Regulated compartmentalization of programmed cell death-1 discriminates CD4+CD25+ resting regulatory T cells from activated T cells

Beyond FOXP3: a 20-year journey unravelling human regulatory T-cell heterogeneity

The initial idea of a distinct group of T-cells responsible for suppressing immune responses was first postulated half a century ago. However, it is only in the last three decades that we have identified what we now term regulatory T-cells (Tregs), and subsequently elucidated and crystallized our understanding of them. Human Tregs have emerged as essential to immune tolerance and the prevention of autoimmune diseases and are typically contemporaneously characterized by their CD3+CD4+CD25high CD127lowFOXP3+ phenotype. It is important to note that FOXP3+ Tregs exhibit substantial diversity in their origin, phenotypic characteristics, and function. Identifying reliable markers is crucial to the accurate identification, quantification, and assessment of Tregs in health and disease, as well as the enrichment and expansion of viable cells for adoptive cell therapy. In our comprehensive review, we address the contributions of various markers identified in the last two decades since the master transcriptional factor FOXP3 was identified in establishing and enriching purity, lineage stability, tissue homing and suppressive proficiency in CD4+ Tregs. Additionally, our review delves into recent breakthroughs in innovative Treg-based therapies, underscoring the significance of distinct markers in their therapeutic utilization. Understanding Treg subsets holds the key to effectively harnessing human Tregs for immunotherapeutic approaches.

Five Inhibitory Receptors Display Distinct Vesicular Distributions in Murine T Cells

T cells can express multiple inhibitory receptors. Upon induction of T cell exhaustion in response to a persistent antigen, prominently in the anti-tumor immune response, many are expressed simultaneously. Key inhibitory receptors are CTLA-4, PD-1, LAG3, TIM3, and TIGIT, as investigated here. These receptors are important as central therapeutic targets in cancer immunotherapy. Inhibitory receptors are not constitutively expressed on the cell surface, but substantial fractions reside in intracellular vesicular structures. It remains unresolved to which extent the subcellular localization of different inhibitory receptors is distinct. Using quantitative imaging of subcellular distributions and plasma membrane insertion as complemented by proximity proteomics and biochemical analysis of the association of the inhibitory receptors with trafficking adaptors, the subcellular distributions of the five inhibitory receptors were discrete. The distribution of CTLA-4 was most distinct, with preferential association with lysosomal-derived vesicles and the sorting nexin 1/2/5/6 transport machinery. With a lack of evidence for the existence of specific vesicle subtypes to explain divergent inhibitory receptor distributions, we suggest that such distributions are driven by divergent trafficking through an overlapping joint set of vesicular structures. This extensive characterization of the subcellular localization of five inhibitory receptors in relation to each other lays the foundation for the molecular investigation of their trafficking and its therapeutic exploitation.

Implications of Rectal Cancer Radiotherapy on the Immune Microenvironment: Allies and Foes to Therapy Resistance and Patients' Outcome

Aside from surgical resection, locally advanced rectal cancer is regularly treated with neoadjuvant chemoradiotherapy. Since the concept of cancer treatment has shifted from only focusing on tumor cells as drivers of disease progression towards a broader understanding including the dynamic tumor microenvironment (TME), the impact of radiotherapy on the TME and specifically the tumor immune microenvironment (TIME) is increasingly recognized. Both promoting as well as suppressing effects on anti-tumor immunity have been reported in response to rectal cancer (chemo-)radiotherapy and various targets for combination therapies are under investigation. A literature review was conducted searching the PubMed database for evidence regarding the pleiotropic effects of (chemo-)radiotherapy on the rectal cancer TIME, including alterations in cytokine levels, immune cell populations and activity as well as changes in immune checkpoint proteins. Radiotherapy can induce immune-stimulating and -suppressive alterations, potentially mediating radioresistance. The response is influenced by treatment modalities, including the dosage administered and the highly individual intrinsic pre-treatment immune status. Directly addressing the main immune cells of the TME, this review aims to highlight therapeutical implications since efficient rectal cancer treatment relies on personalized strategies combining conventional therapies with immune-modulating approaches, such as immune checkpoint inhibitors.

Five inhibitory receptors display distinct vesicular distributions in T cells

T cells can express multiple inhibitory receptors. Upon induction of T cell exhaustion in response to persistent antigen, prominently in the anti-tumor immune response, many are expressed simultaneously. Key inhibitory receptors are CTLA-4, PD-1, LAG3, TIM3 and TIGIT, as investigated here. These receptors are important as central therapeutic targets in cancer immunotherapy. Inhibitory receptors are not constitutively expressed on the cell surface, but substantial fractions reside in intracellular vesicular structures. It remains unresolved to which extent the subcellular localization of different inhibitory receptors is distinct. Using quantitative imaging of subcellular distributions and plasma membrane insertion as complemented by proximity proteomics and a biochemical analysis of the association of the inhibitory receptors with trafficking adaptors, the subcellular distributions of the five inhibitory receptors were discrete. The distribution of CTLA-4 was most distinct with preferential association with lysosomal-derived vesicles and the sorting nexin 1/2/5/6 transport machinery. With a lack of evidence for the existence of specific vesicle subtypes to explain divergent inhibitory receptor distributions, we suggest that such distributions are driven by divergent trafficking through an overlapping joint set of vesicular structures. This extensive characterization of the subcellular localization of five inhibitory receptors in relation to each other lays the foundation for the molecular investigation of their trafficking and its therapeutic exploitation.

PD-1/PD-L1 axis in organ fibrosis

Fibrosis is a pathological tissue repair activity in which many myofibroblasts are activated and extracellular matrix are excessively accumulated, leading to the formation of permanent scars and finally organ failure. A variety of organs, including the lung, liver, kidney, heart, and skin, can undergo fibrosis under the stimulation of various exogenous or endogenous pathogenic factors. At present, the pathogenesis of fibrosis is still not fully elucidated, but it is known that the immune system plays a key role in the initiation and progression of fibrosis. Immune checkpoint molecules are key regulators to maintain immune tolerance and homeostasis, among which the programmed cell death protein 1/programmed death ligand 1 (PD-1/PD-L1) axis has attracted much attention. The exciting achievements of tumor immunotherapy targeting PD-1/PD-L1 provide new insights into its use as a therapeutic target for other diseases. In recent years, the role of PD-1/PD-L1 axis in fibrosis has been preliminarily explored, further confirming the close relationship among PD-1/PD-L1 signaling, immune regulation, and fibrosis. This review discusses the structure, expression, function, and regulatory mechanism of PD-1 and PD-L1, and summarizes the research progress of PD-1/PD-L1 signaling in fibrotic diseases.

T cell co-stimulatory and co-inhibitory pathways in atopic dermatitis

The use of immune checkpoint inhibitors (ICIs) targeting the T cell inhibitory pathways has revolutionized cancer treatment. However, ICIs might induce progressive atopic dermatitis (AD) by affecting T cell reactivation. The critical role of T cells in AD pathogenesis is widely known. T cell co-signaling pathways regulate T cell activation, where co-signaling molecules are essential for determining the magnitude of the T cell response to antigens. Given the increasing use of ICIs in cancer treatment, a timely overview of the role of T cell co-signaling molecules in AD is required. In this review, we emphasize the importance of these molecules involved in AD pathogenesis. We also discuss the potential of targeting T cell co-signaling pathways to treat AD and present the unresolved issues and existing limitations. A better understanding of the T cell co-signaling pathways would aid investigation of the mechanism, prognosis evaluation, and treatment of AD.

Antibody-based cancer immunotherapy by targeting regulatory T cells

Regulatory T cells (Tregs) are among the most abundant suppressive cells, which infiltrate and accumulate in the tumor microenvironment, leading to tumor escape by inducing anergy and immunosuppression. Their presence has been correlated with tumor progression, invasiveness and metastasis. Targeting tumor-associated Tregs is an effective addition to current immunotherapy approaches, but it may also trigger autoimmune diseases. The major limitation of current therapies targeting Tregs in the tumor microenvironment is the lack of selective targets. Tumor-infiltrating Tregs express high levels of cell surface molecules associated with T-cell activation, such as CTLA4, PD-1, LAG3, TIGIT, ICOS, and TNF receptor superfamily members including 4-1BB, OX40, and GITR. Targeting these molecules often attribute to concurrent depletion of antitumor effector T-cell populations. Therefore, novel approaches need to improve the specificity of targeting Tregs in the tumor microenvironment without affecting peripheral Tregs and effector T cells. In this review, we discuss the immunosuppressive mechanisms of tumor-infiltrating Tregs and the status of antibody-based immunotherapies targeting Tregs.

