Virus-reactive and autoreactive T cells are accumulated in cerebrospinal fluid in multiple sclerosis

Animal models of Multiple Sclerosis

Multiple Sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) which involves a complex interaction between immune system and neural cells. Animal modeling has been critical for addressing MS pathogenesis. The three most characterized animal models of MS are (1) the experimental autoimmune/allergic encephalomyelitis (EAE); (2) the virally-induced chronic demyelinating disease, known as Theiler׳s murine encephalomyelitis virus (TMEV) infection and (3) the toxin-induced demyelination. All these models, in a complementary way, have allowed to reach a good knowledge of the pathogenesis of MS. Specifically, EAE is the model which better reflects the autoimmune pathogenesis of MS and is extremely useful to study potential experimental treatments. Furthermore, both TMEV and toxin-induced demyelination models are suitable for characterizing the role of the axonal injury/repair and the remyelination process in MS. In conclusion, animal models, despite their limitations, remain the most useful instrument for implementing the study of MS.

Oral Administration of Lactococcus lactis Expressing Synthetic Genes of Myelin Antigens in Decreasing Experimental Autoimmune Encephalomyelitis in Rats

Background

Multiple sclerosis is a human autoimmunological disease that causes neurodegeneration. One of the potential ways to stop its development is induction of oral tolerance, whose effect lies in decreasing immune response to the fed antigen. It was shown in animal models that administration of specific epitopes of the three main myelin proteins – myelin oligodendrocyte glycoprotein (MOG), myelin basic protein (MBP), and proteolipid protein (PLP) – results in induction of oral tolerance and suppression of disease symptoms. Use of bacterial cells to produce and deliver antigens to gut mucosa seems to be an attractive method for oral tolerance induction in treatment of diseases with autoimmune background.

Material/Methods

Synthetic genes of MOG35-55, MBP85-97, and PLP139-151 myelin epitopes were generated and cloned in Lactococcus lactis under a CcpA-regulated promoter. The tolerogenic effect of bacterial preparations was tested on experimental autoimmune encephalomyelitis, which is the animal model of MS. EAE was induced in rats by intradermal injection of guinea pig spinal cord homogenate into hind paws.

Results

Rats were administered preparations containing whole-cell lysates of L. lactis producing myelin antigens using different feeding schemes. Our study demonstrates that 20-fold, but not 4-fold, intragastric administration of autoantigen-expressing L. lactis cells under specific conditions reduces the clinical symptoms of EAE in rats.

Conclusions

The present study evaluated the use of myelin antigens produced in L. lactis in inhibiting the onset of experimental autoimmune encephalomyelitis in rats. Obtained results indicate that application of such recombinant cells can be an attractive method of oral tolerance induction.

Modeling the heterogeneity of multiple sclerosis in animals

Multiple sclerosis (MS) is an inflammatory, demyelinating disease of the central nervous system (CNS) manifested with varying clinical course, pathology, and inflammatory patterns. There are multiple animal models that reflect different aspects of this heterogeneity. Collectively, these models reveal a balance between pathogenic and regulatory CD4(+) T cells, CD8(+) T cells, and B cells that influences the incidence, timing, and severity of CNS autoimmunity. In this review we discuss experimental autoimmune encephalomyelitis (EAE) models that have been used to study the pathogenic and regulatory roles of these immune cells; models that recapitulate different aspects of the disease seen in patients with MS, and questions remaining for future studies.

Detection of mumps virus RNA in cerebrospinal fluid of patients with neuromyelitis optica

Neuromyelitis optica (NMO) is an acute inflammatory disease that preferentially involves the optic nerves and spinal cord. Although many infectious agents, including mumps virus, are postulated to have a role in the pathogenesis of multiple sclerosis (MS), the relationship between NMO and infectious agents remains uncertain. To investigate the relationship between NMO and viruses that have special affinity for the central nervous system, we performed a nested polymerase chain reaction (PCR) to detect mumps virus or enterovirus RNA in cerebrospinal fluid samples from 13 patients with MS, 8 with NMO and 20 with other neurological diseases (ONDs). Nested PCR was positive for mumps virus in 2 (25%) of NMO patients, but in none of those with MS and ONDs. Moreover, nested PCR results became negative in the remission phase in the two PCR-positive NMO patients. Mumps virus may have some role in the pathogenesis of NMO.

Antiviral immune responses: triggers of or triggered by autoimmunity?

The predisposition of individuals to several common autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus and multiple sclerosis, is genetically linked to certain human MHC class II molecules and other immune modulators. However, genetic predisposition is only one risk factor for the development of these diseases, and low concordance rates in monozygotic twins, as well as the geographical distribution of disease risk, suggest the involvement of environmental factors in the development of these diseases. Among these environmental factors, infections have been implicated in the onset and/or promotion of autoimmunity. In this Review, we outline the mechanisms by which viral infection can trigger autoimmune disease and describe the pathways by which infection and immune control of infectious disease might be dysregulated during autoimmunity.

The MSMV hypothesis: measles virus and multiple sclerosis, etiology and treatment

Multiple sclerosis (MS) is a progressive disease characterised by periods of quiescence and exacerbation. It is found more often in northern and southern climates, rather than those closer to the equator, where it is especially rare, and, therefore, cannot be considered as an autoimmune disease. We present the MSMV Hypothesis, involving novel ideas which encompass an understanding of the blood brain barrier (BBB) function, the lymphocyte population, together with the viral presence in the CNS of what we are calling the multiple sclerosis measles virus (MSMV) that is the immediate cause of MS, and which exhibits a similar immunologic response of the systemic virus. We assume that the geographical distribution of MS is related to MSMV's sensitivity to ultraviolet light and that it is feasible to assume a viral etiology for MS based on this. The methodology employed is eclectic and grounded on several differing approaches: involved are the meta-analyses of two comprehensive studies on the effects of azathioprine in the treatment of a large number of MS patients undertaken since the early 1990s, a pioneering pilot study that examined the effects of azathioprine treatment on a smaller set of patients in the late 1960s; and, finally, we also outline the results of several experiments in cell culture on two MV strains using a new drug lead that has been shown to effectively stave off the progression of MS by interfering with the normal replication process of the MSMV. In the latter case, strain Edmonston (MV-E) was employed, along with strain Halle (MV-H), which was obtained from a lymph node of a patient with subacute sclerosing panencephalitis (SSPE), which mimics various aspects of the pathology of neurological diseases, including demyelination. An analogue of a metabolite of azathioprine (ESP) was evaluated for antiviral activity against these two viral strains. The results proved positive for the MV-H infected cells as syncytia formation was reduced in a dose-dependent manner, and under protocols which avoided toxic effects, following ESP treatment ranging from 66% with 1 microg/ml and to 25% with 0.1 microg/ml. Since ESP is an analogue of the active metabolite of azathioprine, which exhibits positive outcomes when administered to MS patients, we submit that this metabolite is acting on MSMV, in a similar fashion to the action of ESP on MV-H.

