Engagement of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) induces transforming growth factor beta (TGF-beta) production by murine CD4(+) T cells

The nexus between Leishmania & HIV: Debilitating host immunity and Hastening Comorbid disease burden

The scintillating association between Leishmania and HIV has contributed exceptionally towards expansion of Visceral Leishmaniasis (VL) with Acquired Immunodeficiency Syndrome (AIDS). The co-infection poses a grievous threat to elimination of VL and containment of Human Immunodeficiency Virus (HIV). When coinfected, Leishmania and HIV complement each other's proliferation and survival by inducing immunesenescence, T cell fatigue and exhaustion. Antigen presentation is lost, co-stimulatory molecules are diminished whereas co-inhibitory molecules such as CTLA-4, TIGIT, LAG-3 etc. are upregulated to ensure a Th2-baised immune environment. As a consequence, Leishmania-HIV coinfection causes poor outcomes, inflates the spread of Leishmania parasites, enhances the severity of side-effects to drugs, as well as escalate the probability of treatment failure and mortality. What makes control extremely strenuous is that there are frequent episodes of VL relapse with no prognostic markers, no standard immunophenotype(s) and appearance of atypical clinical symptoms. Thus, a standard therapeutic regimen has been difficult to develop and treatment is majorly dependent upon a combination of liposomal Amphotericin B and Miltefosine, a therapy that is expensive and capable of causing drastic side-effects in recipients. As World Health Organization is committed to eliminate both VL and HIV in due course of future, the existing therapeutic interventions require advancements to grapple and overcome this hazardous co-infection. In this context, an overview of HIV-VL co-infection, immunopathology of HIV and Leishmania co-inhabitance, available therapeutic options and their limitations in the treatment of co-infection are discussed in-depth.

Advances in immunotherapy for breast cancer and feline mammary carcinoma: From molecular basis to novel therapeutic targets

The role of inflammation in cancer is a topic that has been investigated for many years. As established, inflammation emerges as a defining characteristic of cancer, presenting itself as a compelling target for therapeutic interventions in the realm of oncology. Controlling the tumor microenvironment (TME) has gained paramount significance, modifying not only the effectiveness of immunotherapy but also modulating the outcomes and prognoses of standard chemotherapy and other anticancer treatments. Immunotherapy has surfaced as a central focus within the domain of tumor treatments, using immune checkpoint inhibitors as cancer therapy. Immune checkpoints and their influence on the tumor microenvironment dynamic are presently under investigation, aiming to ascertain their viability as therapeutic interventions across several cancer types. Cancer presents a significant challenge in humans and cats, where female breast cancer ranks as the most prevalent malignancy and feline mammary carcinoma stands as the third most frequent. This review seeks to summarize the data about the immune checkpoints cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), lymphocyte activation gene-3 (LAG-3), programmed cell death protein-1 (PD-1), V-domain Ig suppressor of T cell activation (VISTA), and T-cell immunoglobulin and mucin domain 3 (TIM-3) respective ongoing investigations as prospective targets for therapy for human breast cancer, while also outlining findings from studies reported on feline mammary carcinoma (FMC), strengthening the rationale for employing FMC as a representative model in the exploration of human breast cancer.

Immune checkpoint inhibitors and cancer immunotherapy by aptamers: an overview

Efforts in cancer immunotherapy aim to counteract evasion mechanisms and stimulate the immune system to recognise and attack cancer cells effectively. Combination therapies that target multiple aspects of immune evasion are being investigated to enhance the overall efficacy of cancer immunotherapy. PD-1 (Programmed Cell Death Protein 1), CTLA-4 (Cytotoxic T-Lymphocyte Antigen 4), LAG-3 (Lymphocyte-Activation Gene 3), and TIM-3 (T Cell Immunoglobulin and Mucin Domain-Containing Protein3) are all immune checkpoint receptors that play crucial roles in regulating the immune response and maintaining self-tolerance often exploited by cancer cells to evade immune surveillance. Antibodies targeted against immune checkpoint inhibitors such as anti-PD-1 antibodies (e.g., pembrolizumab, nivolumab), anti-CTLA-4 antibodies (e.g., Ipilimumab), and experimental drugs targeting LAG-3 and TIM-3, aim to block these interactions and unleash the immune system's ability to recognise and destroy cancer cells. The US FDA has approved different categories of immune checkpoint inhibitors that have been utilised successfully in some patients with metastatic melanoma, renal cell carcinoma, head and neck cancers, and non-small lung cancer. Although several immune checkpoint inhibitor antibodies have been developed, they exhibited immune-related adverse effects, resulting in hypophysitis, diabetes, and neurological issues. These adverse effects of antibodies can be reduced by developing aptamer against the target. Aptamers offer several advantages over traditional antibodies, such as improved specificity, reduced immunogenicity, and flexible design for reduced adverse effects that specifically target and block protein-protein or receptor-ligand interactions involved in immune checkpoint pathways. The current study aims to review the function of particular immune checkpoint inhibitors along with developed aptamer-mediated antitumor cytotoxicity in cancer treatment.

Inhibition of Immunological Suppression

This Pillars of Immunology article is a commentary on “Cytotoxic T lymphocyte-associated antigen 4 plays an essential role in the function of CD25+CD4+ regulatory cells that control intestinal inflammation,” a pivotal article written by S. Read, V. Malmström, and F. Powrie, and published in the Journal of Experimental Medicine, in 2000. https://doi.org/10.1084/jem.192.2.295.

Targeting Cbl-b in cancer immunotherapy

Cancer immunotherapy with immune-checkpoint blockade has improved the outcomes of patients with various malignancies, yet a majority do not benefit or develop resistance. To address this unmet need, efforts across the field are targeting additional coinhibitory receptors, costimulatory proteins, and intracellular mediators that could prevent or bypass anti-PD1 resistance mechanisms. The CD28 costimulatory pathway is necessary for antigen-specific T cell activation, though prior CD28 agonists did not translate successfully to clinic due to toxicity. Casitas B lymphoma-b (Cbl-b) is a downstream, master regulator of both CD28 and CTLA-4 signaling. This E3 ubiquitin ligase regulates both innate and adaptive immune cells, ultimately promoting an immunosuppressive tumor microenvironment (TME) in the absence of CD28 costimulation. Recent advances in pharmaceutical screening and computational biology have enabled the development of novel platforms to target this once 'undruggable' protein. These platforms include DNA encoded library screening, allosteric drug targeting, small-interfering RNA inhibition, CRISPR genome editing, and adoptive cell therapy. Both genetic knock-out models and Cbl-b inhibitors have been shown to reverse immunosuppression in the TME, stimulate cytotoxic T cell activity, and promote tumor regression, findings augmented with PD1 blockade in experimental models. In translating Cbl-b inhibitors to clinic, we propose specific gene expression profiles that may identify patient populations most likely to benefit. Overall, novel Cbl-b inhibitors provide antigen-specific immune stimulation and are a promising therapeutic tool in the field of immuno-oncology.

