Impact of myelin-specific antigen presenting B cells on T cell activation in multiple sclerosis

Anti-CD20 therapies for pediatric-onset multiple sclerosis: A systematic review

BACKGROUND

Pediatric-onset multiple sclerosis (POMS) cases, defined as multiple sclerosis (MS) with onset before the age of 18, represent between 3 and 5 % of all MS patients. Anti-CD20 drugs mainly rituximab, ocrelizumab, and ofatumumab are being widely used in adult-onset MS. Their use in POMS is also being increasingly considered by experts.

OBJECTIVE

to review the latest evidence on safety and efficacy of the use of anti-CD20 therapies in POMS.

METHODS

An extensive search was performed in PubMed, Scopus, and Web of Science databases until the end of July 1st, 2024. Two independent reviewers screened the articles, and collected data. 832 studies were screened using Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines.

RESULTS

12 studies on rituximab (328 patients) and 6 studies on ocrelizumab (106 patients) were synthesized. Using monoclonal antibodies in POMS patients has a noteworthy effect on reducing relapses and lesions and achieving no evidence of disease activity especially in highly active POMS patients. However, anti-CD20 therapies in MS are associated with potential adverse events (AEs). Additional data is required on the effect of anti-CD20 therapy on disability accrual.

CONCLUSION

Although anti-CD20 therapy is associated with some AEs, it can be provided in several circumstances, especially to patients with highly active disease, or ones resistant to platform therapies.

The beneficial role of autophagy in multiple sclerosis: Yes or No?

Multiple sclerosis (MS) is a chronic progressive demyelinating disease of the central nervous system (CNS) due to an increase of abnormal peripherally auto-reactive T lymphocytes which elicit autoimmunity. The main pathophysiology of MS is myelin sheath damage by immune cells and a defect in the generation of myelin by oligodendrocytes. Macroautophagy/autophagy is a critical degradation process that eliminates dysfunctional or superfluous cellular components. Autophagy has the property of a double-edged sword in MS in that it may have both beneficial and detrimental effects on MS neuropathology. Therefore, this review illustrates the protective and harmful effects of autophagy with regard to this disease. Autophagy prevents the progression of MS by reducing oxidative stress and inflammatory disorders. In contrast, over-activated autophagy is associated with the progression of MS neuropathology and in this case the use of autophagy inhibitors may alleviate the pathogenesis of MS. Furthermore, autophagy provokes the activation of different immune and supporting cells that play an intricate role in the pathogenesis of MS. Autophagy functions in the modulation of MS neuropathology by regulating cell proliferation related to demyelination and remyelination. Autophagy enhances remyelination by increasing the activity of oligodendrocytes, and astrocytes. However, autophagy induces demyelination by activating microglia and T cells. In conclusion, specific autophagic activators of oligodendrocytes, and astrocytes, and specific autophagic inhibitors of dendritic cells (DCs), microglia and T cells induce protective effects against the pathogenesis of MS.Abbreviations: ALS: amyotrophic lateral sclerosis; APCs: antigen-presenting cells; BBB: blood-brain barrier; CSF: cerebrospinal fluid; CNS: central nervous system; DCs: dendritic cells; EAE: experimental autoimmune encephalomyelitis; ER: endoplasmic reticulum; LAP: LC3-associated phagocytosis; MS: multiple sclerosis; NCA: non-canonical autophagy; OCBs: oligoclonal bands; PBMCs: peripheral blood mononuclear cells; PD: Parkinson disease; ROS: reactive oxygen species; UPR: unfolded protein response.

Histamine H4 Receptor Agonist, 4-Methylhistamine, Aggravates Disease Progression and Promotes Pro-Inflammatory Signaling in B Cells in an Experimental Autoimmune Encephalomyelitis Mouse Model

We sought to assess the impact of 4-Methylhistamine (4-MeH), a specific agonist targeting the Histamine H4 Receptor (H4R), on the progression of experimental autoimmune encephalomyelitis (EAE) and gain insight into the underlying mechanism. EAE is a chronic autoimmune, inflammatory, and neurodegenerative disease of the central nervous system (CNS) characterized by demyelination, axonal damage, and neurodegeneration. Over the past decade, pharmacological research into the H4R has gained significance in immune and inflammatory disorders. For this study, Swiss Jim Lambert EAE mice were treated with 4-MeH (30 mg/kg/day) via intraperitoneal administration from days 14 to 42, and the control group was treated with a vehicle. Subsequently, we evaluated the clinical scores. In addition, flow cytometry was employed to estimate the impact of 4-Methylhistamine (4-MeH) on NF-κB p65, GM-CSF, MCP-1, IL-6, and TNF-α within CD19+ and CXCR5+ spleen B cells. Additionally, we investigated the effect of 4-MeH on the mRNA expression levels of Nf-κB p65, Gmcsf, Mcp1, Il6, and Tnfα in the brain of mice using RT-PCR. Notably, the clinical scores of EAE mice treated with 4-MeH showed a significant increase compared with those treated with the vehicle. The percentage of cells expressing CD19+NF-κB p65+, CXCR5+NF-κB p65+, CD19+GM-CSF+, CXCR5+GM-CSF+, CD19+MCP-1+, CXCR5+MCP-1+, CD19+IL-6+, CXCR5+IL-6+, CD19+TNF-α+, and CXCR5+TNF-α+ exhibited was more pronounced in 4-MeH-treated EAE mice when compared to vehicle-treated EAE mice. Moreover, the administration of 4-MeH led to increased expression of NfκB p65, Gmcsf, Mcp1, Il6, and Tnfα mRNA in the brains of EAE mice. This means that the H4R agonist promotes pro-inflammatory mediators aggravating EAE symptoms. Our results indicate the harmful role of H4R agonists in the pathogenesis of MS in an EAE mouse model.

Safety and Immune Effects of Blocking CD40 Ligand in Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Costimulation by CD40 and its ligand CD40L (CD154) is important for the functional differentiation of T cells. Preclinical studies have recognized the importance of this costimulatory interaction in the pathogenesis of experimental models of multiple sclerosis (MS). To determine safety, pharmacokinetics, and immune effect of a humanized monoclonal antibody (mAb) against CD40 ligand (toralizumab/IDEC-131) in patients with relapsing-remitting MS (RRMS).

METHODS

This single-institution open-label dose-escalation study (phase I) enrolled 12 patients with RRMS to receive 4 doses of 1, 5, 10, or 15 mg/kg of humanized αCD40L (toralizumab) IV infusion every other week. Patients were followed up to 18 weeks, annually, and finally at 5 years. In addition to safety and pharmacokinetics, other secondary and exploratory measurements are immune effects, clinical, MRI, laboratory, and neuropsychological evaluations.

