GITR: a modulator of immune response and inflammation

Integrated transcriptomic and immunological profiling reveals new diagnostic and prognostic models for cutaneous melanoma

The mortality rate associated with cutaneous melanoma (SKCM) remains alarmingly high, highlighting the urgent need for a deeper understanding of its molecular underpinnings. In our study, we leveraged bulk transcriptome sequencing data from the SKCM cohort available in public databases such as TCGA and GEO. We utilized distinct datasets for training and validation purposes and also incorporated mutation and clinical data from TCGA, along with single-cell sequencing data from GEO. Through dimensionality reduction, we annotated cell subtypes within the single-cell data and analyzed the expression of tumor-related pathways across these subtypes. We identified differentially expressed genes (DEGs) in the training set, which were further refined using the Least Absolute Shrinkage and Selection Operator (LASSO) machine learning algorithm, employing tenfold cross-validation. This enabled the construction of a prognostic model, whose diagnostic efficacy we subsequently validated. We conducted Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses on the DEGs, and performed immunological profiling on two risk groups to elucidate the relationship between model genes and the immune responses relevant to SKCM diagnosis, treatment, and prognosis. We also knocked down the GMR6 expression level in the melanoma cells and verified its effect on cancer through multiple experiments. The results indicate that the GMR6 gene plays a role in promoting the proliferation, invasion, and migration of cancer cells in human melanoma. Our findings offer novel insights and a theoretical framework that could enhance prognosis, treatment, and drug development strategies for SKCM, potentially leading to more precise therapeutic interventions.

A comprehensive analysis of the immune system in healthy Vietnamese people

Lifestyle, diet, socioeconomic status and genetics all contribute to heterogeneity in immune responses. Vietnam is plagued with a variety of health problems, but there are no available data on immune system values in the Vietnamese population. This study aimed to establish reference intervals for immune cell parameters specific to the healthy Vietnamese population by utilizing multi-color flow cytometry (MCFC). We provide a comprehensive analysis of total leukocyte count, quantitative and qualitative shifts within lymphocyte subsets, serum and cytokine and chemokine levels and functional attributes of key immune cells including B cells, T cells, natural killer (NK) cells and their respective subpopulations. By establishing these reference values for the Vietnamese population, these data contribute significantly to our understanding of the human immune system variations across diverse populations. These data will be of substantial comparative value and be instrumental in developing personalized medical approaches and optimizing diagnostic strategies for individuals based on their unique immune profiles.

Expression patterns of novel immunotherapy targets in intermediate- and high-grade lung neuroendocrine neoplasms

BACKGROUND

Advancements in immunotherapeutic approaches only had a modest impact on the therapy of lung neuroendocrine neoplasms (LNENs). Our multicenter study aimed to investigate the expression patterns of novel immunotherapy targets in intermediate- and high-grade LNENs.

METHODS

The expressions of V-domain Ig suppressor of T cell activation (VISTA), OX40L, Glucocorticoid-induced TNF receptor (GITR), and T cell immunoglobulin and mucin domain 3 (TIM3) proteins were measured by immunohistochemistry in surgically resected tumor samples of 26 atypical carcinoid (AC), 49 large cell neuroendocrine lung cancer (LCNEC), and 66 small cell lung cancer (SCLC) patients. Tumor and immune cells were separately scored.

RESULTS

Tumor cell TIM3 expression was the highest in ACs (p < 0.001), whereas elevated tumor cell GITR levels were characteristic for both ACs and SCLCs (p < 0.001 and p = 0.011, respectively). OX40L expression of tumor cells was considerably lower in ACs (vs. SCLCs; p < 0.001). Tumor cell VISTA expression was consistently low in LNENs, with no significant differences across histological subtypes. ACs were the least immunogenic tumors concerning immune cell abundance (p < 0.001). Immune cell VISTA and GITR expressions were also significantly lower in these intermediate-grade malignancies than in SCLCs or in LCNECs. Immune cell TIM3 and GITR expressions were associated with borderline prognostic significance in our multivariate model (p = 0.057 and p = 0.071, respectively).

CONCLUSIONS

LNEN subtypes have characteristic and widely divergent VISTA, OX40L, GITR, and TIM3 protein expressions. By shedding light on the different expression patterns of these immunotherapy targets, the current multicenter study provides support for the future implementation of novel immunotherapeutic approaches.

TRAF1 from a Structural Perspective

Tumor necrosis factor receptor-associated factor (TRAF) proteins play pivotal roles in a multitude of cellular signaling pathways, encompassing immune response, cell fate determination, development, and thrombosis. Their involvement in these processes hinges largely on their ability to interact directly with diverse receptors via the TRAF domain. Given the limited binding interface, understanding how specific TRAF domains engage with various receptors and how structurally similar binding interfaces of TRAF family members adapt their distinct binding partners has been the subject of extensive structural investigations over several decades. This review presents an in-depth exploration of the current insights into the structural and molecular diversity exhibited by the TRAF domain and TRAF-binding motifs across a range of receptors, with a specific focus on TRAF1.

Transcriptomic profiling of the acute mucosal response to local food injections in adults with eosinophilic esophagitis

BACKGROUND

Exposure of the esophageal mucosa to food allergens can cause acute mucosal responses in patients with eosinophilic esophagitis (EoE), but the underlying local immune mechanisms driving these acute responses are not well understood.

OBJECTIVE

We sought to gain insight into the early transcriptomic changes that occur during an acute mucosal response to food allergens in EoE.

METHODS

Bulk RNA sequencing was performed on esophageal biopsy specimens from adult patients with EoE (n = 5) collected before and 20 minutes after intramucosal injection of various food extracts in the esophagus. Baseline biopsy specimens from control subjects without EoE (n = 5) were also included.

RESULTS

At baseline, the transcriptome of the patients with EoE showed increased expression of genes related to an EoE signature. After local food injection, we identified 40 genes with a potential role in the early immune response to food allergens (most notably CEBPB, IL1B, TNFSF18, PHLDA2, and SLC15A3). These 40 genes were enriched in processes related to immune activation, such as the acute-phase response, cellular responses to external stimuli, and cell population proliferation. TNFSF18 (also called GITRL), a member of the TNF superfamily that is best studied for its costimulatory effect on T cells, was the most dysregulated early EoE gene, showing a 12-fold increase compared with baseline and an 18-fold increase compared with a negative visual response. Further experiments showed that the esophageal epithelium may be an important source of TNFSF18 in EoE, which was rapidly induced by costimulating esophageal epithelial cells with the EoE-relevant cytokines IL-13 and TNF-α.

CONCLUSIONS

Our data provide unprecedented insight into the transcriptomic changes that mediate the acute mucosal immune response to food allergens in EoE and suggest that TNFSF18 may be an important effector molecule in this response.

GITR and TIGIT immunotherapy provokes divergent multicellular responses in the tumor microenvironment of gastrointestinal cancers

BACKGROUND

Understanding the mechanistic effects of novel immunotherapy agents is critical to improving their successful clinical translation. These effects need to be studied in preclinical models that maintain the heterogenous tumor microenvironment (TME) and dysfunctional cell states found in a patient's tumor. We investigated immunotherapy perturbations targeting co-stimulatory molecule GITR and co-inhibitory immune checkpoint TIGIT in a patient-derived ex vivo system that maintains the TME in its near-native state. Leveraging single-cell genomics, we identified cell type-specific transcriptional reprogramming in response to immunotherapy perturbations.

METHODS

We generated ex vivo tumor slice cultures from fresh surgical resections of gastric and colon cancer and treated them with GITR agonist or TIGIT antagonist antibodies. We applied paired single-cell RNA and TCR sequencing to the original surgical resections, control, and treated ex vivo tumor slice cultures. We additionally confirmed target expression using multiplex immunofluorescence and validated our findings with RNA in situ hybridization.

