Murine CD27(-) Vγ6(+) γδ T cells producing IL-17A promote ovarian cancer growth via mobilization of protumor small peritoneal macrophages

PD-1 regulation of pathogenic IL-17-secreting γδ T cells in experimental autoimmune encephalomyelitis

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

The therapeutic role of γδT cells in TNBC

Triple-negative breast cancer (TNBC) is a subtype of breast cancer that presents significant therapeutic challenges due to the absence of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression. As a result, conventional hormonal and targeted therapies are largely ineffective, underscoring the urgent need for novel treatment strategies. γδT cells, known for their robust anti-tumor properties, show considerable potential in TNBC treatment as they can identify and eliminate tumor cells without reliance on MHC restrictions. These cells demonstrate extensive proliferation both in vitro and in vivo, and can directly target tumors through cytotoxic effects or indirectly by promoting other immune responses. Studies suggest that expansion and adoptive transfer strategies targeting Vδ2 and Vδ1 γδT cell subtypes have shown promise in preclinical TNBC models. This review compiles and discusses the existing literature on the primary subgroups of γδT cells, their roles in cancer therapy, their contributions to tumor cell cytotoxicity and immune modulation, and proposes potential strategies for future γδT cell-based immunotherapies in TNBC.

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.

The mutual regulation between γδ T cells and macrophages during wound healing

Macrophages are the main cells shaping the local microenvironment during wound healing. As the prime T cells in the skin, γδ T cells participate in regulating microenvironment construction, determining their mutual regulation helps to understand the mechanisms of wound healing, and explore innovative therapeutic options for wound repair. This review introduced their respective role in wound healing firstly, and then summarized the regulatory effect of γδ T cells on macrophages, including chemotaxis, polarization, apoptosis, and pyroptosis. Last, the retrograde regulation on γδ T cells by macrophages was also discussed. The main purpose is to excavate novel interventions for treating wound and provide new thought for further research.

Candida albicans-myeloid cells-T lymphocytes axis in the tumor microenvironment of oral tumor-bearing mice

Candida albicans (C. albicans) is associated with the development of oral cancer. Here, we report the altered tumor microenvironment in oral tumor-bearing mice caused by C. albicans infection. Single-cell RNA sequencing showed that C. albicans infection influenced the tumor microenvironment significantly. Specifically, C. albicans infection reduced the CD8+ T cells but increased the IL-17A+ CD4+ T cells and IL-17A+ γδ T cells in oral tumor. The neutralization of IL-17A or TCR γ/δ alleviated the tumor progression caused by C. albicans infection. Additionally, C. albicans infection promoted the infiltration of myeloid-derived suppressor cells (MDSCs) into tumor, especially polymorphonuclear (PMN)-MDSCs, which infiltration was reduced after the neutralization of CCL2. Thus, our findings reveal the myeloid cells-T lymphocytes axis in oral tumor microenvironment with C. albicans infection, which helps to understand the mechanisms for C. albicans promoting oral cancer from the perspective of immune microenvironment.

Tumor reactive γδ T cells contribute to a complete response to PD-1 blockade in a Merkel cell carcinoma patient

Immunotherapies targeting PD-1/PD-L1 are now widely used in the clinic to treat a variety of malignancies. While most of the research on T cell exhaustion and PD-1 blockade has been focused on conventional αβ T cells, the contribution of innate-like T cells such as γδ T cells to anti-PD-1/PD-L1 mediated therapy is limited. Here we show that tumor reactive γδ T cells respond to PD-1 blockade in a Merkel cell carcinoma (MCC) patient experiencing a complete response to therapy. We find clonally expanded γδ T cells in the blood and tumor after pembrolizumab treatment, and this Vγ2Vδ1 clonotype recognizes Merkel cancer cells in a TCR-dependent manner. Notably, the intra-tumoral γδ T cells in the MCC patient are characterized by higher expression of PD-1 and TIGIT, relative to conventional CD4 and CD8 T cells. Our results demonstrate that innate-like T cells could also contribute to an anti-tumor response after PD-1 blockade.

Exploiting innate immunity for cancer immunotherapy

Immunotherapies have revolutionized the treatment paradigms of various types of cancers. However, most of these immunomodulatory strategies focus on harnessing adaptive immunity, mainly by inhibiting immunosuppressive signaling with immune checkpoint blockade, or enhancing immunostimulatory signaling with bispecific T cell engager and chimeric antigen receptor (CAR)-T cell. Although these agents have already achieved great success, only a tiny percentage of patients could benefit from immunotherapies. Actually, immunotherapy efficacy is determined by multiple components in the tumor microenvironment beyond adaptive immunity. Cells from the innate arm of the immune system, such as macrophages, dendritic cells, myeloid-derived suppressor cells, neutrophils, natural killer cells, and unconventional T cells, also participate in cancer immune evasion and surveillance. Considering that the innate arm is the cornerstone of the antitumor immune response, utilizing innate immunity provides potential therapeutic options for cancer control. Up to now, strategies exploiting innate immunity, such as agonists of stimulator of interferon genes, CAR-macrophage or -natural killer cell therapies, metabolic regulators, and novel immune checkpoint blockade, have exhibited potent antitumor activities in preclinical and clinical studies. Here, we summarize the latest insights into the potential roles of innate cells in antitumor immunity and discuss the advances in innate arm-targeted therapeutic strategies.

The capability of heterogeneous γδ T cells in cancer treatment

γδ T cells, a specialized subset of T lymphocytes, have garnered significant attention within the realm of cancer immunotherapy. Operating at the nexus between adaptive and innate immunological paradigms, these cells showcase a profound tumor discernment repertoire, hinting at novel immunotherapeutic strategies. Significantly, these cells possess the capability to directly identify and eliminate tumor cells without reliance on HLA-antigen presentation. Furthermore, γδ T cells have the faculty to present tumor antigens to αβ T cells, amplifying their anti-tumoral efficacy.Within the diverse and heterogeneous subpopulations of γδ T cells, distinct immune functionalities emerge, manifesting either anti-tumor or pro-tumor roles within the tumor microenvironment. Grasping and strategically harnessing these heterogeneous γδ T cell cohorts is pivotal to their integration in tumor-specific immunotherapeutic modalities. The aim of this review is to describe the heterogeneity of the γδ T cell lineage and the functional plasticity it generates in the treatment of malignant tumors. This review endeavors to elucidate the intricate heterogeneity inherent to the γδ T cell lineage, the consequential functional dynamics in combating malignancies, the latest advancements from clinical trials, and the evolving landscape of γδ T cell-based oncological interventions, while addressing the challenges impeding the field.

