Integration of Th17- and Lymphotoxin-Derived Signals Initiates Meningeal-Resident Stromal Cell Remodeling to Propagate Neuroinflammation

Meningeal leukaemic aggregates as foci of cell expansion and chemoresistance in acute lymphoblastic leukaemia metastasis

PURPOSE

Central nervous system (CNS) involvement and/or relapse remains one of the most important causes of morbidity/mortality in paediatric B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) patients. To identify novel therapeutic targets and develop less aggressive therapies, a better understanding of the cellular and molecular microenvironment in leptomeningeal metastases is key. Here, we aimed to investigate the formation of metastatic leptomeningeal aggregates and their relevance to the expansion, survival and chemoresistance acquisition of leukaemia cells.

METHODS

We used BCP-ALL xenograft mouse models, combined with immunohistofluorescence and flow cytometry, to study the development of CNS metastasis and the contribution of leptomeningeal cells to the organisation of leukaemic aggregates. To in vitro mimic the CNS metastasis, we established co-cultures of three-dimensional (3D) ALL cell spheroids and human leptomeningeal cells (hLMCs) and studied the effects on gene expression, proliferation, cytokine production, and chemoresistance.

RESULTS

In xenografted mice, ALL cells infiltrated the CNS at an early stage and, after crossing an ER-TR7+ fibroblast-like meningeal cell layer, they proliferated extensively and formed large vascularised leukaemic aggregates supported by a network of podoplanin+ leptomeningeal cells. In leukaemia spheroid-hLMC co-cultures, unlike conventional 2D co-cultures, meningeal cells strongly promoted the proliferation of leukaemic cells and generated a pro-inflammatory microenvironment. Furthermore, in 3D cell aggregates, leukaemic cells also developed chemoresistance, at least in part due to ABC transporter up-regulation.

CONCLUSION

Our results provide evidence for the formation of metastatic ALL-leptomeningeal cell aggregates, their pro-inflammatory profile and their contribution to leukaemic cell expansion, survival and chemoresistance in the CNS.

Tertiary lymphoid structures in gliomas: impact on tumour immunity and progression

Tertiary lymphoid structures (TLSs) are ectopic lymphoid formations that develop in chronically inflamed tissues, including various solid tumours. In the context of gliomas, the presence of TLSs has recently attracted considerable attention because of their potential implications in tumour immunology and therapy. The tumour immune microenvironment (TIME) plays a crucial role in cancer progression, and tumour-infiltrating immune cells (TILs) are key players in this environment. These immune cell aggregates, known as TLSs, display distinct characteristics across different solid tumours. However, central nervous system (CNS) tumours are highly heterogeneous, and the immune environment within these tumours is often more deficient than that of peripheral tissue tumours. This leads to differences in the formation and function of TLSs in CNS tumours. These variations are particularly relevant in the context of glioma immunotherapy and could have important implications for treatment strategies. This review focuses on the composition and function of TLSs, examines the complexity of the glioblastoma (GBM) immune microenvironment, and highlights the unique characteristics of TLSs in GBM, providing new theoretical insights and practical foundations for targeting TLSs in glioma immunotherapy.

Redefining CNS immune privilege

The central nervous system (CNS) has a unique relationship with the immune system, referred to as immune privilege. For many years it was thought that immune privilege was due to isolation of the CNS from the immune system, but recent findings have shown that this theory is flawed and that there is substantial neuroimmune communication, particularly at border sites that encase the CNS. These border sites include perivascular and subarachnoid spaces, the choroid plexus, the meninges and the vasculature, including the recently discovered meningeal lymphatic vessels. CNS border tissues have extensive interaction with the cerebrospinal fluid, which acts as an immune mediator, allowing the immune system at the CNS borders to respond to challenges within the CNS parenchyma. Together, CNS border tissues enable immune surveillance and protection against infections while preventing inflammatory damage to the parenchyma. A better understanding of the mechanisms of immune privilege as an accord, as opposed to isolation, between the two systems would help us obtain effective immunotherapies for neurological diseases.

T-B cell cooperation in ectopic lymphoid follicles propagates CNS autoimmunity

Meningeal ectopic lymphoid follicle (eLF)-like structures have been described in multiple sclerosis, but their role in central nervous system (CNS) autoimmunity is unclear. Here, we used a T helper 17 (TH17) adoptive transfer experimental autoimmune encephalomyelitis model featuring formation of eLFs. Single-cell RNA sequencing revealed that clusters of activated B cells and B1/marginal zone-like B cells were overrepresented in the CNS and identified B cells poised for undergoing germinal center reactions and clonal expansion in the CNS. Using intravital imaging to directly visualize TH17-B cell interactions, we demonstrated that T and B cells form long-lasting antigen-specific contacts in meningeal eLFs that result in reactivation of autoreactive T cells. CNS T cells depended on CNS B cells to maintain a proinflammatory cytokine profile. Our study reveals that extensive T-B cell cooperation occurs in meningeal eLFs, promoting both B cell differentiation and T cell reactivation, and may thereby propagate smoldering inflammation in the CNS.

Multiple mechanisms and applications of tertiary lymphoid structures and immune checkpoint blockade

BACKGROUND

Immune checkpoint blockade (ICB) inhibits tumor immune escape and has significantly advanced tumor therapy. However, ICB benefits only a minority of patients treated and may lead to many immune-related adverse events. Therefore, identifying factors that can predict treatment outcomes, enhance synergy with ICB, and mitigate immune-related adverse events is urgently needed.

MAIN TEXT

Tertiary lymphoid structures (TLS) are ectopic lymphoid tissues that arise from the tumor periphery. They have been found to be associated with better prognosis and improved clinical outcomes after ICB therapy. TLS may help address the problems associated with ICB. The multiple mechanisms of action between TLS and ICB remain unknown. This paper described potential mechanisms of interaction between the two and explored their potential applications.

Identifying potential mechanism and targets for treatment of tertiary lymphoid structure in lupus nephritis based on bioinformatics analysis

BACKGROUND

Tertiary lymphoid structure (TLS) is an ectopic lymphoid structure that develops in non-lymphoid structures. Some studies have shown that the TLS formed in autoimmune diseases, such as lupus nephropathy (LN), can cause damage to normal tissues and continuous disease progression. Nevertheless, there is still a lack of efficient treatments for TLS in LN. Thus, the study aims to identify potential targets for therapy of TLS in LN.

METHODS

Mice datasets relative to TLS were obtained from Gene Expression Omnibus (GEO). The differentially expressed genes (DEGs) were identified from mice datasets. Then, the Genetic Ontological (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed. The Protein-Protein Interaction (PPI) network was constructed. Additionally, the hub genes were selected by Cytoscape and verified by human databases from GEO. The relationships between the immune cells with hub genes were explored. Finally, the two genes PSMB9 and STAT1 were validated in the kidney tissues of LN patients and mice.

RESULTS

443 DEGs and 178 DEGs relative to TLS were filtered from GSE160488 and GSE155405, respectively. The enrichment results of these genes mostly focused on inflammatory response, cytokine-cytokine receptor interaction, and immune system process. Six genes were recognized by Cytoscape. According to the validation of six genes in human databases, the two hub genes (PSMB9 and STAT1) were also significantly expressed in LN patients. Immune infiltration analysis of hub genes shows immune cells are significantly crucial in LN patients with TLS.

