknown compared to conventional alpha-beta (αβ) T cells. In this context, our study introduced γδ T cells as an alternative and novel option to overcome several challenges regarding immune cell therapy in glioblastoma treatment. We described the unique characteristics and advantages of γδ T cells compared to conventional αβ T cells and summarize several recent preclinical studies using human gamma-delta T cell therapy for glioblastomas. Finally, we suggested future direction of human γδ T cell therapy for glioblastomas.

Exhausted intratumoral Vδ2- γδ T cells in human kidney cancer retain effector function

Gamma delta (γδ) T cells reside within human tissues including tumors, but their function in mediating antitumor responses to immune checkpoint inhibition is unknown. Here we show that kidney cancers are infiltrated by Vδ2- γδ T cells, with equivalent representation of Vδ1+ and Vδ1- cells, that are distinct from γδ T cells found in normal human tissues. These tumor-resident Vδ2- T cells can express the transcriptional program of exhausted αβ CD8+ T cells as well as canonical markers of terminal T-cell exhaustion including PD-1, TIGIT and TIM-3. Although Vδ2- γδ T cells have reduced IL-2 production, they retain expression of cytolytic effector molecules and co-stimulatory receptors such as 4-1BB. Exhausted Vδ2- γδ T cells are composed of three distinct populations that lack TCF7, are clonally expanded and express cytotoxic molecules and multiple Vδ2- T-cell receptors. Human tumor-derived Vδ2- γδ T cells maintain cytotoxic function and pro-inflammatory cytokine secretion in vitro. The transcriptional program of Vδ2- T cells in pretreatment tumor biopsies was used to predict subsequent clinical responses to PD-1 blockade in patients with cancer. Thus, Vδ2- γδ T cells within the tumor microenvironment can contribute to antitumor efficacy.

Phenotypic and functional characterization of pharmacologically expanded Vγ9Vδ2 T cells in pigtail macaques

While gaining interest as treatment for cancer and infectious disease, the clinical efficacy of Vγ9Vδ2 T cell-based immunotherapeutics has to date been limited. An improved understanding of γδ T cell heterogeneity across lymphoid and non-lymphoid tissues, before and after pharmacological expansion, is required. Here, we describe the phenotype and tissue distribution of Vγ9Vδ2 T cells at steady state and following in vivo pharmacological expansion in pigtail macaques. Intravenous phosphoantigen administration with subcutaneous rhIL-2 drove robust expansion of Vγ9Vδ2 T cells in blood and pulmonary mucosa, while expansion was confined to the pulmonary mucosa following intratracheal antigen administration. Peripheral blood Vγ9Vδ2 T cell expansion was polyclonal, and associated with a significant loss of CCR6 expression due to IL-2-mediated receptor downregulation. Overall, we show the tissue distribution and phenotype of in vivo pharmacologically expanded Vγ9Vδ2 T cells can be altered based on the antigen administration route, with implications for tissue trafficking and the clinical efficacy of Vγ9Vδ2 T cell immunotherapeutics.

Kidney-resident innate-like memory γδ T cells control chronic Staphylococcus aureus infection of mice

γδ T cells are involved in the control of Staphylococcus aureus infection, but their importance in protection compared to other T cells is unclear. We used a mouse model of systemic S. aureus infection associated with high bacterial load and persistence in the kidney. Infection caused fulminant accumulation of γδ T cells in the kidney. Renal γδ T cells acquired tissue residency and were maintained in high numbers during chronic infection. At day 7, up to 50% of renal γδ T cells produced IL-17A in situ and a large fraction of renal γδ T cells remained IL-17A⁺ during chronic infection. Controlled depletion revealed that γδ T cells restricted renal S. aureus replication in the acute infection and provided protection during chronic renal infection and upon reinfection. Our results demonstrate that kidney-resident γδ T cells are nonredundant in limiting local S. aureus growth during chronic infection and provide enhanced protection against reinfection.

Lipid metabolic features of T cells in the Tumor Microenvironment

The tumor microenvironment (TME) is characterized by discrete changes in metabolic features of cancer and immune cells, with various implications. Cancer cells take up most of the available glucose to support their growth, thereby leaving immune cells with insufficient nutrients to expand. In the relative absence of glucose, T cells switch the metabolic program to lipid-based sources, which is pivotal to T-cell differentiation and activation in nutrient-stressed TME. Although consumption of lipids should provide an alternative energy source to starving T cells, a literature survey has revealed that it may not necessarily lead to antitumor responses. Different subtypes of T cells behave differently in various lipid overload states, which widely depends upon the kind of free fatty acids (FFA) engulfed. Key lipid metabolic genes provide cytotoxic T cells with necessary nutrients for proliferation in the absence of glucose, thereby favoring antitumor immunity, but the same genes cause immune evasion in T_mem and T_reg. This review aims to detail the complexity of differential lipid metabolism in distinct subtypes of T cells that drive the antitumor or pro-tumor immunity in specific TME states. We have identified key drug targets related to lipid metabolic rewiring in TME.

γδ T, NKT, and MAIT Cells During Evolution: Redundancy or Specialized Functions?

Innate-like T cells display characteristics of both innate lymphoid cells (ILCs) and mainstream αβ T cells, leading to overlapping functions of innate-like T cells with both subsets. In this review, we show that although innate-like T cells are probably present in all vertebrates, their main characteristics are much better known in amphibians and mammals. Innate-like T cells encompass both γδ and αβ T cells. In mammals, γδ TCRs likely coevolved with molecules of the butyrophilin family they interact with, whereas the semi-invariant TCRs of iNKT and mucosal-associated invariant T cells are evolutionarily locked with their restricting MH1b molecules, CD1d and MR1, respectively. The strong conservation of the Ag recognition systems of innate-like T cell subsets despite similar effector potentialities supports that each one fulfills nonredundant roles related to their Ag specificity.

