Natural killer cell subsets in cerebrospinal fluid of patients with multiple sclerosis

Natural killer cells in multiple sclerosis: foe or friends?

Multiple sclerosis (MS) is an immune-mediated disorder involving the central nervous system (CNS), in which demyelination is caused. The initiation and progression of MS is thought to depend largely on CD4+ T lymphocytes, yet new data has emphasized the involvement of the innate immune system in the MS disease responses. Generally, several types of immune cells play a part, with natural killer (NK) cells being essential. Different subsets of natural killer cells function differently within the course of an autoimmune disease, such as MS. There are mainly two types of natural killers in humans: immature CD56 bright CD16- and mature CD56 dim CD16+ natural killers, together with their respective subtypes. Factors from natural killers expand the T cell population and control the process by which native CD4+ T cells differentiate into Th1 or Th2 lymphocytes, which affect autoimmune responses. Natural killer subsets CD56 bright and CD56 dim may have differing roles in MS development. The impact of these NK cell subsets is influenced by factors such as Granzymes, genetics, infections, TLR, and HSP. We reviewed and evaluated the relationship between natural killer cells and MS.

Neuroinflammation causes mitral cell dysfunction and olfactory impairment in a multiple sclerosis model

BACKGROUND

Olfactory dysfunction is an underestimated symptom in multiple sclerosis (MS). Here, we examined the pathogenic mechanisms underlying inflammation-induced dysfunction of the olfactory bulb using the animal model of MS, experimental autoimmune encephalomyelitis (EAE).

RESULTS

Reduced olfactory function in EAE was associated with the degeneration of short-axon neurons, immature neurons, and both mitral and tufted cells, along with their synaptic interactions and axonal repertoire. To dissect the mechanisms underlying the susceptibility of mitral cells, the main projection neurons of the olfactory bulb, we profiled their responses to neuroinflammation by single-nucleus RNA sequencing followed by functional validation. Neuroinflammation resulted in the induction of potassium channel transcripts in mitral cells, which was reflected in increased halothane-induced outward currents of these cells, likely contributing to the impaired olfaction in EAE animals.

CONCLUSION

This study reveals the crucial role of mitral cells and their potassium channel activity in the olfactory bulb during EAE, thereby enhancing our understanding of neuroinflammation-induced neurodegeneration in MS.

Longitudinal analysis of peripheral immune cells in patients with multiple sclerosis treated with anti-CD20 therapy

OBJECTIVE

Anti-CD20 therapy is a highly effective treatment for multiple sclerosis (MS). In this study, we investigated MS-related changes in peripheral blood mononuclear cell (PBMC) subsets compared to healthy controls and longitudinal changes related to the treatment.

METHODS

Multicolor spectral flow cytometry analysis was performed on 78 samples to characterize disease- and treatment-related PBMC clusters. Blood samples from MS patients were collected at baseline and up to 8 months post-treatment, with three collection points after treatment initiation. Unsupervised clustering tools and manual gating were applied to identify subclusters of interest and quantify changes.

RESULTS

B cells were depleted from the periphery after anti-CD20 treatment as expected, and we observed an isolated acute, transitory drop in the proportion of natural killer (NK) and NKT cells among the main populations of PBMC (P = 0.03, P = 0.004). Major affected PBMC subpopulations were cytotoxic immune cells (NK, NKT, and CD8+ T cells), and we observed a higher proportion of cytotoxic cells with reduced brain-homing ability and a higher regulatory function as a long-term anti-CD20-related effect. Additionally, anti-CD20 therapy altered distributions of memory CD8+ T cells and reduced exhaustion markers in both CD4+ and CD8+ T cells.

INTERPRETATION

The findings of this study elucidate phenotypic clusters of NK and CD8+ T cells, which have previously been underexplored in the context of anti-CD20 therapy. Phenotypic modifications towards a more regulatory and controlled phenotype suggest that these subpopulations may play a critical and previously unrecognized role in mediating the therapeutic efficacy of anti-CD20 treatments.

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.

The role of miRNAs in multiple sclerosis pathogenesis, diagnosis, and therapeutic resistance

In recent years, microRNAs (miRNAs) have gained increased attention from researchers around the globe. Although it is twenty nucleotides long, it can modulate several gene targets simultaneously. Their mal expression is a signature of various pathologies, and they provide the foundation to elucidate the molecular mechanisms of each pathology. Among the debilitating central nervous system (CNS) disorders with a growing prevalence globally is the multiple sclerosis (MS). Moreover, the diagnosis of MS is challenging due to the lack of disease-specific biomarkers, and the diagnosis mainly depends on ruling out other disabilities. MS could adversely affect patients' lives through its progression, and only symptomatic treatments are available as therapeutic options, but an exact cure is yet unavailable. Consequently, this review hopes to further the study of the biological features of miRNAs in MS and explore their potential as a therapeutic target.

MOGAD patient autoantibodies induce complement, phagocytosis, and cellular cytotoxicity

Myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) is an inflammatory demyelinating CNS condition characterized by the presence of MOG autoantibodies. We sought to investigate whether human MOG autoantibodies are capable of mediating damage to MOG-expressing cells through multiple mechanisms. We developed high-throughput assays to measure complement activity (CA), complement-dependent cytotoxicity (CDC), antibody-dependent cellular phagocytosis (ADCP), and antibody-dependent cellular cytotoxicity (ADCC) of live MOG-expressing cells. MOGAD patient sera effectively mediate all of these effector functions. Our collective analyses reveal that (a) cytotoxicity is not incumbent on MOG autoantibody quantity alone; (b) engagement of effector functions by MOGAD patient serum is bimodal, with some sera exhibiting cytotoxic capacity while others did not; (c) the magnitude of CDC and ADCP is elevated closer to relapse, while MOG-IgG binding is not; and (d) all IgG subclasses can damage MOG-expressing cells. Histopathology from a representative MOGAD case revealed congruence between lesion histology and serum CDC and ADCP, and we identified NK cells, mediators of ADCC, in the cerebrospinal fluid of relapsing patients with MOGAD. Thus, MOGAD-derived autoantibodies are cytotoxic to MOG-expressing cells through multiple mechanisms, and assays quantifying CDC and ADCP may prove to be effective tools for predicting risk of future relapses.