RESULTS

We confirmed that tumor slice cultures maintained the cell types, transcriptional cell states and proportions of the original surgical resection. The GITR agonist was limited to increasing effector gene expression only in cytotoxic CD8 T cells. Dysfunctional exhausted CD8 T cells did not respond to GITR agonist. In contrast, the TIGIT antagonist increased TCR signaling and activated both cytotoxic and dysfunctional CD8 T cells. This included cells corresponding to TCR clonotypes with features indicative of potential tumor antigen reactivity. The TIGIT antagonist also activated T follicular helper-like cells and dendritic cells, and reduced markers of immunosuppression in regulatory T cells.

CONCLUSIONS

We identified novel cellular mechanisms of action of GITR and TIGIT immunotherapy in the patients' TME. Unlike the GITR agonist that generated a limited transcriptional response, TIGIT antagonist orchestrated a multicellular response involving CD8 T cells, T follicular helper-like cells, dendritic cells, and regulatory T cells. Our experimental strategy combining single-cell genomics with preclinical models can successfully identify mechanisms of action of novel immunotherapy agents. Understanding the cellular and transcriptional mechanisms of response or resistance will aid in prioritization of targets and their clinical translation.

Single-cell mass cytometric analysis of peripheral immunity and multiplex plasma marker profiling of non-small cell lung cancer patients receiving PD-1 targeting immune checkpoint inhibitors in comparison with platinum-based chemotherapy

Introduction

The effect of platinum-based chemotherapy (Chem.) and second- or multiple- line immune checkpoint PD-1 blocking therapy by Nivolumab or Pembrolizumab (ICI) was assayed in the peripheral blood of non-small cell lung cancer (NSCLC) patients.

Methods

Flow cytometry was used to detect NSCLC-related antigen binding IgG antibodies. The Luminex MagPix multiplex bead-based cytokine/chemokine detecting system was used to quantitatively measure 17 soluble markers in the plasma samples. Single-cell mass cytometry was applied for the immunophenotyping of peripheral leukocytes.

Results

The incubation of patient derived plasma with human NSCLC tumor cell lines, such as A549, H1975, and H1650, detected NSCLC-specific antibodies reaching a maximum of up to 32% reactive IgG-positive NSCLC cells. The following markers were detected in significantly higher concentration in the plasma of Chem. group versus healthy non-smoker and smoker controls: BTLA, CD27, CD28, CD40, CD80, CD86, GITRL, ICOS, LAG-3, PD-1, PD-L1, and TLR-2. The following markers were detected in significantly higher concentration in the plasma of ICI group versus healthy non-smoker and smoker controls: CD27, CD28, CD40, GITRL, LAG-3, PD-1, PD-L1, and TLR-2. We showed the induction of CD69 and IL-2R on CD4+ CD25+ T-cells upon chemotherapy; the exhaustion of one CD8+ T-cell population was detected by the loss of CD127 and a decrease in CD27. CD19+CD20+, CD79B+, or activated B-cell subtypes showed CD69 increase and downregulation of BTLA, CD27, and IL-2R in NSCLC patients following chemotherapy or ICI.

Discussion

Peripheral immunophenotype caused by chemotherapy or PD-1 blocking was shown in the context of advanced NSCLC.

Regulating the regulatory T cells as cell therapies in autoimmunity and cancer

Regulatory T cells (Tregs), possess a pivotal function in the maintenance of immune homeostasis. The dysregulated activity of Tregs has been associated with the onset of autoimmune diseases and cancer. Hence, Tregs are promising targets for interventions aimed at steering the immune response toward the desired path, either by augmenting the immune system to eliminate infected and cancerous cells or by dampening it to curtail the damage to self-tissues in autoimmune disorders. The activation of Tregs has been observed to have a potent immunosuppressive effect against T cells that respond to self-antigens, thus safeguarding our body against autoimmunity. Therefore, promoting Treg cell stability presents a promising strategy for preventing or managing chronic inflammation that results from various autoimmune diseases. On the other hand, Tregs have been found to be overactivated in several forms of cancer, and their role as immune response regulators with immunosuppressive properties poses a significant impediment to the successful implementation of cancer immunotherapy. However, the targeting of Tregs in a systemic manner may lead to the onset of severe inflammation and autoimmune toxicity. It is imperative to develop more selective methods for targeting the function of Tregs in tumors. In this review, our objective is to elucidate the function of Tregs in tumors and autoimmunity while also delving into numerous therapeutic strategies for reprogramming their function. Our focus is on reprogramming Tregs in a highly activated phenotype driven by the activation of key surface receptors and metabolic reprogramming. Furthermore, we examine Treg-based therapies in autoimmunity, with a specific emphasis on Chimeric Antigen Receptor (CAR)-Treg therapy and T-cell receptor (TCR)-Treg therapy. Finally, we discuss key challenges and the future steps in reprogramming Tregs that could lead to the development of novel and effective cancer immunotherapies.

Prognostic Factors in Advanced Non-Small Cell Lung Cancer Patients Treated with Immunotherapy

Taking into account the huge epidemiologic impact of lung cancer (in 2020, lung cancer accounted for 2,206,771 of the cases and for 1,796,144 of the cancer-related deaths, representing the second most common cancer in female patients, the most common cancer in male patients, and the second most common cancer in male and female patients) and the current lack of recommendations in terms of prognostic factors for patients selection and management, this article aims to provide an overview of the current landscape in terms of currently available immunotherapy treatments and the most promising assessed prognostic biomarkers, highlighting the current state-of-the-art and hinting at future challenges.

TNF superfamily control of tissue remodeling and fibrosis

Fibrosis is the result of extracellular matrix protein deposition and remains a leading cause of death in USA. Despite major advances in recent years, there remains an unmet need to develop therapeutic options that can effectively degrade or reverse fibrosis. The tumor necrosis super family (TNFSF) members, previously studied for their roles in inflammation and cell death, now represent attractive therapeutic targets for fibrotic diseases. In this review, we will summarize select TNFSF and their involvement in fibrosis of the lungs, the heart, the skin, the gastrointestinal tract, the kidney, and the liver. We will emphasize their direct activity on epithelial cells, fibroblasts, and smooth muscle cells. We will further report on major clinical trials targeting these ligands. Whether in isolation or in combination with other anti-TNFSF member or treatment, targeting this superfamily remains key to improve efficacy and selectivity of currently available therapies for fibrosis.

Targeting GITR in cancer immunotherapy - there is no perfect knowledge

Glucocorticoid-induced TNFR-related protein (GITR) belongs to the TNFR superfamily (TNFRSF) and stimulates both the acquired and innate immunity. GITR is broadly expressed on immune cells, particularly regulatory T cells (Tregs) and natural killer (NK) cells. Given its potential to promote T effector function and impede Treg immune suppression, GITR is an attractive target for cancer immunotherapy. Preclinically, GITR agonists have demonstrated potent anti-tumor efficacy singly and in combination with a variety of agents, including PD-1 blockade. Multiple GITR agonists have been advanced into the clinic, although the experience with these agents has been disappointing. Recent mechanistic insights into the roles of antibody structure, valency, and Fc functionality in mediating anti-tumor efficacy may explain some of the apparent inconsistency or discordance between preclinical data and observed clinical efficacy.

GITR and TIGIT immunotherapy provokes divergent multi-cellular responses in the tumor microenvironment of gastrointestinal cancers

Understanding the cellular mechanisms of novel immunotherapy agents in the human tumor microenvironment (TME) is critical to their clinical success. We examined GITR and TIGIT immunotherapy in gastric and colon cancer patients using ex vivo slice tumor slice cultures derived from cancer surgical resections. This primary culture system maintains the original TME in a near-native state. We applied paired single-cell RNA and TCR sequencing to identify cell type specific transcriptional reprogramming. The GITR agonist was limited to increasing effector gene expression only in cytotoxic CD8 T cells. The TIGIT antagonist increased TCR signaling and activated both cytotoxic and dysfunctional CD8 T cells, including clonotypes indicative of potential tumor antigen reactivity. The TIGIT antagonist also activated T follicular helper-like cells and dendritic cells, and reduced markers of immunosuppression in regulatory T cells. Overall, we identified cellular mechanisms of action of these two immunotherapy targets in the patients' TME.

