Tissue-resident memory T cells populate the human brain

Distinct Effector Programs of Brain-Homing CD8+ T Cells in Multiple Sclerosis

The effector programs of CD8⁺ memory T cells are influenced by the transcription factors RUNX3, EOMES and T-bet. How these factors define brain-homing CD8⁺ memory T cells in multiple sclerosis (MS) remains unknown. To address this, we analyzed blood, CSF and brain tissues from MS patients for the impact of differential RUNX3, EOMES and T-bet expression on CD8⁺ T cell effector phenotypes. The frequencies of RUNX3- and EOMES-, but not T-bet-expressing CD8⁺ memory T cells were reduced in the blood of treatment-naïve MS patients as compared to healthy controls. Such reductions were not seen in MS patients treated with natalizumab (anti-VLA-4 Ab). We found an additional loss of T-bet in RUNX3-expressing cells, which was associated with the presence of MS risk SNP rs6672420 (RUNX3). RUNX3⁺EOMES⁺T-bet⁻ CD8⁺ memory T cells were enriched for the brain residency-associated markers CCR5, granzyme K, CD20 and CD69 and selectively dominated the MS CSF. In MS brain tissues, T-bet coexpression was recovered in CD20^dim and CD69⁺ CD8⁺ T cells, and was accompanied by increased coproduction of granzyme K and B. These results indicate that coexpression of RUNX3 and EOMES, but not T-bet, defines CD8⁺ memory T cells with a pre-existing brain residency-associated phenotype such that they are prone to enter the CNS in MS.

Immune cells impede repair of old neurons

Interfering with age-related neuroimmune interactions promotes nerve regeneration.

Single-cell profiling reveals periventricular CD56bright NK cell accumulation in multiple sclerosis

Multiple sclerosis (MS) is a chronic demyelinating disease characterised by immune cell infiltration resulting in lesions that preferentially affect periventricular areas of the brain. Despite research efforts to define the role of various immune cells in MS pathogenesis, the focus has been on a few immune cell populations while full-spectrum analysis, encompassing others such as natural killer (NK) cells, has not been performed. Here, we used single-cell mass cytometry (CyTOF) to profile the immune landscape of brain periventricular areas - septum and choroid plexus - and of the circulation from donors with MS, dementia and controls without neurological disease. Using a 37-marker panel, we revealed the infiltration of T cells and antibody-secreting cells in periventricular brain regions and identified a novel NK cell signature specific to MS. CD56bright NK cells were accumulated in the septum of MS donors and displayed an activated and migratory phenotype, similar to that of CD56bright NK cells in the circulation. We validated this signature by multiplex immunohistochemistry and found that the number of NK cells with high expression of granzyme K, typical of the CD56bright subset, was increased in both periventricular lesions and the choroid plexus of donors with MS. Together, our multi-tissue single-cell data shows that CD56bright NK cells accumulate in the periventricular brain regions of MS patients, bringing NK cells back to the spotlight of MS pathology.

Proteomics in Multiple Sclerosis: The Perspective of the Clinician

Multiple sclerosis (MS) is the inflammatory demyelinating and neurodegenerative disease of the central nervous system (CNS) that affects approximately 2.8 million people worldwide. In the last decade, a new era was heralded in by a new phenotypic classification, a new diagnostic protocol and the first ever therapeutic guideline, making personalized medicine the aim of MS management. However, despite this great evolution, there are still many aspects of the disease that are unknown and need to be further researched. A hallmark of these research are molecular biomarkers that could help in the diagnosis, differential diagnosis, therapy and prognosis of the disease. Proteomics, a rapidly evolving discipline of molecular biology may fulfill this dire need for the discovery of molecular biomarkers. In this review, we aimed to give a comprehensive summary on the utility of proteomics in the field of MS research. We reviewed the published results of the method in case of the pathogenesis of the disease and for biomarkers of diagnosis, differential diagnosis, conversion of disease courses, disease activity, progression and immunological therapy. We found proteomics to be a highly effective emerging tool that has been providing important findings in the research of MS.

A bioluminescence reporter mouse model for visualizing and quantifying CD8+ T cells in vivo

Cytotoxic CD8+ T cells are the primary effector cells mediating anti-tumor responses. In vivo monitoring of CD8+ T cells has broad implications for the development of novel cancer therapies. Here we describe the development of a genetically engineered mouse model (GEMM) in which CD8+ T cells are labeled with an optical reporter, enabling in vivo, longitudinal monitoring using bioluminescence imaging (BLI). Firefly luciferase (Luc2), human diphtheria toxin receptor (DTR), and enhanced green fluorescence protein (eGFP) cDNAs are engineered under the CD8α promoter to generate a transgenic mouse line. Luciferase mRNA and CD8α mRNA were generally correlated in various tissues from these mice. Sorted splenic CD8+ T cells, CD4+ T cells and CD3- non-T cells verified that the luciferase signal is specific to CD8+ T cells. In vivo imaging showed that luciferase signal was detected in various immune organs, such as lymph nodes, thymus, and spleen, and the detection was confirmed by ex vivo examination. Administration of diphtheria toxin markedly reduced luciferase signal systemically, confirming the function of the DTR. In the MC38 mouse syngeneic model, we observed significant increases in CD8+ T cells with mDX400 treatment, an anti PD-1 mouse monoclonal antibody that correlated with tumor growth inhibition. This novel reporter GEMM is a valuable drug discovery tool for profiling compounds and understanding mechanisms of action in immunotherapy of cancer.

The Role of Immunity in Alzheimer's Disease

With the increase in the aging population, age-related conditions such as dementia and Alzheimer's disease will become ever more prevalent in society. As there is no cure for dementia and extremely limited therapeutic options, researchers are examining the mechanisms that contribute to the progression of cognitive decline in hopes of developing better therapies and even an effective, long-lasting treatment for this devastating condition. This review will provide an updated perspective on the role of immunity in triggering the changes that lead to the development of dementia. It will detail the latest findings on Aβ- and tau-induced microglial activation, including the role of the inflammasome. The contribution of the adaptive immune system, specifically T cells, will be discussed. Finally, whether the innate and adaptive immune system can be modulated to protect against dementia will be examined, along with an assessment of the prospective candidates for these that are currently in clinical trials.

Tissue-resident memory T cells in gastrointestinal cancer immunology and immunotherapy: ready for prime time?

Tissue-resident memory T (T_RM) cells have emerged as immune sentinels that patrol the tissue microenvironment and orchestrate localized antitumor immunity in various solid cancers. Recent studies have revealed that T_RM cells are key players in cancer immunosurveillance, and their involvement has been linked to favorable responses to immunotherapy as well as general better clinical outcome in cancer patients. In this review, we provide an overview of the major advances and recent findings regarding T_RM cells phenotype, transcriptional and epigenetic regulation in cancer with a special focus on gastrointestinal tumors. Finally, we highlight the exciting clinical implication of T_RM cells in these types of tumors.