Bacillus Calmette-Guerin (BCG) induces superior anti-tumour responses by Vδ2+ T cells compared with the aminobisphosphonate drug zoledronic acid

Vδ2⁺ T cells can recognize malignantly transformed cells as well as those infected with mycobacteria. This cross-reactivity supports the idea of using mycobacteria to manipulate Vδ2⁺ T cells in cancer immunotherapy. To date, therapeutic interventions using Vδ2⁺ T cells in cancer have involved expanding these cells in or ex vivo using zoledronic acid (ZA). Here, we show that the mycobacterium Bacillus Calmette–Guérin (BCG) also causes Vδ2⁺ T-cell expansion in vitro and that resulting Vδ2⁺ cell populations are cytotoxic toward tumour cell lines. We show that both ZA and BCG-expanded Vδ2+ cells effectively killed both Daudi and THP-1 cells. THP-1 cell killing by both ZA and BCG-expanded Vδ2+ cells was enhanced by treatment of targets cells with ZA. Although no difference in cytotoxic activity between ZA- and BCG-expanded Vδ2+ cells was observed, BCG-expanded cells degranulated more and produced a more diverse range of cytokines upon tumour cell recognition compared to ZA-expanded cells. ZA-expanded Vδ2+ cells were shown to upregulate exhaustion marker CD57 to a greater extent than BCG-expanded Vδ2+ cells. Furthermore, ZA expansion was associated with upregulation of inhibitory markers PD-1 and TIM3 in a dose-dependent manner whereas PD-1 expression was not increased following expansion using BCG. Intradermal BCG vaccination of rhesus macaques caused in vivo expansion of Vδ2⁺ cells. In combination with the aforementioned in vitro data, this finding suggests that BCG treatment could induce expansion of Vδ2⁺ T cells with enhanced anti-tumour potential compared to ZA treatment and that either ZA or BCG could be used intratumourally as a means to potentiate stronger anti-tumour Vδ2⁺ T-cell responses.

IgG from Adult Atopic Dermatitis (AD) Patients Induces Nonatopic Neonatal Thymic Gamma-Delta T Cells (γδT) to Acquire IL-22/IL-17 Secretion Profile with Skin-Homing Properties and Epigenetic Implications Mediated by miRNA

γδT cells mature in the human thymus, and mainly produce IL-17A or IFN-γ, but can also produce IL-22 and modulate a variety of immune responses. Here, we aimed to evaluate whether IgG from AD patients (AD IgG) can functionally modulate thymic nonatopic γδT cells. Thymic tissues were obtained from 12 infants who had not had an atopic history. Thymocytes were cultured in mock condition, or in the presence of either AD IgG or therapeutic intravenous IgG (IVIg). Following these treatments, intracellular cytokine production, phenotype, and microRNA expression profiles were investigated. AD IgG could downregulate α4β7, upregulate CLA, and induce the production of IFN-γ, IL-17, and IL-22 in γδT cells. Although both AD IgG and IVIg could directly interact with γδT cell membranes, AD IgG could reduce γδT cell apoptosis. AD IgG could upregulate nine miRNAs compared to IVIg, and six when compared to the mock condition. In parallel, some miRNAs were downregulated. Target gene prediction and functional analysis indicated that some target genes were enriched in the negative regulation of cellular transcription. This study shows that AD IgG influences the production of IL-17 and IL-22 by intrathymic nonatopic γδT cells, and demonstrates epigenetic implications mediated by miRNAs.

Targeting Cytokine Signals to Enhance γδT Cell-Based Cancer Immunotherapy

γδT cells represent a small percentage of T cells in circulation but are found in large numbers in certain organs. They are considered to be innate immune cells that can exert cytotoxic functions on target cells without MHC restriction. Moreover, γδT cells contribute to adaptive immune response via regulating other immune cells. Under the influence of cytokines, γδT cells can be polarized to different subsets in the tumor microenvironment. In this review, we aimed to summarize the current understanding of antigen recognition by γδT cells, and the immune regulation mediated by γδT cells in the tumor microenvironment. More importantly, we depicted the polarization and plasticity of γδT cells in the presence of different cytokines and their combinations, which provided the basis for γδT cell-based cancer immunotherapy targeting cytokine signals.

A local human Vδ1 T cell population is associated with survival in nonsmall-cell lung cancer

Murine tissues harbor signature γδ T cell compartments with profound yet differential impacts on carcinogenesis. Conversely, human tissue-resident γδ cells are less well defined. In the present study, we show that human lung tissues harbor a resident Vδ1 γδ T cell population. Moreover, we demonstrate that Vδ1 T cells with resident memory and effector memory phenotypes were enriched in lung tumors compared with nontumor lung tissues. Intratumoral Vδ1 T cells possessed stem-like features and were skewed toward cytolysis and helper T cell type 1 function, akin to intratumoral natural killer and CD8+ T cells considered beneficial to the patient. Indeed, ongoing remission post-surgery was significantly associated with the numbers of CD45RA-CD27- effector memory Vδ1 T cells in tumors and, most strikingly, with the numbers of CD103+ tissue-resident Vδ1 T cells in nonmalignant lung tissues. Our findings offer basic insights into human body surface immunology that collectively support integrating Vδ1 T cell biology into immunotherapeutic strategies for nonsmall cell lung cancer.

Differential metabolic requirement governed by transcription factor c-Maf dictates innate γδT17 effector functionality in mice and humans

Cellular metabolism has been proposed to govern distinct γδ T cell effector functions, but the underlying molecular mechanisms remain unclear. We show that interleukin-17 (IL-17)-producing γδ T (γδT17) and interferon-γ (IFN-γ)-producing γδ T (γδT1) cells have differential metabolic requirements and that the rate-limiting enzyme isocitrate dehydrogenase 2 (IDH2) acts as a metabolic checkpoint for their effector functions. Intriguingly, the transcription factor c-Maf regulates γδT17 effector function through direct regulation of IDH2 promoter activity. Moreover, mTORC2 affects the expression of c-Maf and IDH2 and subsequent IL-17 production in γδ T cells. Deletion of c-Maf in γδ T cells reduces metastatic lung cancer development, suggesting c-Maf as a potential target for cancer immune therapy. We show that c-Maf also controls IL-17 production in human γδ T cells from peripheral blood and in oral cancers. These results demonstrate a critical role of the transcription factor c-Maf in regulating γδT17 effector function through IDH2-mediated metabolic reprogramming.

