Frequency of T cells specific for myelin basic protein and myelin proteolipid protein in blood and cerebrospinal fluid in multiple sclerosis

Tissue-resident memory CD8+ T cells cooperate with CD4+ T cells to drive compartmentalized immunopathology in the CNS

In chronic inflammatory diseases of the central nervous system (CNS), immune cells persisting behind the blood-brain barrier are supposed to promulgate local tissue destruction. The drivers of such compartmentalized inflammation remain unclear, but tissue-resident memory T cells (T_RM) represent a potentially important cellular player in this process. Here, we investigated whether resting CD8⁺ T_RM persisting after cleared infection with attenuated lymphocytic choriomeningitis virus (LCMV) can initiate immune responses directed against cognate self-antigen in the CNS. We demonstrated that time-delayed conditional expression of the LCMV glycoprotein as neo-self-antigen by glia cells reactivated CD8⁺ T_RM. Subsequently, CD8⁺ T_RM expanded and initiated CNS inflammation and immunopathology in an organ-autonomous manner independently of circulating CD8⁺ T cells. However, in the absence of CD4⁺ T cells, TCF-1⁺ CD8⁺ T_RM failed to expand and differentiate into terminal effectors. Similarly, in human demyelinating CNS autoimmune lesions, we found CD8⁺ T cells expressing TCF-1 that predominantly exhibited a T_RM-like phenotype. Together, our study provides evidence for CD8⁺ T_RM-driven CNS immunopathology and sheds light on why inflammatory processes may evade current immunomodulatory treatments in chronic autoimmune CNS conditions.

Brain Antigens Stimulate Proliferation of T Lymphocytes With a Pathogenic Phenotype in Multiple Sclerosis Patients

A method to stimulate T lymphocytes with a broad range of brain antigens would facilitate identification of the autoantigens for multiple sclerosis and enable definition of the pathogenic mechanisms important for multiple sclerosis. In a previous work, we found that the obvious approach of culturing leukocytes with homogenized brain tissue does not work because the brain homogenate suppresses antigen-specific lymphocyte proliferation. We now report a method that substantially reduces the suppressive activity. We used this non-suppressive brain homogenate to stimulate leukocytes from multiple sclerosis patients and controls. We also stimulated with common viruses for comparison. We measured proliferation, selected the responding CD3+ cells with flow cytometry, and sequenced their transcriptomes for mRNA and T-cell receptor sequences. The mRNA expression suggested that the brain-responding cells from MS patients are potentially pathogenic. The T-cell receptor repertoire of the brain-responding cells was clonal with minimal overlap with virus antigens.

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.

Harnessing regulatory T cell neuroprotective activities for treatment of neurodegenerative disorders

Emerging evidence demonstrates that adaptive immunity influences the pathobiology of neurodegenerative disorders. Misfolded aggregated self-proteins can break immune tolerance leading to the induction of autoreactive effector T cells (Teffs) with associated decreases in anti-inflammatory neuroprotective regulatory T cells (Tregs). An imbalance between Teffs and Tregs leads to microglial activation, inflammation and neuronal injury. The cascade of such a disordered immunity includes the drainage of the aggregated protein antigens into cervical lymph nodes serving to amplify effector immune responses. Both preclinical and clinical studies demonstrate transformation of this altered immunity for therapeutic gain. We posit that the signs and symptoms of common neurodegenerative disorders such as Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, and stroke can be attenuated by boosting Treg activities.

The Diversity of Encephalitogenic CD4+ T Cells in Multiple Sclerosis and Its Animal Models

Autoreactive CD4+ T cells, which target antigens in central nervous system (CNS) myelin, are widely believed to play a critical role in the pathogenesis of multiple sclerosis (MS) in concert with other immune effectors. This theory is supported by data from animal model experiments, genome-wide association studies, and immune profiles of individuals with MS. Furthermore, disease modifying agents that target lymphocytes significantly reduce the rate of MS clinical exacerbations. However, the properties of myelin-reactive CD4+ T cells that are critical for their pathogenic activities are not understood completely. This article reviews the literature on encephalitogenic CD4+ T cells, with an emphasis on T-helper (Th) lineage and cytokine production. An increased understanding of the spectrum of encephalitogenic T cells and how they differ from protective subsets is necessary for the development of the next generation of more effective and safer immunomodulatory therapies customized for individuals with MS and related disorders.

Experimental Autoimmune Encephalomyelitis (EAE) as Animal Models of Multiple Sclerosis (MS)

Multiple sclerosis (MS) is a multifocal demyelinating disease of the central nervous system (CNS) leading to the progressive destruction of the myelin sheath surrounding axons. It can present with variable clinical and pathological manifestations, which might reflect the involvement of distinct pathogenic processes. Although the mechanisms leading to the development of the disease are not fully understood, numerous evidences indicate that MS is an autoimmune disease, the initiation and progression of which are dependent on an autoimmune response against myelin antigens. In addition, genetic susceptibility and environmental triggers likely contribute to the initiation of the disease. At this time, there is no cure for MS, but several disease-modifying therapies (DMTs) are available to control and slow down disease progression. A good number of these DMTs were identified and tested using animal models of MS referred to as experimental autoimmune encephalomyelitis (EAE). In this review, we will recapitulate the characteristics of EAE models and discuss how they help shed light on MS pathogenesis and help test new treatments for MS patients.

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.

A highly immunogenic trivalent T cell receptor peptide vaccine for multiple sclerosis

Background: T cell receptor (TCR) peptide vaccination is a novel approach to treating multiple sclerosis (MS). The low immunogenicity of previous vaccines has hindered the development of TCR peptide vaccination for MS. Objective: To compare the immunogenicity of intramuscular injections of TCR BV5S2, BV6S5 and BV13S1 CDR2 peptides in incomplete Freund’s adjuvant (IFA) with intradermal injections of the same peptides without IFA. Methods: MS subjects were randomized to receive TCR peptides/IFA, TCR peptides/saline or IFA alone. Subjects were on study for 24 weeks. Results: The TCR peptides/IFA vaccine induced vigorous T cell responses in 100% of subjects completing the 24-week study (9/9) compared with only 20% (2/10) of those receiving the TCR peptides/saline vaccine (P =0.001). IFA alone induced a weak response in only one of five subjects. Aside from injection site reactions, there were no significant adverse events attributable to the treatment. Conclusions: The trivalent TCR peptide in IFA vaccine represents a significant improvement in immunogenicity over previous TCR peptide vaccines and warrants investigation of its ability to treat MS.