RESULTS

Fifteen adverse events, all of mild to moderate severity, were considered to be of possible or of unknown relationship to treatment. No serious adverse events, including thromboembolic events, occurred during the 18-week defined study period. Annual and long-term follow-up at 5 years revealed no delayed toxicity. Pharmacokinetics were nonlinear between the 5 and 10 mg/kg dose groups. The serum half-life of toralizumab was consistent between the dose groups with a mean of 15.3 days (SD = 1.9). Flow cytometry revealed no depletion of lymphocyte subsets. An increase in the CD25+/CD3+ and CD25+/CD4+ ratio and a shift toward an anti-inflammatory cytokine response were seen after treatment.

DISCUSSION

Our study suggests that blocking CD40L is safe and well tolerated in patients with RRMS while increasing CD25 + T cells and anti-inflammatory cytokine profile. These findings support further studies to assess the efficacy of blocking CD40L as a potential treatment of RRMS.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence on the safety, pharmacokinetics, and immune effects of an mAb to CD40L in patients with RRMS.

The survival and function of IL-10-producing regulatory B cells are negatively controlled by SLAMF5

B cells have essential functions in multiple sclerosis and in its mouse model, experimental autoimmune encephalomyelitis, both as drivers and suppressors of the disease. The suppressive effects are driven by a regulatory B cell (Breg) population that functions, primarily but not exclusively, via the production of IL-10. However, the mechanisms modulating IL-10-producing Breg abundance are poorly understood. Here we identify SLAMF5 for controlling IL-10⁺ Breg maintenance and function. In EAE, the deficiency of SLAMF5 in B cells causes accumulation of IL10⁺ Bregs in the central nervous system and periphery. Blocking SLAMF5 in vitro induces both human and mouse IL-10-producing Breg cells and increases their survival with a concomitant increase of a transcription factor, c-Maf. Finally, in vivo SLAMF5 blocking in EAE elevates IL-10⁺ Breg levels and ameliorates disease severity. Our results suggest that SLAMF5 is a negative moderator of IL-10⁺ Breg cells, and may serve as a therapeutic target in MS and other autoimmune diseases.

Regulatory B (Breg) cells suppress excessive inflammation primary via the production of interleukin 10 (IL-10). Here the authors show that the function and homeostasis of mouse and human IL-10⁺ Breg cells are negatively regulated by the cell surface receptor, SLAMF5, to impact experimental autoimmunity, thereby hinting SLAMF5 as a potential target for immunotherapy.

Insights into the role of B cells in the cortical pathology of Multiple sclerosis: evidence from animal models and patients

Multiple sclerosis (MS) is a chronic, immune-mediated disease of the central nervous system (CNS) that affects both white and gray matter. Although it has been traditionally considered as a T cell mediated disease, the role of B cell in MS pathology has become a topic of great research interest. Cortical lesions, key feature of the progressive forms of MS, are involved in cognitive impairment and worsening of the patients' outcome. These lesions present pathognomonic hallmarks, such as: absence of blood-brain barrier (BBB) disruption, limited inflammatory events, reactive microglia, neurodegeneration, demyelination and meningeal inflammation. B cells located in the meninges, either as part of diffuse inflammation or as part of follicle-like structures, are strongly associated with cortical damage. The function of CD20-expressing B cells in MS is further highlighted by the success of specific therapies using anti-CD20 antibodies. The possible roles of B cells in pathology go beyond their ability to produce antibodies, as they also present antigens to T cells, secrete cytokines (both pathogenic and protective) within the CNS to modulate T and myeloid cell functions, and are involved in meningeal inflammation. Here, we will review the contributions of B cells to the pathogenesis of meningeal inflammation and cortical lesions in MS patients as well as in preclinical animal models.

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.

Effect of Cladribine on Neuronal Apoptosis: New Insight of In Vitro Study in Multiple Sclerosis Therapy

Background: Cladribine (2-CdA) can cross the blood–brain barrier, resulting in inhibition of DNA synthesis and repair and disruption of cellular proliferation in actively dividing lymphocytes. No data on effect on neurons are available. Aim: To study “in vitro” 2-CdA apoptotic effects on neurons in healthy donor and multiple sclerosis patient lymphocytes. Methods: Neuroblastoma cells were co-cultured with lymphocytes, with and without 2-CdA. Results: Apoptosis increased in lymphocytes with 2-CdA; increase was also observed when lymphocytes were cultured with neuronal cells. However, neurons were not affected by 2-CdA for apoptosis. Conclusions: 2-CdA causes peripheral and central lymphocyte death preserving neurons, with a reasonable impact on inflammation and neuroprotection.

The role of B cells in the immunopathogenesis of multiple sclerosis

There is ongoing debate on how B cells contribute to the pathogenesis of multiple sclerosis (MS). The success of B-cell targeting therapies in MS highlighted the role of B cells, particularly the antibody-independent functions of these cells such as antigen presentation to T cells and modulation of the function of T cells and myeloid cells by secreting pathogenic and/or protective cytokines in the central nervous system. Here, we discuss the role of different antibody-dependent and antibody-independent functions of B cells in MS disease activity and progression proposing new therapeutic strategies for the optimization of B-cell targeting treatments.

Impact of B cells to the pathophysiology of multiple sclerosis

Introduction

Multiple sclerosis (MS) is a chronic autoimmune disorder that affects the central nervous system and compromises the health and well-being of millions of people worldwide. B cells have been linked to MS and its progression. This review aimed to determine the role of B cells in MS development.

Methods

Articles used in this review were obtained from PubMed, LILACS, and EBSCO. The search terms and phrases included “multiple sclerosis,” “MS,” “B-Cells,” “pathogenesis,” and “development.” Original research studies and articles on MS and B cells published between 2007 and 2018 were included.

Results

Results from the selected articles showed a significant connection between B cell groups and MS. B cells act as a significant source of plasma cells, which generate antibodies while also regulating autoimmune processes and T cell production. In addition, B cells regulate the release of molecules that affect the proinflammatory actions of other immune cells.

Discussion

B cells play key roles in immune system functioning and MS. The findings of this review illustrate the complex nature of B cell actions, their effects on the autoimmune system, and the method by which they contribute to MS pathogenesis.

Conclusion

Previous research implicates biological, genetic, and environmental factors in MS pathogenesis. This review suggests that B cells contribute to MS development and advancement by influencing and regulating autoimmune processes such as T cell production and APC activity.