T Lymphocyte Exhaustion During Human and Experimental Visceral Leishmaniasis

A key point of immunity against protozoan Leishmania parasites is the development of an optimal T cell response, which includes a low apoptotic rate, high proliferative activity and polyfunctionality. During acute infection, antigen-specific T cells recognize the pathogen resulting in pathogen control but not elimination, promoting the development and the maintenance of a population of circulating effector cells that mount rapid response quickly after re-exposure to the parasite. However, in the case of visceral disease, the functionality of specific T cells is lost during chronic infection, resulting in inferior effector functions, poor response to specific restimulation, and suboptimal homeostatic proliferation, a term referred to as T cell exhaustion. Multiple factors, including parasite load, infection duration and host immunity, affect T lymphocyte exhaustion. These factors contribute to antigen persistence by promoting inhibitory receptor expression and sustained production of soluble mediators, influencing suppressive cell function and the release of endogenous molecules into chronically inflamed tissue. Together, these signals encourage several changes, reprogramming cells into a quiescent state, which reflects disease progression to more severe forms, and development of acquired resistance to conventional drugs to treat the disease. These points are discussed in this review.

Expression of CTLA-4 and CD86 Antigens and Epstein-Barr Virus Reactivation in Chronic Lymphocytic Leukemia-Any Link with Known Prognostic Factors?

Simple Summary

Chronic lymphocytic leukemia (CLL) accounts for one-third of all leukemias. The Epstein-Barr virus (EBV) has the ability to transform B-cells into cancer cells. A history of EBV infection increases the chances of acquiring CLL and it worsens the prognosis in CLL. We tried to assess whether EBV affects the course of CLL by deregulating the CTLA-4/CD86 pathway. The expression of CTLA-4 and CD86 on immune cells in patients with CLL has been evaluated and linked to indicators of EBV infection and clinical outcomes. Our studies have shown that anergy, which is expressed by inhibition through the interaction of CTLA-4 and CD86, is an important mechanism leading to the inhibition of the antitumor response and CLL progression.

Abstract

Infection with Epstein-Barr virus (EBV) worsens the prognosis in chronic lymphocytic leukemia (CLL), but the underlying mechanisms are not yet established. We intended to assess whether EBV affects the course of CLL by the deregulation of the CTLA-4/CD86 signaling pathway. We used polymerase chain reaction to measure the load of EBV DNA in the blood of 110 newly diagnosed patients with CLL. The expression of CTLA-4 and CD86 antigen on lymphocytes was assessed with flow cytometry. Additionally, CTLA-4 and CD86 serum concentrations were measured through enzyme-linked immunosorbent assays. Fifty-four percent of the patients had detectable EBV DNA [EBV(+)]. In EBV(+) patients the CTLA-4 and CD86 serum concentrations and their expressions on investigated cell populations were significantly higher than in EBV(−) patients. EBV load correlated positively with unfavorable prognostic markers of CLL and the expression of CTLA-4 on CD3+ lymphocytes (r = 0.5339; p = 0.027) and CD86 on CD19+ cells (r = 0.6950; p < 0.001). During a median follow-up period of 32 months EBV(+) patients were more likely to require treatment or have lymphocyte doubling (p < 0.001). Among EBV(+) but not EBV(−) patients, increased expressions of CTLA-4 lymphocytes were associated with elevated risks of progression. We propose that EBV coinfection may worsen prognosis in CLL patients, partly due to EBV-induced up-regulation of CTLA-4 expression.

Oxidative Stress Promotes Instability of Regulatory T Cells in Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

We investigated the characteristics of regulatory T cells (Tregs), focusing on the relationship between their stability and reactive oxygen species (ROS), in antineutrophil cytoplasmic antibody-associated vasculitis (AAV). Intracellular expressions of effector cytokines, forkhead box protein 3 (FoxP3), ROS, phosphorylated mammalian target of rapamycin (mTOR), and sirtuin 1 (SIRT1) in Tregs from peripheral blood mononuclear cells (PBMCs) of patients with AAV and healthy controls (HC) were analyzed. The alterations in and functional ability of Tregs were compared before and after resveratrol (RVL) treatment of PBMCs in patients with AAV. Significantly higher expressions of interferon (IFN)-γ, interleukin (IL)-17, IL-4, ROS, and phosphorylated mTOR (pho-mTOR) and lower expression of SIRT1 in CD4+CD25+FoxP3+ cells were found in patients with AAV than in the HC. FoxP3 expression in CD4+CD25+ cells and suppressive function of Tregs were significantly lower in patients with AAV than in the HC. Tregs after RVL treatment demonstrated significant decreases in IFN-γ, ROS, and pho-mTOR levels and increases in FoxP3, SIRT1 levels, and functional activity. Conversely, the direct activation of SIRT1 by SRT1720 resulted in decreased FoxP3 expression, with no reduction in ROS levels. The pho-mTOR levels were significantly higher in Tregs after activation by SRT1720 than in those after RVL treatment. This study suggested that imbalanced changes in Tregs could be attributed to mTOR activation, in which ROS overproduction was predominantly implicated. Therefore, ROS is a key mediator for promoting Tregs instability in AAV.

The foundations of immune checkpoint blockade and the ipilimumab approval decennial

Cancer immunity, and the potential for cancer immunotherapy, have been topics of scientific discussion and experimentation for over a hundred years. Several successful cancer immunotherapies - such as IL-2 and interferon-α (IFNα) - have appeared over the past 30 years. However, it is only in the past decade that immunotherapy has made a broad impact on patient survival in multiple high-incidence cancer indications. The emergence of immunotherapy as a new pillar of cancer treatment (adding to surgery, radiation, chemotherapy and targeted therapies) is due to the success of immune checkpoint blockade (ICB) drugs, the first of which - ipilimumab - was approved in 2011. ICB drugs block receptors and ligands involved in pathways that attenuate T cell activation - such as cytotoxic T lymphocyte antigen 4 (CTLA4), programmed cell death 1 (PD1) and its ligand, PDL1 - and prevent, or reverse, acquired peripheral tolerance to tumour antigens. In this Review we mark the tenth anniversary of the approval of ipilimumab and discuss the foundational scientific history of ICB, together with the history of the discovery, development and elucidation of the mechanism of action of the first generation of drugs targeting the CTLA4 and PD1 pathways.

Advances in Pancreatic Ductal Adenocarcinoma Treatment

Pancreatic Ductal Adenocarcinoma (PDAC) is one of the deadliest malignancies among all cancers. Despite curative intent, surgery and the use of standard cytotoxic chemotherapy and radiation therapy, PDAC remains treatment-resistant. In recent years, more contemporary treatment modalities such as immunotherapy via checkpoint inhibition have shown some promise in many other malignancies, yet PDAC still eludes an effective curative treatment. In investigating these phenomena, research has suggested that the significant desmoplastic and adaptive tumor microenvironment (TME) of PDAC promote the proliferation of immunosuppressive cells and act as major obstacles to treatment efficacy. In this review, we explore challenges associated with the treatment of PDAC, including its unique immunosuppressive TME. This review examines the role of surgery in PDAC, recent advances in surgical approaches and surgical optimization. We further focus on advances in immunotherapeutic approaches, including checkpoint inhibition, CD40 agonists, and discuss promising immune-based future strategies, such as therapeutic neoantigen cancer vaccines as means of overcoming the resistance mechanisms which underly the dense stroma and immune milieu of PDAC. We also explore unique signaling, TME and stromal targeting via novel small molecule inhibitors, which target KRAS, FAK, CCR2/CCR5, CXCR4, PARP and cancer-associated fibroblasts. This review also explores the most promising strategy for advancement in treatment of pancreatic cancer by reviewing contemporary combinatorial approaches in efforts to overcome the treatment refractory nature of PDAC.