Multiple Sclerosis and T Lymphocytes: An Entangled Story

Multiple sclerosis (MS) is the prototypic inflammatory disease of the central nervous system (CNS) characterized by multifocal areas of demyelination, axonal damage, activation of glial cells, and immune cell infiltration. Despite intensive years of research, the etiology of this neurological disorder remains elusive. Nevertheless, the abundance of immune cells such as T lymphocytes and their products in CNS lesions of MS patients supports the notion that MS is an immune-mediated disorder. An important body of evidence gathered from MS animal models such as experimental autoimmune encephalomyelitis (EAE), points to the central contribution of CD4 T lymphocytes in disease pathogenesis. Both Th1 (producing interferon-γ) and Th17 (producing interleukin 17) CD4 T lymphocytes targeting CNS self-antigens have been implicated in MS and EAE pathobiology. Moreover, several publications suggest that CD8 T lymphocytes also participate in the development of MS lesions. The migration of activated T lymphocytes from the periphery into the CNS has been identified as a crucial step in the formation of MS lesions. Several factors promote such T cell extravasation including: molecules (e.g., cell adhesion molecules) implicated in the T cell-blood brain barrier interaction, and chemokines produced by neural cells. Finally, once in the CNS, T lymphocytes need to be reactivated by local antigen presenting cells prior to enter the parenchyma where they can initiate damage. Further investigations will be necessary to elucidate the impact of environmental factors (e.g., gut microbiota) and CNS intrinsic properties (e.g., microglial activation) on this inflammatory neurological disease.

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

Multiple sclerosis (MS) is a chronic disease of the central nervous system (CNS) typically characterized by the recruitment of T cells into the CNS. However, certain subsets of B cells have been shown to negatively regulate autoimmune diseases and some data support a prominent role for B cells in MS physiopathology. For B cells in MS patients we analyzed subset frequency, cytokine secretion ability and suppressive properties. No differences in the frequencies of the B-cell subsets or in their ability to secrete cytokines were observed between MS and healthy volunteers (HV). Prestimulated B cells from MS patients also inhibited CD4(+)CD25(-) T cell proliferation with a similar efficiency as B cells from HV. Altogether, our data show that, in our MS patient cohort, regulatory B cells have conserved frequency and function.

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.

A small-molecule inhibitor of macrophage migration inhibitory factor for the treatment of inflammatory disease

Multiple sclerosis (MS) is a chronic, debilitating disease of the central nervous system (CNS) characterized by demyelination and axon loss. The proinflammatory cytokine macrophage migration inhibitory factor (MIF) has been shown to be elevated in the cerebrospinal fluid of patients during relapses. The purpose of this study was to evaluate a new small-molecule inhibitor of MIF and its ability to reduce the severity of an animal model of MS, experimental autoimmune encephalomyelitis (EAE). We utilized 2 structurally related isoxazolines, which show in vitro inhibition of MIF tautomerase activity. We found that administration of an inhibitor of MIF to mice with established EAE immediately reduced the severity of clinical signs and expanded a population of regulatory T lymphocytes. We also noted that the inhibitor reduced relapses of disease in a relapsing/remitting model of EAE. An analysis of leukocyte migration into the brain revealed that administration of inhibitor reduced entry of these cells. No effects on inflammatory cytokine production or T-cell activation in the periphery were noted. From these studies, we conclude that a small-molecule inhibitor of MIF reduces the severity of EAE and prevents access of immune cells into the CNS, which could be of therapeutic relevance to MS.

T-cell-based immunotherapy in multiple sclerosis: induction of regulatory immune networks by T-cell vaccination

Multiple sclerosis (MS) is a chronic inflammatory disease of the CNS with presumed autoimmune origin. Pathogenic autoimmune responses in MS are thought to be the result of a breakdown of self tolerance. Several mechanisms account for the natural state of immunological tolerance to self antigens, including clonal deletion of self-reactive T cells in the thymus. However, autoimmune T cells are also part of the normal T-cell repertoire, supporting the existence of peripheral regulatory mechanisms that keep these potentially pathogenic T cells under control. One such mechanism involves active suppression by regulatory T cells. It has been indicated that regulatory T cells do not function properly in autoimmune disease. Immunization with attenuated autoreactive T cells, T-cell vaccination, may enhance or restore the regulatory immune networks to specifically suppress autoreactive T cells, as shown in experimental autoimmune encephalomyelitis, an animal model for MS. In the past decade, T-cell vaccination has been tested for MS in several clinical trials. This review summarizes these clinical trials and updates our current knowledge on the induction of regulatory immune networks by T cell vaccination.

T cell recognition of self-antigen presenting cells by protein transfer assay reveals a high frequency of anti-myelin T cells in multiple sclerosis

Although peripheral blood myelin-autoreactive T cells are thought to play a key role in multiple sclerosis, they are generally considered to have qualitative differences rather than quantitative ones when compared to those found in healthy individuals. Here, we revisited the assessment of myelin-autoreactive T cells in a new approach based on their combined ability to acquire membrane proteins from autologous antigen presenting cells, and to respond to whole myelin extract as the stimulating autoantigen. Using this approach, the myelin-autoreactive T cell frequency in patients with multiple sclerosis was found to be unexpectedly high (n = 22, subtracted values median 2.08%, range 0-6%; background median 1%, range 0-4%) and to exceed that of age/gender-matched healthy individuals significantly (n = 18, subtracted values median 0.1%, range 0-5.3%, P < 0.0001; background median 1.45%, range 0.1-4%). Higher anti-myelin autoreactivity was stable in patients with multiple sclerosis after several months. These data correlated with whole myelin-induced gamma interferon-enzyme-linked immunosorbent spot assay performed under the same conditions, although the values obtained with enzyme-linked immunosorbent spot assay under all conditions were 58 times lower than with this new method. The myelin-autoreactive T cells were memory T cells expressing CD40L with a CD62(low) phenotype, suggesting their ability for homing to tissues. Collectively, these new data show a higher frequency of autoreactive T cells during multiple sclerosis than in age/gender-matched healthy individuals, and support an autoimmune aetiology in multiple sclerosis.