CONCLUSION

PSMB9 and STAT1 may be identified as possible targets for the treatment of TLS in LN. According to the analysis of the interaction between these genes and immune cells, the immune process mediated by these signature targets takes part in the advancement and formation of TLS.

Immune conversations at the border: meningeal immunity in health and disease

The brain and spinal cord, collectively known as the central nervous system, are encapsulated by an overlapping series of membranes known as the meninges. Once considered primarily a physical barrier for central nervous system protection, the bordering meninges are now recognized as highly immunologically active. The meninges host diverse resident immune cells and serve as a critical interface with peripheral immunity, playing multifaceted roles in maintaining central nervous system homeostasis, responding to pathogenic threats, and neurological disorders. This review summarizes recent advancements in our understanding of meningeal immunity including its structural composition, physiological functions, and role in health and disease.

Toll-like receptor agonists promote the formation of tertiary lymphoid structure and improve anti-glioma immunity

BACKGROUND

Glioma, characterized by limited lymphocytic infiltration, constitutes an "immune-desert" tumor displaying insensitivity to various immunotherapies. This study aims to explore therapeutic strategies for inducing tertiary lymphoid structure (TLS) formation within the glioma microenvironment (GME) to transition it from an immune resistant to an activated state.

METHODS

TLS formation in GME was successfully induced by intracranial administration of Toll-like receptor (TLR) agonists (OK-432, TLR2/4/9 agonist) and glioma antigens (i.c. αTLR-mix). We employed staining analysis, antibody neutralization, single-cell RNA sequencing (scRNA-Seq), and BCR/TCR sequencing to investigate the underlying mechanisms of TLS formation and its role in anti-glioma immunity. Additionally, a preliminary translational clinical study was conducted.

RESULTS

TLS formation correlated with increased lymphocyte infiltration in GME and led to improved prognosis in glioma-bearing mice. In the study of TLS induction mechanisms, certain macrophages/microglia and Th17 displayed markers of "LTo" and "LTi" cells, respectively, interaction through LTα/β-LTβR promoted TLS induction. Post-TLS formation, CD4 + and CD8 + T cells but not CD19 + B cells contributed to anti-glioma immunity. Comparative analysis of B/T cells between brain and lymph node showed that brain B/T cells unveiled the switch from naïve to mature, some B cells highlighted an enrichment of class switch recombination (CSR)-associated genes, V gene usage, and clonotype bias were observed. In related clinical studies, i.c. αTLR-mix treatment exhibited tolerability, and chemokines/cytokines assay provided preliminary evidence supporting TLS formation in GME.

CONCLUSIONS

TLS induction in GME enhanced anti-glioma immunity, improved the immune microenvironment, and controlled glioma growth, suggesting potential therapeutic avenues for treating glioma in the future.

Tertiary Lymphoid Structures in Central Nervous System Disorders

The central nervous system (CNS) constitutes a tightly regulated milieu, where immune responses are strictly controlled to prevent neurological damage. This poses considerable challenges to the therapeutic management of CNS pathologies, such as autoimmune disorders and cancer. Tertiary lymphoid structures (TLS) are ectopic, lymph node-like structures containing B- and T-cells, often associated with chronic inflammation or cancer, which have been shown to be detrimental in autoimmunity but beneficial in cancer. In-depth studies of TLS induction in CNS disorders, as well as their precise role in regulating adaptive immune responses in this context, will be paramount to the development of novel TLS-targeting therapies. In the present chapter, we review the anatomical and physiological peculiarities shaping TLS formation in the CNS, their relevance in autoimmunity and cancer, as well as their implications for the development of novel therapeutic modalities for these patients.

Cathepsin C exacerbates EAE by promoting the expansion of Tfh cells and the formation of TLSs in the CNS

Multiple sclerosis (MS) is a chronic autoimmune disease of the central nervous system (CNS) mediated by CD4+ T helper (Th) cells, and characterized by immune cell infiltration, demyelination and neurodegeneration, with no definitive cure available. Thus, it is pivotal and imperative to acquire more profound comprehension of the underlying mechanisms implicated in MS. Dysregulated immune responses are widely believed to play a primary role in the pathogenesis of MS. Recently, a plethora of studies have demonstrated the involvement of T follicular helper (Tfh) cells and tertiary lymphoid-like structures (TLSs) in the pathogenesis and progression of MS. Cathepsin C (CatC) is a cysteine exopeptidase which is crucial for the activation of immune-cell-associated serine proteinases in many inflammatory diseases in peripheral system, such as rheumatoid arthritis and septicemia. We have previously demonstrated that CatC is involved in neuroinflammation and exacerbates demyelination in both cuprizone-induced and experimental autoimmune encephalomyelitis (EAE) mouse models. However, the underlying immunopathological mechanism remains elusive. In the present study, we established a recombinant myelin oligodendrocyte glycoprotein 35-55 peptide-induced EAE model using conditional CatC overexpression mice to investigate the effects of CatC on the alteration of CD4+ Th subsets, including Th1, Th2, Th17, Tfh and T regulatory cells. Our findings demonstrated that CatC particularly enhanced the population of Tfh cell in the brain, resulting in the earlier onset and more severe chronic syndrome of EAE. Furthermore, CatC promoted the formation of TLSs in the brain, leading to persistent neuroinflammation and exacerbating the severity of EAE in the chronic phase. Conversely, treatment with AZD7986, a specific inhibitor of CatC, effectively attenuated the syndrome of EAE and its effects caused by CatC both in vivo and in vitro. These findings provide a novel insight into the critical role of CatC in innate and adaptive immunity in EAE, and specific inhibitor of CatC, AZD7986, may contribute to potential therapeutic strategies for MS.

Maturation of Tertiary Lymphoid Structures

Tertiary lymphoid structures (TLS) are organized collections of B and T lymphocytes that arise in nonlymphoid tissue in response to chronic, unresolved inflammation. TLS have structural and functional similarities to germinal centers found in lymph nodes and are believed to support the establishment of lymph node-like adaptive immune responses at local sites of inflammation. However, understanding of the underlying biology of these structures remains limited, particularly the different stages of TLS life cycle and the signals governing the initiation, maturation, and termination of TLS. Here, we review current understanding of the maturation of TLS and the signals and cell types involved in various stages of development with particular emphasis on recent studies of TLS in cancer, where evidence suggests that TLS may play an important role in supporting antitumor immune responses in solid tumors.

Disease-modifying therapies for Parkinson disease: lessons from multiple sclerosis

The development of disease-modifying therapies (DMTs) for neurological disorders is an important goal in modern neurology, and the associated challenges are similar in many chronic neurological conditions. Major advances have been made in the multiple sclerosis (MS) field, with a range of DMTs being approved for relapsing MS and the introduction of the first DMTs for progressive MS. By contrast, people with Parkinson disease (PD) still lack such treatment options, relying instead on decades-old therapeutic approaches that provide only symptomatic relief. To address this unmet need, an in-person symposium was held in Toronto, Canada, in November 2022 for international researchers and experts in MS and PD to discuss strategies for advancing DMT development. In this Roadmap article, we highlight discussions from the symposium, which focused on therapeutic targets and preclinical models, disease spectra and subclassifications, and clinical trial design and outcome measures. From these discussions, we propose areas for novel or deeper exploration in PD using lessons learned from therapeutic development in MS. In addition, we identify challenges common to the PD and MS fields that need to be addressed to further advance the discovery and development of effective DMTs.