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

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

Abatacept Targets T Follicular Helper and Regulatory T Cells, Disrupting Molecular Pathways That Regulate Their Proliferation and Maintenance

Abatacept is a CTLA-4-Ig fusion protein that binds to the costimulatory ligands CD80 and CD86 and blocks their interaction with the CD28 and CTLA-4 receptors expressed by T cells, therefore inhibiting T cell activation and function. Abatacept has shown clinical efficacy in treating some autoimmune diseases but has failed to show clinical benefit in other autoimmune conditions. The reasons for these disparate results are not clear and warrant further investigation of abatacept's mode of action. Longitudinal specimens from the Immune Tolerance Network's A Cooperative Clinical Study of Abatacept in Multiple Sclerosis trial were used to examine the effects of abatacept treatment on the frequency and transcriptional profile of specific T cell populations in peripheral blood. We found that the relative abundance of CD4⁺ T follicular helper (Tfh) cells and regulatory T cells was selectively decreased in participants following abatacept treatment. Within both cell types, abatacept reduced the proportion of activated cells expressing CD38 and ICOS and was associated with decreased expression of genes that regulate cell-cycle and chromatin dynamics during cell proliferation, thereby linking changes in costimulatory signaling to impaired activation, proliferation, and decreased abundance. All cellular and molecular changes were reversed following termination of abatacept treatment. These data expand upon the mechanism of action of abatacept reported in other autoimmune diseases and identify new transcriptional targets of CD28-mediated costimulatory signaling in human regulatory T and Tfh cells, further informing on its potential use in diseases associated with dysregulated Tfh activity.

B cells are capable of independently eliciting rapid reactivation of encephalitogenic CD4 T cells in a murine model of multiple sclerosis

Recent success with B cell depletion therapies has revitalized efforts to understand the pathogenic role of B cells in Multiple Sclerosis (MS). Using the adoptive transfer system of experimental autoimmune encephalomyelitis (EAE), a murine model of MS, we have previously shown that mice in which B cells are the only MHCII-expressing antigen presenting cell (APC) are susceptible to EAE. However, a reproducible delay in the day of onset of disease driven by exclusive B cell antigen presentation suggests that B cells require optimal conditions to function as APCs in EAE. In this study, we utilize an in vivo genetic system to conditionally and temporally regulate expression of MHCII to test the hypothesis that B cell APCs mediate attenuated and delayed neuroinflammatory T cell responses during EAE. Remarkably, induction of MHCII on B cells following the transfer of encephalitogenic CD4 T cells induced a rapid and robust form of EAE, while no change in the time to disease onset occurred for recipient mice in which MHCII is induced on a normal complement of APC subsets. Changes in CD4 T cell activation over time did not account for more rapid onset of EAE symptoms in this new B cell-mediated EAE model. Our system represents a novel model to study how the timing of pathogenic cognate interactions between lymphocytes facilitates the development of autoimmune attacks within the CNS.

Role of TFH Cells in Promoting T Helper 17-Induced Neuroinflammation

Both T cells and B cells are implicated in the pathology of multiple sclerosis (MS), but how these cells cooperate to drive disease remains unclear. Recent studies using experimental autoimmune encephalomyelitis (EAE) demonstrated that the TH17 pathway is correlated with increased numbers of ectopic B-cell follicles in the central nervous system (CNS). As follicular T helper (TFH) cells are regulators of B cell responses, we sought to examine the role of TFH cells in EAE induced by the transfer of myelin-specific TH17 cells (TH17-EAE). In this study, we first confirmed previous reports that B-cells are a major cell type infiltrating the CNS during TH17-EAE. In addition, we found that B cells contribute to the severity of TH17-EAE. Class-switched B-cells in the CNS were positively correlated with disease and, strikingly, the severity TH17-EAE was diminished in B cell deficient mice. We next focused on the role TFH cells play in TH17-EAE. We found substantial numbers of CXCR5⁺PD1⁺CD4⁺ TFH cells in the CNS tissue of TH17-EAE mice and that at the peak of disease, the number of infiltrating TFHs was correlated with the number of infiltrating B-cells. Using congenic CD45.1⁺ donor mice and CD45.2⁺ recipient mice, we determined that the TFH cells were recipient-derived, whereas IL-17⁺ cells were donor-derived. We assessed whether myelin-specific TFH cells are capable of inducing EAE in recipient mice and found that transferring TFH cells failed to induce EAE. Finally, we tested the effects of blocking TFH trafficking in TH17-EAE using an antagonistic antibody against CXCL13, the chemokine ligand for CXCR5 on TFH cells. We found anti-CXCL13 treatment significantly reduced TH17-EAE disease. This treatment blocked CD4⁺ T cells from entering the CNS, but had no effect on infiltration of B cells. Strikingly, this antibody treatment had no measurable effect on TH17 disease in B cell-deficient mice. These data demonstrate that infiltrating TFH cells are a key cell type that contributes to an inflammatory B cell response in TH17-EAE and provide evidence for targeting TFH cells as a treatment for neuro-autoimmune diseases like MS.

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.

B-cell-targeted therapies in relapsing forms of MS

In recent years, there has been a significant increase in the therapeutic options available for the management of relapsing forms of MS. Therapies primarily targeting B cells, including therapeutic anti-CD20 monoclonal antibodies, have been evaluated in phase I, phase II, and phase III clinical trials. Results of these trials have shown their efficacy and relatively tolerable adverse effect profiles, suggesting a favorable benefit-to-risk ratio. In this review, we discuss the pathogenic role of B cells in MS and the rationale behind the utilization of B-cell depletion as a therapeutic cellular option. We also discuss the data of clinical trials for anti-CD20 antibodies in relapsing forms of MS and existing evidence for other B-cell–directed therapeutic strategies.

Ocrelizumab: a B-cell depleting therapy for multiple sclerosis

INTRODUCTION

Multiple sclerosis (MS) is the most common neurological disease responsible for early disability in the young working population. In the last two decades, based on retrospective/prospective data, the use of disease-modifying therapies has been shown to slow the rate of disability progression and prolonged the time to conversion into secondary-progressive MS (SPMS). However, despite the availability of several approved therapies, disability progression cannot be halted significantly in all MS patients. Areas covered: This article reviews the immunopathology of the B-cells, and their role in pathogenesis of MS and their attractiveness as a potential therapeutic target in MS. The review focuses on the recently published ocrelizumab phase III trials in terms of its efficacy, safety, and tolerability as well as its future considerations. Expert opinion: B lymphocyte cell depletion therapy offers a compelling and promising new option for MS patients. Nonetheless, there is a need for heightened vigilance and awareness in detecting potential long-term consequences that currently remain unknown.