Quantitative systems pharmacology model of GITR-mediated T cell dynamics in tumor microenvironment

T cell interaction in the tumor microenvironment is a key component of immuno-oncology therapy. Glucocorticoid-induced tumor necrosis factor receptor (TNFR)-related protein (GITR) is expressed on immune cells including regulatory T cells (Tregs) and effector T cells (Teffs). Preclinical data suggest that agonism of GITR in combination with Fc-γ receptor-mediated depletion of Tregs results in increased intratumoral Teff:Treg ratio and tumor shrinkage. A novel quantitative systems pharmacology (QSP) model was developed for the murine anti-GITR agonist antibody, DTA-1.mIgG2a, to describe the kinetics of intratumoral Tregs and Teffs in Colon26 and A20 syngeneic mouse tumor models. It adequately captured the time profiles of intratumoral Treg and Teff and serum DTA-1.mIgG2a and soluble GITR concentrations in both mouse models, and described the response differences between the two models. The QSP model provides a quantitative understanding of the trade-off between maximizing Treg depletion versus Teff agonism, and offers insights to optimize drug design and dose regimen.

Predictive biomarkers for the responsiveness of recurrent glioblastomas to activated killer cell immunotherapy

BACKGROUND

Recurrent glioblastoma multiforme (GBM) is a highly aggressive primary malignant brain tumor that is resistant to existing treatments. Recently, we reported that activated autologous natural killer (NK) cell therapeutics induced a marked increase in survival of some patients with recurrent GBM.

METHODS

To identify biomarkers that predict responsiveness to NK cell therapeutics, we examined immune profiles in tumor tissues using NanoString nCounter analysis and compared the profiles between 5 responders and 7 non-responders. Through a three-step data analysis, we identified three candidate biomarkers (TNFRSF18, TNFSF4, and IL12RB2) and performed validation with qRT-PCR. We also performed immunohistochemistry and a NK cell migration assay to assess the function of these genes.

RESULTS

Responders had higher expression of many immune-signaling genes compared with non-responders, which suggests an immune-active tumor microenvironment in responders. The random forest model that identified TNFRSF18, TNFSF4, and IL12RB2 showed a 100% accuracy (95% CI 73.5-100%) for predicting the response to NK cell therapeutics. The expression levels of these three genes by qRT-PCR were highly correlated with the NanoString levels, with high Pearson's correlation coefficients (0.419 (TNFRSF18), 0.700 (TNFSF4), and 0.502 (IL12RB2)); their prediction performance also showed 100% accuracy (95% CI 73.54-100%) by logistic regression modeling. We also demonstrated that these genes were related to cytotoxic T cell infiltration and NK cell migration in the tumor microenvironment.

CONCLUSION

We identified TNFRSF18, TNFSF4, and IL12RB2 as biomarkers that predict response to NK cell therapeutics in recurrent GBM, which might provide a new treatment strategy for this highly aggressive tumor.

In or out of control: Modulating regulatory T cell homeostasis and function with immune checkpoint pathways

Regulatory T cells (Tregs) are the master regulators of immunity and they have been implicated in different disease states such as infection, autoimmunity and cancer. Since their discovery, many studies have focused on understanding Treg development, differentiation, and function. While there are many players in the generation and function of truly suppressive Tregs, the role of checkpoint pathways in these processes have been studied extensively. In this paper, we systematically review the role of different checkpoint pathways in Treg homeostasis and function. We describe how co-stimulatory and co-inhibitory pathways modulate Treg homeostasis and function and highlight data from mouse and human studies. Multiple checkpoint pathways are being targeted in cancer and autoimmunity; therefore, we share insights from the clinic and discuss the effect of experimental and approved therapeutics on Treg biology.

Model-informed drug development for immuno-oncology agonistic anti-GITR antibody GWN323: Dose selection based on MABEL and biologically active dose

GWN323, an agonistic human anti-GITR (glucocorticoid-induced TNFR-related protein) IgG1 antibody, was studied clinically as an immuno-oncology therapeutic agent. A model-based minimum anticipated biological effect level (MABEL) approach integrating in vitro and in vivo data informed dose selection for the first-in-human (FIH) study. Data evaluated included pharmacokinetics (PK) of DTA-1.mIgG2a (mouse surrogate GITR antibody for GWN323), target-engagement pharmacodynamic (PD) marker soluble GITR (sGITR), tumor shrinkage in Colon26 syngeneic mice administered with DTA-1.mIgG2a, cytokine release of GWN323 in human peripheral blood mononuclear cells, and GITR binding affinity. A PK model was developed to describe DTA-1.mIgG2a PK, and its relationship with sGITR was also modeled. Human GWN323 PK was predicted by allometric scaling of mouse PK. Based on the totality of PK/PD modeling and in vitro and in vivo pharmacology and toxicology data, MABEL was estimated to be 3-10 mg once every 3 weeks (Q3W), which informed the starting dose selection of the FIH study. Based on tumor kinetic PK/PD modeling of tumor inhibition by DTA-1.mIgG2a in Colon26 mice and the predicted human PK of GWN323, the biologically active dose of GWN323 was predicted to be 350 mg Q3W, which informed the dose escalation of the FIH study. GWN323 PK from the FIH study was described by a population PK model; the relationship with ex vivo interleukin-2 release, a target-engagement marker, was also modeled. The clinical PK/PD modeling data supported the biological active dose projected from the translational PK/PD modeling in a "learn and confirm" paradigm of model-informed drug development of GWN323.

GITR antibodies in cancer: not ready for prime time

GITR agonistic antibodies are expected to increase the antitumor response mainly by reducing the effect of Foxp3+ T regulatory cells. TRX-518 is a novel GITR agonist that has shown good pharmacodynamic activity by depleting T regs in preclinical models, with limited clinical activity demonstrated in patients with advanced solid tumors.

Phase IB Study of GITR Agonist Antibody TRX518 Singly and in Combination with Gemcitabine, Pembrolizumab or Nivolumab in Patients with Advanced Solid Tumors

Purpose: TRX518 is a monoclonal antibody engaging the glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR). This open-label, phase I study (TRX518-003) evaluated the safety and efficacy of repeated dose TRX518 monotherapy and combination with gemcitabine, pembrolizumab or nivolumab in advanced solid tumors. Experimental Design: TRX518 monotherapy was dose-escalated (Part A) and expanded (Part B) up to 4 mg/kg load, 1 mg/kg Q3W. Parts C-E included dose-escalation (2mg/kg and 4 mg/kg loading followed by 1mg/kg) and dose-expansion (4mg/kg load) phases with gemcitabine (Part C), pembrolizumab (Part D) or nivolumab (Part E). Primary endpoints included incidence of dose-limiting toxicities (DLTs), serious adverse events (SAEs), and pharmacokinetics. Secondary endpoints were efficacy and pharmacodynamics. Results:109 patients received TRX518: 43 (Parts A+B), 30 (Part C), 26 (Part D), and 10 (Part E) respectively. 67% of patients in Parts D+E had received prior anti-PD(L)1 or anti-CTLA-4. No DLTs, treatment-related SAEs and/or G4/5 AEs were observed with TRX518 monotherapy. In Parts C-E, no DLTs were observed, although TRX518-related SAEs were reported in 3.3% (Part C) and 10.0% (Part E) respectively. Objective response rate was 3.2%, 3.8%, 4% and 12.5% in Parts A+B, C, D and E respectively. TRX518 affected peripheral and intratumoral regulatory T cells (Tregs) with different kinetics depending on the combination regimen. Responses with TRX518 monotherapy+anti-PD1 combination were associated with intratumoral Treg reductions and CD8 increases and activation after treatment. Conclusions:TRX518 showed an acceptable safety profile with pharmacodynamic activity. Repeated dose TRX518 monotherapy and in combination resulted in limited clinical responses associated with immune activation.

