B-cell depletion with rituximab in relapsing-remitting multiple sclerosis

Monoclonal antibody treatments for multiple sclerosis

Monoclonal antibodies (MAbs) may have great potential as therapies for autoimmune diseases. Their development as treatments for multiple sclerosis (MS) is promising. Partially effective immunomodulatory therapies have been helpful for many MS patients; however, for patients failing these immunomodulatory treatments, MAbs are an important new treatment option. Currently, MAbs are approved by the US Food and Drug Administration for treatment of many conditions, including autoimmune diseases. Four MAbs that have been investigated as potential treatments for MS are reviewed in this article. Of these MAbs, natalizumab is approved for treatment of MS. The other three MAbs (alemtuzumab, rituximab, and daclizumab) are all promising therapies in development for treatment of MS. Adverse effects are relatively mild for these MAbs; however, care in administration and management of these agents is emphasized. Overall, these MAb therapies have great promise in the treatment of MS.

Anti-NMDA-receptor encephalitis: case series and analysis of the effects of antibodies

BACKGROUND

A severe form of encephalitis associated with antibodies against NR1-NR2 heteromers of the NMDA receptor was recently identified. We aimed to analyse the clinical and immunological features of patients with the disorder and examine the effects of antibodies against NMDA receptors in neuronal cultures.

METHODS

We describe the clinical characteristics of 100 patients with encephalitis and NR1-NR2 antibodies. HEK293 cells ectopically expressing single or assembled NR1-NR2 subunits were used to determine the epitope targeted by the antibodies. Antibody titres were measured with ELISA. The effect of antibodies on neuronal cultures was determined by quantitative analysis of NMDA-receptor clusters.

FINDINGS

Median age of patients was 23 years (range 5-76 years); 91 were women. All patients presented with psychiatric symptoms or memory problems; 76 had seizures, 88 unresponsiveness (decreased consciousness), 86 dyskinesias, 69 autonomic instability, and 66 hypoventilation. 58 (59%) of 98 patients for whom results of oncological assessments were available had tumours, most commonly ovarian teratoma. Patients who received early tumour treatment (usually with immunotherapy) had better outcome (p=0.004) and fewer neurological relapses (p=0.009) than the rest of the patients. 75 patients recovered or had mild deficits and 25 had severe deficits or died. Improvement was associated with a decrease of serum antibody titres. The main epitope targeted by the antibodies is in the extracellular N-terminal domain of the NR1 subunit. Patients' antibodies decreased the numbers of cell-surface NMDA receptors and NMDA-receptor clusters in postsynaptic dendrites, an effect that could be reversed by antibody removal.

INTERPRETATION

A well-defined set of clinical characteristics are associated with anti-NMDA-receptor encephalitis. The pathogenesis of the disorder seems to be mediated by antibodies.

B cells and multiple sclerosis

Clonal expansion of B cells and the production of oligoclonal IgG in the brain and cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS) have long been interpreted as circumstantial evidence of the immune-mediated pathogenesis of the disease and suggest a possible infectious cause. Extensive work on intrathecally produced antibodies has not yet clarified whether they are pathogenetically relevant. Irrespective of antibody specificity, however, the processes of antibody synthesis in the CNS of patients with MS are becoming increasingly clear. Likewise, targeting B cells might be therapeutically relevant in MS and other autoimmune diseases that are deemed to be driven predominantly by T cells. Accumulating evidence indicates that in MS, similar to rheumatoid arthritis, B cells aggregate into lymphoid-like structures in the target organ. The process of aggregation is mediated through the expression of lymphoid-homing chemokines. In the brain of a patient with MS, ectopic B-cell follicles preferentially adjoin the pial membrane within the subarachnoid space. Recent findings indicate that substantial numbers of B cells that are infected with Epstein-Barr virus (EBV) accumulate in these intrameningeal follicles and in white matter lesions and are probably the target of a cytotoxic immune response. These findings, which await confirmation, could be an explanation for the continuous B-cell and T-cell activation in MS, but leave open concerns about the possible pathogenicity of autoantibodies. Going beyond the antimyelin-antibody dogma, the above data warrant further work on various B-cell-related mechanisms, including investigation of B-cell effector and regulatory functions, definition of the consistency of CNS colonisation by Epstein-Barr virus-infected B cells, and understanding of the mechanisms that underlie the formation and persistence of tertiary lymphoid tissues in patients with MS and other chronic autoimmune diseases (ectopic follicle syndromes). This work will stimulate new and unconventional ways of reasoning about MS pathogenesis.

