Natural killer cells in multiple sclerosis: A review

Epstein-Barr virus-encoded BART9 and BART15 miRNAs are elevated in exosomes of cerebrospinal fluid from relapsing-remitting multiple sclerosis patients

Epstein-Barr virus (EBV) infection is approved as the main environmental trigger of multiple sclerosis (MS). In this path, we quantified ebv-miR-BART9-3p and ebv-miR-BART15 in exosomes of cerebrospinal fluid (CSF) of untreated relapsing-remitting MS (RRMS) patients in comparison with the control group. Interestingly, patients displayed significant upregulation of ebv-miR-BART9-3p (18.4-fold) and ebv-miR-BART15 (3.1-fold) expression in CSF exosomes. Moreover, the expression levels of hsa-miR-21-5p and hsa-miR-146a-5p were found to be significantly elevated in the CSF samples obtained from the patient group compared to those obtained from the HC group. The levels of Interferon-gamma (IFN-γ), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-17 (IL-17), interleukin-23 (IL-23), transforming growth factor beta (TGF-β), and tumor necrosis factor-alpha (TNF-α) were observed to be significantly elevated in the serum and CSF exosomes of the patients. The highest increase was observed in TGF-β (8.5-fold), followed by IL-23 (3.9-fold) in CSF exosomes. These findings are in agreement with the association between EBV infection and inflammatory cytokines induction. Furthermore, the ratios of TGF-β: TNF-α and TGF-β: IFN-γ attained values of 4 to 16.4 and 1.3 to 3.6, respectively, in the CSF exosomes of the patients, in comparison to those of the control group. These findings show EBV activity in RRMS patients is different from that of healthy ones. Elevation of ebv-miR-BART9-3p, ebv-miR-BART15, and inflammatory cytokines expression in CSF exosomes in RRMS patients provides a substantial link between EBV activity and the onset of the disease, as well as the transition from EBV infection to MS.

Pregnant Women with Multiple Sclerosis: An Overview of Gene Expression and Molecular Interaction Using Bioinformatics Analysis

Multiple sclerosis (MS) is a common disease in young women of reproductive age, characterized by demyelination of the central nervous system (CNS). Understanding how genes related to MS are expressed during pregnancy can provide insights into the potential mechanisms by which pregnancy affects the course of this disease. This review article presents evidence-based studies on these patients' gene expression patterns. In addition, it constructs interaction networks using bioinformatics tools, such as STRING and KEGG pathways, to understand the molecular role of each of these genes. Bioinformatics research identified 25 genes and 21 signaling pathways, which allows us to understand pregnancy patients' genetic and biological phenomena and formulate new questions about MS during pregnancy.

Viral-mediated inflammation by Poly I:C induces the chemokine CCL5 in NK cells and its receptors CCR1 and CCR5 in microglia in the neonatal rat cerebellum

Objectives

To study the effect of viral inflammation induced by Polyinosinic:polycytidylic acid (PIC) on the cerebellum during a critical period of development in rats.

Methods

Neonatal rat pups were treated with PIC on postnatal days (PN) 8 and 10 after which we quantified RNA using Nanostring, qRT-PCR and RNAscope and analyzed immune cells through flow cytometry and immunohistochemistry on PN11. Using the same paradigm, we also analyzed play juvenile behavior, anxiety-like behavior, motor balance using the balance beam and the rotarod assays as well as fine motor behavior using the sunflower seed opening test.

Results

We determined that male and female pups treated with PIC reacted with a significant increase in CCL5, a chemotactic cytokine that attracts T-cells, eosinophils and basophils to the site of inflammation, at PN11. PIC treatment also increased the expression of two receptors for CCL5, CCR1 and CCR5 in the cerebellar vermis in both males and females at PN11. In-situ hybridization (RNAscope®) for specific transcripts revealed that microglia express both CCL5 receptors under inflammatory and non-inflammatory conditions in both males and females. PIC treatment also increased the total number of CCL5+ cells in the developing cerebellum which were determined to be both natural killer cells and T-cells. There were modest but significant impacts of PIC treatment on large and fine motor skills and juvenile play behavior.

Conclusions

Our findings suggest an important role for CCL5 and other immune cells in mediating inflammation in the developing cerebellum that potentially impact the maturation of cerebellar neurons during a critical period of development.

The ratio of circulating CD56dim NK cells to follicular T helper cells as a promising predictor for disease activity of relapsing-remitting multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system primarily mediated by CD4+ T helper cells. This study investigated the dynamic changes of natural killer (NK) cells and follicular T helper (Tfh) cells and their associations in relapsing-remitting MS patients. The findings revealed inverse relationships between NK cells and CD4+ T cells or Tfh cells. Specifically, CD56dim NK cells, not CD56bright NK cells, were negatively correlated with CD4+ T cells and Tfh cells. However, no significant correlations were found between NK cells and sNfL levels or EDSS scores. The ratio of CD56dim NK cells to circulating Tfh (cTfh) cells demonstrated superior discriminatory ability in distinguishing relapsing MS patients from healthy controls (HCs) and remitting patients, as determined by receiver operating characteristic (ROC) analysis. Following treatment with immunosuppressants or disease-modifying therapies (DMTs), a significant increase in the CD56dim NK/cTfh ratio was observed. These findings suggest that the CD56dim NK/cTfh ratio holds promise as a prognostic indicator for clinical relapse and treatment response in MS.