γδ T cells: origin and fate, subsets, diseases and immunotherapy

The intricacy of diseases, shaped by intrinsic processes like immune system exhaustion and hyperactivation, highlights the potential of immune renormalization as a promising strategy in disease treatment. In recent years, our primary focus has centered on γδ T cell-based immunotherapy, particularly pioneering the use of allogeneic Vδ2+ γδ T cells for treating late-stage solid tumors and tuberculosis patients. However, we recognize untapped potential and optimization opportunities to fully harness γδ T cell effector functions in immunotherapy. This review aims to thoroughly examine γδ T cell immunology and its role in diseases. Initially, we elucidate functional differences between γδ T cells and their αβ T cell counterparts. We also provide an overview of major milestones in γδ T cell research since their discovery in 1984. Furthermore, we delve into the intricate biological processes governing their origin, development, fate decisions, and T cell receptor (TCR) rearrangement within the thymus. By examining the mechanisms underlying the anti-tumor functions of distinct γδ T cell subtypes based on γδTCR structure or cytokine release, we emphasize the importance of accurate subtyping in understanding γδ T cell function. We also explore the microenvironment-dependent functions of γδ T cell subsets, particularly in infectious diseases, autoimmune conditions, hematological malignancies, and solid tumors. Finally, we propose future strategies for utilizing allogeneic γδ T cells in tumor immunotherapy. Through this comprehensive review, we aim to provide readers with a holistic understanding of the molecular fundamentals and translational research frontiers of γδ T cells, ultimately contributing to further advancements in harnessing the therapeutic potential of γδ T cells.

METTL3-mediated m6A methylation regulates ovarian cancer progression by recruiting myeloid-derived suppressor cells

BACKGROUND

Ovarian cancer (OC) typically develops an immunosuppressive microenvironment by funtional changes of host immune cells. Dysregulated m6A level is associated with cancer progression via the intrinsic oncogenic pathways. However, the role of m6A in regulating host immune cell function during anti-tumor immunity needs comprehensive analysis. This study aimed to investigate the role of METTL3, a catalytic subunit of the methyltransferase complex, in regulating host immune cell response against OC.

METHODS

In this study, myeloid-specific Mettl3 gene knockout (Mettl3-cKO) mice were bred using the Cre-LoxP system. Intraperitoneally injection of ID8 cells was used as a syngeneic OC model. Furthermore, the compositions of immune cell populations were analyzed by flow cytometry and single-cell sequencing. Moreover, chemokines and cytokines secretion were assessed using ELISA. Lastly, the role of METTL3 in regulating IL-1β secretion and inflammasome activation in bone marrow-derived macrophages cocultured with ID8 cells was specified by ELISA and immunoblotting.

RESULTS

It was revealed that OC cell growth was enhanced in Mettl3-cKO mice. Furthermore, a shift of decreased M1 to increased M2 macrophage polarization was observed during OC progression. Moreover, Mettl3 depletion in myeloid lineage cells increased secretion of CCL2 and CXCL2 in peritoneal lavage fluild. Interestingly, Mettl3 deficiency enhanced IL-1β secretion induced by viable ID8 cells independent of inflammasome activation and cell death. Therefore, OC cells in tumor-bearing mice trigger a slight inflammatory response with a low-to-moderate secretion of pro-inflammatory cytokines and chemokines.

CONCLUSION

This study provides new insights into METTL3-mediated m6A methylation, which regulates host immune response against OC.

The potential role of interleukins and interferons in ovarian cancer

Ovarian cancer poses significant challenges and remains a highly lethal disease with limited treatment options. In the context of ovarian cancer, interleukins (ILs) and interferons (IFNs), important cytokines that play crucial roles in regulating the immune system, have emerged as significant factors influencing its development. This article provides a comprehensive review of the involvement of various ILs, including those from the IL-1 family, IL-2 family, IL-6 family, IL-8 family, IL-10 family, and IL-17 family, in ovarian cancer. The focus is on their impact on tumor growth, metastasis, and their role in evading immune responses within the tumor microenvironment. Additionally, the article conducts an in-depth examination of the oncogenic or antitumor roles of each IL in the context of ovarian cancer pathogenesis and progression. Besides, we elucidated the enhancements in the treatment of ovarian cancer through the utilization of type-I IFN and type-II IFN. Recent research has shed light on the intricate mechanisms through which specific ILs and IFNs contribute to the advancement of the disease. By incorporating recent findings, this review also seeks to inspire further investigations into unexplored mechanisms, fostering ongoing research to develop more effective therapeutic strategies for ovarian cancer. Moreover, through an in-depth analysis of IL- and IFN-associated clinical trials, we have highlighted their promising potential of in the treatment of ovarian cancer. These clinical trials serve to reinforce the significant outlook for utilizing ILs and IFNs as therapeutic agents in combating this disease.

PPARγ activation modulates the balance of peritoneal macrophage populations to suppress ovarian tumor growth and tumor-induced immunosuppression

BACKGROUND

Ovarian adenocarcinoma (OVAD) frequently metastasizes to the peritoneal cavity and manifests by the formation of ascites, which constitutes a tumor-promoting microenvironment. In the peritoneal cavity, two developmentally, phenotypically and functionally distinct macrophage subsets, immunocompetent large peritoneal macrophages (LPM) and immunosuppressive small peritoneal macrophages (SPM), coexist. Because peroxisome proliferator-activated receptor γ (PPARγ) is a critical factor participating in macrophage differentiation and cooperates with CCAAT/enhancer binding protein β (C/EBPβ), a transcription factor essential for SPM-to-LPM differentiation, PPARγ could be also involved in the regulation of SPM/LPM balance and could be a promising therapeutic target.