Unraveling the Role of Immune Checkpoints in Leishmaniasis

Leishmaniasis are Neglected Tropical Diseases affecting millions of people every year in at least 98 countries and is one of the major unsolved world health issues. Leishmania is a parasitic protozoa which are transmitted by infected sandflies and in the host they mainly infect macrophages. Immunity elicited against those parasites is complex and immune checkpoints play a key role regulating its function. T cell receptors and their respective ligands, such as PD-1, CTLA-4, CD200, CD40, OX40, HVEM, LIGHT, 2B4 and TIM-3 have been characterized for their role in regulating adaptive immunity against different pathogens. However, the exact role those receptors perform during Leishmania infections remains to be better determined. This article addresses the key role immune checkpoints play during Leishmania infections, the limiting factors and translational implications.

Heterodimeric IL-15 in Cancer Immunotherapy

Simple Summary

The rapidly expanding field of cancer immunotherapy uses diverse technologies, including cytokines, T cells, and antibody administration, with the aim to induce effective immune responses leading to tumor control. Interleukin-15 (IL-15), a cytokine discovered in 1994, supports the homeostasis of cytotoxic immune cells and shows promise as an anti-tumor agent. Many studies have elucidated IL-15 synthesis, regulation and biological function and explored its therapeutic efficacy in preclinical cancer models. Escherichia coli-derived single-chain IL-15 was tested in the first in-human trial in cancer patients. Its effects were limited by the biology of IL-15, which in vivo comprises a complex of the IL-15 chain with the IL-15 receptor alpha (IL-15Rα) chain, together forming the IL-15 heterodimer (hetIL-15). Currently, single-chain IL-15 and several heterodimeric IL-15:IL-15Rα variants (hetIL-15, N-803 and RLI) are being tested in clinical trials. This review presents a summary of contemporary preclinical and clinical research on IL-15.

Abstract

Immunotherapy has emerged as a valuable strategy for the treatment of many cancer types. Interleukin-15 (IL-15) promotes the growth and function of cytotoxic CD8⁺ T and natural killer (NK) cells. It also enhances leukocyte trafficking and stimulates tumor-infiltrating lymphocytes expansion and activity. Bioactive IL-15 is produced in the body as a heterodimeric cytokine, comprising the IL-15 and the so-called IL-15 receptor alpha chain that are together termed “heterodimeric IL-15” (hetIL-15). hetIL-15, closely resembling the natural form of the cytokine produced in vivo, and IL-15:IL-15Rα complex variants, such as hetIL-15Fc, N-803 and RLI, are the currently available IL-15 agents. These molecules have showed favorable pharmacokinetics and biological function in vivo in comparison to single-chain recombinant IL-15. Preclinical animal studies have supported their anti-tumor activity, suggesting IL-15 as a general method to convert “cold” tumors into “hot”, by promoting tumor lymphocyte infiltration. In clinical trials, IL-15-based therapies are overall well-tolerated and result in the expansion and activation of NK and memory CD8⁺ T cells. Combinations with other immunotherapies are being investigated to improve the anti-tumor efficacy of IL-15 agents in the clinic.

Immune Checkpoints in Viral Infections

As evidence has mounted that virus-infected cells, such as cancer cells, negatively regulate the function of T-cells via immune checkpoints, it has become increasingly clear that viral infections similarly exploit immune checkpoints as an immune system escape mechanism. Although immune checkpoint therapy has been successfully used in cancer treatment, numerous studies have suggested that such therapy may also be highly relevant for treating viral infection, especially chronic viral infections. However, it has not yet been applied in this manner. Here, we reviewed recent findings regarding immune checkpoints in viral infections, including COVID-19, and discussed the role of immune checkpoints in different viral infections, as well as the potential for applying immune checkpoint blockades as antiviral therapy.

Immune Checkpoint Inhibitors in Hepatocellular Cancer: Current Understanding on Mechanisms of Resistance and Biomarkers of Response to Treatment

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy worldwide and a leading cause of death worldwide. Its incidence continues to increase in the US due to hepatitis C infection and nonalcoholic steatohepatitis. Liver transplantation and resection remain the best therapeutic options for cure, but these are limited by the shortage of available organs for transplantation, diagnosis at advanced stage, and underlying chronic liver disease found in most patients with HCC. Immune checkpoint inhibitors (ICIs) have been shown to be an evolving novel treatment option in certain advanced solid tumors and have been recently approved for inoperable, advanced, and metastatic HCC. Unfortunately, a large cohort of patients with HCC fail to respond to immunotherapy. In this review, we discuss the ICIs currently approved for HCC treatment and their various mechanisms of action. We will highlight current understanding of mechanism of resistance and limitations to ICIs. Finally, we will describe emerging biomarkers of response to ICIs and address future direction on overcoming resistance to immune checkpoint therapy.

Immune checkpoint signaling and cancer immunotherapy

Immune checkpoint blockade therapy has become a major weapon in fighting cancer. Antibody drugs, such as anti-PD-1 and anti-PD-L1, demonstrate obvious advantages such as broad applicability across cancer types and durable clinical response when treatment is effective. However, the overall response rates are still unsatisfying, especially for cancers with low mutational burden. Moreover, adverse effects, such as autoimmune symptoms and tumor hyperprogression, present a significant downside in some clinical applications. These challenges reflect the urgent need to fully understand the basic biology of immune checkpoints. In this review, we discuss regulation of immune checkpoint signaling at multiple levels to provide an overview of our current understanding of checkpoint biology. Topics include the regulation of surface expression levels for known immune checkpoint proteins via surface delivery, internalization, recycling, and degradation. Upon reaching the surface, checkpoints engage in both conventional trans and also cis interactions with ligands to induce signaling and regulate immune responses. Novel therapeutic strategies targeting these pathways in addition to classical checkpoint blockade have recently emerged and been tested in preclinical models, providing new avenues for developing next-generation immunotherapies.

CAMPANELLIProgrammed Death 1 (PD-1) and PD-1 Ligand (PD-L1) Expression in Chronic Apical Periodontitis

Objective:

This study aimed to examine programmed death protein 1 (PD-1) and programmed death lig-and 1 (PD-L1) expression on leukocytes from chronic apical periodontitis, and to determine the levels of cytokines in the apical periodontitis lesions.