Histone deacetylase 6 plays an important role in TGF-β-induced murine Treg cell differentiation by regulating cell proliferation

Regulatory T (Treg) cells maintain immune homeostasis by preventing abnormal or excessive immune responses. Histone deacetylase 6 (HDAC6) regulates expression of Foxp3, and thus, Treg cell differentiation; however, its role in Treg cell differentiation is unclear and somewhat controversial. Here, we investigated the role of HDAC6 in TGF-β-induced murine Treg cells. HDAC6 expression was higher in Treg cells than in other T helper cell subsets. Pharmacological inhibitors of HDAC6 selectively inhibited Treg cell differentiation and suppressive function. A specific HDAC6 inhibitor induced changes in global gene expression by Treg cells. Of these changes, genes related to cell division were prominently affected. In summary, HDAC6 plays an important role in TGF-β-induced murine Treg cell differentiation by regulating cell proliferation.

Exploring genetic and immune underpinnings of the sexual dimorphism in tumor response to immune checkpoints inhibitors: A narrative review

Introduction

In spite of the undisputed relevance of sex as critical biologic variable of the immune landscape, still limited is our understanding of the basic mechanisms implicated in sex-biased immune response thereby conditioning the therapeutic outcome in cancer patients. This hindrance delays the actual attempts to decipher the heterogeneity of cancer and its immune surveillance, further digressing the achievement of predictive biomarkers in the current immunotherapy-driven scenario. Body: The present review concisely reports on genetic, chromosomal, hormonal, and immune features underlying sex-differences in the response to immune checkpoint inhibitors (ICIs). In addition to outline the need of robust data on ICI pharmaco-kinetics/dynamics, our survey might provide new insights on sex determinants of ICI efficacy and suggests uncovered pathways that warrant prospective investigations.

Conclusion

According to a sharable view, we propose to widely include sex among the co-variates when assessing the clinical response to ICI in cancer patients.

Abnormal Epigenetic Regulations in the Immunocytes of Sjögren’s Syndrome Patients and Therapeutic Potentials

Sjögren’s syndrome (SjS), characterized by keratoconjunctivitis sicca and dry mouth, is a common autoimmune disease, especially in middle-aged women. The immunopathogenesis of SjS is caused by the sequential infiltration of T and B cells into exocrine glands, including salivary and lacrimal glands. Effector cytokines produced by these immunocytes, such as interferons (IFNs), IL-17, IL-22, IL-21, IL-4, TNF-α, BAFF and APRIL, play critical roles in promoting autoimmune responses and inducing tissue damages. Epigenetic regulations, including DNA methylation, histone modification and non-coding RNAs, have recently been comprehensively studied during the activation of various immunocytes. The deficiency of key epigenetic enzymes usually leads to aberrant immune activation. Epigenetic modifications in T and B cells are usually found to be altered during the immunopathogenesis of SjS, and they are closely correlated with autoimmune responses. In particular, the important role of methylation in activating IFN pathways during SjS progression has been revealed. Thus, according to the involvement of epigenetic regulations in SjS, target therapies to reverse the altered epigenetic modifications in auto-responsive T and B cells are worthy of being considered as a potential therapeutic strategy for SjS.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

PD-L1 is expressed on human activated naive effector CD4+ T cells. Regulation by dendritic cells and regulatory CD4+ T cells

The T cell expression of various co-signalling receptors from the CD28 immunoglobulin superfamily (Inducible T cell co-stimulator (ICOS), Programmed cell death 1(PD-1), cytotoxic T lymphocyte associated protein 4 (CTLA-4), B and T lymphocyte attenuator (BTLA) or from the tumour necrosis factor receptor superfamily (glucocorticoid-induced TNFR family related (GITR), 4-1BB, and CD27), is essential for T cell responses regulation. Other receptors (such as T cell immunoglobulin and mucin domain-containing protein 3, T cell immunoglobulin and T cell immunoglobulin and ITIM domain (TIGIT), and lymphocyte activation gene 3) are also involved in this regulation. Disturbance of the balance between activating and inhibitory signals can induce autoimmunity. We have developed an in vitro assay to simultaneously assess the function of naive CD4⁺ effector T cells (TEFFs), dendritic cells (DCs) and regulatory T cells (TREGs) and the expression of co-signalling receptors. By running the assay on cells from healthy adult, we investigated the regulation of activated T cell proliferation and phenotypes. We observed that TEFFs activated by DCs mainly expressed BTLA, ICOS and PD-1, whereas activated TREGs mainly expressed TIGIT, ICOS, and CD27. Strikingly, we observed that programmed death-ligand 1 (PD-L1) was significantly expressed on both activated TEFFs and TREGs. Moreover, high PD-L1 expression on activated TEFFs was correlated with a higher index of proliferation. Lastly, and in parallel to the TREG-mediated suppression of TEFF proliferation, we observed the specific modulation of the surface expression of PD-L1 (but not other markers) on activated TEFFs. Our results suggest that the regulation of T cell proliferation is correlated with the specific expression of PD-L1 on activated TEFFs.

Immunobiology of T Cells in Sjögren's Syndrome

Sjögren's syndrome (SjS) is a systemic autoimmune disease marked by xerostomia (dry mouth), keratoconjunctivitis sicca (eye dryness), and other systematic disorders. Its pathogenesis involves an inflammatory process that is characterized by lymphocytic infiltration into exocrine glands and other tissues. Although the development of ectopic lymphoid tissue and overproduction of autoantibodies by hyperactive B cells suggest that they may promote SjS development, treatment directed towards them fails to induce significant laboratory or clinical improvement. T cells are overwhelming infiltrators in most phases of the disease, and the involvement of multiple T cell subsets of suggests the extraordinary complexity of SjS pathogenesis. The factors, including various cellular subtypes and molecules, regulate the activation and suppression of T cells. T cell activation induces inflammatory cell infiltration, B cell activation, tissue damage, and metabolic changes in SjS. Knowledge of the pathways that link these T cell subtypes and regulation of their activities are not completely understood. This review comprehensively summarizes the research progress and our understanding of T cells in SjS, including CD4⁺ T cells, CD8⁺ T_RM cells, and innate T cells, to provide insights into for clinical treatment.

Prospective Evaluation of Radiotherapy-Induced Immunologic and Genetic Effects in Colorectal Cancer Oligo-Metastatic Patients with Lung-Limited Disease: The PRELUDE-1 Study

Simple Summary

The management of advanced colorectal cancer (CRC) has been greatly improved with integrated strategies including stereotactic radiation therapy (SRT). It is a safe and effective option, particularly in oligo-metastatic (om) CRC patients. Interestingly, it has been demonstrated that SRT can induce regression of tumors in non-irradiated regions (“abscopal effect”) through stimulation of anti-tumor immune effects (“radiation-induced immunity”). We have recently shown that lung-limited omCRC is characterized by regression of tumor clones bearing specific key driver gene mutations. The aim of the PRELUDE-1 study is to assess the genetic and immunologic evolutions on tumor cancer/host cells induced by SRT in lung-limited omCRC through liquid biopsies and Next Generation Sequencing of tumor exome, HLA repertoire assessment, peripheral immune cells, and cytokine dynamics characterizations. An important secondary objective is the first prospective evaluation of the abscopal effect. The PRELUDE-1 results will help to identify subsets of patients more prone to show the abscopal effect. The PRELUDE-1 trial was registered into the clinicaltrials.gov registry on 22 April 2021, with identifier NCT04854213.

