Unaltered regulatory B-cell frequency and function in patients with multiple sclerosis

Intruders or protectors - the multifaceted role of B cells in CNS disorders

B lymphocytes are immune cells studied predominantly in the context of peripheral humoral immune responses against pathogens. Evidence has been accumulating in recent years on the diversity of immunomodulatory functions that B cells undertake, with particular relevance for pathologies of the central nervous system (CNS). This review summarizes current knowledge on B cell populations, localization, infiltration mechanisms, and function in the CNS and associated tissues. Acute and chronic neurodegenerative pathologies are examined in order to explore the complex, and sometimes conflicting, effects that B cells can have in each context, with implications for disease progression and treatment outcomes. Additional factors such as aging modulate the proportions and function of B cell subpopulations over time and are also discussed in the context of neuroinflammatory response and disease susceptibility. A better understanding of the multifactorial role of B cell populations in the CNS may ultimately lead to innovative therapeutic strategies for a variety of neurological conditions.

Therapeutic targeting of gut-originating regulatory B cells in neuroinflammatory diseases

Regulatory B cells (Bregs) are immunosuppressive cells that support immunological tolerance by the production of IL-10, IL-35, and TGF-β. Bregs arise from different developmental stages in response to inflammatory stimuli. In that regard, mounting evidence points towards a direct influence of gut microbiota on mucosal B cell development, activation, and regulation in health and disease. While an increasing number of diseases are associated with alterations in gut microbiome (dysbiosis), little is known about the role of microbiota on Breg development and induction in neuroinflammatory disorders. Notably, gut-originating, IL-10- and IgA-producing regulatory plasma cells have recently been demonstrated to egress from the gut to suppress inflammation in the CNS raising fundamental questions about the triggers and functions of mucosal-originating Bregs in systemic inflammation. Advancing our understanding of Bregs in neuroinflammatory diseases could lead to novel therapeutic approaches. Here, we summarize the main aspects of Breg differentiation and functions and evidence about their involvement in neuroinflammatory diseases. Further, we highlight current data of gut-originating Bregs and their microbial interactions and discuss future microbiota-regulatory B cell-targeted therapies in immune-mediated diseases.

Ocrevus reduces TH40 cells, a biomarker of systemic inflammation, in relapsing multiple sclerosis (RMS) and in progressive multiple sclerosis (PMS)

Treating MS has been difficult. One successful drug is Ocrelizumab (anti-CD20), used for the chronic relapsing MS (RMS) and the progressive MS (PMS) forms. TH40 cells are pathogenic effector T cells that increase in percentage and numbers during chronic inflammation. Here we show that in the earliest MS course, clinically isolated syndrome (CIS), TH40 cells expand in number. In PMS TH40 cell numbers remain expanded demonstrating sustained chronic inflammation. In RMS TH40 cells were found in CSF and express CD20. Ocrelizumab reduced TH40 cells to healthy control levels in patients. During treatment inflammatory cytokine producing TH40 cells were decreased.

Deconvolution of B cell receptor repertoire in multiple sclerosis patients revealed a delay in tBreg maturation

Background

B lymphocytes play a pivotal regulatory role in the development of the immune response. It was previously shown that deficiency in B regulatory cells (Bregs) or a decrease in their anti-inflammatory activity can lead to immunological dysfunctions. However, the exact mechanisms of Bregs development and functioning are only partially resolved. For instance, only a little is known about the structure of their B cell receptor (BCR) repertoires in autoimmune disorders, including multiple sclerosis (MS), a severe neuroinflammatory disease with a yet unknown etiology. Here, we elucidate specific properties of B regulatory cells in MS.

Methods

We performed a prospective study of the transitional Breg (tBreg) subpopulations with the CD19+CD24highCD38high phenotype from MS patients and healthy donors by (i) measuring their content during two diverging courses of relapsing-remitting MS: benign multiple sclerosis (BMS) and highly active multiple sclerosis (HAMS); (ii) analyzing BCR repertoires of circulating B cells by high-throughput sequencing; and (iii) measuring the percentage of CD27+ cells in tBregs.

Results

The tBregs from HAMS patients carry the heavy chain with a lower amount of hypermutations than tBregs from healthy donors. The percentage of transitional CD24highCD38high B cells is elevated, whereas the frequency of differentiated CD27+ cells in this transitional B cell subset was decreased in the MS patients as compared with healthy donors.

Conclusions

Impaired maturation of regulatory B cells is associated with MS progression.

Evolution of Anti-B Cell Therapeutics in Autoimmune Neurological Diseases

B cells have an ever-increasing role in the etiopathology of a number of autoimmune neurological disorders, acting as antigen-presenting cells facilitating antibody production but also as sensors, coordinators, and regulators of the immune response. In particular, B cells can regulate the T cell activation process through their participation in antigen presentation, production of proinflammatory cytokines (bystander activation or suppression), and contribution to ectopic lymphoid aggregates. Such an important interplay between B and T cells makes therapeutic depletion of B cells an attractive treatment strategy. The last decade, anti-B cell therapies using monoclonal antibodies against B cell surface molecules have evolved into a rational approach for successfully treating autoimmune neurological disorders, even when T cells seem to be the main effector cells. The paper summarizes basic aspects of B cell biology, discusses the roles of B cells in neurological autoimmunities, and highlights how the currently available or under development anti-B cell therapeutics exert their action in the wide spectrum and immunologically diverse neurological disorders. The efficacy of the various anti-B cell therapies and practical issues on induction and maintenance therapy is specifically detailed for the treatment of patients with multiple sclerosis, neuromyelitis-spectrum disorders, autoimmune encephalitis and hyperexcitability CNS disorders, autoimmune neuropathies, myasthenia gravis, and inflammatory myopathies. The success of anti-B cell therapies in inducing long-term remission in IgG4 neuroautoimmunities is also highlighted pointing out potential biomarkers for follow-up infusions.

