The pathophysiology of myelin basic protein-induced acute experimental allergic encephalomyelitis in the Lewis rat

The Short and Long-Term Effects of Pregnancy on Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis

The role of pregnancy in multiple sclerosis (MS) is of importance because many patients with MS are young women in the childbearing age who require information to inform their reproductive decisions. Pregnancy is now well-known to be associated with fewer relapses of MS and reduced activity of autoimmune encephalomyelitis (EAE). However, in women with multiple sclerosis, this benefit is not always sufficient to protect against a rebound of disease activity if disease-modulating therapy is ceased for pregnancy. There is concern that use of assisted reproductive therapies can be associated with relapses of MS, but more data are required. It is thought that the beneficial effects of pregnancy are due to the pregnancy-associated changes in the maternal immune system. There is some evidence of this in human studies and studies of EAE. There is also evidence that having been pregnant leads to better long-term outcome of MS. The mechanism for this is not fully understood but it could result from epigenetic changes resulting from pregnancy or parenthood. Further studies of the mechanisms of the beneficial effects of pregnancy could provide information that might be used to produce new therapies.

Mechanisms and pharmacology of neuropathic pain in multiple sclerosis

The neuropathic pain of multiple sclerosis is quite prevalent and severely impacts quality of life. A few randomized, placebo-controlled, blinded clinical trials suggest that cannabis- and anticonvulsant-based treatments provide partial pain relief, but at the expense of adverse events. An even smaller, but emerging, number of translational studies are using rodent models of experimental autoimmune encephalomyelitis (EAE), which exhibit pain-like behaviors resembling those of Multiple sclerosis (MS) patients. These studies not only support the possible effectiveness of anticonvulsants, but also compel further clinical trials with serotonin-norepinephrine reuptake inhibitors, the immunosuppressant drug rapamycin, or drugs which interfere with glutamatergic neurotransmission. Future behavioral studies in EAE models are essential toward a new pharmacotherapy of multiple sclerosis pain.

Effects of vaccination with altered Peptide ligand on chronic pain in experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis

Neuropathic pain is a chronic symptom of multiple sclerosis (MS) and affects nearly half of all MS sufferers. A key instigator of this pain is the pro-inflammatory response in MS. We investigated the behavioral effects of immunization with a mutant peptide of myelin basic protein (MBP), termed altered peptide ligand (APL), known to initiate immune deviation from a pro-inflammatory state to an anti-inflammatory response in experimental autoimmune encephalomyelitis (EAE), an animal model of MS. Male and female Lewis rats were injected with vehicle control or with varying doses of 50 or 100 μg guinea pig MBP in combination with or without APL. APL-treated animals established significantly lower disease severity compared to encephalitogenic MBP-treated animals. Animals with EAE developed mechanical, but not thermal pain hypersensitivity. Mechanical pain sensitivities were either improved or normalized during periods of clinical disease in male and female APL-treated animals as compared to the encephalitogenic group. No significant changes to thermal latency were observed upon co-immunization with APL. Together these data indicate that APL ameliorates disease states and selectively mediates an analgesic effect on EAE animals.

Gene expression in the spinal cord in female lewis rats with experimental autoimmune encephalomyelitis induced with myelin basic protein

Background

Experimental autoimmune encephalomyelitis (EAE), the best available model of multiple sclerosis, can be induced in different animal strains using immunization with central nervous system antigens. EAE is associated with inflammation and demyelination of the nervous system. Micro-array can be used to investigate gene expression and biological pathways that are altered during disease. There are few studies of the changes in gene expression in EAE, and these have mostly been done in a chronic mouse EAE model. EAE induced in the Lewis with myelin basic protein (MBP-EAE) is well characterised, making it an ideal candidate for the analysis of gene expression in this disease model.