Abstract

Background: in recent years, the management of advanced colorectal cancer (CRC) has been greatly improved with integrated strategies including stereotactic radiation therapy (SRT). The administration of SRT has been demonstrated, particularly in oligo-metastatic (om) CRC, to be a safe and effective option. Interestingly, it has been demonstrated that SRT can induce regression of tumors in non-irradiated regions (“abscopal effect”) through stimulation of anti-tumor immune effects (“radiation-induced immunity”). We have recently shown that lung-limited omCRC is characterized by regression of tumor clones bearing specific key driver gene mutations. Aims: to assess the genetic evolution on tumor cancer cells induced by SRT in lung-limited omCRC. Secondary objectives included descriptions of the abscopal effect, responses’ duration, toxicity, and progression-free survival. A translational research will be performed to evaluate tumor genetic evolution (through liquid biopsies and Next Generation Sequencing), HLA class I repertoire, peripheral immune cells, and cytokine dynamics. Methods: PRELUDE-1 is a prospective translational study. SRT will be administered only to the largest nodule (with a maximum diameter ≤ 25 mm) in omCRC with two or three radiologically evident lesions. The sample size is based on the innovative hypothesis that radiation-induced immunity could induce regression of tumor clones bearing KRAS oncogene mutations. According to the binomial test, considering the frequency of KRAS mutations and assuming a probability of mutant KRAS→wild type KRAS of p₀ = 0.0077, with α = 0.05 and 1-β = 0.60, the final sample size is 25 patients.

A short course of tofacitinib sustains the immunoregulatory effect of CTLA4-Ig in the presence of inflammatory cytokines and promotes long-term survival of murine cardiac allografts

Costimulation blockade-based regimens are a promising strategy for management of transplant recipients. However, maintenance immunosuppression via CTLA4-Ig monotherapy is characterized by high frequency of rejection episodes. Recent evidence suggests that inflammatory cytokines contribute to alloreactive T cell activation in a CD28-independent manner, a reasonable contributor to the limited efficacy of CTLA4-Ig. In this study, we investigated the possible synergism of a combined short-term inhibition of cytokine signaling and CD28 engagement on the modulation of rejection. Our results demonstrate that the JAK/STAT inhibitor tofacitinib restored the immunomodulatory effect of CTLA4-Ig on mouse alloreactive T cells in the presence of inflammatory cytokines. Tofacitinib exposure conferred dendritic cells with a tolerogenic phenotype reducing their cytokine secretion and costimulatory molecules expression. JAK inhibition also directly affected T cell activation. In vivo, the combination of CTLA4-Ig and tofacitinib induced long-term survival of heart allografts and, importantly, it was equally effective when using grafts subjected to prolonged ischemia. Transplant survival correlated with a reduction in effector T cells and intragraft accumulation of regulatory T cells. Collectively, our studies demonstrate a powerful synergism between CTLA4-Ig and tofacitinib and suggest their combined use is a promising strategy for improved management of transplanted patients.

Hookworm treatment induces a decrease of suppressive regulatory T cell associated with a Th2 inflammatory response

Background

Like other helminths, hookworms (HW) induce a regulatory immune response able to modulate and dampen reactivity of the host to antigens. No data about the evolution of the immune response after treatment are available. We aim to phenotype the regulatory immune response during natural HW infection and its evolution after treatment.

Methodology

Twenty hookworm infected (HW+) and 14 non-infected subjects HW–from endemic area in the periphery of Ho Chi Minh City were included. Blood and feces samples were obtained before, 2 and 4 weeks after treatment with Albendazole 400mg. Additional samples were obtained at 3 and 12 months in the HW+ group. Hematological parameters, Treg (CD4+CD25^hiFoxP3^hi) and surface molecules (CD39, CD62L, ICOS, PD-1, CD45RA) were measured as well as inflammatory and lymphocytes differentiation cytokines such as IL-1β, IL-6, IFNγ, IL-4, IL-17, IL-10, IL-2 and TGFβ.

Results

HW+ subjects showed higher Treg, TregICOS+, Treg PD1-, TregCD62L+ and CD45RA+FoxP3^lo resting Treg (rTreg). CD45RA-FoxP3^lo non-suppressive Treg cells were also increased. No preferential Th1/Th2 orientation was observed, nor difference for IL-10 between two groups. After treatment, Treg, TregICOS+, TregCD62L+, Treg PD1- and rTreg decreased while IL-4 and IL-6 cytokines increased.

Conclusion

During HW infection, Treg are increased and characterized by a heterogeneous population: a highly suppressive as well as a non-suppressive T cells phenotype. After treatment, Treg with immune-suppressive phenotype exhibited a decrease parallel to an inflammatory Th2 response.

Understanding and Targeting Human Cancer Regulatory T Cells to Improve Therapy

Regulatory T cells (Tregs) are critical in maintaining immune homeostasis under various pathophysiological conditions. A growing body of evidence demonstrates that Tregs play an important role in cancer progression and that they do so by suppressing cancer-directed immune responses. Tregs have been targeted for destruction by exploiting antibodies against and small-molecule inhibitors of several molecules that are highly expressed in Tregs-including immune checkpoint molecules, chemokine receptors, and metabolites. To date, these strategies have had only limited antitumor efficacy, yet they have also created significant risk of autoimmunity because most of them do not differentiate Tregs in tumors from those in normal tissues. Currently, immune checkpoint inhibitor (ICI)-based cancer immunotherapies have revolutionized cancer treatment, but the resistance to ICI is common and the elevation of Tregs is one of the most important mechanisms. Therapeutic strategies that can selectively eliminate Tregs in the tumor (i.e. therapies that do not run the risk of causing autoimmunity by affecting normal tissue), are urgently needed for the development of cancer immunotherapies. This chapter discusses specific properties of human Tregs under the context of cancer and the various ways to target Treg for cancer immunotherapy.

Increased Frequency of CTLA-4 and PD-1 Expressing Regulatory T Cells and Basophils With an Activating Profile in Infants With Moderate-to-Severe Atopic Dermatitis Hypersensitized to Food Allergens

Background: Infants with severe atopic dermatitis (AD) may be sensitized to foods that have not been introduced into their diet, posing a risk for developing an immediate hypersensitivity reaction on the first exposure to the food to which they are sensitized. The aim of this work was to perform an analysis of the sensitization profile in infants with moderate-to-severe AD and to identify cellular and molecular markers for food allergy (FA). Methods: Blood samples from healthy donors and children with moderate-to-severe AD were studied. Specific IgE to several allergens were determined using ImmunoCAP FEIA system and ISAC technology. Furthermore, using flow cytometry-based studies, basophils and regulatory T (Treg) cells were phenotypically characterized. Results: 90% of children with AD were sensitized to food antigens before introducing them into the diet, and 100% developed FA. Phenotypic analysis showed a significantly higher percentage of CTLA-4 and PD-1 expressing Treg cells in AD patients than in healthy controls. Basophils from patients exhibited a marked reduction in the expression of CD300a, higher expression of FcεRI and CXCR4, and to some extent higher expression of CD63 and CD300c. Conclusions: Infants with moderate-to-severe AD are at high risk of being sensitized to food allergens. Therefore, to avoid allergic reactions, broad-spectrum sensitization studies are necessary before introducing complementary diet. Increased expression of CTLA-4 and PD-1 suggests greater suppressive potential of Treg cells in infants with AD than healthy controls. Furthermore, our results suggest a role for CD300 molecules on circulating basophils as possible biomarkers for FA susceptibility.

Regulatory T cell phenotype and anti-osteoclastogenic function in experimental periodontitis

The alveolar bone resorption is a distinctive feature of periodontitis progression and determinant for tooth loss. Regulatory T lymphocytes (Tregs) display immuno-suppressive mechanisms and tissue repairing functions, which are critical to support periodontal health. Tregs may become unstable and dysfunctional under inflammatory conditions, which can even accelerate tissue destruction. In this study, experimental periodontitis was associated with the progressive and increased presence of Th17 and Treg-related mediators in the gingiva (IL-6, IL-17A, IL-17F, RANKL, IL-10, TGF-β and GITR; P < 0.05), and the proliferation of both Treg and Th17 cells in cervical lymph nodes. Tregs from cervical lymph nodes had reduced Foxp3 expression (> 25% MFI loss) and increased IL-17A expression (> 15%), compared with Tregs from spleen and healthy controls. Tregs gene expression analysis showed a differential signature between health and disease, with increased expression of Th17-associated factors in periodontitis-derived Tregs. The ex vivo suppression capacity of Tregs on osteoclastic differentiation was significantly lower in Tregs obtained from periodontally diseased animals compared to controls (P < 0.05), as identified by the increased number of TRAP⁺ osteoclasts (P < 0.01) in the Tregs/pre-osteoclast co-cultures. Taken together, these results demonstrate that Tregs become phenotypically unstable and lose anti-osteoclastogenic properties during experimental periodontitis; thus, further promoting the Th17-driven bone loss.