Key actors in neuropathophysiology: The role of γδ T cells

The neuroimmune axis has been the focus of many studies, with special emphasis on the interactions between the central nervous system and the different immune cell subsets. T cells are namely recognized to play a critical role due to their interaction with nerves, by secreting cytokines and neurotrophins, which regulate the development, function, and survival of neurons. In this context, γδ T cells are particularly relevant, as they colonize specific tissues, namely the meninges, and have a wide variety of complex functions that balance physiological systems. Notably, γδ T cells are not only key components for maintaining brain homeostasis but are also responsible for triggering or preventing inflammatory responses in various pathologies, including neurodegenerative diseases as well as neuropsychiatric and developmental disorders. Here, we provide an overview of the current state of the art on the contribution of γδ T cells in neuropathophysiology and delve into the molecular mechanisms behind it. We aim to shed light on γδ T cell functions in the central nervous system while highlighting upcoming challenges in the field and providing new clues for potential therapeutic strategies.

Tertiary lymphoid structures in the central nervous system

Tertiary lymphoid structures (TLSs) frequently occur at sites of chronic inflammation. A more advanced stage of multiple sclerosis (MS) has been associated with certain TLSs. However, tumor-associated TLSs have been shown to correlate with a greater treatment response rate and a better prognosis in glioma mouse models. In this review, we evaluate the clinical significances of TLSs in prognosis and treatment response, as well as the status of TLS-directed therapies targeting alternative biochemical pathways in various central nervous system (CNS) disorders. Potential molecular mechanisms underlying the development of TLSs are also discussed. Exploring these areas may provide an essential understanding of the processes behind disease advancement, uncover new therapeutic objectives, and detect biomarkers that forecast disease progression and treatment efficacy.

Lymphotoxins from distinct types of lymphoid cells differentially contribute to neuroinflammation

Lymphotoxin α and lymphotoxin β (LTs), TNF superfamily members, are expressed in either soluble (LTα3) or membrane-bound (LTα1β2 or LTα2β1) forms. In the pathological context, LT-mediated signaling is known to exacerbate autoimmunity by perpetuating inflammation and promoting the formation of tertiary lymphoid organs. Despite this understanding, the exact roles of LTα and LTβ in the pathogenesis of the murine model of multiple sclerosis, and experimental autoimmune encephalomyelitis (EAE), remain controversial. Here, we employed a panel of gene-modified mice with cell-type restricted ablation of LTα (targeting both membrane-bound and soluble forms of LTs) to unravel the contributions of LTs from various lymphoid cells, namely T cells, type 3 innate lymphoid cells (ILC3) and B cells, in EAE. We found that the effects of LTα deletion were dependent on the cellular source. ILC3-derived lymphotoxins exerted a protective role in EAE by regulating the accumulation of IFN-ɣ- and GM-CSF-producing TH cells in the CNS. In contrast, T-cell-derived lymphotoxins promoted IL-17A- and GM-CSF-mediated TH responses in the periphery, whereas B-cell-derived lymphotoxins were pathogenic only in the autoantibody-mediated EAE model. Collectively, our findings unveil the multifaceted involvement of lymphotoxins in EAE pathogenesis and challenge the view that lymphotoxins play a solely pathogenic role in neuroinflammation.

The role of dendritic cells in tertiary lymphoid structures: implications in cancer and autoimmune diseases

Tertiary Lymphoid Structures (TLS) are organized aggregates of immune cells such as T cells, B cells, and Dendritic Cells (DCs), as well as fibroblasts, formed postnatally in response to signals from cytokines and chemokines. Central to the function of TLS are DCs, professional antigen-presenting cells (APCs) that coordinate the adaptive immune response, and which can be classified into different subsets, with specific functions, and markers. In this article, we review current data on the contribution of different DC subsets to TLS function in cancer and autoimmunity, two opposite sides of the immune response. Different DC subsets can be found in different tumor types, correlating with cancer prognosis. Moreover, DCs are also present in TLS found in autoimmune and inflammatory conditions, contributing to disease development. Broadly, the presence of DCs in TLS appears to be associated with favorable clinical outcomes in cancer while in autoimmune pathologies these cells are associated with unfavorable prognosis. Therefore, it is important to analyze the complex functions of DCs within TLS in order to enhance our fundamental understanding of immune regulation but also as a possible route to create innovative clinical interventions designed for the specific needs of patients with diverse pathological diseases.

LUBAC enables tumor-promoting LTβ receptor signaling by activating canonical NF-κB

Lymphotoxin β receptor (LTβR), a member of the TNF receptor superfamily (TNFR-SF), is essential for development and maturation of lymphoid organs. In addition, LTβR activation promotes carcinogenesis by inducing a proinflammatory secretome. Yet, we currently lack a detailed understanding of LTβR signaling. In this study we discovered the linear ubiquitin chain assembly complex (LUBAC) as a previously unrecognized and functionally crucial component of the native LTβR signaling complex (LTβR-SC). Mechanistically, LUBAC-generated linear ubiquitin chains enable recruitment of NEMO, OPTN and A20 to the LTβR-SC, where they act coordinately to regulate the balance between canonical and non-canonical NF-κB pathways. Thus, different from death receptor signaling, where LUBAC prevents inflammation through inhibition of cell death, in LTβR signaling LUBAC is required for inflammatory signaling by enabling canonical and interfering with non-canonical NF-κB activation. This results in a LUBAC-dependent LTβR-driven inflammatory, protumorigenic secretome. Intriguingly, in liver cancer patients with high LTβR expression, high expression of LUBAC correlates with poor prognosis, providing clinical relevance for LUBAC-mediated inflammatory LTβR signaling.

Single-cell and spatial transcriptome analyses reveal tertiary lymphoid structures linked to tumour progression and immunotherapy response in nasopharyngeal carcinoma

Tertiary lymphoid structures are immune cell aggregates linked with cancer outcomes, but their interactions with tumour cell aggregates are unclear. Using nasopharyngeal carcinoma as a model, here we analyse single-cell transcriptomes of 343,829 cells from 77 biopsy and blood samples and spatially-resolved transcriptomes of 31,316 spots from 15 tumours to decipher their components and interactions with tumour cell aggregates. We identify essential cell populations in tertiary lymphoid structure, including CXCL13+ cancer-associated fibroblasts, stem-like CXCL13+CD8+ T cells, and B and T follicular helper cells. Our study shows that germinal centre reaction matures plasma cells. These plasma cells intersperse with tumour cell aggregates, promoting apoptosis of EBV-related malignant cells and enhancing immunotherapy response. CXCL13+ cancer-associated fibroblasts promote B cell adhesion and antibody production, activating CXCL13+CD8+ T cells that become exhausted in tumour cell aggregates. Tertiary lymphoid structure-related cell signatures correlate with prognosis and PD-1 blockade response, offering insights for therapeutic strategies in cancers.