Characterising Distinct Migratory Profiles of Infiltrating T-Cell Subsets in Human Glioblastoma

Glioblastoma is the most common and aggressive form of primary brain cancer, with no improvements in the 5-year survival rate of 4.6% over the past three decades. T-cell-based immunotherapies such as immune-checkpoint inhibitors and chimeric antigen receptor T-cell therapy have prolonged the survival of patients with other cancers and have undergone early-phase clinical evaluation in glioblastoma patients. However, a major challenge for T-cell-based immunotherapy of glioblastoma and other solid cancers is T-cell infiltration into tumours. This process is mediated by chemokine-chemokine receptor and integrin-adhesion molecule interactions, yet the specific nature of the molecules that may facilitate T-cell homing into glioblastoma are unknown. Here, we have characterised chemokine receptor and integrin expression profiles of endogenous glioblastoma-infiltrating T cells, and the chemokine expression profile of glioblastoma-associated cells, by single-cell RNA-sequencing. Subsequently, chemokine receptors and integrins were validated at the protein level to reveal enrichment of receptors CCR2, CCR5, CXCR3, CXCR4, CXCR6, CD49a, and CD49d in glioblastoma-infiltrating T-cell populations relative to T cells in matched patient peripheral blood. Complementary chemokine ligand expression was then validated in glioblastoma biopsies and glioblastoma-derived primary cell cultures. Together, enriched expression of homing receptor-ligand pairs identified in this study implicate a potential role in mediating T-cell infiltration into glioblastoma. Importantly, our data characterising the migratory receptors on endogenous tumour-infiltrating T cells could be exploited to enhance the tumour-homing properties of future T-cell immunotherapies for glioblastoma.

Tissue-Resident Immune Cells in Humans

Tissue-resident immune cells span both myeloid and lymphoid cell lineages, have been found in multiple human tissues, and play integral roles at all stages of the immune response, from maintaining homeostasis to responding to infectious challenges to resolution of inflammation to tissue repair. In humans, studying immune cells and responses in tissues is challenging, although recent advances in sampling and high-dimensional profiling have provided new insights into the ontogeny, maintenance, and functional role of tissue-resident immune cells. Each tissue contains a specific complement of resident immune cells. Moreover, resident immune cells for each lineage share core properties, along with tissue-specific adaptations. Here we propose a five-point checklist for defining resident immune cell types in humans and describe the currently known features of resident immune cells, their mechanisms of development, and their putative functional roles within various human organs. We also consider these aspects of resident immune cells in the context of future studies and therapeutics.

Tissue-resident CD8+ T cells drive compartmentalized and chronic autoimmune damage against CNS neurons

The mechanisms underlying the chronicity of autoimmune diseases of the central nervous system (CNS) are largely unknown. In particular, it is unclear whether tissue-resident memory T cells (T_RM) contribute to lesion pathogenesis during chronic CNS autoimmunity. Here, we observed that a high frequency of brain-infiltrating CD8⁺ T cells exhibit a T_RM-like phenotype in human autoimmune encephalitis. Using mouse models of neuronal autoimmunity and a combination of T single-cell transcriptomics, high-dimensional flow cytometry, and histopathology, we found that pathogenic CD8⁺ T cells behind the blood-brain barrier adopt a characteristic T_RM differentiation program, and we revealed their phenotypic and functional heterogeneity. In the diseased CNS, autoreactive tissue-resident CD8⁺ T cells sustained focal neuroinflammation and progressive loss of neurons, independently of recirculating CD8⁺ T cells. Consistently, a large fraction of autoreactive tissue-resident CD8⁺ T cells exhibited proliferative potential as well as proinflammatory and cytotoxic properties. Persistence of tissue-resident CD8⁺ T cells in the CNS and their functional output, but not their initial differentiation, were crucially dependent on CD4⁺ T cells. Collectively, our results point to tissue-resident CD8⁺ T cells as essential drivers of chronic CNS autoimmunity and suggest that therapies targeting this compartmentalized autoreactive T cell subset might be effective for treating CNS autoimmune diseases.

Tissue-resident memory CD8+ T cells cooperate with CD4+ T cells to drive compartmentalized immunopathology in the CNS

In chronic inflammatory diseases of the central nervous system (CNS), immune cells persisting behind the blood-brain barrier are supposed to promulgate local tissue destruction. The drivers of such compartmentalized inflammation remain unclear, but tissue-resident memory T cells (T_RM) represent a potentially important cellular player in this process. Here, we investigated whether resting CD8⁺ T_RM persisting after cleared infection with attenuated lymphocytic choriomeningitis virus (LCMV) can initiate immune responses directed against cognate self-antigen in the CNS. We demonstrated that time-delayed conditional expression of the LCMV glycoprotein as neo-self-antigen by glia cells reactivated CD8⁺ T_RM. Subsequently, CD8⁺ T_RM expanded and initiated CNS inflammation and immunopathology in an organ-autonomous manner independently of circulating CD8⁺ T cells. However, in the absence of CD4⁺ T cells, TCF-1⁺ CD8⁺ T_RM failed to expand and differentiate into terminal effectors. Similarly, in human demyelinating CNS autoimmune lesions, we found CD8⁺ T cells expressing TCF-1 that predominantly exhibited a T_RM-like phenotype. Together, our study provides evidence for CD8⁺ T_RM-driven CNS immunopathology and sheds light on why inflammatory processes may evade current immunomodulatory treatments in chronic autoimmune CNS conditions.

Two sides of the same coin: Protective versus pathogenic CD4+ resident memory T cells

The ability of the adaptive immune system to form memory is key to providing protection against secondary infections. Resident memory T cells (T_RM) are specialized T cell populations that reside within tissue sites where they await reencounter with their cognate antigen. T_RM are distinct from circulating memory cells, including central and effector memory T cells, both functionally and transcriptionally. Since the discovery of T_RM, most research has focused on CD8⁺ T_RM, despite that CD4⁺ T_RM are also abundant in most tissues. In the past few years, more evidence has emerged that CD4⁺ T_RM can contribute both protective and pathogenic roles in disease. A complexity inherent to the CD4⁺ T_RM field is the ability of CD4⁺ T cells to polarize into a multitude of distinct subsets and recognize not only viruses and intracellular bacteria but also extracellular bacteria, fungi, and parasites. In this review, we outline the key features of CD4⁺ T_RM in health and disease, including their contributions to protection against SARS-CoV-2 and potential contributions to immunopathology associated with COVID-19.

The meningeal lymphatic vasculature in neuroinflammation

The lymphatic vasculature is a unidirectional network of lymphatic endothelial cells, whose main role is to maintain fluid homeostasis along with the absorption of dietary fat in the gastrointestinal organs and management and coordination of immune cell trafficking into lymph nodes during homeostasis and under inflammatory conditions. In homeostatic conditions, immune cells, such as dendritic cells, macrophages, or T cells can enter into the lymphatic vasculature and move easily through the lymph reaching secondary lymph nodes where immune cell activation or peripheral tolerance can be modulated. However, under inflammatory conditions such as pathogen infection, increased permeabilization of lymphatic vessels allows faster immune cell migration into inflamed tissues following a chemokine gradient, facilitating pathogen clearance and the resolution of inflammation. Interestingly, since the re-discovery of lymphatic vasculature in the central nervous system, known as the meningeal lymphatic vasculature, the role of these lymphatics as a key player in several neurological disorders has been described, with emphasis on the neurodegenerative process. Alternatively, less has been discussed about meningeal lymphatics and its role in neuroinflammation. In this review, we discuss current knowledge about the anatomy and function of the meningeal lymphatic vasculature and specifically analyze its contribution to different neuroinflammatory processes, highlighting the potential therapeutic target of meningeal lymphatic vasculature in these pathological conditions.

