Isolation of myelin basic protein-specific T cells predominantly from the memory T-cell compartment in multiple sclerosis

Vitamin D as a Risk Factor for Multiple Sclerosis: Immunoregulatory or Neuroprotective?

Vitamin D insufficiency during childhood has been linked to the development of multiple sclerosis (MS), typically an adult-onset inflammatory demyelinating disease of the central nervous system (CNS). Since vitamin D was known to have immunoregulatory properties on both innate and adaptive immunity, it was hypothesized that low vitamin D resulted in aberrant immune responses and the development of MS. However, vitamin D receptors are present on many cell types, including neurons, oligodendrocytes, astrocytes and microglia, and vitamin D has profound effects on development and function of the CNS. This leads to the possibility that low vitamin D may alter the CNS in a manner that makes it vulnerable to inflammation and the development of MS. This review analysis the role of vitamin D in the immune and nervous system, and how vitamin D insufficiency in children may contribute to the development of MS.

Molecular characterization of hypoxanthine guanine phosphoribosyltransferase mutant T cells in human blood: The concept of surrogate selection for immunologically relevant cells

Somatic cell gene mutations arise in vivo due to replication errors during DNA synthesis occurring spontaneously during normal DNA synthesis or as a result of replication on a DNA template damaged by endogenous or exogenous mutagens. In principle, changes in the frequencies of mutant cells in vivo in humans reflect changes in exposures to exogenous or endogenous DNA damaging insults, other factors being equal. It is becoming increasingly evident however, that somatic mutations in humans have a far greater range of interpretations. For example, mutations in lymphocytes provide invaluable probes for in vivo cellular and molecular processes, providing identification of clonal amplifications of these cells in autoimmune and infectious diseases, transplantation recipients, paroxysmal nocturnal hemoglobinuria (PNH), and cancer. The assay for mutations of the X-chromosomal hypoxanthine guanine phosphoribosyltransferase (HPRT) gene has gained popular acceptance for this purpose since viable mutant cells can be recovered for molecular and other analyses. Although the major application of the HPRT T cell assay remains human population monitoring, the enrichment of activated T cells in the mutant fraction in individuals with ongoing immunological processes has demonstrated the utility of surrogate selection, a method that uses somatic mutation as a surrogate marker for the in vivo T cell proliferation that underlies immunological processes to investigate clinical disorders with immunological features. Studies encompassing a wide range of clinical conditions are reviewed. Despite the historical importance of the HPRT mutation system in validating surrogate selection, there are now additional mutational and other methods for identifying immunologically active T cells. These methods are reviewed and provide insights for strategies to extend surrogate selection in future studies.

Superoxide Dismutase-1 Intracellular Content in T Lymphocytes Associates with Increased Regulatory T Cell Level in Multiple Sclerosis Subjects Undergoing Immune-Modulating Treatment

Reactive oxygen species (ROS) participate in the T-cell activation processes. ROS-dependent regulatory networks are usually mediated by peroxides, which are more stable and able to freely migrate inside cells. Superoxide dismutase (SOD)-1 represents the major physiological intracellular source of peroxides. We found that antigen-dependent activation represents a triggering element for SOD-1 production and secretion by human T lymphocytes. A deranged T-cell proinflammatory response characterizes the pathogenesis of multiple sclerosis (MS). We previously observed a decreased SOD-1 intracellular content in leukocytes of MS individuals at diagnosis, with increasing amounts of such enzyme after interferon (IFN)-b 1b treatment. Here, we analyzed in depth SOD-1 intracellular content in T cells in a cohort of MS individuals undergoing immune-modulating treatment. Higher amounts of the enzyme were associated with increased availability of regulatory T cells (Treg) preferentially expressing Foxp3-exon 2 (Foxp3-E2), as described for effective Treg. In vitro administration of recombinant human SOD-1 to activated T cells, significantly increased their IL-17 production, while SOD-1 molecules lacking dismutase activity were unable to interfere with cytokine production by activated T cells in vitro. Furthermore, hydrogen peroxide addition was observed to mimic, in vitro, the SOD-1 effect on IL-17 production. These data add SOD-1 to the molecules involved in the molecular pathways contributing to re-shaping the T-cell cytokine profile and Treg differentiation.

Assessment of commonly used methods to determine myelin-reactivity of T cells in multiple sclerosis

Many studies have analyzed myelin-reactivity of T cells in multiple sclerosis (MS); however, with conflicting results. In this study we compare methods to determine myelin reactivity of T cells and aim to delineate the cause of inconsistency in the literature. Challenging T cells with myelin antigens we found a significant increase in antigen-reactivity of T cells from patients with MS using an ELISpot-assay, in contrast to a CFSE-dilution assay. Comparing the two assays showed that the myelin-reactive T cells detected in the ELISpot-assay originated primarily from effector memory T cells in contrast to the myelin-reactive T cells of the CFSE-assay representing a population of both naïve, central memory and effector memory T cells. This diversity in T cell populations activated in the two assays likely contribute to the discrepancy found in the literature and encourages thorough considerations when choosing an assay to determine antigen-specificity of T cells in future studies.

B cell depletion changes the immune cell profile in multiple sclerosis patients: One-year report

B cell depletion therapy has been shown to be beneficial in multiple sclerosis (MS). However, the mechanism by which B cell depletion mediates its beneficial effects in MS is still unclear. To better understand how B cell depletion may benefit patients with a disease previously thought to be primarily mediated by CD4 T cells, immune profiles were monitored in 48 patients in a phase II trial of ublituximab, a glycoengineered CD20 monoclonal antibody, at 18 time points over a year. As we previously described there was a significant shift in the percentages of T cells, NK cells, and myeloid cells following the initial dose of ublituximab, but this shift normalized within a week and these populations remained stable for the duration of the study. However, T cell subsets changed with an increase in the percentage of naïve CD4 and CD8 T cells and a decline in memory T cells. Importantly, the percentage of Th1 and CD4⁺GM-CSF⁺ T cells decreased, while the percentage of Tregs continued to increase over the year. Ublituximab not only depleted CD20⁺ B cells, but also CD20⁺ T cells. The favorable changes in the T cell subsets may contribute to the beneficial effects of B cell depletion therapy.

Ectopic Lymphoid Follicles in Multiple Sclerosis: Centers for Disease Control?