MAIT and Vδ2 unconventional T cells are supported by a diverse intestinal microbiome and correlate with favorable patient outcome after allogeneic HCT

Microbial diversity is associated with improved outcomes in recipients of allogeneic hematopoietic cell transplantation (allo-HCT), but the mechanism underlying this observation is unclear. In a cohort of 174 patients who underwent allo-HCT, we demonstrate that a diverse intestinal microbiome early after allo-HCT is associated with an increased number of innate-like mucosal-associated invariant T (MAIT) cells, which are in turn associated with improved overall survival and less acute graft-versus-host disease (aGVHD). Immune profiling of conventional and unconventional immune cell subsets revealed that the prevalence of Vδ2 cells, the major circulating subpopulation of γδ T cells, closely correlated with the frequency of MAIT cells and was associated with less aGVHD. Analysis of these populations using both single-cell transcriptomics and flow cytometry suggested a shift toward activated phenotypes and a gain of cytotoxic and effector functions after transplantation. A diverse intestinal microbiome with the capacity to produce activating ligands for MAIT and Vδ2 cells appeared to be necessary for the maintenance of these populations after allo-HCT. These data suggest an immunological link between intestinal microbial diversity, microbe-derived ligands, and maintenance of unconventional T cells.

Population Pharmacokinetics Analysis of Guselkumab in Healthy Subjects and Patients with Psoriatic Arthritis, Plaque Psoriasis, and Palmoplantar Pustulosis

AIM

Guselkumab, a monoclonal antibody that binds to the p19 subunit of interleukin 23, is approved for the treatment of plaque psoriasis (PsO) and psoriatic arthritis (PsA), palmoplantar pustulosis (PPP), generalized pustular psoriasis, and erythrodermic psoriasis in various countries. The purpose of this analysis was to develop a comprehensive population pharmacokinetic (PK) model for guselkumab to determine whether PK differs across different disease populations and healthy subjects.

METHODS

A non-linear mixed-effects modeling approach was used to analyze 23,097 serum PK samples obtained from 2,623 healthy subjects and patients with PsO, PsA, and PPP across nine phase I-III clinical trials.

RESULTS

Guselkumab concentrations were adequately described by a 2-compartment linear PK model with first-order absorption and elimination. Clearance (CL), central and peripheral volume of distribution, inter-compartmental flow, absorption rate constant, and absolute bioavailability estimates were 0.255 L/day, 3.60 L, 1.78 L, 0.369 L/day, 0.313 day^-1 , and 49.2%, respectively, for a subject weighing 70 kg. Terminal half-life was estimated to be approximately 14.6 days. Body weight was the primary factor affecting CL and central volume of distribution. CL of guselkumab was similar among patients with PsA, PsO, and PPP, but CL in disease populations was 11%-17% lower than that in healthy subjects after other covariate effects such as body weight were accounted for.

CONCLUSION

The population pharmacokinetic analysis indicated that, after other covariate effects were taken into account, patients with PsO, PsA, and PPP had similar PK characteristics, with CL in these disease populations being slightly lower than healthy individuals.

γδ T Cells Activated in Different Inflammatory Environments Are Functionally Distinct

γδ T cells are important immunoregulatory cells in experimental autoimmune uveitis (EAU), and the activation status of γδ T cells determines their disease-enhancing or inhibitory effects. Because γδ T cells can be activated via various pathways, we questioned whether the nature of their activation might impact their function. In this study, we show that γδ T cells activated under different inflammatory conditions differ greatly in their functions. Whereas anti-CD3 treatment activated both IFN-γ⁺ and IL-17⁺ γδ T cells, cytokines preferentially activated IL-17⁺ γδ T cells. γδ T cells continued to express high levels of surface CD73 after exposure to inflammatory cytokines, but they downregulated surface CD73 after exposure to dendritic cells. Although both CD73^high and CD73^low cells have a disease-enhancing effect, the CD73^low γδ T cells are less inhibitory. We also show that polarized activation not only applies to αβ T cells and myeloid cells, but also to γδ T cells. After activation under Th17-polarizing conditions, γδ T cells predominantly expressed IL-17 (gdT17), but after activation under Th1 polarizing conditions (gdT1) they mainly expressed IFN-γ. The pro-Th17 activity of γδ T cells was associated with gdT17, but not gdT1. Our results demonstrate that the functional activity of γδ T cells is strikingly modulated by their activation level, as well as the pathway through which they were activated.

TGF-β1 potentiates Vγ9Vδ2 T cell adoptive immunotherapy of cancer

Despite its role in cancer surveillance, adoptive immunotherapy using γδ T cells has achieved limited efficacy. To enhance trafficking to bone marrow, circulating Vγ9Vδ2 T cells are expanded in serum-free medium containing TGF-β1 and IL-2 (γδ[T2] cells) or medium containing IL-2 alone (γδ[2] cells, as the control). Unexpectedly, the yield and viability of γδ[T2] cells are also increased by TGF-β1, when compared to γδ[2] controls. γδ[T2] cells are less differentiated and yet display increased cytolytic activity, cytokine release, and antitumor activity in several leukemic and solid tumor models. Efficacy is further enhanced by cancer cell sensitization using aminobisphosphonates or Ara-C. A number of contributory effects of TGF-β are described, including prostaglandin E2 receptor downmodulation, TGF-β insensitivity, and upregulated integrin activity. Biological relevance is supported by the identification of a favorable γδ[T2] signature in acute myeloid leukemia (AML). Given their enhanced therapeutic activity and compatibility with allogeneic use, γδ[T2] cells warrant evaluation in cancer immunotherapy.