Repeated subcutaneous injections of IL12/23 p40 neutralising antibody, ustekinumab, in patients with relapsing-remitting multiple sclerosis: a phase II, double-blind, placebo-controlled, randomised, dose-ranging study

BACKGROUND

Repeated subcutaneous injections of a monoclonal antibody against the p40 subunit of interleukins 12 and 23, ustekinumab, were used to treat patients with relapsing-remitting multiple sclerosis (RRMS) to assess the drug's safety, efficacy, and pharmacokinetics.

METHODS

In this phase II, multicentre, randomised, double-blind, placebo-controlled study, 249 patients with RRMS, aged 18-65 years, were eligible to be assigned equally (by a central randomisation procedure based on study site and presence or absence of gadolinium-enhancing T1-weighted lesions at baseline) to one of five groups that received placebo or four different ustekinumab dosages at weeks 0, 1, 2, 3, 7, 11, 15, and 19. Ustekinumab doses were 27 mg, 90 mg q8w, 90 mg, or 180 mg; the 90 mg q8w dosage group received placebo substitute at weeks 7 and 15. The primary endpoint was the cumulative number of new gadolinium-enhancing T1-weighted lesions on serial cranial MRI through week 23. Patients were followed up through week 37. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00207727.

FINDINGS

From August, 2004, to December, 2006, 249 patients underwent randomisation (49 for placebo; 50 for each ustekinumab group). Ustekinumab treatment did not show a significant reduction in the primary endpoint for any dosage groups versus placebo. At week 37, adverse events occurred in 38 (78%) placebo-treated patients and 170 (85%) ustekinumab-treated patients, with infections most commonly reported. Serious adverse events occurred in one (2%) placebo-treated patient and six (3%) ustekinumab-treated patients. Malignant diseases were reported in two patients shortly after the initiation of ustekinumab treatment; both patients were withdrawn from the trial and given appropriate treatment, which resulted in complete remission. No serious infections, cardiovascular events, or exacerbation of demyelinating events occurred. A dose-dependent increase in serum concentrations of ustekinumab was recorded.

INTERPRETATION

Ustekinumab is generally well tolerated but does not show efficacy in reducing the cumulative number of gadolinium-enhancing T1-weighted lesions in multiple sclerosis.

Current and future standards in treatment of myasthenia gravis

Myasthenia gravis (MG) is a prototypic antibody-mediated neurological autoimmune disorder. Herein we characterize modern treatment algorithms that are adapted to disease severity, and introduce the current principles of escalating strategies for MG treatment. In non-thymoma patients younger than about 50 years of age and with generalized weakness, a complete early (but not urgent) thymectomy is considered as state-of-the-art on the basis of circumstantial evidence and expert opinion. In up to 10% of patients, MG is associated with a thymoma (i.e., is of paraneoplastic origin). The best surgical type of procedure is still under debate. Myasthenic crisis is best treated by plasmapheresis, mostly combined with immunoabsorption techniques. Intravenous immunoglobulins are a reasonable alternative, but a shortage in supplies and high prices limit their use. In generalized MG, a wide array of immunosuppressive treatments has been established, although not formally tested in double-blind, prospective trials. With regard to immunosuppression, azathioprine is still the standard baseline treatment, often combined with initial corticosteroids. In rare patients with an inborn hepatic enzyme deficiency of thiomethylation, azathioprine may be substituted by mycophenolate mofetil. Severe cases may benefit from combined immunosuppression with corticosteroids, cyclosporine A, and even with moderate doses of methotrexate or cyclophosphamide. Tacrolimus is under investigation. In refractory cases, immunoablation via high-dose cyclophosphamide followed by trophic factors such as granulocyte colony-stimulating factor has also been suggested. In the future we may face an increased use of novel, B-cell, or T-cell-directed monoclonal antibodies.