Immunophenotyping in routine clinical practice for predicting treatment response and adverse events in patients with MS

Background

Recent studies proposed cellular immunoprofiling as a surrogate for predicting treatment response and/or stratifying the occurrence of adverse events (AEs) in persons with multiple sclerosis (pwMS). However, applicability in real-world circumstances is not sufficiently addressed.

Objective

We aimed to explore whether standard routine clinical leukocyte phenotyping before treatment initiation could help stratify patients according to treatment response or AEs in a real-world MS cohort.

Methods

In this retrospective study, 150 pwMS were included, who had been newly initiated on a disease-modifying drug (DMD) and had been assessed for standard immunophenotyping before DMD initiation (baseline) and at least once during the following year. Multivariate models were used to assess an association of immune subsets and the association between immune cell profiles regarding treatment response and AEs.

Results

We found that the composition of T cell subsets was associated with relapse activity, as an increased proportion of CD8+ lymphocytes at baseline indicated a higher likelihood of subsequent relapse (about 9% per 1% increase in CD8+ proportion of all CD3+ cells). This was particularly driven by patients receiving anti-CD20 therapy, where also EDSS worsening was associated with a higher number of CD8+ cells at baseline (3% increase per 10 cells). In the overall cohort, an increase in the proportion of NK cells was associated with a higher risk of EDSS worsening (5% per 1% increase). Occurrence of AEs was associated with a higher percentage of T cells and a lower number of percentual NKT cells at baseline.

Conclusion

Immune cell profiles are associated with treatment response and the occurrence of AEs in pwMS. Hence, immunophenotyping may serve as a valuable biomarker to enable individually tailored treatment strategies in pwMS.

The Smoothened agonist SAG Modulates the Male and Female Peripheral Immune Systems Differently in an Immune Model of Central Nervous System Demyelination

Both Hedgehog and androgen signaling pathways are known to promote myelin regeneration in the central nervous system. Remarkably, the combined administration of agonists of each pathway revealed their functional cooperation towards higher regeneration in demyelination models in males. Since multiple sclerosis, the most common demyelinating disease, predominates in women, and androgen effects were reported to diverge according to sex, it seemed essential to assess the existence of such cooperation in females. Here, we developed an intranasal formulation containing the Hedgehog signaling agonist SAG, either alone or in combination with testosterone. We show that SAG promotes myelin regeneration and presumably a pro-regenerative phenotype of microglia, thus mimicking the effects previously observed in males. However, unlike in males, the combined molecules failed to cooperate in the demyelinated females, as shown by the level of functional improvement observed. Consistent with this observation, SAG administered in the absence of testosterone amplified peripheral inflammation by presumably activating NK cells and thus counteracting a testosterone-induced reduction in Th17 cells when the molecules were combined. Altogether, the data uncover a sex-dependent effect of the Hedgehog signaling agonist SAG on the peripheral innate immune system that conditions its ability to cooperate or not with androgens in the context of demyelination.

Relapsing-remitting multiple sclerosis patients exhibit differential natural killer functional subpopulations

BACKGROUND

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) and has been known as T-cell mediated. However, the contribution of multiple cell types, notably natural killer (NK) cells, has also been reported.

AIM

To quantify circulating total NK cells and its subpopulations, CD56 dim and bright, and to characterize the functional phenotype and IFN-γ and TNF-α production in relapsing-remitting patients treated with IFN-β and in apparently healthy controls.

RESULTS

CD56bright NK cells were found to be the least represented subpopulation. In relapse patients, the frequencies of IFN-γ-producing NK cells and their subpopulations were significantly decreased. In remission patients, CD56dim NK cells expressed high levels of HLA-DR and CD54.

CONCLUSION

These results suggest that remission RRMS patients, although in an inactive stage of MS, present circulating NK cells with an activation phenotype, supporting the idea that NK cells may be relevant mediators in the MS pathophysiology.

The role of CD56bright NK cells in neurodegenerative disorders

Emerging evidence suggests a potential role for natural killer (NK) cells in neurodegenerative diseases, such as multiple sclerosis, Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. However, the precise function of NK cells in these diseases remains ambiguous. The existence of two NK cell subsets, CD56bright and CD56dim NK cells, complicates the understanding of the contribution of NK cells in neurodegeneration as their functions within the context of neurodegenerative diseases may differ significantly. CD56bright NK cells are potent cytokine secretors and are considered more immunoregulatory and less terminally differentiated than their mostly cytotoxic CD56dim counterparts. Hence, this review focusses on NK cells, specifically on CD56bright NK cells, and their role in neurodegenerative diseases. Moreover, it explores the mechanisms underlying their ability to enter the central nervous system. By consolidating current knowledge, we aim to provide a comprehensive overview on the role of CD56bright NK cells in neurodegenerative diseases. Elucidating their impact on neurodegeneration may have implications for future therapeutic interventions, potentially ameliorating disease pathogenesis.