The Diverse Roles of γδ T Cells in Cancer: From Rapid Immunity to Aggressive Lymphoma

γδ T cells are unique players in shaping immune responses, lying at the intersection between innate and adaptive immunity. Unlike conventional αβ T cells, γδ T cells largely populate non-lymphoid peripheral tissues, demonstrating tissue specificity, and they respond to ligands in an MHC-independent manner. γδ T cells display rapid activation and effector functions, with a capacity for cytotoxic anti-tumour responses and production of inflammatory cytokines such as IFN-γ or IL-17. Their rapid cytotoxic nature makes them attractive cells for use in anti-cancer immunotherapies. However, upon transformation, γδ T cells can give rise to highly aggressive lymphomas. These rare malignancies often display poor patient survival, and no curative therapies exist. In this review, we discuss the diverse roles of γδ T cells in immune surveillance and response, with a particular focus on cancer immunity. We summarise the intriguing dichotomy between pro- and anti-tumour functions of γδ T cells in solid and haematological cancers, highlighting the key subsets involved. Finally, we discuss potential drivers of γδ T-cell transformation, summarising the main γδ T-cell lymphoma/leukaemia entities, their clinical features, recent advances in mapping their molecular and genomic landscapes, current treatment strategies and potential future targeting options.

IL-17A and IFN-γ are Up-regulated in CD4 and γδ T Cells in Active Behcet's Disease Patients

Involvement of γδ T cells is implicated in the pathogenesis of Behçet's disease (BD) as a bridge between innate and adaptive responses. IL-17 and IL-22 have also been shown to participate in the BD pathogenesis in addition to IFN-γ. Mainly CD4⁺ T cells are investigated previously for the production of these inflammatory cytokines. In this study, the role of γδ T cells in cytokine-related mechanisms was evaluated in BD in comparison to CD4⁺ T cells. Surface expression of markers for functional states of both CD4⁺ and γδ T cells were compared in ex vivo samples collected from patients with BD and healthy controls (HC). Sixteen active BD (a-BD), 9 inactive BD (i-BD) patients and 25 HC were investigated. The expression of CD161, CCR6 as markers for IL-17 producing cells were analyzed on γδ and CD4⁺ T cells. IFN-γ, IL-17A, IL-22, as well as CD107a (LAMP1) and CD16 (FcγRIII) were evaluated in both cell subtypes after in vitro stimulation. Only IFN-γ production was increased in γδ T cells of a-BD patients. There was no difference in increase of CD107a or decrease of CD16 surface expression on γδ T cells upon stimulation between the groups. Ex vivo IL-17A and both IL-17A/IFN-γ production and expression of CD161, CCR6 by CD4⁺ T cells were increased in a-BD. Along with CD4⁺ T cells, γδ T cells have complementary roles in cytokine production in BD. Higher IFN-γ production of γδ T cells suggests the role of an environmental triggers in BD pathogenesis, whereas IL-17 related activity is mainly provided by CD4⁺ T cells.

Metabolic Changes in Tumor Microenvironment: How Could They Affect γδ T Cells Functions?

The metabolic changes that occur in tumor microenvironment (TME) can influence not only the biological activity of tumor cells, which become more aggressive and auto sustained, but also the immune response against tumor cells, either producing ineffective responses or polarizing the response toward protumor activity. γδ T cells are a subset of T cells characterized by a plasticity that confers them the ability to differentiate towards different cell subsets according to the microenvironment conditions. On this basis, we here review the more recent studies focused on altered tumor metabolism and γδ T cells, considering their already known antitumor role and the possibility of manipulating their effector functions by in vitro and in vivo approaches. γδ T cells, thanks to their unique features, are themselves a valid alternative to overcome the limits associated with the use of conventional T cells, such as major histocompatibility complex (MHC) restriction, costimulatory signal and specific tumor-associated antigen recognition. Lipids, amino acids, hypoxia, prostaglandins and other metabolic changes inside the tumor microenvironment could reduce the efficacy of this important immune population and polarize γδ T cells toward IL17 producing cells that play a pro tumoral role. A deeper knowledge of this phenomenon could be helpful to formulate new immunotherapeutic approaches that target tumor metabolisms.

Guselkumab, an inhibitor of the IL-23p19 subunit, provides sustained improvement in signs and symptoms of active psoriatic arthritis: 1 year results of a phase III randomised study of patients who were biologic-naïve or TNFα inhibitor-experienced

Objective

Evaluation of the efficacy and safety of guselkumab, a human monoclonal antibody targeting the interleukin-23p19 subunit, in patients with psoriatic arthritis (PsA) through 1 year.

Methods

Adults who met ClASsification criteria for Psoriatic ARthritis, with active disease (≥3 swollen and ≥3 tender joints; C reactive protein ≥0.3 mg/dL) despite standard treatment (31% previously received ≤2 tumour necrosis factor inhibitors (TNFi)), were randomised (1:1:1) to guselkumab 100 mg every 4 weeks (Q4W); guselkumab 100 mg at Week0, Week4, then Q8W; or placebo with cross-over to guselkumab 100 mg Q4W at Week24 (PBO→Q4W) through Week48. Clinical efficacy through Week52 (employing non-responder imputation) and adverse events (AEs) through Week60 were evaluated.

Results

Of 381 treated patients, 90% completed the study. Numerical increases in the proportions of patients achieving ≥20% improvement in ACR criteria (ACR20) were observed post-Week24, reaching 73% (94/128) and 60% (76/127) for Q4W-randomised and Q8W-randomised patients, respectively, by Week52. Proportions of patients achieving ACR50/ACR70/skin responses and minimal/very low disease activity were maintained, as were improvements in physical function and health-related quality of life, through Week52 in guselkumab-randomised patients. Response to guselkumab was maintained in both TNFi-naïve and TNFi-experienced patients. Serious AEs and serious infections occurred in similar proportions of guselkumab Q4W-randomised (3% and 0%) and Q8W-randomised (6% and 2%) patients through Week60, with no new safety concerns versus observations through Week24. No guselkumab-treated patient and two patients receiving placebo died; no study participant developed opportunistic infection or inflammatory bowel disease.

Conclusion

Guselkumab provided sustained improvement across multiple clinical manifestations of PsA, maintaining a favourable benefit-risk profile, through 1 year regardless of prior TNFi exposure.