METHODS

To evaluate the 15(S)-hydroxyeicosatetraenoic acid (HETE), a PPARγ endogenous ligand, impact on ovarian tumor growth, we intraperitoneally injected 15(S)-HETE into a murine ovarian cancer model. This experimental model consists in the intraperitoneally injection of ID8 cells expressing luciferase into syngeneic C57BL/6 female mice. This ID8 orthotopic mouse model is a well-established experimental model of end-stage epithelial OVAD. Tumor progression was monitored using an in vivo imaging system. Peritoneal immune cells in ascites were analyzed by flow cytometry and cell sorting. To determine whether the impact of 15(S)-HETE in tumor development is mediated through the macrophages, these cells were depleted by injection of liposomal clodronate. To further dissect how 15(S)-HETE mediated its antitumor effect, we assessed the tumor burden in tumor-bearing mice in which the PPARγ gene was selectively disrupted in myeloid-derived cells and in mice deficient of the recombination-activating gene Rag2. Finally, to validate our data in humans, we isolated and treated macrophages from ascites of individuals with OVAD.

RESULTS

Here we show, in the murine experimental model of OVAD, that 15(S)-HETE treatment significantly suppresses the tumor growth, which is associated with the differentiation of SPM into LPM and the LPM residency in the peritoneal cavity. We demonstrate that C/EBPβ and GATA6 play a central role in SPM-to-LPM differentiation and in LPM peritoneal residence through PPARγ activation during OVAD. Moreover, this SPM-to-LPM switch is associated with the increase of the effector/regulatory T-cell ratio. Finally, we report that 15(S)-HETE attenuates immunosuppressive properties of human ovarian tumor-associated macrophages from ascites.

CONCLUSION

Altogether, these results promote PPARγ as a potential therapeutic target to restrain OVAD development and strengthen the use of PPARγ agonists in anticancer therapy.

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.

Infiltrated IL-17A-producing gamma delta T cells play a protective role in sepsis-induced liver injury and are regulated by CCR6 and gut commensal microbes

Introduction

Sepsis is a common but serious disease in intensive care units, which may induce multiple organ dysfunctions such as liver injury. Previous studies have demonstrated that gamma delta (γδ) T cells play a protective role in sepsis. However, the function and mechanism of γδ T cells in sepsis-induced liver injury have not been fully elucidated. IL-17A-producing γδ T cells are a newly identified cell subtype.

Methods

We utilized IL-17A-deficient mice to investigate the role of IL-17A-producing γδ T cells in sepsis using the cecum ligation and puncture (CLP) model.

Results

Our findings suggested that these cells were the major source of IL-17A and protected against sepsis-induced liver injury. Flow cytometry analysis revealed that these γδ T cells expressed Vγ4 TCR and migrated into liver from peripheral post CLP, in a CCR6-dependent manner. When CLP mice were treated with anti-CCR6 antibody to block CCR6-CCL20 axis, the recruitment of Vγ4+ γδ T cells was abolished, indicating a CCR6-dependent manner of migration. Interestingly, pseudo germ-free CLP mice treated with antibiotics showed that hepatic IL-17A+ γδ T cells were regulated by gut commensal microbes. E. coli alone were able to restore the protective effect in pseudo germ-free mice by rescuing hepatic IL-17A+ γδ T cell population.

Conclusion

Our research has shown that Vγ4+ IL-17A+ γδ T cells infiltrating into the liver play a crucial role in protecting against sepsis-induced liver injury. This protection was contingent upon the recruitment of CCR6 and regulated by gut commensal microbes.

Natural γδT17 cell development and functional acquisition is governed by the mTORC2-c-Maf-controlled mitochondrial fission pathway

Natural IL-17-producing γδ T cells (γδT17 cells) are unconventional innate-like T cells that undergo functional programming in the fetal thymus. However, the intrinsic metabolic mechanisms of γδT17 cell development remain undefined. Here, we demonstrate that mTORC2, not mTORC1, selectively controls the functional fate commitment of γδT17 cells through regulating transcription factor c-Maf expression. scRNA-seq data suggest that fetal and adult γδT17 cells predominately utilize mitochondrial metabolism. mTORC2 deficiency results in impaired Drp1-mediated mitochondrial fission and mitochondrial dysfunction characterized by mitochondrial membrane potential (ΔΨm) loss, reduced oxidative phosphorylation (OXPHOS), and subsequent ATP depletion. Treatment with the Drp1 inhibitor Mdivi-1 alleviates imiquimod-induced skin inflammation. Reconstitution of intracellular ATP levels by ATP-encapsulated liposome completely rescues γδT17 defect caused by mTORC2 deficiency, revealing the fundamental role of metabolite ATP in γδT17 development. These results provide an in-depth insight into the intrinsic link between the mitochondrial OXPHOS pathway and γδT17 thymic programming and functional acquisition.

Innate lymphoid cells and innate-like T cells in cancer - at the crossroads of innate and adaptive immunity

Immunotherapies targeting conventional T cells have revolutionized systemic treatment for many cancers, yet only a subset of patients benefit from these approaches. A better understanding of the complex immune microenvironment of tumours is needed to design the next generation of immunotherapeutics. Innate lymphoid cells (ILCs) and innate-like T cells (ILTCs) are abundant, tissue-resident lymphocytes that have recently been shown to have critical roles in many types of cancers. ILCs and ILTCs rapidly respond to changes in their surrounding environment and act as the first responders to bridge innate and adaptive immunity. This places ILCs and ILTCs as pivotal orchestrators of the final antitumour immune response. In this Review, we outline hallmarks of ILCs and ILTCs and discuss their emerging role in antitumour immunity, as well as the pathophysiological adaptations leading to their pro-tumorigenic function. We explore the pleiotropic, in parts redundant and sometimes opposing, mechanisms that underlie the delicate interplay between the different subsets of ILCs and ILTCs. Finally, we highlight their role in amplifying and complementing conventional T cell functions and summarize immunotherapeutic strategies for targeting ILCs and ILTCs in cancer.

The emerging roles of γδ T cells in cancer immunotherapy

Current cancer immunotherapies are primarily predicated on αβ T cells, with a stringent dependence on MHC-mediated presentation of tumour-enriched peptides or unique neoantigens that can limit their efficacy and applicability in various contexts. After two decades of preclinical research and preliminary clinical studies involving very small numbers of patients, γδ T cells are now being explored as a viable and promising approach for cancer immunotherapy. The unique features of γδ T cells, including their tissue tropisms, antitumour activity that is independent of neoantigen burden and conventional MHC-dependent antigen presentation, and combination of typical properties of T cells and natural killer cells, make them very appealing effectors in multiple cancer settings. Herein, we review the main functions of γδ T cells in antitumour immunity, focusing on human γδ T cell subsets, with a particular emphasis on the differences between Vδ1⁺ and Vδ2⁺ γδ T cells, to discuss their prognostic value in patients with cancer and the key therapeutic strategies that are being developed in an attempt to improve the outcomes of these patients.