Methodology/Principal Findings

MBP-EAE was induced in female Lewis rats by inoculation with MBP and adjuvants. Total RNA was extracted from the spinal cords and used for micro-array analysis using AffimetrixGeneChip Rat Exon 1.0 ST Arrays. Gene expression in the spinal cords was compared between healthy female rats and female rats with MBP-EAE. Gene expression in the spinal cord of rats with MBP-EAE differed from that in the spinal cord of normal rats, and there was regulation of pathways involved with immune function and nervous system function. For selected genes the change in expression was confirmed with real-time PCR.

Conclusions/Significance

EAE leads to modulation of gene expression in the spinal cord. We have identified the genes that are most significantly regulated in MBP-EAE in the Lewis rat and produced a profile of gene expression in the spinal cord at the peak of disease.

Models of autoimmune demyelination in the central nervous system: on the way to translational medicine

Multiple sclerosis (MS) is the most common neurologic disease of young adults. In the recent years, our understanding on disease pathomechanisms has considerably improved and new therapies have emerged. Yet a cure for this devastating disorder is still a far cry away and human resources on ex vivo specimens are limited. More than 70 years after its first description, experimental autoimmune encephalomyelitis (EAE) remains an important tool to understand concepts of T cell mediated autoimmunity as well as the roles of the innate and the humoral immune systems. Some EAE models also well reflect mechanisms of tissue damage including demyelination, axonal injury and also cortical changes. A limitation of the classical EAE model is a neglect of CD8 T cell mediated immune mechanisms. Moreover, well characterized models for primary progressive MS or demyelination patterns involving primary oligodendrocyte dystrophy are still not available. Yet many current therapeutic concepts including glatiramer acetate or natalizumab stem from their successful first application in EAE models. New strategies include the widespread use of conditional knockout mice to understand the cell-type specific function of single genes, innovative approaches to establish models on the roles of B cells and CD8 T cells as well as on the relation of inflammation to primary degeneration. In summary, EAE models continue to play an important role in neuroimmunology thereby also stimulating research in other fields of the neurosciences and immunobiology.

Chronic inflammatory demyelinating polyradiculoneuropathy associated with multiple sclerosis

OBJECTIVE

To describe temporal profile of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) in patients with definite, relapsing multiple sclerosis (MS).

BACKGROUND

Peripheral demyelinating neuropathy has been rarely reported in association with central nervous system demyelinating disorder indistinguishable from MS.

METHODS

In addition to usual diagnostic studies for CIDP and MS in all 5 patients, we studied proximal segments of nerves using deep tendon reflex latency measurements of biceps reflex, patellar reflex, and ankle reflex.

RESULTS

All patients with MS subsequently (4-22 years) developed definite CIDP. Two of these patients developed multiple cranial nerve and spinal root enhancement on subsequent imaging without new intraparenchymal enhancement after a diagnosis of CIDP. The deep tendon reflex latencies were prolonged at more than 2 sites in all patients. Cerebral spinal fluid protein increased (70 +/- 19 to 144.8 +/- 17.4 mg/dL, P = 0.0001) at time of diagnosis of CIDP. Clinical improvement was observed in all patients after intravenous immunoglobulin therapy.

CONCLUSIONS

When patients with MS develop CIDP, manifestations of central and peripheral disease involvement seem to respond to intravenous immunoglobulin. These cases suggest that there may be common antigenic targets in central and peripheral nervous system in this subset of patients.

Sclérose en plaques et atteinte du système nerveux périphérique

Multiple sclerosis is a demyelinating disease limited to the central nervous system, but the literature has provided recurring evidence which raises the question of associated peripheral nervous system abnormalities. The prevalence of peripheral neuropathy during multiple sclerosis remains controversial without prospective study. Nevertheless, some data have reported well documented case reports describing the co-occurrence of multiple sclerosis and radiculopathy or mononeuropathy or polyneuropathy in the same patients. By contrast, more frequent subtle nerve abnormalities may be found by using electrophysiological and neuropathological examinations. Some hypotheses have been proposed by Waxman to decipher the electrophysiological and neuropathological findings. The mechanisms for demyelinating disease and peripheral nerve pathophysiology may imply the antigenic properties or the presence of diffusing factors between peripheral nervous system and central nervous system myelin and the molecular plasticity of myelinated fibers.