Methods:

Leukocytes from healthy gingival tissue (n=16) and chronic apical periodontitis (n=10) were eval-uated using flow cytometry. The PD-1 and PDL-1 expressions were evaluated using flow cytometry. The cy-tokine levels were evaluated by enzyme-linked immunosorbent assay. Data were analyzed using one-way ANOVA. The statistical significance level was set at P<0.05.

Results:

Results showed that the apical periodontitis lesions are more infiltrated by PD-1⁺ and PDL1⁺ lym-phocytes than the control samples. In addition, the PDL-1 expression was detected on macrophages in the apical periodontitis lesions, and was significantly higher compared to leukocytes from healthy gingival tis-sue. The IFN-γ, TGF-β, IL-10, and TNF-α levels were significantly higher in the apical periodontitis lesions com-pared to control samples.

Conclusion:

The PD-1, PD-L1, and CTLA-4 molecules are evident in apical periodontitis, and can be an impor-tant immune checkpoint in chronic periapical periodontitis.

What did we learn from CTLA-4 insufficiency on the human immune system?

Cytotoxic-T-lymphocyte-antigen-4 (CTLA-4) is a negative immune regulator constitutively expressed on regulatory T (Treg) cells and upregulated on activated T cells. CTLA-4 inhibits T cell activation by various suppressive functions including competition with CD28, regulation of the inhibitory function of Treg cells, such as transendocytosis, and the control of adhesion and motility. Intrinsic CTLA-4 signaling has been controversially discussed, but so far no distinct signaling pathway has been identified. The CTLA-4-mediated Treg suppression plays an important role in the maintenance of peripheral tolerance and the prevention of autoimmune diseases. Human CTLA-4 insufficiency is caused by heterozygous germline mutations in CTLA4 and characterized by a complex immune dysregulation syndrome. Clinical studies on CTLA4 mutation carriers showed a reduced penetrance and variable expressivity, suggesting modifying factor(s). One hundred and forty-eight CTLA4 mutation carriers have been reported; patients showed hypogammaglobulinemia, recurrent infectious diseases, various autoimmune diseases, and lymphocytic infiltration into multiple organs. The CTLA-4 expression level in Treg cells was reduced, while the frequency of Treg cells was increased in CTLA-4-insufficient patients. The transendocytosis assay is a specific functional test for the assessment of newly identified CTLA4 gene variants. Immunoglobulin substitution, corticosteroids, immunosuppressive therapy, and targeted therapy such as with CTLA-4 fusion proteins and mechanistic target of rapamycin (mTOR) inhibitors were applied; patients with life-threatening, treatment-resistant symptoms underwent hematopoietic stem cell transplantation. The fact that in humans CTLA-4 insufficiency causes severe disease taught us that the amount of CTLA-4 molecules present in/on T cells matters for immune homeostasis. However, whether the pathology-causing activated T lymphocytes in CTLA-4-insufficient patients are antigen-specific is an unsolved question. CTLA-4, in addition, has a role in autoimmune diseases and cancer. Anti-CTLA-4 drugs are employed as checkpoint inhibitors to target various forms of cancer. Thus, clinical research on human CTLA-4 insufficiency might provide us a deeper understanding of the mechanism(s) of the CTLA-4 molecule and immune dysregulation disorders.

Induction of co-inhibitory molecule CTLA-4 by human papillomavirus E7 protein through downregulation of histone methyltransferase JHDM1B expression

Human papillomavirus causes various skin diseases and even cancer. Unfortunately, the host immune system often fails to generate effective responses against HPV infection due to the ability of HPV to evade immune-mediated eradication, although the detailed mechanisms by which HPV inhibits host antiviral immunity are not fully understood. In this study, we reported a novel role of HPV E7 oncoprotein in inducing the expression of co-inhibitory molecule cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) in cells of epithelial origin. Mechanistically, HPV E7 protein downregulated the cellular abundance of Jumonji C histone demethylase 1B (JHDM1B), increasing the levels of H3K36 methylation within the promoter region of CTLA-4. Our findings expand the current understanding of HPV-mediated immune evasion mechanisms and may be helpful in developing optimal anti-HPV therapeutic strategies and relevant drugs.

Osteoclasts Provide Coupling Signals to Osteoblast Lineage Cells Through Multiple Mechanisms

Bone remodeling is essential for the repair and replacement of damaged and old bone. The major principle underlying this process is that osteoclast-mediated resorption of a quantum of bone is followed by osteoblast precursor recruitment; these cells differentiate to matrix-producing osteoblasts, which form new bone to replace what was resorbed. Evidence from osteopetrotic syndromes indicate that osteoclasts not only resorb bone, but also provide signals to promote bone formation. Osteoclasts act upon osteoblast lineage cells throughout their differentiation by facilitating growth factor release from resorbed matrix, producing secreted proteins and microvesicles, and expressing membrane-bound factors. These multiple mechanisms mediate the coupling of bone formation to resorption in remodeling. Additional interactions of osteoclasts with osteoblast lineage cells, including interactions with canopy and reversal cells, are required to achieve coordination between bone formation and resorption during bone remodeling.

Immunomodulatory Bonds of the Partnership between Dendritic Cells and T Cells

By acquiring, processing, and presenting both foreign and self-antigens, dendritic cells (DCs) initiate T cell activation that is shaped through the immunomodulatory functions of a variety of cell-membrane-bound molecules including BTLA-HVEM, CD40-CD40L, CTLA-4-CD80/CD86, CD70-CD27, ICOS-ICOS-L, OX40-OX40L, and PD-L1-PD-1, as well as several key cytokines and enzymes such as interleukin-6 (IL-6), IL-12, IL-23, IL-27, transforming growth factor-beta 1 (TGF-β1), retinaldehyde dehydrogenase (Raldh), and indoleamine 2,3-dioxygenase (IDO). Some of these distinct immunomodulatory signals are mediated by specific subsets of DCs, therefore contributing to the functional specialization of DCs in the priming and regulation of immune responses. In addition to responding to the DC-mediated signals, T cells can reciprocally modulate the immunomodulatory capacities of DCs, further refining immune responses. Here, we review recent studies, particularly in experimental mouse systems, that have delineated the integrated mechanisms of crucial immunomodulatory pathways that enable specific populations of DCs and T cells to work intimately together as single functional units that are indispensable for the maintenance of immune homeostasis.

Engineered Dendritic Cell-Directed Concurrent Activation of Multiple T cell Inhibitory Pathways Induces Robust Immune Tolerance

Inhibitory/repressor-receptors are upregulated significantly on activated T cells, and have been the molecules of attention as targets for inducing immune tolerance. Induction of effective antigen specific tolerance depends on concurrent engagement of the TCR and one or more of these inhibitory receptors. Here, we show, for the first time that dendritic cells (DCs) can be efficiently engineered to express multiple T cell inhibitory ligands, and enhanced engagement of T cell inhibitory receptors, upon antigen presentation, by these DCs can induce effective CD4+ T cell tolerance and suppress autoimmunity. Compared to control DCs, antigen presentation by DCs that ectopically express CTLA4, PD1 and BTLA selective ligands (B7.1wa, PD-L1, and HVEM-CRD1 respectively) individually (mono-ligand DCs) or in combination (multi-ligand DCs) causes an inhibition of CD4+ T cell proliferation and pro-inflammatory cytokine response, as well as increase in Foxp3+ Treg frequency and immune regulatory cytokine production. Administration of self-antigen (mouse thyroglobulin; mTg) loaded multi-ligand DCs caused hyporesponsiveness to mTg challenge, suppression of autoantibody production, and amelioration of experimental autoimmune thyroiditis. Overall, this study shows that engineered DC-directed enhanced concurrent activation of multiple T cell coinhibitory pathways is an effective way to induce self-antigen specific T cell tolerance to suppress ongoing autoimmunity.