CD3+CD56+ and CD3-CD56+ lymphocytes in the cerebrospinal fluid of persons with HIV-1 subtypes B and C

The transactivator of transcription (Tat) is a HIV regulatory protein which promotes viral replication and chemotaxis. HIV-1 shows extensive genetic diversity, HIV-1 subtype C being the most dominant subtype in the world. Our hypothesis is the frequency of CSF CD3+CD56+ and CD3-CD56dim is reduced in HIV-1C compared to HIV-1B due to the Tat C30S31 substitution in HIV-1C. 34 CSF and paired blood samples (PWH, n = 20; PWoH, n = 14) were studied. In PWH, the percentage of CD3+CD56+ was higher in CSF than in blood (p < 0.001), comparable in both compartments in PWoH (p = 0.20). The proportion of CD3-CD56dim in CSF in PWH was higher than PWoH (p = 0.008). There was no subtype differences. These results showed CNS compartmentalization of NKT cell response in PWH.

Natural Killer T-like Cells: Immunobiology and Role in Disease

CD56+ T cells are generally recognized as a distinct population of T cells and are categorized as NKT-like cells. Although our understanding of NKT-like cells is far from satisfactory, it has been shown that aging and a number of disease situations have impacted these cells. To construct an overview of what is currently known, we reviewed the literature on human NKT-like cells. NKT-like cells are highly differentiated T cells with "CD1d-independent" antigen recognition and MHC-unrestricted cell killing. The genesis of NKT-like cells is unclear; however, it is proposed that the acquisition of innate characteristics by T cells could represent a remodeling process leading to successful aging. Additionally, it has been shown that NKT-like cells may play a significant role in several pathological conditions, making it necessary to comprehend whether these cells might function as prognostic markers. The quantification and characterization of these cells might serve as a cutting-edge indicator of individual immune health. Additionally, exploring the mechanisms that can control their killing activity in different contexts may therefore result in innovative therapeutic alternatives in a wide range of disease settings.

The immunology of multiple sclerosis

Our incomplete understanding of the causes and pathways involved in the onset and progression of multiple sclerosis (MS) limits our ability to effectively treat this complex neurological disease. Recent studies explore the role of immune cells at different stages of MS and how they interact with cells of the central nervous system (CNS). The findings presented here begin to question the exclusivity of an antigen-specific cause and highlight how seemingly distinct immune cell types can share common functions that drive disease. Innovative techniques further expose new disease-associated immune cell populations and reinforce how environmental context is critical to their phenotype and subsequent role in disease. Importantly, the differentiation of immune cells into a pathogenic state is potentially reversible through therapeutic manipulation. As such, understanding the mechanisms that provide plasticity to causal cell types is likely key to uncoupling these disease processes and may identify novel therapeutic targets that replace the need for cell ablation.

Stabilization of leukocytes from cerebrospinal fluid for central immunophenotypic evaluation in multicenter clinical trials

Analysis of cerebrospinal fluid (CSF) represents a valuable window into the pathogenesis of neuroinflammatory diseases, such as multiple sclerosis (MS). However, analysis of the cellular fraction of CSF is often neglected because CSF cells die rapidly ex vivo. Immunophenotyping of CSF cells in multicenter clinical trials requires sample preservation and shipping to a centralized lab. Yet, there is no consensus on the best method to preserve intact CSF cells and no detailed evaluation of subset-specific cell loss. We used flow cytometry to compare major leukocyte populations in fresh CSF (processed within 2 h) to cells fixed for 48 h with TransFix-EDTA® or cryopreserved and thawed after 96 h. We observed a statistically significant loss of total mononuclear cells, total T cells, CD3+ CD8- T cells, and CD3+ CD8+ T cells after cryopreservation compared to fresh or fixed (p < 0.001), with no significant difference between fresh and fixed. Thus, our results demonstrate that TransFix-EDTA® was superior to cryopreservation for preserving intact CSF T cells. Surprisingly, neither cryopreservation nor fixation had a significant effect on recovery of low frequency cell subsets in CSF, including B cells, NK cells, NKT-like cells, CD14+ monocytes, or CD123+ DCs, versus fresh CSF. To determine the effect of prolonged fixation on cell recovery, we analyzed major CSF cell subsets by flow cytometry after 24, 48, or 72 h of fixation with TransFix-EDTA®. We observed a consistent and progressive loss in the absolute counts of all subsets over time, although this effect was not statistically significant. We conclude that for immunophenotyping of major CSF cell subsets by flow cytometry, fixation with TransFix-EDTA®, shipment to a central lab, and analysis within 48 h is a feasible method to ensure stability of both absolute cell number and relative frequency. This method is a valuable alternative to fresh CSF analysis and can be implemented in multicenter clinical trials.

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.

Tissue-Dependent Adaptations and Functions of Innate Lymphoid Cells

Tissue-resident immune cells reside in distinct niches across organs, where they contribute to tissue homeostasis and rapidly respond to perturbations in the local microenvironment. Innate lymphoid cells (ILCs) are a family of innate immune cells that regulate immune and tissue homeostasis. Across anatomical locations throughout the body, ILCs adopt tissue-specific fates, differing from circulating ILC populations. Adaptations of ILCs to microenvironmental changes have been documented in several inflammatory contexts, including obesity, asthma, and inflammatory bowel disease. While our understanding of ILC functions within tissues have predominantly been based on mouse studies, development of advanced single cell platforms to study tissue-resident ILCs in humans and emerging patient-based data is providing new insights into this lymphocyte family. Within this review, we discuss current concepts of ILC fate and function, exploring tissue-specific functions of ILCs and their contribution to health and disease across organ systems.

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

Aging is characterized, amongst other features, by a complex process of cellular senescence involving both innate and adaptive immunity, called immunosenescence and associated to inflammaging, a low-grade chronic inflammation. Both processes fuel each other and partially explain increasing incidence of cancers, infections, age-related autoimmunity, and vascular disease as well as a reduced response to vaccination. Multiple sclerosis (MS) is a lifelong disease, for which considerable progress in disease-modifying therapies (DMTs) and management has improved long-term survival. However, disability progression, increasing with age and disease duration, remains. Neurologists are now involved in caring for elderly MS patients, with increasing comorbidities. Aging of the immune system therefore has relevant implications for MS pathogenesis, response to DMTs and the risks mediated by these treatments. We propose to review current evidence regarding markers and molecular mechanisms of immunosenescence and their relevance to understanding MS pathogenesis. We will focus on age-related changes in the innate and adaptive immune system in MS and other auto-immune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. The consequences of these immune changes on MS pathology, in interaction with the intrinsic aging process of central nervous system resident cells will be discussed. Finally, the impact of immunosenescence on disease evolution and on the safety and efficacy of current DMTs will be presented.