Astrocytic junctional adhesion molecule-A regulates T cell entry past the glia limitans to promote central nervous system autoimmune attack

Contact-mediated interactions between the astrocytic endfeet and infiltrating immune cells within the perivascular space are underexplored, yet represent potential regulatory check-points against CNS autoimmune disease and disability. Reactive astrocytes upregulate junctional adhesion molecule-A, an immunoglobulin-like cell surface receptor that binds to T cells via its ligand, the integrin, lymphocyte function-associated antigen-1. Here, we tested the role of astrocytic junctional adhesion molecule-A in regulating CNS autoinflammatory disease. In cell co-cultures, we found that junctional adhesion molecule-A-mediated signalling between astrocytes and T cells increases levels of matrix metalloproteinase-2, C–C motif chemokine ligand 2 and granulocyte-macrophage colony-stimulating factor, pro-inflammatory factors driving lymphocyte entry and pathogenicity in multiple sclerosis and experimental autoimmune encephalomyelitis, an animal model of CNS autoimmune disease. In experimental autoimmune encephalomyelitis, mice with astrocyte-specific JAM-A deletion (mGFAP:CreJAM-A^fl/fl) exhibit decreased levels of matrix metalloproteinase-2, reduced ability of T cells to infiltrate the CNS parenchyma from the perivascular spaces and a milder histopathological and clinical course of disease compared with wild-type controls (JAM-A^fl/fl). Treatment of wild-type mice with intraperitoneal injection of soluble junctional adhesion molecule-A blocking peptide decreases the severity of experimental autoimmune encephalomyelitis, highlighting the potential of contact-mediated astrocyte–immune cell signalling as a novel translational target against neuroinflammatory disease.

Role of the adaptive immune system in diabetic kidney disease

Diabetic kidney disease (DKD) is a highly prevalent complication of diabetes and the leading cause of end-stage kidney disease. Inflammation is recognized as an important driver of progression of DKD. Activation of the immune response promotes a pro-inflammatory milieu and subsequently renal fibrosis, and a progressive loss of renal function. Although the role of the innate immune system in diabetic renal disease has been well characterized, the potential contribution of the adaptive immune system remains poorly defined. Emerging evidence in experimental models of DKD indicates an increase in the number of T cells in the circulation and in the kidney cortex, that in turn triggers secretion of inflammatory mediators such as interferon-γ and tumor necrosis factor-α, and activation of cells in innate immune response. In human studies, the number of T cells residing in the interstitial region of the kidney correlates with the degree of albuminuria in people with type 2 diabetes. Here, we review the role of the adaptive immune system, and associated cytokines, in the development of DKD. Furthermore, the potential therapeutic benefits of targeting the adaptive immune system as a means of preventing the progression of DKD are discussed.

Intranasal insulin modulates cerebrospinal fluid markers of neuroinflammation in mild cognitive impairment and Alzheimer's disease: a randomized trial

Intranasal insulin (INI) has shown promise as a treatment for Alzheimer's disease (AD) in pilot clinical trials. In a recent phase 2 trial, participants with mild cognitive impairment (MCI) or AD who were treated with INI with one of two delivery devices showed improved cerebral spinal fluid (CSF) biomarker profiles and slower symptom progression compared with placebo. In the cohort which showed benefit, we measured changes in CSF markers of inflammation, immune function and vascular integrity and assessed their relationship with changes in cognition, brain volume, and CSF amyloid and tau concentrations. The insulin-treated group had increased CSF interferon-γ (p = 0.032) and eotaxin (p = 0.049), and reduced interleukin-6 (p = 0.048) over the 12 month trial compared to placebo. Trends were observed for increased CSF macrophage-derived chemokine for the placebo group (p = 0.083), and increased interleukin-2 in the insulin-treated group (p = 0.093). Insulin-treated and placebo groups showed strikingly different patterns of associations between changes in CSF immune/inflammatory/vascular markers and changes in cognition, brain volume, and amyloid and tau concentrations. In summary, INI treatment altered the typical progression of markers of inflammation and immune function seen in AD, suggesting that INI may promote a compensatory immune response associated with therapeutic benefit.

Islet Lymphocytes Maintain a Stable Regulatory Phenotype Under Homeostatic Conditions and Metabolic Stress

T cells and B cells have been identified in human and murine islets, but the phenotype and role of islet lymphocytes is unknown. Resident immune populations set the stage for responses to inflammation in the islets during homeostasis and diabetes. Thus, we sought to identify the phenotype and effector function of islet lymphocytes to better understand their role in normal islets and in islets under metabolic stress. Lymphocytes were located in the islet parenchyma, and were comprised of a mix of naïve, activated, and memory T cell and B cell subsets, with an enrichment for regulatory B cell subsets. Use of a Nur77 reporter indicated that CD8 T cells and B cells both received local antigen stimulus, indicating that they responded to antigens present in the islets. Analysis of effector function showed that islet T cells and B cells produced the regulatory cytokine IL-10. The regulatory phenotype of islet T cells and B cells and their response to local antigenic stimuli remained stable under conditions of metabolic stress in the diet induced obesity (DIO) model. T cells present in human islets retained a similar activated and memory phenotype in non-diabetic and T2D donors. Under steady-state conditions, islet T cells and B cells have a regulatory phenotype, and thus may play a protective role in maintaining tissue homeostasis.

Specificity of Adaptive Immune Responses in Central Nervous System Health, Aging and Diseases

The field of neuroimmunology endorses the involvement of the adaptive immune system in central nervous system (CNS) health, disease, and aging. While immune cell trafficking into the CNS is highly regulated, small numbers of antigen-experienced lymphocytes can still enter the cerebrospinal fluid (CSF)-filled compartments for regular immune surveillance under homeostatic conditions. Meningeal lymphatics facilitate drainage of brain-derived antigens from the CSF to deep cervical lymph nodes to prime potential adaptive immune responses. During aging and CNS disorders, brain barriers and meningeal lymphatic functions are impaired, and immune cell trafficking and antigen efflux are altered. In this context, alterations in the immune cell repertoire of blood and CSF and T and B cells primed against CNS-derived autoantigens have been observed in various CNS disorders. However, for many diseases, a causal relationship between observed immune responses and neuropathological findings is lacking. Here, we review recent discoveries about the association between the adaptive immune system and CNS disorders such as autoimmune neuroinflammatory and neurodegenerative diseases. We focus on the current challenges in identifying specific T cell epitopes in CNS diseases and discuss the potential implications for future diagnostic and treatment options.

Thorny ground, rocky soil: Tissue-specific mechanisms of tumor dormancy and relapse

Disseminated tumor cells (DTCs) spread systemically yet distinct patterns of metastasis indicate a range of tissue susceptibility to metastatic colonization. Distinctions between permissive and suppressive tissues are still being elucidated at cellular and molecular levels. Although there is a growing appreciation for the role of the microenvironment in regulating metastatic success, we have a limited understanding of how diverse tissues regulate DTC dormancy, the state of reversible quiescence and subsequent awakening thought to contribute to delayed relapse. Several themes of microenvironmental regulation of dormancy are beginning to emerge, including vascular association, co-option of pre-existing niches, metabolic adaptation, and immune evasion, with tissue-specific nuances. Conversely, DTC awakening is often associated with injury or inflammation-induced activation of the stroma, promoting a proliferative environment with DTCs following suit. We review what is known about tissue-specific regulation of tumor dormancy on a tissue-by-tissue basis, profiling major metastatic organs including the bone, lung, brain, liver, and lymph node. An aerial view of the barriers to metastatic growth may reveal common targets and dependencies to inform the therapeutic prevention of relapse.