The role of the programmed cell death protein-1/programmed death-ligand 1 pathway, regulatory T cells and T helper 17 cells in tumor immunity: a narrative review

Tumor immunotherapy, especially that involving programmed cell death protein-1 (PD-1)/programmed death-ligand 1 (PD-L1) immunosuppressive checkpoint inhibitors, has become an important part of tumor treatment strategy in the past decade. Blocking PD-1/PD-L1 signaling pathway can reduce the inhibitory effect of PD-1 pathway on T cells, promote the anti-tumor activity of activated T cells, and prolong the remission period of tumor. While PD-1/PD-L1 immunotherapy is effective in the treatment of solid malignant tumors, it also has shortcomings, due to the complexity of the tumor microenvironment (TME). Regulatory T cells (Tregs) and T helper 17 (Th17) cells play an important role in the TME and are closely related to the occurrence and development of tumors. Tregs can inhibit the anti-tumor immune effect, while Th17 cells play a dual role in tumor immunity, which not only promotes tumorigenesis but also promotes anti-tumor immunity. In the occurrence and development of tumor, PD-1/PD-L1 pathway, Tregs and Th17 cells are interrelated. However, the complicated relationship between the PD-1/PD-L1 pathway, Tregs, and Th17 cells has not been fully clarified. Here, we summarize the immunoregulation mechanisms and discuss the crosstalk between the PD-1/PD-L1 pathway, Tregs, and Th17 cells, with the aim of providing novel insights for future cancer treatment.

Effect of Octreotide Long-Acting Release on Tregs and MDSC Cells in Neuroendocrine Tumour Patients: A Pivotal Prospective Study

Octreotide long-acting repeatable (LAR) is largely used to treat functional and/or metastatic neuroendocrine neoplasms (NENs). Its effect in controlling carcinoid syndrome and partially reduce tumour burden is attributable to the ability of octreotide to bind somatostatin receptors (SSTRs) on the tumour and metastasis, regulating growth hormone secretion and cell growth. Notably, SSTRs are also expressed, at different levels, on Tregs. Tregs, together with myeloid-derived suppressor cells (MDSCs), are key components in the anti-tumour immunoregulation. This is the first prospective study aimed to explore the impact of Octreotide (OCT) LAR on the immune system, with a particular focus on Tregs and MDSC cells. Here, we show that circulating Tregs are elevated in NENs patients compared to healthy donors and that treatment with OCT LAR significantly decrease the level of total Tregs and of the three functional Tregs populations: nTregs, eTregs and non-Tregs. Furthermore, OCT LAR treatment induces a functional impairment of the remaining circulating Tregs, significantly decreasing the expression of PD1, CTLA4 and ENTPD1. A trend in circulating MDSC cells is reported in patients treated with OCT LAR. The results reported here suggest that the effect of OCT LAR on Tregs could tip the balance of the patients' immune-system towards a durable anti-tumour immunosurveillance with consequent long-term control of the NENs disease.

Intracellular accumulation of PD-1 molecules in circulating T lymphocytes in advanced malignant melanoma: an implication for immune evasion mechanism

BACKGROUND

The blockade of cell surface PD-1 (_(sur)PD-1) by monoclonal antibodies, represented by nivolumab, provides the strategy to treat advanced malignant melanoma (AMM). The intracellular presence of PD-1 molecules have been reported in some T cell subsets, however, their kinetic association with those expressed on the cell surface, let alone their significance in antitumor immunity has been ill-investigated.

METHODS

Intracellular PD-1 expression status in T cell subsets in AMM cases during nivolumab administration was chronologically characterized. The kinetics of PD-1 molecules within AMM-derived T cells was assessed in vitro in conjunction with their functional properties.

RESULTS

Increase in _(sur)PD-1 and intracellular PD-1 (_(int)PD-1⁺) expression was characteristic for AMM T cells. After short-term culture, virtually _(sur)PD-1^- nivolumab-treated AMM T cells restore _(sur)PD-1 expression, which could not be explained by the detachment of nivolumab from PD-1 epitopes alone. The blockade of trans-Golgi network resulted in the decrease in the extent of _(sur)PD-1 recovery, suggesting the translocation of accumulated _(int)PD-1 to the cell surface. Antigen-specific PD-1⁺ T cells significantly increased in _(int)PD-1⁺ cells after treatment. In addition, a surge in _(int)PD-1⁺CD4⁺ T cells was observed prior to the emergence of skin rash as an immune-related adverse event (irAE).

CONCLUSIONS

Accumulated _(int)PD-1 in T cells may contribute to enhanced immune evasion in AMM. Evaluation of intracellular PD-1 expression would be useful for better management of nivolumab-treated AMM patients in view of predicting treatment response and the incidence of irAE. Our findings further support the necessity of periodical administration of nivolumab for treating AMM.

TIGIT Expression Is Associated with T-cell Suppression and Exhaustion and Predicts Clinical Outcome and Anti-PD-1 Response in Follicular Lymphoma

PURPOSE

T-cell immunoglobulin and ITIM domain (TIGIT), a member of the immune checkpoint family, is important in normal T-cell biology. However, the phenotypical profile and clinical relevance of TIGIT in follicular lymphoma is largely unknown.

EXPERIMENTAL DESIGN

Biopsy specimens from a cohort of 82 patients with follicular lymphoma were analyzed using mass cytometry to explore the phenotype and biological and clinical significance of TIGIT⁺ T cells.

RESULTS

TIGIT is highly expressed on intratumoral T cells and its expression alters T-cell phenotype in follicular lymphoma. TIGIT is abundantly expressed on T_reg cells, resulting in an enhanced suppressive property. TIGIT expression on non-T_reg/T_FH T cells defines a population that exhibits an exhausted phenotype. Clinically, increased numbers of TIGIT⁺ T cells are associated with inferior patient outcomes and poor survival. We observe that anti-PD-1 therapy with pembrolizumab alters the phenotype of TIGIT⁺ T subsets and identifies a role for CD28 expression on TIGIT⁺ T cells in treatment response.

CONCLUSIONS

The current study provides a comprehensive analysis of the phenotypic profile of intratumoral TIGIT⁺ T subsets and their prognostic relevance in follicular lymphoma. Inhibition of TIGIT signaling may be an additional mechanism to prevent T-cell suppression and exhaustion in B-cell lymphoma.

PD1 expression on bone marrow T‐cells in newly diagnosed Egyptian AML patients: Correlation with hematological parameters, aberrant antigens expression, and response to induction therapy

Background

Programed cell death protein 1 (PD‐1) is a key mediator for the development of T cell exhaustion that develops in response to persistent antigen stimulation.

Aim

In this study, we measured PD1 expression on CD3 positive bone marrow T‐lymphocytes in newly diagnosis AML patients and its relation to clinical/ prognostic outcomes in addition to response to induction therapy (day 28).

Methods

This study was conducted on 59 newly diagnosed AML patients and 20 healthy controls. Complete blood counts, flow cytometry using acute leukemia panel in addition to PD1 monoclonal antibodies were performed on bone marrow lymphocytes (CD3+), whereas cytogenetic/molecular studies were used to determine risk group. The patients’ remission status following induction therapy was determined.

Results

PD1 was brightly expressed in 91.5% of the cases than control sample with highly significant difference (P = .001). A cutoff of 3.5 for mean fluorescence intensity was used to divide patients into two groups (higher vs normal PD1 expression). A significant difference between the two groups regarding platelet count and aberrant CD7 expression (P = .007 and .023, respectively) was found. Those normally expressed PD1 respond better to induction therapy.

Conclusion

PD1 expression on BM T‐cells had a predictive value and providing an immunotherapeutic target for AML.