Regulatory Cells in Multiple Sclerosis: From Blood to Brain

Multiple sclerosis (MS) is a chronic, autoimmune, and neurodegenerative disease of the central nervous system (CNS) that affects myelin. The etiology of MS is unclear, although a variety of environmental and genetic factors are thought to increase the risk of developing the disease. Historically, T cells were considered to be the orchestrators of MS pathogenesis, but evidence has since accumulated implicating B lymphocytes and innate immune cells in the inflammation, demyelination, and axonal damage associated with MS disease progression. However, more recently the importance of the protective role of immunoregulatory cells in MS has become increasingly evident, such as that of myeloid-derived suppressor cells (MDSCs), regulatory T (Treg) and B (Breg) cells, or CD56bright natural killer cells. In this review, we will focus on how peripheral regulatory cells implicated in innate and adaptive immune responses are involved in the physiopathology of MS. Moreover, we will discuss how these cells are thought to act and contribute to MS histopathology, also addressing their promising role as promoters of successful remyelination within the CNS. Finally, we will analyze how understanding these protective mechanisms may be crucial in the search for potential therapies for MS.

Regulatory B cells, A to Z

B cells play a central role in the immune system through the production of antibodies. During the past two decades, it has become increasingly clear that B cells also have the capacity to regulate immune responses through mechanisms that extend beyond antibody production. Several types of human and murine regulatory B cells have been reported that suppress inflammatory responses in autoimmune disease, allergy, infection, transplantation, and cancer. Key suppressive molecules associated with regulatory B-cell function include the cytokines IL-10, IL-35, and TGF-β as well as cell membrane-bound molecules such as programmed death-ligand 1, CD39, CD73, and aryl hydrocarbon receptor. Regulatory B cells can be induced by a range of different stimuli, including microbial products such as TLR4 or TLR9 ligands, inflammatory cytokines such as IL-6, IL-1β, and IFN-α, as well as CD40 ligation. This review provides an overview of our current knowledge on regulatory B cells. We discuss different types of regulatory B cells, the mechanisms through which they exert their regulatory functions, factors that lead to induction of regulatory B cells and their role in the alteration of inflammatory responses in different diseases.

Mass Cytometry Identifies Expansion of T-bet+ B Cells and CD206+ Monocytes in Early Multiple Sclerosis

Multiple sclerosis (MS) is an immune-driven demyelinating disease of the central nervous system. Immune cell features are particularly promising as predictive biomarkers due to their central role in the pathogenesis but also as drug targets, even if nowadays, they have no impact in clinical practice. Recently, high-resolution approaches, such as mass cytometry (CyTOF), helped to better understand the diversity and functions of the immune system. In this study, we performed an exploratory analysis of blood immune response profiles in healthy controls and MS patients sampled at their first neurological relapse, using two large CyTOF panels including 62 markers exploring myeloid and lymphoid cells. An increased abundance of both a T-bet-expressing B cell subset and a CD206⁺ classical monocyte subset was detected in the blood of early MS patients. Moreover, T-bet-expressing B cells tended to be enriched in aggressive MS patients. This study provides new insights into understanding the pathophysiology of MS and the identification of immunological biomarkers. Further studies will be required to validate these results and to determine the exact role of the identified clusters in neuroinflammation.

The identification, development and therapeutic potential of IL-10-producing regulatory B cells in multiple sclerosis

Regulatory B cells are a rare B-cell subset widely known to exert their immunosuppressive function via the production of interleukin-10 (IL-10) and other mechanisms. B10 cells are a special subset of regulatory B cells with immunoregulatory function that is fully attributed to IL-10. Their unique roles in the animal model of multiple sclerosis (MS) have been described, as well as their relevance in MS patients. This review specifically focuses on the identification and development of B10 cells, the signals that promote IL-10 production in B cells, the roles of B10 cells in MS, and the potential and major challenges of the application of B10-based therapies for MS.

Activated leukocyte cell adhesion molecule regulates B lymphocyte migration across central nervous system barriers

The presence of B lymphocyte-associated oligoclonal immunoglobulins in the cerebrospinal fluid is a classic hallmark of multiple sclerosis (MS). The clinical efficacy of anti-CD20 therapies supports a major role for B lymphocytes in MS development. Although activated oligoclonal populations of pathogenic B lymphocytes are able to traffic between the peripheral circulation and the central nervous system (CNS) in patients with MS, molecular players involved in this migration have not yet been elucidated. In this study, we demonstrated that activated leukocyte cell adhesion molecule (ALCAM/CD166) identifies subsets of proinflammatory B lymphocytes and drives their transmigration across different CNS barriers in mouse and human. We also showcased that blocking ALCAM alleviated disease severity in animals affected by a B cell-dependent form of experimental autoimmune encephalomyelitis. Last, we determined that the proportion of ALCAM⁺ B lymphocytes was increased in the peripheral blood and within brain lesions of patients with MS. Our findings indicate that restricting access to the CNS by targeting ALCAM on pathogenic B lymphocytes might represent a promising strategy for the development of next-generation B lymphocyte-targeting therapies for the treatment of MS.