Single-Cell Transcriptome Profiling Unravels Distinct Peripheral Blood Immune Cell Signatures of RRMS and MOG Antibody-Associated Disease

Relapsing-remitting multiple sclerosis (RRMS) and myelin oligodendrocyte glycoprotein (MOG) antibody-associated disease (MOGAD) are inflammatory demyelinating diseases of the central nervous system (CNS). Due to the shared clinical manifestations, detection of disease-specific serum antibody of the two diseases is currently considered as the gold standard for the diagnosis; however, the serum antibody levels are unpredictable during different stages of the two diseases. Herein, peripheral blood single-cell transcriptome was used to unveil distinct immune cell signatures of the two diseases, with the aim to provide predictive discrimination. Single-cell RNA sequencing (scRNA-seq) was conducted on the peripheral blood from three subjects, i.e., one patient with RRMS, one patient with MOGAD, and one patient with healthy control. The results showed that the CD19+ CXCR4+ naive B cell subsets were significantly expanded in both RRMS and MOGAD, which was verified by flow cytometry. More importantly, RRMS single-cell transcriptomic was characterized by increased naive CD8+ T cells and cytotoxic memory-like Natural Killer (NK) cells, together with decreased inflammatory monocytes, whereas MOGAD exhibited increased inflammatory monocytes and cytotoxic CD8 effector T cells, coupled with decreased plasma cells and memory B cells. Collectively, our findings indicate that the two diseases exhibit distinct immune cell signatures, which allows for highly predictive discrimination of the two diseases and paves a novel avenue for diagnosis and therapy of neuroinflammatory diseases.

The role of NK and NKT cells in the pathogenesis and improvement of multiple sclerosis following disease-modifying therapies

BACKGROUND

Multiple sclerosis (MS) is an autoimmune inflammatory disease of the central nervous system (CNS) that T cells become autoreactive by recognizing CNS antigens. Both innate and adaptive immune systems are involved in the pathogenesis of MS. In recent years, the impact of innate immune cells on MS pathogenesis has received more attention. CD56bright NK cells, as an immunoregulatory subset of NK cells, can increase the production of cytokines that modulate adaptive immune responses, whereas CD56dim NK cells are more active in cytolysis functions. These two main subsets of NK cells may have different effects on the onset or progression of MS. Invariant NKT (iNKT) cells are other immune cells involved in the control of autoimmune diseases; however, variant NKT (vNKT) cells, despite limited information, could play a role in MS remission via an immunoregulatory pathway.

AIM

We aimed to evaluate the influence of MS therapeutic agents on NK and NKT cells and NK cell subtypes.

MATERIALS AND METHODS

The possible mechanism of each MS therapeutic agent has been presented here, focusing on the effects of different disease-modifying therapies on the number of NK and NKT subtypes.

RESULTS

Expansion of CD56bright NK cells, reduction in the CD56dim cells, and enhancement in NKT cells are the more important innate immune cells alterations following the disease-modifying therapies.

CONCLUSION

Expansion of CD56bright NK cells or reduction in the CD56dim cells has been associated with a successful response to different treatments in MS. iNKT and vNKT cells could have beneficial effects on MS improving. It seems that they are enhanced due to some of MS drugs, leading to disease improvement. However, a reduction in the number of NKT cells could be due to the adverse effects of some of MS drugs on the bone marrow.

Role of the PD-1/PD-L1 Signaling in Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis: Recent Insights and Future Directions

Multiple sclerosis (MS) is an autoimmunity-related chronic demyelination disease of the central nervous system (CNS), causing young disability. Currently, highly specific immunotherapies for MS are still lacking. Programmed cell death 1 (PD-1) is an immunosuppressive co-stimulatory molecule, which is expressed on activated T lymphocytes, B lymphocytes, natural killer cells, and other immune cells. PD-L1, the ligand of PD-1, is expressed on T lymphocytes, B lymphocytes, dendritic cells, and macrophages. PD-1/PD-L1 delivers negative regulatory signals to immune cells, maintaining immune tolerance and inhibiting autoimmunity. This review comprehensively summarizes current insights into the role of PD-1/PD-L1 signaling in MS and its animal model experimental autoimmune encephalomyelitis (EAE). The potentiality of PD-1/PD-L1 as biomarkers or therapeutic targets for MS will also be discussed.

The Association of EBV and HHV-6 Viral Load with Different NK and CD8+ T Cell Subsets in The Acute Phase of Relapsing-Remitting Multiple Sclerosis

OBJECTIVE

Epstein-Barr virus (EBV) and Human Herpes virus 6 (HHV-6) are believed to involve in multiple sclerosis (MS) pathogenesis. Natural killer (NK) and CD8+ T cells have essential roles in handling viral infections and their phenotypic and functional properties may be influenced following exposure to viral infections. Here, we investigated the association of NK and CD8+ T cells subpopulations frequency with EBV and HHV-6 viral load in MS patients.

MATERIALS AND METHODS

In this case-control study, EBV and HHV-6 viral load were evaluated in plasma of newly diagnosed relapsing-remitting MS (RRMS) patients at relapse phase (n=23), who were not on disease-modifying therapy (DMT), and sex- and age-matched healthy controls (n=19) using real-time polymerase chain reaction (PCR). The frequency of NK and CD8+ T cells subsets were assessed by CD27, CD28, CD45RO, CD56, and CD57 markers using flow cytometry.

RESULTS

Despite the increased level of EBV viral load in RRMS patients compared to the control group, there was no statistically significant difference in EBV and HHV-6 copy numbers between the studied groups. In addition, a significant decrease was observed in the percentages of CD56bright CD57- and CD56dim CD57+ CD8low CD45RO- NK cells in RRMS patients in comparison to healthy controls. Analysis of CD8+ T cell subsets showed a substantially high proportion of CD27+ CD28+ CD45RO+ CD57- CD8hi T cells in patients at relapse phase compared to controls. The frequency of NK and T cells subtypes was not associated with EBV and HHV6 plasma viral loads.

CONCLUSION

These findings further highlight the variation of NK and CD8+ T cells subsets frequency in clinically active RRMS patients. Since the composition of cells was not associated with EBV and HHV-6 viral load, perhaps other viral infections may be involved in altered NK and CD8+ T cells subpopulation. Larger cohort studies are needed to confirm these results.

