Influence of the Gut Microbiome on Autoimmunity in the Central Nervous System.

Autoimmune disorders of the CNS have complex pathogeneses that are not well understood. In multiple sclerosis and neuromyelitis optica spectrum disorders, T cells destroy CNS tissue, resulting in severe disabilities. Mounting evidence suggests that reducing inflammation in the CNS may start with modulation of the gut microbiome. The lymphoid tissues of the gut are specialized for the induction of regulatory cells, which are directly responsible for the suppression of CNS-damaging autoreactive T cells. Whether cause or effect, the onset of dysbiosis in the gut of patients with multiple sclerosis and neuromyelitis optica provides evidence of communication along the gut-brain axis. Thus, current and future therapeutic interventions directed at microbiome modulation are of considerable appeal.

The role of microbiome in central nervous system disorders.

Mammals live in a co-evolutionary association with the plethora of microorganisms that reside at a variety of tissue microenvironments. The microbiome represents the collective genomes of these co-existing microorganisms, which is shaped by host factors such as genetics and nutrients but in turn is able to influence host biology in health and disease. Niche-specific microbiome, prominently the gut microbiome, has the capacity to effect both local and distal sites within the host. The gut microbiome has played a crucial role in the bidirectional gut-brain axis that integrates the gut and central nervous system (CNS) activities, and thus the concept of microbiome-gut-brain axis is emerging. Studies are revealing how diverse forms of neuro-immune and neuro-psychiatric disorders are correlated with or modulated by variations of microbiome, microbiota-derived products and exogenous antibiotics and probiotics. The microbiome poises the peripheral immune homeostasis and predisposes host susceptibility to CNS autoimmune diseases such as multiple sclerosis. Neural, endocrine and metabolic mechanisms are also critical mediators of the microbiome-CNS signaling, which are more involved in neuro-psychiatric disorders such as autism, depression, anxiety, stress. Research on the role of microbiome in CNS disorders deepens our academic knowledge about host-microbiome commensalism in central regulation and in practicality, holds conceivable promise for developing novel prognostic and therapeutic avenues for CNS disorders.

Digesting the emerging role for the gut microbiome in central nervous system demyelination.

The fields of microbiology, immunology, neurology and nutrition are rapidly converging, as advanced sequencing and genomics-based methodologies have enabled the mapping out of the microbial diversity of humans for the first time. Bugs, guts, brains and behavior were once believed to be separate domains of clinical practice and research; however, recent observations in our understanding of the microbiome indicate that the boundaries between domains are becoming permeable. This permeability is multidirectional: Biological systems are operating simultaneously in a vastly complex and interconnected web. Understanding the microbiome-gut-brain axis will entail fleshing out the mechanisms by which transduction across each domain occurs, allowing us ultimately to appreciate the role of commensal organisms in shaping and modulating host immunity. This article will highlight animal and human research to date, as well as highlight directions for future research. We speculate that the gut microbiome is potentially the premier environmental risk factor mediating inflammatory central nervous system demyelination, in particular multiple sclerosis.

Evaluation of the adjuvant effect of pidotimod on the immune protection induced by UV-attenuated Toxoplasma gondii in mouse models.

The current anti-Toxoplasma gondii drugs have many shortcomings and effective vaccines against T. gondii may contribute to the control of this pathogen. Pidotimod is a synthetic substance capable of stimulating both cellular and humoral immunity. To investigate the possible adjuvant effect of pidotimod on the immune response to T. gondii in Kunming mice induced by ultraviolet-attenuated T. gondii (UV-T.g), in this study, mice were immunized intraperitoneal (i.p.) with UV-T.g or UV-T.g co-administered with pidotimod (UV-T.g + PT). After infection or challenge by i.p. injection of 10(2) RH tachyzoites, the animal survival rate, parasite burden in peritoneal lavage fluids, liver histopathology, the level of serum anti-toxoplasma IgG antibody, and the mRNA expressions of IL-2, IFN-γ, and TNF-α from spleen analyzed using real-time PCR, were compared among different groups. The results showed that, compared with infected controls, infected mice treated with pidotimod had significantly increased survival rate and extended survival time, decreased parasite burden, improved liver histopathology, increased level of anti-toxoplasma IgG antibody, and increased mRNA expressions of Th1-type cytokine (IL-2, IFN-γ, and TNF-α) (P < 0.01), while mice vaccinated with UV-T.g and then challenged had even significantly increased survival rate and extended survival time, decreased parasite burden, improved liver histopathology, and increased mRNA expressions of Th1-type cytokines (IL-2, IFN-γ, and TNF-α) (P < 0.01); furthermore, vaccinated mice co-administered with pidotimod had even more lower parasite burden, milder liver histopathology, and higher levels of Th1-type cytokine and anti-toxoplasma IgG antibody (P < 0.01). Our data demonstrated that pidotimod in vivo could promote strong and specific humoral and cellular immune response to T. gondii challenge infection when co-administered with UV-attenuated T. gondii. It suggests that pidotimod may have the potential to be used as an effective vaccine adjuvant.