The Plasticity of Immune Cell Response Complicates Dissecting the Underlying Pathology of Multiple Sclerosis

Multiple sclerosis (MS) is a neurodegenerative autoimmune disease characterized by the destruction of the myelin sheath of the neuronal axon in the central nervous system. Many risk factors, including environmental, epigenetic, genetic, and lifestyle factors, are responsible for the development of MS. It has long been thought that only adaptive immune cells, especially autoreactive T cells, are responsible for the pathophysiology; however, recent evidence has indicated that innate immune cells are also highly involved in disease initiation and progression. Here, we compile the available data regarding the role immune cells play in MS, drawn from both human and animal research. While T and B lymphocytes, chiefly enhance MS pathology, regulatory T cells (Tregs) may serve a more protective role, as can B cells, depending on context and location. Cells chiefly involved in innate immunity, including macrophages, microglia, astrocytes, dendritic cells, natural killer (NK) cells, eosinophils, and mast cells, play varied roles. In addition, there is evidence regarding the involvement of innate-like immune cells, such as γδ T cells, NKT cells, MAIT cells, and innate-like B cells as crucial contributors to MS pathophysiology. It is unclear which of these cell subsets are involved in the onset or progression of disease or in protective mechanisms due to their plastic nature, which can change their properties and functions depending on microenvironmental exposure and the response of neural networks in damage control. This highlights the need for a multipronged approach, combining stringently designed clinical data with carefully controlled in vitro and in vivo research findings, to identify the underlying mechanisms so that more effective therapeutics can be developed.

Progress in Mechanism of Astragalus membranaceus and Its Chemical Constituents on Multiple Sclerosis

The primary chemical components of Astragalus membranaceus include polysaccharides, saponins, flavonoids, and amino acids. Recent studies have shown that Astragalus membranaceus has multiple functions, including improving immune function and exerting antioxidative, anti-radiation, anti-tumor, antibacterial, antiviral, and hormone-like effects. Astragalus membranaceus and its extracts are widely used in clinical practice because they have obvious therapeutic effects against various autoimmune diseases and relatively less adverse reaction. Multiple sclerosis (MS) is an autoimmune disease of central nervous system (CNS), which mainly caused by immune disorder that leads to inflammatory demyelination, inflammatory cell infiltration, and axonal degeneration in the CNS. In this review, the authors analyzed the clinical manifestations of MS and experimental autoimmune encephalomyelitis (EAE) and focused on the efficacy of Astragalus membranaceus and its chemical components in the treatment of MS/EAE.

Immunomodulatory role of vitamin D and selenium supplementation in newly diagnosed Graves' disease patients during methimazole treatment

Introduction

Methimazole (MMI) represents the conventional therapeutic agent for Graves' disease (GD) hyperthyroidism, but MMI efficacy is limited since it marginally affects the underlying autoimmune process. In a previous study, we randomly assigned 42 newly diagnosed GD patients with insufficient vitamin D (VitD) and selenium (Se) levels to treatment with MMI alone (standard) or combined with selenomethionine and cholecalciferol (intervention) and observed a prompter resolution of hyperthyroidism in the intervention group.

Methods

In the present study, we aimed to explore changes in peripheral T regulatory (Treg) and circulating natural killer (NK) cell frequency, circulating NK cell subset distribution and function, during treatment.

Results

At baseline, circulating total CD3^-CD56⁺NK cells and CD56^bright NK cells were significantly higher in GD patients than in healthy controls (HC) (15.7 ± 9.6% vs 9.9 ± 5.6%, p=0.001; 12.2 ± 10.3% vs 7.3 ± 4.1%, p=0.02, respectively); no differences emerged in Treg cell frequency. Frequencies of total NK cells and CD56^bright NK cells expressing the activation marker CD69 were significantly higher in GD patients than in HC, while total NK cells and CD56^dim NK cells expressing CD161 (inhibitory receptor) were significantly lower. When co-cultured with the K562 target cell, NK cells from GD patients had a significantly lower degranulation ability compared to HC (p<0.001). Following 6 months of treatment, NK cells decreased in both the intervention and MMI-alone groups, but significantly more in the intervention group (total NK: -10.3%, CI 95% -15.8; -4.8% vs -3.6%, CI 95% -9; 1.8%, p=0.09 and CD56^bright NK cells: -6.5%, CI 95% -10.1; -3 vs -0.9%, CI 95% -4.4; 2%, p=0.03). Compared to baseline, CD69⁺ NK cells significantly decreased, while degranulation ability slightly improved, although no differences emerged between the two treatment groups. Compared to baseline, Treg cell frequency increased exclusively in the intervention group (+1.1%, CI 95% 0.4; 1.7%).