NKT and NKT-like Cells in Autoimmune Neuroinflammatory Diseases-Multiple Sclerosis, Myasthenia Gravis and Guillain-Barre Syndrome

NKT cells comprise three subsets-type I (invariant, iNKT), type II, and NKT-like cells, of which iNKT cells are the most studied subset. They are capable of rapid cytokine production after the initial stimulus, thus they may be important for polarisation of Th cells. Due to this, they may be an important cell subset in autoimmune diseases. In the current review, we are summarising results of NKT-oriented studies in major neurological autoimmune diseases-multiple sclerosis, myasthenia gravis, and Guillain-Barre syndrome and their corresponding animal models.

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.

Natural killer cells in inflammatory autoimmune diseases

Natural killer (NK) cells are a specialised population of innate lymphoid cells (ILCs) that help control local immune responses. Through natural cytotoxicity, production of cytokines and chemokines, and migratory capacity, NK cells play a vital immunoregulatory role in the initiation and chronicity of inflammatory and autoimmune responses. Our understanding of their functional differences and contributions in disease settings is evolving owing to new genetic and functional murine proof-of-concept studies. Here, we summarise current understanding of NK cells in several classic autoimmune disorders, particularly in rheumatoid arthritis (RA), multiple sclerosis (MS), systemic lupus erythematosus (SLE) and type 1 diabetes mellitus (T1DM), but also less understood diseases such as idiopathic inflammatory myopathies (IIMs). A better understanding of how NK cells contribute to these autoimmune disorders may pave the way for NK cell-targeted therapeutics.

Extensive Healthy Donor Age/Gender Adjustments and Propensity Score Matching Reveal Physiology of Multiple Sclerosis Through Immunophenotyping

Quantifying cell subpopulations in biological fluids aids in diagnosis and understanding of the mechanisms of injury. Although much has been learned from cerebrospinal fluid (CSF) flow cytometry in neuroimmunological disorders, such as multiple sclerosis (MS), previous studies did not contain enough healthy donors (HD) to derive age- and gender-related normative data and sufficient heterogeneity of other inflammatory neurological disease (OIND) controls to identify MS specific changes. The goals of this blinded training and validation study of MS patients and embedded controls, representing 1,240 prospectively acquired paired CSF/blood samples from 588 subjects was (1) to define physiological age-/gender-related changes in CSF cells, (2) to define/validate cellular abnormalities in blood and CSF of untreated MS through disease duration (DD) and determine which are MS-specific, and (3) to compare effect(s) of low-efficacy (i.e., interferon-beta [IFN-beta] and glatiramer acetate [GA]) and high-efficacy drugs (i.e., natalizumab, daclizumab, and ocrelizumab) on MS-related cellular abnormalities using propensity score matching. Physiological gender differences are less pronounced in the CSF compared to blood, and age-related changes suggest decreased immunosurveillance of CNS by activated HLA-DR+T cells associated with natural aging. Results from patient samples support the concept of MS being immunologically single disease evolving in time. Initially, peripherally activated innate and adaptive immune cells migrate into CSF to form MS lesions. With progression, T cells (CD8+ > CD4+), NK cells, and myeloid dendritic cells are depleted from blood as they continue to accumulate, together with B cells, in the CSF and migrate to CNS tissue, forming compartmentalized inflammation. All MS drugs inhibit non-physiological accumulation of immune cells in the CSF. Although low-efficacy drugs tend to normalize it, high-efficacy drugs overshoot some aspects of CSF physiology, suggesting impairment of CNS immunosurveillance. Comparable inhibition of MS-related CSF abnormalities advocates changes within CNS parenchyma responsible for differences in drug efficacy on MS disability progression. Video summarizing all results may become useful educational tool.

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.

Rps27a might act as a controller of microglia activation in triggering neurodegenerative diseases

Neurodegenerative diseases (NDDs) are increasing serious menaces to human health in the recent years. Despite exhibiting different clinical phenotypes and selective neuronal loss, there are certain common features in these disorders, suggesting the presence of commonly dysregulated pathways. Identifying causal genes and dysregulated pathways can be helpful in providing effective treatment in these diseases. Interestingly, in spite of the considerable researches on NDDs, to the best of our knowledge, no dysregulated genes and/or pathways were reported in common across all the major NDDs so far. In this study, for the first time, we have applied the three-way interaction model, as an approach to unravel sophisticated gene interactions, to trace switch genes and significant pathways that are involved in six major NDDs. Subsequently, a gene regulatory network was constructed to investigate the regulatory communication of statistically significant triplets. Finally, KEGG pathway enrichment analysis was applied to find possible common pathways. Because of the central role of neuroinflammation and immune system responses in both pathogenic and protective mechanisms in the NDDs, we focused on immune genes in this study. Our results suggest that "cytokine-cytokine receptor interaction" pathway is enriched in all of the studied NDDs, while "osteoclast differentiation" and "natural killer cell mediated cytotoxicity" pathways are enriched in five of the NDDs each. The results of this study indicate that three pathways that include "osteoclast differentiation", "natural killer cell mediated cytotoxicity" and "cytokine-cytokine receptor interaction" are common in five, five and six NDDs, respectively. Additionally, our analysis showed that Rps27a as a switch gene, together with the gene pair {Il-18, Cx3cl1} form a statistically significant and biologically relevant triplet in the major NDDs. More specifically, we suggested that Cx3cl1 might act as a potential upstream regulator of Il-18 in microglia activation, and in turn, might be controlled with Rps27a in triggering NDDs.

Natural Killer Cell Dysfunction and Its Role in COVID-19

When facing an acute viral infection, our immune systems need to function with finite precision to enable the elimination of the pathogen, whilst protecting our bodies from immune-related damage. In many instances however this "perfect balance" is not achieved, factors such as ageing, cancer, autoimmunity and cardiovascular disease all skew the immune response which is then further distorted by viral infection. In SARS-CoV-2, although the vast majority of COVID-19 cases are mild, as of 24 August 2020, over 800,000 people have died, many from the severe inflammatory cytokine release resulting in extreme clinical manifestations such as acute respiratory distress syndrome (ARDS) and hemophagocytic lymphohistiocytosis (HLH). Severe complications are more common in elderly patients and patients with cardiovascular diseases. Natural killer (NK) cells play a critical role in modulating the immune response and in both of these patient groups, NK cell effector functions are blunted. Preliminary studies in COVID-19 patients with severe disease suggests a reduction in NK cell number and function, resulting in decreased clearance of infected and activated cells, and unchecked elevation of tissue-damaging inflammation markers. SARS-CoV-2 infection skews the immune response towards an overwhelmingly inflammatory phenotype. Restoration of NK cell effector functions has the potential to correct the delicate immune balance required to effectively overcome SARS-CoV-2 infection.