While the contribution of autoreactive CD4⁺ T cells to the pathogenesis of Multiple Sclerosis (MS) is widely accepted, the advent of B cell-depleting monoclonal antibody (mAb) therapies has shed new light on the complex cellular mechanisms underlying MS pathogenesis. Evidence supports the involvement of B cells in both antibody-dependent and -independent capacities. T cell-dependent B cell responses originate and take shape in germinal centers (GCs), specialized microenvironments that regulate B cell activation and subsequent differentiation into antibody-secreting cells (ASCs) or memory B cells, a process for which CD4⁺ T cells, namely follicular T helper (T_FH) cells, are indispensable. ASCs carry out their effector function primarily via secreted Ig but also through the secretion of both pro- and anti-inflammatory cytokines. Memory B cells, in addition to being capable of rapidly differentiating into ASCs, can function as potent antigen-presenting cells (APCs) to cognate memory CD4⁺ T cells. Aberrant B cell responses are prevented, at least in part, by follicular regulatory T (T_FR) cells, which are key suppressors of GC-derived autoreactive B cell responses through the expression of inhibitory receptors and cytokines, such as CTLA4 and IL-10, respectively. Therefore, GCs represent a critical site of peripheral B cell tolerance, and their dysregulation has been implicated in the pathogenesis of several autoimmune diseases. In MS patients, the presence of GC-like leptomeningeal ectopic lymphoid follicles (eLFs) has prompted their investigation as potential sources of pathogenic B and T cell responses. This hypothesis is supported by elevated levels of CXCL13 and circulating T_FH cells in the cerebrospinal fluid (CSF) of MS patients, both of which are required to initiate and maintain GC reactions. Additionally, eLFs in post-mortem MS patient samples are notably devoid of T_FR cells. The ability of GCs to generate and perpetuate, but also regulate autoreactive B and T cell responses driving MS pathology makes them an attractive target for therapeutic intervention. In this review, we will summarize the evidence from both humans and animal models supporting B cells as drivers of MS, the role of GC-like eLFs in the pathogenesis of MS, and mechanisms controlling GC-derived autoreactive B cell responses in MS.

Memory CD4+ T Cells in Immunity and Autoimmune Diseases

CD4⁺ T helper (Th) cells play central roles in immunity in health and disease. While much is known about the effector function of Th cells in combating pathogens and promoting autoimmune diseases, the roles and biology of memory CD4⁺ Th cells are complex and less well understood. In human autoimmune diseases such as multiple sclerosis (MS), there is a critical need to better understand the function and biology of memory T cells. In this review article we summarize current concepts in the field of CD4⁺ T cell memory, including natural history, developmental pathways, subsets, and functions. Furthermore, we discuss advancements in the field of the newly-described CD4⁺ tissue-resident memory T cells and of CD4⁺ memory T cells in autoimmune diseases, two major areas of important unresolved questions in need of answering to advance new vaccine design and development of novel treatments for CD4⁺ T cell-mediated autoimmune diseases.

Impaired Expression of Tetraspanin 32 (TSPAN32) in Memory T Cells of Patients with Multiple Sclerosis

Tetraspanins are a conserved family of proteins involved in a number of biological processes. We have previously shown that Tetraspanin-32 (TSPAN32) is significantly downregulated upon activation of T helper cells via anti-CD3/CD28 stimulation. On the other hand, TSPAN32 is marginally modulated in activated Treg cells. A role for TSPAN32 in controlling the development of autoimmune responses is consistent with our observation that encephalitogenic T cells from myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE) mice exhibit significantly lower levels of TSPAN32 as compared to naïve T cells. In the present study, by making use of ex vivo and in silico analysis, we aimed to better characterize the pathophysiological and diagnostic/prognostic role of TSPAN32 in T cell immunity and in multiple sclerosis (MS). We first show that TSPAN32 is significantly downregulated in memory T cells as compared to naïve T cells, and that it is further diminished upon ex vivo restimulation. Accordingly, following antigenic stimulation, myelin-specific memory T cells from MS patients showed significantly lower expression of TSPAN32 as compared to memory T cells from healthy donors (HD). The expression levels of TSPAN32 was significantly downregulated in peripheral blood mononuclear cells (PBMCs) from drug-naïve MS patients as compared to HD, irrespective of the disease state. Finally, when comparing patients undergoing early relapses in comparison to patients with longer stable disease, moderate but significantly lower levels of TSPAN32 expression were observed in PBMCs from the former group. Our data suggest a role for TSPAN32 in the immune responses underlying the pathophysiology of MS and represent a proof-of-concept for additional studies aiming at dissecting the eventual contribution of TSPAN32 in other autoimmune diseases and its possible use of TSPAN32 as a diagnostic factor and therapeutic target.

Novel small molecule IL-6 inhibitor suppresses autoreactive Th17 development and promotes Treg development

Multiple sclerosis (MS) is the leading cause of non-traumatic neurological disability in the United States in young adults, but current treatments are only partially effective, making it necessary to develop new, innovative therapeutic strategies. Myelin-specific interleukin (IL)-17-producing T helper type 17 (Th17) cells are a major subset of CD4 T effector cells (T_eff ) that play a critical role in mediating the development and progression of MS and its mouse model, experimental autoimmune encephalomyelitis (EAE), while regulatory T cells (T_reg ) CD4 T cells are beneficial for suppressing disease. The IL-6/signal transducer and activator of transcription 3 (STAT-3) signaling pathway is a key regulator of Th17 and T_reg cells by promoting Th17 development and suppressing T_reg development. Here we show that three novel small molecule IL-6 inhibitors, madindoline-5 (MDL-5), MDL-16 and MDL-101, significantly suppress IL-17 production in myelin-specific CD4 T cells in a dose-dependent manner in vitro. MDL-101 showed superior potency in suppressing IL-17 production compared to MDL-5 and MDL-16. Treatment of myelin-specific CD4 T cells with MDL-101 in vitro reduced their encephalitogenic potential following their subsequent adoptive transfer. Furthermore, MDL-101 significantly suppressed proliferation and IL-17 production of anti-CD3-activated effector/memory CD45RO⁺ CD4⁺ human CD4 T cells and promoted human T_reg development. Together, these data demonstrate that these novel small molecule IL-6 inhibitors have the potential to shift the T_eff  : T_reg balance, which may provide a novel therapeutic strategy for ameliorating disease progression in MS.

Distinct roles for Blimp-1 in autoreactive CD4 T cells during priming and effector phase of autoimmune encephalomyelitis

B lymphocyte-induced maturation protein (Blimp-1) is a transcription factor that regulates effector/memory B cells and CD8 T cells. Here we show that Blimp-1 is expressed in both Th1 and Th17 cells in vitro and highly expressed in effector/memory myelin-specific CD4 T cells in experimental autoimmune encephalomyelitis (EAE) mice. The immunized Blimp-1 conditional knockout mice have a significantly delayed disease onset but enhanced disease severity during the effector phase compared to their wild-type littermates, suggesting that Blimp-1 is a unique transcription factor with distinct roles in the regulation of myelin-specific CD4 T cells during priming and effector phase of EAE.

IL-3 Is a Marker of Encephalitogenic T Cells, but Not Essential for CNS Autoimmunity

Identifying molecules that are differentially expressed in encephalitogenic T cells is critical to the development of novel and specific therapies for multiple sclerosis (MS). In this study, IL-3 was identified as a molecule highly expressed in encephalitogenic Th1 and Th17 cells, but not in myelin-specific non-encephalitogenic Th1 and Th17 cells. However, B10.PL IL-3-deficient mice remained susceptible to experimental autoimmune encephalomyelitis (EAE), a mouse model of MS. Furthermore, B10.PL myelin-specific T cell receptor transgenic IL-3-/- Th1 and Th17 cells were capable of transferring EAE to wild-type mice. Antibody neutralization of IL-3 produced by encephalitogenic Th1 and Th17 cells failed to alter their ability to transfer EAE. Thus, IL-3 is highly expressed in myelin-specific T cells capable of inducing EAE compared to activated, non-encephalitogenic myelin-specific T cells. However, loss of IL-3 in encephalitogenic T cells does not reduce their pathogenicity, indicating that IL-3 is a marker of encephalitogenic T cells, but not a critical element in their pathogenic capacity.