Characterization of cortico-meningeal translocator protein expression in multiple sclerosis

Compartmentalized meningeal inflammation is thought to represent one of the key players in the pathogenesis of cortical demyelination in multiple sclerosis. PET targeting the 18 kDa mitochondrial translocator protein (TSPO) is a molecular-specific approach to quantifying immune cell-mediated density in the cortico-meningeal tissue compartment in vivo. This study aimed to characterize cortical and meningeal TSPO expression in a heterogeneous cohort of multiple sclerosis cases using in vivo simultaneous MR-PET with 11C-PBR28, a second-generation TSPO radioligand, and ex vivo immunohistochemistry. Forty-nine multiple sclerosis patients (21 with secondary progressive and 28 with relapsing-remitting multiple sclerosis) with mixed or high affinity binding for 11C-PBR28 underwent 90-min 11C-PBR28 simultaneous MR-PET. Tracer binding was measured using 60-90 min normalized standardized uptake value ratios sampled at mid-cortical depth and ∼3 mm above the pial surface. Data in multiple sclerosis patients were compared to 21 age-matched healthy controls. To characterize the nature of 11C-PBR28 PET uptake, the meningeal and cortical lesion cellular expression of TSPO was further described in post-mortem brain tissue from 20 cases with secondary progressive multiple sclerosis and five age-matched healthy donors. Relative to healthy controls, patients with multiple sclerosis exhibited abnormally increased TSPO signal in the cortex and meningeal tissue, diffusively in progressive disease and more localized in relapsing-remitting multiple sclerosis. In multiple sclerosis, increased meningeal TSPO levels were associated with increased Expanded Disability Status Scale scores (P = 0.007, by linear regression). Immunohistochemistry, validated using in situ sequencing analysis, revealed increased TSPO expression in the meninges and adjacent subpial cortical lesions of post-mortem secondary progressive multiple sclerosis cases relative to control tissue. In these cases, increased TSPO expression was related to meningeal inflammation. Translocator protein immunostaining was detected on meningeal MHC-class II+ macrophages and cortical-activated MHC-class II+ TMEM119+ microglia. In vivo arterial blood data and neuropathology showed that endothelial binding did not significantly account for increased TSPO cortico-meningeal expression in multiple sclerosis. Our findings support the use of TSPO-PET in multiple sclerosis for imaging in vivo inflammation in the cortico-meningeal brain tissue compartment and provide in vivo evidence implicating meningeal inflammation in the pathogenesis of the disease.

Myelin-reactive B cells exacerbate CD4+ T cell-driven CNS autoimmunity in an IL-23-dependent manner

B cells and T cells collaborate in multiple sclerosis (MS) pathogenesis. IgH[MOG] mice possess a B cell repertoire skewed to recognize myelin oligodendrocyte glycoprotein (MOG). Here, we show that upon immunization with the T cell-obligate autoantigen, MOG[35-55], IgH[MOG] mice develop rapid and exacerbated experimental autoimmune encephalomyelitis (EAE) relative to wildtype (WT) counterparts, characterized by aggregation of T and B cells in the IgH[MOG] meninges and by CD4+ T helper 17 (Th17) cells in the CNS. Production of the Th17 maintenance factor IL-23 is observed from IgH[MOG] CNS-infiltrating and meningeal B cells, and in vivo blockade of IL-23p19 attenuates disease severity in IgH[MOG] mice. In the CNS parenchyma and dura mater of IgH[MOG] mice, we observe an increased frequency of CD4+PD-1+CXCR5- T cells that share numerous characteristics with the recently described T peripheral helper (Tph) cell subset. Further, CNS-infiltrating B and Tph cells from IgH[MOG] mice show increased reactive oxygen species (ROS) production. Meningeal inflammation, Tph-like cell accumulation in the CNS and B/Tph cell production of ROS were all reduced upon p19 blockade. Altogether, MOG-specific B cells promote autoimmune inflammation of the CNS parenchyma and meninges in an IL-23-dependent manner.

Inflammation due to ocular surface homeostasis imbalance caused by pterygia: tear lymphotoxin-alpha study and a literature review

OBJECTIVE

To estimate the pterygium ocular surface state, and compare with healthy eyes and dry eyes. To investigate the inflammation due to pterygia growth by tear Lymphotoxin-alpha (LT α) test.

DESIGN

Prospective, single-center study.

PARTICIPANTS

400 patients, divided into 100 pterygium group, 100 mild dry eye group, 100 moderate dry eye group, and 100 age-and sex-matched normal controls.

METHODS

The non-invasive break-up time (NIBUT), tear meniscus height (TMH) test, corneal fluorescein staining (CFS), meibomian gland loss score (MGs), and lipid layer thickness (LLT) were evaluated in all patients. Pterygium status and ocular status in the pterygium group were collected. The tear LT α test was conducted in the pterygium patients group.

RESULT

Pterygium can affect the ocular surface, leading to decreased tear film stability. The TMH, NIBUT, CFS, MGs, and lipid layer thickness can provide insights into this phenomenon. The presence of pterygium can change the structure and condition of the ocular surface. Tear LT α testing shows an abnormal decrease in LT α levels in pterygium patients. This indicates an immune-inflammation microenvironment that causes tissue repair deficiency.

CONCLUSION

The dry eye triggered by the growth of pterygium may originate from the tear film instability due to pterygia. As an inflammatory index, LT α in the development of pterygium and the aggravation of dry eye patients can indicate that the ocular surface is in different inflammatory states. Future tear testing in LT α may be a potential indicator to assess the inflammatory status of the dry eye.

Delivery technologies for therapeutic targeting of fibronectin in autoimmunity and fibrosis applications

Fibronectin (FN) is a critical component of the extracellular matrix (ECM) contributing to various physiological processes, including tissue repair and immune response regulation. FN regulates various cellular functions such as adhesion, proliferation, migration, differentiation, and cytokine release. Alterations in FN expression, deposition, and molecular structure can profoundly impact its interaction with other ECM proteins, growth factors, cells, and associated signaling pathways, thus influencing the progress of diseases such as fibrosis and autoimmune disorders. Therefore, developing therapeutics that directly target FN or its interaction with cells and other ECM components can be an intriguing approach to address autoimmune and fibrosis pathogenesis.

Intra-abdominal transplantation of PLGA/PCL/M13 phage electrospun scaffold induces self-assembly of lymphoid tissue-like structure

Lymphoid organs are the main structural components of the immune system. In the current research, the mixture of poly lactic-co-glycolic acid (PLGA), polycaprolactone (PCL), and M13 phage or its RGD-modified form was used in the construction of a fibrillar scaffold using the electrospinning method. The constructs were transplanted intra-abdominally and examined for the formation of lymphoid-like tissues at different time intervals. The confocal and scanning electron microscopy demonstrate that M13 phage-containing scaffolds provide a suitable environment for lymph node-isolated fibroblasts. Morphological analysis demonstrate the formation of lymph node-like tissues in the M13 phage-containing scaffolds after transplantation. Histological analysis confirm both blood and lymph angiogenesis in the implanted construct and migration of inflammatory cells to the M13 phage-containing scaffolds. In addition, flow cytometry and immunohistochemistry analysis showed the homing and compartmentalization of dendritic cells (DCs), B and T lymphocytes within the PLGA/PCL/M13 phage-RGD based scaffolds and similar to what is seen in the mouse lymphoid tissues. It seems that the application of M13 phage could improve the generation of functional lymphoid tissues in the electrospun scaffolds and could be used for lymphoid tissue regeneration.