Evolved to protect, designed to destroy: IL-17-producing γδ T cells in infection, inflammation, and cancer

T cells of the gamma delta (γδ) lineage are evolutionary conserved from jawless to cartilaginous and bony fish to mammals and represent the "swiss army knife" of the immune system capable of antigen-dependent or independent responses, memory, antigen presentation, regulation of other lymphocytes, tissue homeostasis, and mucosal barrier maintenance, to list a few. Over the last 10 years, γδ T cells that produce the cytokine IL-17 (γδT17) have taken a leading position in our understanding of how our immune system battles infection, inflicts tissue damage during inflammation, and gets rewired by the tumor microenvironment. A lot of what we know about γδT17 cells stems from mouse models, however, increasing evidence implicates these cells in numerous human diseases. Herein, we aim to give an overview of the most common mouse models that have been used to study the role of γδT17 cells in infection, inflammation, and cancer, while at the same time we will evaluate evidence for their importance in humans. We hope and believe that in the next 10 years, means to take advantage of the protective and destructive properties of γδ T and in particular γδT17 cells will be part of our standard immunotherapy toolkit.

Targeting butyrophilins for cancer immunotherapy

Vγ9Vδ2⁺ T cells form part of the innate immune repertoire and are activated by phosphorylated antigens produced by many bacteria and tumors. They have long been suggested as promising targets for anti-tumor therapies, but clinical trials so far have not shown major successes. Several recent discoveries could help to overcome these shortfalls, such as those leading to an improved understanding of the role of butyrophilin molecules BTN2A1 and BTN3A1, in Vγ9Vδ2⁺ T cell activation. Moreover, we propose that studies suggesting the presence of live bacteria in a variety of tumors (tumor microbiome), indicate that the latter might be harnessed as a source of high affinity bacterial phosphoantigen to trigger or enhance anti-tumor immune responses.

A fetal wave of human type 3 effector γδ cells with restricted TCR diversity persists into adulthood

Accumulating evidence suggests that the mouse embryonic thymus produces distinct waves of innate effector γδ T cells. However, it is unclear whether this process occurs similarly in humans and whether it comprises a dedicated subset of innate-like type 3 effector γδ T cells. Here, we present a protocol for high-throughput sequencing of TRG and TRD pairs that comprise the clonal γδTCR. In combination with single-cell RNA sequencing, multiparameter flow cytometry, and TCR sequencing, we reveal a high heterogeneity of γδ T cells sorted from neonatal and adult blood that correlated with TCR usage. Immature γδ T cell clusters displayed mixed and diverse TCRs, but effector cell types segregated according to the expression of either highly expanded individual Vδ1⁺ TCRs or moderately expanded semi-invariant Vγ9Vδ2⁺ TCRs. The Vγ9Vδ2⁺ T cells shared expression of genes that mark innate-like T cells, including ZBTB16 (encoding PLZF), KLRB1, and KLRC1, but consisted of distinct clusters with unrelated Vγ9Vδ2⁺ TCR clones characterized either by TBX21, FCGR3A, and cytotoxicity-associated gene expression (type 1) or by CCR6, RORC, IL23R, and DPP4 expression (type 3). Effector γδ T cells with type 1 and type 3 innate T cell signatures were detected in a public dataset of early embryonic thymus organogenesis. Together, this study suggests that functionally distinct waves of human innate-like effector γδ T cells with semi-invariant Vγ9Vδ2⁺ TCR develop in the early fetal thymus and persist into adulthood.

Efficacy and Safety of Guselkumab, an Interleukin-23p19-Specific Monoclonal Antibody, Through One Year in Biologic-Naive Patients With Psoriatic Arthritis

Objective

Guselkumab, a human monoclonal antibody specific to interleukin‐23p19, demonstrated efficacy and safety versus placebo through week 24 of the phase III DISCOVER‐2 trial in biologic‐naive patients with psoriatic arthritis (PsA). Here we report 1‐year DISCOVER‐2 findings.

Methods

Adults with active PsA (≥5 swollen and ≥5 tender joints; C‐reactive protein level ≥0.6 mg/dl) despite standard nonbiologic treatment were randomized to receive subcutaneous injections of guselkumab 100 mg every 4 weeks, guselkumab 100 mg at week 0, week 4 and every 8 weeks thereafter, or placebo with crossover to guselkumab 100 mg every 4 weeks at week 24. We primarily evaluated clinical efficacy through week 52 by imputing missing data (nonresponse for categorical end points; no change/using multiple imputation for continuous end points). Observed radiographic scores and adverse events (AEs) were summarized.

Results

Of 739 randomized, treated patients, 93% completed week 52. The proportions of patients in whom a ≥20% improvement from baseline in American College of Rheumatology criteria (ACR20) was achieved were maintained after week 24, reaching 71% (173 of 245) and 75% (185 of 248) for patients randomized to receive treatment every 4 weeks or every 8 weeks, respectively, by week 52. The proportions of patients in whom ACR50/ACR70 and skin responses, minimal or very low disease activity, and dactylitis or enthesitis resolution were achieved at week 24 were also maintained through week 52. Further, low levels of radiographic progression, along with improvements in physical function and health‐related quality of life, were sustained through week 52 with continued guselkumab treatment. Few patients experienced serious infections through week 52, with no evidence of a dosing regimen response or increase from weeks 0–24 (4 of 493 [0.8%]) to weeks 24–52 (3 of 493 [0.6%]) among guselkumab‐randomized patients. No patient developed an opportunistic infection or died.

Conclusion

In biologic‐naive PsA patients, guselkumab provided sustained improvements across diverse manifestations and maintained a favorable risk–benefit profile through week 52.

Function of γδ T cells in tumor immunology and their application to cancer therapy

T cells of the γδ lineage are unconventional T cells with functions not restricted to MHC-mediated antigen presentation. Because of their broad antigen specificity and NK-like cytotoxicity, γδ T-cell importance in tumor immunology has been emphasized. However, some γδ T-cell subsets, especially those expressing IL-17, are immunosuppressive or tumor-promoting cells. Their cytokine profile and cytotoxicity are seemingly determined by cross-talk with microenvironment components, not by the γδTCR chain. Furthermore, much about the TCR antigen of γδ T cells remains unknown compared with the extreme diversity of their TCR chain pairs. Thus, the investigation and application of γδ T cells have been relatively difficult. Nevertheless, γδ T cells remain attractive targets for antitumor therapy because of their independence from MHC molecules. Because tumor cells have the ability to evade the immune system through MHC shedding, heterogeneous antigens, and low antigen spreading, MHC-independent γδ T cells represent good alternative targets for immunotherapy. Therefore, many approaches to using γδ T cells for antitumor therapy have been attempted, including induction of endogenous γδ T cell activation, adoptive transfer of expanded cells ex vivo, and utilization of chimeric antigen receptor (CAR)-T cells. Here, we discuss the function of γδ T cells in tumor immunology and their application to cancer therapy.