Effector T Cells in Multiple Sclerosis

Multiple sclerosis (MS) has long been considered a CD4 T-cell disease, primarily because of the findings that the strongest genetic risk for MS is the major histocompatibility complex (MHC) class II locus, and that T cells play a central role in directing the immune response. The importance that the T helper (Th)1 cytokine, interferon γ (IFN-γ), and the Th17 cytokine, interleukin (IL)-17, play in MS pathogenesis is indicated by recent clinical trial data by the enhanced presence of Th1/Th17 cells in central nervous system (CNS) tissue, cerebrospinal fluid (CSF), and blood, and by research on animal models of MS, such as experimental autoimmune encephalomyelitis (EAE). Although the majority of research on MS pathogenesis has centered on the role of effector CD4 T cells, accumulating data suggests that CD8 T cells may play a significant role in the human disease. In fact, in contrast to most animal models, the primary T cell found in the CNS in patients with MS, is the CD8 T cell. As patient-derived effector T cells are also resistant to mechanisms of dominant tolerance such as that induced by interaction with regulatory T cells (Tregs), their reduced response to regulation may also contribute to the unchecked effector T-cell activity in patients with MS. These concepts will be discussed below.

Role of Immunological Memory Cells as a Therapeutic Target in Multiple Sclerosis

Pharmacological targeting of memory cells is an attractive treatment strategy in various autoimmune diseases, such as psoriasis and rheumatoid arthritis. Multiple sclerosis is the most common inflammatory disorder of the central nervous system, characterized by focal immune cell infiltration, activation of microglia and astrocytes, along with progressive damage to myelin sheaths, axons, and neurons. The current review begins with the identification of memory cell types in the previous literature and a recent description of the modulation of these cell types in T, B, and resident memory cells in the presence of different clinically approved multiple sclerosis drugs. Overall, this review paper tries to determine the potential of memory cells to act as a target for the current or newly-developed drugs.

IL-23R-activated STAT3/STAT4 is essential for Th1/Th17-mediated CNS autoimmunity

The factors that promote the differentiation of pathogenic T cells in autoimmune diseases are poorly defined. Use of genetically modified mice has provided insight into molecules necessary for the development of autoimmunity, but the sum of the data has led to contradictory observations based on what is currently known about specific molecules in specific signaling pathways. To define the minimum signals required for development of encephalitogenic T cells that cause CNS autoimmunity, myelin-specific T cells were differentiated with various cytokine cocktails, and pathogenicity was determined by transfer into mice. IL-6+IL-23 or IL-12+IL-23 generated encephalitogenic T cells and recapitulated the essential cytokine signals provided by antigen-presenting cells, and both IL-6 and IL-12 induced IL-23 receptor expression on both mouse and human naive T cells. IL-23 signaled through both STAT3 and STAT4, and disruption in STAT4 signaling impaired CNS autoimmunity independent of IL-12. These data explain why IL-12-deficient mice develop CNS autoimmunity, while STAT4-deficient mice are resistant. CD4+ memory T cells from multiple sclerosis patients had significantly higher levels of p-STAT3/p-STAT4, and p-STAT3/p-STAT4 heterodimers were observed upon IL-23 signaling, suggesting that p-STAT3/p-STAT4 induced by IL-23 signaling orchestrate the generation of pathogenic T cells in CNS autoimmunity, regardless of Th1 or Th17 phenotype.

Multiple Sclerosis and Obesity: Possible Roles of Adipokines

Multiple Sclerosis (MS) is an autoimmune disorder of the Central Nervous System that has been associated with several environmental factors, such as diet and obesity. The possible link between MS and obesity has become more interesting in recent years since the discovery of the remarkable properties of adipose tissue. Once MS is initiated, obesity can contribute to increased disease severity by negatively influencing disease progress and treatment response, but, also, obesity in early life is highly relevant as a susceptibility factor and causally related risk for late MS development. The aim of this review was to discuss recent evidence about the link between obesity, as a chronic inflammatory state, and the pathogenesis of MS as a chronic autoimmune and inflammatory disease. First, we describe the main cells involved in MS pathogenesis, both from neural tissue and from the immune system, and including a new participant, the adipocyte, focusing on their roles in MS. Second, we concentrate on the role of several adipokines that are able to participate in the mediation of the immune response in MS and on the possible cross talk between the latter. Finally, we explore recent therapy that involves the transplantation of adipocyte precursor cells for the treatment of MS.

Role of CD4+ T Cells in the Pathophysiology of Multiple Sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. Although the precise etiology of MS remains unclear, CD4⁺ T cells have been proposed to play not only effector but also regulatory roles in MS. CD4⁺ T cells can be divided into four subsets: pro-inflammatory helper T (Th) 1 and Th17 cells, anti-inflammatory Th2 cells and regulatory T cells (Tregs). The roles of CD4⁺ T cells in MS have been clarified by either “loss-of-function” or “gain-of-function” methods, which have been carried out mainly in autoimmune and viral models of MS: experimental autoimmune encephalomyelitis and Theiler's murine encephalomyelitis virus infection, respectively. Observations in MS patients were consistent with the mechanisms found in the MS models, that is, increased pro-inflammatory Th1 and Th17 activity is associated with disease exacerbation, while anti-inflammatory Th2 cells and Tregs appear to play a protective role.

Is T-bet a potential therapeutic target in multiple sclerosis?

Treatments for multiple sclerosis (MS) have changed over the past years as our understanding of immunology and neuroscience has evolved. Experimental autoimmune encephalomyelitis (EAE) continues to remain the major model for MS and has been a major vehicle in the development of new therapeutic targets for MS, including new agents such as natalizumab, fingolimod, and dimethyl fumarate. As progress in the molecular understanding of immunology continues, many observations in EAE are pursued with the ultimate goal of defining the pathophysiology of MS and development of innovative treatments for the disease. Although many consider MS to be a T cell-mediated autoimmune disease directed against myelin antigens, the exact cause of the disease is still unknown. For many years, it was thought that myelin-specific T cells that secreted interferon-γ and were proinflammatory were the major T cell subset that mediated the disease, but recent studies on the cytokine phenotype of pathogenic T cells in EAE and MS have opened debate on this issue. Work over the past several years suggests that the transcription factor T-bet appears to be an important factor in T cell encephalitogenicity; however, recent data suggest that it is also dispensable in certain situations, particularly for Th17 cells. Understanding the molecular mechanisms responsible for T cell encephalitogenicity in MS and other autoimmune diseases will be essential in the development of specific therapies for these inflammatory diseases.