OUP accepted manuscript

Although major progress in multiple sclerosis research has been made during the last decades, key questions related to the cause and the mechanisms of brain and spinal cord pathology remain unresolved. These cover a broad range of topics, including disease aetiology, antigenic triggers of the immune response inside and/or outside the CNS and mechanisms of inflammation, demyelination neurodegeneration and tissue repair. Most of these questions can be addressed with novel molecular technologies in the injured CNS. Access to brain and spinal cord tissue from multiple sclerosis patients is, therefore, of critical importance. High-quality tissue is provided in part by the existing brain banks. However, material from early and highly active disease stages is limited. An initiative, realized under the patronage of the European Charcot Foundation, gathered together experts from different disciplines to analyse the current state of multiple sclerosis tissues collected post-mortem or as biopsies. Here, we present an account of what material is currently available and where it can be accessed. We also provide recommendations on how tissue donation from patients in early disease stages could be potentially increased and for procedures of tissue sampling and preservation. We also suggest to create a registry of the available tissues that, depending on the source (autopsy versus biopsy), could be made accessible to clinicians and researchers.

The precursors of CD8+ tissue resident memory T cells: from lymphoid organs to infected tissues

CD8⁺ tissue resident memory T cells (T_RM cells) are essential for immune defence against pathogens and malignancies, and the molecular processes that lead to T_RM cell formation are therefore of substantial biomedical interest. Prior work has demonstrated that signals present in the inflamed tissue micro-environment can promote the differentiation of memory precursor cells into mature T_RM cells, and it was therefore long assumed that T_RM cell formation adheres to a 'local divergence' model, in which T_RM cell lineage decisions are exclusively made within the tissue. However, a growing body of work provides evidence for a 'systemic divergence' model, in which circulating T cells already become preconditioned to preferentially give rise to the T_RM cell lineage, resulting in the generation of a pool of T_RM cell-poised T cells within the lymphoid compartment. Here, we review the emerging evidence that supports the existence of such a population of circulating T_RM cell progenitors, discuss current insights into their formation and highlight open questions in the field.

T-cell surveillance of the human brain in health and multiple sclerosis

Circulating and tissue-resident T cells collaborate in the protection of tissues against harmful infections and malignant transformation but also can instigate autoimmune reactions. Similar roles for T cells in the brain have been less evident due to the compartmentized organization of the central nervous system (CNS). In recent years, beneficial as well as occasional, detrimental effects of T-cell-targeting drugs in people with early multiple sclerosis (MS) have increased interest in T cells patrolling the CNS. Next to studies focusing on T cells in the cerebrospinal fluid, phenotypic characteristics of T cells located in the perivascular space and the meninges as well as in the parenchyma in MS lesions have been reported. We here summarize the current knowledge about T cells infiltrating the healthy and MS brain and argue that understanding the dynamics of physiological CNS surveillance by T cells is likely to improve the understanding of pathological conditions, such as MS.

Randomized trial of neoadjuvant vaccination with tumor-cell lysate induces T-cell response in low-grade gliomas

BACKGROUND

Long-term prognosis of WHO grade II low-grade glioma (LGG) is poor secondary to risk of recurrence and malignant transformation into high-grade glioma. Given the relatively intact immune system of patients with LGG and the slow tumor growth rate, vaccines are an attractive treatment strategy.

METHODS

We conducted a pilot study to evaluate the safety and immunological effects of vaccination with GBM6-AD, lysate of an allogeneic glioblastoma stem cell line, with poly-ICLC in patients with LGG. Patients were randomized to receive the vaccines before surgery (Arm 1) or not (Arm 2) and all patients received adjuvant vaccine. Co-primary outcomes were to evaluate the safety and immune response in the tumor.

RESULTS

A total of 17 eligible patients were enrolled - nine into Arm 1 and eight into Arm 2. This regimen was well-tolerated with no regimen-limiting toxicity. Neoadjuvant vaccination induced upregulation of type-1 cytokines and chemokines, and increased activated CD8+ T-cells in peripheral blood. Single-cell RNA/TCR-sequencing detected CD8+ T-cell clones that expanded with effector phenotype and migrated into tumor microenvironment (TME) in response to neoadjuvant vaccination. Mass cytometric analyses detected increased tissue resident-like CD8+ T-cells with effector memory phenotype in TME following the neoadjuvant vaccination.

CONCLUSION

The current regimen induces effector CD8+ T-cell response in peripheral blood and enables vaccine-reactive CD8+ T-cells to migrate into TME. Further refinements of the regimen may have to be integrated into future strategies.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02549833.

FUNDING

NIH (1R35NS105068, 1R21CA233856), Dabbiere Foundation, Parker Institute for Cancer Immunotherapy, and Daiichi Sankyo Foundation of Life Science.

T cell dysfunction in glioblastoma: a barrier and an opportunity for the development of successful immunotherapies

PURPOSE OF REVIEW

Immunotherapies such as immune checkpoint blockade have revolutionized cancer treatment, but current approaches have failed to improve outcomes in glioblastoma and other brain tumours. T cell dysfunction has emerged as one of the major barriers for the development of central nervous system (CNS)-directed immunotherapy. Here, we explore the unique requirements that T cells must fulfil to ensure immune surveillance in the CNS, and we analyse T cell dysfunction in glioblastoma (GBM) through the prism of CNS-resident immune responses.

RECENT FINDINGS

Using comprehensive and unbiased techniques such as single-cell RNA sequencing, multiple studies have dissected the transcriptional state of CNS-resident T cells that patrol the homeostatic brain. A similar approach has revealed that in GBM, tumour-infiltrating T cells lack the hallmarks of antigen-driven exhaustion typical of melanoma and other solid tumours, suggesting the need for better presentation of tumour-derived antigens. Consistently, in a mouse model of GBM, increasing lymphatic drainage to the cervical lymph node was sufficient to promote tumour rejection.

SUMMARY

For the success of future immunotherapy strategies, further work needs to explore the natural history of dysfunction in GBM tumour-infiltrating T cells, establish whether these originate from CNS-resident T cells and how they can be manipulated therapeutically.

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.

The Single-Cell Transcriptomic Analysis of Prefrontal Pyramidal Cells and Interneurons Reveals the Neuronal Expression of Genes Encoding Antimicrobial Peptides and Immune Proteins

The investigation of the molecular background of direct communication of neurons and immune cells in the brain is an important issue for understanding physiological and pathological processes in the nervous system. Direct contacts between brain-infiltrating immune cells and neurons, and the neuromodulatory effect of immune cell-derived regulatory peptides are well established. Several aspects of the role of immune and glial cells in the direct neuro-immune communication are also well known; however, there remain many questions regarding the molecular details of signaling from neurons to immune cells. Thus, we report here on the neuronal expression of genes encoding antimicrobial and immunomodulatory peptides, as well as proteins of immune cell-specific activation and communication mechanisms. In the present study, we analyzed the single-cell sequencing data of our previous transcriptomic work, obtained from electrophysiologically identified pyramidal cells and interneurons of the murine prefrontal cortex. We filtered out the genes that may be associated with the direct communication between immune cells and neurons and examined their expression pattern in the neuronal transcriptome. The expression of some of these genes by cortical neurons has not yet been reported. The vast majority of antimicrobial (~53%) and immune cell protein (~94%) transcripts was identified in the transcriptome of the 84 cells, owing to the high sensitivity of ultra-deep sequencing. Several of the antimicrobial and immune process-related protein transcripts showed cell type-specific or enriched expression. Individual neurons transcribed only a fraction of the investigated genes with low copy numbers probably due to the bursting kinetics of gene expression; however, the comparison of our data with available transcriptomic datasets from immune cells and neurons suggests the functional relevance of the reported findings. Accordingly, we propose further experimental and in silico studies on the neuronal expression of immune system-related genes and the potential role of the encoded proteins in neuroimmunological processes.