Discussion

This pilot study suggested that VitD and Se supplementation, in GD patients receiving MMI treatment, modulates Treg and NK cell frequency, favoring a more pronounced reduction of NK cells and the increase of Treg cells, compared to MMI alone. Even if further studies are needed, it is possible to speculate that this immunomodulatory action might have facilitated the prompter and better control of hyperthyroidism in the supplemented group observed in the previous study.

Recent advances in developing active targeting and multi-functional drug delivery systems via bioorthogonal chemistry

Bioorthogonal chemistry reactions occur in physiological conditions without interfering with normal physiological processes. Through metabolic engineering, bioorthogonal groups can be tagged onto cell membranes, which selectively attach to cargos with paired groups via bioorthogonal reactions. Due to its simplicity, high efficiency, and specificity, bioorthogonal chemistry has demonstrated great application potential in drug delivery. On the one hand, bioorthogonal reactions improve therapeutic agent delivery to target sites, overcoming off-target distribution. On the other hand, nanoparticles and biomolecules can be linked to cell membranes by bioorthogonal reactions, providing approaches to developing multi-functional drug delivery systems (DDSs). In this review, we first describe the principle of labeling cells or pathogenic microorganisms with bioorthogonal groups. We then highlight recent breakthroughs in developing active targeting DDSs to tumors, immune systems, or bacteria by bioorthogonal chemistry, as well as applications of bioorthogonal chemistry in developing functional bio-inspired DDSs (biomimetic DDSs, cell-based DDSs, bacteria-based and phage-based DDSs) and hydrogels. Finally, we discuss the difficulties and prospective direction of bioorthogonal chemistry in drug delivery. We expect this review will help us understand the latest advances in the development of active targeting and multi-functional DDSs using bioorthogonal chemistry and inspire innovative applications of bioorthogonal chemistry in developing smart DDSs for disease treatment.

Medicinal herbs and multiple sclerosis: Overview on the hard balance between new therapeutic strategy and occupational health risk

Multiple sclerosis (MS) is an autoimmune disease characterized by demyelination and axonal loss of the central nervous system (CNS). Despite its spread throughout the world, the mechanisms that determine its onset are still to be defined. Immunological, genetic, viral, and environmental factors and exposure to chemicals may trigger MS. Many studies have highlighted the anti-inflammatory and anti-oxidant effects of medicinal herbs, which make them a natural and complementary treatment for neurodegenerative diseases. A severe reduction of several MS symptoms occurs with herbal therapy. Thus, the request for medicinal plants with potential beneficial effects, for MS patients, is constantly increasing. Consequently, a production increase needs. Unfortunately, many medicinal herbs were untested and their action mechanism, possible adverse effects, contraindications, or interactions with other drugs, are poorly or not investigated. Keeping in mind the pathological mechanisms of MS and the oxidative damages and mitochondrial dysfunctions induced by pesticides, it is important to understand if pesticides used to increase agricultural productivity and their residues in medicinal plants, may increase the risk of developing MS in both workers and consumers. Studies providing some indication about the relationship between environmental exposure to pesticides and MS disease incidence are few, fragmentary, and discordant. The aim of this article is to provide a glance at the therapeutic potential of medicinal plants and at the risk for MS onset of pesticides used by medicinal plant growers and present in medicinal herbs.

Studying the Interactions of U24 from HHV-6 in Order to Further Elucidate Its Potential Role in MS

A number of studies have suggested that human herpesvirus 6A (HHV-6A) may play a role in multiple sclerosis (MS). Three possible hypotheses have been investigated: (1) U24 from HHV-6A (U24-6A) mimics myelin basic protein (MBP) through analogous phosphorylation and interaction with Fyn-SH3; (2) U24-6A affects endocytic recycling by binding human neural precursor cell (NPC) expressed developmentally down-regulated protein 4-like WW3* domain (hNedd4L-WW3*); and (3) MS patients who express Killer Cell Immunoglobulin Like Receptor 2DL2 (KIR2DL2) on natural killer (NK) cells are more susceptible to HHV-6 infection. In this contribution, we examined the validity of these propositions by investigating the interactions of U24 from HHV-6B (U24-6B), a variant less commonly linked to MS, with Fyn-SH3 and hNedd4L-WW3* using heteronuclear single quantum coherence (HSQC) nuclear magnetic resonance (NMR) titrations and isothermal titration calorimetry (ITC). In addition, the importance of phosphorylation and the specific role of U24 in NK cell activation in MS patients were examined. Overall, the findings allowed us to shed light into the models linking HHV-6 to MS and the involvement of U24.