The proportion of myeloid-derived suppressor cells in the spleen is related to the severity of the clinical course and tissue damage extent in a murine model of multiple sclerosis

Multiple Sclerosis (MS) is the second cause of paraplegia among young adults, after all types of CNS traumatic lesions. In its most frequent relapsing-remitting form, the severity of the disease course is very heterogeneous, and its reliable evaluation remains a key issue for clinicians. Myeloid-Derived sSuppressor Cells (MDSCs) are immature myeloid cells that suppress the inflammatory response, a phenomenon related to the resolution or recovery of the clinical symptoms associated with experimental autoimmune encephalomyelitis (EAE), the most common model for MS. Here, we establish the severity index as a new parameter for the clinical assessment in EAE. It is derived from the relationship between the maximal clinical score and the time elapsed since disease onset. Moreover, we relate this new index with several histopathological hallmarks in EAE and with the peripheral content of MDSCs. Based on this new parameter, we show that the splenic MDSC content is related to the evolution of the clinical course of EAE, ranging from mild to severe. Indeed, when the severity index indicates a severe disease course, EAE mice display more intense lymphocyte infiltration, demyelination and axonal damage. A direct correlation was drawn between the MDSC population in the peripheral immune system, and the preservation of myelin and axons, which was also correlated with T cell apoptosis within the CNS (being these cells the main target for MDSC suppression). The data presented clearly indicated that the severity index is a suitable tool to analyze disease severity in EAE. Moreover, our data suggest a clear relationship between circulating MDSC enrichment and disease outcome, opening new perspectives for the future targeting of this population as an indicator of MS severity.

The role of B regulatory (B10) cells in inflammatory disorders and their potential as therapeutic targets

Over the past decade, studies have identified subset of B cells, which play suppressive functions in additions to the conventional functions of B cells: antigen processing and presentation, activation of T cells and antibody productions. Because of their regulatory function, they were named as B regulatory cells (Bregs). Bregs restrict the severity of autoimmune disorders in animal disease models such as experimental autoimmune myocarditis (EAM), experimental autoimmune encephalitis (EAE), and collagen-induced arthritis (CIA) but can contribute to the development of infection and cancer. In humans, the roles of B regulatory cells in autoimmune diseases have not been clearly established because of the inconsistent findings from many researchers. This is believed to arise from the speculated fact that Bregs lack specific marker, which can be used to identify and characterize them in human diseases. The CD19⁺CD24^hiCD38^hiCD1d^hiB cells have been associated with the regulatory function. Available evidences highlight the relevance of increasing IL-10-producing B cells in autoimmune diseases and the possibility of serving as new therapeutic targets in inflammatory disorders. This review empanels the functions of Bregs in autoimmune diseases in both human and animal models, and further evaluates the possibility of Bregs as therapeutic targets in inflammatory disorders. Consequently, this might help identify possible research gaps, which need to be clarified as researchers speculate the possibility of targeting some subsets of Bregs in the treatment of inflammatory disorders.

Resolution of inflammation during multiple sclerosis

Multiple sclerosis (MS) is a frequent autoimmune demyelinating disease of the central nervous system (CNS). There are three clinical forms described: relapsing-remitting multiple sclerosis (RRMS), the most common initial presentation (85%) among which, if not treated, about half will transform, into the secondary progressive multiple sclerosis (SPMS) and the primary progressive MS (PPMS) (15%) that is directly progressive without superimposed clinical relapses. Inflammation is present in all subsets of MS. The relapsing/remitting form could represent itself a particular interest for the study of inflammation resolution even though it remains incomplete in MS. Successful resolution of acute inflammation is a highly regulated process and dependent on mechanisms engaged early in the inflammatory response that are scarcely studied in MS. Moreover, recent classes of disease-modifying treatment (DMTs) that are effective against RRMS act by re-establishing the inflammatory imbalance, taking advantage of the pre-existing endogenous suppressor. In this review, we will discuss the active role of regulatory immune cells in inflammation resolution as well as the role of tissue and non-hematopoietic cells as contributors to inflammation resolution. Finally, we will explore how DMTs, more specifically induction therapies, impact the resolution of inflammation during MS.

Role of Regulatory Immune Cells and Molecules in Autoimmune Bullous Dermatoses

Autoimmune bullous dermatoses (AIBD) include a series of typical organ-specific autoimmune diseases characterized by extensive mucocutaneous blisters. It is generally accepted to be caused by pathological autoantibodies that directly target specific adhesion components of the skin or the adjacent mucous membranes. Both innate and adaptive immune systems are critically involved in the misguided immune response against self-antigens. Recent studies have indicated that the dysfunction of regulatory T cells, regulatory B cells, and complement regulatory proteins that play essential roles in maintaining a healthy immune environment is also closely related to immune disorders in AIBD. It is important to summarize these studies, elucidate the changes in these regulatory immune cells and molecules for the pathogenesis of AIBD, and reveal the mechanisms by which they lose their ability to regulate immune disorders. In this review, we highlight the role of regulatory immune cells and molecules in the pathogenesis of pemphigus vulgaris and bullous pemphigoid, the two most representative forms of AIBD, and indicate issues that should be addressed in future investigations.