The experimental autoimmune encephalomyelitis (EAE) model of MS: utility for understanding disease pathophysiology and treatment

While no single model can exactly recapitulate all aspects of multiple sclerosis (MS), animal models are essential in understanding the induction and pathogenesis of the disease and to develop therapeutic strategies that limit disease progression and eventually lead to effective treatments for the human disease. Several different models of MS exist, but by far the best understood and most commonly used is the rodent model of experimental autoimmune encephalomyelitis (EAE). This model is typically induced by either active immunization with myelin-derived proteins or peptides in adjuvant or by passive transfer of activated myelin-specific CD4+ T lymphocytes. Mouse models are most frequently used because of the inbred genotype of laboratory mice, their rapid breeding capacity, the ease of genetic manipulation, and availability of transgenic and knockout mice to facilitate mechanistic studies. Although not all therapeutic strategies for MS have been developed in EAE, all of the current US Food and Drug Administration (FDA)-approved immunomodulatory drugs are effective to some degree in treating EAE, a strong indicator that EAE is an extremely useful model to study potential treatments for MS. Several therapies, such as glatiramer acetate (GA: Copaxone), and natalizumab (Tysabri), were tested first in the mouse model of EAE and then went on to clinical trials. Here we discuss the usefulness of the EAE model in understanding basic disease pathophysiology and developing treatments for MS as well as the potential drawbacks of this model.

Autoimmune T-cell reactivity to myelin proteolipids and glycolipids in multiple sclerosis

Central nervous system (CNS) myelin, the likely major target of autoimmune attack in multiple sclerosis (MS), contains a number of unique components that are potential targets of the attack. Two classes of molecules that are greatly enriched in CNS myelin compared to other parts of the body are certain types of proteolipids and glycolipids. Due to the hydrophobic nature of both of these classes of molecules, they present challenges for use in immunological assays and have therefore been somewhat neglected in studies of T-cell reactivity in MS compared to more soluble molecules such as the myelin basic proteins and the extracellular domain of myelin oligodendrocyte glycoprotein. This review firstly looks at the makeup of CNS myelin, with an emphasis on proteolipids and glycolipids. Next, a retrospective of what is known of T-cell reactivity directed against proteolipids and glycolipids in patients with MS is presented, and the implications of the findings are discussed. Finally, this review considers the question of what would be required to prove a definite role for autoreactivity against proteolipids and glycolipids in the pathogenesis of MS.

HLA-DR15-derived self-peptides are involved in increased autologous T cell proliferation in multiple sclerosis

The HLA-DR15 haplotype confers the largest part of the genetic risk to develop multiple sclerosis, a prototypic CD4+ T cell-mediated autoimmune disease. The mechanisms how certain HLA-class II molecules functionally contribute to autoimmune diseases are still poorly understood, but probably involve shaping an autoimmune-prone T cell repertoire during central tolerance in the thymus and subsequently maintaining or even expanding it in the peripheral immune system. Self-peptides that are presented by disease-associated HLA-class II molecules most likely play important roles during both processes. Here, we examined the functional involvement of the HLA-DR15 haplotype in autologous proliferation in multiple sclerosis and the contribution of HLA-DR15 haplotype-derived self-peptides in an in vitro system. We observe increased autologous T cell proliferation in patients with multiple sclerosis in relation to the multiple sclerosis risk-associated HLA-DR15 haplotype. Assuming that the spectrum of self-peptides that is presented by the two HLA-DR15 allelic products is important for sustaining autologous proliferation we performed peptide elution and identification experiments from the multiple sclerosis-associated DR15 molecules and a systematic analysis of a DR15 haplotype-derived self-peptide library. We identify HLA-derived self-peptides as potential mediators of altered autologous proliferation. Our data provide novel insights about perturbed T cell repertoire dynamics and the functional involvement of the major genetic risk factor, the HLA-DR15 haplotype, in multiple sclerosis.

Immunomodulatory effects of helminths and protozoa in multiple sclerosis and experimental autoimmune encephalomyelitis

Multiple sclerosis is a chronic inflammatory CNS disease, which affects about 1 in 1000 individuals in the western world. During the last couple of decades, epidemiological data have accumulated, pointing towards increases in incidence. This has been suggested to be linked to the relatively high hygiene standards that exist in the western world, with reduced exposure to various pathogens, including parasites, as a consequence. Parasites are known to employ various immunomodulatory and anti-inflammatory strategies, which enable them to evade destruction by the immune system. This is most likely one of the reasons for the disease-dampening effects, reported in numerous studies investigating parasite infections and autoimmunity. This review will focus on recent advances in the field of parasites as beneficial immunomodulators, in multiple sclerosis and the animal model experimental autoimmune encephalomyelitis.

Tolerogenic vaccines for Multiple sclerosis

Tolerogenic vaccines represent a new class of vaccine designed to re-establish immunological tolerance, restore immune homeostasis, and thereby reverse autoimmune disease. Tolerogenic vaccines induce long-term, antigen-specific, inhibitory memory that blocks pathogenic T cell responses via loss of effector T cells and gain of regulatory T cell function. Substantial advances have been realized in the generation of tolerogenic vaccines that inhibit experimental autoimmune encephalomyelitis in a preclinical setting, and these vaccines may be a prequel of the tolerogenic vaccines that may have therapeutic benefit in Multiple Sclerosis. The purpose here is to provide a snapshot of the current concepts and future prospects of tolerogenic vaccination for Multiple Sclerosis, along with the central challenges to clinical application.

Specific T-cell proliferation to myelin peptides in relapsing-remitting multiple sclerosis

BACKGROUND

The identification of major immunogenic peptides in multiple sclerosis (MS) is of great importance for the development of antigen-specific therapies. Cellular reactivity against a selected mix of seven myelin peptides was evaluated in vitro. The evolution of this reactivity over time and its correlation with clinical variables was also analysed.

MATERIAL AND METHODS

  Forty-two patients with MS, 15 with other demyelinating diseases and 40 healthy donors (HD) were studied. Cell proliferation was measured by 3[H] thymidine incorporation into samples obtained at 0, 3, 6 and 12months of MS patient follow-up.

RESULTS

  A positive reaction to the peptide mix was detected in 31 of the 42 patients (74%), 12 of the 40 HD (30%) and 6 of the 15 (40%) patients with other demyelinating diseases. Patients with positive proliferation had greater disability (EDSS score, 3 [1-5.5] vs. 1.0[1-2], P=0.021), higher number of relapses (7±4.1 vs. 3±1.2, P<0.001) and shorter time since the last relapse (9±7.5 vs. 32±12.3months, P=0.036). After 12months of follow-up, cell reactivity was maintained in 33 patients (78%).

CONCLUSION

  A high percentage of patients exhibit a significant and maintained reactivity to myelin peptides over time. Therefore, this mix may be useful as a source of antigen in the development of protocols aimed at inducing specific tolerance in MS.

Th1 versus Th17: are T cell cytokines relevant in multiple sclerosis?

Our understanding of the pathophysiology of multiple sclerosis (MS) has evolved significantly over the past two decades as the fields of immunology and neurobiology provide new avenues of exploration into the cause and mechanism of the disease. It has been known for decades that T cells have different cytokine phenotypes, yet the cytokine phenotype of pathogenic T cells in MS is still an area of debate. In EAE, it appears that IFNγ and IL-17, produced by Th1 and Th17 cells respectively, are not the critical factor that determines T cell encephalitogenicity. However, there are molecules such as IL-23, T-bet and STAT4, that appear to be critical, yet it is unclear whether all these molecules contribute to a common, yet undefined pathway, or act in a synergistic manner which culminates in encephalitogenicity has still to be determined. Therefore, the focus of research on effector T cells in MS should focus on pathways upstream of the cytokines that define Th1 and Th17 cells, since downstream products, such as IFNγ and IL-17, probably are not critical determinants of whether an effector T cells is capable of trafficking to the CNS and inducing inflammatory demyelination.