From immune checkpoints to vaccines: The past, present and future of cancer immunotherapy

Cancer is a worldwide medical problem with significant repercussions on individual patients and societies as a whole. In order to alter the outcomes of this deadly disease the treatment of cancer over the centuries has undergone a unique evolution. However, utilizing the best treatment modalities and achieving cures or long-term durable responses have been inconsistent and limited, that is until recently. Contemporary research has highlighted a fundamental gap in our understanding of how we approach treating cancer, by revealing the intricate relationship between the immune system and tumors. In this atmosphere, the growth of immunotherapy has not only forever changed our understanding of cancer biology, but the manner by which we treat patients. It's paradigm shifting success has led to the approval of over 10 different immunotherapeutic agents, including checkpoint inhibitors, vaccine-based therapies, oncolytic viruses and T cell directed therapies for nearly 20 different indications across countless tumor types. Despite the breakthroughs that have occurred in the field of immunotherapy, it has not been the panacea for all cancers. With a deeper understanding of the immune system we have been able to peer into tumor immune escape and therapy resistance. Simultaneously this understanding has paved the way for the investigation and development of novel immune system altering agents and combinatorial therapies. In this chapter we review the immune system and its intricate relationship with cancer, the evolution of immunotherapy, its current landscape, and future directions in the context of resistance mechanisms and the challenges faced by immunotherapy against cancer.

Characterization of Plasmodium berghei Homologues of T-cell Immunomodulatory Protein as a New Potential Candidate for Protecting against Experimental Cerebral Malaria

The pathogenesis of cerebral malaria is biologically complex and involves multi-factorial mechanisms such as microvascular congestion, immunopathology by the pro-inflammatory cytokine and endothelial dysfunction. Recent data have suggested that a pleiotropic T-cell immunomodulatory protein (TIP) could effectively mediate inflammatory cytokines of mammalian immune response against acute graft-versus-host disease in animal models. In this study, we identified a conserved homologue of TIP in Plasmodium berghei (PbTIP) as a membrane protein in Plasmodium asexual stage. Compared with PBS control group, the pathology of experimental cerebral malaria (ECM) in rPbTIP intravenous injection (i.v.) group was alleviated by the downregulation of pro-inflammatory responses, and rPbTIP i.v. group elicited an expansion of regulatory T-cell response. Therefore, rPbTIP i.v. group displayed less severe brain pathology and feverish mice in rPbTIP i.v. group died from ECM. This study suggested that PbTIP may be a novel promising target to alleviate the severity of ECM.

CTLA‑4 interferes with the HBV‑specific T cell immune response (Review)

Hepatitis B virus (HBV) infection is a major cause of hepatic inflammation. Successful HBV clearance in patients is associated with sustained viral control by effector T cells. Compared with acute hepatitis B, chronic HBV infection is associated with the depletion of T cells, resulting in weak or absent virus-specific T cells reactivity, which is described as 'exhaustion'. This exhaustion is characterized by impaired cytokine production and sustained expression of multiple coinhibitory molecules. Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) is one of many coinhibitory molecules that can attenuate T cell activation by inhibiting costimulation and transmitting inhibitory signals to T cells. Persistent HBV infection results in the upregulation of CTLA-4 on hepatic CD8⁺ T cells. This prompts CD8⁺ T cell apoptosis, and the activation of cytotoxic T lymphocytes is blocked. Similar to CD8⁺ T cells, CD4⁺ T helper (Th) cell proliferation is hindered following CTLA-4 upregulation. In addition, the differentiation of CD4⁺ Th is polarized toward the Th2/peripherally-inducible T regulatory cell types, increasing the levels of anti-inflammatory cytokines. Conversely, the activation of proinflammatory cells (Th1 and follicular helper T) is blocked, and the levels of proinflammatory cytokines decline. This review summarizes the current literature relevant to T cell exhaustion in patients with HBV-related chronic hepatitis, and discusses the roles of CTLA-4 in T cell exhaustion.

The synergic effects of CTLA-4/Foxp3-related genotypes and chromosomal aberrations on the risk of recurrent spontaneous abortion among a Chinese Han population

The current study was aimed to investigate the association of CLTA-4/Foxp3 polymorphisms and chromosomal abnormalities with recurrent spontaneous abortion (RSA) risk in a Chinese Han population. Altogether, 1284 RSA women and 1046 women with normal pregnancy were incorporated in this study. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was implemented to genotype the single-nucleotide polymorphisms (SNPs) located within CTLA4 and Foxp3. Moreover, the cytogenetic diagnosis was performed in line with the standards of G banding karyotype. As a consequence, rs231775 and rs3087243 of CTLA4, as well as rs2232365 and rs2232368 of Foxp3, all appeared to modify the risk of RSA. Besides, significant differences were found between the ratio of structural abnormality and that of numerical abnormality (P < 0.038), and chromosome abnormality was associated with higher miscarriage frequency (>3) than normal karyotypes. Of note, the synergic effects of the genotypes and chromosomal abnormality all tallied with the sub-multiplication model (ORchromosome × ORSNP > ORchromosome+SNP), while rs2232365 GG and chromosomal aberration impacted the RSA risk in a super-multiplicative way that ORchromosome × ORSNP < ORchromosome+SNP. In conclusion, susceptibility to RSA was subject to the synthetic regulation of chromosomal aberrations and genetic mutations within CLTA-4 and Foxp3, suggesting that the conduction of karyotype analysis and genetic detection for RSA patients could effectively guide effective RSA counseling and sound child rearing.

T Cell Calcium Signaling Regulation by the Co-Receptor CD5

Calcium influx is critical for T cell effector function and fate. T cells are activated when T cell receptors (TCRs) engage peptides presented by antigen-presenting cells (APC), causing an increase of intracellular calcium (Ca2+) concentration. Co-receptors stabilize interactions between the TCR and its ligand, the peptide-major histocompatibility complex (pMHC), and enhance Ca2+ signaling and T cell activation. Conversely, some co-receptors can dampen Ca2+ signaling and inhibit T cell activation. Immune checkpoint therapies block inhibitory co-receptors, such as cytotoxic T-lymphocyte associated antigen 4 (CTLA-4) and programmed death 1 (PD-1), to increase T cell Ca2+ signaling and promote T cell survival. Similar to CTLA-4 and PD-1, the co-receptor CD5 has been known to act as a negative regulator of T cell activation and to alter Ca2+ signaling and T cell function. Though much is known about the role of CD5 in B cells, recent research has expanded our understanding of CD5 function in T cells. Here we review these recent findings and discuss how our improved understanding of CD5 Ca2+ signaling regulation could be useful for basic and clinical research.