Thymosins in multiple sclerosis and its experimental models: moving from basic to clinical application

BACKGROUND

Multiple sclerosis (MS) afflicts more than 2.5 million individuals worldwide and this number is increasing over time. Within the past years, a great number of disease-modifying treatments have emerged; however, efficacious treatments and a cure for MS await discovery. Thymosins, soluble hormone-like peptides produced by the thymus gland, can mediate immune and non-immune physiological processes and have gained interest in recent years as therapeutics in inflammatory and autoimmune diseases.

METHODS

Pubmed was searched with no time constraints for articles using a combination of the keywords "thymosin/s" or "thymus factor/s" AND "multiple sclerosis", mesh terms with no language restriction.

RESULTS

Here, we review the state-of-the-art on the effects of thymosins on MS and its experimental models. In particular, we describe what is known in this field on the roles of thymosin-α1 (Tα1) and -β4 (Tβ4) as potential anti-inflammatory as well as neuroprotective and remyelinating molecules and their mechanisms of action.

CONCLUSION

Based on the data that Tα1 and Tβ4 act as anti-inflammatory molecules and as inducers of myelin repair and neuronal protection, respectively, a possible therapeutic application in MS for Tα1 and Tβ4 alone or combined with other approved drugs may be envisaged. This approach is reasonable in light of the current clinical usage of Tα1 and data demonstrating the safety, tolerability and efficacy of Tβ4 in clinical practice.

Frequency and immunophenotype of IL10-producing regulatory B cells in optic neuritis

Mouse models of multiple sclerosis (MS) have shown the importance of interleukin-10 (IL-10) -producing regulatory B (Breg) cells in dampening disease activity and inhibiting disease initiation and progression. In MS and other autoimmune diseases decreased frequency and functionality of Breg cells correlate with disease activity and the percentage of IL-10-producing Breg cells decreases during relapse and normalizes in remission. Optic neuritis (ON) is a common first clinical manifestation of MS and IL-10-producing Breg cells may be crucial in the transition from ON to MS, we therefore investigate the frequency and function of Breg cells in ON as a clinical model of early demyelinating disease. B cells were purified from 27 patients with ON sampled close to symptom onset (median 23 days, range 7-41 days) and 13 healthy controls. The B cells were stimulated and cultured for 48 hr with CD40 ligand and CpG before measurement of intracellular IL-10 and the surface markers CD19, CD1d, CD5, CD24, CD38 and CD27 by flow cytometry. The frequency of B-cell subsets was analysed in peripheral blood and cerebral spinal fluid (CSF) of patients. Sixty-five per cent of the IL-10-producing Breg cells co-expressed CD24 and CD38, and only 14% were CD24^high  CD27⁺ , suggesting that the naive B cells are the primary source of IL-10 in the B-cell culture, followed by memory cells in both healthy controls and patients. The frequency of naive CD19⁺  CD24⁺  CD38⁺ Breg cells was higher in patients with ON compared with controls. The ability of Breg cells to produce IL-10 was at normal levels in both ON patients with high risk and those with low risk of progression to MS. We found no correlation between Breg cell function and the presence of brain white matter lesions by magnetic resonance imaging or CSF oligoclonal bands indicative of ON patients carrying a higher risk of conversion to MS. The frequencies of IL-10-producing B cells did not correlate with the conversion to MS at 2-year follow up. Interleukin-10 was primarily produced by naive and memory B cells. The frequency of IL-10-secreting B cells did not correlate with risk factors of MS. Breg cell function at clinical onset of ON is not a determining factor for conversion to MS.

Central Nervous System Involvement in Common Variable Immunodeficiency: A Case of Acute Unilateral Optic Neuritis in a 26-Year-Old Italian Patient

Common Variable Immunodeficiency (CVID) is a group of heterogeneous primary immunodeficiencies sharing defective B lymphocytes maturation and dysregulated immune response and resulting in impaired immunoglobulin production. Clinical picture encompasses increased susceptibility to infections, hematologic malignancies, inflammatory, and autoimmune diseases. Neurological manifestations are uncommon and optic neuritis has been previously reported only in one case with bilateral involvement. We hereby report a case of a 26-year-old man affected by CVID undergoing regular immunoglobulin supplementation, who presented with acute unilateral demyelinating optic neuritis and lymphocytic pleocytosis in the cerebrospinal fluid. A variety of infectious, inflammatory, and neoplastic conditions were excluded and a diagnosis of clinically isolated optic neuritis was made. The patient was treated with a short course of intravenous steroids with complete recovery. Overall, this case expands our current knowledge about clinical spectrum of complications in CVID and highlights the need for further research about this complex disease.

Regulatory B and T lymphocytes in multiple sclerosis: friends or foes?