Gamma Delta T Cells and Their Pathogenic Role in Psoriasis

γδT cells are an unconventional population of T lymphocytes that play an indispensable role in host defense, immune surveillance, and homeostasis of the immune system. They display unique developmental, distributional, and functional patterns and rapidly respond to various insults and contribute to diverse diseases. Although γδT cells make up only a small portion of the total T cell pool, emerging evidence suggest that aberrantly activated γδT cells may play a role in the pathogenesis of psoriasis. Dermal γδT cells are the major IL-17-producing cells in the skin that respond to IL-23 stimulation. Furthermore, γδT cells exhibit memory-cell-like characteristics that mediate repeated episodes of psoriatic inflammation. This review discusses the differentiation, development, distribution, and biological function of γδT cells and the mechanisms by which they contribute to psoriasis. Potential therapeutic approaches targeting these cells in psoriasis have also been detailed.

Increase of Vδ2+ T Cells That Robustly Produce IL-17A in Advanced Abdominal Aortic Aneurysm Tissues

Abdominal aortic aneurysm (AAA) is a chronic dilation of the aorta with a tendency to enlarge and eventually rupture, which constitutes a major cause of cardiovascular mortality. Although T-cell infiltrates have been observed in AAA, the cellular, phenotypic, and functional characteristics of these tissue-infiltrating T cells are not fully understood. Here, we investigated the proportional changes of T-cell subsets-including CD4⁺ T cells, CD8⁺ T cells, and γδ T cells-and their effector functions in AAAs. We found that Vδ2⁺ T cells were presented at a higher frequency in aortic aneurysmal tissue compared to normal aortic tissue and PBMCs from patients with AAA. In contrast, no differences were observed in the frequencies of CD4⁺, CD8⁺, and Vδ1⁺ T cells. Moreover, we observed that the Vδ2⁺ T cells from AAA tissue displayed immunophenotypes indicative of CCR5⁺ non-exhausted effector memory cells, with a decreased proportion of CD16⁺ cells. Finally, we found that these Vδ2⁺ T cells were the main source of IL-17A in abdominal aortic aneurysmal tissue. In conclusion, our results suggest that increased Vδ2⁺ T cells that robustly produce IL-17A in aortic aneurysmal tissue may contribute to AAA pathogenesis and progression.

Translating Unconventional T Cells and Their Roles in Leukemia Antitumor Immunity

Recently, cell-mediated immune response in malignant neoplasms has become the focus in immunotherapy against cancer. However, in leukemia, most studies on the cytotoxic potential of T cells have concentrated only on T cells that recognize peptide antigens (Ag) presented by polymorphic molecules of the major histocompatibility complex (MHC). This ignores the great potential of unconventional T cell populations, which include gamma-delta T cells (γδ), natural killer T cells (NKT), and mucosal-associated invariant T cells (MAIT). Collectively, these T cell populations can recognize lipid antigens, specially modified peptides and small molecule metabolites, in addition to having several other advantages, which can provide more effective applications in cancer immunotherapy. In recent years, these cell populations have been associated with a repertoire of anti- or protumor responses and play important roles in the dynamics of solid tumors and hematological malignancies, thus, encouraging the development of new investigations in the area. This review focuses on the current knowledge regarding the role of unconventional T cell populations in the antitumor immune response in leukemia and discusses why further studies on the immunotherapeutic potential of these cells are needed.

Immunobiology and immunotherapy of HCC: spotlight on innate and innate-like immune cells

Immune-based therapies such as immune checkpoint inhibitors have revolutionized the systemic treatment of various cancer types. The therapeutic application of monoclonal antibodies targeting inhibitory pathways such as programmed cell death-1(PD-1)/programmed cell death ligand 1 (PD-L1) and CTLA-4 to cells of the adaptive immune system has recently been shown to generate meaningful improvement in the clinical outcome of hepatocellular carcinoma (HCC). Nevertheless, current immunotherapeutic approaches induce durable responses in only a subset of HCC patients. Since immunologic mechanisms such as chronic inflammation due to chronic viral hepatitis or alcoholic and nonalcoholic fatty liver disease play a crucial role in the initiation, development, and progression of HCC, it is important to understand the underlying mechanisms shaping the unique tumor microenvironment of liver cancer. The liver is an immunologic organ with large populations of innate and innate-like immune cells and is exposed to bacterial, viral, and fungal antigens through the gut-liver axis. Here, we summarize and highlight the role of these cells in liver cancer and propose strategies to therapeutically target them. We also discuss current immunotherapeutic strategies in HCC and outline recent advances in our understanding of how the therapeutic potential of these agents might be enhanced.

Synthetic retinoid AM80 inhibits IL-17 production of gamma delta T cells and ameliorates biliary atresia in mice

BACKGROUND & AIMS

Recent evidence suggests that Interleukin (IL)-17-producing gamma delta ( γδ ) T cells are the dominant pathogenic cellular component in designated autoimmune or inflammatory diseases, including biliary atresia (BA). We have previously demonstrated that retinoids effectively suppress T-helper cell (Th) 17 differentiation.

METHODS

Here, we established an in vitro system, enabling investigations of the effect of AM80 on the IL-17 production of γδ T cells. Additionally, we tested the therapeutic effect of AM80 in the Rotavirus-induced mouse model of BA. Co-incubation of γδ T cells with IL-23 and anti-CD28 mAb proved most effective in inducing an IL-17 response in vitro. The effect of AM80 on human CCR6+CD26+ V δ 2 cells was assessed by flow cytometry.