Age-Associated B Cells with Proinflammatory Characteristics Are Expanded in a Proportion of Multiple Sclerosis Patients

Immune aging occurs in the elderly and in autoimmune diseases. Recently, IgD^-CD27^- (double negative, DN) and CD21^-CD11c⁺ (CD21^low) B cells were described as age-associated B cells with proinflammatory characteristics. This study investigated the prevalence and functional characteristics of DN and CD21^low B cells in multiple sclerosis (MS) patients. Using flow cytometry, we demonstrated a higher proportion of MS patients younger than 60 y with peripheral expansions of DN (8/41) and CD21^low (9/41) B cells compared with age-matched healthy donors (1/33 and 2/33, respectively), which indicates an increase in age-associated B cells in MS patients. The majority of DN B cells had an IgG⁺ memory phenotype, whereas CD21^low B cells consisted of a mixed population of CD27^- naive, CD27⁺ memory, IgG⁺, and IgM⁺ cells. DN B cells showed similar (MS patients) or increased (healthy donors) MHC-II expression as class-switched memory B cells and intermediate costimulatory molecule expression between naive and class-switched memory B cells, indicating their potential to induce (proinflammatory) T cell responses. Further, DN B cells produced proinflammatory and cytotoxic cytokines following ex vivo stimulation. Increased frequencies of DN and CD21^low B cells were found in the cerebrospinal fluid of MS patients compared with paired peripheral blood. In conclusion, a proportion of MS patients showed increased peripheral expansions of age-associated B cells. DN and CD21^low B cell frequencies were further increased in MS cerebrospinal fluid. These cells could contribute to inflammation by induction of T cell responses and the production of proinflammatory cytokines.

B cells of multiple sclerosis patients induce autoreactive proinflammatory T cell responses

Antibody-independent B cell functions play an important role in multiple sclerosis (MS) pathogenesis. In this study, B cell antigen presentation and costimulation in MS were studied. Peripheral blood B cells of MS patients showed increased expression of costimulatory CD86 and CD80 molecules compared with healthy controls (HC). In MS cerebrospinal fluid (CSF), 12-fold and 2-fold increases in CD86⁺ and CD80⁺ B cells, respectively, were evidenced compared with peripheral blood. Further, B cells from MS patients induced proinflammatory T cells in response to myelin basic protein (MBP). Immunomodulatory treatment restored B cell costimulatory molecule expression and caused significantly reduced B cell induced T cell responses. Together, these results demonstrate the potential of B cells from MS patients to induce autoreactive proinflammatory T cell responses. Immunomodulatory therapy abrogated this effect, emphasizing the importance of B cell antigen presentation and costimulation in MS pathology.

CD20 therapies in multiple sclerosis and experimental autoimmune encephalomyelitis - Targeting T or B cells?

MS is widely considered to be a T cell-mediated disease although T cell immunotherapy has consistently failed, demonstrating distinct differences with experimental autoimmune encephalomyelitis (EAE), an animal model of MS in which T cell therapies are effective. Accumulating evidence has highlighted that B cells also play key role in MS pathogenesis. The high frequency of oligoclonal antibodies in the CSF, the localization of immunoglobulin in brain lesions and pathogenicity of antibodies originally pointed to the pathogenic role of B cells as autoantibody producing plasma cells. However, emerging evidence reveal that B cells also act as antigen presenting cells, T cell activators and cytokine producers suggesting that the strong efficacy of anti-CD20 antibody therapy observed in people with MS may reduce disease progression by several different mechanisms. Here we review the evidence and mechanisms by which B cells contribute to disease in MS compared to findings in the EAE model.

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 from relapsing remitting multiple sclerosis patients support neuro-antigen-specific Th17 responses

B cells are highly potent antigen presenting cells of their cognate antigens. However, it remains unknown whether B cells can orchestrate Th17-mediated responses against neuro-antigens. We report that MS patients and healthy donors had a similar frequency of antigen-specific Th1 and Th17 cells, and distribution of T effector and T central memory cells. Notwithstanding these similarities, the application of an in vitro assay demonstrated that the B cells derived from a subset of MS patients exhibited the capability of coordinating Th17 responses directed toward neuro-antigens. These observations underscore the B cell's contribution to the putative underpinnings of multiple sclerosis.

Role of B cells in presentation of autoantigens to CD4(+) T cells in patients with autoimmune thyroiditis

The antigen-presenting activity of B cells and expression of molecules involved in antigen presentation by B cells have been studied in patients with autoimmune thyroiditis (AIT). The disease is characterized by enhanced expression of the costimulatory molecule CD80 in naive B cells (CD19(+)CD27(-) cells) both ex vivo and under the conditions of polyclonal cell activation in a culture. Under in vitro conditions, antigen-loaded B cells have been shown to be capable of inducing proliferation of autologous CD4(+) cells, in particular, proliferation of autospecific T cells in patients with AIT. Given that an intense infiltration of thyroid tissue by B cells is a typical sign of AIT, the antigen-presenting activity of B cells appears to contribute to this pathology.

Differential Antigen-presenting B Cell Phenotypes from Synovial Microenvironment of Patients with Rheumatoid and Psoriatic Arthritis

OBJECTIVE

To study the qualitative and quantitative phenotypic changes that occur in molecules involved in antigen presentation and costimulation in synovial B cells from rheumatoid arthritis (RA) and psoriatic arthritis (PsA).

METHODS

The presence of HLA-DR, CD86, and CD40 in CD20+ cells was studied in RA synovium biopsies using immunohistochemistry and immunofluorescence. Expression was assessed by flow cytometry of the Class II molecules CD40, CD86, CD23, and CD27 on B cells from the synovial fluid (SF), with respect to peripheral blood, from 13 patients with RA and 15 patients with PsA. Expression of interferon-induced protein with tetratricopeptide repeats 4 (IFIT4) in immune-selected CD20+ cells from patients with RA was assessed by quantitative realtime PCR.

RESULTS

Infiltrating synovial RA, B cells expressed HLA-DR, CD40, and CD86. Increased expression of CD86, HLA-DR, and HLA-DQ in B cells from SF was found in patients with RA and PsA. HLA-DP was also elevated in rheumatoid SF B cells; conversely, a significantly lower expression was observed in SF from patients with PsA. CD40 expression was increased in SF B cells from PsA, but not in patients with RA. Interestingly, CD20 surface expression level was significantly lower in SF B cells (CD19+, CD138-) from RA, but not in patients with PsA. CD27 upregulation and CD23 downregulation were observed in synovial B cells in both pathologies. Finally, a 4-fold increase in IFIT4 mRNA content was shown in B cells from SF in patients with RA.