Upregulated expression of Tim-3 involved in the process of toxoplasmic encephalitis in mouse model.

Toxoplasma gondii can establish chronic infection and is characterized by the formation of tissue cysts in the brain. The cysts may remain throughout the life of the host but can reactivate and cause life-threatening toxoplasmic encephalitis (TE) in immunocompromised patients. T cell-mediated immune responses are essential for preventing the reactivation of chronic infection of T. gondii in the brain. The immunoinhibitory receptor T cell immunoglobulin and mucin domain (Tim)-1 and Tim-3 are expressed on terminally differentiated T helper (Th) 2 and Th1 cells, respectively, participating in the regulation of Th immune response. However, there is no report concerning the role of Tim genes in TE. In this study, Kunming outbred mice were infected with Prugniaud (Pru), a type II strain of T. gondii by oral gavage. Compared with the uninfected controls, there were mild brain inflammations at 3 weeks postinfection (p.i.), moderate brain inflammations at 5 weeks p.i., and aggravated brain inflammations and necrosis at 7 and 9 weeks p.i. The expressions of tachyzoite stage-specific genes in brains were consistent with the severity of brain histopathology of TE at 5 and 7 weeks p.i., while the expressions of bradyzoite stage-specific genes in brains were significantly increased at 7 and 9 weeks p.i. Using quantitative real-time PCR detection and immunohistochemistry staining, our results showed that the expressions of Tim-3 were significantly upregulated in both brains and spleens at 5 weeks p.i. and in spleens at 9 weeks p.i., which showed the similar dynamic tendency as that of interferon-γ expressions in both brains and spleens at the same times. In contrast, the Th2-specific marker Tim-1 expressions were significantly downregulated in both brains and spleens at 3 weeks p.i. and upregulated in both brains and spleens at 7 and 9 weeks p.i., which showed the similar dynamic tendency as that of interleukin-4 expressions in both brains and spleens at the same time. Our data indicate that Tim-3 may involve in the process of TE in mice infected with T. gondii Pru strain.

Gut, bugs, and brain: role of commensal bacteria in the control of central nervous system disease.

The mammalian gastrointestinal track harbors a highly heterogeneous population of microbial organisms that are essential for the complete development of the immune system. The gut microbes or "microbiota," coupled with host genetics, determine the development of both local microbial populations and the immune system to create a complex balance recently termed the "microbiome." Alterations of the gut microbiome may lead to dysregulation of immune responses both in the gut and in distal effector immune sites such as the central nervous system (CNS). Recent findings in experimental autoimmune encephalomyelitis, an animal model of human multiple sclerosis, suggest that altering certain bacterial populations present in the gut can lead to a proinflammatory condition that may result in the development of autoimmune diseases, in particular human multiple sclerosis. In contrast, other commensal bacteria and their antigenic products, when presented in the correct context, can protect against inflammation within the CNS.

Central nervous system demyelinating disease protection by the human commensal Bacteroides fragilis depends on polysaccharide A expression.

