Expansion of Neutrophils and Classical and Nonclassical Monocytes as a Hallmark in Relapsing-Remitting Multiple Sclerosis

High frequency of circulating non-classical monocytes is associated with stable remission in relapsing-remitting multiple sclerosis

'No evidence of disease activity (NEDA)', judged by clinical and radiological findings, is a therapeutic goal in patients with multiple sclerosis (MS). It is, however, unclear if distinct biological mechanisms contribute to the maintenance of NEDA. To clarify the immunological background of long-term disease stability defined by NEDA, circulating immune cell subsets in patients with relapsing-remitting MS (RRMS) were analyzed using flow cytometry. Patients showing long-term NEDA (n = 31) had significantly higher frequencies of non-classical monocytes (NCMs) (6.1% vs 1.4%) and activated regulatory T cells (Tregs; 2.1% vs 1.6%) than those with evidence of disease activity (n = 8). The NCM frequency and NCMs to classical monocytes ratio (NCM/CM) positively correlated with activated Treg frequency and duration of NEDA. Co-culture assays demonstrated that NCMs could increase the frequency of activated Tregs and the expression of PD-L1, contributing to development of Tregs, was particularly high in NCMs from patients with NEDA. Collectively, NCMs contribute to stable remission in patients with RRMS, possibly by increasing activated Treg frequency. In addition, the NCM frequency and NCM/CM ratio had high predictive values for disease stability (AUC = 0.97 and 0.94, respectively), suggesting these markers are potential predictors of a long-term NEDA status in RRMS.

Current Knowledge about Nonclassical Monocytes in Patients with Multiple Sclerosis, a Systematic Review

Monocytes play a critical role in the initiation and progression of multiple sclerosis (MS). Recent research indicates the importance of considering the roles of monocytes in the management of MS and the development of effective interventions. This systematic review examined published research on the roles of nonclassical monocytes in MS and how they influence disease management. Reputable databases, such as PubMed, EMBASE, Cochrane, and Google Scholar, were searched for relevant studies on the influence of monocytes on MS. The search focused on studies on humans and patients with experimental autoimmune encephalomyelitis (EAE) published between 2014 and 2024 to provide insights into the study topic. Fourteen articles that examined the role of monocytes in MS were identified; the findings reported in these articles revealed that nonclassical monocytes could act as MS biomarkers, aid in the development of therapeutic interventions, reveal disease pathology, and improve approaches for monitoring disease progression. This review provides support for the consideration of monocytes when researching effective diagnostics, therapeutic interventions, and procedures for managing MS pathophysiology. These findings may guide future research aimed at gaining further insights into the role of monocytes in MS.

A pilot study of monocytes in relapsing remitting multiple sclerosis: Correlation with disease activity

Background: Numerous immune cells are involved in developing multiple sclerosis (MS). Monocytes are believed to be the first to enter the brain and initiate inflammation. The role of monocyte subtypes in MS needs to be better understood. Objective: The current study aims to investigate the presence of different subsets of monocytes in relapsing-remitting MS (RRMS) Egyptian patients and their correlation with disease activity. Methods: This study included 44 RRMS patients (22 patients in relapse, 22 patients in remission), diagnosed according to the 2017 MacDonalds criteria, and 44 matched healthy controls. Personal and medical histories were taken from the patients, and the Expanded Disability Status Scale (EDSS) was used to evaluate the degree of impairment. Characterization of peripheral blood monocyte subsets was done by flow cytometry for all participants. Results: The percentage of classical, intermediate, and non-classical monocyte subsets showed a significant increase in RRMS patients than controls with p-values of 0.029, 0.049, and 0.043, respectively. In the RRMS patients, there were no statistically significant correlations (p-values >0.05) between the EDSS scores, the duration of disease, and number of relapses in the past year and the percentages of the various monocyte subsets. Furthermore, there were no significant differences in the percentage of each monocyte subset between RRMS patients in remission and those experiencing a relapse (p-values >0.05). However, patients with evidence of activity in magnetic resonance imaging (MRI) had a significantly high percentage of non-classical monocytes with a p-value of 0.002. Conclusion: In RRMS patients, the three monocyte subsets (classical, non-classical and intermediate) increase significantly regardless of the disease activity. This increase denotes the vital role of monocytes and innate immunity in MS pathology, especially the non-classical monocyte subset. These findings suggest that monocytes might be a promising MS therapeutic target.

Disease activity drives divergent epigenetic and transcriptomic reprogramming of monocyte subpopulations in systemic lupus erythematosus

OBJECTIVES

Systemic lupus erythematosus (SLE) is characterised by systemic inflammation involving various immune cell types. Monocytes, pivotal in promoting and regulating inflammation in SLE, differentiate from classic monocytes into intermediate and non-classic monocytes, assuming diverse roles and changing their proportions in inflammation. In this study, we investigated the epigenetic and transcriptomic profiles of these and novel monocyte subsets in SLE in relation to activity and progression.

METHODS

We obtained the DNA methylomes and transcriptomes of classic, intermediate, non-classic monocytes in patients with SLE (at first and follow-up visits) and healthy donors. We integrated these data with single-cell transcriptomics of SLE and healthy donors and interrogated their relationships with activity and progression.