Attenuation of canonical NF-κB signaling maintains function and stability of human Treg

Nuclear factor ‘κ‐light‐chain‐enhancer’ of activated B cells (NF‐κB) signaling is a signaling pathway used by most immune cells to promote immunostimulatory functions. Recent studies have indicated that regulatory T cells (Treg) differentially integrate TCR‐derived signals, thereby maintaining their suppressive features. However, the role of NF‐κB signaling in the activation of human peripheral blood (PB) Treg has not been fully elucidated so far. We show that the activity of the master transcription factor forkhead box protein 3 (FOXP3) attenuates p65 phosphorylation and nuclear translocation of the NF‐κB proteins p50, p65, and c‐Rel following activation in human Treg. Using pharmacological and genetic inhibition of canonical NF‐κB signaling in FOXP3‐transgenic T cells and PB Treg from healthy donors as well as Treg from a patient with a primary NFKB1 haploinsufficiency, we validate that Treg activation and suppressive capacity is independent of NF‐κB signaling. Additionally, repression of residual NF‐κB signaling in Treg further enhances interleukin‐10 (IL‐10) production. Blockade of NF‐κB signaling can be exploited for the generation of in vitro induced Treg (iTreg) with enhanced suppressive capacity and functional stability. In this respect, dual blockade of mammalian target of rapamycin (mTOR) and NF‐κB signaling was accompanied by enhanced expression of the transcription factors FOXP1 and FOXP3 and demethylation of the Treg‐specific demethylated region compared to iTreg generated under mTOR blockade alone. Thus, we provide first insights into the role of NF‐κB signaling in human Treg. These findings could lead to strategies for the selective manipulation of Treg and the generation of improved iTreg for cellular therapy.

Cell-Penetrating Anti-Protein Kinase C Theta Antibodies Act Intracellularly to Generate Stable, Highly Suppressive Regulatory T Cells

Regulatory T cells maintain immunological tolerance and dampen inflammatory responses. Administering regulatory T cells can prevent the immune-mediated tissue destruction of graft-versus-host disease, which frequently accompanies hematopoietic stem cell transfer. Neutralizing the T cell-specific kinase, protein kinase C theta, which promotes T cell effector functions and represses regulatory T cell differentiation, augments regulatory T cell immunosuppression and stability. We used a synthetic, cell-penetrating peptide mimic to deliver antibodies recognizing protein kinase C theta into primary human CD4 T cells. When differentiated ex vivo into induced regulatory T cells, treated cells expressed elevated levels of the regulatory T cell transcriptional regulator forkhead box P3, the surface-bound immune checkpoint receptor programmed death receptor-1, and pro-inflammatory interferon gamma, previously ascribed to a specific population of stable, highly suppressive human induced regulatory T cells. The in vitro suppressive capacity of these induced regulatory T cells was 10-fold greater than that of T cells differentiated without antibody delivery. When administered at the time of graft-versus-host disease induction, using a humanized mouse model, antibody-treated regulatory T cells were superior to non-treated T cells in attenuating lethal outcomes. This antibody delivery approach may overcome obstacles currently encountered using patient-derived regulatory T cells as a cell-based therapy for immune modulation.

Mass Cytometry Analysis Reveals that Specific Intratumoral CD4+ T Cell Subsets Correlate with Patient Survival in Follicular Lymphoma

Follicular lymphoma (FL) is an indolent B cell malignancy characterized by an extensive but poorly functional T cell infiltrate in the tumor microenvironment. Using mass cytometry, we identified at least 12 subsets of intratumoral CD4⁺ T cells, 3 of which were unique to FL biopsies versus control tissues. Of these subsets, the frequency of naive T cells correlated with improved patient survival. Although total PD-1⁺ T cell numbers were not associated with patient outcome, specific PD-1⁺ T cell subpopulations were associated with poor survival. Intratumoral T cells lacking CD27 and CD28 co-stimulatory receptor expression were enriched in FL and correlated with inferior patient outcomes. In vitro models revealed that CD70⁺ lymphoma cells played an important role in expanding this population. Taken together, our mass cytometry results identified CD4⁺ memory T cell populations that are poorly functional due to loss of co-stimulatory receptor expression and are associated with an inferior survival in FL.

Yang et al. utilize mass cytometry (CyTOF) to characterize intratumoral T cells and explore the clinical relevance of T cell subsets in follicular lymphoma (FL). Clustering analysis reveals an immune signature with reduced expression of co-stimulatory molecules on intratumoral T cells that correlated with a poor prognosis in FL.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)

These guidelines are a consensus work of a considerable number of members of the immunology and flow cytometry community. They provide the theory and key practical aspects of flow cytometry enabling immunologists to avoid the common errors that often undermine immunological data. Notably, there are comprehensive sections of all major immune cell types with helpful Tables detailing phenotypes in murine and human cells. The latest flow cytometry techniques and applications are also described, featuring examples of the data that can be generated and, importantly, how the data can be analysed. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid, all written and peer-reviewed by leading experts in the field, making this an essential research companion.

Recent advances with Treg depleting fusion protein toxins for cancer immunotherapy

T regulatory cells (Tregs) are an important T cell population for immune tolerance, prevention of autoimmune diseases and inhibition of antitumor immunity. The tumor-promoting role played by Tregs in cancer has prompted numerous approaches to develop immunotherapeutics targeting Tregs. One approach to depletion of Treg cells is retargeting the highly potent cytotoxic activity of bacterial toxins. These agents capitalize on the well-characterized bacterial toxins, diphtheria toxin and Pseudomonas aeruginosa exotoxin A-both of which harbor membrane translocation domains and enzymatic domains that catalytically halt protein synthesis within intoxicated eukaryotic cells and act at picomolar or subpicomolar concentrations. In this review, we summarize the preclinical and clinical development of several Treg-depleting cancer immunotherapies based on these two bacterial toxins.

Expression of costimulatory and inhibitory receptors in FoxP3+ regulatory T cells within the tumor microenvironment: Implications for combination immunotherapy approaches

The unprecedented success of immune checkpoint inhibitors has given rise to a rapidly growing number of immuno-oncology agents undergoing preclinical and clinical development and an exponential increase in possible combinations. Defining a clear rationale for combinations by identifying synergies between immunomodulatory pathways has therefore become a high priority. Immunosuppressive regulatory T cells (Tregs) within the tumor microenvironment (TME) represent a major roadblock to endogenous and therapeutic tumor immunity. However, Tregs are also essential for the maintenance of immunological self-tolerance, and share many molecular pathways with conventional T cells including cytotoxic T cells, the primary mediators of tumor immunity. Hence the inability to specifically target and neutralize Tregs within the TME of cancer patients without globally compromising self-tolerance poses a significant challenge. Here we review recent advances in the characterization of tumor-infiltrating Tregs with a focus on costimulatory and inhibitory receptors. We discuss receptor expression patterns, their functional role in Treg biology and mechanistic insights gained from targeting these receptors in preclinical models to evaluate their potential as clinical targets. We further outline a framework of parameters that could be used to refine the assessment of Tregs in cancer patients and increase their value as predictive biomarkers. Finally, we propose modalities to integrate our increasing knowledge on Treg phenotype and function for the rational design of checkpoint inhibitor-based combination therapies. Such combinations have great potential for synergy, as they could concomitantly enhance cytotoxic T cells and inhibit Tregs within the TME, thereby increasing the efficacy of current cancer immunotherapies.

Exploring the role of programmed cell death protein 1 and its ligand 1 in eye diseases

Programmed death receptor-1 (PD-1) and its ligand, PD-L1, as negative co-stimulatory molecules, are indispensable for regulating both physiological and pathological immune responses. The PD-1/PD-L1-mediated signaling pathway has been studied extensively in cancer research and has become a hotspot for biopharmaceuticals and immunotherapy. Furthermore, monoclonal antibodies to PD-1 have just been approved by the US Food and Drug Administration to treat certain types of malignancies. Recent research has unveiled a close association between the PD-1/PD-L1 system and eye diseases. This review describes the expression and physiological functions of PD-1 and its ligand in ocular tissues and summarizes the pathogenic, regulatory, and therapeutic roles of PD-1/PD-L1 system in eye diseases, including uveal melanoma, autoimmune uveitis, autoimmune dry eye, sympathetic ophthalmia, Graves' ophthalmopathy, diabetic retinopathy, herpes simplex keratitis, and trachoma, with the intent of highlighting the potential of PD-1/PD-L1 as novel therapeutic targets or biomarkers for these ocular diseases.