The Implementation of TNFRSF Co-Stimulatory Domains in CAR-T Cells for Optimal Functional Activity

The Tumor Necrosis Factor Receptor Superfamily (TNFRSF) is a large and important immunoregulatory family that provides crucial co-stimulatory signals to many if not all immune effector cells. Each co-stimulatory TNFRSF member has a distinct expression profile and a unique functional impact on various types of cells and at different stages of the immune response. Correspondingly, exploiting TNFRSF-mediated signaling for cancer immunotherapy has been a major field of interest, with various therapeutic TNFRSF-exploiting anti-cancer approaches such as 4-1BB and CD27 agonistic antibodies being evaluated (pre)clinically. A further application of TNFRSF signaling is the incorporation of the intracellular co-stimulatory domain of a TNFRSF into so-called Chimeric Antigen Receptor (CAR) constructs for CAR-T cell therapy, the most prominent example of which is the 4-1BB co-stimulatory domain included in the clinically approved product Kymriah. In fact, CAR-T cell function can be clearly influenced by the unique co-stimulatory features of members of the TNFRSF. Here, we review a select group of TNFRSF members (4-1BB, OX40, CD27, CD40, HVEM, and GITR) that have gained prominence as co-stimulatory domains in CAR-T cell therapy and illustrate the unique features that each confers to CAR-T cells.

Immune System in Action

Tumor exists as a complex network of structures with an ability to evolve and evade the host immune surveillance mechanism. The immune milieu which includes macrophages, dendritic cells, natural killer cells, neutrophils, mast cells, B cells, and T cells is found in the core, the invasive margin, or the adjacent stromal or lymphoid component of the tumor. The immune infiltrate is heterogeneous and varies within a patient and between patients of the same tumor histology. The location, density, functionality, and the crosstalk between the immune cells in the tumor microenvironment influence the nature of immune response, prognosis, and treatment outcomes in cancer patients. Therefore, an understanding of the characteristics of the immune cells and their role in tumor immune surveillance is of paramount importance to identify immune targets and to develop novel immune therapeutics in the war against cancer. In this chapter, we provide an overview of the individual components of the human immune system and the translational relevance of predictive biomarkers.

GITR Promotes the Polarization of TFH-Like Cells in Helicobacter pylori-Positive Gastritis

Gastric CD4⁺T cells contribute to Helicobacter pylori (H. pylori)-induced gastritis by amplifying mucosal inflammation and exacerbating mucosal injuries. However, the pathogenic CD4⁺ T cell subset involved in gastritis and the potential regulators are still unclear. Here we identified an IL-21-producing gastric CD4⁺T cell subset, which exhibited tissue-resident CXCR5⁻BTLA⁻PD-1^hi TFH-like phenotype in H. pylori-positive gastritis patients. Meanwhile, we identified glucocorticoid-induced tumor necrosis factor receptor (GITR) as an important regulator to facilitate IL-21 production by CD4⁺T cells and accelerate mucosal inflammation in gastritis patients with H. pylori infection. Moreover, GITR expression was increased in gastric CD4⁺T cells of gastritis patients compared to healthy controls, along with the upregulated expression of its ligand GITRL in mucosal macrophages (Mϕ) of gastritis patients. Further observations showed that the activation of GITR/GITRL signal promoted the IL-21 production of CD4⁺T cells via the STAT3 pathway. Besides this, IL-21 from CD4⁺T cells induced the proliferation of B cell and promoted the production of inflammatory cytokines IL-1β and IL-6 and chemokines MIP-3α and CCL-25 as well as matrix metalloproteinase (MMP)-3 and MMP-9 by human gastric epithelial cells, suggesting the facilitating effect of IL-21-producing CD4⁺T cells on mucosal inflammation and injuries. Taking these data together, we revealed that GITR/GITRL signal promoted the polarization of mucosal IL-21-producing CD4⁺T cells in H. pylori-positive gastritis, which may provide therapeutic strategies for the clinical treatment of H. pylori-induced gastritis.

Impact of immune checkpoint molecules on FoxP3+ Treg cells and related cytokines in patients with acute and chronic brucellosis

Background

The immunoregulatory functions of regulatory T cells (Tregs) in the development and progression of some chronic infectious diseases are mediated by immune checkpoint molecules and immunosuppressive cytokines. However, little is known about the immunosuppressive functions of Tregs in human brucellosis, which is a major burden in low-income countries. In this study, expressions of immune checkpoint molecules and Treg-related cytokines in patients with acute and chronic Brucella infection were evaluated to explore their impact at different stages of infection.

Methods

Forty patients with acute brucellosis and 19 patients with chronic brucellosis admitted to the Third People’s Hospital of Linfen in Shanxi Province between August 2016 and November 2017 were enrolled. Serum and peripheral blood mononuclear cells were isolated from patients before antibiotic treatment and from 30 healthy subjects. The frequency of Tregs (CD4⁺ CD25⁺ FoxP3⁺ T cells) and expression of CTLA-4, GITR, and PD-1 on Treg cells were detected by flow cytometry. Levels of Treg-related cytokines, including IL-35, TGF-β1, and IL-10, were measured by customised multiplex cytokine assays using the Luminex platform.

Results

The frequency of Tregs was higher in chronic patients than in healthy controls (P = 0.026) and acute patients (P = 0.042); The frequency of CTLA-4⁺ Tregs in chronic patients was significantly higher than that in healthy controls (P = 0.011). The frequencies of GITR⁺ and PD-1⁺ Tregs were significantly higher in acute and chronic patients than in healthy controls (P < 0.05), with no significant difference between the acute and chronic groups (all P > 0.05). Serum TGF-β1 levels were higher in chronic patients (P = 0.029) and serum IL-10 levels were higher in acute patients (P = 0.033) than in healthy controls. We detected weak correlations between serum TGF-β1 levels and the frequencies of Tregs (R = 0.309, P = 0.031) and CTLA-4⁺ Tregs (R = 0.302, P = 0.035).

Conclusions

Treg cell immunity is involved in the chronicity of Brucella infection and indicates the implication of Tregs in the prognosis of brucellosis. CTLA-4 and TGF-β1 may contribute to Tregs-mediated immunosuppression in the chronic infection stage of a Brucella infection.

Atypical TNF-TNFR superfamily binding interface in the GITR-GITRL complex for T cell activation

Glucocorticoid-induced tumor necrosis factor receptor family-related protein (GITR) is a critical regulatory molecule in modulation of T cell immune responses. Here we report the mouse GITR (mGITR) and mGITR ligand (mGITRL) complex structure and find that the binding interface of mGITR and mGITRL is distinct from the typical tumor necrosis factor superfamily (TNFSF)/TNF receptor superfamily (TNFRSF) members. mGITR binds to its ligand with a single domain, whereas the binding interface on mGITRL is located on the side, which is distal from conserved binding sites of TNFSF molecules. Mutational analysis reveals that the binding interface of GITR/GITRL in humans is conserved with that in the mouse. Substitution of key interacting D93-I94-V95 (DIV) in mGITR with the corresponding K93-F94-S95 (KFS) in human GITR enables cross-recognition with human GITRL and cross-activation of receptor signaling. The findings of this study substantially expand our understanding of the interaction of TNFSF/TNFRSF superfamily molecules and can benefit the future design of biologics by targeting GITR/GITRL.

Multiple mechanisms for TRAF3-mediated regulation of the T cell costimulatory receptor GITR

Tumor necrosis factor receptor (TNFR)-associated factor 3 (TRAF3) plays context-specific roles in multiple receptor-mediated signaling pathways in different cell types. Mice lacking TRAF3 in T cells display defective T-cell-mediated immune responses to immunization and infection and demonstrate defective early signaling via the TCR complex. However, the role of TRAF3 in the function of GITR/TNFRSF18, an important costimulatory member of the TNFR superfamily, is unclear. Here we investigated the impact of T cell TRAF3 status on both GITR expression and activation of specific kinases in the GITR signaling pathway in T cells. Our results indicate that TRAF3 negatively regulates GITR functions in several ways. First, expression of GITR protein was elevated in TRAF3-deficient T cells, resulting from both transcriptional and posttranslational regulation that led to greater GITR transcript levels, as well as enhanced GITR protein stability. TRAF3 associated with T cell GITR in a manner dependent upon GITR ligation. TRAF3 also inhibited several events of the GITR mediated early signaling cascade, in a manner independent of recruitment of phosphatases, a mechanism by which TRAF3 inhibits signaling through several other cytokine receptors. These results add new information to our understanding of GITR signaling and function in T cells, which is relevant to the potential use of GITR to enhance immune therapies.