Immunological basis for the development of tissue inflammation and organ-specific autoimmunity in animal models of multiple sclerosis

Experimental autoimmune encephalomyelitis (EAE) is an animal model for multiple sclerosis (MS) that has shaped our understanding of autoimmune tissue inflammation in the central nervous system (CNS). Major therapeutic approaches to MS have been first validated in EAE. Nevertheless, EAE in all its modifications is not able to recapitulate the full range of clinical and histopathogenic aspects of MS. Furthermore, autoimmune reactions in EAE-prone rodent strains and MS patients may differ in terms of the relative involvement of various subsets of immune cells. However, the role of specific molecules that play a role in skewing the immune response towards pathogenic autoreactivity is very similar in mice and humans. Thus, in this chapter, we will focus on the identification of a novel subset of inflammatory T cells, called Th17 cells, in EAE and their interplay with other immune cells including protective regulatory T cells (T-regs). It is likely that the discovery of Th17 cells and their relationship with T-regs will change our understanding of organ-specific autoimmune diseases in the years to come.

Clone clusters in autoreactive CD4 T-cell lines from probable multiple sclerosis patients form disease-characteristic signatures

We developed a method for selectively propagating disease-related autoreactive T-cell lines (auTCLs) based on their increased resistance to apoptosis. The generated auTCLs homogeneously co-express CD45RO and CD49a, adhere strongly to extracellular matrix proteins and express high interleukin-17 (IL-17) messenger RNA levels, resembling a T-cell subset proposed to transmigrate into tissues and induce systemic and local inflammation in rheumatoid arthritis. The combinations of T-cell oligoclones that comprise probable multiple sclerosis (pMS) disease-related lines use a unique portfolio of T-cell receptor beta-chain variable allele (BV genes) combinations forming 'disease-specific cluster patterns'. The auTCL derived from different patients and from different myelin epitopes display striking similarities in BV gene allele clusters and are derived primarily from a disease-prone hotspot residing in the BV gene locus between Vbeta6 and Vbeta9. Conversely, healthy subject TCLs use different BV gene allele sets, forming 'healthy responder usage formats'. These formats were absent from the pMS patient V-beta gene allele combinations evaluated in this study. Hierarchical clustering of the BV gene combinations, distinguish three pMS auTCL groups, implying existence of up to three disease-related immune response patterns. These subgroup patterns may reflect different disease subclasses or alternatively they may suggest immune reactivity to different aetiological agents. Analyses of clonal-clustering patterns may potentially aid in subclassification of MS or in characterizing aetiological agents of this disease.

Preferential recruitment of interferon-gamma-expressing TH17 cells in multiple sclerosis

OBJECTIVE

There is substantial evidence supporting the role of interferon (IFN)-gamma-producing T helper (T(H)) 1 and interleukin (IL)-17-expressing T(H)17 lymphocytes in multiple sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE). However, to date little is known about the potential cooperative interplay between these 2 cytokines. In the current study, we sought to evaluate the frequency of IFN-gamma-expressing T(H)17 lymphocytes in MS and EAE, and study their recruitment into the central nervous system (CNS).

METHODS

Human T(H)17 lymphocytes were expanded in vitro from the blood of healthy controls and relapsing MS patients using IL-23. Immune cell migration to the CNS was assessed in vitro with primary cultures of human blood-brain barrier (BBB)-derived endothelial cells, and in vivo in EAE mice.

RESULTS

We demonstrate that in response to IL-23, human memory lymphocytes expand into a T(H)17 phenotype, with a subpopulation of cells simultaneously expressing IFN-gamma and IL-17. We note that lymphocytes obtained from the blood of relapsing MS patients have an increased propensity to expand into IFN-gamma-producing T(H)17 cells and identify numerous T lymphocytes coexpressing IL-17 and IFN-gamma in brain tissue of MS patients. We also find lymphocytes expressing both the T(H)1- and the T(H)17-associated transcription factors ROR gamma t and T-bet, in situ and in vitro. We further provide in vitro and in vivo evidence that IFN-gamma(+) T(H)17 lymphocytes preferentially cross the human BBB and accumulate in the CNS of mice during the effector phase of EAE.

INTERPRETATION

Our data underscore the involvement of IFN-gamma(+) T(H)17 lymphocytes in the pathology of MS and EAE and their preferential recruitment into the CNS during inflammatory events.

Urinary CD4+ effector memory T cells reflect renal disease activity in antineutrophil cytoplasmic antibody-associated vasculitis

OBJECTIVE

Numbers of circulating CD4+ effector memory T cells are proportionally increased in patients with proteinase 3 antineutrophil cytoplasmic antibody-associated vasculitis (AAV) whose disease is in remission and are decreased during active disease, which presumably reflects their migration toward sites of inflammation. Since renal infiltrating cells may appear in urine, we investigated the presence of CD4+ effector memory T cells in urinary sediment as a reflection of renal disease activity in AAV.

METHODS

CD4+ effector memory (CD45RO+CCR7-CD3+CD4+) T cells were quantitated in the urine and peripheral blood of patients with AAV with renal involvement (n = 33), patients with AAV without renal involvement (n = 18), patients with AAV whose disease was in remission (n = 29), and patients with active disease (n = 22), using 4-color flow cytometric analysis. Numbers and percentages of urine CD4+ effector memory T cells in 12 patients with AAV with active renal disease were obtained over several weeks of followup during remission induction.

RESULTS

A notable increase in urine CD4+ effector memory T cell numbers was observed in patients with active renal AAV compared with patients whose disease was in remission and patients with active disease without renal involvement. The increase in these cells in the urine of patients with active renal AAV was accompanied by a reciprocal decrease in these cells in peripheral blood. Results from followup analysis showed a clear reduction in urine CD4+ effector memory T cells following treatment. Moreover, a negative correlation was observed between percentages of circulating and urine CD4+ effector memory T cells, consistent with their migration toward sites of inflammation.

CONCLUSION

Our findings indicate that the presence of CD4+ effector memory T cells in urine reflects renal involvement in AAV. Flow cytometric analysis of these cells in urine may contribute to assessing renal disease activity in patients with AAV.

T-bet is essential for encephalitogenicity of both Th1 and Th17 cells

The extent to which myelin-specific Th1 and Th17 cells contribute to the pathogenesis of experimental autoimmune encephalomyelitis (EAE) is controversial. Combinations of interleukin (IL)-1β, IL-6, and IL-23 with transforming growth factor β were used to differentiate myelin-specific T cell receptor transgenic T cells into Th17 cells, none of which could induce EAE, whereas Th1 cells consistently transferred disease. However, IL-6 was found to promote the differentiation of encephalitogenic Th17 cells. Further analysis of myelin-specific T cells that were encephalitogenic in spontaneous EAE and actively induced EAE demonstrated that T-bet expression was critical for pathogenicity, regardless of cytokine expression by the encephalitogenic T cells. These data suggest that encephalitogenicity of myelin-specific T cells appears to be mediated by a pathway dependent on T-bet and not necessarily pathway-specific end products, such as interferon γ and IL-17.