RESULTS

In addition to shared DNA methylation and transcriptomic alterations associated with a strong interferon signature, we identified monocyte subset-specific alterations, especially in DNA methylation, which reflect an impact of SLE on monocyte differentiation. SLE classic monocytes exhibited a proinflammatory profile and were primed for macrophage differentiation. SLE non-classic monocytes displayed a T cell differentiation-related phenotype, with Th17-regulating features. Changes in monocyte proportions, DNA methylation and expression occurred in relation to disease activity and involved the STAT pathway. Integration of bulk with single-cell RNA sequencing datasets revealed disease activity-dependent expansion of SLE-specific monocyte subsets, further supported the interferon signature for classic monocytes, and associated intermediate and non-classic populations with exacerbated complement activation.

CONCLUSIONS

Disease activity in SLE drives a subversion of the epigenome and transcriptome programme in monocyte differentiation, impacting the function of different subsets and allowing to generate predictive methods for activity and progression.

HLA-DRB1*15:01 and the MERTK Gene Interact to Selectively Influence the Profile of MERTK-Expressing Monocytes in Both Health and MS

BACKGROUND AND OBJECTIVES

HLA-DRB1*15:01 (DR15) and MERTK are 2 risk genes for multiple sclerosis (MS). The variant rs7422195 is an expression quantitative trait locus for MERTK in CD14+ monocytes; cells with phagocytic and immunomodulatory potential. We aimed to understand how drivers of disease risk and pathogenesis vary with HLA and MERTK genotype and disease activity.

METHODS

We investigated how proportions of monocytes vary with HLA and MERTK genotype and disease activity in MS. CD14+ monocytes were isolated from patients with MS at relapse (n = 40) and 3 months later (n = 23). Healthy controls (HCs) underwent 2 blood collections 3 months apart. Immunophenotypic profiling of monocytes was performed by flow cytometry. Methylation of 35 CpG sites within and near the MERTK gene was assessed in whole blood samples of individuals experiencing their first episode of clinical CNS demyelination (n = 204) and matched HCs (n = 345) using an Illumina EPIC array.

RESULTS

DR15-positive patients had lower proportions of CD14+ MERTK+ monocytes than DR15-negative patients, independent of genotype at the MERTK SNP rs7422195. Proportions of CD14+ MERTK+ monocytes were further reduced during relapse in DR15-positive but not DR15-negative patients. Patients homozygous for the major G allele at rs7422195 exhibited higher proportions of CD14+ MERTK+ monocytes at both relapse and remission compared with controls. We observed that increased methylation of the MERTK gene was significantly associated with the presence of DR15.

DISCUSSION

DR15 and MERTK genotype independently influence proportions of CD14+ MERTK+ monocytes in MS. We confirmed previous observations that the MERTK risk SNP rs7422195 is associated with altered MERTK expression in monocytes. We identified that expression of MERTK is stratified by disease in people homozygous for the major G allele of rs7422195. The finding that the proportion of CD14+ MERTK+ monocytes is reduced in DR15-positive individuals supports prior data identifying genetic links between these 2 loci in influencing MS risk. DR15 genotype-dependent alterations in methylation of the MERTK gene provides a molecular link between these loci and identifies a potential mechanism by which MERTK expression is influenced by DR15. This links DR15 haplotype to MS susceptibility beyond direct influence on antigen presentation and suggests the need for HLA-based stratification of approaches to MERTK as a therapeutic target.

Treated and Untreated Primary Progressive Multiple Sclerosis: Walkthrough Immunological Changes of Monocytes and T Regulatory Cells

The objective of this study was to investigate regulatory T cells (Tregs) and monocytes; specifically, the expression of CTLA-4 (CD152) and FOXP3+ in CD4+CD25+ Tregs and the expression of CD40+ and CD192+ monocyte subpopulations in subjects with primary progressive multiple sclerosis (PPMS). Immunological analysis was conducted on peripheral blood samples collected from the 28 PPMS subjects (15 treated with ocrelizumab and 13 untreated PPMS subjects) and 10 healthy control subjects (HCs). The blood samples were incubated with antihuman CD14, CD16, CD40, and CD192 antibodies for monocytes and antihuman CD4, CD25, FOXP3, and CTLA-4 antibodies for lymphocytes. The study results showed that in comparison to HCs both ocrelizumab treated (N = 15) and untreated (N = 13) PPMS subjects had significantly increased percentages of CTLA-4+ and FOXP3+ in CD4+CD25+ Tregs. Further, ocrelizumab treated PPMS subjects, compared to the untreated ones, had significantly decreased percentages of CD192+ and CD40+ nonclassical monocytes. Increased percentages of CTLA-4+ and FOXP3+ in CD4+CD25+ Tregs in both ocrelizumab treated and untreated PPMS subjects indicates the suppressive (inhibitory) role of Tregs in abnormal immune responses in PPMS subjects. Decreased percentages of CD40+ and CD192+ non-classical CD14+CD16++ monocytes for treated compared to untreated PPMS subjects suggests a possible role for ocrelizumab in dampening CNS inflammation.

Neutropenia following immune-depletion, notably CD20 targeting, therapies in multiple sclerosis

Neutropenia serves as a risk factor for severe infection and is a consequence of some immune-depleting immunotherapies. This occurs in people with multiple sclerosis following chemotherapy-conditioning in haematopoietic stem cell transplantation and potent B cell targeting agents. Whilst CD52 is expressed by neutrophils and may contribute to early-onset neutropenia following alemtuzumab treatment, deoxycytidine kinase and CD20 antigen required for activity of cladribine tablets, off-label rituximab, ocrelizumab, ofatumumab and ublituximab are not or only weakly expressed by neutrophils. Therefore, alternative explanations are needed for the rare occurrence of early and late-onset neutropenia following such treatments. This probably occurs due to alterations in the balance of granulopoiesis and neutrophil removal. Neutrophils are short-lived, and their removal may be influenced by drug-associated infections, the killing mechanisms of the therapies and amplified by immune dyscrasia due to influences on neutropoiesis following growth factor rerouting for B cell recovery and cytokine deficits following lymphocyte depletion. This highlights the small but evident neutropenia risks following sustained B cell depletion with some 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.