New emerging targets in cancer immunotherapy: the role of GITR

In the last decade, immunotherapies have revolutionised anticancer treatment. However, there is still a number of patients that do not respond or acquire resistance to these treatments. Despite several efforts to combine immunotherapy with other strategies like chemotherapy, or other immunotherapy, there is an 'urgent' need to better understand the immune landscape of the tumour microenvironment. New promising approaches, in addition to blocking co-inhibitory pathways, such those cytotoxic T-lymphocyte-associated protein 4 and programmed cell death protein 1 mediated, consist of activating co-stimulatory pathways to enhance antitumour immune responses. Among several new targets, glucocorticoid-induced TNFR-related gene (GITR) activation can promote effector T-cell function and inhibit regulatory T-cell (Treg) function. Preclinical data on GITR-agonist monoclonal antibodies (mAbs) demonstrated antitumour activity in vitro and in vivo enhancing CD8⁺ and CD4⁺ effector T-cell activity and depleting tumour-infiltrating Tregs. Phase I clinical trials reported a manageable safety profile of GITR mAbs. However, monotherapy seems not to be effective, whereas responses have been reported in combination therapy, in particular adding PD-1 blockade. Several clinical studies are ongoing and results are awaited to further develop GITR-stimulating treatments.

Merkel Cell Carcinoma from Molecular Pathology to Novel Therapies

Merkel cell carcinoma (MCC) is an uncommon and highly aggressive skin cancer. It develops mostly within chronically sun-exposed areas of the skin. MCPyV is detected in 60-80% of MCC cases as integrated within the genome and is considered a major risk factor for MCC. Viral negative MCCs have a high mutation burden with a UV damage signature. Aberrations occur in RB1, TP53, and NOTCH genes as well as in the PI3K-AKT-mTOR pathway. MCC is highly immunogenic, but MCC cells are known to evade the host's immune response. Despite the characteristic immunohistological profile of MCC, the diagnosis is challenging, and it should be confirmed by an experienced pathologist. Sentinel lymph node biopsy is considered the most reliable staging tool to identify subclinical nodal disease. Subclinical node metastases are present in about 30-50% of patients with primary MCC. The basis of MCC treatment is surgical excision. MCC is highly radiosensitive. It becomes chemoresistant within a few months. MCC is prone to recurrence. The outcomes in patients with metastatic disease are poor, with a historical 5-year survival of 13.5%. The median progression-free survival is 3-5 months, and the median overall survival is ten months. Currently, immunotherapy has become a standard of care first-line therapy for advanced MCC.

High-dimensional immunotyping of tumors grown in obese and non-obese mice

Obesity is a disease characterized by chronic low-grade systemic inflammation and has been causally linked to the development of 13 cancer types. Several studies have been undertaken to determine whether tumors evolving in obese environments adapt differential interactions with immune cells and whether this can be connected to disease outcome. Most of these studies have been limited to single-cell lines and tumor models and analysis of limited immune cell populations. Given the multicellular complexity of the immune system and its dysregulation in obesity, we applied high-dimensional suspension mass cytometry to investigate how obesity affects tumor immunity. We used a 36-marker immune-focused mass cytometry panel to interrogate the immune landscape of orthotopic syngeneic mouse models of pancreatic and breast cancer. Unanchored batch correction was implemented to enable simultaneous analysis of tumor cohorts to uncover the immunotypes of each cancer model and reveal remarkably model-specific immune regulation. In the E0771 breast cancer model, we demonstrate an important link to obesity with an increase in two T-cell-suppressive cell types and a decrease in CD8 T cells.

Structures of mouse and human GITR-GITRL complexes reveal unique TNF superfamily interactions

Glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) and GITR ligand (GITRL) are members of the tumor necrosis superfamily that play a role in immune cell signaling, activation, and survival. GITR is a therapeutic target for directly activating effector CD4 and CD8 T cells, or depleting GITR-expressing regulatory T cells (Tregs), thereby promoting anti-tumor immune responses. GITR activation through its native ligand is important for understanding immune signaling, but GITR structure has not been reported. Here we present structures of human and mouse GITR receptors bound to their cognate ligands. Both species share a receptor–ligand interface and receptor–receptor interface; the unique C-terminal receptor–receptor enables higher order structures on the membrane. Human GITR–GITRL has potential to form a hexameric network of membrane complexes, while murine GITR–GITRL complex forms a linear chain due to dimeric interactions. Mutations at the receptor–receptor interface in human GITR reduce cell signaling with in vitro ligand binding assays and minimize higher order membrane structures when bound by fluorescently labeled ligand in cell imaging experiments.

Glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) and GITR ligand (GITRL) regulate immune cell activities, including anti-tumor immune responses. Structures and visualization of human and mouse GITR–GITRL complexes offer insight into the architecture of higher-order membrane assemblies, and their signaling.

Lower Functional and Proportional Characteristics of Cord Blood Treg of Male Newborns Compared with Female Newborns

Understanding the early events involved in the induction of immune tolerance to harmless environmental antigens and microbiota compounds could reveal potential targets for allergic disease therapy or prevention. Regulatory T cells (Treg), particularly induced Treg (iTreg), are crucial for the induction and maintenance of tolerance against environmental antigens including allergens. A decrease in the number and/or function of Treg or iTreg could represent an early predictor of allergy development. We analyzed proportional and functional properties of Treg in the cord blood of children of allergic mothers (neonates at high risk of allergy development) and healthy mothers (neonates with relatively low risk of allergy development). We observed a higher number of induced Treg in the cord blood of females compared to males, suggesting an impaired capacity of male immunity to set up tolerance to allergens, which could contribute to the higher incidence of allergy observed in male infants. The decreased proportion of iTreg in cord blood compared with maternal peripheral blood documents the general immaturity of the neonatal immune system. We observed a positive correlation in the demethylation of the Treg-specific demethylated region (TSDR) and the proportion of Treg in cord blood. Our data suggest that immaturity of the neonatal immune system is more severe in males, predisposing them to increased risk of allergy development.

GITRL on dendritic cells aggravates house dust mite-induced airway inflammation and airway hyperresponsiveness by modulating CD4+ T cell differentiation

Background

Glucocorticoid-induced tumor necrosis factor receptor family-related protein ligand (GITRL) plays an important role in tumors, autoimmunity and inflammation. However, GITRL is not known to modulate the pathogenesis of allergic asthma. In this study, we investigated whether regulating GITRL expressed on dendritic cells (DCs) can prevent asthma and to elucidate its mechanism of action.

Methods

In vivo, the role of GITRL in modulating house dust mite (HDM)-induced asthma was assessed in adeno-associated virus (AAV)-shGITRL mice. In vitro, the role of GITRL expression by DCs was evaluated in LV-shGITRL bone marrow dendritic cells (BMDCs) under HDM stimulation. And the direct effect of GITRL was observed by stimulating splenocytes with GITRL protein. The effect of regulating GITRL on CD4⁺ T cell differentiation was detected. Further, GITRL mRNA in the peripheral blood of asthmatic children was tested.

Results

GITRL was significantly increased in HDM-challenged mice. In GITRL knockdown mice, allergen-induced airway inflammation, serum total IgE levels and airway hyperresponsiveness (AHR) were reduced. In vitro, GITRL expression on BMDCs was increased after HDM stimulation. Further, knocking down GITRL on DCs partially restored the balance of Th1/Th2 and Th17/Treg cells. Moreover, GITRL stimulation in vitro inhibited Treg cell differentiation and promoted Th2 and Th17 cell differentiation. Similarly, GITRL mRNA expression was increased in the peripheral blood from asthmatic children.

Conclusions

This study identified a novel role for GITRL expressed by DCs as a positive regulator of CD4⁺ T cells responses in asthma, which implicates that GITRL inhibitors may be a potential immunotherapy for asthma.