[Choice of early and escalation treatment options for multiple sclerosis]

Recent advances in understanding of the immunopathogenesis of multiple sclerosis (MS) have led to the development of new treatment options. To date several immunomodulatory agents have been licensed for the treatment of relapsing-remitting MS. However, some debate remains on the optimal time point for initiating therapy. While there is general consensus on the benefit of an early treatment start, the issues of how to define "early MS" and how to identify patients with a "benign" disease course have not yet been finally addressed. Further open questions include the situations of treatment failure and therapeutic escalation. Here we summarize available data from studies on early treatment with immunomodulatory drugs for a first demyelinating event, also referred to as clinically isolated syndrome. Furthermore, options for the escalation of immunomodulatory therapy will be discussed, e.g. with the recently licensed monoclonal antibody natalizumab.

B cells as therapeutic targets in autoimmune neurological disorders

B cells have a fundamental role in the pathogenesis of various autoimmune neurological disorders, not only as precursors of antibody-producing cells, but also as important regulators of the T-cell activation process through their participation in antigen presentation, cytokine production, and formation of ectopic germinal centers in the intermeningeal spaces. Two B-cell trophic factors-BAFF (B-cell-activating factor) and APRIL (a proliferation-inducing ligand)-and their receptors are strongly upregulated in many immunological disorders of the CNS and PNS, and these molecules contribute to clonal expansion of B cells in situ. The availability of monoclonal antibodies or fusion proteins against B-cell surface molecules and trophic factors provides a rational approach to the treatment of autoimmune neurological diseases. This article reviews the role of B cells in autoimmune neurological disorders and summarizes the experience to date with rituximab, a B-cell-depleting monoclonal antibody against CD20, for the treatment of relapsing-remitting multiple sclerosis, autoimmune neuropathies, neuromyelitis optica, paraneoplastic neurological disorders, myasthenia gravis, and inflammatory myopathies. It is expected that ongoing controlled trials will establish the efficacy and long-term safety profile of anti-B-cell agents in several autoimmune neurological disorders, as well as exploring the possibility of a safe and synergistic effect with other immunosuppressants or immunomodulators.

Role of B cells in systemic lupus erythematosus and rheumatoid arthritis

B cell tolerance to many self-proteins is actively maintained by either purging self-reactive B receptors through clonal deletion and receptor editing, or by functional silencing known as anergy. However, these processes are clearly incomplete as B cell driven autoimmune diseases still occur. The significance of B cells in two such diseases, rheumatoid arthritis and systemic lupus erythematosus, is highlighted by the ameliorative effects of B cell depletion. It remains to be determined, however, whether the key role of the B cell in autoimmune disease is autoantibody production or another antibody-independent function.

Identification and development of new therapeutics for multiple sclerosis

In recent years, large efforts have been undertaken to establish new therapeutic options for the treatment of multiple sclerosis (MS). So far, all of these strategies more or less specifically target subsets of the immune response in MS, including not only activation and expansion of T cells, their circulation and transmigration over the blood-brain barrier but also other cell types such as B cells and probably also natural killer cells. Here, we review available data on the most promising (at present) new therapeutic approaches. These involve the orally available compounds cladribine, FTY720, fumaric-acid esters, laquinimod and teriflunomide in addition to the monoclonal antibodies alemtuzumab, daclizumab, natalizumab and rituximab. After successful completion of Phase III studies, these compounds might have the potential to add to the current therapeutic armentarium especially for relapsing remitting disease courses in the near future, possibly opening the way to a more individualized treatment.

Role of rituximab therapy in glomerulonephritis

B cell depletion with the monoclonal antibody rituximab is attracting increasing attention in systemic lupus erythematosus, vasculitis, and primary glomerulonephritis. Existing, uncontrolled data report high response rates in patients with refractory disease. If supported by the results of ongoing randomized trials, then rituximab and related B cell-depleting or -modulating drugs are likely to become a component in the future management of these disorders. Their use may improve patient outcomes by permitting more complete disease control and reduced exposure to glucocorticoid and traditional immunosuppressive drugs. The toxicity and infective risk of B cell-targeted agents in renal disease needs to be determined as well as their optimal dosing in combination with conventional agents.