New challenges in integrated diagnosis by imaging and osteo-immunology in bone lesions

INTRODUCTION

High-resolution imaging is the gold standard to measure the functional and biological features of bone lesions. Imaging markers have allowed the characterization both of tumour heterogeneity and metabolic data. Besides, ongoing studies are evaluating a combined use of 'imaging markers', such as SUVs, MATV, TLG, ADC from PET and MRI techniques respectively, and several 'biomarkers' spanning from chemokine immune-modulators, such as PD-1, RANK/RANKL, CXCR4/CXCL12 to transcription factors, such as TP53, RB1, MDM2, RUNX family, EZH2, YY1, MAD2. Osteoimmunology may improve diagnosis and prognosis leading to precision medicine in bone lesion treatment. Areas covered: We investigated modalities (molecular and imaging approach) useful to identify bone lesions deriving both from primary bone tumours and from osteotropic tumours, which have a higher incidence, prevalence and prognosis. Here, we summarized the recent advances in imaging techniques and osteoimmunology biomarkers which could play a pivotal role in personalized treatment. Expert commentary: Although imaging and molecular integration could allow both early diagnosis and stratification of cancer prognosis, large scale clinical trials will be necessary to translate pilot studies in the current clinical setting.

ABBREVIATIONS

ADC: apparent diffusion coefficient; ALCAM: Activated Leukocyte Cell Adhesion Molecule; ALP: Alkaline phosphatases; BC: Breast cancer; BSAP: B-Cell Lineage Specific Activator; BSAP: bone-specific alkaline phosphatase; BSP: bone sialoprotein; CRIP1: cysteine-rich intestinal protein 1; CD44: cluster of differentiation 44; CT: computed tomography; CXCL12: C-X-C motif ligand 12; CXCR4: C-X-C C-X-C chemokine receptor type 4; CTLA-4: Cytotoxic T-lymphocyte antigen 4; CTX-1: C-terminal end of the telopeptide of type I collagen; DC: dendritic cell; DWI: Diffusion-weighted MR image; EMT: mesenchymal transition; ET-1: endothelin-1; FDA: Food and Drug Administration; FDG: ¹⁸F-2-fluoro-2-deoxy-D-glucose; FGF: fibroblast growth factor; FOXC2: forkhead box protein C2: HK-2: hexokinase-2; ICTP: carboxyterminal cross-linked telopeptide of type I collagen; IGF-1R: Insulin Like Growth Factor 1 Receptor; ILC: innate lymphocytes cells; LC: lung cancer; IL-1: interleukin-1; LYVE1: lymphatic vessel endothelial hyaluronic acid receptor 1; MAD2: mitotic arrest deficient 2; MATV: metabolically active tumour volume; M-CSF: macrophage colony stimulating factor; MM: multiple myeloma; MIP1a: macrophage inflammatory protein 1a; MSC: mesenchymal stem cell; MRI: magnetic resonance imaging; PC: prostate cancer; NRP2: neuropilin 2; OPG: osteoprotogerin; PDGF: platelet-derived growth factor; PD-1: Programmed Cell Death 1; PET: positron emission tomography; PINP: procollagen type I N propeptide; PROX1: prospero homeobox protein 1; PSA: Prostate-specific antigen; PTH: parathyroid hormone; RANK: Receptor activator of NF-kB ligand; RECK: Reversion-inducing-cysteine-rich protein; SEMAs: semaphorins; SPECT: single photon computed tomography; SUV: standard uptake value; TLG: total lesion glycolysis; TP53: tumour protein 53; VCAM-1: vascular endothelial molecule-1; VOI: volume of interest; YY1: Yin Yang 1.

Inhibitory Receptors and Pathways of Lymphocytes: The Role of PD-1 in Treg Development and Their Involvement in Autoimmunity Onset and Cancer Progression

Regulatory T (Treg) cells represent a subpopulation of suppressor CD4⁺ T cells critically involved in the establishment of peripheral tolerance through the inhibition of effector T (Teff) cells and the suppression of the immune-mediated tissue destruction toward self-antigens. Treg generation, their suppressive properties and also Treg-Teff cell interactions could be modulated at least in part by programmed cell death-1 (PD-1) expression on their surface and through binding between PD-1 and programmed cell death ligand-1 (PD-L1). Defects involving PD-1 and Tregs can lead to the development of pathological conditions, including autoimmune disorders or promote cancer progression by favoring tumor evasion from the host immune response. At the same time, PD-1 and Tregs could represent attractive targets for treatment, as demonstrated by the therapeutic blockade of PD-L1 applied for the management of different cancer conditions in humans. In the present Review, we focus specifically the role of PD-1/PD-L1 on Treg development and activity.

Correlation of PD-1/PD-L1 Signaling Pathway with Treg/Th17 Imbalance from Asthmatic Children

BACKGROUND

The balance between T helper 17 (Th17) and regulatory T cells (Treg) is a new paradigm in asthma pathogenesis, but no therapeutic targets could modulate the Th17/Treg balance specifically for asthma. Since previous studies have shown the programmed cell death-1(PD-1)/PD-ligand 1 (PD-L1) pathway is critical to immune homeostasis in this disease, we hypothesized that the PD-1/PD-L1 pathway might be involved in the regulation of Treg/Th17 imbalance in asthmatic children.

METHODS

The percentage of Treg and Th17 cells and the expression of PD-1 and PD-L1 were detected by flow cytometry in children with asthma and healthy controls. CD4+ T cells were stimulated with Th17 and Treg differentiating factors, and treated with anti-PD-1. Then cells were harvested and measured for Th17 and Treg percentages and Foxp3 and RORγt levels using RT-PCR.

RESULTS

We observed an inverse correlation between the percentages of Treg and Th17 cells, and the expression of PD-1 and PD-L1 in the two subsets also changed in the mild persistent and moderate to severe persistent groups compared with healthy controls. In vitro, administration of anti-PD-1 could decrease Th17 percentages and RORγt mRNA, and increase Treg percentages and Foxp3 mRNA in CD4+ T cells of children with asthma in the mild persistent and moderate to persistent groups. Additionally, the role played by anti-PD-1 in regulating Treg/Th17 balance was further confirmed in an asthmatic mouse model.

CONCLUSION

Alteration of the PD-1/PD-L1 pathway can modulate Treg/Th17 balance in asthmatic children. Treatment with anti-PD-1 posed protective effects on asthma models, providing a novel theoretical target for asthma.

Shared and Unique Features Distinguishing Follicular T Helper and Regulatory Cells of Peripheral Lymph Node and Peyer's Patches

Follicular helper (TFH) and regulatory (TFR) cells are critical players in managing germinal center (GC) reactions that accomplish effective humoral immune responses. Transcriptome analyses were done comparing gene regulation of TFH and TFR cells isolated from Peyer’s Patches (PP) and immunized peripheral lymph nodes (pLNs) revealing many regulatory patterns common to all follicular cells. However, in contrast to TFH cells, the upregulation or downregulation of many genes was attenuated substantially in pLN TFR cells when compared to those of PP. Additionally, PP but not pLN TFR cells were largely unresponsive to IL2 and expressed Il4 as well as Il21. Together with fundamental differences in gene expression that were found between cells of both compartments this emphasizes specific adaptations of follicular T cell functions to their micro-milieu. Moreover, although GL7 expression distinguishes matured follicular T cells, GL7⁺ as well as GL7⁻ cells are present in the GC.

Phase II study of idelalisib, a selective inhibitor of PI3Kδ, for relapsed/refractory classical Hodgkin lymphoma

Background

The phosphatidylinositol-3-kinase delta (PI3Kδ) inhibitor idelalisib has been shown to block downstream intracellular signaling, reduce the production of prosurvival chemokines and induce apoptosis in classical Hodgkin lymphoma (HL) cell lines. It has also been shown to inhibit regulatory T cells and myeloid-derived suppressor cells in other tumor models. We hypothesized that inhibiting PI3Kδ would have both direct and indirect antitumor effects by directly targeting the malignant cells as well as modulating the inflammatory microenvironment. We tested this hypothesis in a phase II study.