Current clinical experience with immunomodulatory agents and monoclonal antibodies in principle has established the benefit of depleting lymphocytic populations in relapsing–remitting multiple sclerosis (RRMS). B and T cells may exert multiple pro-inflammatory actions, but also possess regulatory functions making their role in RRMS pathogenesis much more complex. There is no clear correlation of Tregs and Bregs with clinical features of the disease. Herein, we discuss the emerging data on regulatory T and B cell subset distributions in MS and their roles in the pathophysiology of MS and its murine model, experimental autoimmune encephalomyelitis (EAE). In addition, we summarize the immunomodulatory properties of certain MS therapeutic agents through their effect on such regulatory cell subsets and their relevance to clinical outcomes.

B lymphocytes: Crucial contributors to brain development and neurological diseases

The immune system is a major contributor to brain homeostasis and pathogenesis of neurological diseases. However, the role of B lymphocytes (cells) in the brain is poorly understood. In this review, we describe the functions of the different subtypes of B cells in brain development and neurological diseases. B cells are classified into several subtypes according their function and gene expression. B-1a cells, which participate in innate immunity by producing natural antibodies, are abundant in the developing brain, and mediate oligodendrocyte development. In conditions such as autoimmune encephalomyelitis, spinal cord injury, and stroke, B-2 cells exacerbate the pathology by producing pathogenic autoantibodies. On the other hand, regulatory B cells suppress inflammation by secreting interleukin-10 and play beneficial roles in pathological conditions. Here, we summarize the distribution and function of B cells during brain development and neurological diseases.

The IL-10-producing regulatory B cells (B10 cells) and regulatory T cell subsets in neuromyelitis optica spectrum disorder

B cells contribute to the pathogenesis of neuromyelitis optica (NMO) by producing Aquaporin 4-specific autoantibodies (AQP4-ab); on the other hand, there are certain B cells that suppress immune responses by producing regulatory cytokines, such as IL-10. In this study, we investigated the presence of IL-10-producing Breg cells among lymphocyte subsets. Twenty-two seropositive NMO spectrum disorder (NMOSD) patients (29 samples) and 13 healthy controls (HCs) (14 samples) were enrolled. All NMOSD patients have received one or more immunosuppressive drugs. The phenotype and frequency of B cell and T cell subsets in the peripheral blood were measured by flow cytometry. We defined Breg cells as IL-10-producing B (B10) cells, which are CD19⁺CD39⁺CD1d⁺IL-10⁺. The potential relations were evaluated between specific lymphocyte subsets and AQP4-ab intensity measured by the cell-based indirect immunofluorescence assay. The frequency of B10 cells was higher in patients with NMOSD regardless of the disease status than that in HCs (attack samples; p = 0.009 and remission samples; p < 0.001, respectively). In addition, the frequency of IL-17⁺ Treg cells among Treg cells was higher during remission than during an attack (uncorrected p = 0.032). Among the lymphocyte subsets, B10 cells alone showed a positive correlation with the intensity of AQP4-ab positivity (ρ [rho] = 0.402 and p = 0.031). It was suggested that the suppressive subsets including B10 and IL-17⁺ Treg cells might have important roles in controlling disease status in NMOSD. Further functional studies may help to elucidate the immunological role of B10 and IL-17⁺ Treg cells in NMOSD.

Proinflammatory B-cell profile in the early phases of MS predicts an active disease

Objective:

To assess whether any alteration of B-cell subset distribution and/or the cytokine production capacities of B cells could be associated with any stage of MS and could be predictive of MS evolution.

Methods:

We prospectively enrolled radiologically isolated syndrome (RIS), clinically isolated syndrome (CIS), naive patients with relapsing remitting MS (RRMS) of any disease modifying drug, and healthy controls (HCs). Peripheral blood B-cell subset distributions and the interleukin (IL)-6/IL-10–producing B-cell ratio were assessed by flow cytometry to evaluate their proinflammatory and anti-inflammatory functional properties.

Results:

Twelve RIS, 46 CIS, 31 RRMS patients, and 36 HCs were enrolled. We observed that a high IL-6/IL-10–producing B-cell ratio in patients with RIS/CIS was associated with the evolution of the disease in the short term (6 months). This imbalance in cytokine production was mainly explained by an alteration of the production of IL-10 by B cells, especially for the transitional B-cell subset. In addition, a significant increase in IgD⁻/CD27⁻ B cells was detected in patients with CIS and RRMS compared with HCs (p = 0.01). Apart from this increase in exhausted B cells, no other variation in B-cell subsets was observed.

Conclusions:

The association between a high IL-6/IL-10–producing B-cell ratio and the evolution of patients with RIS/CIS suggest a skew of B cells toward proinflammatory properties that might be implicated in the early phases of MS disease.

The CD40-CD40L Dyad in Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis

The CD40-CD40L dyad is an immune checkpoint regulator that promotes both innate and adaptive immune responses and has therefore an essential role in the development of inflammatory diseases, including multiple sclerosis (MS). In MS, CD40 and CD40L are expressed on immune cells present in blood and lymphoid organs, affected resident central nervous system (CNS) cells, and inflammatory cells that have infiltrated the CNS. CD40-CD40L interactions fuel the inflammatory response underlying MS, and both genetic deficiency and antibody-mediated inhibition of the CD40-CD40L dyad reduce disease severity in experimental autoimmune encephalomyelitis (EAE). Both proteins are therefore attractive therapeutic candidates to modulate aberrant inflammatory responses in MS. Here, we discuss the genetic, experimental and clinical studies on the role of CD40 and CD40L interactions in EAE and MS and we explore novel approaches to therapeutically target this dyad to combat neuroinflammatory diseases.