PD-1 and TIM-3 differentially regulate subsets of mouse IL-17A-producing γδ T cells

IL-17A-producing γδ T cells in mice consist primarily of Vγ6+ tissue-resident cells and Vγ4+ circulating cells. How these γδ T cell subsets are regulated during homeostasis and cancer remains poorly understood. Using single-cell RNA sequencing and flow cytommetry, we show that lung Vγ4+ and Vγ6+ cells from tumor-free and tumor-bearing mice express contrasting cell surface molecules as well as distinct co-inhibitory molecules, which function to suppress their expansion. Vγ6+ cells express constitutively high levels of PD-1, whereas Vγ4+ cells upregulate TIM-3 in response to tumor-derived IL-1β and IL-23. Inhibition of either PD-1 or TIM-3 in mammary tumor-bearing mice increased Vγ6+ and Vγ4+ cell numbers, respectively. We found that genetic deletion of γδ T cells elicits responsiveness to anti-PD-1 and anti-TIM-3 immunotherapy in a mammary tumor model that is refractory to T cell checkpoint inhibitors, indicating that IL-17A-producing γδ T cells instigate resistance to immunotherapy. Together, these data demonstrate how lung IL-17A-producing γδ T cell subsets are differentially controlled by PD-1 and TIM-3 in steady-state and cancer.

Recent Advances of RNA m6A Modifications in Cancer Immunoediting and Immunotherapy

Cancer immunotherapy, which modulates immune responses against tumors using immune-checkpoint inhibitors or adoptive cell transfer, has emerged as a novel and promising therapy for tumors. However, only a minority of patients demonstrate durable responses, while the majority of patients are resistant to immunotherapy. The immune system can paradoxically constrain and promote tumor development and progression. This process is referred to as cancer immunoediting. The mechanisms of resistance to immunotherapy seem to be that cancer cells undergo immunoediting to evade recognition and elimination by the immune system. RNA modifications, specifically N6-methyladenosine (m6A) methylation, have emerged as a key regulator of various post-transcriptional gene regulatory processes, such as RNA export, splicing, stability, and degradation, which play unappreciated roles in various physiological and pathological processes, including immune system development and cancer pathogenesis. Therefore, a deeper understanding of the mechanisms by which RNA modifications impact the cancer immunoediting process can provide insight into the mechanisms of resistance to immunotherapies and the strategies that can be used to overcome such resistance. In this chapter, we briefly introduce the background of cancer immunoediting and immunotherapy. We also review and discuss the roles and mechanisms of RNA m6A modifications in fine-tuning the innate and adaptive immune responses, as well as in regulating tumor escape from immunosurveillance. Finally, we summarize the current strategies targeting m6A regulators for cancer immunotherapy.

Role of γδ T Cells in Cancer Progression and Therapy

γδ T cells signify a foundational group of immune cells that infiltrate tumors early on, engaging in combat against cancer cells. The buildup of γδ T cells as cancer advances underscores their significance. Initially, these cells infiltrate and enact cytotoxic effects within the tumor tissue. However, in later stages, the predominant phenotype of γδ T cells undergoes changes in numerous cancers, fostering tumor growth and metastasis. Different mechanisms induced by cancer cell suppress effector action of γδ T cells and even sometimes promote cancer progression. In the early stages, stopping this mechanism clears this challenge and enables γδ T cells to effectively remove cancer cells. Given this context, it becomes imperative to delve into the mechanisms of how γδ T cells function in tumor microenvironment. This review discusses γδ T cells' role across different cancer types.

Development of γδ T Cells: Soldiers on the Front Lines of Immune Battles

While the functions of αβ T cells in host resistance to pathogen infection are understood in far more detail than those of γδ lineage T cells, γδ T cells perform critical, essential functions during immune responses that cannot be compensated for by αβ T cells. Accordingly, it is critical to understand how the development of γδ T cells is controlled so that their generation and function might be manipulated in future for therapeutic benefit. This introductory chapter will focus primarily on the basic processes that underlie γδ T cell development in the thymus, as well as the current understanding of how they are controlled.

γδ T Lymphocytes as a Double-Edged Sword-State of the Art in Gynecological Diseases

Human gamma-delta (γδ) T cells are a heterogeneous cell population that bridges the gap between innate and acquired immunity. They are involved in a variety of immunological processes, including tumor escape mechanisms. However, by being prolific cytokine producers, these lymphocytes also participate in antitumor cytotoxicity. Which one of the two possibilities takes place depends on the tumor microenvironment (TME) and the subpopulation of γδ T lymphocytes. The aim of this paper is to summarize existing knowledge about the phenotype and dual role of γδ T cells in cancers, including ovarian cancer (OC). OC is the third most common gynecological cancer and the most lethal gynecological malignancy. Anticancer immunity in OC is modulated by the TME, including by immunosuppressive cells, cytokines, and soluble factors. Immune cells are exposed in the TME to many signals that determine their immunophenotype and can manipulate their functions. The significance of γδ T cells in the pathophysiology of OC is enigmatic and remains to be investigated.

The research progress in the interaction between Candida albicans and cancers

Candida albicans is an opportunistic pathogenic fungus, which tends to infect the host with defective immune function including cancer patients. A growing number of studies have shown that C. albicans infection increases the host susceptibility to cancer such as oral, gastric, and colorectal cancer. Cancer and anti-cancer treatment may also affect the colonization of C. albicans. C. albicans may promote the development of cancer by damaging mucosal epithelium, inducing the production of carcinogens, triggering chronic inflammation including Th17 cell-mediated immune response. In this article, we aim to elaborate the interaction between C. albicans and cancers development and summarize the potential molecular mechanisms, so as to provide theoretical basis for prevention, diagnosis and treatment of cancers.

Peripheral γδ T Cells Regulate Neutrophil Expansion and Recruitment in Experimental Psoriatic Arthritis

OBJECTIVE

This study was undertaken to identify the mechanistic role of γδ T cells in the pathogenesis of experimental psoriatic arthritis (PsA).