CONCLUSION

Synovial B cells from patients with RA and patients with PsA express different antigen-presenting cell phenotypes, suggesting that this cell type plays a dissimilar role in the pathogenesis of each disease.

Tertiary Lymphoid Structure-Associated B Cells are Key Players in Anti-Tumor Immunity

It is now admitted that the immune system plays a major role in tumor control. Besides the existence of tumor-specific T cells and B cells, many studies have demonstrated that high numbers of tumor-infiltrating lymphocytes are associated with good clinical outcome. In addition, not only the density but also the organization of tumor-infiltrating immune cells has been shown to determine patient survival. Indeed, more and more studies describe the development within the tumor microenvironment of tertiary lymphoid structures (TLS), whose presence has a positive impact on tumor prognosis. TLS are transient ectopic lymphoid aggregates displaying the same organization and functionality as canonical secondary lymphoid organs, with T-cell-rich and B-cell-rich areas that are sites for the differentiation of effector and memory T cells and B cells. However, factors favoring the emergence of such structures within tumors still need to be fully characterized. In this review, we survey the state of the art of what is known about the general organization, induction, and functionality of TLS during chronic inflammation, and more especially in cancer, with a particular focus on the B-cell compartment. We detail the role played by TLS B cells in anti-tumor immunity, both as antigen-presenting cells and tumor antigen-specific antibody-secreting cells, and raise the question of the capacity of chemotherapeutic and immunotherapeutic agents to induce the development of TLS within tumors. Finally, we explore how to take advantage of our knowledge on TLS B cells to develop new therapeutic tools.

Impaired T cell activation and cytokine production by calcitriol-primed human B cells

The biologically active form of vitamin D3 , 1, 25-dihydroxyvitamin D3 (calcitriol), is a potent modulator of the immune response. We have shown previously that calcitriol modulates the immunoglobulin response in vitro and in vivo in mice and humans. To analyse the underlying molecular mechanisms we studied whether calcitriol-primed B cells modulate T cell activation and function. Human B cells were stimulated with anti-CD40 and interleukin (IL)-4 in the presence of increasing concentrations of calcitriol. After removal of calcitriol, primed B cells were co-cultured with autologous CD4(+) T cells; the B cell phenotype T cell activation and their consecutive cytokine production were also assessed. Naive T cells co-cultured with calcitriol-primed naive B cells showed a reduced expansion, nuclear factor of activated T cells, cytoplasmic 2 (NFATc2) expression and cytokine production upon restimulation. CD86 expression on B cells after calcitriol priming was identified as an underlying mechanism, as T cell activation and expansion was rescued by activating anti-CD28 antibodies. Our data indicate that calcitriol-primed B cells display an impaired capacity to activate T cells. Taken together, we identified a novel B cell-dependent vitamin D immune regulatory mechanism, namely by decreased co-stimulation of calcitriol-primed B cells.

Anti-CD20 inhibits T cell-mediated pathology and microgliosis in the rat brain

OBJECTIVE

The mechanism of action of anti-B cell therapy in multiple sclerosis (MS) is not fully understood. Here, we compared the effect of anti-CD20 therapy on microglial activation in two distinct focal rat models of MS.

METHODS

The effect of anti-CD20 therapy on lesion formation and extralesional microglial activation was evaluated in the fDTH-EAE (experimental allergic encephalomyelitis) model, which is a focal demyelinating type-IV delayed-type hypersensitivity lesion. For comparison, effects were also assessed in the focal humoral MOG model induced by intracerebral injection of cytokine in myelin oligodendrocyte glycoprotein immunized rats. Microglial activation was assessed in situ and in vivo using the TSPO SPECT ligand [(125)I]DPA-713, and by immunostaining for MHCII. The effect of treatment on demyelination and lymphocyte recruitment to the brain were evaluated.

RESULTS

Anti-CD20 therapy reduced microglial activation, and lesion formation in the humoral model, but it was most effective in the antibody-independent fDTH-EAE. Immunohistochemistry for MHCII also demonstrated a reduced volume of microglial activation in the brains of anti-CD20-treated fDTH-EAE animals, which was accompanied by a reduction in T-cell recruitment and demyelination. The effect anti-CD20 therapy in the latter model was similarly strong as compared to the T-cell targeting MS compound FTY720.

INTERPRETATION

The suppression of lesion development by anti-CD20 treatment in an antibody-independent model suggests that B-cells play an important role in lesion development, independent of auto-antibody production. Thus, CD20-positive B-cell depletion has the potential to be effective in a wider population of individuals with MS than might have been predicted from our knowledge of the underlying histopathology.

Targeting B cells in the treatment of multiple sclerosis: recent advances and remaining challenges

Recent years have substantially broadened our view on the pathogenesis of multiple sclerosis (MS). While earlier concepts focused predominantly on T lymphocytes as the key cell type to mediate inflammatory damage within central nervous system (CNS) lesions, emerging evidence suggests that B lymphocytes may play a comparably important role both as precursors of antibody-secreting plasma cells and as antigen-presenting cells (APCs) for the activation of T cells. With greater appreciation of this pathogenic B-cell function in MS, B-cell-directed therapies, and in particular B-cell-depleting monoclonal antibodies targeting the CD20 molecule, have gained enormous interest over recent years. Clinical trials demonstrated that anti-CD20 treatment, which depletes immature and mature B cells but spares CD20 negative plasma cells, rapidly reduces formation of new inflammatory CNS lesions. While these findings clearly corroborate a pathogenic contribution of B cells, recent experimental but also clinical findings indicate that not all B cells contribute in an equally pathogenic manner and that certain subsets may in contrast mediate anti-inflammatory effects. In this review, we summarize current findings in support of pathogenic B-cell function in MS, including the encouraging clinical data which derived from anti-CD20 MS trials. Further, we review novel findings suggestive of regulatory properties of B-cell subsets which may be collaterally abolished by pan-CD20 depletion. In conclusion, we aim to provide an outlook on how this currently differentiating concept of pro- and anti-inflammatory B-cell function could be harnessed to further improve safety and effectiveness of B-cell-directed therapeutic approaches in MS.

What do effective treatments for multiple sclerosis tell us about the molecular mechanisms involved in pathogenesis?