Autoimmune T cell responses in the central nervous system

Autoreactive T cell responses have a crucial role in central nervous system (CNS) diseases such as multiple sclerosis. Recent data indicate that CNS autoimmunity can be mediated by two distinct lineages of CD4+ T cells that are defined by the production of either interferon-gamma or interleukin-17. The activity of these CD4+ T cell subsets within the CNS influences the pathology and clinical course of disease. New animal models show that myelin-specific CD8+ T cells can also mediate CNS autoimmunity. This Review focuses on recent progress in delineating the pathogenic mechanisms, regulation and interplay between these different T cell subsets in CNS autoimmunity.

Polyunsaturated fatty acids in the pathogenesis and treatment of multiple sclerosis

Epidemiological, biochemical, animal model and clinical trial data described in this overview strongly suggest that polyunsaturated fatty acids, particularly n-6 fatty acids, have a role in the pathogenesis and treatment of multiple sclerosis (MS). Data presented provides further evidence for a disturbance in n-6 fatty acid metabolism in MS. Disturbance of n-6 fatty acid metabolism and dysregulation of cytokines are shown to be linked and a "proof of concept clinical trial" further supports such a hypothesis. In a randomised double-blind, placebo controlled trial of a high dose and low dose selected GLA (18:3n-6)-rich oil and placebo control, the high dose had a marked clinical effect in relapsing-remitting MS, significantly decreasing the relapse rate and the progression of disease. Laboratory findings paralleled clinical changes in the placebo group in that production of mononuclear cell pro-inflammatory cytokines (TNF-alpha, IL-1beta) was increased and anti-inflammatory TGF-beta markedly decreased with loss of membrane n-6 fatty acids linoleic (18:2n-6) and arachidonic acids (20:4n-6). In contrast there were no such changes in the high dose group. The improvement in disability (Expanded Disability Status Scale) in the high dose suggests there maybe a beneficial effect on neuronal lipids and neural function in MS. Thus disturbed n-6 fatty acid metabolism in MS gives rise to loss of membrane long chain n-6 fatty acids and loss of the anti-inflammatory regulatory cytokine TGF-beta, particularly during the relapse phase, as well as loss of these important neural fatty acids for CNS structure and function and consequent long term neurological deficit in MS.

Reshaping the past: Strategies for modulating T-cell memory immune responses

Memory T cells are generated following an initial encounter with antigen, persist over the lifetime of an individual, and mediate rapid and robust functional responses upon antigenic recall. While immune memory is generally associated with protective immune response to pathogens, memory T cells can be generated to diverse types of antigens including autoantigens and alloantigens through homologous or crossreactive priming and comprise the majority of circulating T cells during adulthood. Memory T cells can therefore play critical roles in propagating and perpetuating autoimmune disease and in mediating allograft rejection, although the precise pathways for regulation of memory immune responses remain largely undefined. Moreover, evaluating and designing strategies to modulate memory T-cell responses are challenging given the remarkable heterogeneity of memory T cells, with different subsets predominating in lymphoid versus non-lymphoid tissue sites. In this review, we discuss what is presently known regarding the effect of current immunomodulation strategies on the memory T-cell compartment and potential strategies for controlling immunological recall.

Potassium channels, memory T cells, and multiple sclerosis

Multiple sclerosis is a chronic inflammatory autoimmune disease of the central nervous system characterized by demyelination and axonal damage that result in disabling neurological deficits. Here the authors explain the rationale for the use of inhibitors of the Kv1.3 K+ channel in immune cells as a therapy for multiple sclerosis and other autoimmune disorders.

Tissue-resident memory CD8+ T cells can be deleted by soluble, but not cross-presented antigen

Under noninflammatory conditions, both naive and central memory CD8 T cells can be eliminated in the periphery with either soluble peptide or cross-presented Ag. Here, we assess the tolerance susceptibility of tissue-resident memory CD8 T cells in mice to these two forms of tolerogen. Soluble peptide specifically eliminated the majority of memory CD8 cells present in both lymphoid and extralymphoid tissues including lung and liver, but was unable to reduce the number present in the CNS. In contrast, systemic cross-presentation of Ag by dendritic cells resulted in successful elimination of memory cells only from the spleen, with no significant reduction in the numbers of tissue-resident memory cells in the lung. The fact that tissue-resident memory cells were unable to access cross-presented Ag suggests that either the memory cells in the lung do not freely circulate out of the tissue, or that they circulate through a region in the spleen devoid of cross-presented Ag. Thus, although tissue-resident memory cells are highly susceptible to tolerance induction, both the form of tolerogen and location of the T cells can determine their accessibility to tolerogen and the degree to which they are successfully deleted from specific tissues.

Effect of gender on T-cell proliferative responses to myelin proteolipid protein antigens in patients with multiple sclerosis and controls

Multiple sclerosis (MS) is an inflammatory demyelinating disorder of the central nervous system. Gender influences both susceptibility to MS, with the disease being more common in women, and the clinical course of disease, with an increased proportion of males developing the primary progressive form of the disease. The basis for these differences may include genetic and immunological factors, and the immunological differences between men and women may be influenced by the effects of the sex hormones. Over several years we have collected blood from MS patients and controls, and measured T-cell responses to myelin proteolipid protein (PLP) and myelin basic protein (MBP) and have shown increased responses to PLP in MS patients compared to healthy controls and patients with other neurological diseases. In the present study we analyzed data from over 500 individuals, to determine whether there are differences between males and females in their responses to PLP and MBP. We found that there was higher frequency of increased T-cell reactivity to immunodominant PLP peptides in women than in men, particularly in non-MS individuals. We suggest that this may be relevant to the higher prevalence of MS in women.

Expansion and Functional Relevance of High-Avidity Myelin-Specific CD4+T Cells in Multiple Sclerosis

Multiple sclerosis (MS) is an autoimmune disease in which myelin-specific T cells are believed to play a crucial pathogenic role. Nevertheless, so far it has been extremely difficult to demonstrate differences in T cell reactivity to myelin Ag between MS patients and controls. We believe that by using unphysiologically high Ag concentrations previous studies have missed a highly relevant aspect of autoimmune responses, i.e., T cells recognizing Ag with high functional avidity. Therefore, we focused on the characterization of high-avidity myelin-specific CD4+ T cells in a large cohort of MS patients and controls that was matched demographically and with respect to expression of MHC class II alleles. We demonstrated that their frequency is significantly higher in MS patients while the numbers of control T cells specific for influenza hemagglutinin are virtually identical between the two cohorts; that high-avidity T cells are enriched for previously in vivo-activated cells and are significantly skewed toward a proinflammatory phenotype. Moreover, the immunodominant epitopes that were most discriminatory between MS patients and controls differed from those described previously and were clearly biased toward epitopes with lower predicted binding affinities to HLA-DR molecules, pointing at the importance of thymic selection for the generation of the autoimmune T cell repertoire. Correlations between selected immunological parameters and magnetic resonance imaging markers indicate that the specificity and function of these cells influences phenotypic disease expression. These data have important implications for autoimmunity research and should be considered in the development of Ag-specific therapies in MS.