Circulating regulatory B cell subsets in patients with neuromyelitis optica spectrum disorders

This study analyzed the populations of three different subsets of regulatory B cells (Bregs) in the peripheral blood mononuclear cells (PBMCs) of patients with neuromyelitis optica spectrum disorders (NMOSDs) and explored the relationship between the changes in these subsets of Bregs and the severity of NMOSD. A total of 22 patients with relapsed NMOSDs before treatment were recruited in our study, along with 20 age and gender-matched healthy controls, from May 2015 to March 2016. The percentages and numbers for three different subsets of Bregs including the CD19+CD24hiCD38hi, CD19+CD24hiCD27+, and CD19+CD5+CD1dhi populations were evaluated in parallel by flow cytometry. Afterwards, correlations between the change of three different subsets of Bregs and disease severity were analyzed. We found significantly lower percentages of CD19+CD24hiCD38hi and CD19+CD5+CD1dhi Bregs in NMOSDs patients than in healthy individuals. In contrast, the CD19+CD24hiCD27+ Bregs population was significantly higher in NMOSDs patients than in healthy individuals. However, the three different Bregs subsets showed no significant correlation with expanded disability status scale (EDSS) or annualized relapse rate (ARR). Our findings suggest that the subsets of Bregs may play complex roles in the pathogenesis of NMOSDs and are not correlated with clinical disease severity. Further insights into the potential role of subsets of Bregs could increase our basic knowledge of NMOSDs pathogenesis.

Altered regulatory T-cell fractions and Helios expression in clinically isolated syndrome: clues to the development of multiple sclerosis

Development of multiple sclerosis (MS) is frequently preceded by an acute or subacute neurological disturbance referred to as clinically isolated syndrome (CIS). The specific immunological disturbances present in CIS remain underexamined. This study analysed peripheral blood mononuclear cells from n=18 treatment-naive individuals with recently diagnosed CIS (<120 days) for disturbances in the phenotype of T regulatory (Treg), follicular T regulatory (Tfr), T helper (Th), follicular T helper (Tfh) and B cells. Relative to healthy controls (n=19), CIS was associated with lower proportions of suppressive CD45RA⁺FoxP3^lo Treg and Tfr cells and greater proportions of non-suppressive CD45RA⁻FoxP3^lo and Th17-like Treg and Tfr. Lower Helios expression (maen fluorescent intensity) was measured across all Treg and Tfr fractions in the CIS group, suggesting less potent regulatory function. Greater frequencies of activated, efficient B-cell helper Tfh subsets and a trend for a higher proportion of IgD⁻CD27⁻ B cells was also detected in the CIS group, characteristics that were positively correlated with Treg and Tfr Helios expression. These results indicate that Treg and Tfr impairment is an early feature in MS.

Effector and regulatory B cells in Multiple Sclerosis

The role of B cells in the pathogenesis of Multiple Sclerosis (MS), an autoimmune neurodegenerative disease, is becoming eminent in recent years, but the specific contribution of the distinct B cell subsets remains to be elucidated. Several B cell subsets have shown regulatory, anti-inflammatory capacities in response to stimuli in vitro, as well as in the animal model of MS: Experimental Autoimmune Encephalomyelitis (EAE). However, the functional role of the B regulatory cells (Bregs) in vivo and specifically in the human disease is yet to be clarified. In the present review, we have summarized the updated information on the roles of effector and regulatory B cells in MS and the immune-modulatory effects of MS therapeutic agents on their phenotype and function.

Thymosin-α1 expands deficient IL-10-producing regulatory B cell subsets in relapsing–remitting multiple sclerosis patients

Background:

B cells are key pathogenic effectors in multiple sclerosis (MS) and several therapies have been designed to restrain B cell abnormalities by directly targeting this lymphocyte population.

Objectives:

Moving from our data showing a Toll-like receptor (TLR)7-driven dysregulation of B cell response in relapsing–remitting multiple sclerosis (RRMS) and having found a low serum level of Thymosin-α1 (Tα1) in patients, we investigated whether the addition of this molecule to peripheral blood mononuclear cells (PBMCs) would influence the expansion of regulatory B cell subsets, known to dampen autoimmune inflammation.

Methods:

Serum Tα1 level was measured by enzyme immunoassay. Cytokine expression was evaluated by Cytometric Bead Array (CBA), enzyme-linked immunosorbent assay (ELISA), and real-time reverse transcription polymerase chain reaction (RT-PCR). B cell subsets were analyzed by flow cytometry.

Results:

Tα1 pre-treatment induces an anti-inflammatory status in TLR7-stimulated RRMS PBMC cultures, reducing the secretion of pro-inflammatory interleukin (IL)-6, IL-8, and IL-1β while significantly increasing the regulatory IL-10 and IL-35. Indeed, Tα1 treatment enhanced expansion of CD19+CD24+CD38hi transitional-immature and CD24low/negCD38hi plasmablast-like regulatory B cell subsets, which likely inhibit both interferon (IFN)-γ and IL-17 production.