Multiple sclerosis is a potentially debilitating disease of the central nervous system. A concerted program of research by many centers around the world has consistently demonstrated the importance of the immune system in its pathogenesis. This knowledge has led to the formal testing of a number of therapeutic agents in both animal models and humans. These clinical trials have shed yet further light on the pathogenesis of MS through their sometimes unexpected effects and by their differential effects in terms of impact on relapses, progression of the disease, paraclinical parameters (MRI) and the adverse events that are experienced. Here we review the currently approved medications for the commonest form of multiple sclerosis (relapsing-remitting) and the emerging therapies for which preliminary results from phase II/III clinical trials are available. A detailed analysis of the molecular mechanisms responsible for the efficacy of these medications in multiple sclerosis indicates that blockade or modulation of both T- and B-cell activation and migration pathways in the periphery or CNS can lead to amelioration of the disease. It is hoped that further therapeutic trials will better delineate the pathogenesis of MS, ultimately leading to even better treatments with fewer adverse effects.

Laquinimod modulates B cells and their regulatory effects on T cells in multiple sclerosis

Laquinimod is an orally administered drug under development for the treatment of Multiple Sclerosis (MS), lacking a fully elucidated mode of action. We assessed the immunomodulatory effects of laquinimod in vitro on human B cells from healthy or MS patients, cultured alone or with CD4(+) T cells. Laquinimod modulated B cell markers, mainly by increasing the regulatory ones CD25, IL10 and CD86, and decreased IL4, while increasing IL10 and TGFβ in both B and T cells, in a B cell-mediated manner. These findings shed additional light on the mechanisms underlying the effects of laquinimod in MS and potentially other immune-mediated diseases.

The immunomodulatory and neuroprotective effects of mesenchymal stem cells (MSCs) in experimental autoimmune encephalomyelitis (EAE): a model of multiple sclerosis (MS)

Mesenchymal stem cells (MSCs) are multipotent cells that differentiate into the mesenchymal lineages of adipocytes, osteocytes and chondrocytes. MSCs can also transdifferentiate and thereby cross lineage barriers, differentiating for example into neurons under certain experimental conditions. MSCs have anti-proliferative, anti-inflammatory and anti-apoptotic effects on neurons. Therefore, MSCs were tested in experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), for their effectiveness in modulating the pathogenic process in EAE to develop effective therapies for MS. The data in the literature have shown that MSCs can inhibit the functions of autoreactive T cells in EAE and that this immunomodulation can be neuroprotective. In addition, MSCs can rescue neural cells via a mechanism that is mediated by soluble factors, which provide a suitable environment for neuron regeneration, remyelination and cerebral blood flow improvement. In this review, we discuss the effectiveness of MSCs in modulating the immunopathogenic process and in providing neuroprotection in EAE.

CD20+ tumor-infiltrating lymphocytes have an atypical CD27- memory phenotype and together with CD8+ T cells promote favorable prognosis in ovarian cancer

PURPOSE

Tumor-infiltrating lymphocytes (TIL), in particular CD8(+) T cells and CD20(+) B cells, are strongly associated with survival in ovarian cancer and other carcinomas. Although CD8(+) TIL can mediate direct cytolytic activity against tumors, the role of CD20(+) TIL is poorly understood. Here, we investigate the possible contributions of CD20(+) TIL to humoral and cellular tumor immunity.

EXPERIMENTAL DESIGN

Tumor and serum specimens were obtained from patients with high-grade serous ovarian cancer. CD8(+) and CD20(+) TIL were analyzed by immunohistochemistry and flow cytometry. Immunoglobulin molecules were evaluated by DNA sequencing. Serum autoantibody responses to the tumor antigens p53 and NY-ESO-1 were measured by ELISA.

RESULTS

The vast majority of CD20(+) TIL were antigen experienced, as evidenced by class-switching, somatic hypermutation, and oligoclonality, yet they failed to express the canonical memory marker CD27. CD20(+) TIL showed no correlation with serum autoantibodies to p53 or NY-ESO-1. Instead, they colocalized with activated CD8(+) TIL and expressed markers of antigen presentation, including MHC class I, MHC class II, CD40, CD80, and CD86. The presence of both CD20(+) and CD8(+) TIL correlated with increased patient survival compared with CD8(+) TIL alone.

CONCLUSIONS

In high-grade serous ovarian tumors, CD20(+) TIL have an antigen-experienced but atypical CD27(-) memory B-cell phenotype. They are uncoupled from serum autoantibodies, express markers of antigen-presenting cells, and colocalize with CD8(+) T cells. We propose that the association between CD20(+) TIL and patient survival may reflect a supportive role in cytolytic immune responses.

Evidence for the role of B cells and immunoglobulins in the pathogenesis of multiple sclerosis

The pathogenesis of multiple sclerosis (MS) remains elusive. Recent reports advocate greater involvement of B cells and immunoglobulins in the initiation and propagation of MS lesions at different stages of their ontogeny. The key role of B cells and immunoglobulins in pathogenesis was initially identified by studies in which patients whose fulminant attacks of demyelination did not respond to steroids experienced remarkable functional improvement following plasma exchange. The positive response to Rituximab in Phase II clinical trials of relapsing-remitting MS confirms the role of B cells. The critical question is how B cells contribute to MS. In this paper, we discuss both the deleterious and the beneficial roles of B cells and immunoglobulins in MS lesions. We provide alternative hypotheses to explain both damaging and protective antibody responses.

Primed status of transitional B cells associated with their presence in the cerebrospinal fluid in early phases of multiple sclerosis

In the present study we showed that transitional B cells of patients with clinically isolated syndrome (CIS) and relapsing-remitting multiple sclerosis (RR-MS) are reduced in the peripheral blood (PB) (5.5- and 3.7-fold, respectively). In addition, these cells appeared to up-regulate different integrins (α4 and β1). These observations were associated with a primed cellular status, confirmed by an increased proportion of circulating CD80(+) transitional B cells. Interestingly, these results correlate with presence of transitional B cells in the CSF. Furthermore, these cells were absent in the CSF of individuals with other inflammatory neurological disease, and their levels in paired PB and CD80 expression were normal. Altogether, our data revealed that a differential primed status of transitional B cells is a characteristic feature of early phases of MS disease, and this functional status is associated with the ability of these cells to cross the blood-CSF barrier.