RESULTS

AM80 efficiently reduced IL-17 production by murine γδ T cells and the expression of the master transcription factor Retinoid-Orphan-Receptor- γ t (ROR γτ ) in a dose-dependent manner. The fraction of human CCR6+CD26+ V δ 2 cells was significantly reduced by co-incubation with AM80. Moreover, AM80 also inhibited IL-17 production by liver-infiltrating γδ T cells isolated from animals suffering from BA. Intraperitoneal treatment with AM80 ameliorated BA-associated inflammation. However, AM80 treatment was not sufficient to control disease progression in the murine model, despite reduced inflammatory activity in the animals.

CONCLUSIONS

Retinoids are very efficient in down-regulating IL-17 production by γδ T cells in vitro and, to a lesser extent, in the BA mouse model. However, retinoids do not suffice for the control of disease progression. Thus, our data suggest that IL-17 is not the only factor contributing to the pathogenesis of BA.

LAY SUMMARY

Biliary atresia (BA) is a rare disease which affects infants, causing progressive liver failure in most children, and is the most common indication for paediatric liver transplantation. We have previously demonstrated that IL-17, produced by γδ T cells, contributes to hepatic inflammation in the murine model of BA and is increased in the livers of infants suffering from the disease. In the study at hand, we demonstrate that treatment with AM80, a synthetic retinoid with superior pharmacological properties, effectively inhibits the IL-17 production of gamma delta T cells without generating systemic immunosuppression. Although all-trans retinoic acid (ATRA) has been demonstrated to suppress differentiation of IL-17-producing conventional T-helper cells (Th17) in vitro, the therapeutic application of ATRA in vivo is limited by the compound's potential side effects caused by its instability and lack of receptor specificity. Our study is the first to show that AM80 suppresses the IL-17 production of γδ T cells in a very efficient manner and that hepatic inflammation is ameliorated in mice suffering from BA. However, AM80 treatment does not suffice to block the disease progression. We conclude that factors other than IL-17 drive the progressive inflammation in BA. The addition of retinoids to the treatment regime of children suffering from BA might decrease the disease burden; however, further research is needed to clarify the pathomechanism and possible therapeutic interventions in humans.

Diversity in recognition and function of human γδ T cells

As interest increases in harnessing the potential power of tissue-resident cells for human health and disease, γδ T cells have been thrust into the limelight due to their prevalence in peripheral tissues, their sentinel-like phenotypes, and their unique antigen recognition capabilities. This review focuses primarily on human γδ T cells, highlighting their distinctive characteristics including antigen recognition, function, and development, with an emphasis on where they differ from their αβ T cell comparators, as well as from γδ T cell populations in the mouse. We review the antigens that have been identified thus far to regulate members of the human Vδ1 population and discuss what players are involved in transducing phosphoantigen-mediated signals to human Vγ9Vδ2 T cells. We also briefly review distinguishing features of these cells in terms of TCR signaling, use of coreceptor and costimulatory molecules and their development. These cells have great potential to be harnessed in a clinical setting, but caution must be taken to understand their unique capabilities and how they differ from the populations to which they are commonly compared.

Gut γδ T cells as guardians, disruptors, and instigators of cancer

Colorectal cancer is the third most common cancer worldwide with nearly 2 million cases per year. Immune cells and inflammation are a critical component of colorectal cancer progression, and they are used as reliable prognostic indicators of patient outcome. With the growing appreciation for immunology in colorectal cancer, interest is growing on the role γδ T cells have to play, as they represent one of the most prominent immune cell populations in gut tissue. This group of cells consists of both resident populations-γδ intraepithelial lymphocytes (γδ IELs)-and transient populations that each has unique functions. The homeostatic role of these γδ T cell subsets is to maintain barrier integrity and prevent microorganisms from breaching the mucosal layer, which is accomplished through crosstalk with enterocytes and other immune cells. Recent years have seen a surge in discoveries regarding the regulation of γδ IELs in the intestine and the colon with particular new insights into the butyrophilin family. In this review, we discuss the development, specialities, and functions of γδ T cell subsets during cancer progression. We discuss how these cells may be used to predict patient outcome, as well as how to exploit their behavior for cancer immunotherapy.

Similar biologics in India: A story of access or potential for compromise?

Biosimilars or similar biotherapeutic products are the biological products approved by regulatory agencies based on the demonstration of similarity in quality, safety and efficacy with reference biologics (or original biologics). Though biosimilars could be considered as interchangeable therapeutic alternatives over original biologics, there are concerns regarding their similarity in effectiveness and safety with reference product along with the level of evidence of similarity required for approval. The biosimilars, particularly, monoclonal antibodies that are developed based on the complex manufacturing processes, require stringent comparative evaluations. The Indian Regulatory Authorities in July 2012 developed the first guidelines for approval of similar biologics, which comprised requirements for the manufacturing process, quality evaluation, preclinical and clinical studies, as well as post-marketing studies. The 2016 guidelines, an update to previous guidelines, were released with the intent to provide a well-defined pathway at par with international regulations for the approval of similar biologics in India. This article highlights the key attributes of the 2016 Regulatory Guidelines and also describes the aspects such as interchangeability, nomenclature and labelling of similar biologics in India. Rigorous consideration is imperative for highly complex similar biologics of monoclonal antibodies on a case-to-case basis.

ADAM protease inhibition overcomes resistance of breast cancer stem-like cells to γδ T cell immunotherapy

Gamma delta T cells (γδTc) have tremendous anti-tumoral activity, thus γδTc immunotherapy is currently under development for various malignancies. We targeted breast cancer stem-like cells (BCSC), a rare cell population responsible for patient mortality. BCSC were mostly susceptible to γδTc immunotherapy, yet some escaped. The BCSC secretome rendered γδTc hypo-responsive, and resistant BCSC expressed more PD-L1 and anti-apoptotic protein MCL-1 than non-stem-like cells (NSC). BCSC resistance was partially overcome by dMCL1-2, an MCL-1 degrader, or more fully by blocking PD-1 on γδTc. Increased MICA shedding was prevented by the ADAM inhibitor GW280264X, rendering BCSC as sensitive to γδTc cytotoxicity as NSC. Our data show promising potential for γδTc immunotherapy against BCSC while unraveling immune evasion mechanisms exploited by BCSC, which likely also enable their resistance to cytotoxic T and NK cells. Overcoming this resistance, as we have done here, will improve cancer immunotherapy, leading to better cancer patient outcomes.