Inhibition of B cell receptor-mediated activation of primary human B cells by coengagement of CD19 and FcgammaRIIb with Fc-engineered antibodies

The humoral immune response requires antigen-specific B cell activation and subsequent terminal differentiation into plasma cells. Engagement of B cell antigen receptor (BCR) on mature B cells activates an intracellular signaling cascade, including calcium mobilization, which leads to cell proliferation and differentiation. Coengagement by immune complex of BCR with the inhibitory Fc receptor FcgammaRIIb, the only IgG receptor expressed on B cells, inhibits B cell activation signals through a negative feedback loop. We now describe antibodies that mimic the inhibitory effects of immune complex by high-affinity coengagement of FcgammaRIIb and the BCR coreceptor complex on human B cells. We engineered the Fc domain of an anti-CD19 antibody to generate variants with up to approximately 430-fold greater affinity to FcgammaRIIb. Relative to native IgG1, the FcgammaRIIb binding-enhanced (IIbE) variants strongly inhibited BCR-induced calcium mobilization and viability in primary human B cells. Inhibitory effects involved phosphorylation of SH2-containing inositol polyphosphate 5-phosphatase (SHIP), which is known to be involved in FcgammaRIIb-induced negative feedback of B cell activation by immune complex. Coengagement of BCR and FcgammaRIIb by IIbE variants also overcame the anti-apoptotic effects of BCR activation. The use of a single antibody to suppress B cell functions by coengagement of BCR and FcgammaRIIb may represent a novel approach in the treatment of B cell-mediated autoimmune diseases.

Autoantibodies and neurodegeneration in multiple sclerosis

Neurodegeneration develops in association with inflammation and demyelination in multiple sclerosis. Available data suggest that the progressive neuroaxonal loss begins in the earliest stages of the disease and underlies the accumulation of clinical disability. The loss of neurons and their processes is driven by a complex molecular mechanism involving cellular and humoral immune histotoxicity, demyelination, reduced neurotrophic support, metabolic impairment, and altered intracellular processes. Here we survey available data concerning the role of autoreactive immunoglobulins in neurotoxicity. A better understanding of molecular pathways leading to immune-mediated neurodegeneration may have key importance in the successful treatment of the disease.

Getting specific: monoclonal antibodies in multiple sclerosis

For more than a decade the only therapies that were available for multiple sclerosis (MS) were two immunomodulatory drugs-interferon beta and glatiramer acetate-and the immunosuppressant mitoxantrone. Natalizumab, a monoclonal antibody against alpha4 integrin, has been approved by the US Food and Drug Administration and the European Medicines Agency on the basis of its higher efficacy than the available treatments and its good safety profile. Monoclonal antibodies that are already licensed to treat other diseases, such as cancer and autoimmune diseases, are being tested for the treatment of MS. Additionally, novel targets are currently being investigated for MS. The therapeutic use of monoclonal antibodies was initially viewed with great scepticism owing to the high rates of sensitisation against mouse proteins, their pharmacokinetic properties, and the difficulties in their production. However, most of these problems have been overcome, and monoclonal antibodies are now among the most promising therapies for MS.

Early relapses after the first dose of natalizumab in active multiple sclerosis patients

Background

Natalizumab is prescribed in Italy in patients who experienced at least two clinical relapses during a 12-month therapy with other approved immunomodulatory agents.

Results

In 7 of 35 patients selected on the basis of these recommendations, we have observed clinical relapses occurring within 24 h after the first dose of natalizumab.

Conclusion

The mechanism by which a first injection of natalizumab may precipitate a clinical relapse in patients with MS is unknown. We speculate that natalizumab can promote the release of inflammatory mediators from lymphocytes present in the central nervous system at the time of the first infusion, thus favoring the clinical manifestation of a pre-existing active lesion.

A regulatory B cell subset with a unique CD1dhiCD5+ phenotype controls T cell-dependent inflammatory responses

B cells mediate multiple functions that influence immune and inflammatory responses. In this study, T cell-mediated inflammation was exaggerated in CD19-deficient (Cd19(-/-)) mice and wild-type mice depleted of CD20(+) B cells, whereas inflammation was substantially reduced in mice with hyperactive B cells as a result of CD19 overexpression (hCD19Tg). These inflammatory responses were negatively regulated by a unique CD1d(hi)CD5(+) B cell subset that was absent in Cd19(-/-) mice, represented only 1%-2% of spleen B220(+) cells in wild-type mice, but was expanded to approximately 10% of spleen B220(+) cells in hCD19Tg mice. Adoptive transfer of these CD1d(hi)CD5(+) B cells normalized inflammation in wild-type mice depleted of CD20(+) B cells and in Cd19(-/-) mice. Remarkably, IL-10 production was restricted to this CD1d(hi)CD5(+) B cell subset, with IL-10 production diminished in Cd19(-/-) mice, yet increased in hCD19Tg mice. Thereby, CD1d(hi)CD5(+) B cells represent a unique subset of potent regulatory B cells.