Dynamic fibroblast-immune interactions shape wound healing after brain injury

Fibroblasts coordinate the response to tissue injury, directing organ regeneration versus scarring. In the central nervous system (CNS), fibroblasts are uncommon cells enriched at tissue borders, and their molecular, cellular, and functional interactions after brain injury are poorly understood. Here we define the fibroblast response to sterile brain damage across time and space. Early pro-fibrotic myofibroblasts infiltrated CNS lesions and were functionally and spatially organized by fibroblast TGF β signaling, pro-fibrotic macrophages and microglia, and perilesional brain glia that activated TGF β via integrin α v β 8 . Early myofibroblasts subsequently transitioned into a variety of late states, including meningeal and lymphocyte-interactive fibroblasts that persisted long term. Interruption of this dynamic fibroblast-macrophage-glial coordination impaired brain wound healing and the resolution of neuroinflammation, disrupted generation of late de novo CNS lymphocyte niches, and increased mortality in a stroke model. This work highlights an unexpected role of fibroblasts as coordinate regulators of CNS healing and neuroinflammation after brain injury.

B cell depletion with anti-CD20 promotes neuroprotection in a BAFF-dependent manner in mice and humans

Anti-CD20 therapy to deplete B cells is highly efficacious in preventing new white matter lesions in patients with relapsing-remitting multiple sclerosis (RRMS), but its protective capacity against gray matter injury and axonal damage is unclear. In a passive experimental autoimmune encephalomyelitis (EAE) model whereby TH17 cells promote brain leptomeningeal immune cell aggregates, we found that anti-CD20 treatment effectively spared myelin content and prevented myeloid cell activation, oxidative damage, and mitochondrial stress in the subpial gray matter. Anti-CD20 treatment increased B cell survival factor (BAFF) in the serum, cerebrospinal fluid, and leptomeninges of mice with EAE. Although anti-CD20 prevented gray matter demyelination, axonal loss, and neuronal atrophy, co-treatment with anti-BAFF abrogated these benefits. Consistent with the murine studies, we observed that elevated BAFF concentrations after anti-CD20 treatment in patients with RRMS were associated with better clinical outcomes. Moreover, BAFF promoted survival of human neurons in vitro. Together, our data demonstrate that BAFF exerts beneficial functions in MS and EAE in the context of anti-CD20 treatment.

N6-Methyladenosine (m6A) Methylation Is Associated with the Immune Microenvironments in Acute Intracerebral Hemorrhage (ICH)

Researchers have recently found that N6-methyladenosine (m6A) is a type of internal posttranscriptional modification that is essential in mammalian mRNA. However, the features of m6A RNA methylation in acute intracerebral hemorrhage (ICH) remain unknown. To explore differential methylations and to discover their functions in acute ICH patients, we recruited three acute ICH patients, three healthy controls, and an additional three patients and healthy controls for validation. The m6A methylation levels in blood samples from the two groups were determined by ultrahigh-performance liquid chromatography coupled with triple quadruple mass spectrometry (UPLC-QQQ-MS). Methylated RNA immunoprecipitation sequencing (MeRIP-seq) was employed to identify differences in m6A modification, and the differentially expressed m6A-modified genes were confirmed by MeRIP-qPCR. We found no significant differences in the total m6A levels between the two groups but observed differential methylation peaks. Compared with the control group, the coding genes showing increased methylation following acute ICH were mostly involved in processes connected with osteoclast differentiation, the neurotrophin signaling pathway, and the spliceosome, whereas genes with reduced m6A modification levels after acute ICH were found to be involved in the B-cell and T-cell receptor signaling pathways. These results reveal that differentially m6A-modified genes may influence the immune microenvironments in acute ICH.

Long-term recruitment of peripheral immune cells to brain scars after a neonatal insult

Although brain scars in adults have been extensively studied, there is less data available regarding scar formation during the neonatal period, and the involvement of peripheral immune cells in this process remains unexplored in neonates. Using a murine model of neonatal hypoxic-ischemic encephalopathy (HIE) and confocal microscopy, we characterized the scarring process and examined the recruitment of peripheral immune cells to cortical and hippocampal scars for up to 1 year post-insult. Regional differences in scar formation were observed, including the presence of reticular fibrotic networks in the cortex and perivascular fibrosis in the hippocampus. We identified chemokines with chronically elevated levels in both regions and demonstrated, through a parabiosis-based strategy, the recruitment of lymphocytes, neutrophils, and monocyte-derived macrophages to the scars several weeks after the neonatal insult. After 1 year, however, neutrophils and lymphocytes were absent from the scars. Our data indicate that peripheral immune cells are transient components of HIE-induced brain scars, opening up new possibilities for late therapeutic interventions.

Translational and oncologic significance of tertiary lymphoid structures in pancreatic adenocarcinoma

Pancreatic adenocarcinoma (PDAC) is an aggressive tumor with poor survival and limited treatment options. PDAC resistance to immunotherapeutic strategies is multifactorial, but partially owed to an immunosuppressive tumor immune microenvironment (TiME). However, the PDAC TiME is heterogeneous and harbors favorable tumor-infiltrating lymphocyte (TIL) populations. Tertiary lymphoid structures (TLS) are organized aggregates of immune cells that develop within non-lymphoid tissue under chronic inflammation in multiple contexts, including cancers. Our current understanding of their role within the PDAC TiME remains limited; TLS are complex structures with multiple anatomic features such as location, density, and maturity that may impact clinical outcomes such as survival and therapy response in PDAC. Similarly, our understanding of methods to manipulate TLS is an actively developing field of research. TLS may function as anti-tumoral immune niches that can be leveraged as a therapeutic strategy to potentiate both existing chemotherapeutic regimens and potentiate future immune-based therapeutic strategies to improve patient outcomes. This review seeks to cover anatomy, relevant features, immune effects, translational significance, and future directions of understanding TLS within the context of PDAC.

Evaluation of lymphotoxin-alpha in pterygium and diagnostic value in active and inactive pterygium states

To explore the correlation between tear LT-a, pterygium status, and dry eye indicators. We established a diagnostic model to evaluate active pterygium. A retrospective study was conducted between June 2021 and June 2023 on 172 patients, comprising 108 men and 64 women. The study analyzed LT-a and various ocular parameters in all participants. The data was collected using Excel software and analyzed using SPSS 25.0 statistical software and Medcalc. We made a nomogram diagnostic model to different diagnosed the state of pterygium. This study found that pterygium has progressive eye surface damage during the active state. There was no significant difference in dry eye indicators between the two groups. However, the concentration of LT-a in the active group was significantly lower than that in the inactive group (P < 0.001). We observed that increased pterygium grade corresponded to a worse ocular surface condition. In addition, LT-a was significantly positively correlated with disease duration, but negatively correlated with age, pterygium size, active pterygium state, and LLT value. The optimal intercept value for evaluating active pterygium in Lt-a was ≤ 0.49 dg/ml. We screened three variables for evaluating active pterygium through Single and Multiple regression analysis: LT-a grading, pterygium size, and congestion score. Finally, we made a reliable diagnostic nomogram model. Pterygium development triggers immune inflammation. Our model based on LT-a identifies active pterygium for personalized treatment options and new research directions.