Alpha Calcitonin Gene-related Peptide, Neuropeptide Y, and Substance P as Biomarkers for Diagnosis and Disease Activity and Severity in Multiple Sclerosis

BACKGROUND

Alpha calcitonin gene-related peptide (aCGRP), neuropeptide Y (NPY), and substance P (SP) are neuropeptides that have emerged recently as potent immunomodulatory factors with potential as novel biomarkers and therapeutic targets in multiple sclerosis (MS).

OBJECTIVE

The study aimed to detect serum levels of aCGRP, NPY, and SP in MS patients versus healthy controls and their association with disease activity and severity.

METHODS

Serum levels were measured in MS patients and age and sex-matched healthy controls using ELISA.

RESULTS

We included 67 MS patients: 61 relapsing-remitting MS (RR-MS) and 6 progressive MS (PR-MS), and 67 healthy controls. Serum NPY level was found to be lower in MS patients than in healthy controls (p < 0.001). Serum aCGRP level was higher in PR-MS compared to RR-MS (p = 0.007) and healthy controls (p = 0.001), and it positively correlated with EDSS (r = 0.270, p = 0.028). Serum NPY level was significantly higher in RR-MS and PR-MS than in healthy controls (p < 0.001 and p = 0.001, respectively), and it was lower in patients with mild or moderate/severe disease than in healthy controls (p < 0.001). Significant inverse correlations were found between SP level and MS disease duration (r = -0.279, p = 0.022) and duration of current DMT (r = -0.315, p = 0.042).

CONCLUSION

Lower serum levels of NPY were revealed in MS patients compared to healthy controls. Since serum levels of aCGRP are significantly associated with disease activity and severity, it is a potential disease progression marker.

Neutrophil heterogeneity and aging: implications for COVID-19 and wound healing

Neutrophils play a critical role in the immune response to infection and tissue injury. However, recent studies have shown that neutrophils are a heterogeneous population with distinct subtypes that differ in their functional properties. Moreover, aging can alter neutrophil function and exacerbate immune dysregulation. In this review, we discuss the concept of neutrophil heterogeneity and how it may be affected by aging. We then examine the implications of neutrophil heterogeneity and aging for COVID-19 pathogenesis and wound healing. Specifically, we summarize the evidence for neutrophil involvement in COVID-19 and the potential mechanisms underlying neutrophil recruitment and activation in this disease. We also review the literature on the role of neutrophils in the wound healing process and how aging and neutrophil heterogeneity may impact wound healing outcomes. Finally, we discuss the potential for neutrophil-targeted therapies to improve clinical outcomes in COVID-19 and wound healing.

The role of biogenic amines in the modulation of monocytes in autoimmune neuroinflammation

Multiple sclerosis (MS) is inflammatory demyelinating and neurodegenerative disease of the central nervous system (CNS) with autoimmune mechanism of development. The study of the neuroimmune interactions is one of the most developing directions in the research of the pathogenesis of MS. The influence of biogenic amines on the pathogenesis of experimental autoimmune encephalomyelitis (EAE) and MS was shown by the modulation of subsets of T-helper cells and B-cells, which plays a crucial role in the autoimmunity of the CNS. However, along with T- and B-cells the critical involvement of mononuclear phagocytes such as dendritic cells, macrophages, and monocytes in the development of neuroinflammation also was shown. It was demonstrated that the activation of microglial cells (resident macrophages of the CNS) could initiate the neuroinflammation in the EAE, suggesting their role at an early stage of the disease. In contrast, monocytes, which migrate from the periphery into the CNS through the blood-brain barrier, mediate the effector phase of the disease and cause neurological disability in EAE. In addition, the clinical efficacy of the therapy with depletion of the monocytes in EAE was shown, suggesting their crucial role in the autoimmunity of the CNS. Biogenic amines, such as epinephrine, norepinephrine, dopamine, and serotonin are direct mediators of the neuroimmune interaction and may affect the pathogenesis of EAE and MS by modulating the immune cell activity and cytokine production. The anti-inflammatory effect of targeting the biogenic amines receptors on the pathogenesis of EAE and MS by suppression of Th17- and Th1-cells, which are critical for the CNS autoimmunity, was shown. However, the latest data showed the potential ability of biogenic amines to affect the functions of the mononuclear phagocytes and their involvement in the modulation of neuroinflammation. This article reviews the literature data on the role of monocytes in the pathogenesis of EAE and MS. The data on the effect of targeting of biogenic amine receptors on the function of monocytes are presented.