Evidence for cytokine dysregulation in multiple sclerosis: peripheral blood mononuclear cell production of pro-inflammatory and anti-inflammatory cytokines during relapse and remission

We investigated circulating anti-inflammatory and pro-inflammatory cytokines, and their ex vivo PBMC production in the absence or presence of the neuroantigens myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG) and T cell mitogen (PHA) in MS patients in relapse and remission, patients with other neurological disorders (OND) and normal healthy controls. MS patients in relapse exhibited significantly increased PBMC production of TNF-alpha spontaneously compared with MS remission and healthy controls and with MBP compared with MS remission. Patients in relapse had significantly increased spontaneous, PHA- and MBP-induced PBMC IL-1beta production compared with remission MS, and was increased compared (PHA only) with OND and healthy controls. In relapse there was also significantly increased PBMC IFN-gamma production (PHA only) compared with remission and a significantly lower production of biologically active TGF-beta1 (PHA only) compared with remission MS and OND. In contrast, MS patients in remission produced significantly less spontaneous and MBP-induced TNF-alpha, spontaneous, PHA- and MBP-induced IL-1beta and PHA-induced IFN-gamma together with increased production of biologically active TGF-beta1. MOG non-specifically increased PBMC TNF-alpha and IL-1beta production in all groups. Pro-inflammatory cytokines in corresponding plasma samples were undetectable whilst the concentration of biologically active TGF-beta1 was the reverse of ex vivo PBMC findings. The increase in biologically active TGF-beta1 production ex vivo in OND patients, despite active disease, compared with the low level in the MS relapse may indicate a regulatory defect in MS. We conclude that the balance between biologically active TGF-beta1 and the pro-inflammatory TNF-alpha, IL-1beta and IFN-gamma is dysregulated during MS relapse-remission and that normal counter-regulatory mechanisms during the relapse phase are defective.

Multiple sclerosis associated with interferon-alpha therapy for chronic myelogenous leukemia

We report a chronic myelogenous leukemia (CML) patient in chronic phase (CP) who developed multiple sclerosis (MS) in association with interferon-alpha (IFN-alpha) administration. In our patient, recombinant IFN-alpha2b therapy induced hematologically complete and cytogenetically major partial response for CML first, and sequential central nervous system dysfunction evolved, which subsided shortly after the cessation of its administration. Restarting IFN-alpha therapy by changing to a natural type of IFN-alpha resulted in rapid exacerbation of MS. The patient's neurological symptoms progressed gradually, but partial hematologic response persisted without any IFN-alpha derivatives or anti-cancer agents until a matched unrelated donor transplant procedure was performed. Myeloablative therapy led to lasting stable state of MS and finally to complete cytogenetic remission of CML. This patient's presenting clinical course and laboratory data suggest that both exertion of anti-leukemic activity and autoimmune process of MS might be mediated by mutual mechanisms, such as enhancement of specific cellular immunity induced by IFN-alpha.

Chemokine receptor expression on MBP-reactive T cells: CXCR6 is a marker of IFNgamma-producing effector cells

Cytokine-polarized T cells have distinct chemokine receptor (CKR) expression patterns associated with their cytokine secretion profiles. In order to investigate this paradigm in autoreactive human T cells, we have determined the CKR expression pattern of myelin basic protein (MBP)-reactive T cell lines (TCL) and compared these profiles to those of TCL-generated in response to tetanus toxoid (TT). Expression of CXCR6 and CXCR3 on TCL was significantly positively correlated with IFNgamma, and inversely correlated with IL-5 production. TT TCL had significantly higher expression of CCR7(-)/CD45RA(-) T effector memory (Tem) cells than MBP TCL. However, in MBP-specific TCL, CXCR6 was found to be the best marker of conversion to the Tem phenotype. CXCR6 and CXCR3 are likely to be important in the migration of effector memory T cells in Th1-mediated inflammatory diseases such as multiple sclerosis (MS).

IL-7-enhanced T-cell response to myelin proteins in multiple sclerosis

In this study, we investigated the in vitro proliferative response of peripheral blood T lymphocytes from MS patients and controls to MBP and MOG either in the absence or in the presence of the conditioning factor IL-7. In the absence of IL-7, T-cell reactivity to MOG and MBP was similar in MS patients and controls even if an increased MBP response was found in a subgroup of patients with active disease. In the presence of IL-7, increased T-cell reactivity to MBP was observed in MS patients suggesting that their MBP-specific T cells are in a different functional state.

Isolation of CD45RO+, memory T cells recognizing proteolipid protein from neurologically normal subjects

Previous studies provide evidence for in vivo activation of MBP-reactive T cells in subjects with multiple sclerosis. In general, in vivo activation occurs less frequently in healthy control subjects. In the current study we examined the T cell response to proteolipid protein in PBMC isolated from 9 control subjects. We used CD45 isotypes as markers for memory and naïve T cells to assess in vivo activation of CD4+ T cells reactive with PLP. In contrast to the results obtained using MBP, we found that approximately 50% of PLP-reactive T cells were derived from the CD45RO+ memory subpopulation of T cells isolated from these control subjects. These results indicate that some myelin-reactive T cells have undergone activation in vivo in neurologically intact individuals. This suggests that immunoregulatory mechanisms may be present that prevent overt disease in spite of in vivo activation of PLP-reactive T cells.

Altered phenotype and function of blood dendritic cells in multiple sclerosis are modulated by IFN-beta and IL-10

Multiple sclerosis (MS) is assumed to result from autoaggressive T cell-mediated immune responses, in which T helper type 1 (Th1) cells producing cytokines, e.g. IFN-gamma and lymphotoxin promote damage of oligodendrocyte-myelin units. Dendritic cells (DCs) as potent antigen presenting cells initiate and orchestrate immune responses. Whether phenotype and function of DCs with respect to Th1 cell promotion are altered in MS, are not known. This study revealed that blood-derived DCs from MS patients expressed low levels of the costimulatory molecule CD86. In addition, production of IFN-gamma by blood mononuclear cells (MNCs) was strongly enhanced by DCs derived from MS patients. IFN-beta and IL-10 inhibited the costimulatory capacity of DCs in mixed lymphocyte reaction (MLR) and showed additive effects on suppression of IL-12 production by DCs. Correspondingly, DCs pretreated with IFN-beta and IL-10 significantly suppressed IFN-gamma production by MNCs. IFN-beta in vitro also upregulated CD80 and, in particular, CD86 expression on DCs. In vitro, anti-CD80 antibody remarkably increased, while anti-CD86 antibody inhibited DC-induced IL-4 production in MLR. We conclude that DC phenotype and function are altered in MS, implying Th1-biased responses with enhanced capacity to induce Th1 cytokine production. In vitro modification of MS patients' DCs by IFN-beta and IL-10 could represent a novel way of immunomodulation and of possible usefulness for future immunotherapy of MS.