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.

Gene expression profiles in Finnish twins with multiple sclerosis

Background

Since genetic alterations influencing susceptibility to multiple sclerosis (MS), the most common autoimmune demyelinating disease of the central nervous system (CNS), are as yet poorly understood, the purpose of this study was to identify genes responsible for MS by studying monozygotic (MZ) twin pairs discordant for MS.

Methods

In order to identify genes involved in MS development, the gene expression profiles in blood mononuclear cells obtained from eight MZ twin pairs discordant for MS were analyzed by cDNA microarray technology detecting the expression of 8 300 genes. The twins were collected from the Finnish Twin Cohort Study and both affected subjects and their healthy siblings underwent neurological evaluation and cerebral and spinal magnetic resonance imaging. Gene expressions were confirmed by relative quantitative reverse transcription PCR.

Results

It appeared that 25 genes were at least two-fold up-regulated and 15 genes down-regulated in 25% (2/8) of twins with MS when compared to their healthy siblings. Moreover, 6/25 genes were up-regulated in 40% of MS twins and one gene, interferon alpha-inducible protein (clone IFI-6-16) (G1P3), in 50% of them. The six most constantly expressed genes are (1) G1P3, (2) POU domain, class 3, transcription factor 1, (3) myxovirus resistance 2, (4) lysosomal-associated multispanning membrane protein-5, (5) hemoglobin alpha 2 and (6) hemoglobin beta.

Conclusion

Over two-fold up-regulation of these six genes in almost half of MZ twins with MS suggests their role in MS pathogenesis. Studies using MZ MS twins obtained from genetically homogeneous population offer a unique opportunity to explore the genetic nature of MS.

Morbilliviruses and human disease

Morbilliviruses are a group of viruses that belong to the family Paramyxoviridae. The most instantly recognizable member is measles virus (MV) and individuals acutely infected with the virus exhibit a wide range of clinical symptoms ranging from a characteristic mild self-limiting infection to death. Canine distemper virus (CDV) and rinderpest virus (RPV) cause a similar but distinctive pathology in dogs and cattle, respectively, and these, alongside experimental MV infection of primates, have been useful models for MV pathogenesis. Traditionally, viruses were identified because a distinctive disease was observed in man or animals; an infectious agent was subsequently isolated, cultured, and this could be used to recapitulate the disease in an experimentally infected host. Thus, satisfying Koch's postulates has been the norm. More recently, particularly due to the advent of exceedingly sensitive molecular biological assays, many researchers have looked for infectious agents in disease conditions for which a viral aetiology has not been previously established. For these cases, the modified Koch's postulates of Bradford Hill have been developed as criteria to link a virus to a specific disease. Only in a few cases have these conditions been fulfilled. Therefore, many viruses have over the years been definitely and tentatively linked to human diseases and in this respect the morbilliviruses are no different. In this review, human diseases associated with morbillivirus infection have been grouped into three broad categories: (1) those which are definitely caused by the infection; (2) those which may be exacerbated or facilitated by an infection; and (3) those which currently have limited, weak, unsubstantiated or no credible scientific evidence to support any link to a morbillivirus. Thus, an attempt has been made to clarify the published data and separate human diseases actually linked to morbilliviruses from those that are merely anecdotally associated.

Autoreactivity against induced or upregulated abundant self-peptides in HLA-A*0201 following measles virus infection

Infectious agents have been implied as causative environmental factors in the development of autoimmunity. However, the exact nature of their involvement remains unknown. We describe a possible mechanism for the activation of autoreactive T cells induced by measles virus (MV) infection. The display of HLA-A*0201 associated peptides obtained from MV infected cells was compared with that from uninfected cells by mass spectrometry. We identified two abundant self peptides, IFI-6-16(74-82) and Hsp90beta(570-578), that were induced or upregulated, respectively, following infection. Their parental proteins, the type I interferon inducible protein IFI-6-16, and the beta chain of heat shock protein 90, have not been involved in MV pathogenesis. MV infection caused minor and major changes in the intracellular expression patterns of these proteins, possibly leading to altered peptide processing. CD8+ T cells capable of recognizing the self-peptides in the context of HLA-A*0201 were detectable at low basal levels in the neonatal and adult human T cell repertoire, but were functionally silent. In contrast, peptide-specific producing IFN-gamma producing effector cells were present in MV patients during acute infection. Thus, MV infection induces an enhanced display of self-peptides in MHC class I, which may lead to the temporary activation of autoreactive T cells.

Application of tetramer technology in studies on autoimmune diseases

Autoreactive T cells are thought to play a role in the immunopathogenesis of autoimmune diseases. Analysis of such cells had long been hampered by lack of suitable assays. Recently developed tetramer technology is based on the recognition of specific peptide-MHC complex by T cell receptor and on the increased binding affinity of multimerized peptide-MHC complex. MHC class I and class II tetramers can be used to detect autoreactive CD4(+) and CD8(+) T cells, while nonclassical MHC (such as CD1d) tetramer can be used to detect other T cell groups, for example natural killer T cells. Tetramer technologies enable direct quantitation of autoreactive T cells in blood and affected tissues. It is also possible to carry out phenotypic and functional characterization of specific T cells on a single cell basis by using tetramers. Of special interest, in situ tetramer staining has the great potential of analyzing autoreactive T cells in their cellular environments. Utilization of tetramers in studies of autoreactive T cells is expected to generate important information regarding the role of such cells in the underlying mechanisms of autoimmune diseases.