Mechanisms underlying the beneficial effects of physical exercise on multiple sclerosis: focus on immune cells

Multiple sclerosis (MS) is a prevalent neuroimmunological illness that leads to neurological disability in young adults. Although the etiology of MS is heterogeneous, it is well established that aberrant activity of adaptive and innate immune cells plays a crucial role in its pathogenesis. Several immune cell abnormalities have been described in MS and its animal models, including T lymphocytes, B lymphocytes, dendritic cells, neutrophils, microglia/macrophages, and astrocytes, among others. Physical exercise offers a valuable alternative or adjunctive disease-modifying therapy for MS. A growing body of evidence indicates that exercise may reduce the autoimmune responses triggered by immune cells in MS. This is partially accomplished by restricting the infiltration of peripheral immune cells into the central nervous system (CNS) parenchyma, curbing hyperactivation of immune cells, and facilitating a transition in the balance of immune cells from a pro-inflammatory to an anti-inflammatory state. This review provides a succinct overview of the correlation between physical exercise, immune cells, and MS pathology, and highlights the potential benefits of exercise as a strategy for the prevention and treatment of MS.

Effects of Cannabidiol on Innate Immunity: Experimental Evidence and Clinical Relevance

Cannabidiol (CBD) is the main non-psychotropic cannabinoid derived from cannabis (Cannabis sativa L., fam. Cannabaceae). CBD has received approval by the Food and Drug Administration (FDA) and European Medicines Agency (EMA) for the treatment of seizures associated with Lennox-Gastaut syndrome or Dravet syndrome. However, CBD also has prominent anti-inflammatory and immunomodulatory effects; evidence exists that it could be beneficial in chronic inflammation, and even in acute inflammatory conditions, such as those due to SARS-CoV-2 infection. In this work, we review available evidence concerning CBD's effects on the modulation of innate immunity. Despite the lack so far of clinical studies, extensive preclinical evidence in different models, including mice, rats, guinea pigs, and even ex vivo experiments on cells from human healthy subjects, shows that CBD exerts a wide range of inhibitory effects by decreasing cytokine production and tissue infiltration, and acting on a variety of other inflammation-related functions in several innate immune cells. Clinical studies are now warranted to establish the therapeutic role of CBD in diseases with a strong inflammatory component, such as multiple sclerosis and other autoimmune diseases, cancer, asthma, and cardiovascular diseases.

Specific myeloid signatures in peripheral blood differentiate active and rare clinical phenotypes of multiple sclerosis

Current understanding of Multiple Sclerosis (MS) pathophysiology implicates perturbations in adaptive cellular immune responses, predominantly T cells, in Relapsing-Remitting forms (RRMS). Nevertheless, from a clinical perspective MS is a heterogeneous disease reflecting the heterogeneity of involved biological systems. This complexity requires advanced analysis tools at the single-cell level to discover biomarkers for better patient-group stratification. We designed a novel 44-parameter mass cytometry panel to interrogate predominantly the role of effector and regulatory subpopulations of peripheral blood myeloid subsets along with B and T-cells (excluding granulocytes) in MS, assessing three different patient cohorts: RRMS, PPMS (Primary Progressive) and Tumefactive MS patients (TMS) (n=10, 8, 14 respectively). We further subgrouped our cohort into inactive or active disease stages to capture the early underlying events in disease pathophysiology. Peripheral blood analysis showed that TMS cases belonged to the spectrum of RRMS, whereas PPMS cases displayed different features. In particular, TMS patients during a relapse stage were characterized by a specific subset of CD11c+CD14+ CD33+, CD192+, CD172+-myeloid cells with an alternative phenotype of monocyte-derived macrophages (high arginase-1, CD38, HLA-DR-low and endogenous TNF-a production). Moreover, TMS patients in relapse displayed a selective CD4 T-cell lymphopenia of cells with a Th2-like polarised phenotype. PPMS patients did not display substantial differences from healthy controls, apart from a trend toward higher expansion of NK cell subsets. Importantly, we found that myeloid cell populations are reshaped under effective disease-modifying therapy predominantly with glatiramer acetate and to a lesser extent with anti-CD20, suggesting that the identified cell signature represents a specific therapeutic target in TMS. The expanded myeloid signature in TMS patients was also confirmed by flow cytometry. Serum neurofilament light-chain levels confirmed the correlation of this myeloid cell signature with indices of axonal injury. More in-depth analysis of myeloid subsets revealed an increase of a subset of highly cytolytic and terminally differentiated NK cells in PPMS patients with leptomeningeal enhancement (active-PPMS), compared to those without (inactive-PPMS). We have identified previously uncharacterized subsets of circulating myeloid cells and shown them to correlate with distinct disease forms of MS as well as with specific disease states (relapse/remission).

Neutrophils in aging and aging‐related pathologies

Over the past millennia, life expectancy has drastically increased. While a mere 25 years during Bronze and Iron ages, life expectancy in many European countries and in Japan is currently above 80 years. Such an increase in life expectancy is a result of improved diet, life style, and medical care. Yet, increased life span and aging also represent the most important non-modifiable risk factors for several pathologies including cardiovascular disease, neurodegenerative diseases, and cancer. In recent years, neutrophils have been implicated in all of these pathologies. Hence, this review provides an overview of how aging impacts neutrophil production and function and conversely how neutrophils drive aging-associated pathologies. Finally, we provide a perspective on how processes of neutrophil-driven pathologies in the context of aging can be targeted therapeutically.