Lymphatic endothelial cells attenuate inflammation via suppression of dendritic cell maturation

Vascular endothelial growth factor-C (VEGF-C)-induced lymphangiogenesis and increased tissue drainage have been reported to inhibit acute and chronic inflammation, and an activated lymphatic endothelium might mediate peripheral tolerance. Using transgenic mice overexpressing VEGF-C in the skin, we found that under inflammatory conditions, VEGF-C-mediated expansion of the cutaneous lymphatic network establishes an immune-inhibitory microenvironment characterised by increased regulatory T (Treg) cells, immature CD11c+CD11b+ dendritic cells (DCs) and CD8+ cells exhibiting decreased effector function. Strikingly, lymphatic endothelial cell (LEC)-conditioned media (CM) potently suppress DC maturation with reduced expression of MHCII, CD40, and IL-6, and increased IL-10 and CCL2 expression. We identify an imbalance in prostaglandin synthase expression after LEC activation, favoring anti-inflammatory prostacyclin synthesis. Importantly, blockade of LEC prostaglandin synthesis partially restores DC maturity. LECs also produce TGF-ß1, contributing to the immune-inhibitory microenvironment. This study identifies novel mechanisms by which the lymphatic endothelium modulates cellular immune responses to limit inflammation.

Integration of radiation and immunotherapy in breast cancer - Treatment implications

Radiation therapy (RT) has been successfully used in the treatment of breast cancer (BC) for over a century. While historically thought to be immunosuppressive, new data have shown that RT can work together with the immune system to eliminate cancer. It can cause immunogenic cell death and facilitate tumor neoantigen presentation and cross-priming of tumor-specific T-lymphocytes, turning irradiated tumor into an in-situ vaccine. Unfortunately, due to various immune escape mechanism put in place by the tumor, RT alone rarely results in a systemic response of metastatic disease sites (known as the abscopal effect). Immunotherapy, a series of agents designed to stimulate the immune system in order to generate tumor-specific immune response, is showing promise in treatment of various cancers, including BC, and can be an ideal complement to RT in stimulating a systemic immune response to reject the tumor cells. This review discusses the mechanisms in which RT can trigger an immune response for tumor rejection, and provide emerging preclinical and clinical data of combination immunoradiotherapy, and its potential in treating BC.

Regulatory T Cell-Mediated Tissue Repair

Regulatory T-cells (Treg cells) are a specific group of T-cells that maintain immune homeostasis by counteracting the immune responses of conventional T-cells. So far, the therapeutic applications of Treg cells have focused on the treatment of autoimmune diseases, as depletion of Treg cells or Treg-related genes is known to cause autoimmune defects. However, Treg cells can be a potential solution for tissue repair as they can terminate the pro-inflammatory phase and initiate the anti-inflammatory or regenerative phase at the tissue injury site. This review summarizes the known characteristics of Treg cells and lists examples of their therapeutic applications. The use of Treg cells in the treatment of myocardial infarctions, skeletal muscle injuries, and ischemia injuries has revealed their potential as a promising tissue repair method. We have also discussed the limitations and scope of Treg cells in tissue repair.

Immunomodulatory Drugs: Immune Checkpoint Agents in Acute Leukemia

Intrinsic immune responses to acute leukemia are inhibited by a variety of mechanisms, such as aberrant antigen expression by leukemia cells, secretion of immunosuppressive cytokines and expression of inhibitory enzymes in the tumor microenvironment, expansion of immunoregulatory cells, and activation of immune checkpoint pathways, all leading to T cell dysfunction and/or exhaustion. Leukemic cells, similar to other tumor cells, hijack these inhibitory pathways to evade immune recognition and destruction by cytotoxic T lymphocytes. Thus, blockade of immune checkpoints has emerged as a highly promising approach to augment innate anti-tumor immunity in order to treat malignancies. Most evidence for the clinical efficacy of this immunotherapeutic strategy has been seen in patients with metastatic melanoma, where anti-CTLA-4 and anti-PD-1 antibodies have recently revolutionized treatment of this lethal disease with otherwise limited treatment options. To meet the high demand for new treatment strategies in acute leukemia, clinical testing of these promising therapies is commencing. Herein, we review the biology of multiple inhibitory checkpoints (including CTLA-4, PD-1, TIM-3, LAG-3, BTLA, and CD200R) and their contribution to immune evasion by acute leukemias. In addition, we discuss the current state of preclinical and clinical studies of immune checkpoint inhibition in acute leukemia, which seek to harness the body's own immune system to fight leukemic cells.

The Yin and Yang of regulatory T cell and therapy progress in autoimmune disease

Autoimmune diseases (ADs) are primarily mediated by the failure of immunological self-tolerance. Regulatory T cells (Tregs) play a critical role in the maintenance of induced tolerance to peripheral self-antigens, suppressing immoderate immune responses deleterious to the host and preventing the AD development. Tregs and suppressive cytokines are homeostatic with effective cells plus pro-inflammatory cytokines in healthy hosts which is defined as "Yang", and ADs are usually induced in case of disturbed homeostasis, which is defined as "Yin". Indeed, the Yin-Yang balance could explain the pathogenic mechanism of ADs. Tregs not only suppress CD4⁺ and CD8⁺ T cells but also can suppress other immune cells such as B cell, natural killer cell, DC and other antigen-presenting cell through cell-cell contact or secreting suppressive cytokines. In Tregs, Foxp3 as an intracellular protein displays a more specific marker than currently used other cell-surface markers (such as CD25, CD40L, CTLA-4, ICOS and GITR) in defining the naturally occurring CD4⁺ Tregs. Though the precise mechanism for the opposite effects of Tregs has not been fully elucidated, the importance of Tregs in ADs has been proved to be associated with kinds of immunocytes. At present, the surface marker, frequency and function of Tregs existed conflicts and hence the Tregs therapy in ADs faces challenges. Though some success has been achieved with Tregs therapy in few ADs both in murine models and humans, more effort should paid to meet the future challenges. This review summarizes the progress and discusses the phenotypic, numeric and functional abnormalities of Tregs and is the first time to systematically review the progress of Tregs therapy in kinds of ADs.

Challenges and opportunities in targeting the CD28/CTLA-4 pathway in transplantation and autoimmunity

INTRODUCTION

T cell activation is a complex process that requires multiple cell signaling pathways, including a primary recognition signal and additional costimulatory signals. One of the best-characterized costimulatory pathways includes the Ig superfamily members CD28 and CTLA-4 and their ligands CD80 and CD86. Areas covered: This review discusses past, current and future biological therapies that have been utilized to block the CD28/CTLA-4 cosignaling pathway in the settings of autoimmunity and transplantation, as well the challenges facing successful implementation of these therapies. Expert opinion: The development of CD28 blockers Abatacept and Belatacept provided a more targeted therapy approach for transplant rejection and autoimmune disease relative to calcineurin inhibitors and anti-proliferatives, but overall efficacy may be limited due to their collateral effect of simultaneously blocking CTLA-4 coinhibitory signals. As such, current investigations into the potential of selective CD28 blockade to block the costimulatory potential of CD28 while exploiting the coinhibitory effects of CTLA-4 are promising. However, as selective CD28 blockade inhibits the activity of both effector and regulatory T cells, an important goal for the future is the design of therapies that will maximize the attenuation of effector responses while preserving the suppressive function of T regulatory cells.