METHODS

In this study, we performed interleukin-23 (IL-23) gene transfer in wild-type (WT) and T cell receptor δ-deficient (TCRδ-/- ) mice and conducted tissue phenotyping in the joint, skin, and nails to characterize the inflammatory infiltrate. We further performed detailed flow cytometry, immunofluorescence staining, RNA sequencing, T cell repertoire analysis, and in vitro T cell polarization assays to identify regulatory mechanisms of γδ T cells.

RESULTS

We demonstrated that γδ T cells support systemic granulopoiesis, which is critical for murine PsA-like pathology. Briefly, γδ T cell ablation inhibited the expression of neutrophil chemokines CXCL1 and CXCL2 and neutrophil CD11b+Ly6G+ accumulation in the aforementioned PsA-related tissues. Although significantly reduced expression of granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-17A was detected systemically in TCRδ-/- mice, no GM-CSF+/IL-17A+ γδ T cells were detected locally in the inflamed skin or bone marrow in WT mice. Our data showed that nonresident γδ T cells regulate the expansion of an CD11b+Ly6G+ neutrophil population and their recruitment to joint and skin tissues, where they develop hallmark pathologic features of human PsA.

CONCLUSION

Our findings do not support the notion that tissue-resident γδ T cells initiate the disease but demonstrate a novel role of γδ T cells in neutrophil regulation that can be exploited therapeutically in PsA patients.

Peritoneal resident macrophages in tumor metastasis and immunotherapy

Macrophages residing in various tissues play crucial roles in innate immunity, tissue repair, and immune homeostasis. The development and differentiation of macrophages in non-lymphoid tissues are highly regulated by the tissue microenvironment. Peritoneum provides a unique metastatic niche for certain types of tumor cells. As the dominant immune cell type in peritoneal cavity, macrophages control the immune response to tumor and influence the efficacy of anti-tumor therapy. Considering the heterogeneity of macrophages in origin, metabolism, and function, it is always challenging to define the precise roles of macrophages in tumor microenvironment. We review here recent progresses in peritoneal resident macrophage research in the context of physiological and metastatic tumor conditions, which may benefit the development of new anti-tumor therapies through targeting macrophages.

TCR-Vγδ usage distinguishes protumor from antitumor intestinal γδ T cell subsets

γδ T cells represent a substantial fraction of intestinal lymphocytes at homeostasis, but they also constitute a major lymphocyte population infiltrating colorectal cancers (CRCs); however, their temporal contribution to CRC development or progression remains unclear. Using human CRC samples and murine CRC models, we found that most γδ T cells in premalignant or nontumor colons exhibit cytotoxic markers, whereas tumor-infiltrating γδ T cells express a protumorigenic profile. These contrasting T cell profiles were associated with distinct T cell receptor (TCR)-Vγδ gene usage in both humans and mice. Longitudinal intersectional genetics and antibody-dependent strategies targeting murine γδ T cells enriched in the epithelium at steady state led to heightened tumor development, whereas targeting γδ subsets that accumulate during CRC resulted in reduced tumor growth. Our results uncover temporal pro- and antitumor roles for γδ T cell subsets.

Identification of the function of γδ1 T cells in the lung cancer microenvironments

PURPOSE

To investigate whether γδ1 T cells derived from lung cancer tissues have immunosuppressive function and to verify the mechanism of immunosuppressive effect.

METHODS

Fresh lung cancer tissue samples were collected, some of them were prepared tissue sections, the others were isolated and amplified into TILs cells, γδ1 T cells were isolated from TILs cells by immunomagnetic beads kits, and then cloned and amplified. The immunomodulatory effects of γδ1 T cells on naive and effector CD4⁺ T cells were detected by immunohistochemistry, flow cytometry, CCK8, ELISA and transwell culture.

RESULTS

A high proportion of γδ1 T cells was found in lung cancer tissues. The cultural supernatants of γδ1 T cells could inhibit the proliferation of naive CD4⁺ T cells and decrease the secretion level of IL-2 by effector CD4⁺ T cells. Further studies showed that the expression levels of IL-8, MIP-1α, MIP-1β and RANTES were higher than that of IFN-γ, GM-CSF and TNF-α, TNF-β, however, their neutralizing antibodies could not block the immunosuppressive activity of the supernatant.

CONCLUSION

γδ1 T cells play an negative immunoregulation function in lung cancer microenvironments, and have obvious immunosuppressive effects on proliferation and cytokine release of naive CD4⁺ T cells and effector CD4⁺ T cells. Preliminary evidence from this study suggests that the mechanism of immunosuppressive effects is mediated by the soluble factors in γδ1 T cell culture supernatants, but its exact molecular mechanism needs to be further explored.

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.

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.

Functional Phenotypes of Peritoneal Macrophages Upon AMD3100 Treatment During Colitis-Associated Tumorigenesis

CXCL12 and its receptor CXCR4 are independent prognostic factors in colorectal cancer. AMD3100 is the most frequently used FDA-approved antagonist that targets the CXCL12-CXCR4 axis in clinical trials. We aimed to explore the role of AMD3100 and its effect on peritoneal macrophages' functional phenotypes during colitis-associated tumorigenesis. We treated AMD3100 in a colitis-associated colon cancer mouse model and evaluated its effect on tumorigenesis. The phagocytosis activities of peritoneal macrophages were measured by flow cytometry. The proportions of macrophages and M1/M2 subpopulations were investigated by flow cytometry, ELISA, and immunochemistry. Serum levels of pro-inflammatory and anti-inflammatory cytokines were measured by LEGENDplex™ kits. Transwell assay and qRT-PCR were performed to investigate the direct effect of CXCL12 on macrophages in vitro. We demonstrated that AMD3100 treatment reduced the inflammatory damages in the colonic mucosal and ameliorated tumor development in experimental mice. We found that the phagocytosis activities of peritoneal macrophages fluctuated during colitis-associated tumorigenesis. The proportions of peritoneal macrophages and M1/M2 subpopulations, together with their metabolite and cytokines, changed dynamically in the process. Moreover, AMD3100 regulated the functional phenotypes of macrophages, including reducing the recruiting activity, promoting polarization to the M1 subpopulation, and reducing IL-12 and IL-23 levels in serum. Our study contributes to understanding dynamic changes of peritoneal macrophages upon AMD3100 treatment during tumorigenesis and sheds light on the potential therapeutic target of AMD3100 and peritoneal macrophages against colitis-associated colon cancer.