Transcriptional Alterations in Dorsolateral Prefrontal Cortex and Nucleus Accumbens Implicate Neuroinflammation and Synaptic Remodeling in Opioid Use Disorder

BACKGROUND

Prevalence rates of opioid use disorder (OUD) have increased dramatically, accompanied by a surge of overdose deaths. While opioid dependence has been extensively studied in preclinical models, an understanding of the biological alterations that occur in the brains of people who chronically use opioids and who are diagnosed with OUD remains limited. To address this limitation, RNA sequencing was conducted on the dorsolateral prefrontal cortex and nucleus accumbens, regions heavily implicated in OUD, from postmortem brains in subjects with OUD.

METHODS

We performed RNA sequencing on the dorsolateral prefrontal cortex and nucleus accumbens from unaffected comparison subjects (n = 20) and subjects diagnosed with OUD (n = 20). Our transcriptomic analyses identified differentially expressed transcripts and investigated the transcriptional coherence between brain regions using rank-rank hypergeometric orderlap. Weighted gene coexpression analyses identified OUD-specific modules and gene networks. Integrative analyses between differentially expressed transcripts and genome-wide association study datasets using linkage disequilibrium scores assessed the genetic liability of psychiatric-related phenotypes in OUD.

RESULTS

Rank-rank hypergeometric overlap analyses revealed extensive overlap in transcripts between the dorsolateral prefrontal cortex and nucleus accumbens in OUD, related to synaptic remodeling and neuroinflammation. Identified transcripts were enriched for factors that control proinflammatory cytokine, chondroitin sulfate, and extracellular matrix signaling. Cell-type deconvolution implicated a role for microglia as a potential driver for opioid-induced neuroplasticity. Linkage disequilibrium score analysis suggested genetic liabilities for risky behavior, attention-deficit/hyperactivity disorder, and depression in subjects with OUD.

CONCLUSIONS

Overall, our findings suggest connections between the brain's immune system and opioid dependence in the human brain.

Dementia-associated changes of immune cell composition within the cerebrospinal fluid

Inflammation and alterations in essential protein structures in the brain might also change the cellular distribution in the cerebrospinal fluid (CSF).

Using flow cytometry, we analyzed cell populations of the innate and adaptive immune system associated with the most frequent forms of dementias. We included patients with mild cognitive impairment (MCI; N ​= ​33), Alzheimer’s disease (AD; N ​= ​90), vascular dementia (VD; N ​= ​35) and frontotemporal dementia (FTD; N ​= ​17) at the time of diagnosis, before onset of treatment and 11 elderly non-demented individuals. Dependent on the form of dementia, an increased frequency of CD14⁺ monocytes, NK cells and NKT cells was measured. Within the T cell population, a dementia-associated shift from central memory towards (late-stage) effector cells was detected. T cells and NKT cells were correlated with MMSE, NK and NKT cells were correlated with ptau, CD14⁺ monocytes and NK cells were correlated with Amyloid-β 1–40.

Our data suggest that each investigated immune cell type is involved in dementia-associated alterations within the CSF, possibly having distinct functions in their pathogenesis.

Tissue-specific differentiation of CD8+ resident memory T cells

CD8⁺ tissue-resident memory T (T_RM) cells play crucial roles in defense against infections and cancer and have been implicated in autoimmune diseases such as psoriasis. In mice and humans, they exist in all nonlymphoid organs and share key characteristics across all tissues, including downregulation of tissue egress and lymph node homing pathways. However, recent studies demonstrate considerable heterogeneity across T_RM cells lodged in different tissues - linked to the activity of tissue-specific molecules, including chemokines, cytokines, and transcription factors. Current work indicates that transforming growth factor (TGF)-β plays a major role in generating T_RM heterogeneity at phenotypic and functional levels. Here, we review common and unique features of T_RM cells in different tissues and discuss putative strategies aimed at harnessing T_RM cells for site-specific protection against infectious and malignant diseases.

Signatures and Specificity of Tissue-Resident Lymphocytes Identified in Human Renal Peritumor and Tumor Tissue

BACKGROUND

Tissue-resident memory T (T_RM) cells are known to be important for the first line of defense in mucosa-associated tissues. However, the composition, localization, effector function, and specificity of T_RM cells in the human kidney and their relevance for renal pathology have not been investigated.

METHODS

Lymphocytes derived from blood, renal peritumor samples, and tumor samples were phenotypically and functionally assessed by applying flow cytometry and highly advanced histology (multi-epitope ligand cartography) methods.

RESULTS

CD69⁺CD103⁺CD8⁺ T_RM cells in kidneys display an inflammatory profile reflected by enhanced IL-2, IL-17, and TNFα production, and their frequencies correlate with increasing age and kidney function. We further identified mucosa-associated invariant T and CD56^dim and CD56^bright natural killer cells likewise expressing CD69 and CD103, the latter significantly enriched in renal tumor tissues. CD8⁺ T_RM cell frequencies were not elevated in kidney tumor tissue, but they coexpressed PD-1 and TOX and produced granzyme B. Tumor-derived CD8⁺ T_RM cells from patients with metastases were functionally impaired. Both CD69⁺CD103^-CD4⁺ and CD69⁺CD103^-CD8⁺ T_RM cells form distinct clusters in tumor tissues in proximity to antigen-presenting cells. Finally, EBV, CMV, BKV, and influenza antigen-specific CD8⁺ T cells were enriched in the effector memory T cell population in the kidney.

CONCLUSIONS

Our data provide an extensive overview of T_RM cells' phenotypes and functions in the human kidney for the first time, pointing toward their potential relevance in kidney transplantation and kidney disease.

Single-Cell Omics in Dissecting Immune Microenvironment of Malignant Gliomas-Challenges and Perspectives

Single-cell technologies allow precise identification of tumor composition at the single-cell level, providing high-resolution insights into the intratumoral heterogeneity and transcriptional activity of cells in the tumor microenvironment (TME) that previous approaches failed to capture. Malignant gliomas, the most common primary brain tumors in adults, are genetically heterogeneous and their TME consists of various stromal and immune cells playing an important role in tumor progression and responses to therapies. Previous gene expression or immunocytochemical studies of immune cells infiltrating TME of malignant gliomas failed to dissect their functional phenotypes. Single-cell RNA sequencing (scRNA-seq) and cytometry by time-of-flight (CyTOF) are powerful techniques allowing quantification of whole transcriptomes or >30 protein targets in individual cells. Both methods provide unprecedented resolution of TME. We summarize the findings from these studies and the current state of knowledge of a functional diversity of immune infiltrates in malignant gliomas with different genetic alterations. A precise definition of functional phenotypes of myeloid and lymphoid cells might be essential for designing effective immunotherapies. Single-cell omics studies have identified crucial cell subpopulations and signaling pathways that promote tumor progression, influence patient survival or make tumors vulnerable to immunotherapy. We anticipate that the widespread usage of single-cell omics would allow rational design of oncoimmunotherapeutics.