Molecular anatomy of adult mouse leptomeninges

Leptomeninges, consisting of the pia mater and arachnoid, form a connective tissue investment and barrier enclosure of the brain. The exact nature of leptomeningeal cells has long been debated. In this study, we identify five molecularly distinct fibroblast-like transcriptomes in cerebral leptomeninges; link them to anatomically distinct cell types of the pia, inner arachnoid, outer arachnoid barrier, and dural border layer; and contrast them to a sixth fibroblast-like transcriptome present in the choroid plexus and median eminence. Newly identified transcriptional markers enabled molecular characterization of cell types responsible for adherence of arachnoid layers to one another and for the arachnoid barrier. These markers also proved useful in identifying the molecular features of leptomeningeal development, injury, and repair that were preserved or changed after traumatic brain injury. Together, the findings highlight the value of identifying fibroblast transcriptional subsets and their cellular locations toward advancing the understanding of leptomeningeal physiology and pathology.

Heterogeneity of tertiary lymphoid structures in cancer

The success of immunotherapy approaches, such as immune checkpoint blockade and cellular immunotherapy with genetically modified lymphocytes, has firmly embedded the immune system in the roadmap for combating cancer. Unfortunately, the majority of cancer patients do not yet benefit from these therapeutic approaches, even when the prognostic relevance of the immune response in their tumor entity has been demonstrated. Therefore, there is a justified need to explore new strategies for inducing anti-tumor immunity. The recent connection between the formation of ectopic lymphoid aggregates at tumor sites and patient prognosis, along with an effective anti-tumor response, suggests that manipulating the occurrence of these tertiary lymphoid structures (TLS) may play a critical role in activating the immune system against a growing tumor. However, mechanisms governing TLS formation and a clear understanding of their substantial heterogeneity are still lacking. Here, we briefly summarize the current state of knowledge regarding the mechanisms driving TLS development, outline the impact of TLS heterogeneity on clinical outcomes in cancer patients, and discuss appropriate systems for modeling TLS heterogeneity that may help identify new strategies for inducing protective TLS formation in cancer patients.

CCL5 promotes LFA-1 expression in Th17 cells and induces LCK and ZAP70 activation in a mouse model of Parkinson's disease

Background

Parkinson's disease (PD), which is associated to autoimmune disorders, is characterized by the pathological deposition of alpha-synuclein (α-Syn) and loss of dopaminergic (DA) neurons. Th17 cells are thought to be responsible for the direct loss of DA neurons. C-C chemokine ligand 5 (CCL5) specifically induces Th17 cell infiltration into the SN. However, the specific effect of CCL5 on Th17 cells in PD and the relationship between CCL5 and lymphocyte function-associated antigen-1 (LFA-1) expression in Th17 cells are unknown.

Methods

We evaluated the effects of CCL5 on LFA-1 expression in Th17 cells in mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and examined Th17 cell differentiation upon CCL5 stimulation in vitro. Furthermore, we assessed the effects of CCL5 on tyrosine kinase zeta-chain-associated protein kinase 70 (ZAP70) and lymphocyte-specific protein tyrosine kinase (LCK) activity in CCL5-stimulated Th17 cells in vivo and in vitro.

Results

CCL5 increased the proportion of peripheral Th17 cells in MPTP-treated mice, LFA-1 expression on Th17 cells, and Th17 cell levels in the SN of MPTP-treated mice. CCL5 promoted Th17 cell differentiation and LFA-1 expression in naive T cells in vitro. Moreover, CCL5 increased Th17 cell differentiation and LFA-1 expression by stimulating LCK and ZAP70 activation in naive CD4+ T cells. Inhibiting LCK and ZAP70 activation reduced the proportion of peripheral Th17 cells and LFA-1 surface expression in MPTP-treated mice, and Th17 cell levels in the SN also significantly decreased.

Conclusion

CCL5, which increased Th17 cell differentiation and LFA-1 protein expression by activating LCK and ZAP70, could increase the Th17 cell number in the SN, induce DA neuron death and aggravate PD.

Association of MRI leptomeningeal enhancement with disability worsening in progressive multiple sclerosis: A clinical and post-mortem study

BACKGROUND

Leptomeningeal enhancement (LME) has been described as a biomarker of meningeal inflammation in multiple sclerosis (MS).

OBJECTIVE

The aim of this study was to (1) assess if LME is predictive of disability worsening in progressive MS (pMS) patients and (2) investigate the pathological substrates of LME in an independent post-mortem MS series.

METHODS

In total, 115 pMS patients were imaged yearly with 1.5T MRI, using post-contrast CUBE 3D FLAIR for LME detection. Endpoint: to identify the baseline variables predictive of confirmed disability worsening (CDW) at 24 months follow-up. Post-mortem, inflammation, and structural changes of the leptomeninges were assessed in 12 MS/8 control brains.

RESULTS

LME (27% of patients at baseline) was associated with higher EDSS and lower brain volume (nBV). LME was unchanged in most patients over follow-up. LME at baseline MRI was independently associated with higher risk of 24 months CDW (HR 3.05, 95% CI 1.36-6.84, p = 0.007) in a Cox regression, including age, nBV, T2 lesion volume, high-efficacy treatments, and MRI disease activity. Post-mortem, focal structural changes (fibrosis) of the leptomeninges were observed in MS, usually associated with inflammation (Kendall's Tau 0.315, p < 0.0001).

CONCLUSIONS

LME is frequently detected in pMS patients using 1.5T MRI and is independently predictive of disability progression. LME could result from both focal leptomeningeal post-inflammatory fibrosis and inflammation.

Proteomic interrogation of the meninges reveals the molecular identities of structural components and regional distinctions along the CNS axis

The meninges surround the brain and spinal cord, affording physical protection while also serving as a niche of neuroimmune activity. Though possessing stromal qualities, its complex cellular and extracellular makeup has yet to be elaborated, and it remains unclear whether the meninges vary along the neuroaxis. Hence, studies were carried-out to elucidate the protein composition and structural organization of brain and spinal cord meninges in normal, adult Biozzi ABH mice. First, shotgun, bottom-up proteomics was carried-out. Prominent proteins at both brain and spinal levels included Type II collagen and Type II keratins, representing extracellular matrix (ECM) and cytoskeletal categories, respectively. While the vast majority of total proteins detected was shared between both meningeal locales, more were uniquely detected in brain than in spine. This pattern was also seen when total proteins were subdivided by cellular compartment, except in the case of the ECM category where brain and spinal meninges each had near equal number of unique proteins, and Type V and type III collagen registered exclusively in the spine. Quantitative analysis revealed differential expression of several collagens and cytoskeletal proteins between brain and spinal meninges. High-resolution immunofluorescence and immunogold-scanning electronmicroscopy on sections from whole brain and spinal cord - still encased within bone -identified major proteins detected by proteomics, and highlighted their association with cellular and extracellular elements of variously shaped arachnoid trabeculae. Western blotting aligned with the proteomic and immunohistological analyses, reinforcing differential appearance of proteins in brain vs spinal meninges. Results could reflect regional distinctions in meninges that govern protective and/or neuroimmune functions.

Tertiary Lymphoid Structures Are Related to Inflammatory Progression and Bone Loss in Human Apical Periodontitis

INTRODUCTION

Bone loss is strongly associated with the immunologic milieu in apical periodontitis (AP). Tertiary lymphoid structures (TLSs) are organized lymphoid cell aggregates that form in nonlymphoid tissues under persistent inflammatory circumstances. To date, there has been no relevant report of TLSs in periapical lesions. This work aimed to investigate the formation and potential function of TLSs in AP.