Patients and methods

We enrolled 25 patients with relapsed/refractory HL with a median age of 42 years and who had previously received a median of five therapies including 18 (72%) with failed autologous stem cell transplant, 23 (92%) with failed brentuximab vedotin, and 11 (44%) with prior radiation therapy. Idelalisib was administered at 150 mg two times daily; an increase to 300 mg two times daily was permitted at the time of disease progression.

Results

The overall response rate to idelalisib therapy was 20% (95% confidence interval: 6.8%, 40.7%) with a median time to response of 2.0 months. Seventeen patients (68%) experienced reduction in target lesions with one complete remission and four partial remissions. The median duration of response was 8.4 months and median progression-free survival was 2.3 months. The most common grade ≥3 adverse event was elevation of alanine aminotransferase (two patients, 8%). Diarrhea/colitis was seen in three patients and was grade 1-2. There was one adverse event leading to death (hypoxia).

Conclusions

Idelalisib was tolerable and had modest single-agent activity in heavily pretreated patients with HL. Rational combinations with other novel agents may improve response rate and duration of response.

Clinical trial registration

ClinicalTrials.gov # NCT01393106.

Fibrinogen-like protein-2 causes deterioration in cardiac function in experimental autoimmune myocarditis rats through regulation of programmed death-1 and inflammatory cytokines

Programmed death-1 (PD-1) plays an important role in protecting against inflammation and myocyte damage in T-cell-mediated myocarditis. To understand whether fibrinogen-like protein-2 (FGL2) can affect the role of the PD-1/PD-L1 pathway in experimental autoimmune myocarditis (EAM), we investigated cardiac function in EAM rats over-expressing FGL2. Over-expression of FGL2 significantly decreased PD-1 and deteriorated cardiac function in rats with autoimmune myocarditis. Histopathology revealed increased inflammatory cell infiltrate in EAM-FGL2 rats compared with the control groups (EAM, EAM-GFP and NC). Notably, transcription factor forkhead box P3 (Foxp3) and retinoic acid-related orphan receptor γt (RORγt) protein and mRNA levels were statistically (P < 0·05) increased in EAM rats. We also found that interferon-γ, interleukin-6, interleukin-17 and brain natriuretic peptide levels were profoundly increased in serum of FGL2 over-expressing EAM rats. Hence, FGL2 plays an important role in the pathogenesis of autoimmune myocarditis that also involves the PD-1/PD-L1 pathway. Our findings may provide novel therapeutic targets for the treatment of immune-induced heart injury.

Update on the Therapeutic Efficacy of Tregs in IBD: Thumbs up or Thumbs down?

Crohn's disease and ulcerative colitis, the 2 major forms of inflammatory bowel disease (IBD) in humans, arise in genetically predisposed individuals because of an abnormal immune response direct against constituents of the gut flora. Defects in counter-regulatory mechanisms are supposed to amplify and maintain the IBD-associated mucosal inflammation. Therefore, restoring the balance between inflammatory and anti-inflammatory pathways in the gut could contribute to halt the IBD-associated tissue-damaging immune response. Various suppressive T cell (Tregs) subsets have been characterized phenotypically and functionally and over the last decade, there has been enormous effort for optimizing the procedures for the in vitro expansion/generation of these cells for therapeutic purposes. Here we review the mechanisms of action and functional relevance of Tregs in the maintenance of gut inflammation and analyze the available data about the use of these cells in the treatment of IBD patients.

PD-1 and PD-L1 expression in bone and soft tissue sarcomas

PD-1 and its ligands have been shown to play a significant role in evasion of malignant tumour cells from the immune system. Last year, the Unites States Food and Drug Administration (FDA) approved anti-PD-1 inhibitors for treatment of non-small cell lung carcinoma and recently expanded the use of immunotherapy for metastatic urothelial cell carcinoma and Hodgkin lymphoma. However, studies on expression of PD-1 and its ligand in malignant bone and soft tissue sarcoma are sparse. In this study, we evaluated PD-1 and PD-L1 expression on variants of liposarcomas and rhabdomyosarcomas, osteosarcomas and chondrosarcomas. Tissue microarrays (TMAs) for liposarcomas (well differentiated, myxoid/round cell, and pleomorphic), rhabdomyosarcomas (alveolar, embryonal, pleomorphic, and spindle cell), conventional osteosarcomas and chondrosarcomas were stained for PD-1 and PD-L1 antibodies. Adipose tissue, skeletal muscle, bone, osteochondroma and lipoma were used as control and benign counterparts. Western blot was performed to evaluate expression of PD-1 and PD-L1 in four sarcoma cell lines. Osteosarcomas, chondrosarcomas, and all variants of liposarcomas and rhabdomyosarcomas over-expressed PD-1 relative to normal tissue. Expression of PD-1 in rhabdomyosarcomas was associated with higher tumour stage. Only one case of pleomorphic liposarcoma, one case of pleomorphic rhabdomyosarcoma and two cases of alveolar rhabdomyosarcomas were positive for PD-L1. Normal adipose tissue, skeletal muscle, and bone were negative for both PD-1 and PD-L1 and lipomas and osteochondroma weakly expressed PD-1 but not PD-L1. Western blot confirmed the presence of PD-1 protein in all four sarcoma cell lines. Overall, our results showed cytoplasmic expression of PD-1 in the bone and soft tissue sarcomas, while PD-L1 was negative. Whether these data are an indication for effectiveness of immunotherapy in the management of malignant bone and soft tissue sarcomas remains to be elucidated.

Tumor immunotherapy: drug-induced neoantigens (xenogenization) and immune checkpoint inhibitors

More than 40 years ago, we discovered that novel transplantation antigens can be induced in vivo or in vitro by treating murine leukemia with dacarbazine. Years later, this phenomenon that we called "Chemical Xenogenization" (CX) and more recently, "Drug-Induced Xenogenization" (DIX), was reproduced by Thierry Boon with a mutagenic/carcinogenic compound (i.e. N-methyl-N'-nitro-N-nitrosoguanidine). In both cases, the molecular bases of DIX rely on mutagenesis induced by methyl adducts to oxygen-6 of DNA guanine. In the present review we illustrate the main DIX-related immune-pharmacodynamic properties of triazene compounds of clinical use (i.e. dacarbazine and temozolomide).In recent years, tumor immunotherapy has come back to the stage with the discovery of immune checkpoint inhibitors (ICpI) that show an extraordinary immune-enhancing activity. Here we illustrate the salient biochemical features of some of the most interesting ICpI and the up-to-day status of their clinical use. Moreover, we illustrate the literature showing the direct relationship between somatic mutation burden and susceptibility of cancer cells to host's immune responses.When DIX was discovered, we were not able to satisfactorily exploit the possible presence of triazene-induced neoantigens in malignant cells since no device was available to adequately enhance host's immune responses in clinical settings. Today, ICpI show unprecedented efficacy in terms of survival times, especially when elevated mutation load is associated with cancer cells. Therefore, in the future, mutation-dependent neoantigens obtained by appropriate pharmacological intervention appear to disclose a novel approach for enhancing the therapeutic efficacy of ICpI in cancer patients.

Association of PD-1.5 C/T, but Not PD-1.3 G/A, with Malignant and Benign Brain Tumors in Iranian Patients

Programmed death-1 (PD-1) negatively regulates the immune response. The aims of this study were to assess the association of two single nucleotide polymorphisms in the PD-1 gene, PD-1.5 (+7785 C/T-rs2227981) and PD-1.3 (+7146 G/A- rs11568821), with benign and malignant brain tumors. Patients with brain tumors (96 patients with benign and 56 with malignant brain tumors) and 150 healthy control individuals were included. PCR-RFLP was performed for genotyping. It was revealed that the genotype and allele frequencies of PD-1.5 C/T polymorphism were significantly different between all brain tumor patients and the control group. The frequencies of the CT genotype and T allele were higher in brain tumor patients. In contrast, the frequency of PD-1.3 G/A genotypes and alleles showed no significant difference between all brain tumor patients and controls. Patients were then divided into malignant and benign groups. The results revealed a significant difference in both patients groups compared with the controls only at PD-1.5 C/T position. Arlequin analysis showed the GC haplotype was the most frequent haplotype in the whole group of patients and controls, and the GT haplotype was significantly different between patient and control groups. In conclusion, we demonstrate that PD-1.5 C/T polymorphism, but not PD-1.3 G/A, is associated with brain tumors in Iranian patients.