IL-17 triggers the onset of cognitive and synaptic deficits in early stages of Alzheimer's disease

Neuroinflammation in patients with Alzheimer's disease (AD) and related mouse models has been recognized for decades, but the contribution of the recently described meningeal immune population to AD pathogenesis remains to be addressed. Here, using the 3xTg-AD model, we report an accumulation of interleukin-17 (IL-17)-producing cells, mostly γδ T cells, in the brain and the meninges of female, but not male, mice, concomitant with the onset of cognitive decline. Critically, IL-17 neutralization into the ventricles is sufficient to prevent short-term memory and synaptic plasticity deficits at early stages of disease. These effects precede blood-brain barrier disruption and amyloid-beta or tau pathology, implying an early involvement of IL-17 in AD pathology. When IL-17 is neutralized at later stages of disease, the onset of short-memory deficits and amyloidosis-related splenomegaly is delayed. Altogether, our data support the idea that cognition relies on a finely regulated balance of "inflammatory" cytokines derived from the meningeal immune system.

Dysregulated Microglial Cell Activation and Proliferation Following Repeated Antigen Stimulation

Upon reactivation of quiescent neurotropic viruses antigen (Ag)-specific brain resident-memory CD8+ T-cells (bT_RM) may respond to de novo-produced viral Ag through the rapid release of IFN-γ, which drives subsequent interferon-stimulated gene expression in surrounding microglia. Through this mechanism, a small number of adaptive bT_RM may amplify responses to viral reactivation leading to an organ-wide innate protective state. Over time, this brain-wide innate immune activation likely has cumulative neurotoxic and neurocognitive consequences. We have previously shown that HIV-1 p24 Ag-specific bT_RM persist within the murine brain using a heterologous prime-CNS boost strategy. In response to Ag restimulation, these bT_RM display rapid and robust recall responses, which subsequently activate glial cells. In this study, we hypothesized that repeated challenges to viral antigen (Ag) (modeling repeated episodes of viral reactivation) culminate in prolonged reactive gliosis and exacerbated neurotoxicity. To address this question, mice were first immunized with adenovirus vectors expressing the HIV p24 capsid protein, followed by a CNS-boost using Pr55Gag/Env virus-like particles (HIV-VLPs). Following the establishment of the bT_RM population [>30 days (d)], prime-CNS boost animals were then subjected to in vivo challenge, as well as re-challenge (at 14 d post-challenge), using the immunodominant HIV-1 AI9 CD8+ T-cell epitope peptide. In these studies, Ag re-challenge resulted in prolonged expression of microglial activation markers and an increased proliferative response, longer than the challenge group. This continued expression of MHCII and PD-L1 (activation markers), as well as Ki67 (proliferative marker), was observed at 7, 14, and 30 days post-AI9 re-challenge. Additionally, in vivo re-challenge resulted in continued production of inducible nitric oxide synthase (iNOS) with elevated levels observed at 7, 14 and 30 days post re-challenge. Interestingly, iNOS expression was significantly lower among challenged animals when compared to re-challenged groups. Furthermore, in vivo specific Ag re-challenge produced lower levels of arginase (Arg)-1 when compared with the challenged group. Taken together, these results indicate that repeated Ag-specific stimulation of adaptive immune responses leads to cumulative dysregulated microglial cell activation.

Tissue-Resident Memory T Cells in Skin Diseases: A Systematic Review

In health, the non-recirculating nature and long-term persistence of tissue-resident memory T cells (TRMs) in tissues protects against invading pathogens. In disease, pathogenic TRMs contribute to the recurring traits of many skin diseases. We aimed to conduct a systematic literature review on the current understanding of the role of TRMs in skin diseases and identify gaps as well as future research paths. EMBASE, PubMed, SCOPUS, Web of Science, Clinicaltrials.gov and WHO Trials Registry were searched systematically for relevant studies from their inception to October 2020. Included studies were reviewed independently by two authors. This study was conducted in accordance with the PRISMA-S guidelines. This protocol was registered with the PROSPERO database (ref: CRD42020206416). We identified 96 studies meeting the inclusion criteria. TRMs have mostly been investigated in murine skin and in relation to infectious skin diseases. Pathogenic TRMs have been characterized in various skin diseases including psoriasis, vitiligo and cutaneous T-cell lymphoma. Studies are needed to discover biomarkers that may delineate TRMs poised for pathogenic activity in skin diseases and establish to which extent TRMs are contingent on the local skin microenvironment. Additionally, future studies may investigate the effects of current treatments on the persistence of pathogenic TRMs in human skin.

Cellular and Molecular Effects of SARS-CoV-2 Linking Lung Infection to the Brain

In December 2019, a new viral disease emerged and quickly spread all around the world. In March 2020, the COVID-19 outbreak was classified as a global pandemic and by June 2021, the number of infected people grew to over 170 million. Along with the patients' mild-to-severe respiratory symptoms, reports on probable central nervous system (CNS) effects appeared shortly, raising concerns about the possible long-term detrimental effects on human cognition. It remains unresolved whether the neurological symptoms are caused directly by the SARS-CoV-2 infiltration in the brain, indirectly by secondary immune effects of a cytokine storm and antibody overproduction, or as a consequence of systemic hypoxia-mediated microglia activation. In severe COVID-19 cases with impaired lung capacity, hypoxia is an anticipated subsidiary event that can cause progressive and irreversible damage to neurons. To resolve this problem, intensive research is currently ongoing, which seeks to evaluate the SARS-CoV-2 virus' neuroinvasive potential and the examination of the antibody and autoantibody generation upon infection, as well as the effects of prolonged systemic hypoxia on the CNS. In this review, we summarize the current research on the possible interplay of the SARS-CoV-2 effects on the lung, especially on alveolar macrophages and direct and indirect effects on the brain, with special emphasis on microglia, as a possible culprit of neurological manifestation during COVID-19.