Prevention and treatment of experimental autoimmune encephalomyelitis with clonotypic CDR3 peptides: CD4(+) Foxp3(+) T-regulatory cells suppress interleukin-2-dependent expansion of myelin basic protein-specific T cells

T-cell receptor (TCR)-derived peptides are recognized by the immune system and are capable of modulating autoimmune responses. Using the myelin basic protein (MBP) TCR 1501 transgenic mouse model, we demonstrated that TCR CDR3 peptides from the transgenic TCR can provide a protective effect when therapy is initiated before the induction of experimental autoimmune encephalomyelitis (EAE). More importantly, TCR CDR3 peptide therapy can ameliorate the disease when administered after EAE onset. Concurrent with the therapeutic effects, we observed reduced T-cell proliferation and reduced interleukin-2 (IL-2) levels in response to stimulation with MBP-85-99 peptide in splenocyte cultures from mice receiving TCR CDR3 peptides compared with that of control mice. Moreover, we found that Foxp3(+) CD4 T cells from mice protected with TCR CDR3 peptide are preferentially expanded in the presence of IL-2. This is supportive of a proposed mechanism where Foxp3(+) T-regulatory cells induced by therapy with MBP-85-99 TCR CDR3 peptides limit expansion and the encephalitogenic activity of MBP-85-99-specific T cells by regulating the levels of secreted IL-2.

A DNA vaccine for multiple sclerosis

BACKGROUND

Multiple sclerosis (MS) is a disease in which safety is of paramount importance when developing a potential therapeutic. Antigen-specific treatments provide a method for achieving efficacy while maintaining safety. DNA vaccines are one such form of treatment that have been tested in clinical trials

OBJECTIVE

To determine if a DNA vaccine is a viable method of antigen-specific treatment of MS.

RESULTS/CONCLUSION

Phase I and II trials of BHT-3009, a DNA vaccine encoding myelin basic protein, demonstrated that it was safe, well-tolerated, and caused antigen-specific immune tolerance. BHT-3009 showed efficacy in reducing brain lesion activity as well as clinical relapses in patients that were immunologically active at baseline. BHT-3009 is a promising therapy in development for MS, and may prove to be one of the first antigen-specific treatments for this disease.

Autologous T-cell vaccination for multiple sclerosis: a perspective on progress

T-cell vaccination (TCV) is a unique approach to induce immune regulation that may have importance in the treatment of autoimmune diseases, including multiple sclerosis (MS). TCV employs a classic vaccine strategy of injecting an attenuated form of the disease-causing agent--in this case, myelin-reactive T cells--that have been selected and expanded from each MS donor and then re-injected after irradiation to induce protective immunity. This anti-T-cell immunity consistently results in selective deletion or regulation of the targeted pathogenic T cells in vivo. Longitudinal studies have established that TCV is safe and often results in a reduced relapse rate and clinical stability or improvement, at least temporarily, in the majority of treated MS patients. These results lend direct support to the involvement of inflammatory myelin-reactive T cells in the MS disease process. However, these hopeful trends reported in a number of pilot trials await validation in larger proof-of-principle trials that are now in progress.

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.

Multiple sclerosis patients show sexual dimorphism in cytokine responses to myelin antigens

Multiple sclerosis affects more women than men. The reasons for this are unknown. Previously, we have shown significant differences in women versus men in inflammatory cytokine responses to the major protein component of myelin, proteolipid protein (PLP), which is thought to be a target in MS patients. Here, using the ELISPOT assay, we examined sex differences in single-cell secretion of Th1 and Th2 cytokines from freshly isolated PBMC between relapsing remitting (RR) MS patients and healthy individuals. Cells were stimulated with MS-associated antigens including proteolipid protein (PLP), myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG), and non-disease related antigens. Our data show a sex bias in the cytokine responses to multiple MS-relevant myelin antigens: Women with MS show IFNgamma-skewed responses and men with MS show IL-5-skewed responses. These data extend our previous findings [Pelfrey, C.M., Cotleur, A.C., Lee, J.C., Rudick, R.A. 2002. Sex differences in cytokine responses to myelin peptides in multiple sclerosis. J. Neuroimmunol. 130, 211-223.]: (1) by demonstrating gender skewing in cytokine responses to an expanded myelin antigen repertoire, which includes MBP, MOG and PLP; (2) by showing TNFalpha and IL-10 do not display comparable gender skewing compared to IFNgamma and IL5; (3) by defining the patient population as early, untreated RRMS patients to avoid confounding factors, such as different disease stages/disability and immunomodulatory therapy; and (4) by showing HLA type does not appear to underlie the gender differences. These findings may explain increased susceptibility to MS in women and could contribute to the differences in disease severity between men and women.

Autoreactive CD8-specific T-cell response in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an autoimmune liver disease of unknown etiology. Autoimmune attack in PBC is predominantly organ-specific, despite the presence of mitochondrial autoantigens, the major targets of autoimmunity in PBC, in all nucleated cells. Cytotoxic T lymphocytes are thought to be directly involved in the tissue injury in PBC. The major histocompatibility complex (MHC) class I-restricted epitope for E2 components of pyruvate dehydrogenase complexes, namely amino acid 159-167, a region very close to the epitoperecognized by MHC class II-restricted CD4 cells and by antibody, has been characterized. In addition, there was a 10-fold increase in the frequency of autoreactive cytotoxic T lymphocytes in the liver as compared to the blood in PBC patients using tetramer technology.

The role of CD4 T cells in the pathogenesis of multiple sclerosis

T lymphocytes play a central role in the pathogenesis of multiple sclerosis (MS) (Zhang et al., 1992). Both CD4+ and CD8+ T cells have been demonstrated in MS lesions, with CD4+ T cells predominating in acute lesions and CD8+ T cells being observed more frequently in chronic lesions (Raine, 1994). Additionally, T cells are found in all four of the described histopathologic subtypes of MS (Lucchinetti et al., 2000). Activated myelin-reactive CD4+ T cells are present in the blood and cerebrospinal fluid (CSF) of MS patients; in contrast, only nonactivated myelin-reactive T cells are present in the blood of controls (Zhang et al., 1994). The success of several T-cell-targeted therapies in MS reinforces the importance of the role of the T cell in MS pathogenesis. Here, we outline basic concepts in CD4+ T-cell immunology and summarize the current understanding of the role of CD4+ T cells in the pathogenesis of MS.