High-throughput investigation of molecular and cellular biomarkers in NMOSD

Objective

To identify candidate biomarkers associated with neuromyelitis optica spectrum disorder (NMOSD) using high-throughput technologies that broadly assay the concentrations of serum analytes and frequencies of immune cell subsets.

Methods

Sera, peripheral blood mononuclear cells (PBMCs), and matched clinical data from participants with NMOSD and healthy controls (HCs) were obtained from the Collaborative International Research in Clinical and Longitudinal Experience Study NMOSD biorepository. Flow cytometry panels were used to measure the frequencies of 39 T-cell, B-cell, regulatory T-cell, monocyte, natural killer (NK) cell, and dendritic cell subsets in unstimulated PBMCs. In parallel, multiplex proteomics assays were used to measure 46 serum cytokines and chemokines in 2 independent NMOSD and HC cohorts. Multivariable regression models were used to assess molecular and cellular profiles in NMOSD compared with HC.

Results

NMOSD samples had a lower frequency of CD16⁺CD56⁺ NK cells. Both serum cohorts and multivariable logistic regression revealed increased levels of B-cell activating factor associated with NMOSD. Interleukin 6, CCL22, and CCL3 were also elevated in 1 NMOSD cohort of the 2 analyzed. Multivariable linear regression of serum analyte levels revealed a correlation between CX3CL1 (fractalkine) levels and the number of days since most recent disease relapse.

Conclusions

Integrative analyses of cytokines, chemokines, and immune cells in participants with NMOSD and HCs provide congruence with previously identified biomarkers of NMOSD and highlight CD16⁺CD56⁺ NK cells and CX3CL1 as potential novel biomarker candidates.

Natural killer cells in multiple sclerosis: A review

As the most common non-traumatic disabling disease among adolescents, multiple sclerosis (MS) is a devastating neurological inflammatory disease of the central nervous system. Research has not yet fully elucidated its pathogenesis, but it has shown MS to be a complex, multifactorial disease with many interplaying factors. One of these factors, natural killer (NK) cells, lymphocytes of the innate immune system, have recently gained attention due to the effects of daclizumab therapy, causing an expansion of the immunoregulatory subset of NK cells. Since then, NK cells and their relation to MS have been the focus of research, with many new findings being published in the last decade. In this review, NK cells are pictured as potent cytotoxic killers, as well as unique immune-regulators. Additionally, an overview of our current knowledge regarding NK cells in MS is given. The role of NK cells in MS is reviewed in the context of well-established environmental factors and current disease modifying therapies to gain further understanding of the pathogenesis and treatment options in MS.

Integrated single cell analysis of blood and cerebrospinal fluid leukocytes in multiple sclerosis

Cerebrospinal fluid (CSF) protects the central nervous system (CNS) and analyzing CSF aids the diagnosis of CNS diseases, but our understanding of CSF leukocytes remains superficial. Here, using single cell transcriptomics, we identify a specific location-associated composition and transcriptome of CSF leukocytes. Multiple sclerosis (MS) – an autoimmune disease of the CNS – increases transcriptional diversity in blood, but increases cell type diversity in CSF including a higher abundance of cytotoxic phenotype T helper cells. An analytical approach, named cell set enrichment analysis (CSEA) identifies a cluster-independent increase of follicular (TFH) cells potentially driving the known expansion of B lineage cells in the CSF in MS. In mice, TFH cells accordingly promote B cell infiltration into the CNS and the severity of MS animal models. Immune mechanisms in MS are thus highly compartmentalized and indicate ongoing local T/B cell interaction.

Here the authors provide a single-cell characterization of cerebrospinal fluid and blood of newly diagnosed multiple sclerosis (MS) patients, revealing altered composition of lymphocyte and monocyte subsets, validated by other methods including the interrogation of the TFH subset in mouse models of MS.

The differential expression of natural killer cells in NMOSD and MS

Natural killer (NK) cells are involved in the pathogenesis of inflammatory demyelinating diseases of the central nervous system. However, the differential expressions of NK cells in the peripheral blood of patients with neuromyelitis optica spectrum disorders (NMOSD) and multiple sclerosis (MS) are unknown. This study aimed to explore the differential expressions of NK cells in NMOSD and MS and evaluate the clinical implications of this difference. We performed a cross-sectional study to investigate the expression of NK cells in the peripheral blood of patients with NMOSD (n = 78) and MS (n = 24) and of healthy controls (HC, n = 27). Furthermore, we investigated the relationship between NK cell level and disease phase in 102 patients with NMOSD and MS through Spearman correlation analysis and receiver operating characteristic (ROC) analysis. Our results showed that the median (interquartile range) NK cell levels in acute-phase NMOSD patients, remission-phase NMOSD patients, acute-phase MS patients, and HC subjects were 114.10 (64.75-153.38) cells/µL, 167.60 (116.35-266.15) cells/µL, 282.55 (140.57-368.20) cells/µL, and 221.00 (170.40-269.55) cells/µL, respectively (p < 0.001). The Spearman correlation coefficient (95%) for the relationship between NK level and disease phase in NMOSD patients was 0.366 (0.150-0.550) (p < 0.001). Furthermore, ROC analysis revealed that patients with NK cell values lower than 172.200 cells/µL were more prone to have acute-phase NMOSD than MS. In conclusion, the expression of NK cells in peripheral blood was lower in patients with NMOSD than in patients with MS in the acute phase, and a low expression of NK cells may suggest having acute-phase NMOSD rather than MS.