Identifying disease-critical cell types and cellular processes by integrating single-cell RNA-sequencing and human genetics

Genome-wide association studies provide a powerful means of identifying loci and genes contributing to disease, but in many cases, the related cell types/states through which genes confer disease risk remain unknown. Deciphering such relationships is important for identifying pathogenic processes and developing therapeutics. In the present study, we introduce sc-linker, a framework for integrating single-cell RNA-sequencing, epigenomic SNP-to-gene maps and genome-wide association study summary statistics to infer the underlying cell types and processes by which genetic variants influence disease. The inferred disease enrichments recapitulated known biology and highlighted notable cell-disease relationships, including γ-aminobutyric acid-ergic neurons in major depressive disorder, a disease-dependent M-cell program in ulcerative colitis and a disease-specific complement cascade process in multiple sclerosis. In autoimmune disease, both healthy and disease-dependent immune cell-type programs were associated, whereas only disease-dependent epithelial cell programs were prominent, suggesting a role in disease response rather than initiation. Our framework provides a powerful approach for identifying the cell types and cellular processes by which genetic variants influence disease.

Development of a standardized and validated flow cytometry approach for monitoring of innate myeloid immune cells in human blood

Innate myeloid cell (IMC) populations form an essential part of innate immunity. Flow cytometric (FCM) monitoring of IMCs in peripheral blood (PB) has great clinical potential for disease monitoring due to their role in maintenance of tissue homeostasis and ability to sense micro-environmental changes, such as inflammatory processes and tissue damage. However, the lack of standardized and validated approaches has hampered broad clinical implementation. For accurate identification and separation of IMC populations, 62 antibodies against 44 different proteins were evaluated. In multiple rounds of EuroFlow-based design-testing-evaluation-redesign, finally 16 antibodies were selected for their non-redundancy and separation power. Accordingly, two antibody combinations were designed for fast, sensitive, and reproducible FCM monitoring of IMC populations in PB in clinical settings (11-color; 13 antibodies) and translational research (14-color; 16 antibodies). Performance of pre-analytical and analytical variables among different instruments, together with optimized post-analytical data analysis and reference values were assessed. Overall, 265 blood samples were used for design and validation of the antibody combinations and in vitro functional assays, as well as for assessing the impact of sample preparation procedures and conditions. The two (11- and 14-color) antibody combinations allowed for robust and sensitive detection of 19 and 23 IMC populations, respectively. Highly reproducible identification and enumeration of IMC populations was achieved, independently of anticoagulant, type of FCM instrument and center, particularly when database/software-guided automated (vs. manual “expert-based”) gating was used. Whereas no significant changes were observed in identification of IMC populations for up to 24h delayed sample processing, a significant impact was observed in their absolute counts after &gt;12h delay. Therefore, accurate identification and quantitation of IMC populations requires sample processing on the same day. Significantly different counts were observed in PB for multiple IMC populations according to age and sex. Consequently, PB samples from 116 healthy donors (8-69 years) were used for collecting age and sex related reference values for all IMC populations. In summary, the two antibody combinations and FCM approach allow for rapid, standardized, automated and reproducible identification of 19 and 23 IMC populations in PB, suited for monitoring of innate immune responses in clinical and translational research settings.

The antimicrobial peptide cathelicidin drives development of experimental autoimmune encephalomyelitis in mice by affecting Th17 differentiation

Multiple sclerosis (MS) is a highly prevalent demyelinating autoimmune condition; the mechanisms regulating its severity and progression are unclear. The IL-17-producing Th17 subset of T cells has been widely implicated in MS and in the mouse model, experimental autoimmune encephalomyelitis (EAE). However, the differentiation and regulation of Th17 cells during EAE remain incompletely understood. Although evidence is mounting that the antimicrobial peptide cathelicidin profoundly affects early T cell differentiation, no studies have looked at its role in longer-term T cell responses. Now, we report that cathelicidin drives severe EAE disease. It is released from neutrophils, microglia, and endothelial cells throughout disease; its interaction with T cells potentiates Th17 differentiation in lymph nodes and Th17 to exTh17 plasticity and IFN-γ production in the spinal cord. As a consequence, mice lacking cathelicidin are protected from severe EAE. In addition, we show that cathelicidin is produced by the same cell types in the active brain lesions in human MS disease. We propose that cathelicidin exposure results in highly activated, cytokine-producing T cells, which drive autoimmunity; this is a mechanism through which neutrophils amplify inflammation in the central nervous system.

Multidimensional overview of neurofilament light chain contribution to comprehensively understanding multiple sclerosis

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease characterized by demyelination, progressive axonal loss, and varying clinical presentations. Axonal damage associated with the inflammatory process causes neurofilaments, the major neuron structural proteins, to be released into the extracellular space, reaching the cerebrospinal fluid (CSF) and the peripheral blood. Methodological advances in neurofilaments’ serological detection and imaging technology, along with many clinical and therapeutic studies in the last years, have deepened our understanding of MS immunopathogenesis. This review examines the use of light chain neurofilaments (NFLs) as peripheral MS biomarkers in light of the current clinical and therapeutic evidence, MS immunopathology, and technological advances in diagnostic tools. It aims to highlight NFL multidimensional value as a reliable MS biomarker with a diagnostic-prognostic profile while improving our comprehension of inflammatory neurodegenerative processes, mainly RRMS, the most frequent clinical presentation of MS.