Vaccination with selected synovial T cells in rheumatoid arthritis

OBJECTIVE

This pilot clinical study was undertaken to investigate the role of T cell vaccination in the induction of regulatory immune responses in patients with rheumatoid arthritis (RA).

METHODS

Autologous synovial T cells were selected for pathologic relevance, rendered inactive by irradiation, and used for vaccination. Fifteen patients received T cell vaccination via 6 subcutaneous inoculations over a period of 12 months.

RESULTS

T cell vaccination led to induction of CD4+ Tregs and CD8+ cytotoxic T cells specific for T cell vaccine. There was selective expansion of CD4+,V(beta)2+ Tregs that produced interleukin-10 (IL-10) and expressed a high level of transcription factor Foxp3, which coincided with depletion of overexpressed BV14+ T cells in treated patients. CD4+ IL-10-secreting Tregs induced by T cell vaccination were found to react specifically with peptides derived from IL-2 receptor alpha-chain. The expression level of Foxp3 in CD4+ T cells and increased inhibitory activity of CD4+,CD25+ Tregs were significantly elevated following T cell vaccination. The observed regulatory immune responses collectively correlated with clinical improvement in treated patients. In an intent-to-treat analysis, a substantial response, defined as meeting the American College of Rheumatology 50% improvement criteria, was shown in 10 of the 15 patients (66.7%) and was accompanied by a marked improvement in RA-related laboratory parameters.

CONCLUSION

These findings suggest that T cell vaccination induces regulatory immune responses that are associated with improved clinical and laboratory variables in RA patients.

Ozone exposure impairs antigen-specific immunity but activates IL-7-induced proliferation of CD4-CD8- thymocytes in BALB/c mice

It is well known that ozone (O3), a potent reactive oxidant and air pollutant, induces respiratory inflammation and hyperresponsiveness upon inhalation. It was previously shown that O3 exposure (0.6 ppm, 10 h/day for 15 days) not only results in local bronchial inflammation, but also affects the nervous system and thymocyte proliferation, and places mice under oxidative stress. In the present study, data showed that O3 exposure could impair both the natural killer (NK) cell activity and the proliferation potential of spleen T cells to a specific antigen stimulus. Immunological function assays indicated that O3 exposure attenuated the proliferation of spleen mononuclear cells induced by concanavalin A and decreased CD4+ and CD28+ lymphocyte subsets. However, supplementation with natural antioxidants protected mice from O3-induced dysfunction of splenocyte proliferation. Meanwhile, O3 exposure resulted in a decline of mitogen-induced IL-2 production in splenocytes. It was also found that O3 exposure dramatically enhanced the proliferation of CD4-CD8- thymocytes stimulated by recombinant mouse interleukin-7 (rmIL-7), which is usually observed during the mammal aging process. Taken together, data conclude that short-term repetitive O3 exposure damages both innate and acquired immunity via altering the lymphocyte subset and cytokine profile, and via impact on thymocyte early development. O3-induced oxidative damage is one of the key factors leading to immune dysfunction in this mouse model.

A new clinically relevant approach to expand myelin specific T cells

Human self-reactive T cells are potentially involved in many autoimmune diseases. Although ex vivo detection of self-reactive T cells is possible, exhaustive functional characterization of these cells is impeded by their low frequency. In vitro expansion of antigen (Ag) specific T cells is typically achieved by using autologous (fresh or frozen) irradiated peripheral blood mononuclear cells (PBMCs), EBV-immortalized B cells or dendritic cells in the presence of Ag. These approaches require a large blood volume. We explored a method successfully applied for tumor specific T cells using in vitro expanded autologous B cells. PBMCs were stimulated with irradiated CD40L-expressing fibroblasts and IL-4, resulting in an enriched population of B cell that expressed high levels of MHC and co-stimulatory molecules, essential hallmarks of antigen presenting cells (APCs). Expanded B cells were loaded with Ag, irradiated and then used as APCs to stimulate T cells. The specificity of T cell lines was assessed by comparing their proliferation and IFN-gamma secretion when cultured with antigen-loaded B cells vs. unloaded B cells. T cell lines exhibiting antigen-specific proliferation and/or IFN-gamma secretion were expanded. Using this method, MBP and MOG specific CD4(+) and CD8(+) T cell lines were obtained from multiple donors in comparable numbers to those obtained using the traditional approach (i.e. fresh PBMCs as APCs) and were kept in culture for many weeks. We have shown that myelin specific CD4(+) and CD8(+) T cells can be expanded from a relatively small volume of blood (50-100 ml) from multiple donors using expanded B cells as APCs.

Short communication: impairment of membrane markers on peripheral blood mononuclear cells and imbalance of cytokine secretion in the pathogenesis of multiple sclerosis active phases

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). In active disease, a transmigration of autoreactive T cells to myelin antigens recruited from the peripheral blood (PBMC) to the CNS occurs, and there these cells prolong their survival and contribute to the perpetuation of the inflammation. In the active local lesions of MS patients, these cells display activation and apoptosis surface markers and secrete a range of cytokines. The aim of this research is to study on PBMCs and in the serum of stable and active MS subjects (1) the behavior of the CD40/CD40L system and the consequent balance of Th1 and Th2 cytokines and (2) the apoptosis marker system CD95/CD95L and tumor necrosis factor (TNF)- binding receptors, TNFRI and TNFRII. A possible excess of activation marker expression affecting and driving Th1 cytokine production or a parallel impairment of apoptosis may contribute to MS relapses. Our results may indicate that a dysregulation of early activation and apoptosis receptor systems and a profound and complex imbalance of cytokine production occurred in the peripheral blood of MS patients. This impairment could account for active phases of the disease.