Reversing Epigenetic Gene Silencing to Overcome Immune Evasion in CNS Malignancies

Glioblastoma (GBM) is an aggressive brain malignancy with a dismal prognosis. With emerging evidence to disprove brain-immune privilege, there has been much interest in examining immunotherapy strategies to treat central nervous system (CNS) cancers. Unfortunately, the limited success of clinical studies investigating immunotherapy regimens, has led to questions about the suitability of immunotherapy for these cancers. Inadequate inherent populations of tumor infiltrating lymphocytes (TILs) and limited trafficking of systemic, circulating T cells into the CNS likely contribute to the poor response to immunotherapy. This paucity of TILs is in concert with the finding of epigenetic silencing of genes that promote immune cell movement (chemotaxis) to the tumor. In this study we evaluated the ability of GSK126, a blood-brain barrier (BBB) permeable small molecule inhibitor of EZH2, to reverse GBM immune evasion by epigenetic suppression of T cell chemotaxis. We also evaluated the in vivo efficacy of this drug in combination with anti-PD-1 treatment on tumor growth, survival and T cell infiltration in syngeneic mouse models. GSK126 reversed H3K27me³ in murine and human GBM cell lines. When combined with anti-PD-1 treatment, a significant increase in activated T cell infiltration into the tumor was observed. This resulted in decreased tumor growth and enhanced survival both in sub-cutaneous and intracranial tumors of immunocompetent, syngeneic murine models of GBM. Additionally, a significant increase in CXCR3⁺ T cells was also seen in the draining lymph nodes, suggesting their readiness to migrate to the tumor. Closer examination of the mechanism of action of GSK126 revealed its ability to promote the expression of IFN-γ driven chemokines CXCL9 and CXCL10 from the tumor cells, that work to traffic T cells without directly affecting T maturation and/or proliferation. The loss of survival benefit either with single agent or combination in immunocompromised SCID mice, suggest that the therapeutic efficacy of GSK126 in GBM is primarily driven by lymphocytes. Taken together, our data suggests that in glioblastoma, epigenetic modulation using GSK126 could improve current immunotherapy strategies by reversing the epigenetic changes that enable immune cell evasion leading to enhanced immune cell trafficking to the tumor.

The CD8 T Cell-Epstein-Barr Virus-B Cell Trialogue: A Central Issue in Multiple Sclerosis Pathogenesis

The cause and the pathogenic mechanisms leading to multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system (CNS), are still under scrutiny. During the last decade, awareness has increased that multiple genetic and environmental factors act in concert to modulate MS risk. Likewise, the landscape of cells of the adaptive immune system that are believed to play a role in MS immunopathogenesis has expanded by including not only CD4 T helper cells but also cytotoxic CD8 T cells and B cells. Once the key cellular players are identified, the main challenge is to define precisely how they act and interact to induce neuroinflammation and the neurodegenerative cascade in MS. CD8 T cells have been implicated in MS pathogenesis since the 80's when it was shown that CD8 T cells predominate in MS brain lesions. Interest in the role of CD8 T cells in MS was revived in 2000 and the years thereafter by studies showing that CNS-recruited CD8 T cells are clonally expanded and have a memory effector phenotype indicating in situ antigen-driven reactivation. The association of certain MHC class I alleles with MS genetic risk implicates CD8 T cells in disease pathogenesis. Moreover, experimental studies have highlighted the detrimental effects of CD8 T cell activation on neural cells. While the antigens responsible for T cell recruitment and activation in the CNS remain elusive, the high efficacy of B-cell depleting drugs in MS and a growing number of studies implicate B cells and Epstein-Barr virus (EBV), a B-lymphotropic herpesvirus that is strongly associated with MS, in the activation of pathogenic T cells. This article reviews the results of human studies that have contributed to elucidate the role of CD8 T cells in MS immunopathogenesis, and discusses them in light of current understanding of autoreactivity, B-cell and EBV involvement in MS, and mechanism of action of different MS treatments. Based on the available evidences, an immunopathological model of MS is proposed that entails a persistent EBV infection of CNS-infiltrating B cells as the target of a dysregulated cytotoxic CD8 T cell response causing CNS tissue damage.

Skin and gut imprinted helper T cell subsets exhibit distinct functional phenotypes in central nervous system autoimmunity

Multidimensional single-cell analyses of T cells have fueled the debate about whether there is extensive plasticity or 'mixed' priming of helper T cell subsets in vivo. Here, we developed an experimental framework to probe the idea that the site of priming in the systemic immune compartment is a determinant of helper T cell-induced immunopathology in remote organs. By site-specific in vivo labeling of antigen-specific T cells in inguinal (i) or gut draining mesenteric (m) lymph nodes, we show that i-T cells and m-T cells isolated from the inflamed central nervous system (CNS) in a model of multiple sclerosis (MS) are distinct. i-T cells were Cxcr6+, and m-T cells expressed P2rx7. Notably, m-T cells infiltrated white matter, while i-T cells were also recruited to gray matter. Therefore, we propose that the definition of helper T cell subsets by their site of priming may guide an advanced understanding of helper T cell biology in health and disease.

The Role of NKT Cells in Glioblastoma

Glioblastoma is an aggressive and deadly cancer, but to date, immunotherapies have failed to make significant strides in improving prognoses for glioblastoma patients. One of the current challenges to developing immunological interventions for glioblastoma is our incomplete understanding of the numerous immunoregulatory mechanisms at play in the glioblastoma tumor microenvironment. We propose that Natural Killer T (NKT) cells, which are unconventional T lymphocytes that recognize lipid antigens presented by CD1d molecules, may play a key immunoregulatory role in glioblastoma. For example, evidence suggests that the activation of type I NKT cells can facilitate anti-glioblastoma immune responses. On the other hand, type II NKT cells are known to play an immunosuppressive role in other cancers, as well as to cross-regulate type I NKT cell activity, although their specific role in glioblastoma remains largely unclear. This review provides a summary of our current understanding of NKT cells in the immunoregulation of glioblastoma as well as highlights the involvement of NKT cells in other cancers and central nervous system diseases.

B Cells in Neuroinflammation: New Perspectives and Mechanistic Insights

In recent years, the role of B cells in neurological disorders has substantially expanded our perspectives on mechanisms of neuroinflammation. The success of B cell-depleting therapies in patients with CNS diseases such as neuromyelitis optica and multiple sclerosis has highlighted the importance of neuroimmune crosstalk in inflammatory processes. While B cells are essential for the adaptive immune system and antibody production, they are also major contributors of pro- and anti-inflammatory cytokine responses in a number of inflammatory diseases. B cells can contribute to neurological diseases through peripheral immune mechanisms, including production of cytokines and antibodies, or through CNS mechanisms following compartmentalization. Emerging evidence suggests that aberrant pro- or anti-inflammatory B cell populations contribute to neurological processes, including glial activation, which has been implicated in the pathogenesis of several neurodegenerative diseases. In this review, we summarize recent findings on B cell involvement in neuroinflammatory diseases and discuss evidence to support pathogenic immunomodulatory functions of B cells in neurological disorders, highlighting the importance of B cell-directed therapies.

The role of T cells in age-related diseases

Age-related T cell dysfunction can lead to failure of immune tolerance mechanisms, resulting in aberrant T cell-driven cytokine and cytotoxic responses that ultimately cause tissue damage. In this Review, we discuss the role of T cells in the onset and progression of age-associated conditions, focusing on cardiovascular disorders, metabolic dysfunction, neuroinflammation and defective tissue repair and regeneration. We present different mechanisms by which T cells contribute to inflammageing and might act as modulators of age-associated diseases, including through enhanced pro-inflammatory and cytotoxic activity, defective clearance of senescent cells or regulation of the gut microbiota. Finally, we propose that 'resetting' immune system tolerance or targeting pathogenic T cells could open up new therapeutic opportunities to boost resilience to age-related diseases.