The duplexity of unconventional T cells in cancer

Unconventional T cells and their involvement in cancer are understudied in comparison to conventional T cells, but recent findings indicate that these cells play important roles in both cancer progression and inhibition. Here, we briefly review the dichotomous role of three unconventional T cell lineages: γδ T cells, MAIT cells and NKT cells. Studies using mouse models of cancer show how this unconventional trilogy interacts with cancer epithelial cells and other immune cell populations during tumour evolution. These reports highlight various potential avenues for therapeutic intervention that may be exploited for cancer immunotherapy.

IL-17: an important pathogenic factor in endometriosis

Interleukin-17 (IL-17) is known as a Th17-cell-derived proinflammatory cytokine, which plays a pivotal role in several inflammatory and autoimmune diseases such as systemic lupus erythematosus (SLE), rheumatoid arthritis, and psoriasis. Emerging evidence has shown that IL-17 is linked to endometriosis, although the etiology of endometriosis is still unknown. The IL-17 expression is up-regulated in serum, peritoneal fluid (PF) and endometriotic lesions from patients with endometriosis but the related regulation mechanisms are complex and obscure. Meanwhile, the specific roles of IL-17 in endometriosis are also worthy of further exploration. Through the integration and summary of literature, we conclude that the secretion of IL-17 increases under the regulation of ectopic microenvironment and other factors, and then IL-17 is deeply involved in endometriosis in the regulation of immune microenvironment, the invasion and growth of ectopic lesions, and so on, which implies its therapeutic value in this disorder.

A single-cell transcriptomic landscape of innate and adaptive intratumoral immunity in triple negative breast cancer during chemo- and immunotherapies

Breast cancer (BC) constitutes a major health problem worldwide, making it the most common malignancy in women. Current treatment options for BC depend primarily on histological type, molecular markers, clinical aggressiveness and stage of disease. Immunotherapy, such as αPD-1, have shown combinatorial clinical activity with chemotherapy in triple negative breast cancer (TNBC) delineating some therapeutic combinations as more effective than others. However, a clear overview of the main immune cell populations involved in these treatments has never been provided.

Here, an assessment of the immune landscape in the tumor microenvironment (TME) of two TNBC mouse models has been performed using single-cell RNA sequencing technology. Specifically, immune cells were evaluated in untreated conditions and after treatments with chemotherapy or immunotherapy used as single agents or in combination. A decrease of Treg was found in treatments with in vivo efficacy as well as γδ T cells, which have a pro-tumoral activity in mice. Focusing on Cd8 T cells, across all the conditions, a general increase of exhausted-like Cd8 T cells was confirmed in pre-clinical treatments with low efficacy and an opposite trend was found for the proliferative Cd8 T cells. Regarding macrophages, M2-like cells were enriched in treatments with low efficacy while M1-like macrophages followed an opposite trend. For both models, similar proportions of B cells were detected with an increase of proliferative B cells in treatments involving cisplatin in combination with αPD-1. The fine-scale characterization of the immune TME in this work can lead to new insights on the diagnosis and treatment of TNBC.

Translational randomized phase II trial of cabozantinib in combination with nivolumab in advanced, recurrent, or metastatic endometrial cancer

BACKGROUND

Combining immunotherapy and antiangiogenic agents is a promising treatment strategy in endometrial cancer. To date, no biomarkers for response have been identified and data on post-immunotherapy progression are lacking. We explored the combination of a checkpoint inhibitor (nivolumab) and an antiangiogenic agent (cabozantinib) in immunotherapy-naïve endometrial cancer and in patients whose disease progressed on previous immunotherapy with baseline biopsy for immune profiling.

PATIENTS AND METHODS

In this phase II trial (ClinicalTrials.gov NCT03367741, registered December 11, 2017), women with recurrent endometrial cancer were randomized 2:1 to nivolumab with cabozantinib (Arm A) or nivolumab alone (Arm B). The primary endpoint was Response Evaluation Criteria in Solid Tumors-defined progression-free survival (PFS). Patients with carcinosarcoma or prior immune checkpoint inhibitor received combination treatment (Arm C). Baseline biopsy and serial peripheral blood mononuclear cell (PBMC) samples were analyzed and associations between patient outcome and immune data from cytometry by time of flight (CyTOF) and PBMCs were explored.

RESULTS

Median PFS was 5.3 (90% CI 3.5 to 9.2) months in Arm A (n=36) and 1.9 (90% CI 1.6 to 3.4) months in Arm B (n=18) (HR=0.59, 90% CI 0.35 to 0.98; log-rank p=0.09, meeting the prespecified statistical significance criteria). The most common treatment-related adverse events in Arm A were diarrhea (50%) and elevated liver enzymes (aspartate aminotransferase 47%, alanine aminotransferase 42%). In-depth baseline CyTOF analysis across treatment arms (n=40) identified 35 immune-cell subsets. Among immunotherapy-pretreated patients in Arm C, non-progressors had significantly higher proportions of activated tissue-resident (CD103+CD69+) ɣδ T cells than progressors (adjusted p=0.009).

CONCLUSIONS

Adding cabozantinib to nivolumab significantly improved outcomes in heavily pretreated endometrial cancer. A subgroup of immunotherapy-pretreated patients identified by baseline immune profile and potentially benefiting from combination with antiangiogenics requires further investigation.

Immunological control of ovarian carcinoma by chemotherapy and targeted anticancer agents

At odds with other solid tumors, epithelial ovarian cancer (EOC) is poorly sensitive to immune checkpoint inhibitors (ICIs), largely reflecting active immunosuppression despite CD8⁺ T cell infiltration at baseline. Accumulating evidence indicates that both conventional chemotherapeutics and targeted anticancer agents commonly used in the clinical management of EOC not only mediate a cytostatic and cytotoxic activity against malignant cells, but also drive therapeutically relevant immunostimulatory or immunosuppressive effects. Here, we discuss such an immunomodulatory activity, with a specific focus on molecular and cellular pathways that can be harnessed to develop superior combinatorial regimens for clinical EOC care.