Alterations of blood monocyte subset distribution and surface phenotype are linked to infection severity in COVID-19 inpatients

Severe coronavirus disease 19 (COVID‐19) manifests with systemic immediate proinflammatory innate immune activation and altered iron turnover. Iron homeostasis, differentiation, and function of myeloid leukocytes are interconnected. Therefore, we characterized the cellularity, surface marker expression, and iron transporter phenotype of neutrophils and monocyte subsets in COVID‐19 patients within 72 h from hospital admission, and analyzed how these parameters relate to infection severity. Between March and November 2020, blood leukocyte samples from hospitalized COVID‐19 patients (n = 48) and healthy individuals (n = 7) were analyzed by flow cytometry enabling comparative analysis of 40 features. Inflammation‐driven neutrophil expansion, depletion of CD16⁺ nonclassical monocytes, and changes in surface expression of neutrophil and monocyte CD64 and CD86 were associated with COVID‐19 severity. By unsupervised self‐organizing map clustering, four patterns of innate myeloid response were identified and linked to varying levels of systemic inflammation, altered cellular iron trafficking and the severity of disease. These alterations of the myeloid leukocyte compartment during acute COVID‐19 may be hallmarks of inefficient viral control and immune hyperactivation and may help at risk prediction and treatment optimization.

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.

Serological markers exploration and real-world effectiveness and safety of teriflunomide in south Chinese patients with multiple sclerosis

BACKGROUND

Since September 2012, when teriflunomide was approved as a disease-modifying treatment for relapsing multiple sclerosis, real-world observational studies on teriflunomide in Chinese patients are limited.

METHODS

We collected demographic characteristics and peripheral blood samples at different time points. Clinical symptoms, magnetic resonance imaging data, and concentrations of neurofilament light chains and multiple cytokines at different time points were compared to assess the efficacy. Moreover, the safety was assessed by blood routine, liver and kidney function, and a questionnaire to report adverse reactions.

RESULTS

Teriflunomide significantly reduced serum levels of neurofilament light chains and several inflammatory cytokines. After accepting teriflunomide treatment, many clinical symptoms improved, scores of the expanded disability status scale decreased from 2.0 to 1.75, and annualized relapse rates decreased from 1.45 to 0.31. 29 (80.56%) and 15 (78.95%) patients achieved the no evidence of disease activity-3 status after 6 months and 12 months treatment, respectively. Teriflunomide was associated with mild or moderate discomfort, and discontinuation rates due to adverse events were low.

CONCLUSION

Serum neurofilament light chain protein is sensitive to teriflunomide treatment, suggesting that it has the potential to be used as an indicator to assess the efficacy of teriflunomide. Teriflunomide can significantly reduce the concentrations of inflammatory cytokines, indicating that teriflunomide may regulate neuroinflammation through the inhibitory effect on a variety of immune cells and their cytokines. Teriflunomide can improve clinical symptoms and disease severity in MS patients in southern China, and patients have good compliance.

Identifying disease-critical cell types and cellular processes across the human body by integration of single-cell profiles and human genetics

Genome-wide association studies (GWAS) provide a powerful means to identify loci and genes contributing to disease, but in many cases the related cell types/states through which genes confer disease risk remain unknown. Deciphering such relationships is important for identifying pathogenic processes and developing therapeutics. Here, we introduce sc-linker, a framework for integrating single-cell RNA-seq (scRNA-seq), epigenomic maps and GWAS summary statistics to infer the underlying cell types and processes by which genetic variants influence disease. We analyzed 1.6 million scRNA-seq profiles from 209 individuals spanning 11 tissue types and 6 disease conditions, and constructed gene programs capturing cell types, disease progression, and cellular processes both within and across cell types. We evaluated these gene programs for disease enrichment by transforming them to SNP annotations with tissue-specific epigenomic maps and computing enrichment scores across 60 diseases and complex traits (average N= 297K). Cell type, disease progression, and cellular process programs captured distinct heritability signals even within the same cell type, as we show in multiple complex diseases that affect the brain (Alzheimer’s disease, multiple sclerosis), colon (ulcerative colitis) and lung (asthma, idiopathic pulmonary fibrosis, severe COVID-19). The inferred disease enrichments recapitulated known biology and highlighted novel cell-disease relationships, including GABAergic neurons in major depressive disorder (MDD), a disease progression M cell program in ulcerative colitis, and a disease-specific complement cascade process in multiple sclerosis. In autoimmune disease, both healthy and disease progression immune cell type programs were associated, whereas for epithelial cells, disease progression programs were most prominent, perhaps suggesting a role in disease progression over initiation. Our framework provides a powerful approach for identifying the cell types and cellular processes by which genetic variants influence disease.

Monocytes in central nervous system remyelination

Remyelination failure with aging and progression of neurodegenerative disorders contributes to axonal dysfunction, highlighting the importance of understanding the mechanisms underpinning this process to develop regenerative therapies. Central nervous system (CNS) macrophages, encompassing both resident microglia and blood monocyte-derived cells, play a crucial role in driving successful remyelination. Although there has been a focus on the critical roles of microglia in remyelination, the specific contribution of monocyte-derived macrophages is still not fully understood. Until recently, the lack of tools enabling distinction between CNS macrophage populations has hindered our understanding of monocyte influence on remyelination. Recent advances have allowed for identification and characterization of monocyte populations in health, aging and in neurodegenerative conditions like multiple sclerosis, indicating heterogeneity of monocyte subsets impacted by both intrinsic and extrinsic factors. Here, we discuss the new tools enabling distinction between macrophage populations and advancements in understanding the importance of monocytes in remyelination, and reflect on the potential for therapeutic targeting of monocytes to promote remyelination.