Cerebrospinal fluid B cells correlate with early brain inflammation in multiple sclerosis

BACKGROUND

There is accumulating evidence from immunological, pathological and therapeutic studies that B cells are key components in the pathophysiology of multiple sclerosis (MS).

METHODOLOGY/PRINCIPAL FINDINGS

In this prospective study we have for the first time investigated the differences in the inflammatory response between relapsing and progressive MS by comparing cerebrospinal fluid (CSF) cell profiles from patients at the onset of the disease (clinically isolated syndrome, CIS), relapsing-remitting (RR) and chronic progressive (CP) MS by flow cytometry. As controls we have used patients with other neurological diseases. We have found a statistically significant accumulation of CSF mature B cells (CD19+CD138-) and plasma blasts (CD19+CD138+) in CIS and RRMS. Both B cell populations were, however, not significantly increased in CPMS. Further, this accumulation of B cells correlated with acute brain inflammation measured by magnetic resonance imaging and with inflammatory CSF parameters such as the number of CSF leukocytes, intrathecal immunoglobulin M and G synthesis and intrathecal production of matrix metalloproteinase (MMP)-9 and the B cell chemokine CxCL-13.

CONCLUSIONS

Our data support an important role of CSF B cells in acute brain inflammation in CIS and RRMS.

Not always the bad guys: B cells as regulators of autoimmune pathology

When B cells react aggressively against self, the potential for pathology is extreme. It is therefore not surprising that B-cell depletion is seen as an attractive therapy in autoimmune diseases. However, B cells can also be essential for restraining unwanted autoaggressive T-cell responses. Recent advances have pointed to interleukin-10 (IL-10) production as a key component in B-cell-mediated immune regulation. In this Opinion article, we develop a hypothesis that triggering of Toll-like receptors controls the propensity of B cells for IL-10 production and immune suppression. According to this model, B cells can translate exposure to certain microbial infections into protection from chronic inflammatory diseases.

The genetics of multiple sclerosis: SNPs to pathways to pathogenesis

Multiple sclerosis (MS) is an autoimmune demyelinating disease and a common cause of neurological disability in young adults. The modest heritability of MS reflects complex genetic effects and multifaceted gene-environment interactions. The human leukocyte antigen (HLA) region is the strongest susceptibility locus for MS, but a genome-wide association study recently identified new susceptibility genes. Progress in high-throughput genotyping and sequencing technologies and a better understanding of the structural organization of the human genome, together with powerful brain-imaging techniques that refine the phenotype, suggest that the tools could finally exist to identify the full set of genes influencing the pathogenesis of MS.

Interferon-beta increases BAFF levels in multiple sclerosis: implications for B cell autoimmunity

B cells are increasingly recognized as major players in multiple sclerosis pathogenesis. The BAFF/APRIL system is crucial for B cell homoeostasis and may drive B cell-dependent autoimmunity. We asked whether this system is affected by Interferon (IFN)-beta therapy. We analysed transcription of the ligands (BAFF, APRIL, TWE-PRIL) and the corresponding receptors (BAFF-R, TACI and BCMA) by TaqMan-PCR ex vivo in whole blood and in immune cell subsets purified from IFN-beta-treated multiple sclerosis patients. Serum BAFF concentrations were determined by ELISA. This cross-sectional study involved 107 donors. IFN-beta therapy strongly induced BAFF transcription proportionally to the IFN-beta biomarker MxA in monocytes and granulocytes in vivo. BAFF serum concentrations were elevated in IFN-beta-treated multiple sclerosis patients to a similar level as observed in SLE patients. In cultured PBMC, neutrophils, fibroblasts and astrocytes, BAFF was induced by IFN-beta concentrations similar to those reached in vivo in treated multiple sclerosis patients. BAFF turned out to be the main regulated element of the BAFF/APRIL system. In untreated multiple sclerosis patients, there was no BAFF increase as compared to healthy controls. Our study reveals a complex situation. We show that IFN-beta therapy induces a potent B cell survival factor, BAFF. However, B cell depletion would be desirable at least in some multiple sclerosis patients. The systemic induction of BAFF by IFN-beta therapy may facilitate the production of various autoantibodies and of IFN-neutralizing antibodies. Individual MS/NMO patients who have major B cell involvement may benefit less than others from IFN-beta therapy, thus explaining interindividual differences of the therapeutic response.