Cytokines in multiple sclerosis: methodological aspects and pathogenic implications

Multiple sclerosis (MS) is one of the leading causes of disability among young adults of Caucasian origin. One hundred and fifty years after the first description of the disease, the cause of MS remains unknown. Ironically, the few hypotheses concerning MS pathogenesis that are valid today were first proposed over a hundred years ago. However, equipped with the advanced technology of molecular biology and imaging systems, we are at present progressively uncovering dues to understanding the pathogenesis of the disease. It is dearly evident that aberrant immune responses occur in MS, and it is likely that the spectrum of cytokines produced decisively influences disease outcome. The detrimental consequences of IFN-gamma and the beneficial effects of IFN-beta treatment in MS support this hypothesis. However, there are still major gaps in our knowledge of the involvement of cytokines in MS. Numerous studies have addressed the question of cytokine levels in MS, often with conflicting results; elevated, normal and decreased levels of almost all cytokines have been reported. This scenario most probably reflects methodological dilemmas as well as the complex biology of cytokines. Here we focus on possible reasons for the discrepancies of results reported on cytokines in MS and summarize findings obtained in particular by the application of enzyme-linked immunospot (ELISPOT) assays to cytokine studies in MS.

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.

Multiple MAG peptides are recognized by circulating T and B lymphocytes in polyneuropathy and multiple sclerosis

Abnormal immune responses to myelin associated glycoprotein (MAG), a component of myelin of the central and peripheral nervous system, have been suggested to play a role in the pathogenesis of multiple sclerosis (MS) and certain types of inflammatory polyneuropathy. To identify possible immunodominant MAG peptides in neuroinflammation, we examined T and B cell responses to five selected synthetic MAG peptides and myelin proteins in 21 patients with non-inflammatory polyneuropathy, 26 patients with MS, 10 optic neuritis patients and 17 healthy subjects. Enzyme-linked immunosorbent spot-forming cell assays were adopted, allowing the detection and enumeration of individual antigen responsive T and B cells in body fluids. Patients with polyneuropathy as well as those with MS had elevated levels of T and B cells recognizing MAG and its peptides. Any of the five MAG peptides under study functioned as immunodominant T and/or B cell epitope in individual subjects. None of the MAG peptides elicited a specific disease-associated T or B cell response. The enhanced T and B cell response to myelin components like MAG may play some role in initiation and/or progression of these diseases, but they could also represent secondary responses associated with myelin damage and indicate tolerization rather than autoaggressive immunity.

Identification of single nucleotide variations in the coding and regulatory regions of the myelin-associated glycoprotein gene and study of their association with multiple sclerosis

The myelin-associated glycoprotein (MAG) gene is an appealing candidate in the 19q13 Multiple Sclerosis (MS) candidate region. Using denaturing high performance liquid chromatography (DHPLC), we identified 14 single nucleotide polymorphisms (SNPs) in MAG coding and regulatory regions, and we tested their possible association with MS in Italian patient and control DNA pools. Eight variations had a frequency <0.05, i.e. below the detection limit in the pools. Of these, Arg537Cys was further studied with individually genotyped individuals and was detected in 1/189 patients and 0/85 controls. The frequency of the six remaining SNPs were not significantly different in pools including a total of 1266 patient and 1612 control chromosomes. Considering the statistical power of the experimental design, these results exclude the MAG gene as an MS susceptibility factor with an odds ratio (OR) equal or higher than 1.3.

Multiple sclerosis and Kaposi's sarcoma--chronic diseases associated with new human herpesviruses?

Two diseases that for many years have been suspected to be of viral origin are multiple sclerosis (MS) and Kaposi's sarcoma (KS). With the use of a new technique called representational difference analysis both these diseases have recently been associated with new lymphotropic herpesviruses, i.e. human herpesviruses (HHV) 6 and 8. HHV-6 is a ubiquitous virus and the etiological agent of exanthema subitum. Viral neuroinvasion occurs frequently in primary HHV-6 infection, and meningitis, encephalitis and demyelination have been described as rare complications. A relation with MS has been suggested for HHV-6, as the virus has been detected in MS plaques in the brain. Data from different studies are, however, conflicting and a definitive role for HHV-6 in MS pathogenesis has not been established. HHV-8 is believed to be the causative agent of KS, and is also associated with some rare hematological malignancies. The viral genome contains several potential oncogenes that are believed to have been picked up from the human genome during evolution. The role of HHV-8 in healthy, immunocompetent individuals is however uncertain. In conclusion, the full spectrum of human diseases associated with these new viruses is not yet understood, and rapid developments in molecular biology will continue to shed new light on the interactions between herpesviruses and their hosts.

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.

Quantification of self-recognition in multiple sclerosis by single-cell analysis of cytokine production

Identifying and quantifying autoaggressive responses in multiple sclerosis (MS) has been difficult in the past due to the low frequency of autoantigen-specific T cells, the high number of putative determinants on the autoantigens, and the different cytokine signatures of the autoreactive T cells. We used single-cell resolution enzyme-linked immunospot (ELISPOT) assays to study, directly ex vivo, proteolipid protein (PLP)-specific memory cell reactivity from MS patients and controls. Overlapping 9-aa-long peptides, spanning the entire PLP molecule in single amino acid steps, were used to determine the frequency and fine specificity of PLP-specific lymphocytes as measured by their IFN-gamma and IL-5 production. MS patients (n = 22) responded to 4 times as many PLP peptides as did healthy controls (n = 22). The epitopes recognized in individual patients, up to 22 peptides, were scattered throughout the PLP molecule, showing considerable heterogeneity among MS patients. Frequency measurements showed that the number of PLP peptide-specific IFN-gamma-producing cells averaged 11 times higher in MS patients than in controls. PLP peptide-induced IL-5-producing T cells occurred in very low frequencies in both MS patients and controls. This first comprehensive assessment of the anti-PLP-Th1/Th2 response in MS shows a greatly increased Th1 effector cell mass in MS patients. Moreover, the highly IFN-gamma-polarized, IL-5-negative cytokine profile of the PLP-reactive T cells suggests that these cells are committed Th1 cells. The essential absence of uncommitted Th0 cells producing both cytokines may explain why therapeutic strategies that aim at the induction of immune deviation show little efficacy in the established disease.