Cell-based gene therapy experiments in murine experimental autoimmune encephalomyelitis

With the ultimate goal of developing a novel treatment for multiple sclerosis (MS), we have developed a cell-based gene therapy protocol for the treatment of murine experimental autoimmune encephalomyelitis (EAE), a powerful animal model for MS. We have determined that transduced fibroblasts secreting encephalogenic epitopes, when injected into mice with EAE, cause a striking abrogation of disease. Both myelin basic protein (MBP) and proteolipid protein mini-gene constructs expressed in syngeneic fibroblast cells were capable of ameliorating ongoing EAE induced by MBP protein. These experiments are crucial since they suggest that not all encephalogenic epitopes need be secreted for the control of disease. We also demonstrate the success of this protocol when transduced syngeneic, and most importantly, allogeneic cells are sequestered within an implantable chamber. Furthermore, we find that through modifying antigen expression by changing the signal sequence of the mini-gene construct, we were able to significantly reduce the dose of cells required for treatment. These improvements to the mini-gene delivery system are critical for the eventual translation of our protocol to the clinic.

Systemic immunomodulation of autoimmune disease using MHC-derived recombinant TCR ligands

Human autoimmune disease involves local activation of antigen-specific CD4(+) T cells that produce inflammatory Th1 cytokines leading to the further recruitment and activation of lymphocytes and monocytes, resulting ultimately in the destruction of target tissue. Antigen presenting cells (APCs) initiate activation of CD4(+) T cells in a multistep process that minimally involves co-ligation of the TCR and CD4 by the MHC class II/peptide complex and costimulation through additional T cell surface molecules such as CD28. Disruption of this highly orchestrated series of events can result in the direct modulation of CD4(+) T cell behavior. The interaction between MHC and TCR holds unique promise as a focal point for therapeutic intervention in the pathology of CD4(+) T cell-mediated diseases, and MHC class II-derived Recombinant TCR Ligands ("RTLs") have emerged as a new class of therapeutics with potent clinical efficacy in a diverse set of animal models for multiple sclerosis. Here I review the systemic effect that RTL therapy has on the intact immune system and present an overview of a molecular mechanism by which RTL therapy could induce these systemic changes.

Identification of autoantigens in psoriatic plaques using expression cloning

To search for autoantigens in psoriatic plaques, we screened cDNA libraries of plaque epidermis with psoriatic serum samples. This approach has been highly successful in identifying tumor antigens, but has not been widely applied to autoimmune disease. We identified 11 autoantigens including three with prominent reactivity and plausible disease relevance. These are keratin 13 (K13), heterogeneous nuclear ribonucleoprotein-A1 (hnRNP-A1), and a previously uncharacterized protein, FLJ00294. Serum antibody screening for these demonstrated reactivity in 40%, 38%, and 27% of psoriasis patients, respectively. Most positive samples reacted with all three, and we found that this was due to cross-reactivity among them. Enzyme-linked immunospot assay (ELISPOT) analysis of psoriatic peripheral blood T cells confirmed that these autoantigens are also recognized by T cells. This demonstrates that this is a feasible method to identify autoantigens in an autoimmune target tissue, and suggests that these antigens warrant further study in psoriasis. Furthermore, but peripheral blood of normal controls reacted to these autoantigens with essentially the same frequencies as patients, suggesting that psoriatics may have not only an immune system which is capable of reacting to certain autoantigens, but also to a skin immunoregulatory alteration which allows this normal reactivity to develop into abnormal inflammation.

CD4 T-cell epitopes of human alpha B-crystallin

Of potential importance to multiple sclerosis (MS), oligodendroglial alpha B-crystallin is expressed and associated with the myelin sheath at the earliest stage of MS lesion development. We selected T-cell lines specific for human alpha B-crystallin from peripheral blood mononuclear cells (PBMC) of HLA-DR2 homozygous MS patients and found that the alpha B-crystallin-specific T-cells were CD4+ and restricted by DRB1*1501, and expressed Th1 cytokines. The CD4 T-cell epitopes of human alpha B-crystallin were determined by proliferation of alpha B-crystallin-specific T-cell lines to 17 20-mer synthetic overlapping peptides spanning the entire molecule of human alpha B-crystallin. It was found that the HLA-DR2 donor-derived alpha B-crystallin-specific T-cell lines proliferated to alpha B-crystallin peptides 21-40, 41-60, and to a lesser extent, 131-150. These T-cell proliferation responses were associated with intracellular expression of interleukin-2 (IL-2) and secretion of interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha). The amino acid sequences of these peptides were compatible with predicted HLA-DR2-restricted binding motifs. PBMC of an early active MS patient proliferated to the epitope-containing peptides significantly better than did those of later stage MS patients or healthy controls. Taken together, these findings suggest that autoreactive alpha B-crystallin-specific Th1 cells may have the potential to contribute to MS pathogenesis.

Ex vivo detection of myelin basic protein-reactive T cells in multiple sclerosis and controls using specific TCR oligonucleotide probes

T cell reactivity to candidate myelin autoantigens, such as myelin basic protein (MBP), may play an important role in the pathogenesis of multiple sclerosis (MS). Although MBP-reactive T cells have been found to undergo in vivo activation in patients with MS, their true precursor frequency in MS is unknown as current frequency analysis is commonly based on the T cell functional responses to MBP. In this study, we developed a TCR sequence-based ex vivo detection system using colony hybridization with oligonucleotide probes specific for CDR3 of selected T cell clones for the analysis of true T cell precursor frequency in PBMC. The results revealed that the precursor frequency of five independent T cell clones recognizing the immunodominant MBP(83-99) region was found to be in the range of 1.6 x 10(-4) in total T cells in three HLA-DR2 patients with MS compared to that of 0.25 x 10(-4) in HLA-DR2 healthy individuals. The observed frequency of MBP(83-99)-reactive T cells in MS patients was considerably higher than those measured in parallel by cell culture-based analysis (2.3 x 10(-6)) or by enzyme-linked immunospot assay (3.9 x 10(-5)) in the same peripheral blood mononuclear cell specimens. Furthermore, the study showed that MBP(83-99)-reactive T cells detected ex vivo belonged to CD45RA+, CD25+ and CD95- T cell subsets as evidenced by preferential expression of specific TCR transcripts in these cell fractions.

Antibodies to myelin basic protein, myelin oligodendrocytes peptides, alpha-beta-crystallin, lymphocyte activation and cytokine production in patients with multiple sclerosis

OBJECTIVE

To measure neurone-specific humoral and cellular immune parameters in MRI-positive patients with multiple sclerosis (MS).