Immune recognition of phosphoantigen-butyrophilin molecular complexes by γδ T cells

Gamma-delta (γδ) T cells are an important component of the immune system. They are often enriched in non-lymphoid tissues and exhibit diverse functional attributes including rapid activation, cytokine production, proliferation, and acquisition of cytotoxicity following both TCR-dependent and TCR-independent stimulation, but poor capacity for immunological memory. They can detect a broad range of antigens, although typically not peptide-MHC complexes in contrast to alpha-beta (αβ) T cells. In humans, a prominent population of γδ T cells, defined as Vγ9Vδ2⁺ cells, reacts to small phosphorylated non-peptide "phosphoantigens" (pAgs). The molecular mechanism underpinning this recognition is poorly defined, but is known to involve butyrophilin family members and appears to involve indirect pAg recognition via alterations to butyrophilin molecular complexes. In this review, we discuss recent advances in our understanding of pAg recognition by γδ T cells including the role of butyrophilins and in particular, a newly described role for butyrophilin 2A1.

Pro-tumor γδ T Cells in Human Cancer: Polarization, Mechanisms of Action, and Implications for Therapy

The tumor immune microenvironment contributes to tumor initiation, progression and response to therapy. Among the immune cell subsets that play a role in the tumor microenvironment, innate-like T cells that express T cell receptors composed of γ and δ chains (γδ T cells) are of particular interest. Indeed, γδ T cells contribute to the immune response against many cancers, notably through their powerful effector functions that lead to the elimination of tumor cells and the recruitment of other immune cells. However, their presence in the tumor microenvironment has been associated with poor prognosis in various solid cancers (breast, colon and pancreatic cancer), suggesting that γδ T cells also display pro-tumor activities. In this review, we outline the current evidences of γδ T cell pro-tumor functions in human cancer. We also discuss the factors that favor γδ T cell polarization toward a pro-tumoral phenotype, the characteristics and functions of such cells, and the impact of pro-tumor subsets on γδ T cell-based therapies.

Cancer immunotherapy with γδ T cells: many paths ahead of us

γδ T cells play uniquely important roles in stress surveillance and immunity for infections and carcinogenesis. Human γδ T cells recognize and kill transformed cells independently of human leukocyte antigen (HLA) restriction, which is an essential feature of conventional αβ T cells. Vγ9Vδ2 γδ T cells, which prevail in the peripheral blood of healthy adults, are activated by microbial or endogenous tumor-derived pyrophosphates by a mechanism dependent on butyrophilin molecules. γδ T cells expressing other T cell receptor variable genes, notably Vδ1, are more abundant in mucosal tissue. In addition to the T cell receptor, γδ T cells usually express activating natural killer (NK) receptors, such as NKp30, NKp44, or NKG2D which binds to stress-inducible surface molecules that are absent on healthy cells but are frequently expressed on malignant cells. Therefore, γδ T cells are endowed with at least two independent recognition systems to sense tumor cells and to initiate anticancer effector mechanisms, including cytokine production and cytotoxicity. In view of their HLA-independent potent antitumor activity, there has been increasing interest in translating the unique potential of γδ T cells into innovative cellular cancer immunotherapies. Here, we discuss recent developments to enhance the efficacy of γδ T cell-based immunotherapy. This includes strategies for in vivo activation and tumor-targeting of γδ T cells, the optimization of in vitro expansion protocols, and the development of gene-modified γδ T cells. It is equally important to consider potential synergisms with other therapeutic strategies, notably checkpoint inhibitors, chemotherapy, or the (local) activation of innate immunity.

Activation of Human Vδ2+ γδ T Cells by Staphylococcus aureus Promotes Enhanced Anti-Staphylococcal Adaptive Immunity

Murine studies have shown the potential for γδ T cells to mediate immunity to Staphylococcus aureus in multiple tissue settings by the secretion of diverse cytokines. However, the role played by γδ T cells in human immune responses to S. aureus is almost entirely unknown. In this study, we establish the capacity of human Vδ2+ γδ T cells for rapid activation in response to S. aureus In coculture with S. aureus-infected monocyte-derived dendritic cells (DCs), Vδ2+ cells derived from peripheral blood rapidly upregulate CD69 and secrete high levels of IFN-γ. DCs mediate this response through direct contact and IL-12 secretion. In turn, IFN-γ released by Vδ2+ cells upregulates IL-12 secretion by DCs in a positive feedback loop. Furthermore, coculture with γδ T cells results in heightened expression of the costimulatory molecule CD86 and the lymph node homing molecule CCR7 on S. aureus-infected DCs. In cocultures of CD4+ T cells with S. aureus-infected DCs, the addition of γδ T cells results in heightened CD4+ T cell activation. Our findings identify γδ T cells as potential key players in the early host response to S. aureus during bloodstream infection, promoting enhanced responses by both innate and adaptive immune cell populations, and support their consideration in the development of host-directed anti-S. aureus treatments.

Interleukin-22 and intestinal homeostasis: Protective or destructive?

Interleukin (IL)-22 is a member of IL-10 family cytokines with various immunologic functions. As its name implies, IL-22 is known to be secreted mainly by Th22 cells, a recently discovered lineage of CD4+ T cells. Also, Th17, Th1, natural killer cells, γδT cells, and innate immune cells along with some nonlymphoid cells have been confirmed as secondary cellular sources of IL-22. Different cell types such as bronchial and intestinal epithelial cells, keratinocytes, hepatocytes, dermal fibroblasts, and tubular epithelial cells are affected by IL-22. Both pathologic and protective roles have been attributed to IL-22 in maintaining gut homeostasis and inflammation. According to the latest fast-growing investigations, IL-22 is significantly involved in various pathologies including allergic diseases, infection, autoimmunity, and cancer development. Regulating gut immune responses, barrier integrity, and inflammation is dependent on a diverse complex of cytokines and mediators which are secreted by mucosal immune cells. Several investigations have been designed to recognize the role of IL-22 in gastrointestinal immunity. This article tries to discuss the latest knowledge on this issue and clarify the potential of IL-22 to be used in the future therapeutic approaches of intestinal disorders including inflammatory bowel diseases and colon cancer.