Potential impact of B cells on T cell function in multiple sclerosis

Multiple sclerosis is a chronic debilitating autoimmune disease of the central nervous system. The contribution of B cells in the pathoetiology of MS has recently been highlighted by the emergence of rituximab, an anti-CD20 monoclonal antibody that specifically depletes B cells, as a potent immunomodulatory therapy for the treatment of MS. However, a clearer understanding of the impact B cells have on the neuro-inflammatory component of MS pathogenesis is needed in order to develop novel therapeutics whose affects on B cells would be beneficial and not harmful. Since T cells are known mediators of the pathology of MS, the goal of this review is to summarize what is known about the interactions between B cells and T cells, and how current and emerging immunotherapies may impact B-T cell interactions in MS.

Estrogen-induced protection against experimental autoimmune encephalomyelitis is abrogated in the absence of B cells

Increased remissions in multiple sclerosis (MS) during pregnancy suggest that elevated levels of sex steroids exert immunoregulatory activity. Estrogen (E2=17β-estradiol) protects against experimental autoimmune encephalomyelitis (EAE), but the cellular basis for E2-induced protection remains unclear. Studies demonstrate that depletion of B cells prior to induction of EAE exacerbates disease severity, implicating regulatory B cells. We thus evaluated pathogenic and E2-induced protective mechanisms in B-cell-deficient (μMT(-/-)) mice. EAE-protective effects of E2 were abrogated in μMT(-/-) mice, with no reduction in disease severity, cellular infiltration or pro-inflammatory factors in the central nervous system compared to untreated controls. E2 treatment of WT mice selectively upregulated expression of PD-L1 on B cells and increased the percentage of IL-10-producing CD1d(high) CD5(+) regulatory B cells. Upregulation of PD-L1 was critical for E2-mediated protection since E2 did not inhibit EAE in PD-L1(-/-) mice. Direct treatment of B cells with E2 significantly reduced proliferation of MOG(35-55)-specific T cells that required estrogen receptor-α (ERα). These results demonstrate, for the first time, a requirement for B cells in E2-mediated protection against EAE involving direct E2 effects on regulatory B cells mediated through ERα and the PD-1/PD-L1 negative co-stimulatory pathway. E2-primed B cells may represent an important regulatory mechanism in MS and have strong implications for women receiving current MS therapies that cause B-cell depletion.

Interferon-beta increases systemic BAFF levels in multiple sclerosis without increasing autoantibody production

BACKGROUND

Treatment with interferon-beta (IFN-beta) increases B-cell activating factor of the TNF family (BAFF) expression in multiple sclerosis (MS), raising the concern that treatment of MS patients with IFN-beta may activate autoimmune B cells and stimulate the production of MS-associated autoantibodies.

OBJECTIVE

To investigate whether BAFF levels are associated with disease severity/activity in untreated MS patients, and to assess the effect of IFN-beta therapy on circulating BAFF and anti-myelin basic protein (MBP) autoantibody levels.

RESULTS

Twenty-three patients with relapsing-remitting MS (RRMS) were followed longitudinally from initiation of IFN-beta therapy. Their blood levels of BAFF correlated positively at baseline with the expanded disability status scale (p<0.009) and MS severity score (p<0.05), but not with disease activity as determined by the number of gadolinium-enhanced lesions. The patients were followed for up to 26 months, during which the BAFF levels remained elevated without association to increased disease activity. IFN-beta therapy caused an increase in plasma BAFF levels after both 3 and 6 months of therapy (p<0.002). However, an 11% decrease in IgM and a 33% decrease in IgG anti-MBP autoantibodies (p<0.09 and p<0.009, respectively) was observed after 6 months.

CONCLUSION

Pre-treatment BAFF levels correlate with high disability scores in MS, suggesting that high BAFF expression is a negative prognostic marker. Despite its known beneficial effects, IFN-beta therapy causes a sustained increase in plasma BAFF levels, which does not translate into increased levels of anti-MBP autoantibodies.

Memory B cells from a subset of treatment-naïve relapsing-remitting multiple sclerosis patients elicit CD4(+) T-cell proliferation and IFN-γ production in response to myelin basic protein and myelin oligodendrocyte glycoprotein

Recent evidence suggests that B- and T-cell interactions may be paramount in relapsing-remitting MS (RRMS) disease pathogenesis. We hypothesized that memory B-cell pools from RRMS patients may specifically harbor a subset of potent neuro-APC that support neuro-Ag reactive T-cell proliferation and cytokine secretion. To test this hypothesis, we compared CD80 and HLA-DR expression, IL-10 and lymphotoxin-α secretion, neuro-Ag binding capacity, and neuro-Ag presentation by memory B cells from RRMS patients to naïve B cells from RRMS patients and to memory and naïve B cells from healthy donors (HD). We identified memory B cells from some RRMS patients that elicited CD4(+) T-cell proliferation and IFN-γ secretion in response to myelin basic protein and myelin oligodendrocyte glycoprotein. Notwithstanding the fact that the phenotypic parameters that promote efficient Ag presentation were observed to be similar between RRMS and HD memory B cells, a corresponding capability to elicit CD4(+) T-cell proliferation in response to myelin basic protein and myelin oligodendrocyte glycoprotein was not observed in HD memory B cells. Our results demonstrate for the first time that the memory B-cell pool in RRMS harbors neuro-Ag specific B cells that can activate T cells.

Susceptibility to experimental autoimmune encephalomyelitis is associated with altered B-cell subsets distribution and decreased serum BAFF levels

B cells possess the ability to regulate either pathogenic or protective events in several autoimmune diseases such as multiple sclerosis (MS) and its experimental model, experimental autoimmune encephalomyelitis (EAE). Given the extensive use of B-cell-targeting treatments, it appears crucial to more precisely define the dual role of B cells in the progression of the disease. In the present study, we explored the impact of EAE induction on the distribution of potential regulatory B-cell subsets (CD5(+) B1a, marginal zone and transitional 2 B cells) over critical time points in the relapsing-remitting EAE model, SJL/J (H2s). The same approach was carried out in B10.S mice that are resistant to EAE induction, (H2s). The comparative data obtained from these experiments showed that the homeostasis of the regulatory B-cell subsets is altered during the EAE preclinical and acute phases. These observations were associated with a distortion of the BAFF response. All these data suggest the existence of a close relationship between B-cell homeostasis, BAFF response and the susceptibility to develop EAE.

Changes in B- and T-lymphocyte and chemokine levels with rituximab treatment in multiple sclerosis

BACKGROUND

B cells are implicated in the pathogenesis of multiple sclerosis. A beneficial effect of B-cell depletion using rituximab has been shown, but the complete mechanism of action for this drug is unclear.

OBJECTIVE

To determine the relationship between T and B cells and changes in cerebrospinal fluid (CSF) chemokine levels with rituximab, a monoclonal antibody that targets CD20.