Cancer cell-expressed BTNL2 facilitates tumour immune escape via engagement with IL-17A-producing γδ T cells

Therapeutic blockade of the immune checkpoint proteins programmed cell death protein 1 (PD-1) and cytotoxic T lymphocyte antigen 4 (CTLA4) has transformed cancer treatment. However, the overall response rate to these treatments is low, suggesting that immune checkpoint activation is not the only mechanism leading to dysfunctional anti-tumour immunity. Here we show that butyrophilin-like protein 2 (BTNL2) is a potent suppressor of the anti-tumour immune response. Antibody-mediated blockade of BTNL2 attenuates tumour progression in multiple in vivo murine tumour models, resulting in prolonged survival of tumour-bearing mice. Mechanistically, BTNL2 interacts with local γδ T cell populations to promote IL-17A production in the tumour microenvironment. Inhibition of BTNL2 reduces the number of tumour-infiltrating IL-17A-producing γδ T cells and myeloid-derived suppressor cells, while facilitating cytotoxic CD8⁺ T cell accumulation. Furthermore, we find high BTNL2 expression in several human tumour samples from highly prevalent cancer types, which negatively correlates with overall patient survival. Thus, our results suggest that BTNL2 is a negative regulator of anti-tumour immunity and a potential target for cancer immunotherapy.

Cancer cells producing ligands for the immune checkpoint molecules PD-1 and CTLA-4 is an important mechanism of tumour immune resistance. Here authors show that BTNL2 expression on cancer cells generates a dysfunctional tumour immune microenvironment via promoting IL-17A-producing γδ T cells.

MicroRNA-181a restricts human γδ T cell differentiation by targeting Map3k2 and Notch2

γδ T cells are a conserved population of lymphocytes that contributes to anti-tumor responses through its overt type 1 inflammatory and cytotoxic properties. We have previously shown that human γδ T cells acquire this profile upon stimulation with IL-2 or IL-15, in a differentiation process dependent on MAPK/ERK signaling. Here, we identify microRNA-181a as a key modulator of human γδ T cell differentiation. We observe that miR-181a is highly expressed in patients with prostate cancer and that this pattern associates with lower expression of NKG2D, a critical mediator of cancer surveillance. Interestingly, miR-181a expression negatively correlates with an activated type 1 effector profile obtained from in vitro differentiated γδ T cells and miR-181a overexpression restricts their levels of NKG2D and TNF-α. Upon in silico analysis, we identify two miR-181a candidate targets, Map3k2 and Notch2, which we validate via overexpression coupled with luciferase assays. These results reveal a novel role for miR-181a as critical regulator of human γδ T cell differentiation and highlight its potential for manipulation of γδ T cells in next-generation immunotherapies.

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.

MAIT cells accumulate in ovarian cancer-elicited ascites where they retain their capacity to respond to MR1 ligands and cytokine cues

The low mutational burden of epithelial ovarian cancer (EOC) is an impediment to immunotherapies that rely on conventional MHC-restricted, neoantigen-reactive T lymphocytes. Mucosa-associated invariant T (MAIT) cells are MR1-restricted T cells with remarkable immunomodulatory properties. We sought to characterize intratumoral and ascitic MAIT cells in EOC. Single-cell RNA sequencing of six primary human tumor specimens demonstrated that MAIT cells were present at low frequencies within several tumors. When detectable, these cells highly expressed CD69 and VSIR, but otherwise exhibited a transcriptomic signature inconsistent with overt cellular activation and/or exhaustion. Unlike mainstream CD8⁺ T cells, CD8⁺ MAIT cells harbored high transcript levels of TNF, PRF1, GZMM and GNLY, suggesting their arming and cytotoxic potentials. In a congenic, MAIT cell-sufficient mouse model of EOC, MAIT and invariant natural killer T cells amassed in the peritoneal cavity where they showed robust IL-17A and IFN-γ production capacities, respectively. However, they gradually lost these functions with tumor progression. In a cohort of 23 EOC patients, MAIT cells were readily detectable in all ascitic fluids examined. In a sub-cohort in which we interrogated ascitic MAIT cells for functional impairments, several exhaustion markers, most notably VISTA, were present on the surface. However, ascitic MAIT cells were capable of producing IFN-γ, TNF-α and granzyme B, but neither IL-17A nor IL-10, in response to an MR1 ligand, bacterial lysates containing MR1 ligands, or a combination of IL-12 and IL-18. In conclusion, ascitic MAIT cells in EOC possess inducible effector functions that may be modified in future immunotherapeutic strategies.

γδT17/γδTreg cell subsets: a new paradigm for asthma treatment

Bronchial asthma (abbreviated as asthma), is a heterogeneous disease characterized by chronic airway inflammation and airway hyperresponsiveness. The main characteristics of asthma include variable reversible airflow limitation and airway remodeling. The pathogenesis of asthma is still unclear. Th1/Th2 imbalance, Th1 deficiency and Th2 hyperfunction are classic pathophysiological mechanisms of asthma. Some studies have shown that the imbalance of the Th1/Th2 cellular immune model and Th17/Treg imbalance play a key role in the occurrence and development of asthma; however, these imbalances do not fully explain the disease. In recent years, studies have shown that γδT and γδT17 cells are involved in the pathogenesis of asthma. γδTreg has a potential immunosuppressive function, but its regulatory mechanisms have not been fully elucidated. In this paper, we reviewed the role of γδT17/γδTreg cells in bronchial asthma, including the mechanisms of their development and activation. Here we propose that γδT17/Treg cell subsets contribute to the occurrence and development of asthma, constituting a novel potential target for asthma treatment.

Type I interferon supports γδ T-cell homeostasis and immunity through direct and indirect receptor signaling in mice

Interleukin (IL)-17-producing gamma delta (γδ) T (γδT17) cells are an essential part of innate type 3 immunity against numerous pathogens. At the same time, a large body of evidence from mouse models and human clinical studies suggests that γδT17 cells contribute to the pathogenesis of many inflammatory diseases as well as cancer. It is therefore relevant to elucidate their immunobiology in detail and identify molecules and pathways that can regulate their function. Herein, we investigated the importance of the type I interferon (IFN) signaling system in γδT17 homeostasis and activation. We found that the IFN alpha receptor 1 (IFNAR1) was critical to maintain their normal homeostasis and to promote their activation during cutaneous inflammation. However, this did not require γδT17-intrinsic expression of IFNAR1. In contrast, expression of IFNAR1 by γδT17 cells was required in order to suppress IL-17 production during viral infection. Our data delineate direct from indirect IFNAR1 signaling and reveal an important immunoregulatory role for both tonic and inducible type I IFN in γδT17 cells.