Single-Cell Analysis to Better Understand the Mechanisms Involved in MS

Multiple sclerosis is a chronic and inflammatory disease of the central nervous system. Although this disease is widely studied, many of the precise mechanisms involved are still not well known. Numerous studies currently focusing on multiple sclerosis highlight the involvement of many major immune cell subsets, such as CD4+ T cells, CD8+ T cells and more recently B cells. However, our vision of its pathology has remained too broad to allow the proper use of targeted therapeutics. This past decade, new technologies have emerged, enabling deeper research into the different cell subsets at the single-cell level both in the periphery and in the central nervous system. These technologies could allow us to identify new cell populations involved in the disease process and new therapeutic targets. In this review, we briefly introduce the major single-cell technologies currently used in studies before diving into the major findings from the multiple sclerosis research from the past 5 years. We focus on results that were obtained using single-cell technologies to study immune cells and cells from the central nervous system.

Ofatumumab Modulates Inflammatory T Cell Responses and Migratory Potential in Patients With Multiple Sclerosis

BACKGROUND AND OBJECTIVES

The anti-CD20 antibody ofatumumab is an efficacious therapy for multiple sclerosis (MS) through depletion of B cells. The purpose of this study was to examine the derivative effects of B cell depletion on the peripheral immune system and a direct treatment effect on T cells expressing CD20.

METHODS

Frequency and absolute numbers of peripheral leukocytes of treatment-naive patients with relapsing-remitting MS (RRMS) and patients treated with ofatumumab for a mean of 482 days were assessed in this observational study by flow cytometry. In addition, effector function and CNS migration of T cells using a human in vitro blood-brain barrier (BBB) assay were analyzed.

RESULTS

This study showed that ofatumumab treatment of patients with RRMS increased the control of effector T cells and decreased T cell autoreactivity. It also showed that ofatumumab reduced the level of peripheral CD20⁺ T cells and that the observed decrease in CNS-migratory capacity of T cells was caused by the depletion of CD20⁺ T cells. Finally, our study pointed out a bias in the measurement of CD20⁺ cells due to a steric hindrance between the treatment antibody and the flow cytometry antibody.

DISCUSSION

The substantial ofatumumab-induced alteration in the T cell compartment including a severely decreased CNS-migratory capacity of T cells could partly be attributed to the depletion of CD20⁺ T cells. Therefore, we propose that depletion of CD20⁺ T cells contributes to the positive treatment effect of ofatumumab and suggests that ofatumumab therapy should be considered a B cell and CD20⁺ T cell depletion therapy.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that compared with treatment-naive patients, ofatumumab treatment of patients with RRMS decreases peripheral CD20⁺ T cells, increases effector T cell control, and decreases T cell autoreactivity.

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.

Natural Killer Cells in Multiple Sclerosis: Entering the Stage

Studies investigating the immunopathology of multiple sclerosis (MS) have largely focused on adaptive T and B lymphocytes. However, in recent years there has been an increased interest in the contribution of innate immune cells, amongst which the natural killer (NK) cells. Apart from their canonical role of controlling viral infections, cell stress and malignancies, NK cells are increasingly being recognized for their modulating effect on the adaptive immune system, both in health and autoimmune disease. From different lines of research there is now evidence that NK cells contribute to MS immunopathology. In this review, we provide an overview of studies that have investigated the role of NK cells in the pathogenesis of MS by use of the experimental autoimmune encephalomyelitis (EAE) animal model, MS genetics or through ex vivo and in vitro work into the immunology of MS patients. With the advent of modern hypothesis-free technologies such as single-cell transcriptomics, we are exposing an unexpected NK cell heterogeneity, increasingly blurring the boundaries between adaptive and innate immunity. We conclude that unravelling this heterogeneity, as well as the mechanistic link between innate and adaptive immune cell functions will lay the foundation for the use of NK cells as prognostic tools and therapeutic targets in MS and a myriad of other currently uncurable autoimmune disorders.

The current standing of autologous haematopoietic stem cell transplantation for the treatment of multiple sclerosis

Autologous haematopoietic stem cell transplantation (aHSCT) is gaining traction as a valuable treatment option for patients affected by severe multiple sclerosis (MS), particularly the relapsing–remitting form. We describe the current literature in terms of clinical trials, observational and retrospective studies, as well as immune reconstitution following transplantation, with a focus on the conditioning regimens used for transplantation. The evidence base predominantly consists of non-randomised, uncontrolled clinical trials or data from retrospective or observational cohorts, i.e. very few randomised or controlled trials. Most often, intermediate-intensity conditioning regimens are used, with promising results from both myeloablative and lymphoablative strategies, as well as from regimens that are low and high intensity. Efficacy of transplantation, which is likely secondary to immune reconstitution and restored immune tolerance, is, therefore, not clearly dependent on the intensity of the conditioning regimen. However, the conditioning regimen may well influence the immune response to transplantation. Heterogeneity of conditioning regimens among studies hinders synthesis of the articles assessing post-aHSCT immune system changes. Factors associated with better outcomes were lower Kurtzke Expanded Disability Status Scale, relapsing–remitting MS, younger age, and shorter disease duration at baseline, which supports the guidance for patient selection proposed by the European Society for Blood and Marrow Transplantation. Interestingly, promising outcomes were described for patients with secondary progressive MS by some studies, which may be worth taking into account when considering treatment options for patients with active, progressive disease. Of note, a significant proportion of patients develop autoimmune disease following transplantation, with alemtuzumab-containing regimens associated with the highest incidence.