The importance of gut commensal bacteria in maintaining immune homeostasis is increasingly understood. We recently described that alteration of the gut microflora can affect a population of Foxp3(+)T(reg) cells that regulate demyelination in experimental autoimmune encephalomyelitis (EAE), the experimental model of human multiple sclerosis. We now extend our previous observations on the role of commensal bacteria in CNS demyelination, and we demonstrate that Bacteroides fragilis producing a bacterial capsular polysaccharide Ag can protect against EAE. Recolonization with wild type B. fragilis maintained resistance to EAE, whereas reconstitution with polysaccharide A-deficient B. fragilis restored EAE susceptibility. Enhanced numbers of Foxp3(+)T(reg) cells in the cervical lymph nodes were observed after intestinal recolonization with either strain of B. fragilis. Ex vivo, CD4(+)T cells obtained from mice reconstituted with wild type B. fragilis had significantly enhanced rates of conversion into IL-10-producing Foxp3(+)T(reg) cells and offered greater protection against disease. Our results suggest an important role for commensal bacterial Ags, in particular B. fragilis expressing polysaccharide A, in protecting against CNS demyelination in EAE and perhaps human multiple sclerosis.

TLR9-dependent induction of intestinal alpha-defensins by Toxoplasma gondii.

Alpha-defensins (or Cryptdins [Crps]) are a group of antimicrobial peptides produced as a component of Paneth cell (PC) secretory granules in the small intestine. In vivo ligation of TLR9 by synthetic agonists leads to PC degranulation, although the mechanism by which this occurs remains uncertain. In this report, we investigated TLR9-dependent mechanisms, triggered by the parasite Toxoplasma gondii, inducing Crp release in the lumen. Oral challenge of C57BL/6J (B6) wild-type (WT) mice with T. gondii induced TLR9 mRNA upregulation associated with a marked increase of type I IFN mRNA expression. PC secretory granules were released, and Crp-3/-5 mRNA expression by purified epithelial cells was increased following oral challenge of B6 WT mice. Although PCs failed to degranulate in infected B6 TLR9-/- mice, i.p. injection of mouse IFN-beta alone led to Crp-3/-5 mRNA upregulation in B6 WT and TLR9-/- mice. In addition, modulation of Crp mRNA expression in response to T. gondii infection was abrogated in B6 IFNAR-/- mice, which lack a functional type I IFN receptor. Taken together, these data demonstrate that T. gondii induces Crp-3/-5 production and release by PCs via a TLR9-dependent production of type I IFNs. Crps have a limited direct effect against T. gondii but may indirectly affect the early control of T. gondii invasiveness by promoting the initiation of a protective Th1 response against the parasite.

Cryopreservation of Toxoplasma gondii in infected murine tissues.

Laboratory maintenance of the RH strain of Toxoplasma gondii is generally done by passage in mice, in vitro propagation in fibroblasts, or cryopreservation of peritoneal exudates from mice infected with T. gondii. To explore alternative techniques for preserving laboratory T. gondii tachyzoites, we propose a new method of freezing tissues from infected mice. The effect of storage of T. gondii tissue tachyzoites in two different cryoprotectant combinations and at two different temperatures was studied. The liver and spleen tissues, and peritoneal exudates from mice infected with RH-GFP strain of T. gondii, suspended in RPMI 1640 medium supplemented with 12 % glycerol plus 20 % calf serum, or 12 % dimethyl sulfoxide (DMSO) plus 20 % calf serum, were stored for 3 months at -20 °C in an ordinary refrigerator or at -80 °C in a deep freezer, respectively. The viability of tissue T. gondii tachyzoites was determined by animal inoculation method, which was assessed by monitoring survival and tissue parasitemia in recipient mice. Our data showed that toxoplasma tachyzoites in the above tissues remained viable after cryopreservation in 12 % DMSO plus 20 % calf serum at -80 °C, the infectivity of tachyzoites from the tissues and peritoneal fluids was demonstrated in inoculated murine tissues. Our data indicate that freezing infected murine tissues at -80 °C provides a simple and appropriate method for preservation of T. gondii tachyzoites in laboratory without the need for costly liquid nitrogen preservation procedures.

Role of gut commensal microflora in the development of experimental autoimmune encephalomyelitis.