BACKGROUND

It has been postulated from animal models for MS and in situ evidence in MS patients that antibodies, activated T cells and proinflammatory cytokines are involved in the destruction of myelin sheaths and loss of oligodendrocytes in active areas.

SUBJECTS AND METHODS

Blood samples were obtained from 20 healthy control subjects and 20 patients with abnormal MRI and clinical diagnosis of MS. Sera were tested for levels of IgG, IgM and IgA against myelin basic protein (MBP), myelin oligodendrocyte glycoprotein (MOG) peptides, and a small heat-shock protein, alpha-beta-crystallin. Lymphocytes were isolated and cultured in the presence or absence of MBP, MOG peptides and alpha-beta-crystallin, measured for stimulated T cells, cytokine production and compared with controls.

RESULTS

Patients with MS showed the highest levels of IgG, IgM or IgA antibodies against one or all three tested antigens. Moreover, in the presence of MBP, MOG peptides or alpha-beta-crystallin, a significant percent- age of lymphocytes from MS patients underwent blast transformation, which resulted in high levels of interferon gamma (IFN-gamma), tumour necrosis factor alpha (TNF-alpha) and tumour necrosis factor beta (TNF-beta) production. Sensitivity of these assays was 60-80% and specificity, 65-70%.

CONCLUSIONS

Detection of antibodies against MBP, MOG peptides, alpha-beta-crystallin, lymphocyte stimulation and production of proinflammatory cytokines in response to these antigens could be used as surrogate markers for the confirmation of MS diagnosis. A combination of antibodies, lymphocyte activation or cytokine production with abnormal MRI may significantly increase the sensitivity and specificity of MS diagnosis.

Interferon gamma responses to myelin peptides in multiple sclerosis correlate with a new clinical measure of disease progression

The relationship between autoreactivity to myelin antigens and disease progression in multiple sclerosis (MS) is not fully understood. We addressed this relationship by cross-sectionally comparing an objective measure of MS disability with immune cytokine responses to myelin proteins. The ELISPOT assay was used to determine the ex vivo interferon gamma (IFNgamma) and interleukin-10 (IL-10) production by peripheral blood mononuclear cells (PBMCs) in response to peptides spanning the entire proteolipid protein (PLP) and myelin basic protein (MBP) molecules in 20 patients with relapsing-remitting (RR) MS and 27 age- and sex-matched healthy controls. MS patients showed significantly higher MBP-induced IFNgamma responses and PLP-induced IL-10 responses compared with healthy controls. Using the Multiple Sclerosis Functional Composite (MSFC), a new multifactorial measure of disability, MS patients showed a significant correlation between the IFNgamma response to PLP peptides and MBP peptides, and disability. In contrast, in MS patients, there was no correlation between the MSFC and the response to unrelated control antigens or mitogens. These data show that myelin-specific T lymphocytes secreting the inflammatory cytokine IFNgamma correlate with functional impairment in MS, supporting an antigen-specific link between the immune response to myelin and disability in MS.

Fas expression on T cells and sFas in relapsing-remitting multiple sclerosis

OBJECTIVES

To investigate the proportions of peripheral blood CD4+/Fas+ and CD8+/Fas+ cells and serum sFas levels in relapsing-remitting multiple sclerosis (RRMS) patients with relapses (active RRMS), those without relapses (stable RRMS), and controls over 1 year.

MATERIAL AND METHODS

Sixteen RRMS patients and 10 controls were tested monthly. Cells were analyzed by dual immunofluorescence and the sFas levels by ELISA. There were 14 relapses which occurred 1223 days after the last control visits. The measurements performed at these visits in the active RRMS patients were considered as relapse-related, while the rest were regarded as relapse-unrelated.

RESULTS

In active RRMS patients the median of CD4+ Fas+ to total CD4+ and CD8+ Fas+ to total CD8+ from relapse-related measurements were higher than the median from relapse-unrelated measurements (P=0.003, 0.004, respectively). The median of CD4+ Fas+ to total CD4+ from relapse-unrelated measurements in active RRMS was higher compared with stable RRMS (P = 0.005) and controls (P = 0.004). The sFas level from relapse-unrelated measurements was also higher in active RRMS than in stable RRMS (P = 0.04) and in controls (P = 0.004).

CONCLUSIONS

We suggest that increased expression of Fas antigen on CD4+ subset and increased serum sFas level are valuable markers of clinical activity 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.

A new approach for evaluating antigen-specific T cell responses to myelin antigens during the course of multiple sclerosis

We used a flow cytometry assay to measure proliferation and cytokine production of self-antigen-specific T cells in individual patients during the clinical course of multiple sclerosis (MS). Myelin-associated oligodendrocytic basic protein (MOBP) was selected for proof of principles in the assay, along with myelin basic protein (MBP) to assess specific activated T cells in 10 MS patients over an 18-month period, in parallel with brain magnetic resonance imaging (MRI) scans and clinical rating scale. A positive correlation occurred between antigen-specific T cell proliferation and interferon-gamma production with clinical relapses and MRI lesion activity that was absent when the same patients were in remission.

Addressing parents' concerns: do vaccines cause allergic or autoimmune diseases?

Anecdotal case reports and uncontrolled observational studies in the medical literature claim that vaccines cause chronic diseases such as asthma, multiple sclerosis, chronic arthritis, and diabetes. Several biological mechanisms have been proposed to explain how vaccines might cause allergic or autoimmune diseases. For example, allergic diseases might be caused by prevention of early childhood infections (the "hygiene hypothesis"), causing a prolongation of immunoglobulin E-promoting T-helper cell type 2-type responses. However, vaccines do not prevent most common childhood infections, and large well-controlled epidemiologic studies do not support the hypothesis that vaccines cause allergies. Autoimmune diseases might occur after immunization because proteins on microbial pathogens are similar to human proteins ("molecular mimicry") and could induce immune responses that damage human cells. However, wild-type viruses and bacteria are much better adapted to growth in humans than vaccines and much more likely to stimulate potentially damaging self-reactive lymphocytes. Consistent with critical differences between natural infection and immunization, well-controlled epidemiologic studies do not support the hypothesis that vaccines cause autoimmunity. Flaws in proposed biological mechanisms that explain how vaccines might cause chronic diseases are consistent with the findings of many well-controlled large epidemiologic studies that fail to show a causal relationship.