KIR2DL4-HLAG interaction at human NK cell-oligodendrocyte interfaces regulates IFN-γ-mediated effects

Interactions between germline-encoded natural killer (NK) cell receptors and their respective ligands on tumorigenic or virus-infected cells determine NK cell cytotoxic activity and/or cytokine secretion. NK cell cytokine responses can be augmented in and can potentially contribute to multiple sclerosis (MS), an inflammatory disease of the central nervous system focused upon the oligodendrocytes (OLs). To investigate mechanisms by which NK cells may contribute to MS pathogenesis, we developed an in vitro human model of OL-NK cell interaction. We found that activated, but not resting human NK cells form conjugates with, and mediate cytotoxicity against, human oligodendrocytes. NK cells, when in conjugate with OLs, rapidly synthesize and polarize IFN-γ toward the OLs. IFN-γ  is capable of reducing myelin oligodendrocyte and myelin associated glycoproteins (MOG and MAG) content. This activity is independent of MHC class-I mediated inhibition via KIR2DL1, but dependent upon the interaction between NK cell-expressed KIR2DL4 and its oligodendrocyte-expressed ligand, HLA-G. NK cells from patients with MS express higher levels of IFN-γ following conjugation to OLs, more actively promote in vitro reduction of MOG and MAG and have higher frequencies of the KIR2DL4 positive population. These data collectively suggest a mechanism by which NK cells can promote pathogenic effects upon OLs.

Innate, innate-like and adaptive lymphocytes in the pathogenesis of MS and EAE

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) in which the immune system damages the protective insulation surrounding the nerve fibers that project from neurons. A hallmark of MS and its animal model, experimental autoimmune encephalomyelitis (EAE), is autoimmunity against proteins of the myelin sheath. Most studies in this field have focused on the roles of CD4+ T lymphocytes, which form part of the adaptive immune system as both mediators and regulators in disease pathogenesis. Consequently, the treatments for MS often target the inflammatory CD4+ T-cell responses. However, many other lymphocyte subsets contribute to the pathophysiology of MS and EAE, and these subsets include CD8+ T cells and B cells of the adaptive immune system, lymphocytes of the innate immune system such as natural killer cells, and subsets of innate-like T and B lymphocytes such as γδ T cells, natural killer T cells, and mucosal-associated invariant T cells. Several of these lymphocyte subsets can act as mediators of CNS inflammation, whereas others exhibit immunoregulatory functions in disease. Importantly, the efficacy of some MS treatments might be mediated in part by effects on lymphocytes other than CD4+ T cells. Here we review the contributions of distinct subsets of lymphocytes on the pathogenesis of MS and EAE, with an emphasis on lymphocytes other than CD4+ T cells. A better understanding of the distinct lymphocyte subsets that contribute to the pathophysiology of MS and its experimental models will inform the development of novel therapeutic approaches.

Multi-centre validation of a flow cytometry method to identify optimal responders to interferon-beta in multiple sclerosis

BACKGROUND AND OBJECTIVES

Percentages of blood CD19+CD5+ B cells and CD8+perforin+ T lymphocytes can predict response to Interferon (IFN)-beta treatment in relapsing-remitting multiple sclerosis (RRMS) patients. We aimed to standardize their detection in a multicenter study, prior to their implementation in clinical practice.

METHODS

Fourteen hospitals participated in the study. A reference centre was established for comparison studies. Peripheral blood cells of 105 untreated RRMS patients were studied. Every sample was analyzed in duplicate in the participating centre and in the reference one by flow cytometry. When needed, participating centres corrected fluorescence compensations and negative cut-off position following reference centre suggestions. Concordance between results obtained by participating centres and by reference one was evaluated by intraclass correlation coefficients (ICC) and Spearman correlation test. Centre performance was measured by using z-scores values.

RESULTS

After results review and corrective actions implementation, overall ICC was 0.86 (CI: 0.81-0.91) for CD19+CD5+ B cell and 0.89 (CI: 0.85-0.93) for CD8+ perforin+ T cell quantification; Spearman r was 0.92 (0.89-0.95; p <0.0001) and 0.92 (0.88-0.95; p <0.0001) respectively. All centres obtained z-scores≤0.5 for both biomarkers.

CONCLUSION

Homogenous percentages of CD19+CD5+ B cells and CD8 perforin+ T lymphocytes can be obtained if suitable compensation values and negative cut-off are pre-established.

Multiple Immune-Inflammatory and Oxidative and Nitrosative Stress Pathways Explain the Frequent Presence of Depression in Multiple Sclerosis

Patients with a diagnosis of multiple sclerosis (MS) or major depressive disorder (MDD) share a wide array of biological abnormalities which are increasingly considered to play a contributory role in the pathogenesis and pathophysiology of both illnesses. Shared abnormalities include peripheral inflammation, neuroinflammation, chronic oxidative and nitrosative stress, mitochondrial dysfunction, gut dysbiosis, increased intestinal barrier permeability with bacterial translocation into the systemic circulation, neuroendocrine abnormalities and microglial pathology. Patients with MS and MDD also display a wide range of neuroimaging abnormalities and patients with MS who display symptoms of depression present with different neuroimaging profiles compared with MS patients who are depression-free. The precise details of such pathology are markedly different however. The recruitment of activated encephalitogenic Th17 T cells and subsequent bidirectional interaction leading to classically activated microglia is now considered to lie at the core of MS-specific pathology. The presence of activated microglia is common to both illnesses although the pattern of such action throughout the brain appears to be different. Upregulation of miRNAs also appears to be involved in microglial neurotoxicity and indeed T cell pathology in MS but does not appear to play a major role in MDD. It is suggested that the antidepressant lofepramine, and in particular its active metabolite desipramine, may be beneficial not only for depressive symptomatology but also for the neurological symptoms of MS. One clinical trial has been carried out thus far with, in particular, promising MRI findings.

NK cells in autoimmune diseases: Linking innate and adaptive immune responses

The pathogenesis of autoimmunity remains to be fully elucidated, although the contribution of genetic and environmental factors is generally recognized. Despite autoimmune conditions are principally due to T and B lymphocytes, NK cells also appear to play a role in the promotion and/or maintenance of altered adaptive immune responses or in peripheral tolerance mechanisms. Although NK cells are components of the innate immune system, they shows characteristics of the adaptive immune system, such as the expansion of pathogen-specific cells, the generation of long-lasting "memory" cells able to persist upon cognate antigen encounter, and the possibility to induce an increased secondary recall response to re-challenge. Human NK cells are generally identified as CD56+CD3-, conversely CD56+CD3+ cells represent a mixed population of NK-like T (NK T) cells and antigen-experienced T cells showing the up-regulation of several NK cell markers. CD56dim constitute about 90% of NK cells in the peripheral blood, they are mature and involved in cytotoxicity responses; CD56bright instead are more immature, mostly involved in cytokine production, having only a limited role in cytolytic responses, keen to leave the blood vessels as the principal population observed in lymph nodes. NK cells have been identified also in non-lymphoid tissues since, in pathologic conditions, they can quickly reach the target organs. A cross-talk between NK with dendritic cells and T cells is established throughout different receptor-ligand bindings. Several studies support the correlation between NK cell number and/or functional alterations, such as a defective cytotoxic activity and several autoimmune conditions. Among the different autoimmune pathologies and even within the same disease, NK cell function is significantly different either promoting or even protecting against the onset of the autoimmune condition. In this Review, we discuss recent literature supporting the role played by NK cells, as a bridge between innate and adaptive immunity, in the onset of autoimmune diseases.