The central nervous system-specific myelin oligodendrocytic basic protein (MOBP) is encephalitogenic and a potential target antigen in multiple sclerosis (MS)

Uncovering primary target antigens in multiple sclerosis (MS) is of major significance for understanding the etiology and pathophysiology of the disease, and for designing immunospecific therapy. In this study, a synthetic peptide representing a predicted T cell epitope on myelin oligodendrocytic basic protein (MOBP) was found to be encephalitogenic in C3H.SW mice, inducing experimental autoimmune encephalomyelitis with an abrupt onset. Two separate preliminary studies with MOBP peptides indicated that autoreactivity to MOBP occurs in MS. These data strongly suggest that MOBP is a highly relevant target in MS and further point to the complexity of antigen specificities in MS.

Dendritic cells in experimental allergic encephalomyelitis and multiple sclerosis

The mechanisms by which autoimmune diseases are triggered and by which the activation of autoreactive T cells is initiated and maintained are not yet fully understood. As the most potent antigen presenting cells (APC), and also being responsible for antigen transport as well as primary sensitisation of T cells, dendritic cells (DC) are capable of breaking the state of self-ignorance and inducing aggressive autoreactive T cells. In the development of autoimmune diseases, different types of DC exhibit distinct properties for inducing Th1/Th2 cell responses. Appropriate cytokines can convert immunogenic DC to tolerogenic DC. Utilizing the possibility to promote the tolerogenic effects of DC, a new therapeutic tool might soon become available to treat multiple sclerosis and other autoimmune diseases.

Candidate autoantigens in multiple sclerosis

Multiple sclerosis is an inflammatory demyelinating CNS disease of putatively autoimmune origin. Novel models of experimental autoimmune encephalomyelitis (EAE) have demonstrated that T cells specific for various myelin and even nonmyelin proteins are potentially encephalitogenic. The encephalitogenic T cell response directed against different CNS antigens not only determines the lesional topography of CNS inflammation but also the composition of the inflammatory infiltrates. The heterogeneity of the lesional distribution seen in EAE might therefore be useful for the understanding of the various clinical subtypes seen in MS. In this review the possible candidate autoantigens in MS are discussed with special regard to the human T cell and B cell responses against various myelin and nonmyelin proteins.

Immunopathogenesis of multiple sclerosis: the role of T cells

Multiple sclerosis is considered to be an autoimmune disease that results from aberrant immune responses to central nervous system antigens. T cells are considered to be crucial in orchestrating an immunopathological cascade that culminates in damage to the myelin sheath, oligodendrocytes and axons.

Encephalitogenic and neuritogenic T cell responses to the myelin-associated glycoprotein (MAG) in the Lewis rat

Autoimmune responses to the myelin-associated glycoprotein (MAG) are implicated in the immunopathogenesis of both multiple sclerosis (MS) and certain peripheral neuropathies. In this study we demonstrate that T cell responses to defined epitopes of MAG mediate a pathological inflammatory response in the nervous system of the Lewis rat. Peptide-specific T cells were generated against four different MAG epitopes, three of which are common to both L- and S-isoforms of MAG (amino acid (a.a.) sequence: 20-34, 124-137, 354-377) whilst the fourth epitope (a.a. sequence: 570-582) is located in the C-terminal sequence of S-MAG. The adoptive transfer of T cells specific for these epitopes initiated a mild but dose-dependent inflammatory response in the central nervous system (CNS) of naive recipients. Clinical disease was only observed in those animals injected with T cells specific for the a.a. sequence 20-34 (MP1.1), which also initiated an inflammatory response in the peripheral nervous system (PNS). Co-transfer of MP1.1 (a.a. sequence 20-34)-specific T cells with the myelin oligodendrocyte glycoprotein (MOG)-specific monoclonal antibody 8-18C5 enhanced disease severity and induced widespread demyelination in the CNS. In contrast, co-transfer of T cells with the MAG-specific mAb 513 failed to induce demyelination, but had a moderate effect on the local inflammatory response. The ability of MAG to initiate an autoaggressive T cell response in the Lewis rat supports the concept that MAG-specific autoimmune responses may play a role in the pathogenesis of immune mediated diseases of the nervous system in man.

Cytokine flow cytometry differentiates the clinical status of multiple sclerosis (MS) patients

In this study we have examined intracellular cytokines in peripheral blood mononuclear cells (PBMC) of MS patients by flow cytometry (cytokine flow cytometry). MS progressive patients showed an increased number of cells producing interferon-gamma (IFN-gamma) after activation with phorbol 12-myristate 13-acetate and ionomycin, compared with patients with clinically inactive forms (P < 0001) and with healthy controls (P = 0001). These cells belonged to the CD4+ and CD8+ subsets in similar proportions. Clinically inactive patients showed a lower level of cells producing IL-2 than controls (P = 0.03) and active MS patients (P = 0.03). Most IL-2-producing cells were CD4+ lymphocytes, although a small part of the IL-2 was also produced by CD8+ cells. The percentage of cells producing simultaneously IL-2 and IFN-gamma was increased in active MS and they were mainly CD4+ lymphocytes. No differences in the production of IL-4 were observed between groups. However, we found an increased IL-10 production in clinically active MS patients (P = 0.03). Treatment with IFN-beta of active MS patients showed lower levels of cytokines when compared with untreated MS patients. This methodological approach could help in the follow up and therapeutic monitoring of MS patients.