Impaired peroxisomal function in the central nervous system with inflammatory disease of experimental autoimmune encephalomyelitis animals and protection by lovastatin treatment

Peroxisomes are ubiquitous subcellular organelles and abnormality in their biogenesis and specific gene defects leads to fatal demyelinating disorders. We report that neuroinflammatory disease in brain of experimental autoimmune encephalomyelitis (EAE) rats decreased the peroxisomal functions. Degradation of very long chain fatty acids decreased by 47% and resulted in its accumulation (C26:0, 40%). Decreased activity (66% of control) of dihydroxyacetonephosphate acyltransferase (DHAP-AT), first enzyme in plasmalogens biosynthesis, resulted in decreased levels of plasmalogens (16-30%). Catalase activity, a peroxisomal enzyme, was also reduced (37%). Gene microarray analysis of EAE spinal cord showed significant decrease in transcripts encoding peroxisomal proteins including catalase (folds 3.2; p<0.001) and DHAP-AT (folds 2.6; p<0.001). These changes were confirmed by quantitative reverse transcription polymerase chain reaction (RT-PCR) analysis, suggesting that decrease of peroxisomal functions in the central nervous system will have negative consequences for myelin integrity and repair because these lipids are major constituents of myelin. However, lovastatin (a cholesterol lowering and anti-inflammatory drug) administered during EAE induction provided protection against loss/down-regulation of peroxisomal functions. Attenuation of induction of neuroinflammatory mediators by statins in cultured brain cells [J. Clin. Invest. 100 (1997) 2671-2679], and in central nervous system of EAE animals and thus the EAE disease [J. Neurosci. Res. 66 (2001) 155-162] and the studies described here indicate that inflammatory mediators have a marked negative effect on peroxisomal functions and thus on myelin assembly and that these effects can be prevented by treatment with statins. These observations are of importance because statins are presently being tested as therapeutic agents against a number of neuroinflammatory demyelinating diseases.

Multiple sclerosis and glutamate

Experimental autoimmune encephalomyelitis reproduces in rodents the features of multiple sclerosis, an immune-mediated, disabling disorder of the human nervous system. No adequate therapy is available for multiple sclerosis, despite anti-inflammatory, immunosuppressive, and immunomodulatory measures. Increasingly glutamate is implicated in the pathogenesis of neurodegenerative diseases. Here we (1) review changes in the glutamatergic system in multiple sclerosis and (2) reveal the effects of glutamate AMPA antagonists in acute and chronic rodent models of multiple sclerosis. Administration of structurally diverse competitive and non-competitive AMPA antagonists reduces neurologic disability in rodents subjected to acute experimental autoimmune encephalomyelitis. In addition, AMPA antagonists are active in both the adoptive transfer and in chronic models of experimental autoimmune encephalomyelitis in rats and mice and affect both the acute and chronic relapsing phases. Moreover, short-term therapy with AMPA antagonists leads to sustained benefit well into the progressive phases. These results imply that therapeutic strategies for multiple sclerosis should be complemented by glutamate AMPA antagonists to reduce neurologic disability.

Mycophenolate mofetil treatment accelerates recovery from experimental allergic encephalomyelitis

Mycophenolate mofetil (MM) acts through its metabolite mycophenolic acid to inhibit inosine monophosphate dehydrogenase (IMPDH), an enzyme essential for purine synthesis in lymphocytes. Oral treatment with MM from the day of immunization for 2 weeks significantly delayed both the development of active experimental allergic encephalomyelitis (EAE) in Lewis rats and reduced the antibody response to myelin basic protein (MBP). MM did not deplete T and B cells, nor did it prevent induction of Th1 or Th2 cytokine in the regional nodes. Treatment of EAE with MM at the onset of clinical symptoms resulted in more rapid recovery from EAE than in control or cyclosporin A (CsA)-treated. MM-treated rats had less infiltration of T cells, B cells, macrophages and dendritic cells into brainstems than either the control or CsA-treated. MM-treated brainstems also had lower level of mRNA for Thl (IL-2, IL-12Rbeta2, IFN-gamma), Th2 (IL-4, IL-10) cytokines and TNF-alpha and TGF-beta compared to that in CsA and controls groups. This study shows MM was superior to CsA in the treatment of EAE and acted by reducing the inflammatory infiltrate, not by suppression of Ig response or by promotion of regulatory cells such as Th2 or Th3.