NK Cells and Innate-Like T Cells After Autologous Hematopoietic Stem Cell Transplantation in Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, in which autoreactive T and B cells play important roles. Other lymphocytes such as NK cells and innate-like T cells appear to be involved as well. To name a few examples, CD56^bright NK cells were described as an immunoregulatory NK cell subset in MS while innate-like T cells in MS were described in brain lesions and with proinflammatory signatures. Autologous hematopoietic stem cell transplantation (aHSCT) is a procedure used to treat MS. This procedure includes hematopoietic stem/progenitor cell (HSPC) mobilization, then high-dose chemotherapy combined with anti-thymocyte globulin (ATG) and subsequent infusion of the patients own HSPCs to reconstitute a functional immune system. aHSCT inhibits MS disease activity very effectively and for long time, presumably due to elimination of autoreactive T cells. Here, we performed multidimensional flow cytometry experiments in peripheral blood lymphocytes of 27 MS patients before and after aHSCT to address its potential influence on NK and innate-like T cells. After aHSCT, the relative frequency and absolute numbers of CD56^bright NK cells rise above pre-aHSCT levels while all studied innate-like T cell populations decrease. Hence, our data support an enhanced immune regulation by CD56^bright NK cells and the efficient reduction of proinflammatory innate-like T cells by aHSCT in MS. These observations contribute to our current understanding of the immunological effects of aHSCT in MS.

The IL-2 - IL-2 receptor pathway: Key to understanding multiple sclerosis

The development, progression, diagnosis and treatment of autoimmune diseases, such as multiple sclerosis (MS), are convoluted processes which remain incompletely understood. Multiple studies demonstrated that the interleukin (IL)-2 – IL-2 receptor (IL-2R) pathway plays a pivotal role within these processes. The most striking functions of the IL-2 – IL-2R pathway are the differential induction of autoimmune responses and tolerance. This paradoxical function of the IL-2 – IL-2R pathway may be an attractive therapeutic target for autoimmune diseases such as MS. However, the exact mechanisms that lead to autoimmunity or tolerance remain to be elucidated. Furthermore, another factor of this pathway, the soluble form of the IL-2R (sIL-2R), further complicates understanding the role of the IL-2 – IL-2R pathway in MS. The challenge is to unravel these mechanisms to prevent, diagnose and recover MS. In this review, first, the current knowledge of MS and the IL-2 – IL-2R pathway are summarized. Second, the key findings of the relation between the IL-2 – IL-2R pathway and MS have been highlighted. Eventually, this review may launch broad interest in the IL-2 – IL-2R pathway propelling further research in autoimmune diseases, including MS.

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The IL-2 – IL-2R pathway determines the balance between immunity and tolerance.

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The IL-2 – IL-2R pathway is involved in the pathogenesis of multiple sclerosis.

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The role of soluble IL-2R is controversial and requires further investigation.

Fingolimod as a first- or second-line treatment in a mini-series of young Hellenic patients with adolescent-onset multiple sclerosis: focus on immunological data

BACKGROUND

Pediatric onset multiple sclerosis(POMS) is characterized by a highly active profile, often warranting treatment with high efficacy disease-modulating therapies (DMTs). Fingolimod, an oral sphingosine-1-phosphate receptor modulator, is the first Food and Drug Administration (FDA)- and European Medicines Agency (EMA)-approved DMT for the treatment of POMS.

OBJECT

Our aim is to present real-world data of seven fingolimod-treated POMS-patients, recruited in a single MS center in Greece.

METHODS

Clinical and imaging/laboratory data from 7 Hellenic patients fulfilling the International Pediatric Multiple Sclerosis Study Group (IPMSSG) criteria for POMS diagnosis, who have received fingolimod treatment, were selected. Human leukocyte antigen (HLA) genotyping was performed with standard low-resolution sequence-specific oligonucleotide techniques.

RESULTS

Three patients were treatment-naïve adolescents who received fingolimod as first-line treatment. Two experienced ongoing clinical and radiological disease activity and have been switched to natalizumab. The remaining cases were post-adolescent adults with POMS, where the vast majority experienced total/near-total disease remission. Fingolimod was generally well-tolerated. Two patients with high disease activity carried the HLA-DRB1*03 allele, while five patients were carriers of at least one of the HLA-DRB1*04, HLA-DRB1*13, and HLA-DRB1*14 alleles, which when not combined with HLA-DRB1*03 showed a trend towards a more favorable clinical course. Fingolimod responders showed a trend towards increased CD(16-56)⁺NK cell counts in immunophenotyping assays.