Expansion of inflammatory monocytes in periphery and infiltrated into thyroid tissue in Graves' disease

Monocytes are important mediators of immune system and are reported to be altered in autoimmune disorders. Little is known about the pathological role of monocytes in Graves' disease (GD). Thus, we investigated monocytes in periphery and thyroid tissue in GD. Untreated GD patients were enrolled and followed up until remission. Monocytes were significantly increased and positively correlated with anti-thyrotropin receptor antibody (TRAb) in untreated GD (r_counts = 0.269, P < 0.001; r_percentage = 0.338, P < 0.001). Flow cytometry showed CD14++ CD16+ monocytes were increased and CD14++ CD16- monocytes were decreased in untreated GD (both P < 0.001). Skewed monocyte subsets were recovered in GD with remission. Serum B cell-activating factor (BAFF) was positively correlated with TRAb (r = 0.384 and P = 0.001). CD14++ CD16+ monocytes expressed higher level of BAFF in untreated GD (P < 0.05). The frequency of CD14+ monocytes and CD14+ CD16+ monocytes were significantly higher in GD thyroid tissue than in normal thyroid tissue (both P < 0.001). Our study suggested CD14++ CD16+ monocytes were significantly expanded and involved in the production of TRAb via secreting a higher level of BAFF in periphery. Besides, monocytes infiltrated into thyroid tissue and thus could serve as an important participant in GD pathogenesis.

Human Monocytes Plasticity in Neurodegeneration

Monocytes play a crucial role in immunity and tissue homeostasis. They constitute the first line of defense during the inflammatory process, playing a role in the pathogenesis and progression of diseases, making them an attractive therapeutic target. They are heterogeneous in morphology and surface marker expression, which suggest different molecular and physiological properties. Recent evidences have demonstrated their ability to enter the brain, and, as a consequence, their hypothetical role in different neurodegenerative diseases. In this review, we will discuss the current knowledge about the correlation between monocyte dysregulation in the brain and/or in the periphery and neurological diseases in humans. Here we will focus on the most common neurodegenerative disorders, such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and multiple sclerosis.

Extracellular vesicles (exosomes and ectosomes) play key roles in the pathology of brain diseases

Last century, neurons and glial cells were mostly believed to play distinct functions, relevant for the brain. Progressively, however, it became clear that neurons, astrocytes and microglia co-operate intensely with each other by release/binding of signaling factors, direct surface binding and generation/release of extracellular vesicles, the exosomes and ectosomes, called together vesicles in this abstract. The present review is focused on these vesicles, fundamental in various brain diseases. Their properties are extraordinary. The specificity of their membrane governs their fusion with distinct target cells, variable depending on the state and specificity of their cells of origin and target. Result of vesicle fusion is the discharge of their cargos into the cytoplasm of target cells. Cargos are composed of critical molecules, from proteins (various nature and function) to nucleotides (especially miRNAs), playing critical roles in immune and neurodegenerative diseases. Among immune diseases is multiple sclerosis, affected by extensive dysregulation of co-trafficking neural and glial vesicles, with distinct miRNAs inducing severe or reducing effects. The vesicle-dependent differences between progressive and relapsing-remitting forms of the disease are relevant for clinical developments. In Alzheimer’s disease the vesicles can affect the brain by changing their generation and inducing co-release of effective proteins, such Aβ and tau, from neurons and astrocytes. Specific miRNAs can delay the long-term development of the disease. Upon their traffic through the blood-brainbarrier, vesicles of various origin reach fluids where they are essential for the identification of biomarkers, important for diagnostic and therapeutic innovations, critical for the future of many brain patients.

Disorders of the enteric nervous system - a holistic view

The enteric nervous system (ENS) is the largest division of the peripheral nervous system and closely resembles components and functions of the central nervous system. Although the central role of the ENS in congenital enteric neuropathic disorders, including Hirschsprung disease and inflammatory and functional bowel diseases, is well acknowledged, its role in systemic diseases is less understood. Evidence of a disordered ENS has accumulated in neurodegenerative diseases ranging from amyotrophic lateral sclerosis, Alzheimer disease and multiple sclerosis to Parkinson disease as well as neurodevelopmental disorders such as autism. The ENS is a key modulator of gut barrier function and a regulator of enteric homeostasis. A 'leaky gut' represents the gateway for bacterial and toxin translocation that might initiate downstream processes. Data indicate that changes in the gut microbiome acting in concert with the individual genetic background can modify the ENS, central nervous system and the immune system, impair barrier function, and contribute to various disorders such as irritable bowel syndrome, inflammatory bowel disease or neurodegeneration. Here, we summarize the current knowledge on the role of the ENS in gastrointestinal and systemic diseases, highlighting its interaction with various key players involved in shaping the phenotypes. Finally, current flaws and pitfalls related to ENS research in addition to future perspectives are also addressed.

Inflammation in multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS) that is characterised pathologically by demyelination, gliosis, neuro-axonal damage and inflammation. Despite intense research, the underlying pathomechanisms driving inflammatory demyelination in MS still remain incompletely understood. It is thought to be caused by an autoimmune response towards CNS self-antigens in genetically susceptible individuals, assuming autoreactive T cells as disease-initiating immune cells. Yet, B cells were recognized as crucial immune cells in disease pathology, including antibody-dependent and independent effects. Moreover, myeloid cells are important contributors to MS pathology, and it is becoming increasingly evident that different cell types act in concert during MS immunopathology. This is supported by the finding that the beneficial effects of actual existing disease-modifying therapies cannot be attributed to one single immune cell-type, but rather involve immunological cooperation. The current strategy of MS therapies thus aims to shift the immune cell repertoire from a pro-inflammatory towards an anti-inflammatory phenotype, involving regulatory T and B cells and anti-inflammatory macrophages. Although no existing therapy actually exists that directly induces an enhanced regulatory immune cell pool, numerous studies identified potential net effects on these cell types. This review gives a conceptual overview on T cells, B cells and myeloid cells in the immunopathology of relapsing-remitting MS and discusses potential contributions of actual disease-modifying therapies on these immune cell phenotypes.