METHODS

Tissues from human apical lesions (n = 61) and healthy oral mucosa (n = 5) were collected. Immunohistochemistry and multiplex immunofluorescence were used to detect the formation of TLSs. Correlation analyses were performed between clinical variables and TLSs. In addition, immunohistochemistry was used to evaluate the expression of interleukin-1 beta, interleukin-6, receptor activator of nuclear factor kappa-B ligand, and macrophage subsets in the apical lesions.

RESULTS

Periapical granulomas (n = 24) and cysts (n = 37) were identified by histologic evaluation. TLSs, composed of B-cell and T-cell clusters, developed in periapical granulomas and radicular cysts. The CXC-chemokine ligand 13, its receptor CXC-chemokine receptor 5, follicular dendritic cells, and high endothelial venules were localized in TLSs. The quantity and size of TLSs were positively associated with bone loss in AP. Moreover, proinflammatory cytokines and macrophage subsets were also substantially elevated in TLS regions of apical lesions.

CONCLUSIONS

The formation of TLSs in periapical granulomas and cysts was closely associated with persistent immune responses and bone loss in apical lesions. TLSs provide an updated insight into the complicated immune response process in AP.

Pulmonary inflammation and fibroblast immunoregulation: from bench to bedside

In recent years, there has been an explosion of interest in how fibroblasts initiate, sustain, and resolve inflammation across disease states. Fibroblasts contain heterogeneous subsets with diverse functionality. The phenotypes of these populations vary depending on their spatial distribution within the tissue and the immunopathologic cues contributing to disease progression. In addition to their roles in structurally supporting organs and remodeling tissue, fibroblasts mediate critical interactions with diverse immune cells. These interactions have important implications for defining mechanisms of disease and identifying potential therapeutic targets. Fibroblasts in the respiratory tract, in particular, determine the severity and outcome of numerous acute and chronic lung diseases, including asthma, chronic obstructive pulmonary disease, acute respiratory distress syndrome, and idiopathic pulmonary fibrosis. Here, we review recent studies defining the spatiotemporal identity of the lung-derived fibroblasts and the mechanisms by which these subsets regulate immune responses to insult exposures and highlight past, current, and future therapeutic targets with relevance to fibroblast biology in the context of acute and chronic human respiratory diseases. This perspective highlights the importance of tissue context in defining fibroblast-immune crosstalk and paves the way for identifying therapeutic approaches to benefit patients with acute and chronic pulmonary disorders.

T cells in health and disease

T cells are crucial for immune functions to maintain health and prevent disease. T cell development occurs in a stepwise process in the thymus and mainly generates CD4+ and CD8+ T cell subsets. Upon antigen stimulation, naïve T cells differentiate into CD4+ helper and CD8+ cytotoxic effector and memory cells, mediating direct killing, diverse immune regulatory function, and long-term protection. In response to acute and chronic infections and tumors, T cells adopt distinct differentiation trajectories and develop into a range of heterogeneous populations with various phenotype, differentiation potential, and functionality under precise and elaborate regulations of transcriptional and epigenetic programs. Abnormal T-cell immunity can initiate and promote the pathogenesis of autoimmune diseases. In this review, we summarize the current understanding of T cell development, CD4+ and CD8+ T cell classification, and differentiation in physiological settings. We further elaborate the heterogeneity, differentiation, functionality, and regulation network of CD4+ and CD8+ T cells in infectious disease, chronic infection and tumor, and autoimmune disease, highlighting the exhausted CD8+ T cell differentiation trajectory, CD4+ T cell helper function, T cell contributions to immunotherapy and autoimmune pathogenesis. We also discuss the development and function of γδ T cells in tissue surveillance, infection, and tumor immunity. Finally, we summarized current T-cell-based immunotherapies in both cancer and autoimmune diseases, with an emphasis on their clinical applications. A better understanding of T cell immunity provides insight into developing novel prophylactic and therapeutic strategies in human diseases.

Inflammation and immunomodulation in central nervous system injury - B cells as a novel therapeutic opportunity

Acute injury to the central nervous system (CNS) remains a complex and challenging clinical need. CNS injury initiates a dynamic neuroinflammatory response, mediated by both resident and infiltrating immune cells. Following the primary injury, dysregulated inflammatory cascades have been implicated in sustaining a pro-inflammatory microenvironment, driving secondary neurodegeneration and the development of lasting neurological dysfunction. Due to the multifaceted nature of CNS injury, clinically effective therapies for conditions such as traumatic brain injury (TBI), spinal cord injury (SCI), and stroke have proven challenging to develop. No therapeutics that adequately address the chronic inflammatory component of secondary CNS injury are currently available. Recently, B lymphocytes have gained increasing appreciation for their role in maintaining immune homeostasis and regulating inflammatory responses in the context of tissue injury. Here we review the neuroinflammatory response to CNS injury with particular focus on the underexplored role of B cells and summarize recent results on the use of purified B lymphocytes as a novel immunomodulatory therapeutic for tissue injury, particularly in the CNS.

The roles of tertiary lymphoid structures in chronic diseases

Tertiary lymphoid structures (TLSs) are ectopic lymphoid tissues that drive antigen-specific immune responses at sites of chronic inflammation. Unlike secondary lymphoid organs such as lymph nodes, TLSs lack capsules and have their own unique characteristics and functions. The presumed influence of TLSs on the disease course has led to widespread interest in obtaining a better understanding of their biology and function. Studies using single-cell analyses have suggested heterogeneity in TLS composition and phenotype, and consequently, functional correlates with disease progression are sometimes conflicting. The presence of TLSs correlates with a favourable disease course in cancer and infection. Conversely, in autoimmune diseases and chronic age-related inflammatory diseases including chronic kidney disease, the presence of TLSs is associated with a more severe disease course. However, the detailed mechanisms that underlie these clinical associations are not fully understood. To what extent the mechanisms of TLS development and maturation are shared across organs and diseases is also still obscure. Improved understanding of TLS development and function at the cellular and molecular levels may enable the exploitation of these structures to improve therapies for chronic diseases, including chronic kidney disease.

The presence of cerebellar B cell aggregates is associated with a specific chemokine profile in the cerebrospinal fluid in a mouse model of multiple sclerosis

BACKGROUND

The presence of meningeal ectopic lymphoid structures (ELS) in a subgroup of patients diagnosed with secondary progressive multiple sclerosis (SPMS) corresponds to a pronounced cortical inflammation and an aggravated disease course. In MP4-induced experimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclerosis (MS), B cell aggregates develop in the central nervous system (CNS) in the chronic stage of the disease. Therefore, the model is suitable for studying key molecules of ELS development and maintenance. Here, we investigated whether there is a specific cytokine and chemokine signature in paired cerebrospinal fluid (CSF) and serum samples associated with the presence of cerebellar B cell and T cell pathology and B cell aggregates of MP4-immunized mice.

METHODS

Paired CSF and serum samples were collected from the cisterna magna and periphery of MP4-immunized mice at the chronic stage of disease. A control group with mice immunized only with the adjuvant (vehicle) was included in the study. A selected panel of 34 cytokines and chemokines were measured by MAGPIX® for both cohorts. For the assessment of B cell and T cell infiltration, immunohistochemical staining was performed and analyzed using light microscopy. To detect specific chemokine receptors additional staining was conducted.