Mucosal tolerance has been considered a potentially important pathway for the treatment of autoimmune disease, including human multiple sclerosis and experimental conditions such as experimental autoimmune encephalomyelitis (EAE). There is limited information on the capacity of commensal gut bacteria to induce and maintain peripheral immune tolerance. Inbred SJL and C57BL/6 mice were treated orally with a broad spectrum of antibiotics to reduce gut microflora. Reduction of gut commensal bacteria impaired the development of EAE. Intraperitoneal antibiotic-treated mice showed no significant decline in the gut microflora and developed EAE similar to untreated mice, suggesting that reduction in disease activity was related to alterations in the gut bacterial population. Protection was associated with a reduction of proinflammatory cytokines and increases in IL-10 and IL-13. Adoptive transfer of low numbers of IL-10-producing CD25(+)CD4(+) T cells (>75% FoxP3(+)) purified from cervical lymph nodes of commensal bacteria reduced mice and in vivo neutralization of CD25(+) cells suggested the role of regulatory T cells maintaining peripheral immune homeostasis. Our data demonstrate that antibiotic modification of gut commensal bacteria can modulate peripheral immune tolerance that can protect against EAE. This approach may offer a new therapeutic paradigm in the treatment of multiple sclerosis and perhaps other autoimmune conditions.

Exploring the Gut-Brain Axis for the Control of CNS Inflammatory Demyelination: Immunomodulation by Bacteroides fragilis' Polysaccharide A.

The symbiotic relationship between animals and their resident microorganisms has profound effects on host immunity. The human microbiota comprises bacteria that reside in the gastrointestinal tract and are involved in a range of inflammatory and autoimmune diseases. The gut microbiota's immunomodulatory effects extend to extraintestinal tissues, including the central nervous system (CNS). Specific symbiotic antigens responsible for inducing immunoregulation have been isolated from different bacterial species. Polysaccharide A (PSA) of Bacteroides fragilis is an archetypical molecule for host-microbiota interactions. Studies have shown that PSA has beneficial effects in experimental disease models, including experimental autoimmune encephalomyelitis (EAE), the most widely used animal model for multiple sclerosis (MS). Furthermore, in vitro stimulation with PSA promotes an immunomodulatory phenotype in human T cells isolated from healthy and MS donors. In this review, we discuss the current understanding of the interactions between gut microbiota and the host in the context of CNS inflammatory demyelination, the immunomodulatory roles of gut symbionts. More specifically, we also discuss the immunomodulatory effects of B. fragilis PSA in the gut-brain axis and its therapeutic potential in MS. Elucidation of the molecular mechanisms responsible for the microbiota's impact on host physiology offers tremendous promise for discovering new therapies.

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.

A Gut Feeling: The Importance of the Intestinal Microbiota in Psychiatric Disorders.

The intestinal microbiota constitutes a complex ecosystem in constant reciprocal interactions with the immune, neuroendocrine, and neural systems of the host. Recent molecular technological advances allow for the exploration of this living organ and better facilitates our understanding of the biological importance of intestinal microbes in health and disease. Clinical and experimental studies demonstrate that intestinal microbes may be intimately involved in the progression of diseases of the central nervous system (CNS), including those of affective and psychiatric nature. Gut microbes regulate neuroinflammatory processes, play a role in balancing the concentrations of neurotransmitters and could provide beneficial effects against neurodegeneration. In this review, we explore some of these reciprocal interactions between gut microbes and the CNS during experimental disease and suggest that therapeutic approaches impacting the gut-brain axis may represent the next avenue for the treatment of psychiatric disorders.

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.

Apoptosis in Toxoplasma gondii activated T cells: the role of IFNgamma in enhanced alteration of Bcl-2 expression and mitochondrial membrane potential.