CONCLUSIONS

Our preliminary results support that response of POMS patients to fingolimod may be partially dependent on age and previous DMT, with younger and treatment-naïve patients presenting worse outcomes. The role of immunogenetics and immunophenotyping in personalized treatment warrants investigation in larger and more diverse populations.

Made to Measure: Patient-Tailored Treatment of Multiple Sclerosis Using Cell-Based Therapies

Currently, there is still no cure for multiple sclerosis (MS), which is an autoimmune and neurodegenerative disease of the central nervous system. Treatment options predominantly consist of drugs that affect adaptive immunity and lead to a reduction of the inflammatory disease activity. A broad range of possible cell-based therapeutic options are being explored in the treatment of autoimmune diseases, including MS. This review aims to provide an overview of recent and future advances in the development of cell-based treatment options for the induction of tolerance in MS. Here, we will focus on haematopoietic stem cells, mesenchymal stromal cells, regulatory T cells and dendritic cells. We will also focus on less familiar cell types that are used in cell therapy, including B cells, natural killer cells and peripheral blood mononuclear cells. We will address key issues regarding the depicted therapies and highlight the major challenges that lie ahead to successfully reverse autoimmune diseases, such as MS, while minimising the side effects. Although cell-based therapies are well known and used in the treatment of several cancers, cell-based treatment options hold promise for the future treatment of autoimmune diseases in general, and MS in particular.

Proportions of circulating transitional B cells associate with MRI activity in interferon beta-treated multiple sclerosis patients

B-cells contribute to MS pathogenesis. The association of circulating B-cell phenotypes with combined unique active lesions (CUA) on MRI at 48 weeks follow-up was investigated in 50 interferon beta-treated MS patients. Transitional B-cell proportions were lower in participants with CUA at week 0 and 48 [p = 0.004, p = 0.002]. A decrease in circulating anti-EBNA-1 IgG levels between week 0 and 48 associated with absence of CUA [p = 0.047], but not with B-cell profiles. In a multi-factor model for CUA-risk, transitional B-cell proportions contributed independent from NK/T-cell ratio, change in anti-EBNA-1 IgG, and vitamin D supplementation. Transitional B-cells may predict treatment response in MS.

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.

Cross-Talk of the CNS With Immune Cells and Functions in Health and Disease

The immune system's role is much more than merely recognizing self vs. non-self and involves maintaining homeostasis and integrity of the organism starting from early development to ensure proper organ function later in life. Unlike other systems, the central nervous system (CNS) is separated from the peripheral immune machinery that, for decades, has been envisioned almost entirely as detrimental to the nervous system. New research changes this view and shows that blood-borne immune cells (both adaptive and innate) can provide homeostatic support to the CNS via neuroimmune communication. Neurodegeneration is mostly viewed through the lens of the resident brain immune populations with little attention to peripheral circulation. For example, cognition declines with impairment of peripheral adaptive immunity but not with the removal of microglia. Therapeutic failures of agents targeting the neuroinflammation framework (inhibiting immune response), especially in neurodegenerative disorders, call for a reconsideration of immune response contributions. It is crucial to understand cross-talk between the CNS and the immune system in health and disease to decipher neurodestructive and neuroprotective immune mechanisms for more efficient therapeutic strategies.

Complete Freund's adjuvant-free experimental autoimmune encephalomyelitis in Dark Agouti rats is a valuable tool for multiple sclerosis studies

Experimental autoimmune encephalomyelitis (EAE) is classically induced with complete Freund's adjuvant (CFA). The immune response against CFA has a confounding influence on the translational capacity of EAE as a multiple sclerosis model. Here, we compare clinical, cellular and molecular properties between syngeneic spinal cord homogenate (SCH)- and SCH + CFA-immunized Dark Agouti rats. EAE signs were observed earlier and the cumulative clinical score was higher without CFA. Also, a higher number of immune cells infiltrates in the spinal cords was noticed at the peak of EAE without CFA. High spinal cord abundance of CD8⁺CD11bc⁺MHC class II⁺ cells was detected in SCH-immunized rats. Myelin basic protein -specific response can be elicited in the cells from the lymph nodes draining the site of SCH immunization. This CFA-free EAE is a reliable multiple sclerosis model.

NK Cells in Autoimmune Diseases: Protective or Pathogenic?

Autoimmune diseases generally result from the loss of self-tolerance (i.e., failure of the immune system to distinguish self from non-self), and are characterized by autoantibody production and hyperactivation of T cells, which leads to damage of specific or multiple organs. Thus, autoimmune diseases can be classified as organ-specific or systemic. Genetic and environmental factors contribute to the development of autoimmunity. Recent studies have demonstrated the contribution of innate immunity to the onset of autoimmune diseases. Natural killer (NK) cells, which are key components of the innate immune system, have been implicated in the development of multiple autoimmune diseases such as systemic lupus erythematosus, type I diabetes mellitus, and autoimmune liver disease. However, NK cells have both protective and pathogenic roles in autoimmunity depending on the NK cell subset, microenvironment, and disease type or stage. In this work, we review the current knowledge of the varied roles of NK cell subsets in systemic and organic-specific autoimmune diseases and their clinical potential as therapeutic targets.