RESULTS

While we detected several upregulated cytokines and chemokines in the CSF of MP4-immunized mice independent of the extent of B cell and T cell pathology compared to vehicle-immunized mice, C-C motif chemokine ligand (CCL)-1 was associated with high B cell and T cell infiltration. Furthermore, the level of certain chemokines, including CCL1, CCL5, CCL7, CCL12, CCL22 and C-X-C motif chemokine ligand (CXCL)-13, was significantly increased (p < 0.05) in MP4-immunized mice showing a high number of B cell aggregates. While C-C motif chemokine receptor (CCR)5 had a ubiquitous expression independent of the extent of B cell and T cell pathology, C-X-C motif chemokine receptor (CXCR)-5 and CXCR6 expression was specifically associated with high B cell and T cell pathology.

CONCLUSION

Our data suggest that multiple cytokines and chemokines are involved in the pathophysiology of MP4-induced EAE. Furthermore, the presence of B cell aggregates was associated with a specific chemokine profile in the CSF, which might be useful for predicting the presence of these aggregates without the necessity to histologically screen the CNS tissue.

The multisensory regulation of unconventional T cell homeostasis

Unconventional T cells typically group γδ T cells, invariant Natural Killer T cells (NKT) and Mucosal Associated Invariant T (MAIT) cells. With their pre-activated status and biased tropism for non-lymphoid organs, they provide a rapid (innate-like) and efficient first line of defense against pathogens at strategical barrier sites, while they can also trigger chronic inflammation, and unexpectedly contribute to steady state physiology. Thus, a tight control of their homeostasis is critical to maintain tissue integrity. In this review, we discuss the recent advances of our understanding of the factors, from neuroimmune to inflammatory regulators, shaping the size and functional properties of unconventional T cell subsets in non-lymphoid organs. We present a general overview of the mechanisms common to these populations, while also acknowledging specific aspects of their diversity. We mainly focus on their maintenance at steady state and upon inflammation, highlighting some key unresolved issues and raising upcoming technical, fundamental and translational challenges.

A Review of Compartmentalised Inflammation and Tertiary Lymphoid Structures in the Pathophysiology of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, immune-mediated, demyelinating disease of the central nervous system (CNS). The most common form of MS is a relapsing–remitting disease characterised by acute episodes of demyelination associated with the breakdown of the blood–brain barrier (BBB). In the relapsing–remitting phase there is often relative recovery (remission) from relapses characterised clinically by complete or partial resolution of neurological symptoms. In the later and progressive stages of the disease process, accrual of neurological disability occurs in a pathological process independent of acute episodes of demyelination and is accompanied by a trapped or compartmentalised inflammatory response, most notable in the connective tissue spaces of the vasculature and leptomeninges occurring behind an intact BBB. This review focuses on compartmentalised inflammation in MS and in particular, what we know about meningeal tertiary lymphoid structures (TLS; also called B cell follicles) which are organised clusters of immune cells, associated with more severe and progressive forms of MS. Meningeal inflammation and TLS could represent an important fluid or imaging marker of disease activity, whose therapeutic abrogation might be necessary to stop the most severe outcomes of disease.

Neuroinflammation: Extinguishing a blaze of T cells

Inflammation is a biological process that dynamically alters the surrounding microenvironment, including participating immune cells. As a well-protected organ surrounded by specialized barriers and with immune privilege properties, the central nervous system (CNS) tightly regulates immune responses. Yet in neuroinflammatory conditions, pathogenic immunity can disrupt CNS structure and function. T cells in particular play a key role in promoting and restricting neuroinflammatory responses, while the inflamed CNS microenvironment can influence and reshape T cell function and identity. Still, the contraction of aberrant T cell responses within the CNS is not well understood. Using autoimmunity as a model, here we address the contribution of CD4 T helper (Th) cell subsets in promoting neuropathology and disease. To address the mechanisms antagonizing neuroinflammation, we focus on the control of the immune response by regulatory T cells (Tregs) and describe the counteracting processes that preserve their identity under inflammatory challenges. Finally, given the influence of the local microenvironment on immune regulation, we address how CNS-intrinsic signals reshape T cell function to mitigate abnormal immune T cell responses.

New insight into DAVF pathology—Clues from meningeal immunity

In recent years, with the current access in techniques, studies have significantly advanced the knowledge on meningeal immunity, revealing that the central nervous system (CNS) border acts as an immune landscape. The latest concept of meningeal immune system is a tertiary structure, which is a comprehensive overview of the meningeal immune system from macro to micro. We comprehensively reviewed recent advances in meningeal immunity, particularly the new understanding of the dural sinus and meningeal lymphatics. Moreover, based on the clues from the meningeal immunity, new insights were proposed into the dural arteriovenous fistula (DAVF) pathology, aiming to provide novel ideas for DAVF understanding.

CXCL13-CXCR5 axis: Regulation in inflammatory diseases and cancer

Chemokine C-X-C motif ligand 13 (CXCL13), originally identified as a B-cell chemokine, plays an important role in the immune system. The interaction between CXCL13 and its receptor, the G-protein coupled receptor (GPCR) CXCR5, builds a signaling network that regulates not only normal organisms but also the development of many diseases. However, the precise action mechanism remains unclear. In this review, we discussed the functional mechanisms of the CXCL13-CXCR5 axis under normal conditions, with special focus on its association with diseases. For certain refractory diseases, we emphasize the diagnostic and therapeutic role of CXCL13-CXCR5 axis.

The gut-immune-brain axis in neurodevelopment and neurological disorders

The gut-brain axis is gaining momentum as an interdisciplinary field addressing how intestinal microbes influence the central nervous system (CNS). Studies using powerful tools, including germ-free, antibiotic-fed, and fecal microbiota transplanted mice, demonstrate how gut microbiota perturbations alter the fate of neurodevelopment. Probiotics are also becoming more recognized as potentially effective therapeutic agents in alleviating symptoms of neurological disorders. While gut microbes may directly communicate with the CNS through their effector molecules, including metabolites, their influence on neuroimmune populations, including newly discovered brain-resident T cells, underscore the host immunity as a potent mediator of the gut-brain axis. In this review, we examine the unique immune populations within the brain, the effects of the gut microbiota on the CNS, and the efficacy of specific probiotic strains to propose the novel concept of the gut-immune-brain axis.

The role of neutrophils in the dysfunction of central nervous system barriers

Leukocyte migration into the central nervous system (CNS) represents a central process in the development of neurological diseases with a detrimental inflammatory component. Infiltrating neutrophils have been detected inside the brain of patients with several neuroinflammatory disorders, including stroke, multiple sclerosis and Alzheimer’s disease. During inflammatory responses, these highly reactive innate immune cells can rapidly extravasate and release a plethora of pro-inflammatory and cytotoxic factors, potentially inducing significant collateral tissue damage. Indeed, several studies have shown that neutrophils promote blood-brain barrier damage and increased vascular permeability during neuroinflammatory diseases. Recent studies have shown that neutrophils migrate into the meninges and choroid plexus, suggesting these cells can also damage the blood-cerebrospinal fluid barrier (BCSFB). In this review, we discuss the emerging role of neutrophils in the dysfunction of brain barriers across different neuroinflammatory conditions and describe the molecular basis and cellular interplays involved in neutrophil-mediated injury of the CNS borders.