EBV-Induced Expression and HLA-DR-Restricted Presentation by Human B Cells of αB-Crystallin, a Candidate Autoantigen in Multiple Sclerosis

The development of multiple sclerosis is most likely influenced by autoimmune responses to central nervous system myelin proteins as well as by infections with common viruses such as EBV and human herpesvirus-6. However, much remains to be established on how these factors interact. In this study, we show that upon EBV infection, human B cells start to express αB-crystallin, a small stress protein that was identified previously as an immunodominant Ag of CNS myelin in multiple sclerosis patients. EBV-induced expression of αB-crystallin in B cells leads to HLA-DR-restricted presentation of the protein and to activation of proinflammatory αB-crystallin-specific Th cells. While αB-crystallin is present in EBV-infected human B cells, the protein is absent from human lymphoid tissues under normal conditions. This is in sharp contrast to other stress proteins such as heat-shock protein (hsp)27 and hsp60 that are ubiquitously expressed in these tissues. In addition, the absence of αB-crystallin from lymphoid tissues in humans is unique as compared with other mammals. All other species examined, including rodents, sheep, and primates, showed constitutive expression of αB-crystallin in secondary lymphoid tissues and sometimes even in the thymus. Since constitutive lymphoid expression most likely results in immunologic tolerance, such a state of tolerance to αB-crystallin can be expected for all of these species, but not for humans. When taken together, our data provide evidence for a novel mechanism by which common viral infections can trigger myelin-directed autoimmunity in a way that is unique for humans.

The role of tumour necrosis factor, interleukin 6, interferon-gamma and inducible nitric oxide synthase in the development and pathology of the nervous system

Proinflammatory cytokines, tumour necrosis factor (TNF)-alpha, interferon (IFN)-gamma and interleukin (IL)-6, have multiple effects in the central nervous system (CNS) not strictly cytotoxic being involved in controlling neuronal and glial activation, proliferation, differentiation and survival, thus influencing neuronal and glial plasticity, degeneration as well as development and regeneration of the nervous system. Moreover, they can contribute to CNS disorders, including multiple sclerosis. Alzheimer's disease and human immunodeficiency virus-associated dementia complex. Recent results with deficient mice in the expression of those cytokines indicate that they are in general more sensible to insults resulting in neural damage. Some of the actions induced by TNF-alpha, and IFN-gamma, including both beneficial and detrimental, are mediated by inducible nitric oxide synthase (iNOS)-derived nitric oxide (NO) production. NO produced by iNOS may be beneficial by promoting the differentiation and survival of neurons. IL-6 does not induce iNOS, explaining why this cytokine is less often involved in this dual role protection pathology. Some of the proinflammatory as well as the neurotrophic effects of those cytokines also involve upregulation of cell adhesion molecules (CAM). Those apparently conflicting results may be reconciled considering that proinflammatory cytokines are involved in promoting the disease, mostly by inducing expression of CAM leading to alteration of the blood-brain barrier integrity, whereas they have a protective role once disease is established due to its immunosuppressive or neurotrophic role. Understanding the dichotomy pathogenesis/neuroprotection of those cytokines may provide a rationale for better therapeutic strategies.

T-cell responses to myelin antigens in multiple sclerosis; relevance of the predominant autoimmune reactivity to myelin oligodendrocyte glycoprotein

Until recently, the search for the 'culprit' autoantigen towards which deleterious autoimmunity is directed in multiple sclerosis (MS) centered mostly on myelin basic protein (MBP) and proteolipid (PLP), the two most abundant protein components of central nervous system (CNS) myelin, the target tissue for the autoimmune attack in MS. Although such research has yielded important data, furthering our understanding of the disease and opening avenues for possible immune-specific therapeutic approaches, attempts to unequivocally associate MS with MBP or PLP as primary target antigens in the disease have not been successful. This has led in recent years to a new perspective in MS research, whereby different CNS antigens are being investigated for their possible role in the initiation or progression of MS. Interesting studies in laboratory animals show that T-cells directed against certain non-myelin-specific CNS antigens are able to cause inflammation of the CNS, albeit without expression of clinical disease. However, reactivity to these antigens by MS T-cells has not been demonstrated. Conversely, reactivity by MS T-cells to non-myelin-specific antigens such as heat shock proteins, could be observed, but the pathogenic potential of such reactivity has not been corroborated with the encephalitogenicity of the antigen. More relevant to MS pathogenesis may be, as we outlined in this review, the autoimmune reactivity directed against minor myelin proteins, in particular the CNS-specific myelin oligodendrocyte glycoprotein (MOG). Here, we review the current knowledge gathered on T-cell reactivity to possible target antigens in MS in the context of their encephalitogenic potential, and underline the facets which make MOG a highly relevant contender as primary target antigen in MS, albeit not necessarily the only one.

Experimental Autoimmune Encephalomyelitis Induced with a Combination of Myelin Basic Protein and Myelin Oligodendrocyte Glycoprotein Is Ameliorated by Administration of a Single Myelin Basic Protein Peptide

Multiple sclerosis is an autoimmune disease of the central nervous system in which T cell reactivity to several myelin proteins, including myelin basic protein (MBP), proteolipid protein, and myelin oligodendrocyte glycoprotein (MOG), has been implicated in the perpetuation of the disease state. Experimental autoimmune encephalomyelitis (EAE) is used commonly as a model in which potential therapies for multiple sclerosis are evaluated. The ability of T cell epitope-containing peptides to down-regulate the disease course is well documented for both MBP- and proteolipid protein-induced EAE, and recently has been shown for MOG-induced EAE. In this study, we describe a novel EAE model, in which development of severe disease symptoms in (PL/J × SJL)F1 mice is dependent on reactivity to two different immunizing Ags, MBP and MOG. The disease is often fatal, with a relapsing/progressive course in survivors, and is more severe than would be predicted by immunization with either Ag alone. The MOG plus MBP disease can be treated postinduction with a combination of the MOG 41–60 peptide (identified as the major therapeutic MOG epitope for this strain) and the MBP Ac1–11[4Y] peptide. A significant treatment effect can also be obtained by administration of the MBP peptide alone, but this effect is strictly dose dependent. This MBP peptide does not treat the disease induced only with MOG. These results suggest that peptide immunotherapy can provide an effective means of mitigating disease in this model, even when the treatment is targeted to only one component epitope or one component protein Ag of a diverse autoimmune response.