Immuno-comparative screening of adult-derived human liver stem/progenitor cells for immune-inflammatory-associated molecules

OBJECTIVE

One of the main challenges in liver cell therapy is the replacement of damaged cells and the induction of a tolerogenic microenvironment to promote graft acceptance by the recipient. Adult-derived human liver stem/progenitor cells (ADHLSCs) are currently evaluated at the clinical levels as a promising pro-regenerative and immune-modulatory tool. The expression profile of several immunological molecules may influence the local immune-inflammatory response and, therefore, modulate the tissue healing process. To increase the quality and safety of ADHLSCs before transplantation requires an appropriate analysis and characterization of their pattern expression of immune-inflammatory-associated molecules.

METHODS

The expression of 27 molecules belonging to T-cell co-stimulatory pathway, CD47 partners, Ikaros family, CD300 family and TNF family were analyzed using flow cytometry. We compared their expression profiles to PBMCs, hepatocytes and ADHLSCs in both expansion and after hepatogenic differentiation culture conditions.

RESULTS

This original immuno-comparative screening revealed that liver cell populations do not constitutively present significant immunological pattern compared to PBMCs. Moreover, our findings highlight that neither the expansion nor the hepatogenic differentiation induces the expression of immune-inflammatory molecules. The detailed expression characteristics (percentage of positive cells and median fluorescence intensity) of each molecule were analyzed and presented.

CONCLUSION

By analyzing 27 relevant molecules, our immuno-comparative screening demonstrates that ADHLSCs keep a non-immunogenic profile independent of their expansion or hepatogenic differentiation state. Accordingly, the immunological profile of ADHLSCs seems to support their safe and efficient use in liver tissue therapeutic repair strategy.

Tumor Necrosis Factor Superfamily: Ancestral Functions and Remodeling in Early Vertebrate Evolution

The evolution of the tumor necrosis factor superfamily (TNFSF) in early vertebrates is inferred by comparing the TNFSF genes found in humans and nine fishes: three agnathans, two chondrichthyans, three actinopterygians, and the sarcopterygian Latimeria chalumnae. By combining phylogenetic and synteny analyses, the TNFSF sequences detected are classified into five clusters of genes and 24 orthology groups. A model for their evolution since the origin of vertebrates is proposed. Fifteen TNFSF genes emerged from just three progenitors due to the whole-genome duplications (WGDs) that occurred before the agnathan/gnathostome split. Later, gnathostomes not only kept most of the genes emerged in the WGDs but soon added several tandem duplicates. More recently, complex, lineage-specific patterns of duplications and losses occurred in different gnathostome lineages. In agnathan species only seven to eight TNFSF genes are detected, because this lineage soon lost six of the genes emerged in the ancestral WGDs and additional losses in both hagfishes and lampreys later occurred. The orthologs of many of these lost genes are, in mammals, ligands of death-domain-containing TNFSF receptors, indicating that the extrinsic apoptotic pathway became simplified in the agnathan lineage. From the patterns of emergence of these genes, it is deduced that both the regulation of apoptosis and the control of the NF-κB pathway that depends in modern mammals on TNFSF members emerged before the ancestral vertebrate WGDs.

The Role of GITR/GITRL Interaction in Autoimmune Diseases

Glucocorticoid-induced TNFR-related protein (GITR) is a member of the TNFR superfamily which is expressed in various cells, including T cells, natural killer cells and some myeloid cells. GITR is activated by its ligand, GITRL, mainly expressed on antigen presenting cells and endothelial cells. It has been acknowledged that the engagement of GITR can modulate both innate and adaptive immune responses. Accumulated evidence suggests GITR/GITRL interaction is involved in the pathogenesis of tumor, inflammation and autoimmune diseases. In this review, we describe the effects of GITR/GITRL activation on effector T cells, regulatory T cells (Tregs) and myeloid cells; summarize its role and the underlying mechanisms in modulating autoimmune diseases.

Low-Dose LPS Induces Tolerogenic Treg Skewing in Asthma

The mechanism(s) underlying endotoxin tolerance in asthma remain elusive. As the endotoxin lipopolysaccharide (LPS) affects the expression of the regulatory T-cell (Treg)-suppressive glucocorticoid-induced tumor necrosis factor receptor ligand (GITRL) on antigen-presenting dendritic cells (DCs), we hypothesized that LPS-induced changes in DC GITRL expression may impact Treg-mediated T-helper (Th) cell suppression and the induction of endotoxin tolerance. Here, we propose a novel mechanism by which low-dose LPS inhalation in neonatal mice induces endotoxin tolerance, thereby offering protection from later asthma development. Three-day old wild-type and Toll-like receptor 4 (TLR4)-deficient neonatal mice were exposed to low-dose LPS (1 μg) intranasally for 10 consecutive days prior to ovalbumin (OVA)-induced asthma to better understand the tolerogenic mechanism(s) of low-dose LPS pre-exposure. In vivo findings were validated using in vitro co-culturing studies of primary CD11c⁺ DCs and CD4⁺ T-cells with or without low-dose LPS pre-exposure before OVA stimulation. Low-dose LPS pre-exposure upregulated the Treg response and downregulated pathogenic Th2 and Th17 responses through promoting apoptosis of Th2 and Th17 cells. Low-dose LPS pre-exposure downregulated DC GITRL expression and T-cell GITR expression. Artificial DC GITRL expression abrogated the tolerogenic Treg-skewing effect of low-dose LPS pre-exposure. Low-dose LPS pre-exposure inhibited TRIF/IRF3/IFNβ signaling and upregulated expression of tolerogenic TRIF/IRF3/IFNβ negative regulators in a TLR4-dependent manner. This tolerogenic DC GITRL downregulation was attributable to TRIF/IRF3/IFNβ signaling inhibition. Low-dose LPS pre-exposure produces tolerogenic Treg skewing in neonatal asthmatic mice, a phenomenon attributable to TLR4-dependent TRIF/IRF3/IFNβ-mediated DC GITRL downregulation.

GITR controls intestinal inflammation by suppressing IL-15-dependent NK cell activity

Glucocorticoid-induced TNFR family related gene (GITR) is a member of the TNFR superfamily that is expressed on cells of the immune system. Although the protective and pathogenic roles of GITR in T cell immunity are well characterized, the role of GITR in innate immunity in the intestinal tissues has not been well clarified. In this study, using a dextran sulfate sodium (DSS)-induced colitis model in mice, we found that GITR-deficiency rendered mice more susceptible to acute intestinal inflammation and that a significantly higher number of activated natural killer (NK) cells was accumulated in the colonic lamina propria of Gitr^-/- mice as compared to wild-type mice. Additionally, Rag2^-/- Gitr^-/- mice, which lack T cells but have NK cells, also displayed more severe colonic inflammation than Rag2^-/- mice. In contrast, an anti-GITR agonistic antibody significantly alleviated colitis in Rag2^-/- mice. Engagement of GITR inhibited IL-15-mediated activating signaling events in NK cells, which include cell activation and proliferation, and production of cytokines and cytotoxic granules. Taken together, our results provide the first evidence that GITR negatively controls intestinal inflammation through NK cell functions.

Impact of Immunometabolism on Cancer Metastasis: A Focus on T Cells and Macrophages

Despite improved treatment options, cancer remains the leading cause of morbidity and mortality worldwide, with 90% of this mortality correlated to the development of metastasis. Since metastasis has such an impact on treatment success, disease outcome, and global health, it is important to understand the different steps and factors playing key roles in this process, how these factors relate to immune cell function and how we can target metabolic processes at different steps of metastasis in order to improve cancer treatment and patient prognosis. Recent insights in immunometabolism direct to promising therapeutic targets for cancer treatment, however, the specific contribution of metabolism on antitumor immunity in different metastatic niches warrant further investigation. Here, we provide an overview of what is so far known in the field of immunometabolism at different steps of the metastatic cascade, and what may represent the next steps forward. Focusing on metabolic checkpoints in order to translate these findings from in vitro and mouse studies to the clinic has the potential to revolutionize cancer immunotherapy and greatly improve patient prognosis.