DESIGN

Phase 2 trial of rituximab as an add-on therapy.

SETTING

The John L. Trotter Multiple Sclerosis Center, Washington University. Participants and Intervention Thirty subjects who had relapsing-remitting multiple sclerosis with clinical and magnetic resonance imaging activity despite treatment with an immunomodulatory drug received 4 weekly doses of rituximab (375 mg/m(2)).

MAIN OUTCOME MEASURES

Lumbar puncture was performed before and after rituximab infusions in 26 subjects. Levels of B and T lymphocytes in the CSF were enumerated by flow cytometry, and chemoattractant levels were measured by enzyme-linked immunosorbent assay.

RESULTS

After rituximab administration, CSF B-cell levels were decreased or undetectable in all subjects, and CSF T-cell levels were reduced in 21 subjects (81%). The mean reduction in CSF cellularity was 95% for B cells and 50% for T cells. After rituximab infusion, CSF CXCL13 and CCL19 levels decreased (P = .002 and P = .03, respectively). The proportional decline in CSF T-cell levels correlated with the proportional decrease in CXCL13 levels (r = 0.45; P = .03), suggesting a possible relationship. The CSF IgG index, IgG concentration, and oligoclonal band number were unchanged following treatment.

CONCLUSIONS

In subjects with multiple sclerosis, B cells are critical for T-cell trafficking into the central nervous system and may alter the process by influencing chemokine production within the central nervous system.

Role of platelets in neuroinflammation: a wide-angle perspective

OBJECTIVES

This review summarizes recent developments in platelet biology relevant to neuroinflammatory disorders. Multiple sclerosis (MS) is taken as the "Poster Child" of these disorders but the implications are wide. The role of platelets in inflammation is well appreciated in the cardiovascular and cancer research communities but appears to be relatively neglected in neurological research.

ORGANIZATION

After a brief introduction to platelets, topics covered include the matrix metalloproteinases, platelet chemokines, cytokines and growth factors, the recent finding of platelet PPAR receptors and Toll-like receptors, complement, bioactive lipids, and other agents/functions likely to be relevant in neuroinflammatory diseases. Each section cites literature linking the topic to areas of active research in MS or other disorders, including especially Alzheimer's disease.

CONCLUSION

The final section summarizes evidence of platelet involvement in MS. The general conclusion is that platelets may be key players in MS and related disorders, and warrant more attention in neurological research.

Meningeal inflammation is not associated with cortical demyelination in chronic multiple sclerosis

Cortical demyelination can be extensive in chronic multiple sclerosis (MS) patients. Cortical lesions are not associated with lymphocyte infiltration, blood-brain barrier disruption, or complement deposition; therefore, their pathogenesis is unclear. We analyzed the extent and cellular composition of leptomeningeal inflammatory infiltrates and their relationship with cortical demyelinated lesions in brain autopsy samples from 28 chronic MS patients; samples from 6 nonneurological disease control patients were also studied. Immunohistochemistry was used to detect meningeal T cells, B cells, macrophages, mature and immature dendritic cells, T-helper cells, (activated) cytotoxic T cells, and plasma cells. Quantitative analysis revealed significant meningeal inflammation in chronic MS patients; T cells were the predominant inflammatory cells. Morphometric analysis was performed on coronal hemisphere sections of the MS cases to assess subpial demyelination; no correlation between the extent of subpial demyelination and extent of meningeal inflammation was identified. Moreover, no differences were observed in the degree or cellular composition of meningeal infiltrates in areas directly adjacent to subpial lesions compared with areas adjacent to normal-appearing gray matter in the MS cases. In addition, no follicle-like structures were found in the MS samples. Our data suggest that the occurrence of cortical lesions is not related to the presence of meningeal inflammation in a large number of chronic MS patients.

In vivo sensitized and in vitro activated B cells mediate tumor regression in cancer adoptive immunotherapy

Adoptive cellular immunotherapy utilizing tumor-reactive T cells has proven to be a promising strategy for cancer treatment. However, we hypothesize that successful treatment strategies will have to appropriately stimulate not only cellular immunity, but also humoral immunity. We previously reported that B cells in tumor-draining lymph nodes (TDLNs) may function as APCs. In this study, we identified TDLN B cells as effector cells in an adoptive immunotherapy model. In vivo primed and in vitro activated TDLN B cells alone mediated effective (p < 0.05) tumor regression after adoptive transfer into two histologically distinct murine pulmonary metastatic tumor models. Prior lymphodepletion of the host with either chemotherapy or whole-body irradiation augmented the therapeutic efficacy of the adoptively transferred TDLN B cells in the treatment of s.c. tumors as well as metastatic pulmonary tumors. Furthermore, B cell plus T cell transfers resulted in substantially more efficient antitumor responses than B cells or T cells alone (p < 0.05). Activated TDLN B cells conferred strong humoral responses to tumor. This was evident by the production of IgM, IgG, and IgG2b, which bound specifically to tumor cells and led to specific tumor cell lysis in the presence of complement. Collectively, these data indicate that in vivo primed and in vitro activated B cells can be employed as effector cells for cancer therapy. The synergistic antitumor efficacy of cotransferred activated B effector cells and T effector cells represents a novel approach for cancer adoptive immunotherapy.

Cooperation of B cells and T cells in the pathogenesis of multiple sclerosis

B cells and T cells are two major players in the pathogenesis of multiple sclerosis (MS) and cooperate at various check points. B cells, besides serving as a source for antibody-secreting plasma cells, are efficient antigen presenting cells for processing of intact myelin antigen and subsequent activation and pro-inflammatory differentiation of T cells. This notion is supported by the immediate clinical benefit of therapeutic B cell depletion in MS, presumably abrogating development of encephalitogenic T cells. However, different B cell subsets strongly vary in their respective effect on T cell differentiation which may relate to B cell phenotype, activation status, antigen specificity and the immunological environment where a B cell encounters a naïve T cell in. In this regard, some B cells also have anti-inflammatory properties producing regulatory cytokines and facilitating development and maintenance of other immunomodulatory immune cells, such as regulatory T cells. Reciprocally, differentiated T cells influence T cell polarizing B cell properties establishing a positive feedback loop of joint pro- or anti-inflammatory B and T cell developments. Further, under the control of activated T helper cells, antigen-primed B cells can switch immunoglobulin isotype, terminally commit to the plasma cell pathway or enter the germinal center reaction to memory B Cell development. Taken together, B cells and T cells thus closely support one another to participate in the pathogenesis of MS in an inflammatory but also in a regulatory manner.