Conclusion::

Our study reveals a deficient ability of B cells from MS patients to differentiate into regulatory subsets and unveils a novel anti-inflammatory and repurposing potential for Tα1 in MS targeting B cell response.

Inebilizumab, a B Cell-Depleting Anti-CD19 Antibody for the Treatment of Autoimmune Neurological Diseases: Insights from Preclinical Studies

Exaggerated or inappropriate responses by B cells are an important feature in many types of autoimmune neurological diseases. The recent success of B-cell depletion in the treatment of multiple sclerosis (MS) has stimulated the development of novel B-cell-targeting therapies with the potential for improved efficacy. CD19 has emerged as a promising target for the depletion of B cells as well as CD19-positive plasmablasts and plasma cells. Inebilizumab (MEDI-551), an anti-CD19 antibody with enhanced antibody-dependent cell-mediated cytotoxicity against B cells, is currently being evaluated in MS and neuromyelitis optica. This review discusses the role of B cells in autoimmune neurological disorders, summarizes the development of inebilizumab, and analyzes the recent results for inebilizumab treatment in an autoimmune encephalitis mouse model. The novel insights obtained from these preclinical studies can potentially guide future investigation of inebilizumab in patients.

Circulating immune cells in multiple sclerosis

Circulating T and B lymphocytes contribute to the pathogenesis of the neuroinflammatory autoimmune disease, multiple sclerosis (MS). Further progress in the development of MS treatments is dependent upon a greater understanding of the immunological disturbances that underlie the disease. Analyses of circulating immune cells by flow cytometry have revealed MS-associated alterations in the composition and function of T and B cell subsets, including temporal changes associated with disease activity. Disturbances in circulating immune populations reflect those observed in the central nervous system and include skewing towards proinflammatory CD4⁺ and CD8⁺ T cells and B cells, greater proportions of follicular T helper cells and functional defects in the corresponding T and B regulatory subsets. Utilizing the analytical power of modern flow cytometers, researchers are now well positioned to monitor immunological changes associated with disease activity or intervention, describe immunological signatures with predictive value and identify targets for therapeutic drug development. This review discusses the contribution of various T and B lymphocyte subsets to MS pathogenesis, provides current and relevant phenotypical descriptions to assist in experimental design and highlights areas of future research.

CD19+CD24hiCD38hiBregs involved in downregulate helper T cells and upregulate regulatory T cells in gastric cancer

Regulatory B cells (Bregs) play a critical role in inflammation and autoimmune disease. We characterized the role of Bregs in the progression of gastric cancer. We detected an increase in Bregs producing IL-10 both in peripheral blood mononuclear cells (PBMCs) and in gastric tumors. Multicolor flow cytometry analysis revealed that a subset of CD19⁺CD24^hiCD38^hi B cells produces IL-10. Functional studies indicated that increased Bregs do not inhibit the proliferation of CD3⁺T cells or CD4⁺ helper T cells (Th cells). However, Bregs do suppress the secretion of IFN-γ and TNF-α by CD4⁺Th cells. CD19⁺CD24^hiCD38^hiBregs were also found to correlate positively with CD4⁺FoxP3⁺ regulatory T cells (Tregs). Neutralization experiments showed that Bregs convert CD4⁺CD25⁻ effector T cells to CD4⁺FoxP3⁺Tregs via TGF-β1. Collectively, these findings demonstrate that increased Bregs play a immunosuppressive role in gastric cancer by inhibiting T cells cytokines as well as conversion to Tregs. These results may provide new clues about the underlying mechanisms of immune escape in gastric cancer.

Role of regulatory b cells in neuroimmunologic disorders

B lymphocytes augment the immune response by producing antibodies and activating T cells by antigen presentation. Recent studies have highlighted a specific and functionally significant B-cell subset that could downregulate excessive immune and inflammatory responses through a vast array of inhibitory cytokines, such as interleukin (IL)-10 and transforming growth factor-β (TGF-β). This subset of B cells is generally referred to as regulatory B cells (Bregs). In addition, recent studies have shown that IL-35-producing Bregs also play a role in downregulation of immunity. Diverse phenotypes of Bregs have been proposed to underlie human disorders and their animal models. Most studies have focused on the role of different subsets of Bregs and Bregs-associated molecules such as IL-10, TGF-β, and IL-35 in the pathogenesis of neuroimmunologic disorders. Furthermore, Bregs exert regulatory function mainly through suppressing the differentiation of Th1/Th17 cells and promoting regulatory T-cell expansion. Reduced presence of Bregs is reportedly associated with progression of several neuroimmunologic disorders. This Review summarizes the current knowledge on the role of Bregs in neuroimmunologic disorders, including multiple sclerosis, neuromyelitis optica, and myasthenia gravis. © 2016 The Authors. Journal of Neuroscience Research Published by Wiley Periodicals, Inc.