Western lifestyle and immunopathology of multiple sclerosis

There is increasing evidence for a sudden and unprecedented rise in the incidence of multiple sclerosis (MS) in Westernized countries over the past decades, emphasizing the role of environmental factors. Among many candidates, rapid changes in dietary habits seem to play a role in the pathogenesis of MS. Here, we summarize and discuss the available evidence for the role of dietary nutrients, such as table salt, fatty acids, and flavonoids, in the development and pathogenesis of MS. We also discuss new and emerging risk factors accompanying Western lifestyle, such as shift work, sleep, and circadian disruption.

Decreased NK cell immunity in kidney transplant recipients late post-transplant and increased NK-cell immunity in patients with recurrent miscarriage

BACKGROUND

There is evidence that NK-cell reactivity might affect graft outcome in transplant recipients and pregnancy in women.

METHOD

NK-cell subsets were determined in whole blood using eight-colour-fluorescence flow cytometry in patients before and after renal transplantation, patients with recurrent miscarriage (RM) and healthy controls (HC).

RESULTS

Patients late post-transplant (late-Tx) with functioning renal transplants showed abnormally low CD56dimCD16+ NK-cells containing both perforin and granzyme (vs HC p = 0.021) whereas RM patients exhibited abnormally high numbers of these cells (vs HC p = 0.043). CD56dimCD16+perforin+granzyme+ NK-cell counts were strikingly different between the two patient groups (p<0.001). In addition, recipients late-Tx showed abnormally low CD8+ NK-cells (vs HC p<0.001) in contrast to RM patients who showed an abnormal increase (vs HC p = 0.008). CD8+ NK-cell counts were strongly different between the two patient groups (p<0.001). Higher perforin+granzyme+CD56dimCD16+ and CD8+ NK-cells were associated with impaired graft function (p = 0.044, p = 0.032). After in-vitro stimulation, CD56dimCD16+ and CD56brightCD16dim/- NK-cells showed strong upregulation of CD107a and IFNy, whereas the content of perforin decreased dramatically as a consequence of perforin release. Recipients late post-Tx showed less in-vitro perforin release (= less cytotoxicity) than HC (p = 0.037) and lower perforin release was associated with good graft function (r = 0.738, p = 0.037). Notably, we observed strong in-vitro perforin release in 2 of 6 investigated RM patients. When circulating IL10+CD56bright NK-cells were analyzed, female recipients late post-Tx (n = 9) showed significantly higher relative and absolute cell numbers than RM patients (p = 0.002 and p = 0.018, respectively); and high relative and absolute IL10+CD56bright NK-cell numbers in transplant recipients were associated with low serum creatinine (p = 0.004 and p = 0.012) and high glomerular filtration rate (p = 0.011 and p = 0.002, respectively). Female recipients late post-Tx exhibited similar absolute but higher relative numbers of IL10+IFNy- NK-cells than RM patients (p>0.05 and p = 0.016, respectively).

CONCLUSION

NK-cells with lower cytotoxicity and immunoregulatory function might contribute to good long-term graft outcome, whereas circulating NK-cells with normal or even increased cytotoxicity and less immunoregulatory capacity are observed in patients with RM.

6-Mercaptopurine modifies cerebrospinal fluid T cell abnormalities in paediatric opsoclonus-myoclonus as steroid sparer

The purpose of this study was to evaluate the capacity of 6-mercaptopurine (6-MP), a known immunosuppressant, to normalize cerebrospinal fluid (CSF) lymphocyte frequencies in opsoclonus-myoclonus syndrome (OMS) and function as a steroid sparer. CSF and blood lymphocytes were immunophenotyped in 11 children with OMS (without CSF B cell expansion) using a comprehensive panel of cell surface adhesion, activation and maturation markers by flow cytometry, and referenced to 18 paediatric controls. Drug metabolites, lymphocyte counts and liver function tests were used clinically to monitoring therapeutic range and toxicity. In CSF, adjunctive oral 6-MP was associated with a 21% increase in the low percentage of CD4⁺ T cells in OMS, restoring the CD4/CD8 ratio. The percentage of CD4⁺ T cells that were interferon (IFN)-γ⁺ was reduced by 66%, shifting the cytokine balance away from T helper type 1 (Th1) (proinflammatory) predominance. The percentage of natural killer (NK) cells decreased significantly in CSF (-32%) and blood (-67 to -82%). Low blood absolute lymphocyte count was more predictive of improvement in CSF lymphocyte proportions (correlated with % CD4⁺ T cells) than the 6-thioguanine level (no correlation). 6-MP was difficult to titrate: 50% achieved the target absolute lymphocyte count (< 1·5 K/mm); 20%, the 'therapeutic' 6-thioguanine level; and 40% the non-toxic 6-methylmercaptopurine level. Side effects and transaminase elevation were mild and reversible. Clinical steroid-sparing properties and lowered relapse frequency were demonstrated. 6-MP displayed unique pharmacodynamic properties that may be useful in OMS and other autoimmune disorders. Its steroid sparer capacity is limited to children in whom the therapeutic window can be reached without limiting pharmacokinetic factors or side effects.

Promise, Progress, and Pitfalls in the Search for Central Nervous System Biomarkers in Neuroimmunological Diseases: A Role for Cerebrospinal Fluid Immunophenotyping

Biomarkers are central to the translational medicine strategic focus, though strict criteria need to be applied to their designation and utility. They are one of the most promising areas of medical research, but the "biomarker life-cycle" must be understood to avoid false-positive and false-negative results. Molecular biomarkers will revolutionize the treatment of neurological diseases, but the rate of progress depends on a bold, visionary stance by neurologists, as well as scientists, biotech and pharmaceutical industries, funding agencies, and regulators. One important tool in studying cell-specific biomarkers is multiparameter flow cytometry. Cerebrospinal fluid immunophenotyping, or immune phenotypic subsets, captures the biology of intrathecal inflammatory processes, and has the potential to guide personalized immunotherapeutic selection and monitor treatment efficacy. Though data exist for some disorders, they are surprisingly lacking in many others, identifying a serious deficit to be overcome. Flow cytometric immunophenotyping provides a valuable, available, and feasible "window" into both adaptive and innate components of neuroinflammation that is currently underutilized.