New immunotherapeutic drugs in advanced non-small cell lung cancer (NSCLC): from preclinical to phase I clinical trials

INTRODUCTION

The development of immune checkpoint inhibitors (ICI) has represented a revolution in the treatment of non-small cell lung cancer (NSCLC) and has established a new standard of care for different settings. However, through adaptive changes, cancer cells can develop resistance mechanisms to these drugs, hence the necessity for novel immunotherapeutic agents.

AREAS COVERED

This paper explores the immunotherapeutics currently under investigation in phase I clinical trials for the treatment of NSCLC as monotherapies and combination therapies. It provides two comprehensive tables of phase I agents which are listed according to target, drug, drug class, mechanism of action, setting, trial identifier, and trial status. A comprehensive literature search was carried out to identify eligible studies from MEDLINE/PubMed and ClinicalTrials.gov.

EXPERT OPINION

A key hurdle to success in this field is our limited understanding of the synergic interactions of the immune targets in the context of the TME. While we can recognize the links between inhibitors and some particularly promising new targets such as TIM-3 and LAG3, we continue to develop approaches to exploit their interactions to enhance the immune response of the patient to tumor cells.

Discovery and Function of B-Cell IgD Low (BDL) B Cells in Immune Tolerance

It is now appreciated that in addition to their role in humoral immunity, B cells also exert regulatory mechanisms that lead to attenuation of inflammatory responses. The concept of B-cell regulation became well recognized when mice deficient in B cells due to genetic disruption were shown to be refractory to recovery from the signs of experimental autoimmune encephalomyelitis (EAE), the mouse model of multiple sclerosis. This seminal study spurred the search for B-cell regulatory phenotypes and mechanisms of action. Our approach was to utilize differential B-cell depletion with anti-CD20 to retain B cells whose presence were required to achieve EAE recovery. Utilizing flow cytometry, adoptive cell therapy and genetic approaches, we discovered a new B-cell subset that, upon adoptive transfer into B cell-deficient mice, was sufficient to promote EAE recovery. This B-cell subset is IgM⁺, but due to low/negative IgD cell surface expression, it was named B-cell IgD low (BD_L). Mechanistically, we found that in the absence of BD_L, the absolute cell number of CD4⁺Foxp3⁺ T regulatory cells (Treg), essential for immune tolerance, was significantly reduced. Furthermore, we found that BD_L expression of glucocorticoid-induced tumor necrosis factor ligand (GITRL) was essential for induction of Treg proliferation and maintenance of their homeostasis. Thus, we have identified a new B-cell subset that is critical for immunological tolerance through interactions with Treg.

GITR Agonism Triggers Antitumor Immune Responses through IL21-Expressing Follicular Helper T Cells

Although treatment with the glucocorticoid-induced tumor necrosis factor receptor-related protein (GITR) agonistic antibody (DTA-1) has shown antitumor activity in various tumor models, the underlying mechanism is not fully understood. Here, we demonstrate that interleukin (IL)-21-producing follicular helper T (Tfh) cells play a crucial role in DTA-1-induced tumor inhibition. The administration of DTA-1 increased IL21 expression by Tfh cells in an antigen-specific manner, and this activation led to enhanced antitumor cytotoxic T lymphocyte (CTL) activity. Mice treated with an antibody that neutralizes the IL21 receptor exhibited decreased antitumor activity when treated with DTA-1. Tumor growth inhibition by DTA-1 was abrogated in Bcl6 ^fl/fl Cd4 ^Cre mice, which are genetically deficient in Tfh cells. IL4 was required for optimal induction of IL21-expressing Tfh cells by GITR costimulation, and c-Maf mediated this pathway. Thus, our findings identify GITR costimulation as an inducer of IL21-expressing Tfh cells and provide a mechanism for the antitumor activity of GITR agonism.

Co-Stimulatory Receptors in Cancers and Their Implications for Cancer Immunotherapy

Immune checkpoint inhibitors (ICIs), including anti-PD-1 and anti-CTLA-4 therapeutic agents, are now approved by the Food and Drug Administration for treatment of various types of cancer. However, the therapeutic efficacy of ICIs varies among patients and cancer types. Moreover, most patients do not develop durable antitumor responses after ICI therapy due to an ephemeral reversal of T-cell dysfunction. As co-stimulatory receptors play key roles in regulating the effector functions of T cells, activating co-stimulatory pathways may improve checkpoint inhibition efficacy, and lead to durable antitumor responses. Here, we review recent advances in our understating of co-stimulatory receptors in cancers, providing the necessary groundwork for the rational design of cancer immunotherapy.

Overview of Basic Immunology and Clinical Application

Tumor exists as a complex network of structures with an ability to evolve and evade the host immune surveillance mechanism. The immune milieu which includes macrophages, dendritic cells, natural killer cells, neutrophils, mast cells, B cells, and T cells are found in the core, the invasive margin, or the adjacent stromal or lymphoid component of the tumor. The immune infiltrate is heterogeneous and varies within a patient and between patients of the same tumor histology. The location, density, functionality, and cross-talk between the immune cells in the tumor microenvironment influence the nature of immune response, prognosis, and treatment outcomes in cancer patients. Therefore, an understanding of the characteristics of the immune cells and their role in tumor immune surveillance is of paramount importance to identify immune targets and to develop novel immune therapeutics in the war against cancer. In this chapter, we provide an overview of the individual components of the human immune system and the translational relevance of predictive biomarkers.

Invariant NKT Cell-Mediated Modulation of ILC1s as a Tool for Mucosal Immune Intervention

Non-NK group 1 innate lymphoid cells (ILC1s), mainly investigated in the mucosal areas of the intestine, are well-known to contribute to anti-parasitic and anti-bacterial immune responses. Recently, our group revealed that lung ILC1s become activated during murine influenza infection, thereby contributing to viral clearance. In this context, worldwide seasonal influenza infections often result in severe disease outbreaks leading to high morbidity and mortality. Therefore, new immune interventions are urgently needed. In contrast to NK cells, the potential of non-NK ILC1s to become functionally tailored by immune modulators to contribute to the combat against mucosal-transmitted viral pathogens has not yet been addressed. The present study aimed at assessing the potential of ILC1s to become modulated by iNKT cells activated through the CD1d agonist αGalCerMPEG. Our results demonstrate an improved functional responsiveness of murine lung and splenic ILC1s following iNKT cell stimulation by the mucosal route, as demonstrated by enhanced surface expression of TNF-related apoptosis-inducing ligand (TRAIL), CD49a and CD28, and increased secretion of IFNγ. Interestingly, iNKT cell stimulation also induced the expression of the immune checkpoint molecules GITR and CTLA-4, which represent crucial points of action for immune regulation. An in vivo influenza infection model revealed that intranasal activation of ILC1s by αGalCerMPEG contributed to increased viral clearance as shown by reduced viral loads in the lungs. The findings that ILC1s can become modulated by mucosally activated iNKT cells in a beneficial manner emphasize their up to now underestimated potential and renders them to be considered as targets for novel immune interventions.

Soluble glucocorticoid-induced tumor necrosis factor receptor regulates Helios expression in myasthenia gravis

BACKGROUND

Helios is important for functional and phenotype stability of regulatory T cells (Tregs). However, the role of Helios in autoimmune diseases and its regulation remains unclear. This study aimed to investigate the role of Helios⁺ Tregs in myasthenia gravis (MG) and glucocorticoid-induced tumor necrosis factor receptor (GITR) and its ligand (GITRL) in the modulation of Helios.

METHOD

Multicolor flow cytometry was performed to analyze Helios⁺ Tregs in peripheral blood from MG patients and healthy donors (HDs). Enzyme-linked immunosorbent assay (ELISA) was used to determine the levels of soluble GITRL/GITR in plasma. Tregs were isolated via magnetic separation and treated with recombinant GITRL and GITR-Fc. Membrane GITRL on Tregs and expression of Helios and other markers (FOXP3, CD25, CD39, CTLA-4, PD-L1 and IL-10) involved in immunosuppressive activity were determined by flow cytometry.