Illuminating vitamin D effects on B cells--the multiple sclerosis perspective

Vitamin D is associated with many immune-mediated disorders. In multiple sclerosis (MS) a poor vitamin D status is a major environmental factor associated with disease incidence and severity. The inflammation in MS is primarily T-cell-mediated, but increasing evidence points to an important role for B cells. This has paved the way for investigating vitamin D effects on B cells. In this review we elaborate on vitamin D interactions with antibody production, T-cell-stimulating capacity and regulatory B cells. Although in vitro plasma cell generation and expression of co-stimulatory molecules are inhibited and the function of regulatory B cells is promoted, this is not supported by in vivo data. We speculate that differences might be explained by the B-cell-Epstein-Barr virus interaction in MS, the exquisite role of germinal centres in B-cell biology, and/or in vivo interactions with other hormones and vitamins that interfere with the vitamin D pathways. Further research is warranted to illuminate this tube-versus-body paradox.

Anti-B-Cell Therapies in Autoimmune Neurological Diseases: Rationale and Efficacy Trials

B cells have an ever-increasing role in the etiopathology of a number of autoimmune neurological disorders, acting as antibody-producing cells and, most importantly, as sensors, coordinators, and regulators of the immune response. B cells, among other functions, regulate the T-cell activation process through their participation in antigen presentation and production of cytokines. The availability of monoclonal antibodies or fusion proteins against B-cell surface molecules or B-cell trophic factors bestows a rational approach for treating autoimmune neurological disorders, even when T cells are the main effector cells. This review summarizes basic aspects of B-cell biology, discusses the role(s) of B cells in neurological autoimmunity, and presents anti-B-cell drugs that are either currently on the market or are expected to be available in the near future for treating neurological autoimmune disorders.

B Cells in the Multiple Sclerosis Central Nervous System: Trafficking and Contribution to CNS-Compartmentalized Inflammation

Clinical trial results of peripheral B cell depletion indicate abnormal proinflammatory B cell properties, and particularly antibody-independent functions, contribute to relapsing MS disease activity. However, potential roles of B cells in progressive forms of disease continue to be debated. Prior work indicates that presence of B cells is fostered within the inflamed MS central nervous system (CNS) environment, and that B cell-rich immune cell collections may be present within the meninges of patients. A potential association is reported between such meningeal immune cell collections and the subpial pattern of cortical injury that is now considered important in progressive disease. Elucidating the characteristics of B cells that populate the MS CNS, how they traffic into the CNS and how they may contribute to progressive forms of the disease has become of considerable interest. Here, we will review characteristics of human B cells identified within distinct CNS subcompartments of patients with MS, including the cerebrospinal fluid, parenchymal lesions, and meninges, as well as the relationship between B cell populations identified in these subcompartments and the periphery. We will further describe the different barriers of the CNS and the possible mechanisms of migration of B cells across these barriers. Finally, we will consider the range of human B cell responses (including potential for antibody production, cytokine secretion, and antigen presentation) that may contribute to propagating inflammation and injury cascades thought to underlie MS progression.

B Cells Are Multifunctional Players in Multiple Sclerosis Pathogenesis: Insights from Therapeutic Interventions

Multiple sclerosis (MS) is a severe disease of the central nervous system (CNS) characterized by autoimmune inflammation and neurodegeneration. Historically, damage to the CNS was thought to be mediated predominantly by activated pro-inflammatory T cells. B cell involvement in the pathogenesis of MS was solely attributed to autoantibody production. The first clues for the involvement of antibody-independent B cell functions in MS pathology came from positive results in clinical trials of the B cell-depleting treatment rituximab in patients with relapsing-remitting (RR) MS. The survival of antibody-secreting plasma cells and decrease in T cell numbers indicated the importance of other B cell functions in MS such as antigen presentation, costimulation, and cytokine production. Rituximab provided us with an example of how clinical trials can lead to new research opportunities concerning B cell biology. Moreover, analysis of the antibody-independent B cell functions in MS has gained interest since these trials. Limited information is present on the effects of current immunomodulatory therapies on B cell functions, although effects of both first-line (interferon, glatiramer acetate, dimethyl fumarate, and teriflunomide), second-line (fingolimod, natalizumab), and even third-line (monoclonal antibody therapies) treatments on B cell subtype distribution, expression of functional surface markers, and secretion of different cytokines by B cells have been studied to some extent. In this review, we summarize the effects of different MS-related treatments on B cell functions that have been described up to now in order to find new research opportunities and contribute to the understanding of the pathogenesis of MS.

Antigen Presentation, Autoantigens, and Immune Regulation in Multiple Sclerosis and Other Autoimmune Diseases

Antigen presentation is in the center of the immune system, both in host defense against pathogens, but also when the system is unbalanced and autoimmune diseases like multiple sclerosis (MS) develop. It is not just by chance that a major histocompatibility complex gene is the major genetic susceptibility locus in MS; a feature that MS shares with other autoimmune diseases. The exact etiology of the disease, however, has not been fully understood yet. T cells are regarded as the major players in the disease, but most probably a complex interplay of altered central and peripheral tolerance mechanisms, T-cell and B-cell functions, characteristics of putative autoantigens, and a possible interference of environmental factors like microorganisms are at work. In this review, new data on all these different aspects of antigen presentation and their role in MS will be discussed, probable autoantigens will be summarized, and comparisons to other autoimmune diseases will be drawn.