Dwellers and Trespassers: Mononuclear Phagocytes at the Borders of the Central Nervous System

The central nervous system (CNS) parenchyma is enclosed and protected by a multilayered system of cellular and acellular barriers, functionally separating glia and neurons from peripheral circulation and blood-borne immune cells. Populating these borders as dynamic observers, CNS-resident macrophages contribute to organ homeostasis. Upon autoimmune, traumatic or neurodegenerative inflammation, these phagocytes start playing additional roles as immune regulators contributing to disease evolution. At the same time, pathological CNS conditions drive the migration and recruitment of blood-borne monocyte-derived cells across distinct local gateways. This invasion process drastically increases border complexity and can lead to parenchymal infiltration of blood-borne phagocytes playing a direct role both in damage and in tissue repair. While recent studies and technical advancements have highlighted the extreme heterogeneity of these resident and CNS-invading cells, both the compartment-specific mechanism of invasion and the functional specification of intruding and resident cells remain unclear. This review illustrates the complexity of mononuclear phagocytes at CNS interfaces, indicating how further studies of CNS border dynamics are crucially needed to shed light on local and systemic regulation of CNS functions and dysfunctions.

Common Peripheral Immunity Mechanisms in Multiple Sclerosis and Alzheimer's Disease

Neurodegenerative diseases are closely related to inflammatory and autoimmune events, suggesting that the dysregulation of the immune system is a key pathological factor. Both multiple sclerosis (MS) and Alzheimer's disease (AD) are characterized by infiltrating immune cells, activated microglia, astrocyte proliferation, and neuronal damage. Moreover, MS and AD share a common pro-inflammatory signature, characterized by peripheral leukocyte activation and transmigration to the central nervous system (CNS). MS and AD are both characterized by the accumulation of activated neutrophils in the blood, leading to progressive impairment of the blood–brain barrier. Having migrated to the CNS during the early phases of MS and AD, neutrophils promote local inflammation that contributes to pathogenesis and clinical progression. The role of circulating T cells in MS is well-established, whereas the contribution of adaptive immunity to AD pathogenesis and progression is a more recent discovery. Even so, blocking the transmigration of T cells to the CNS can benefit both MS and AD patients, suggesting that common adaptive immunity mechanisms play a detrimental role in each disease. There is also growing evidence that regulatory T cells are beneficial during the initial stages of MS and AD, supporting the link between the modulatory immune compartments and these neurodegenerative disorders. The number of resting regulatory T cells declines in both diseases, indicating a common pathogenic mechanism involving the dysregulation of these cells, although their precise role in the control of neuroinflammation remains unclear. The modulation of leukocyte functions can benefit MS patients, so more insight into the role of peripheral immune cells may reveal new targets for pharmacological intervention in other neuroinflammatory and neurodegenerative diseases, including AD.

Nonclassical monocytes in cardiovascular physiology and disease

Monocytes are a heterogeneous cell population of innate immune cells with distinct cell surface markers that help them in carrying out different functions. In humans, there are three well-characterized subsets, namely, classical (CD14⁺⁺CD16^-), intermediate (CD14⁺⁺CD16⁺), and nonclassical (CD14⁺ CD16⁺⁺) monocytes. There is an emerging focus on the not yet well explored nonclassical monocytes that maintain vascular integrity by slowly patrolling on the endothelium, reacting to inflammatory signals, and clearing cell debris. In this manner, they are not only crucial for vascular homeostasis but also play a vital role in wound healing and resolution of inflammation by linking innate to adaptive immune response. Although they have been shown to be protective, yet they are also associated with inflammatory disease progression. This short review will give an insight about the emerging role of nonclassical monocytes in vascular homeostasis, inflammation, and protection in the context of cardiovascular disease.

Neutrophils: Underestimated Players in the Pathogenesis of Multiple Sclerosis (MS)

Neutrophils are the most abundant circulating and first-responding innate myeloid cells and have so far been underestimated in the context of multiple sclerosis (MS). MS is the most frequent, immune-mediated, inflammatory disease of the central nervous system. MS is treatable but not curable and its cause(s) and pathogenesis remain elusive. The involvement of neutrophils in MS pathogenesis has been suggested by the use of preclinical animal disease models, as well as on the basis of patient sample analysis. In this review, we provide an overview of the possible mechanisms and functions by which neutrophils may contribute to the development and pathology of MS. Neutrophils display a broad variety of effector functions enabling disease pathogenesis, including (1) the release of inflammatory mediators and enzymes, such as interleukin-1β, myeloperoxidase and various proteinases, (2) destruction and phagocytosis of myelin (as debris), (3) release of neutrophil extracellular traps, (4) production of reactive oxygen species, (5) breakdown of the blood-brain barrier and (6) generation and presentation of autoantigens. An important question relates to the issue of whether neutrophils exhibit a predominantly proinflammatory function or are also implicated in the resolution of chronic inflammatory responses in MS.