In the present study we addressed the question whether Toxoplasma gondii could promote apoptosis in T lymphocytes in the acute stage of infection. Using in vivo activated T cells and then culturing them for a short time, we observed activation-induced cell death in T. gondii infected mice. A higher level of activation-induced cell death (AICD) was seen in susceptible C57BL/6 mice than in resistant CBA/J mice following infection with the same P strain of parasite. Apoptosis in T cells of susceptible mice was associated with altered induction of Bcl-2/Bax, loss of Mitochondrial Transmembrane Potential. Both CD4+ and CD8+ T cells were found to be susceptible to apoptosis; CD4+ T cells were sensitive to Fas-mediated death whereas CD8+ T cells were insensitive to this signal. Caspase inhibitors had less effect on DNA fragmentation in CD4+ compared to CD8+ T cells. Exposure of CD4+ T cells to anti-IFNgamma mAb resulted in an increase in the number of T cells that were positive for anti-apoptotic molecule Bcl-2 and DiOC6, a cationic dye that accumulates in intact mitochondria. These changes were less noticeable in CD8+ T cells following treatment with anti-IFNgamma mAb. These findings provide further insight into the mechanisms of T cell apoptosis in T. gondii infection.

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.

Downregulation of IL-17 and IL-6 in the central nervous system by glatiramer acetate in experimental autoimmune encephalomyelitis.

T helper 17 (Th17) cells are pivotal in the immune pathogenesis of EAE. Glatiramer acetate (GA) can enhance Treg FOXp3 expression. We demonstrate that GA downregulates the expression of both IL-17 and IL-6 in two different EAE models. Increased mRNA expression in CNS for ROR gamma t, IL-17, IL-12/IL-23, IL-6, TNF-alpha, STAT4 and Th1 cytokines were significantly reduced by GA with a concomitant rise in SMAD3. The increased expression of TNF-alpha, IL-6, and IL-17 in CNS of CD25+ depleted animals was suppressed by GA treatment. This study demonstrates that both Th1 polarization and Th17 expression are modulated by GA.

The Gut Microbiome and Multiple Sclerosis.

The microbiome can be defined as the sum of the microbial and host's genome. Recent information regarding this complex organ suggests that in animal models of multiple sclerosis (MS), the composition of the gut microbiome can be altered, giving rise to both the effector and regulatory phases of central nervous system (CNS) demyelination. Experimental findings during the past decade in animal models of MS have provided clear evidence for the significant role of gut microbes in both the effector and regulatory phase of this condition. There is mounting evidence in preliminary human studies suggesting that a dysbiotic MS gut microbiome could affect disease progression. We propose considering the gut microbiome as a key organ for the regulation of tolerance mechanisms and speculate that the gut microbiome is the major environmental risk factor for CNS demyelinating disease. Accordingly, we hypothesize that intervention of the gut microbiome could result in safer novel therapeutic strategies to treat MS.

Confronting potential influenza A (H5N1) pandemic with better vaccines.

Influenza A (H5N1) viruses are strong candidates for causing the next influenza pandemic if they acquire the ability for efficient human-to-human transmission. A major public health goal is to make efficacious vaccines against these viruses by using novel approaches, including cell-culture system, reverse genetics, and adjuvant development. Important consideration for the strategy includes preparation of vaccines from a currently circulating strain to induce broad-spectrum immunity toward newly emerged human H5 strains. This strategy would be a good solution early in a pandemic until an antigenically matched and approved vaccine is produced. The concept of therapeutic vaccines (e.g., antidisease vaccine) directed at diminishing the cytokine storm frequently seen in subtype H5N1-infected persons is underscored. Better understanding of host-virus interaction is essential to identify tools to produce effective vaccines against influenza (H5N1).

The influence of gut-derived CD39 regulatory T cells in CNS demyelinating disease.

There is considerable interest in trying to understand the importance of the gut microbiome in human diseases. The association between dysbiosis, an altered microbial composition, as related to human disease is being explored in the context of different autoimmune conditions, including multiple sclerosis (MS). Recent studies suggest that MS affects the composition of the gut microbiota by altering the relative abundances of specific bacteria and archaea species. Remarkably, some of the bacterial species shown reduced in the gut of MS patients are known to promote immunosuppressive regulatory T cells (Tregs). In MS, the function of a phenotype of Tregs that express CD39, an ectoenzyme involved in the catabolism of adenosine triphosphate as immunomodulatory cells, appears to be reduced. In this review, we discuss the involvement of the gut microbiota in the regulation of experimental models of central nervous system inflammatory demyelination and review the evidence that link the gut microbiome with MS. Further, we hypothesize that the gut microbiome is an essential organ for the control of tolerance in MS patients and a potential source for safer novel therapeutics.