The immunogenetics of multiple sclerosis

The discoveries in the 1970s of strong associations between various diseases and certain human leukocyte antigen (HLA) factors were a revolution within genetic epidemiology in the last century by demonstrating for the first time how genetic markers can help unravel the genetics of disorders with complex genetic backgrounds. HLA controls immune response genes and HLA associations indicate the involvement of autoimmunity. Multiple sclerosis (MS) was one of the first conditions proven to be HLA associated involving primarily HLA class II factors. We review how HLA studies give fundamental information on the genetics of the susceptibility to MS, on the importance of linkage disequilibrium in association studies, and on the pathogenesis of MS. The HLA-DRB1*1501 molecule may explain about 50% of MS cases and its role in the pathogenesis is supported by studies of transgenic mice. Studies of polymorphic non-HLA genetic markers are discussed based on linkage studies and candidate gene approaches including complete genome scans. No other markers have so far rivaled the importance of HLA in the genetic susceptibility to MS. Recently, large international collaborations provided strong evidence for the involvement of polymorphism of two cytokine receptor genes in the pathogenesis of MS: the interleukin 7 receptor alpha chain gene (IL7RA) on chromosome 5p13 and the interleukin 2 receptor alpha chain gene (IL2RA (=CD25)) on chromosome 10p15. It is estimated that the C allele of a single nucleotide polymorphism, rs6897932, within the alternative spliced exon 6 of IL7RA is involved in about 30% of MS cases.

Perspectives in pharmacological management of Graves' hyperthyroidism and orbitopathy

Drugs currently used for Graves' hyperthyroidism (thionamides) or for the major extrathyroidal expression of Graves' disease, Graves' orbitopathy (systemic glucocorticoids with or without orbital radiotherapy), have limited effects on the autoimmune processes underpinning these disorders. Thionamides show a high rate of treatment failure and at least 30% of patients with Graves' orbitopathy are eventually dissatisfied with treatment outcome. Progress in our understanding of the autoimmune basis of Graves' hyperthyroidism and orbitopathy made it possible, similar to other autoimmune disorders, to envision the use of novel immunomodulating drugs. Among the currently available biologic agents, the CD20(+) B-cell-depleting agent, rituximab, and TNF-alpha inhibitors are the drugs that have the highest chance of finding a place in the treatment of Graves' hyperthyroidism and orbitopathy, although randomized, controlled clinical trials are warranted to support their use.

Rituximab in relapsing-remitting multiple sclerosis: a 72-week, open-label, phase I trial

We evaluated the safety, tolerability, pharmacodynamics, and activity of B-cell depletion with rituximab in patients with relapsing-remitting multiple sclerosis, receiving two courses of rituximab 6 months apart, and followed for a total of 72 weeks. No serious adverse events were noted; events were limited to mild-to-moderate infusion-associated events, which tended to decrease with subsequent infusions. Infections were also mild or moderate, and none led to withdrawal. Fewer new gadolinium-enhancing or T2 lesions were seen starting from week 4 and through week 72. An apparent reduction in relapses was also observed over the 72 weeks compared with the year before therapy.

B cells and autoantibodies in the pathogenesis of multiple sclerosis and related inflammatory demyelinating diseases

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). The mainstream view is that MS is caused by an autoimmune attack of the CNS myelin by myelin-specific CD4 T cells, and this perspective is supported by extensive work in the experimental autoimmune encephalomyelitis (EAE) model of MS as well as immunological and genetic studies in humans. However, it is important to keep in mind that other cell populations of the immune system are also essential in the complex series of events leading to MS, as exemplified by the profound clinical efficacy of B cell depletion with Rituximab. This review discusses the mechanisms by which B cells contribute to the pathogenesis of MS and dissects their role as antigen-presenting cells (APCs) to T cells with matching antigen specificity, the production of proinflammatory cytokines and chemokines, as well as the secretion of autoantibodies that target structures on the myelin sheath and the axon. Mechanistic dissection of the interplay between T cells and B cells in MS may permit the development of B cell based therapies that do not require depletion of this important cell population.