Cross-reactivity with myelin basic protein and human herpesvirus-6 in multiple sclerosis

Viral infections are though to play an important role in the pathogenesis of multiple sclerosis (MS) potentially through molecular mimicry. An identical sequence was found in both myelin basic protein (MBP, residues 96-102), a candidate autoantigen for MS, and human herpesvirus-6 (HHV-6 U24, residues 4-10) that is a suspected viral agent associated with MS. In this study, we showed that greater than 50% of T cells recognizing MBP(93-105) cross-reacted with and could be activated by a synthetic peptide corresponding to residues 1 to 13 of HHV-6 U24 in MS patients. The estimated precursor frequency of these cross-reactive T cells recognizing both peptides, MBP(93-105) and HHV-6 (U24)(1-13), was significantly elevated in MS patients compared with that in healthy controls. These cross-reactive CD4+ T cells represented the same Th1 phenotype as that of monospecific T cells recognizing MBP(93-105). There were increased antibody titers for both peptide HHV-6 (U24)(1-13) and peptide MBP(93-105) in the same patients with MS compared with those in healthy controls, suggesting B-cell sensitization to the antigens in MS patients. The study provides important evidence in the understanding of the potential role of HHV-6 infection/reactivation in the activation of autoimmune reactivity to MBP and its implication in the pathogenesis of MS.

T cell vaccination in multiple sclerosis patients with autologous CSF-derived activated T cells: results from a pilot study

Myelin-reactive T cells are considered to play an essential role in the pathogenesis of multiple sclerosis (MS), an autoimmune disease of the central nervous system. We have previously studied the effects of T cell vaccination (TCV), a procedure by which MS patients are immunized with attenuated autologous myelin basic protein (MBP)-reactive T cell clones. Because several myelin antigens are described as potential autoantigens for MS, T cell vaccines incorporating a broad panel of antimyelin reactivities may have therapeutic effects. Previous reports have shown an accumulation of activated T cells recognizing multiple myelin antigens in the cerebrospinal fluid (CSF) of MS patients. We conducted a pilot clinical trial of TCV with activated CD4+ T cells derived from CSF in five MS patients (four RR, one CP) to study safety, feasibility and immune effects of TCV. CSF lymphocytes were cultured in the presence of rIL-2 and depleted for CD8 cells. After 5-8 weeks CSF T cell lines (TCL) were almost pure TCR alpha beta+CD4+ cells of the Th1/Th0 type. The TCL showed reactivity to MBP, MOG and/or PLP as tested by Elispot and had a restricted clonality. Three immunizations with irradiated CSF vaccines (10 million cells) were administered with an interval of 2 months. The vaccinations were tolerated well and no toxicity or adverse effects were reported. The data from this small open-label study cannot be used to support efficacy. However, all patients remained clinically stable or had reduced EDSS with no relapses during or after the treatment. Proliferative responses against the CSF vaccine were observed in 3/5 patients. Anti-ergotypic responses were observed in all patients. Anti-MBP/PLP/MOG reactivities remained low or were reduced in all patients. Based on these encouraging results, we recently initiated a double-blind placebo-controlled trial with 60 MS patients to study the effects of TCV with CSF-derived vaccines in early RR MS patients.

Insights into the immunopathogenesis of multiple sclerosis

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system (CNS). Significant progress has been made in our understanding of the etiology of MS. MS is widely believed to be an autoimmune disease that results from aberrant immune responses to CNS antigens. T cells are considered to be crucial in orchestrating an immunopathological cascade that results in damage to the myelin sheath. This review summarizes the currently available data supporting the idea that myelin reactive T cells are actively involved in the immunopathogenesis of MS. Some of the therapeutic strategies for MS are discussed with a focus on immunotherapies that aim to specifically target the myelin reactive T cells.

The human T cell response to myelin oligodendrocyte glycoprotein: a multiple sclerosis family-based study

Myelin oligodendrocyte glycoprotein (MOG) is an encephalitogenic myelin protein and a likely autoantigen in human multiple sclerosis (MS). In this work, we describe the fine specificity and cytokine profile of T cell clones (TCC) directed against MOG in three nuclear families, comprised of four individuals affected with MS and their HLA-identical siblings. TCC were generated from PBMC by limiting dilution against a mixture of eleven 20-mer overlapping peptides corresponding to the encephalitogenic extracellular domain of human MOG (aa 1-120). The frequency of MOG peptide-reactive T cells was surprisingly high (range, 1:400 to 1:3,000) and, unexpectedly, cloning efficiencies were highest at low seeding densities of 10(2) or 10(3) PBMC per well. A total of 235 MOG peptide-reactive TCC were produced, all of which were CD4(+)CD8(-)TCRalphabeta(+)TCRgammadelta(-). All 11 MOG peptides were recognized by the TCC, and different epitopes of MOG appeared to be immunodominant in the HLA-identical siblings. The patterns of cytokine secretion by TCC from single individuals were generally similar. The healthy individuals exhibited Th2-, Th0-, and T regulatory cell 1-like cytokine profiles, whereas TCC from one sibling with MS had a striking Th1-like phenotype, producing high levels of IFN-gamma and TNF-alpha, and low IL-4 levels. Thus, MOG-reactive T cells appear to constitute an important part of the natural T cell repertoire, a finding that could contribute to the development of autoimmunity to this protein.

Quantitative and functional analysis of PDC-E2-specific autoreactive cytotoxic T lymphocytes in primary biliary cirrhosis

While the pathologic mechanisms responsible for organ-specific tissue damage in primary biliary cirrhosis (PBC) remain an enigma, it has been suggested that the pathology is mediated by autoreactive T cells infiltrating the intrahepatic bile ducts. Previously, we have documented that there is 100-fold enrichment in the frequency of CD4(+) autoreactive T cells in the liver that are specific for peptides encoded by the E2 components of the pyruvate dehydrogenase complexes (PDC-E2). We have also recently characterized the first MHC class I-restricted epitope for PDC-E2, namely amino acid 159-167, a region very similar to the epitope recognized by MHC class II-restricted CD4(+) cells and by autoantibodies. The effector functions of these PDC-E2(159-167)-specific CD8(+) cytotoxic T lymphocytes (CTLs) are not well understood. We have taken advantage of tetramer technology and report herein that there is tenfold increase in the frequency of PDC-E2(159-167)-specific CTLs in the liver as compared with the blood in PBC. In addition, the precursor frequency of the CTLs in blood was significantly higher in early-stage PBC. Of interest was the fact that, upon stimulation with the peptide, the response of PDC-E2(159-167) tetramer-positive cells is heterogeneous with respect to IFN-gamma synthesis. These data, we believe for the first time, document the enrichment of autoantigen-specific CD8(+) T cells in the PBC liver, suggesting that CD8(+) T cells play a significant role in the immunopathogenesis of PBC.