Interleukin-12 and perforin mRNA expression is augmented in blood mononuclear cells in multiple sclerosis

Cytokines are suggested to orchestrate an abnormal immune response in multiple sclerosis (MS). The regulatory cytokine interleukin (IL)-12 induces T-helper (Th) cell switch to the Th1 type and the production by cytotoxic T cells of perforin, a cell lysis-inducing factor. It has been suggested that Th1-like cytokines may promote the development of MS, and the production of perforin to induce oligodendrocyte damage. In-situ hybridization with radiolabelled synthetic oligonucleotide probes was used to detect and enumerate mononuclear cells (MNC) expressing IL-12 and perforin mRNA in blood and cerebrospinal fluid (CSF) from patients with MS and controls. Plasma and CSF levels of IL-12 (p70) were evaluated by ELISA. Higher numbers of IL-12 and perforin mRNA-expressing MNC were registered in blood in MS and also in controls with aseptic meningoencephalitis (AM) compared to healthy subjects. There were a few patients with other non-inflammatory neurological diseases who also had high levels of IL-12 or perforin mRNA expressing blood MNC. A parallel elevation was observed for IL-12 (p70) concentrations in plasma. In the MS patients' CSF, there was a further augmentation of IL-12 mRNA expressing MNC. To evaluate autoantigen-induced IL-12 and perforin mRNA expression, blood MNC were cultivated +/- myelin basic protein (MBP), a candidate autoantigen in MS. Higher numbers of MBP-reactive IL-12 and perforin mRNA expressing blood MNC were detected in MS than controls. The augmentation of both IL-12 and perforin in MS might reflect ongoing inflammatory processes in MS and could represent targets for future treatments.

Peripheral blood in Sjögren's syndrome does not contain increased levels of T lymphocytes reactive with the recombinant Ro/SS-A 52 kD and La/SS-B 48 kD autoantigens

Patients with Sjögren's syndrome (SS) frequently have anti-Ro/SS-A and anti-La/SS-B autoantibodies. The aim of this study was to investigate if these patients have peripheral blood lymphocytes (PBL) secreting IFN-gamma after short-term cultivation in the presence of Ro/SS-A and La/SS-B antigens. The frequency of PBL secreting IFN-gamma was examined in 12 SS patients and 11 healthy controls. The enzyme-linked immunospot (ELISPOT) assay was performed after 48 hours cultivation of PBL in the presence of recombinant Ro 52 kD protein or recombinant La 48 kD protein. The number of unstimulated IFN-gamma secreting cells in the SS patient group was not significantly different from that of the control group. Moreover, no increase in the number of IFN-gamma secreting cells after Ro/SS-A and La/SS-B stimulation was detected in the two groups. Thus, T cells reactive with the recombinant Ro 52 kD and La 48 kD proteins do not occur with any increased frequency in peripheral blood of SS patients.

Expression of IFN-gamma, IL-4, and TGF-beta in multiple sclerosis in relation to HLA-Dw2 phenotype and stage of disease

Multiple sclerosis (MS) is associated with upregulation of both proinflammatory (interferon-gamma, IFN-gamma) and immunosuppressive (transforming growth factor-beta, TGF-beta) cytokines. To examine a possible relation between the MS-related HLA haplotype Dw2 and cytokine profiles, we used in situ hybridization with labeled cDNA oligonucleotide probes to detect transcripts of the T helper type 1 (Th 1) cell related IFN-gamma, the Th2 cell related interleukin-4 (IL-4) and of TGF-beta in blood and cerebrospinal fluid (CSF) mononuclear cells from 62 patients with MS. Compared to patients with other neurological diseases and healthy controls, MS patients had elevated numbers of IFN-gamma, IL-4 and TGF-beta mRNA expressing cells in blood and further augmented in CSF. Although several HLA-Dw2-positive individuals showed very high numbers of cells expressing these cytokines, no significant difference was found in comparison with Dw2-negative patients. However, expression of IL-4 and TGF beta mRNA was significantly increased in patients with shorter duration and minor disability and, for IL-4, in patients still in the relapsing-remitting phase compared to patients with secondary chronic progressive MS. Surprisingly, these changes which favour a beneficial, disease-downregulating effect of IL-4 and TGF-beta in MS, were found to be confined to HLA-Dw2-positive patients. Our findings suggest that the HLA phenotype does not influence the overall level of immune reactivity in MS, but may distinguish subgroups characterized by particular cytokine expression patterns.

The outer surface proteins of Lyme disease borrelia spirochetes stimulate T cells to secrete interferon-gamma (IFN-gamma): diagnostic and pathogenic implications

Late stages of borrelia Lyme disease infections may be difficult to diagnose because of unspecific symptoms and unreliable laboratory tests, being too unspecific or insensitive. The T cell immune response was thus evaluated in these patients by using a sensitive ELISPOT T cell assay that detects the secretion of IFN-gamma, i.e. a T helper 1 (Th1) response on the single-cell level. Three subcellular fractions of the Lyme borreliosis strain Borrelia afzelii were used for antigenic stimulation. The outer surface protein (Osp) fraction elicited the strongest response, discriminating between borrelia infections (n = 15) compared with other neurological diseases (n = 10) and normal controls (n = 12) (P = 0.0001). The more heterogeneous sonicated borrelia fraction also elicited a strong response, however, also in some of the controls. The flagellin fraction did not have a similar T cell-stimulating effect. When looking at subgroups of borrelia infections, central nervous system (CNS) infections (n = 7) revealed a lower T cell response in blood (P = 0.0128) compared with other borrelia manifestations (n = 8). Cerebrospinal fluid (CSF) lymphocytes were available from three patients with CNS borreliosis, and all showed a compartmentalization with higher responses to the Osp fraction in CSF compared with blood, also in the two patients without any intrathecal-specific antibody synthesis. The ELISPOT method is feasible for detecting a specific IFN-gamma T cell response in borrelia infections. This Th1 response may well be of pathogenic relevance.