Disturbed Th17/Treg Balance in Patients with Non-small Cell Lung Cancer

The fine balance of T help-17 (Th17)/regulatory T(Treg) cells is crucial for maintenance of immune homeostasis. However, there is little information concerning the role played in non-small cell lung cancer (NSCLC) by Th17/Treg cells. The objective of this study was to investigate the variation of Th17 and Treg cells in the peripheral blood of patients with NSCLC. Blood samples were collected from 19 patients with NSCLC and 19 healthy donors. Samples were processed to detect CD4(+)IL-17(+) Th17 cells and CD4(+)CD25(+)Foxp3(+) Treg cells by flow cytometry, and related gene expressions were assessed by real-time quantitative polymerase chain reaction. The concentrations of interleukin (IL)-1β, IL-6, IL-10, IL-17, IL-23, and transforming growth factor-beta (TGF-β1) were also measured by enzyme-linked immunosorbent assay analysis (ELISA). The frequency of circulating Th17 cells and Treg cells was increased in samples derived from patients with NSCLC, accompanied by the upregulation of Foxp3 and RORγt. However, a negative correlation between Treg cells and Th17 cells was found in patients with NSCLC. Additionally, the Th17/Treg ratio and the related cytokines were also significantly higher in patients with NSCLC than in healthy controls. Furthermore, the frequency of Th17 cells was positively correlated with IL-1β, IL-6, and IL-23 in patients with NSCLC, and the frequency of Treg cells was positively correlated with TGF-β1 and IL-10. More importantly, the Th17/Treg ratio was positively correlated with the CEA concentrations in patients with NSCLC. Our data indicated that Th17 and Treg subset are involved in the immunopathology of NSCLC. Distinct cytokine environment might play a key role in the differentiation of the Th17 and Treg cells in NSCLC. Reconstituting an adequate balance between Th17 and Treg may be beneficial in the treatment of NSCLC.

Anti-CD28 Antibody and Belatacept Exert Differential Effects on Mechanisms of Renal Allograft Rejection

Belatacept is a biologic that targets CD80/86 and prevents its interaction with CD28 and its alternative ligand, cytotoxic T lymphocyte antigen 4 (CTLA-4). Clinical experience in kidney transplantation has revealed a high incidence of rejection with belatacept, especially with intensive regimens, suggesting that blocking CTLA-4 is deleterious. We performed a head to head assessment of FR104 (n=5), a selective pegylated Fab' antibody fragment antagonist of CD28 that does not block the CTLA-4 pathway, and belatacept (n=5) in kidney allotransplantation in baboons. The biologics were supplemented with an initial 1-month treatment with low-dose tacrolimus. In cases of acute rejection, animals also received steroids. In the belatacept group, four of five recipients developed severe, steroid-resistant acute cellular rejection, whereas FR104-treated animals did not. Assessment of regulatory T cell-specific demethylated region methylation status in 1-month biopsy samples revealed a nonsignificant trend for higher regulatory T cell frequencies in FR104-treated animals. Transcriptional analysis did not reveal significant differences in Th17 cytokines but did reveal higher levels of IL-21, the main cytokine secreted by CD4 T follicular helper (Tfh) cells, in belatacept-treated animals. In vitro, FR104 controlled the proliferative response of human preexisting Tfh cells more efficiently than belatacept. In mice, selective CD28 blockade also controlled Tfh memory cell responses to KLH stimulation more efficiently than CD80/86 blockade. Our data reveal that selective CD28 blockade and belatacept exert different effects on mechanisms of renal allograft rejection, particularly at the level of Tfh cell stimulation.

Antibody-Mediated Phosphatidylserine Blockade Enhances the Antitumor Responses to CTLA-4 and PD-1 Antibodies in Melanoma

In tumor-bearing animals, the membrane phospholipid phosphatidylserine (PS) suppresses immune responses, suggesting that PS signaling could counteract the antitumor effect of antibody-driven immune checkpoint blockade. Here, we show that treating melanoma-bearing mice with a PS-targeting antibody enhances the antitumor activity of downstream checkpoint inhibition. Combining PS-targeting antibodies with CTLA-4 or PD-1 blockade resulted in significantly greater inhibition of tumor growth than did single-agent therapy. Moreover, combination therapy enhanced CD4(+) and CD8(+) tumor-infiltrating lymphocyte numbers; elevated the fraction of cells expressing the proinflammatory cytokines IL2, IFNγ, and TNFα; and increased the ratio of CD8 T cells to myeloid-derived suppressor cells and regulatory T cells in tumors. Similar changes in immune cell profiles were observed in splenocytes. Taken together, these data show that antibody-mediated PS blockade enhances the antitumor efficacy of immune checkpoint inhibition. Cancer Immunol Res; 4(6); 531-40. ©2016 AACR.

Novel immunotherapeutic approaches for the treatment of acute leukemia (myeloid and lymphoblastic)

There have been major advances in our understanding of the multiple interactions between malignant cells and the innate and adaptive immune system. While the attention of immunologists has hitherto focused on solid tumors, the specific immunobiology of acute leukemias is now becoming defined. These discoveries have pointed the way to immune interventions building on the established graft-versus-leukemia (GVL) effect from hematopoietic stem-cell transplant (HSCT) and extending immunotherapy beyond HSCT to individuals with acute leukemia with a diversity of immune manipulations early in the course of the leukemia. At present, clinical results are in their infancy. In the coming years larger studies will better define the place of immunotherapy in the management of acute leukemias and lead to treatment approaches that combine conventional chemotherapy, immunotherapy and HSCT to achieve durable cures.

Innovative perspectives of immunotherapy in head and neck cancer. From relevant scientific rationale to effective clinical practice

It is now well established that head and neck cancer carcinogenesis is characterized by genetic instability and several immune defects, leading to unique host-tumor interactions. In such condition, recent improved comprehension and relevant findings could lead to identification of innovative molecular therapeutic targets, achieving considerable clinical and translational research. This review aims to summarize and to highlight most recent and relevant scientific rationale in this era of immunotherapy revival, and to correlate it to the near future clinical practice for the management of this challenging disease.