Myelin/axonal pathology in interleukin-12 induced serial relapses of experimental allergic encephalomyelitis in the Lewis rat

Lewis rats, on recovery from monophasic clinical experimental allergic encephalomyelitis (EAE), can be induced to develop repeated paralytic relapses with a graded reduction in clinical severity following intraperitoneal administration of IL-12. By the time of the third relapse, the number and size of inflammatory cuffs in the spinal cord were reduced with the makeup of the cellular infiltrate shifting to a significantly increased number of B cells. Serum levels of myelin basic protein (MBP)-specific IgG1 and IgG2b were found to rise over time while MBP and MBP peptide-positive macrophages and microglia became evident in perivascular cuffs and in spinal cord parenchyma, indicative of myelin phagocytosis. Axonal death was observed in semithin and EM sections of spinal cord in third relapse animals in association with iNOS and tPA immunostaining throughout gray and white matter. These neurotoxic or excitotoxic agents may contribute to axonal damage directly or indirectly by activated microglia and macrophages, leading to limited damage of the axonal-myelin unit.

Selective blocking of voltage-gated K+ channels improves experimental autoimmune encephalomyelitis and inhibits T cell activation

Kaliotoxin (KTX), a blocker of voltage-gated potassium channels (Kv), is highly selective for Kv1.1 and Kv1.3. First, Kv1.3 is expressed by T lymphocytes. Blockers of Kv1.3 inhibit T lymphocyte activation. Second, Kv1.1 is found in paranodal regions of axons in the central nervous system. Kv blockers improve the impaired neuronal conduction of demyelinated axons in vitro and potentiate the synaptic transmission. Therefore, we investigated the therapeutic properties of KTX via its immunosuppressive and symptomatic neurological effects, using experimental autoimmune encephalomyelitis (EAE), an animal model for multiple sclerosis. The T line cells used to induce adoptive EAE were myelin basic protein (MBP)-specific, constitutively contained mRNA for Kv1.3. and expressed Kv1.3. These channels were shown to be blocked by KTX. Activation is a crucial step for MBP T cells to become encephalitogenic. The addition of KTX during Ag-T cell activation led to a great reduction in the MBP T cell proliferative response, in the production of IL-2 and TNF, and in Ca(2+) influx. Furthermore, the addition of KTX during T cell activation in vitro led a decreased encephalitogenicity of MBP T cells. Moreover, KTX injected into Lewis rats impaired T cell function such as the delayed-type hypersensitivity. Lastly, the administration of this blocker of neuronal and lymphocyte channels to Lewis rats improved the symptoms of EAE. We conclude that KTX is a potent immunosuppressive agent with beneficial effects on the neurological symptoms of EAE.

Combined TUNEL and double immunofluorescent labeling for detection of apoptotic mononuclear phagocytes in autoimmune demyelinating disease

Apoptosis is usually associated with genomic DNA fragmentation which can be detected in situ by the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) assay. We describe a combined TUNEL and double immunofluorescent labeling technique to determine the fate of inflammatory infiltrates and resident glial cells in the central nervous system following the onset of an autoimmune demyelinating disease such as experimental allergic encephalomyelitis (EAE) in rats. Anti-digoxigenin (anti-DIG) antibody conjugated with 7-amino-4-methylcoumarin-3-acetic acid (AMCA) emitting blue fluorescence was used to detect apoptotic cell DNA, which was already labeled by modified TUNEL using alkali-stable DIG-11-dUTP. Anti-mouse IgG secondary antibody conjugated with Texas Red emitting red fluorescence was used to detect anti-rat CD11b primary antibody (clone OX-42) directed to the surface antigen of mononuclear phagocytes including microglia. Using this technique, we detected apoptotic mononuclear phagocytes (co-labeled with blue and red fluorescences) in the spinal cord sections of rats with EAE.