Depletion of CD8+ T cells suppresses the development of experimental autoimmune myasthenia gravis in Lewis rats

To understand the role of CD8+ T cells in experimental autoimmune myasthenia gravis (EAMG), CD8+ T cells were depleted by injecting a monoclonal anti-rat CD8 antibody (OX8) into Lewis rats immunized with Torpedo acetylcholine receptor (AChR) in complete Freund's adjuvant (CFA). CD8-depleted EAMG rats showed strikingly less muscle weakness and lower anti-AChR IgG antibody levels compared to Hy2-15-injected control EAMG rats. Moreover, the numbers of AChR-specific IgG antibody-secreting cells, AChR-reactive interferon-gamma-secreting T helper type 1-like cells and lymphocyte proliferation to AChR were lower in the CD8-depleted group than in control EAMG rats. These differences were significant among mononuclear cells from inguinal and popliteal lymph nodes, mesenteric lymph nodes and spleen, but not from thymus when examined 3, 5 and 7 weeks post-immunization. We suggest that CD8+ T cells are involved in the induction and persistance of EAMG by directly or indirectly affecting AChR-reactive T cells and anti-AChR IgG antibody-secreting cells.

Is there a case for a virus aetiology in multiple sclerosis?

Multiple Sclerosis (MS) is a devastating demyelinating disease with a very high prevalence in North-East Scotland and in the Orkney and Shetland Islands. MS appears to be a multifactorial disorder with environmental and genetic elements and it has been proposed that these, in tandem, provoke an autoimmune response giving rise to the disease. Although there is no direct evidence of a specific virus being involved in MS, there are nevertheless grounds for suspecting a viral association. This review discusses these aspects of MS and suggests that a more aggressive approach to unravelling the role of viruses is needed.

Immunological aspects of experimental allergic encephalomyelitis and multiple sclerosis

Multiple sclerosis (MS) is the most frequent, demyelinating disease of the central nervous system (CNS) in Northern Europeans and North Americans. Despite intensive research its etiology is still unknown, but a T cell-mediated autoimmune pathogenesis is likely to be responsible for the demyelination. This hypothesis is based both on findings in MS patients and studies of an experimental animal model for demyelinating diseases, experimental allergic encephalomyelitis (EAE). Experiments in EAE have not only demonstrated which myelin antigens are able to induce the demyelinating process but also have determined the characteristics of encephalitogenic T cells, that is, their fine specificity, major histocompatibility complex (MHC) restriction, lymphokine secretion, activation requirements, and T cell receptor (TCR) usage. Based on these findings, highly specific and efficient immune interventions have been designed in EAE and have raised hopes that similar approaches could modulate the disease process in MS. Although the examination of the myelin-specific T cell response in MS patients has shown parallels to EAE, this remains an area of intensive research because a number of questions remain. This review summarizes the important lessons from EAE, examines recent findings in MS, and discusses current concepts about how the disease process develops and which steps might be taken to modulate it.

Self-determinants in autoimmune demyelinating disease: changes in T- cell response specificity

Recent research developments support the following views regarding antigen recognition in autoimmune demyelinating disease: there may be no single autoimmune target protein; diverse peptide self-determinants from multiple myelin proteins can be recognized; target determinant epitopes may differ among individuals; and target epitope recognition can change with time during the course of disease.

Increased transforming growth factor-beta, interleukin-4, and interferon-gamma in multiple sclerosis

The inflammatory nature of multiple sclerosis (MS) implicates the participation of immunoregulatory cytokines, including the T-helper type 1 (Th1) cell-associated interferon-gamma (IFN-gamma), the Th2 cell-related interleukin-4 (IL-4), and the immune response-downregulating cytokine transforming growth factor-beta (TGF-beta), but proof for their involvement in MS has been lacking. By adopting in situ hybridization with complementary DNA oligonucleotide probes for human IFN-gamma IL-4, and TGF-beta, the expression of mRNA for these cytokines was detected in mononuclear cells (MNC) from blood and cerebrospinal fluids. Strongly elevated levels of MNC expressing all three cytokines were found in peripheral blood and at even higher frequencies in cerebrospinal fluid from untreated patients with MS and optic neuritis, i.e., a common first manifestation of MS, compared with patients with other neurological diseases and healthy subjects. In MS and optic neuritis, IL-4 mRNA expressing cells predominated, followed by TGF-beta- and IFN-gamma-positive cells. Control patients with myasthenia gravis had similarly elevated levels of IFN-gamma and TGF-beta and TGF-beta mRNA expressing blood MNC but lower numbers of IL-4-positive cells. No or slight disability of MS was associated with high levels of TGF-beta mRNA expressing cells, while MS patients with moderate or severe disability had high levels of IFN-gamma-positive cells. IFN-gamma and TGF-beta may have opposing effects in MS, and treatments inhibiting IFN-gamma and/or promoting TGF-beta might ameliorate MS.

Optic neuritis and multiple sclerosis: the T cell repertoires to myelin proteins and MBP peptides change with time

Autoreactive T cells recognizing myelin basic protein (MBP), proteolipid protein (PLP) and MBP peptides have been described in multiple sclerosis (MS) and optic neuritis (ON), but their role in disease pathogenesis, if any, is unknown. A consistency of the T cell repertoire over the course of MS and ON should facilitate the development of specific immunotherapies. We have examined the T cell responses to autoantigens in two consecutive blood specimens taken from patients with ON and MS, and in two consecutive CSF specimens obtained from ON patients. As read-out numbers of T cells responding to antigen stimulation by the secretion of interferon-gamma were estimated. Pronounced differences in occurrence and numbers of T cells recognizing MBP, MBP peptides with the amino acid sequences 63-88, 110-128 and 148-165, and PLP were noticed in individual ON and MS patients over the course of disease. The MBP peptide among those three included, that was predominantly recognized by T cells in the individual patient, also varied over the course. The quantitative and qualitative changes of the myelin antigen-specific T cell response in MS and in ON, the latter to a certain extent reflecting the situation in early MS, do not favor the future useful development of specific immunotherapies in these diseases.