Maintenance of WT1 expression in tumor cells is associated with a good prognosis in malignant glioma patients treated with WT1 peptide vaccine immunotherapy

We have previously revealed the overexpression of Wilms' tumor gene 1 (WT1) in malignant glioma and developed WT1 peptide vaccine cancer immunotherapy. A phase II clinical trial indicated the clinical efficacy of the WT1 peptide vaccine for recurrent malignant glioma. Here, we aimed to investigate the immunological microenvironment in glioma tissues before and after WT1 peptide vaccine treatment. Paired tissue samples were obtained from 20 malignant glioma patients who had received the WT1 peptide vaccine for > 3 months and experienced tumor progression, confirmed radiographically and/or clinically, during vaccination. We discovered that the expression of WT1 and HLA class I antigens in the tumor cells significantly decreased after vaccination. Maintenance of WT1 expression, which is the target molecule of immunotherapy, in tumor cells during the vaccination period was significantly associated with a longer progression-free and overall survival. A high expression of HLA class I antigens and low CD4⁺/CD8⁺ tumor-infiltrating lymphocytes (TIL) ratio in pre-vaccination specimens, were also associated with a good prognosis. No statistically significant difference existed in the number of infiltrating CD3⁺ or CD8⁺ T cells between the pre- and post-vaccination specimens, whereas the number of infiltrating CD4⁺ T cells significantly decreased in the post-vaccination specimens. This study provides insight into the mechanisms of intra-tumoral immune reaction/escape during WT1 peptide vaccine treatment and suggests potential clinical strategies for cancer immunotherapy.

Neurodegeneration in Multiple Sclerosis: Symptoms of Silent Progression, Biomarkers and Neuroprotective Therapy-Kynurenines Are Important Players

Neurodegeneration is one of the driving forces behind the pathogenesis of multiple sclerosis (MS). Progression without activity, pathopsychological disturbances (cognitive impairment, depression, fatigue) and even optic neuropathy seems to be mainly routed in this mechanism. In this article, we aim to give a comprehensive review of the clinical aspects and symptomology, radiological and molecular markers and potential therapeutic targets of neurodegeneration in connection with MS. As the kynurenine pathway (KP) was evidenced to play an important role in the pathogenesis of other neurodegenerative conditions (even implied to have a causative role in some of these diseases) and more and more recent evidence suggest the same central role in the neurodegenerative processes of MS as well, we pay special attention to the KP. Metabolites of the pathway are researched as biomarkers of the disease and new, promising data arising from clinical evaluations show the possible therapeutic capability of KP metabolites as neuroprotective drugs in MS. Our conclusion is that the kynurenine pathway is a highly important route of research both for diagnostic and for therapeutic values and is expected to yield concrete results for everyday medicine in the future.

Deep immune profiling reveals targetable mechanisms of immune evasion in immune checkpoint inhibitor-refractory glioblastoma

BACKGROUND

Glioblastoma (GBM) is refractory to immune checkpoint inhibitor (ICI) therapy. We sought to determine to what extent this immune evasion is due to intrinsic properties of the tumor cells versus the specialized immune context of the brain, and if it can be reversed.

METHODS

We used CyTOF mass cytometry to compare the tumor immune microenvironments (TIME) of human tumors that are generally ICI-refractory (GBM and sarcoma) or ICI-responsive (renal cell carcinoma), as well as mouse models of GBM that are ICI-responsive (GL261) or ICI-refractory (SB28). We further compared SB28 tumors grown intracerebrally versus subcutaneously to determine how tumor site affects TIME and responsiveness to dual CTLA-4/PD-1 blockade. Informed by these data, we explored rational immunotherapeutic combinations.

RESULTS

ICI-sensitivity in human and mouse tumors was associated with increased T cells and dendritic cells (DCs), and fewer myeloid cells, in particular PD-L1+ tumor-associated macrophages. The SB28 mouse model of GBM responded to ICI when grown subcutaneously but not intracerebrally, providing a system to explore mechanisms underlying ICI resistance in GBM. The response to ICI in the subcutaneous SB28 model required CD4 T cells and NK cells, but not CD8 T cells. Recombinant FLT3L expanded DCs, improved antigen-specific T cell priming, and prolonged survival of mice with intracerebral SB28 tumors, but at the cost of increased Tregs. Targeting PD-L1 also prolonged survival, especially when combined with stereotactic radiation.

CONCLUSIONS

Our data suggest that a major obstacle for effective immunotherapy of GBM is poor antigen presentation in the brain, rather than intrinsic immunosuppressive properties of GBM tumor cells. Deep immune profiling identified DCs and PD-L1+ tumor-associated macrophages as promising targetable cell populations, which was confirmed using therapeutic interventions in vivo.

Imbalance between T helper 1 and regulatory T cells plays a detrimental role in experimental Parkinson's disease in mice

Objective

Parkinson’s disease (PD) is a degenerative disorder characterized by steady motor function loss. PD pathogenesis remains inconclusive, but aberrant immune responses might play important roles. We hypothesized that imbalance between T helper (Th) 1 and regulatory T (Treg) cells was essential in experimental PD.

Methods

Th1 and Treg cells from the blood of patients with PD and healthy volunteer blood were measured by flow cytometry. Experimental PD was induced in mice by peritoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Experimental PD severity was measured by open field test behavior assessments (distance moved, rearing, and grooming). Mice were administered neutralizing anti-tumor necrosis factor (TNF) α to inhibit Th1 effects. Treg cells were depleted by anti-CD25 neutralizing antibodies or isolated and transferred to experimental PD mice.

Results

Patients with PD had fewer Treg and more Th1 cells than healthy volunteers. Experimental PD mice exhibited fewer Treg and more Th1 cells. Treg cell depletion exacerbated experimental PD, whereas TNFα neutralization attenuated PD in mice. Treg transfer to experimental PD mice reduced PD severity. Mechanistically, anti-TNFα antibody administration and Treg transfer increased Treg and reduced Th1 cell abundance in the brain.

Conclusion

Th1 and Treg cell imbalance plays an essential role in mouse experimental PD pathogenesis.

Capturing T Lymphocytes' Dynamic Interactions With Human Neural Cells Using Time-Lapse Microscopy

To fully perform their functions, T lymphocytes migrate within organs’ parenchyma and interact with local cells. Infiltration of T lymphocytes within the central nervous system (CNS) is associated with numerous neurodegenerative disorders. Nevertheless, how these immune cells communicate and respond to neural cells remains unresolved. To investigate the behavior of T lymphocytes that reach the CNS, we have established an in vitro co-culture model and analyzed the spatiotemporal interactions between human activated CD8⁺ T lymphocytes and primary human astrocytes and neurons using time-lapse microscopy. By combining multiple variables extracted from individual CD8⁺ T cell tracking, we show that CD8⁺ T lymphocytes adopt a more motile and exploratory behavior upon interacting with astrocytes than with neurons. Pretreatment of astrocytes or neurons with IL-1β to mimic in vivo inflammation significantly increases CD8⁺ T lymphocyte motility. Using visual interpretation and analysis of numerical variables extracted from CD8⁺ T cell tracking, we identified four distinct CD8⁺ T lymphocyte behaviors: scanning, dancing, poking and round. IL-1β-pretreatment significantly increases the proportion of scanning CD8⁺ T lymphocytes, which are characterized by active exploration, and reduces the proportion of round CD8⁺ T lymphocytes, which are less active. Blocking MHC class I on astrocytes significantly diminishes the proportion of poking CD8⁺ T lymphocytes, which exhibit synapse-like interactions. Lastly, our co-culture time-lapse model is easily adaptable and sufficiently sensitive and powerful to characterize and quantify spatiotemporal interactions between human T lymphocytes and primary human cells in different conditions while preserving viability of fragile cells such as neurons and astrocytes.