Biological activity of glatiramer acetate on Treg and anti-inflammatory monocytes persists for more than 10years in responder multiple sclerosis patients

Glatiramer acetate (GA) is a widely used treatment for multiple sclerosis (MS), with incompletely defined mechanism of action. Short-term studies suggested its involvement in the modulation of anti-inflammatory cytokines and regulatory T cells (Treg), while long-term effect is still unknown. To investigate this aspect, we analyzed by flow-cytometry peripheral-blood Treg, natural killer (NK), CD4 and CD8 T-cells and anti-inflammatory CD14⁺CD163⁺ monocytes from 37 healthy donor and 90 RRMS patients divided in untreated, treated with GA for 12months and from 34 to 192months. While NK, CD4 and CD8 T-cells did not show any significant differences among groups over time, we demonstrated that GA increased the anti-inflammatory monocytes and restored the Treg level in both GA-treated groups. Both these effects are a characteristic of responder patients and are observed not just in short-term but even after as long as a decade of GA treatment.

Regulatory Functions of Natural Killer Cells in Multiple Sclerosis

There is increasing evidence that natural killer (NK) cells exhibit regulatory features. Among them, CD56^bright NK cells have been suggested to play a major role in controlling T cell responses and maintaining homeostasis. Dysfunction in NK cell-mediated regulatory features has been recently described in untreated multiple sclerosis (MS), suggesting a contribution to MS pathogenesis. Moreover, biological disease-modifying treatments effective in MS apparently enhance the frequencies and/or regulatory function of NK cells, further pointing toward an immunoprotective role of NK cells in MS. Here, we summarize the current knowledge on the regulatory functions of NK cells, based on their interactions with other cells belonging to the innate compartment, as well as with adaptive effector cells. We review the more recent data reporting disruption of NK cell/T cell interactions in MS and discuss how disease-modifying treatments for MS affect NK cells.

Environmental factors in autoimmune diseases and their role in multiple sclerosis

An increase in autoimmune diseases poses a socioeconomic challenge worldwide. Predisposing genetic risk has been identified, yet environmental factors make up a significant part of the risk in disease initiation and propagation. Next to improved hygiene and a gross reduction of infections, changes in dietary habits are one of the most evident Western lifestyle factors potentially associated with the increase in autoimmune diseases. Growing evidence suggests that particularly a typical 'Western diet', rich in saturated fat and salt and related pathologies can have a profound impact on local and systemic immune responses under physiologic and autoimmune conditions such as in multiple sclerosis (MS). In this review, we discuss recent findings on environmental factors influencing autoimmunity with an emphasis on the impact of 'Western diet' on immune homeostasis and gut microbiota in MS.

Dysregulation of Chemokine/Chemokine Receptor Axes and NK Cell Tissue Localization during Diseases

Chemokines are small chemotactic molecules that play key roles in physiological and pathological conditions. Upon signaling via their specific receptors, chemokines regulate tissue mobilization and trafficking of a wide array of immune cells, including natural killer (NK) cells. Current research is focused on analyzing changes in chemokine/chemokine receptor expression during various diseases to interfere with pathological trafficking of cells or to recruit selected cell types to specific tissues. NK cells are a heterogeneous lymphocyte population comprising several subsets endowed with distinct functional properties and mainly representing distinct stages of a linear development process. Because of their different functional potential, the type of subset that accumulates in a tissue drives the final outcome of NK cell-regulated immune response, leading to either protection or pathology. Correspondingly, chemokine receptors, including CXCR4, CXCR3, and CX₃CR1, are differentially expressed by NK cell subsets, and their expression levels can be modulated during NK cell activation. At first, this review will summarize the current knowledge on the contribution of chemokines to the localization and generation of NK cell subsets in homeostasis. How an inappropriate chemotactic response can lead to pathology and how chemokine targeting can therapeutically affect tissue recruitment/localization of distinct NK cell subsets will also be discussed.

Human CD56bright NK Cells: An Update

Human NK cells can be subdivided into various subsets based on the relative expression of CD16 and CD56. In particular, CD56(bright)CD16(-/dim) NK cells are the focus of interest. They are considered efficient cytokine producers endowed with immunoregulatory properties, but they can also become cytotoxic upon appropriate activation. These cells were shown to play a role in different disease states, such as cancer, autoimmunity, neuroinflammation, and infection. Although their phenotype and functional properties are well known and have been extensively studied, their lineage relationship with other NK cell subsets is not fully defined, nor is their precise hematopoietic origin. In this article, we summarize recent studies about CD56(bright) NK cells in health and disease and briefly discuss the current controversies surrounding them.

KIR2DL2 inhibitory pathway enhances Th17 cytokine secretion by NK cells in response to herpesvirus infection in multiple sclerosis patients

We have previously demonstrated that multiple sclerosis (MS) patients with KIR2DL2 expression on Natural killer (NK) cells are more susceptible to herpes simplex virus 1 (HSV-1) infection. We explored cytokine expression by NK cells during HSV-1 infection in association with KIR2DL2 expression. MS KIR2DL2(+) NK cells failed to control HSV-1 infection and secreted high levels of Th17 cytokines, while MS KIR2DL2(-) NK cells released Th1 cytokines, mainly IFN-gamma. Our data showed, for the first time, a peculiar Th17 cytokine secretion by MS KIR2DL2(+) NK cells in the presence of HSV-1 infection, that could be implicated in MS pathogenesis.

Increased natural killer cell chemotaxis to CXCL12 in patients with multiple sclerosis

Multiple sclerosis (MS) is an inflammatory and neurodegenerative disease characterized by leukocyte infiltration into the central nervous system (CNS). Migration of lymphocyte subpopulations towards CXCL12 was analyzed coupled to six-color flow cytometry in untreated patients in the remitting phase, during relapse, in patients with clinically isolated syndrome (CIS), and in healthy volunteers. Significantly higher migration rates of natural killer cells (CD45+CD3-CD16/56+) were observed in patients in remission and CIS patients than in patients during relapse and in controls. Moreover, the frequency of CD3-CD16/56+CXCR4+ cells is higher in patients in remission and in CIS patients, but not during relapse.