Prognostic value of natural killer cell/T cell ratios for disease activity in multiple sclerosis

Background and purpose

Natural killer (NK) cells may play a role in multiple sclerosis (MS). Ratios of NK cells to CD4⁺ T cells have been proposed as a biomarker for the therapeutic effect of stem cell transplantation in MS. The objectives here were to explore the relevance of this ratio in MS patients by analysing NK and T cell subsets, as well as their prognostic value for disease activity.

Methods

Baseline peripheral blood mononuclear cells of 50 relapsing–remitting MS patients, participating in our vitamin D supplementation study (SOLARIUM), were analysed with flow cytometry. Disease activity was measured as new magnetic resonance imaging lesions, relapses and mean plasma neurofilament light chain levels after 48 weeks of follow‐up.

Results

The proportion of NK cells correlated negatively with CD4⁺ T cells (R = −0.335, p = 0.001) and interleukin 17A (IL‐17A⁺) CD4⁺ T cells (R = −0.203, p = 0.043). Participants with magnetic resonance imaging activity or relapses displayed lower NK/IL‐17A⁺ CD4⁺ T cell ratios (p =0.025 and p = 0.006, respectively). The NK/IL‐17A⁺ CD4⁺ T cell ratio correlated negatively with neurofilament light chain levels (R = −0.320, p = 0.050). Vitamin D supplementation did not affect these ratios.

Conclusions

Our data suggest a protective role of an expanded NK cell compartment compared to the CD4⁺ T cell subset fractions in relapsing–remitting MS patients. NK/CD4⁺ T cell ratios may be a prognostic biomarker for disease activity in MS.

Drugs for Multiple Sclerosis Activate Natural Killer Cells: Do They Protect Against COVID-19 Infection?

COVID-19 infection caused by the newly discovered coronavirus severe acute respiratory distress syndrome virus-19 (SARS-CoV-2) has become a pandemic issue across the globe. There are currently many investigations taking place to look for specific, safe and potent anti-viral agents. Upon transmission and entry into the human body, SARS-CoV-2 triggers multiple immune players to be involved in the fight against the viral infection. Amongst these immune cells are NK cells that possess robust antiviral activity, and which do not require prior sensitization. However, NK cell count and activity were found to be impaired in COVID-19 patients and hence, could become a potential therapeutic target for COVID-19. Several drugs, including glatiramer acetate (GA), vitamin D₃, dimethyl fumarate (DMF), monomethyl fumarate (MMF), natalizumab, ocrelizumab, and IFN-β, among others have been previously described to increase the biological activities of NK cells especially their cytolytic potential as reported by upregulation of CD107a, and the release of perforin and granzymes. In this review, we propose that such drugs could potentially restore NK cell activity allowing individuals to be more protective against COVID-19 infection and its complications.

Metabolic determinants of leukocyte pathogenicity in neurological diseases

Neuroinflammatory and neurodegenerative diseases are characterized by the recruitment of circulating blood-borne innate and adaptive immune cells into the central nervous system (CNS). These leukocytes sustain the detrimental response in the CNS by releasing pro-inflammatory mediators that induce activation of local glial cells, blood-brain barrier (BBB) dysfunction, and neural cell death. However, infiltrating peripheral immune cells could also dampen CNS inflammation and support tissue repair. Recent advances in the field of immunometabolism demonstrate the importance of metabolic reprogramming for the activation and functionality of such innate and adaptive immune cell populations. In particular, an increasing body of evidence suggests that the activity of metabolites and metabolic enzymes could influence the pathogenic potential of immune cells during neuroinflammatory and neurodegenerative disorders. In this review, we discuss the role of intracellular metabolic cues in regulating leukocyte-mediated CNS damage in Alzheimer's and Parkinson's disease, multiple sclerosis and stroke, highlighting the therapeutic potential of drugs targeting metabolic pathways for the treatment of neurological diseases.

Immunological Drivers in Graves' Disease: NK Cells as a Master Switcher

Graves' disease (GD) is a common autoimmune cause of hyperthyroidism, which is eventually related to the generation of IgG antibodies stimulating the thyrotropin receptor. Clinical manifestations of the disease reflect hyperstimulation of the gland, causing thyrocyte hyperplasia (goiter) and excessive thyroid hormone synthesis (hyperthyroidism). The above clinical manifestations are preceded by still partially unraveled pathogenic actions governed by the induction of aberrant phenotype/functions of immune cells. In this review article we investigated the potential contribution of natural killer (NK) cells, based on literature analysis, to discuss the bidirectional interplay with thyroid hormones (TH) in GD progression. We analyzed cellular and molecular NK-cell associated mechanisms potentially impacting on GD, in a view of identification of the main NK-cell subset with highest immunoregulatory role.