Differential responses of CD45+ve T-cell subsets to MBP in multiple sclerosis

The proliferative response of preparations of whole PBMC populations from 20 healthy individuals and 28 multiple sclerosis (MS) patients to purified protein derivative (PPD) and myelin basic protein (MBP) was monitored in a kinetic assay over a period of up to 10 days. PPD produced a classical secondary response in both groups, the magnitude being significantly reduced in the MS cohort. The magnitude and pattern of response to MBP did not differ between the two populations. The kinetic profile characteristic of a primary response was observed in both groups. Enrichment of the CD45RO+ve and CD45RA+ve T-cell subsets in PBMC led to a secondary response to PPD in the RO+ve and primary response in the RA+ve population in both groups. The response to MBP in both RO+ve and RA+ve populations exhibited primary kinetics in both MS patients and healthy individuals. However, the use of T-cell subset enriched populations allowed a finer dissection of the response to MBP which highlighted the more active role of RO-positive cells in MS patients. The most striking difference between patients and healthy individuals occurred on day 4 of culture when a greater response to MBP occurred in the CD45RO enriched population, paralleling the response to PPD, in the majority of patients. Futhermore in 4/8 patients and only 1/8 healthy individuals the response in the RO+ve cultures was maintained at a higher level than that seen in the corresponding RA+ve cultures throughout the culture period. This data indicates that a measurable memory response to MBP exists in MS patients implying prior activation of MBP reactive T lymphocytes during the course of disease.

T cells, cytokines, and autoantigens in multiple sclerosis

In multiple sclerosis (MS), inflammatory demyelination in the central nervous system is thought to be initiated by T cells that recognize myelin antigens. T cells are the main regulators of acquired immunity and are involved in the pathogenesis of several organ-specific autoimmune diseases. This review provides an overview of recent studies on the role of T cells in autoimmune demyelination. Because autoreactive T cells are normally present in the mature repertoire of T cells in the blood and lymphoid organs of MS patients, but also in normal controls, particular attention is devoted to the mechanisms of activation and the functional phenotype of such T cells in patients with MS. The role of cytokines as effector molecules and the main candidate antigens are also discussed.

Kinetic profiles of cerebrospinal fluid anti-MBP in response to intravenous MBP synthetic peptide DENP(85)VVHFFKNIVTP(96)RT in multiple sclerosis patients

Multiple sclerosis [MS], a demyelinating disease of the central nervous system associated with inflammation and gliosis, may be an autoimmune disease with T lymphocytes and autoantibodies to myelin protein(s). This study deals exclusively with B cell autoimmunity to myelin basic protein (MBP). T lymphocytes and anti-MBP share a common MBP epitope located between P(85) and P(96) which contains the essential contact residues H(88)FFK(91) for the trimolecular complex. The purpose of this Phase I open label clinical study was to monitor CSF anti-MBP in patients with chronic progressive MS subsequent to IV administration of synthetic peptide (sp) MBP82-98 namely DEN(85)VVHFFKNIVTP(96)RT. Fifty-six patients who participated in this project were assigned to two groups: a 'control group' of 15 patients who received IV saline injections every 6 months for the first 2 years of the study and a 'peptide group' of 41 patients who received IV spMBP82-98 from the beginning of the study and then infrequently subsequent to a rise of their CSF anti-MBP. In the control group antibody levels remained persistently elevated during the 2 year period. Patients in the 'peptide group' segregated into four kinetic profiles: Cohort A (15 patients) illustrated prolonged anti-BMP suppression into the normal range. Cohort B (10 patients) illustrated significant anti-MBP suppression into the normal range for shorter durations. Cohort C (eight patients) showed significant CSF anti-MBP suppression after the initial injection but lost the ability to suppress the autoantibody titer following subsequent injections. Cohort D (eight patients) failed to show significant CSF anti-MBP suppression. In conclusion the B cell tolerizing effect of spMBP82-98 segregated into four kinetic profiles; this molecular variability should be considered in attempts to develop specific 'peptide therapies' for the broad range of clinical profiles currently diagnosed as 'multiple sclerosis'. Multiple Sclerosis (2000) 6 300 - 311

Flow cytometric differentiation of Asian and Western types of multiple sclerosis, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and hyperIgEaemic myelitis by analyses of memory CD4 positive T cell subsets and NK cell subsets

We examined the alterations of memory CD4(+) T cell subsets bearing surface receptors linked to either Th1 or Th2 cytokine production as well as natural killer (NK) cell subsets by three color flow cytometry in the peripheral blood from 36 patients with clinically definite multiple sclerosis (MS), 27 patients with HAM/TSP, 13 patients with hyperIgEaemic myelitis who had mite antigen-specific IgE and 25 healthy controls (HC). The patients with MS were clinically classified into an optico-spinal form of MS (Asian type, MS-A) and the conventional form of MS (Western type, MS-W). MS-A showed a significant increase of CD4(+)CD45RA(-)CCR5(+) cells (Th1 cells) through the relapse and remission phases in comparison to HC, while MS-W showed a significant increase of CD4(+)CD45RO(+)CD62L(-) cells (Th1 cells) only at the relapse phase. HAM/TSP showed a significant increase of CCR5(+) and CD62L(-) memory CD4(+) T cells as well as CD30(+) memory CD4(+) T cells (Th2 cells) in comparison to HC. On the other hand, a selective increase of CD4(+)CD45RO(+)CD30(+) cells was found in hyperIgEaemic myelitis. The percentage of mature NK cells (CD3(-)CD16(+)CD56(+) cells) as well as double negative T cells (CD3(+)CD4(-)CD8(-) cells) decreased significantly in HAM/TSP in comparison to HC. Our findings therefore suggest a flow cytometric analysis of Th1/Th2-associated markers on memory CD4(+) T cells as well as NK cell subsets to be useful for differentiating various inflammatory neurologic conditions.

Human autoreactive CD4+ T cells from naive CD45RA+ and memory CD45RO+ subsets differ with respect to epitope specificity and functional antigen avidity

T cells with specificity for self-Ags are normally present in the peripheral blood, and, upon activation, may target tissue Ags and become involved in the pathogenesis of autoimmune processes. In multiple sclerosis, a demyelinating disease of the CNS, it is postulated that inflammatory damage is initiated by CD4+ T cells reactive to myelin Ags. To investigate the potential naive vs memory origin of circulating myelin-reactive cells, we have generated myelin basic protein (MBP)- and tetanus toxoid-specific T cell clones from CD45RA+/RO- and CD45RO+/RA- CD4+ T cell subsets from the peripheral blood of multiple sclerosis patients and controls. Our results show that 1) the response to MBP, different from that to TT, predominantly emerges from the CD45RA+ subset; 2) the reactivity to immunodominant MBP epitopes mostly resides in the CD45RA+ subset; 3) in each individual, the recognition of single MBP epitopes is skewed to either subset, with no overlap in the Ag fine specificity; and 4) in spite of a lower expression of costimulatory and adhesion molecules, CD45RA+ subset-derived clones recognize epitopes with higher functional Ag avidity. These findings point to a central role of the naive CD45RA+ T cell subset as the source for immunodominant, potentially pathogenic effector CD4+ T cell responses in humans.