The pathophysiology of multiple sclerosis: the mechanisms underlying the production of symptoms and the natural history of the disease

The pathophysiology of multiple sclerosis is reviewed, with emphasis on the axonal conduction properties underlying the production of symptoms, and the course of the disease. The major cause of the negative symptoms during relapses (e.g. paralysis, blindness and numbness) is conduction block, caused largely by demyelination and inflammation, and possibly by defects in synaptic transmission and putative circulating blocking factors. Recovery from symptoms during remissions is due mainly to the restoration of axonal function, either by remyelination, the resolution of inflammation, or the restoration of conduction to axons which persist in the demyelinated state. Conduction in the latter axons shows a number of deficits, particularly with regard to the conduction of trains of impulses and these contribute to weakness and sensory problems. The mechanisms underlying the sensitivity of symptoms to changes in body temperature (Uhthoff's phenomenon) are discussed. The origin of 'positive' symptoms, such as tingling sensations, are described, including the generation of ectopic trains and bursts of impulses, ephaptic interactions between axons and/or neurons, the triggering of additional, spurious impulses by the transmission of normal impulses, the mechanosensitivity of axons underlying movement-induced sensations (e.g. Lhermitte's phenomenon) and pain. The clinical course of the disease is discussed, together with its relationship to the evolution of lesions as revealed by magnetic resonance imaging and spectroscopy. The earliest detectable event in the development of most new lesions is a breakdown of the blood-brain barrier in association with inflammation. Inflammation resolves after approximately one month, at which time there is an improvement in the symptoms. Demyelination occurs during the inflammatory phase of the lesion. An important mechanism determining persistent neurological deficit is axonal degeneration, although persistent conduction block arising from the failure of repair mechanisms probably also contributes.

Effects of cyclosporin A treatment on clinical course and inflammatory cell apoptosis in experimental autoimmune encephalomyelitis induced in Lewis rats by inoculation with myelin basic protein

Experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats by inoculation with myelin basic protein (MBP) and adjuvants. Rats were treated with second daily injections of saline or cyclosporin A (CsA) from the day of inoculation. Saline-treated rats had an acute episode of disease followed by clinical recovery. Rats treated with CsA 16 or 32 mg/kg had minimal signs of EAE at the usual time after inoculation, but developed signs of disease after treatment was ceased. Rats treated with CsA 8 mg/kg had a delayed first episode of disease and then developed a relapsing or a chronic persistent course of disease. CsA 4 mg/kg delayed the onset of disease. To study the effects of CsA on the inflammatory infiltrate, cells were extracted from the spinal cords of rats with EAE, 16 h after a single injection of CsA or saline. Extracted cells were labelled with antibodies to T cells, CD11b/c (macrophages/microglia), CD95 (Fas) and Fas ligand. CsA 4 mg/kg did not alter the composition of the inflammatory infiltrate. Treatment with higher single doses of CsA caused a dose-dependent decline in the percentage of T cell receptor (TCR) alphabeta+ cells in the inflammatory infiltrate. All doses of CsA caused a significant increase in the number and percentage of cells that were apoptotic. CsA treatment caused an increase in the percentages of CD5+ and TCR alphabeta+ cells that were apoptotic. There was a decline in the percentage of apoptotic T cells that were Vbeta8.2+, compared to the percentage of non-apoptotic T cells that were Vbeta8.2+, in CsA treated rats compared to saline-treated controls. This suggests that, while CsA treatment caused a non-specific increase in the overall level of T cell apoptosis in the spinal cord, it abrogated the selective apoptosis of Vbeta8.2+ encephalitogenic T cells that normally occurs during spontaneous recovery from acute EAE.