RESULT

Both Helios⁺ Tregs and soluble GITR were decreased in generalized MG (GMG) patients (n = 14), compared with HDs (n = 14) and ocular MG (OMG) patients (n = 16). Helios⁺ Tregs possessed greater immunosuppressive capacity compared to Helios^- Tregs. Further analysis indicates soluble GITR was negatively correlated with quantitative MG score and promoted Helios expression and enhanced function of Tregs independently of membrane GITRL.

CONCLUSION

This work demonstrates abnormal changes in Helios⁺ Tregs and soluble GITR in MG, as well as direct regulation of Helios by GITR in the context of Tregs. This work provides new insight into the role of GITR in the regulatory pathway of Helios and pathogenesis of MG.

GITRL on inflammatory antigen presenting cells in the lung parenchyma provides signal 4 for T-cell accumulation and tissue-resident memory T-cell formation

T-cell responses in the lung are critical for protection against respiratory pathogens. TNFR superfamily members play important roles in providing survival signals to T cells during respiratory infections. However, whether these signals take place mainly during priming in the secondary lymphoid organs and/or in the peripheral tissues remains unknown. Here we show that under conditions of competition, GITR provides a T-cell intrinsic advantage to both CD4 and CD8 effector T cells in the lung tissue, as well as for the formation of CD4 and CD8 tissue-resident memory T cells during respiratory influenza infection in mice. In contrast, under non-competitive conditions, GITR has a preferential effect on CD8 over CD4 T cells. The nucleoprotein-specific CD8 T-cell response partially compensated for GITR deficiency by expansion of higher affinity T cells; whereas, the polymerase-specific response was less flexible and more GITR dependent. Following influenza infection, GITR is expressed on lung T cells and GITRL is preferentially expressed on lung monocyte-derived inflammatory antigen presenting cells. Accordingly, we show that GITR+/+ T cells in the lung parenchyma express more phosphorylated-ribosomal protein S6 than their GITR-/- counterparts. Thus, GITR signaling within the lung tissue critically regulates effector and tissue-resident memory T-cell accumulation.

Reverse Signaling of Tumor Necrosis Factor Superfamily Proteins in Macrophages and Microglia: Superfamily Portrait in the Neuroimmune Interface

The tumor necrosis factor (TNF) superfamily (TNFSF) is a protein superfamily of type II transmembrane proteins commonly containing the TNF homology domain. The superfamily contains more than 20 protein members, which can be released from the cell membrane by proteolytic cleavage. Members of the TNFSF function as cytokines and regulate diverse biological processes, including immune responses, proliferation, differentiation, apoptosis, and embryogenesis, by binding to TNFSF receptors. Many TNFSF proteins are also known to be responsible for the regulation of innate immunity and inflammation. Both receptor-mediated forward signaling and ligand-mediated reverse signaling play important roles in these processes. In this review, we discuss the functional expression and roles of various reverse signaling molecules and pathways of TNFSF members in macrophages and microglia in the central nervous system (CNS). A thorough understanding of the roles of TNFSF ligands and receptors in the activation of macrophages and microglia may improve the treatment of inflammatory diseases in the brain and periphery. In particular, TNFSF reverse signaling in microglia can be exploited to gain further insights into the functions of the neuroimmune interface in physiological and pathological processes in the CNS.

Costimulation of type-2 innate lymphoid cells by GITR promotes effector function and ameliorates type 2 diabetes

Metabolic syndrome is characterized by disturbances in glucose homeostasis and the development of low-grade systemic inflammation, which increase the risk to develop type 2 diabetes mellitus (T2DM). Type-2 innate lymphoid cells (ILC2s) are a recently discovered immune population secreting Th2 cytokines. While previous studies show how ILC2s can play a critical role in the regulation of metabolic homeostasis in the adipose tissue, a therapeutic target capable of modulating ILC2 activation has yet to be identified. Here, we show that GITR, a member of the TNF superfamily, is expressed on both murine and human ILC2s. Strikingly, we demonstrate that GITR engagement of activated, but not naïve, ILC2s improves glucose homeostasis, resulting in both protection against insulin resistance onset and amelioration of established insulin- resistance. Together, these results highlight the critical role of GITR as a novel therapeutic molecule against T2DM and its fundamental role as an immune checkpoint for activated ILC2s.

Type-2 innate lymphoid cells (ILC2s) are an immune population secreting Th2 cytokines playing a role in the regulation of adipose metabolic homeostasis. Here the authors show that engagement of GITR, a member of the TNF superfamily, in activated ILC2s is protective against insulin resistance in both a preventive and a therapeutic manner in the context of obesity.

Antigen delivery targeted to tumor-associated macrophages overcomes tumor immune resistance

Immune checkpoint inhibitors and adoptive transfer of gene-engineered T cells have emerged as novel therapeutic modalities for hard-to-treat solid tumors; however, many patients are refractory to these immunotherapies, and the mechanisms underlying tumor immune resistance have not been fully elucidated. By comparing the tumor microenvironment of checkpoint inhibition-sensitive and -resistant murine solid tumors, we observed that the resistant tumors had low immunogenicity. We identified antigen presentation by CD11b+F4/80+ tumor-associated macrophages (TAMs) as a key factor correlated with immune resistance. In the resistant tumors, TAMs remained inactive and did not exert antigen-presenting activity. Targeted delivery of a long peptide antigen to TAMs by using a nano-sized hydrogel (nanogel) in the presence of a TLR agonist activated TAMs, induced their antigen-presenting activity, and thereby transformed the resistant tumors into tumors sensitive to adaptive immune responses such as adoptive transfer of tumor-specific T cell receptor-engineered T cells. These results indicate that the status and function of TAMs have a significant impact on tumor immune sensitivity and that manipulation of TAM functions would be an effective approach for improving the efficacy of immunotherapies.

Immune checkpoint blockade and its combination therapy with small-molecule inhibitors for cancer treatment

Initially understood for its physiological maintenance of self-tolerance, the immune checkpoint molecule has recently been recognized as a promising anti-cancer target. There has been considerable interest in the biology and the action mechanism of the immune checkpoint therapy, and their incorporation with other therapeutic regimens. Recently the small-molecule inhibitor (SMI) has been identified as an attractive combination partner for immune checkpoint inhibitors (ICIs) and is becoming a novel direction for the field of combination drug design. In this review, we provide a systematic discussion of the biology and function of major immune checkpoint molecules, and their interactions with corresponding targeting agents. With both preclinical studies and clinical trials, we especially highlight the ICI + SMI combination, with its recent advances as well as its application challenges.

Distinct characteristics of Tregs of newborns of healthy and allergic mothers

Allergic diseases represent a major issue in clinical and experimental immunology due to their high and increasing incidence worldwide. Allergy status of the mother remains the best predictor of an individual's increased risk of allergy development. Dysregulation of the balance between different branches of immune response, chiefly excessive polarization towards Th2, is the underlying cause of allergic diseases. Regulatory T cells (Tregs) play a pivotal role in the timely establishment of physiological immune polarization and are crucial for control of allergy. In our study we used flow cytometry to assess Tregs in cord blood of newborns of healthy (n = 121) and allergic (n = 108) mothers. We observed a higher percentage of Tregs (CD4+CD25+CD127lowFoxP3+) in cord blood of children of allergic mothers. However, the percentage of cells expressing extracellular (PD-1, CTLA-4, GITR) and intracellular (IL-10, TGF-β) markers of function was lower (significantly for PD-1 and IL-10) within Tregs of these children. Furthermore, Helios- induced Tregs in the cord blood of children of allergic mothers were decreased. These results were supported by a decrease in plasma levels of IL-10 and TGF-β in cord blood of newborns of allergic mothers, implying lower tolerogenic capacity on the systemic level. Taken together, these findings reflect deficient function of Tregs in the group with higher risk of allergy development. This may be caused by a lower maturation status of the immune system, specifically Tregs, at birth. Such immaturity may represent an important mechanism involved in the increased risk of allergy in children of allergic mothers.