Autoimmune T cell repertoire in optic neuritis and multiple sclerosis: T cells recognising multiple myelin proteins are accumulated in cerebrospinal fluid

Monosymptomatic unilateral optic neuritis is a common first manifestation of multiple sclerosis. Abnormal T cell responses to myelin components including myelin basic protein (MBP), proteolipid protein (PLP), and myelin-associated glycoprotein (MAG) have been implicated in the pathogenesis of multiple sclerosis. Antigen-reactive T helper type 1 (Th1)-like cells that responded by interferon gamma (IFN-gamma) secretion on antigen stimulation in vitro were counted. Untreated patients with optic neuritis and multiple sclerosis had similarly raised levels of T cells recognising MBP, PLP, and MAG in peripheral blood. Such T cells were strongly enriched in CSF. None of these myelin antigens functioned as immunodominant T cell antigen characteristic for optic neuritis or multiple sclerosis. The autoimmune T cell repertoire was not more restricted in optic neuritis (as an example of early multiple sclerosis). The autoreactive T cell repertoires differed in blood compared with CSF in individual patients with optic neuritis and multiple sclerosis. No relations were found between specificity or quantity of autoreactive T cells in blood or CSF, and clinical variables of optic neuritis or multiple sclerosis, or occurrence of oligoclonal IgG bands in CSF. The role of raised MBP, PLP, and MAG reactive Th1-like cells found in optic neuritis and multiple sclerosis remains unexplained.

Organ-specific autoantigens induce transforming growth factor-beta mRNA expression in mononuclear cells in multiple sclerosis and myasthenia gravis

Multiple sclerosis (MS) is characterized by patchy accumulations of inflammatory cells combined with demyelination. There are mononuclear cells in blood and cerebrospinal fluid of patients with MS that produce interferon-gamma and interleukin-4 in response to myelin basic protein (MBP) and proteolipid protein (PLP). Here we describe autoantigen-induced production of transforming growth factor-beta (TGF-beta). This multifunctional cytokine has inhibitory effects on the growth, differentiation, and effector functions of activated T cells. Blood and cerebrospinal fluid cells were exposed in short-term cultures to MBP and PLP and, after hybridization with complementary DNA oligonucleotide probes, they were evaluated for TGF-beta mRNA expression. Patients with MS had higher numbers of MBP- and PLP-responsive TGF-beta mRNA expressing cells in blood compared with control patients with other neurological diseases or myasthenia gravis and a five- and threefold further increment in their cerebrospinal fluid. In blood of patients with myasthenia gravis, where the acetylcholine receptor (AChR) is a target for autoaggressive immunity, there were increased levels of AChR-responsive TGF-beta mRNA expressing cells. Thymectomized myasthenia gravis patients showed higher levels of TGF-beta mRNA expressing cells compared with patients not thymectomized. Numbers of cells responding to AChR in MS and MBP in myasthenia gravis did not differ from numbers found in absence of antigen. Patients with other neurological diseases showed infrequent and low responses to MBP, PLP, and AChR. Diseases with presumed autoimmune pathogenesis are associated with organ-specific autoantigen-induced TGF-beta production, which is increased after thymectomy.

Multiple sclerosis:cerebrospinal fluid

Examination of cerebrospinal fluid (CSF) in the context of multiple sclerosis (MS), is valuable for several reasons. First, routine diagnostic evaluation of CSF cell counts and various forms of immunoglobulin determination are important to differentiate MS from other diseases. Second, because MS most probably is an organ-specific inflammatory disease and CSF is often the closest one can get to the target organ, examination of this fluid may allow basic studies on the immunopathogenesis of the disease, and indications of different aspects of inflammation should be considered when evaluating treatments aimed at reducing central nervous system inflammation. This article describes measurements taken at the cellular level in blood and CSF, of myelin-antigen autoreactive B- and T-cell responses, as well as cytokine production. Patients with MS display greatly increased numbers of cells in the CSF that produce antibodies against a variety of myelin antigens, such as myelin basic protein, proteolipid protein, and myelin-oligodendrocyte glycoprotein. Such antibodies may promote demyelination, and autoreactive B cells may enhance antigen presentation to T cells. There is also an increased number of T cells in MS, which in response to a broad range of myelin antigens and peptides, produce cytokines. The production of interferon-gamma, belonging to the T helper-1 type of cells, may have a disease up-regulatory role, while production of other cytokines, such as transforming growth factor beta, may counteract disease. Accurate measurements of cellular production of cytokines will be important in the design and monitoring of immunotherapy.

Optic neuritis is associated with myelin basic protein and proteolipid protein reactive cells producing interferon-gamma, interleukin-4 and transforming growth factor-beta

Studies on patients with monosymptomatic optic neuritis (ON) should give opportunities to identify features typical for early multiple sclerosis (MS). There are increased T and B cell responses to the myelin components myelin basic protein (MBP) and proteolipid protein (PLP) in both ON and MS, but there is little information on the types of cytokines produced by such cells. We describe the use of in situ hybridization with complementary DNA oligonucleotide probes to detect and enumerate mononuclear cells expressing mRNA for the cytokines interferon-gamma (IFN-gamma) which augments cell-mediated immunity; interleukin-4 (IL-4) which promotes the B cell response; and transforming growth factor beta (TGF-beta) that in many cases downregulates immune responses. Expression of these cytokines was studied in mononuclear cells from peripheral blood and cerebrospinal fluid (CSF) from patients with ON and MS after in vitro exposure to MBP and PLP, and in absence of antigen. There were elevated levels of cells that in response to MBP and PLP expressed IFN-gamma, IL-4 and TGF-beta mRNA in blood and further enriched in CSF in both ON and MS, compared to patients with other neurological diseases. The results suggest that IFN-gamma, IL-4 as well as TGF-beta are involved in both ON and MS, and that the cytokine profile in early MS as reflected by ON is not different from that in clinically definite MS.