In situ vaccination by radiotherapy to improve responses to anti-CTLA-4 treatment

Targeting immune checkpoint receptors has emerged as an effective strategy to induce immune-mediated cancer regression in the subset of patients who have significant pre-existing anti-tumor immunity. For the remainder, effective anti tumor responses may require vaccination. Radiotherapy, traditionally used to achieve local tumor control, has acquired a new role, that of a partner for immunotherapy. Ionizing radiation has pro-inflammatory effects that facilitate tumor rejection. Radiation alters the tumor to enhance the concentration of effector T cells via induction of chemokines, cytokines and adhesion molecules. In parallel, radiation can induce an immunogenic death of cancer cells, promoting cross-presentation of tumor-derived antigens by dendritic cells to T cells. Newly generated anti-tumor immune responses have been demonstrated post-radiation in both murine models and occasional patients, supporting the hypothesis that the irradiated tumor can become an in situ vaccine. It is in this role, that radiation can be applied to induce anti-tumor T cells in lymphocyte-poor tumors, and possibly benefit patients who would otherwise fail to respond to immune checkpoint inhibitors. This review summarizes preclinical and clinical data demonstrating that radiation acts in concert with antibodies targeting the immune checkpoint cytotoxic T-lymphocyte antigen-4 (CTLA-4), to induce therapeutically effective anti-tumor T cell responses in tumors otherwise non responsive to anti-CTLA-4 therapy.

Combination of radiotherapy and immune checkpoint inhibitors

The ability of ionizing radiation to cause cell death and inflammatory reactions has been known since the beginning of its therapeutic use in oncology. However, only recently this property of radiation has attracted the attention of immunologists seeking to induce or improve antitumor immunity. As immune checkpoint inhibitors are becoming mainstream cancer treatments, radiation oncologists have begun to observe unexpected out-of-the-field (abscopal) responses in patients receiving radiation therapy during immunotherapy. These unexpected responses were predicted by experimental work in preclinical tumor models and have clear biological bases. Accumulating experimental evidence that radiation induces an immunogenic cell death and promotes recruitment and function of T cells within the tumor microenvironment supports the hypothesis that radiation can convert the tumor into an in situ individualized vaccine. This property of radiation is key to its synergy with immune checkpoint inhibitors, antibodies targeting inhibitory receptors on T cells such as cytotoxic T lymphocyte antigen-4 and programmed death-1. By removing the obstacles hindering the activation and function of antitumor T cells, these agents benefit patients with pre-existing antitumor immunity but are ineffective in patients lacking these spontaneous responses. Radiation induces antitumor T cells complementing the activity of immune checkpoint inhibitors.

The role of checkpoints in the treatment of GBM

Targeted immunotherapy is founded on the principle that augmentation of effector T cell activity in the tumor microenvironment can translate to tumor regression. Targeted checkpoint inhibitors in the form of agonist or antagonist monoclonal antibodies have come to the fore as a promising strategy to activate systemic immunity and enhance T cell activity by blocking negative signals, enhancing positive signals, or altering the cytokine milieu. This review will examine several immune checkpoints and checkpoint modulators that play a role in cancer pathogenesis, with an emphasis on malignant gliomas.

Anticancer immunotherapy by CTLA-4 blockade: obligatory contribution of IL-2 receptors and negative prognostic impact of soluble CD25

The cytotoxic T lymphocyte antigen-4 (CTLA-4)-blocking antibody ipilimumab induces immune-mediated long-term control of metastatic melanoma in a fraction of patients. Although ipilimumab undoubtedly exerts its therapeutic effects via immunostimulation, thus far clinically useful, immunologically relevant biomarkers that predict treatment efficiency have been elusive. Here, we show that neutralization of IL-2 or blocking the α and β subunits of the IL-2 receptor (CD25 and CD122, respectively) abolished the antitumor effects and the accompanying improvement of the ratio of intratumoral T effector versus regulatory cells (Tregs), which were otherwise induced by CTLA-4 blockade in preclinical mouse models. CTLA-4 blockade led to the reduction of a suppressive CD4(+) T cell subset expressing Lag3, ICOS, IL-10 and Egr2 with a concomitant rise in IL-2-producing effector cells that lost FoxP3 expression and accumulated in regressing tumors. While recombinant IL-2 improved the therapeutic efficacy of CTLA-4 blockade, the decoy IL-2 receptor α (IL-2Rα, sCD25) inhibited the anticancer effects of CTLA-4 blockade. In 262 metastatic melanoma patients receiving ipilimumab, baseline serum concentrations of sCD25 represented an independent indicator of overall survival, with high levels predicting resistance to therapy. Altogether, these results unravel a role for IL-2 and IL-2 receptors in the anticancer activity of CTLA-4 blockade. Importantly, our study provides the first immunologically relevant biomarker, namely elevated serum sCD25, that predicts resistance to CTLA-4 blockade in patients with melanoma.

Immune checkpoint blockade in hepatocellular carcinoma: current progress and future directions

Immune checkpoint blockade has recently emerged as a promising therapeutic approach for various malignancies including hepatocellular carcinoma (HCC). Preclinical and clinical studies have shown the potential benefit of modulating the immunogenicity of HCC. In addition, recent advances in tumor immunology have broadened our understanding of the complex mechanism of immune evasion. In this review we summarize the current knowledge on HCC immunology and discuss the potential of immune checkpoint blockade as a novel HCC therapy from the basic, translational, and clinical perspectives.

The mucosal immune system in the oral cavity-an orchestra of T cell diversity

The mucosal immune system defends against a vast array of pathogens, yet it exhibits limited responses to commensal microorganisms under healthy conditions. The oral-pharyngeal cavity, the gateway for both the gastrointestinal and respiratory tracts, is composed of complex anatomical structures and is constantly challenged by antigens from air and food. The mucosal immune system of the oral-pharyngeal cavity must prevent pathogen entry while maintaining immune homeostasis, which is achieved via a range of mechanisms that are similar or different to those utilized by the gastrointestinal immune system. In this review, we summarize the features of the mucosal immune system, focusing on T cell subsets and their functions. We also discuss our current understanding of the oral-pharyngeal mucosal immune system.

Two functionally distinct myeloid dendritic cell subpopulations are present in bovine blood

Immature myeloid (m)DCs circulating in the blood of cattle have been defined as lineage negative (Lin(-))MHCII(+)CD11c(+)CD205(+) cells. Lin(-)MHCII(+)CD11c(+)CD205(+) mDCs (0.2% blood mononuclear cells) isolated from bovine blood were heterogeneous in cell size and CD205 expression. Using highspeed cell sorting, Lin(-)MHCII(+)CD11c(+)CD205(+) DCs were sorted into CD205(Hi) and CD205(Lo) subpopulations which were phenotypically distinct and differed significantly (P<0.01) in TLR gene expression. CD205(Hi) and CD205(Lo) mDCs were more efficient in macropinocytosis than monocytes and expressed no or little detectable non-specific esterase activity. CD205(Lo) mDCs efficiently activated purified allogeneic T cells and the addition of TLR agonists did not significantly alter this antigen presentation capacity. T cell activation by CD205(Lo) mDCs was associated with differential up-regulation of CD40, CD80, CD86 and TGFβ1 gene expression when compared to CD205(Hi) mDCs. In conclusion, two phenotypically and functionally distinct CD11c(+)CD205(+) mDCs were isolated from blood that had an equal capacity to acquire antigen but markedly different capacities to activate T cells.