Frequency, heterogeneity and encephalitogenicity of T cells specific for myelin oligodendrocyte glycoprotein in naive outbred primates

Auto-reactive T cells present in healthy subjects remain in a state of unresponsiveness, but may trigger autoimmunity under various situations. Although myelin oligodendrocyte glycoprotein (MOG) is a potential target antigen in multiple sclerosis (MS), MOG-reactive T cell responses are present in the blood of both healthy subjects and MS-affected individuals. To investigate the disease-inducing potential and regulation of these autoreactive T cells in healthy outbred populations, we have characterized MOG-reactive T cell clones obtained by limiting dilution from peripheral blood of unimmunized C. jacchus marmosets. We report an extraordinarily high prevalence of circulating MOG-reactive T cells in these naive animals (2.6 +/- 1.4 / 10(5) PBMC), and a broadly diverse repertoire of epitope recognition encompassing at least three regions within the extracellular domain of MOG. Adoptive transfer of a MOG21-40-specific T cell clone resulted in mild clinical experimental allergic encephalomyelitis, characterized pathologically by rare foci of inflammation and minimal demyelination. We conclude that MOG-reactive T cells are present in healthy primates at a highly prevalent frequency, and are potentially capable of triggering central nervous system autoimmunity. Expansion of these autoreactive T cells must be tightly controlled to maintain immune homeostasis in healthy individuals.

TCR peptide therapy in human autoimmune diseases

Inflammatory Th1 cells reacting to tissue/myelin derived antigens likely contribute to the pathogenesis of diseases such as multiple sclerosis (MS), rheumatoid arthritis (RA), and psoriasis. One regulatory mechanism that may be useful for treating autoimmune diseases involves an innate second set of Th2 cells specific for portions of the T cell receptor of clonally expanded pathogenic Th1 cells. These Th2 cells are programmed to respond to internally modified V region peptides from the T cell receptor (TCR) that are expressed on the Th1 cell surface in association with major histocompatibility molecules. Once the regulatory Th2 cells are specifically activated, they may inhibit inflammatory Th1 cells through a non-specific bystander mechanism. A variety of strategies have been used by us to identify candidate disease-associated TCR V genes present on pathogenic Th1 cells, including BV5S2, BV6S5, and BV13SI in MS, BV3, BV14, and BV17 in RA, and BV3 and BV13S1 in psoriasis. TCR peptides corresponding to the mid region of these BV genes were found to be consistently immunogenic in vivo when administered either i.d. in saline or i.m. in incomplete Freund's adjuvant (IFA). In MS patients, repeated injection of low doses of peptides (100-300 microg) significantly boosted the number of TCR-reactive Th2 cells. These activated cells secreted cytokines, including IL-10, that are known to inhibit inflammatory Th1 cells. Cytokine release could also be induced in TCR-reactive Th2 cells by direct cell-cell contact with Th1 cells expressing the target V gene. These findings indicate the potential of regulatory Th2 cells to inhibit not only the target Th1 cells, but also bystander Th1 cells expressing different V genes specific for other autoantigens. TCR peptide vaccines have been used in our studies to treat a total of 171 MS patients (6 trials), 484 RA patients (7 trials), and 177 psoriasis patients (2 trials). Based on this experience in 824 patients with autoimmune diseases, TCR peptide vaccination is safe and well tolerated, and can produce significant clinical improvement in a subset of patients that respond to immunization. TCR peptide vaccination represents a promising approach that is well-suited for treating complex autoimmune diseases.

Reactivity pattern and cytokine profile of T cells primed by myelin peptides in multiple sclerosis and healthy individuals

Autoreactive T cells specific for candidate myelin antigens, including myelin basic protein (MBP) and proteolipid protein (PLP), are thought to play an important role in the pathogenesis of multiple sclerosis (MS). Myelin-reactive T cells primed in vivo by myelin breakdown products or microbial cross-reactive antigens during the disease processes may exhibit a reactivity pattern and cytokine profile different from those in the normal T cell repertoire. In this study, we examined the precursor frequency, the reactivity pattern and cytokine profile of myelin-reactive T cells that were primed in vitro with overlapping peptides of MBP and PLP in patients with MS and healthy individuals. The results revealed that T cells specific for peptides of MBP and PLP occurred at a relatively higher precursor frequency in patients with MS than that in healthy individuals. We identified a number of dominant T cell epitopes within MBP and PLP, some of which were not previously detected using whole myelin antigens as the primary stimuli. Some residues represented common immunodominant regions that were detected in both MS patients and healthy controls while others were associated only with MS. MBP-reactive T cell lines generally exhibited a Th0-like cytokine profile. There was significantly increased Th1 cytokine production (i. e. TNF and IFN-gamma) among MS-derived T cell lines. PLP-reactive T cell lines had a distinct cytokine profile, producing predominantly TNF-alpha and little or not IFN-gamma and IL-4. The findings have important implications in the understanding of the role of myelin-reactive T cells in MS.

Effective antigen-specific immunotherapy in the marmoset model of multiple sclerosis

Mature T cells initially respond to Ag by activation and expansion, but high and repeated doses of Ag cause programmed cell death and can suppress T cell-mediated diseases in rodents. We evaluated repeated systemic Ag administration in a marmoset model of experimental allergic encephalomyelitis that closely resembles the human disease multiple sclerosis. We found that treatment with MP4, a chimeric, recombinant polypeptide containing human myelin basic protein and human proteolipid protein epitopes, prevented clinical symptoms and did not exacerbate disease. CNS lesions were also reduced as assessed in vivo by magnetic resonance imaging. Thus, specific Ag-directed therapy can be effective and nontoxic in primates.