γδT Cells Are Required for CD8+ T Cell Response to Vaccinia Viral Infection

Vaccinia virus (VV) is the most studied member of the poxvirus family, is responsible for the successful elimination of smallpox worldwide, and has been developed as a vaccine vehicle for infectious diseases and cancer immunotherapy. We have previously shown that the unique potency of VV in the activation of CD8+ T cell response is dependent on efficient activation of the innate immune system through Toll-like receptor (TLR)-dependent and -independent pathways. However, it remains incompletely defined what regulate CD8+ T cell response to VV infection. In this study, we showed that γδT cells play an important role in promoting CD8+ T cell response to VV infection. We found that γδT cells can directly present viral antigens in the context of MHC-I for CD8+ T cell activation to VV in vivo, and we further demonstrated that cell-intrinsic MyD88 signaling in γδT cells is required for activation of γδT cells and CD8+ T cells. These results illustrate a critical role for γδT cells in the regulation of adaptive T cell response to viral infection and may shed light on the design of more effective vaccine strategies based on manipulation of γδT cells.

Immunoregulation by type I interferons in the peritoneal cavity

The peritoneal cavity, a fluid-containing potential space surrounding the abdominal and pelvic organs, is home to a rich network of immune cells that maintain tissue homeostasis and provide protection against infection. However, under pathological conditions such as peritonitis, endometriosis, and peritoneal carcinomatosis, the peritoneal immune system can become dysregulated, resulting in nonresolving inflammation and disease progression. An enhanced understanding of the factors that regulate peritoneal immune cells under both homeostatic conditions and in disease contexts is therefore required to identify new treatment strategies for these often life-limiting peritoneal pathologies. Type I interferons (T1IFNs) are a family of cytokines with broad immunoregulatory functions, which provide defense against viruses, bacteria, and cancer. There have been numerous reports of immunoregulation by T1IFNs within the peritoneal cavity, which can contribute to both the resolution or propagation of peritoneal disease states, depending on the specifics of the disease setting and local environment. In this review, we provide an overview of the major immune cell populations that reside in the peritoneal cavity (or infiltrate it under inflammatory conditions) and highlight their contribution to the initiation, progression, or resolution of peritoneal diseases. Additionally, we will discuss the role of T1IFNs in the regulation of peritoneal immune cells, and summarize the results of laboratory studies and clinical trials which have investigated T1IFNs in peritonitis/sepsis, endometriosis, and peritoneal carcinomatosis.

Bringing Macrophages to the Frontline against Cancer: Current Immunotherapies Targeting Macrophages

Macrophages are found in all tissues and display outstanding functional diversity. From embryo to birth and throughout adult life, they play critical roles in development, homeostasis, tissue repair, immunity, and, importantly, in the control of cancer growth. In this review, we will briefly detail the multi-functional, protumoral, and antitumoral roles of macrophages in the tumor microenvironment. Our objective is to focus on the ever-growing therapeutic opportunities, with promising preclinical and clinical results developed in recent years, to modulate the contribution of macrophages in oncologic diseases. While the majority of cancer immunotherapies target T cells, we believe that macrophages have a promising therapeutic potential as tumoricidal effectors and in mobilizing their surroundings towards antitumor immunity to efficiently limit cancer progression.

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.

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.

Regulation and Functions of Protumoral Unconventional T Cells in Solid Tumors

The vast majority of studies on T cell biology in tumor immunity have focused on peptide-reactive conventional T cells that are restricted to polymorphic major histocompatibility complex molecules. However, emerging evidence indicated that unconventional T cells, including γδ T cells, natural killer T (NKT) cells and mucosal-associated invariant T (MAIT) cells are also involved in tumor immunity. Unconventional T cells span the innate-adaptive continuum and possess the unique ability to rapidly react to nonpeptide antigens via their conserved T cell receptors (TCRs) and/or to activating cytokines to orchestrate many aspects of the immune response. Since unconventional T cell lineages comprise discrete functional subsets, they can mediate both anti- and protumoral activities. Here, we review the current understanding of the functions and regulatory mechanisms of protumoral unconventional T cell subsets in the tumor environment. We also discuss the therapeutic potential of these deleterious subsets in solid cancers and why further feasibility studies are warranted.

Characterization of ascites- and tumor-infiltrating γδ T cells reveals distinct repertoires and a beneficial role in ovarian cancer

The role of γδ T cells in antitumor immunity has been under investigation for the past two decades, but little is known about their contribution to clinical outcomes in patients. Here, we set out to define the clonotypic, phenotypic, and functional features of γδ T cells in peripheral blood, ascites, and metastatic tumor tissue from patients with advanced epithelial ovarian cancer. T cell receptor (TCR) sequencing of the γ chain revealed that tumor-infiltrating γδ T cells have a unique and skewed repertoire with high TCR diversity and low clonality. In contrast, ascites-derived γδ T cells presented a lower TCR diversity and higher clonality, suggesting a TCR-dependent clonal focusing at this site. Further investigation showed that tumor samples had abundant γδ T cells with a tissue-resident, activation-associated phenotype, less usage of Vγ9 and an impaired response to adaptive-associated stimuli, implying an innate-like activation pathway, rather than an adaptive TCR-engaging pathway, at these tumor sites. Furthermore, high γδ T cell cytokine responsiveness upon stimulation was associated with a favorable outcome for patients in terms of both overall survival and reduced residual tumor burden after primary surgery. Last, the functionality of γδ T cells and patient survival were negatively affected by the proportions of CD39-expressing T cells, highlighting the potential of CD39 as a target to improve γδ T cell responses and unleash their antitumor capabilities.

In respond to commensal bacteria: γδT cells play a pleiotropic role in tumor immunity

γδT cells are a mixture of innate programming and acquired adaptability that bridge the adaptive and innate immune systems. γδT cells are mainly classified as tissue-resident Vδ1 or circulating Vδ2 γδT cells. In the tumor microenvironment, tumor immunity is influenced by the increased quantity and phenotype plasticity of γδT cells. Commensal bacteria are ubiquitous in the human body, and they have been confirmed to exist in various tumor tissues. With the participation of commensal bacteria, γδT cells maintain homeostasis and are activated to affect the development and progression of tumors. Here, we summarize the relationship between γδT cells and commensal bacteria, the potential protumor and antitumor effects underlying γδT cells, and the new developments in γδT cell-based tumor therapy which is expected to open new opportunities for tumor immunotherapy.