Role of TIM-3 in ovarian cancer

Evidences have suggested that immunotherapy for ovarian cancer is effective. Immune checkpoints have emerged in the field of cancer immunotherapy. Multiple studies have shown negative regulation of TIM-3 expression on CD4⁺ and CD8⁺ T cells and other immunocytes. Overexpression of TIM-3 in innate immune cells has been found in certain types of tumor. The blockade of TIM-3 leads to sustained anti-tumor reactions. TIM-3 plays an inhibitive role for immunity in ovarian cancer. TIM-3 is involved in the development of various subtypes of ovarian cancer and thus has the potential to be a therapeutic target for treatment of ovarian cancer.

Programmed death ligand 1 is expressed in canine B cell lymphoma and downregulated by MEK inhibitors

Programmed death ligand 1 (PD-L1) expression in antigen-presenting cells and tumors can inhibit T cell-mediated immunity. In this study, PD-L1 mRNA and protein expression was evaluated in canine B cell lymphoma (CLL17-71), large T-cell leukemia (CLGL-90), B cell leukemia (GL-1) and primitive leukocyte round cell neoplasia (CLL-1390). Variable PD-L1 mRNA and protein were observed in these cells with high endogenous expression present in CLL17-71 cells. PD-L1 protein was also observed in canine patient B cell lymphoma tissues using immunostaining. PD-L1 and signal transducer and activator of transcription 1 ( STAT1 ) mRNA expression were reduced in the presence of mitogen-activated protein kinase kinase 1.2 (MEK1/2) inhibitors RDEA119 and AZD6244 in CLL 17-71 cells. RDEA119 had similar effect on PD-L1 and STAT-1 in IFN-γ activated CLL-1390 cells. Overall, these results indicate that PD-L1 is expressed in canine B cell lymphoma. Its inhibition by MEK1/2 inhibitors suggests a possible treatment strategy using targeted drugs which likely could enhance antitumor immune response.

Therapeutic Potential of Targeting the Th17/Treg Axis in Autoimmune Disorders

A disruption of the crucial balance between regulatory T-cells (Tregs) and Th17-cells was recently implicated in various autoimmune disorders. Tregs are responsible for the maintenance of self-tolerance, thus inhibiting autoimmunity, whereas pro-inflammatory Th17-cells contribute to the induction and propagation of inflammation. Distortion of the Th17/Treg balance favoring the  pro-inflammatory Th17 side is hence suspected to contribute to exacerbation of autoimmune disorders. This review aims to summarize recent data and advances in targeted therapeutic modification of the Th17/Treg-balance, as well as information on the efficacy of candidate therapeutics with respect to the treatment of autoimmune diseases.

The epigenetic landscape of T cell exhaustion

Exhausted T cells in cancer and chronic viral infection express distinctive patterns of genes, including sustained expression of programmed cell death protein 1 (PD-1). However, the regulation of gene expression in exhausted T cells is poorly understood. Here, we define the accessible chromatin landscape in exhausted CD8⁺ T cells and show that it is distinct from functional memory CD8⁺ T cells. Exhausted CD8⁺ T cells in humans and a mouse model of chronic viral infection acquire a state-specific epigenetic landscape organized into functional modules of enhancers. Genome editing shows that PD-1 expression is regulated in part by an exhaustion-specific enhancer that contains essential RAR, T-bet, and Sox3 motifs. Functional enhancer maps may offer targets for genome editing that alter gene expression preferentially in exhausted CD8⁺ T cells.

Phenotypical characterization of regulatory T cells in humans and rodents

Regulatory T cells (Tregs ) constitute a fascinating subpopulation of CD4(+) T cells due to their ability to limit the immune response against self and non-self antigens. Murine models and antibodies directed against surface and intracellular molecules have allowed elucidation of the mechanisms that govern their development and function. However, these markers used to their classification lack of specificity, as they can be expressed by activated T cells. Similarly, there are slight differences between animal models, in steady state and pathological conditions, anatomical localization and strategy of analysis by flow cytometry. Here, we revised the most common markers utilized for Treg typification by flow cytometry such as CD25, forkhead box protein 3 (FoxP3) and CD127, along with our data obtained in different body compartments of humans, mice and rats. Furthermore, we revised and determined the expression of other molecules important for the phenotypical characterization of Treg cells. We draw attention to the drawbacks of those markers used in chronic states of inflammation. However, until a specific marker for the identification of Tregs is discovered, the best combination of markers will depend upon the tissue or the degree of inflammation from which Tregs derive.

T-Cell Activation Independently Associates With Immune Senescence in HIV-Infected Recipients of Long-term Antiretroviral Treatment

Background.  Aging-associated noncommunicable comorbidities are more prevalent among human immunodeficiency virus type 1 (HIV)–infected individuals than among HIV-uninfected individuals. Residual HIV-related chronic immune activation and senescence may increase the risk of developing comorbidities.

Methods.  Immune phenotyping, thymic output, and telomere length were assessed in 94 HIV-infected individuals who were aged >45 years and receiving antiretroviral therapy (ART; cases) and 95 age-matched uninfected controls.

Results.  Cases had lower CD4+ T-cell counts, higher CD8+ T-cell counts, and increased levels of immune activation (ie, increased soluble CD14 [sCD14] level and increased percentages of CD38+HLA-DR+ cells among both CD4+ and CD8+ T cells), regulatory T cells, and percentage of programmed cell death 1 (PD-1)–expressing cells among CD4+ T cells. Immune senescence levels (ie, percentages of CD27−CD28− cells or CD57+ cells) were comparable between cases and controls. Peripheral blood mononuclear cells from cases had shorter telomeres but increased single-joint T-cell receptor excision circle content and CD31+ naive CD4+ T cells. Although cytomegalovirus (CMV) antibody titers were higher in cases, CMV-specific T-cell responses were comparable between cases and controls. T-cell senescence in cases was independently associated with T-cell activation but not with CMV-specific immune responses.

Conclusions.  Despite long-term receipt of ART, HIV-infected adults had higher levels of immune activation, regulatory T cells, and PD-1–expressing CD4+ cells and shorter telomeres. The increased soluble CD14 levels and percentage of CD38+HLA-DR+ cells among CD4+ T cells correlated with shorter telomeres and increased regulatory T-cell levels. This suggests that HIV influences immune function irreversibly, with several pathways that are persistently abnormal during effective ART. Therapies aimed at improving immune health during ART are needed.

Effects of lung cancer cell-associated B7-H1 on T-cell proliferation in vitro and in vivo

B7 homolog 1 (B7-H1) is the most potent immunoinhibitory molecule in the B7 family. In this study, we examined the effects of tumor-associated B7-H1 on T-cell proliferation in lung cancer. The expression of B7-H1 in human adenocarcinoma A549 and mouse Lewis lung carcinoma (LLC) cells were examined by flow cytometry. To assess the in vitro effect of tumor-associated B7-H1 on T-cell proliferation, we isolated T cells from peripheral blood mononuclear cells (PBMCs) of healthy individuals, labeled them with carboxyfluorescein succinimidyl ester, and co-cultured them with A549 cells in the absence or presence of anti-B7-H1 antibody. For in vivo analysis, LLC cells were subcutaneously injected into mice treated or not with anti-B7-H1 antibody. T-cell proliferation in both in vitro and in vivo assays was analyzed by flow cytometry. In vitro, co-culturing T cells with A549 cells significantly inhibited the proliferation of the former compared with the proliferation of T cells alone (P<0.01), and the addition of B7-H1 blocking antibody dramatically reversed the inhibition of T-cell proliferation by A549 cells. Similarly, in mice bearing LLC-derived xenograft tumors, in vivo administration of anti-B7-H1 antibody significantly increased the total number of spleen and tumor T cells compared to levels in control mice that did not receive anti-B7-H1 antibody. Functionally, in vivo administration of anti-B7-H1 antibody markedly reduced tumor growth. Tumor-associated B7-H1 may facilitate immune evasion by inhibiting T-cell proliferation. Targeting of this mechanism offers a promising therapy for cancer immunotherapy.