Cytokines, signal transduction, and inflammatory demyelination: review and hypothesis

The mechanism of focal demyelination in multiple sclerosis has been a long-standing enigma of this disorder. Cytokines, a diverse family of signalling molecules, are viewed as potential mediators of the process based on clinical observations and studies with animal models and tissue/cell culture systems. Myelin and oligodendrocyte (OL) destruction occur in cultured preparations subjected to cytokines such as tumor necrosis factor-alpha (TNF alpha) and lymphotoxin (LT). Many studies have shown these and other cytokines to be elevated at lesion sites and in the CSF of multiple sclerosis (MS) patients, with similar findings in animal models. Some variability in the nature of MS lesion formation has been reported, both OLs and myelin being primary targets. To account for myelin destruction in the presence of apparently functional OLs we hypothesize that cytokines such as TNF alpha and LT alpha contribute to myelin damage through triggering of specific reactions within the myelin sheath. We further propose that neutral sphingomyelinase (SMase) is one such enzyme, two forms of which have been detected in purified myelin. An additional event is accumulation of cholesterol ester, apparently a downstream consequence of cytokine-induced SMase. The resulting lipid changes are viewed as potentially destabilizing to myelin, which may render it more vulnerable to attack by invading and resident phagocytes.

Conduction in segmentally demyelinated mammalian central axons

The prominent symptoms associated with central demyelinating diseases such as multiple sclerosis (MS) are primarily caused by conduction deficits in affected axons. The symptoms may go into remission, but the mechanisms underlying remissions are uncertain. One factor that could be important is the restoration of conduction to affected axons, but it is not known whether demyelinated central axons resemble their peripheral counterparts in being able to conduct in the absence of repair by remyelination. In the present study we have made intra-axonal recordings from central axons affected by a demyelinating lesion, and then the axons have been labeled ionophoretically to permit their subsequent identification. Ultrastructural examination of 23 labeled preparations has established that some segmentally demyelinated central axons can conduct, and that they can do so over continuous lengths of demyelination exceeding several internodes (2500 micron). Such segmentally demyelinated central axons were found to conduct with the anticipated reduction in velocity and a refractory period of transmission (RPT) as much as 34 times the value obtained from the nondemyelinated portion of the same axon; the RPT was typically prolonged to 2-5 times the normal value. We conclude that some segmentally demyelinated central axons can conduct, and we propose that the restoration of conduction to such axons is likely to contribute to the remissions commonly observed in diseases such as MS.

T-cell receptor V beta-element expression in peripheral nerves of Lewis rats suffering from experimental autoimmune neuritis

In experimental autoimmune neuritis (EAN), peripheral nerves are infiltrated by T-lymphocytes and macrophages. By RT-PCR and sequence analysis we characterized TCR V beta-element usage in sciatic nerve tissue of Lewis rats suffering from EAN induced by immunization with peripheral myelin antigens. Several TCR V beta-chain sequences were detected, which did not show homology to sequences of P2-reactive T cells published so far. In EAN induced with peripheral nerve myelin, but not with P2-protein or P2 peptide aa 53-78, TCR V beta 8.2 sequences identical to sequences of encephalitogenic myelin basic protein (MBP) reactive T-cells were identified. These results provide further evidence for a contribution of MBP-directed T-cell reactivity to the pathogenesis of myelin induced EAN and may have implications for the pathogenesis of human demyelinating neuropathies.

Ganglioside spinal cord changes in chronic relapsing experimental allergic encephalomyelitis induced in the Lewis rats

Chronic relapsing experimental allergic encephalomyelitis (CREAE) was induced in Lewis rats by inoculation with guinea-pig myelin and complete Freund's adjuvant followed by treatment with low-dose cyclosporin A. Rats were sacrified at different phases of the disease (just before the onset of clinical signs, during the first clinical episode of CREAE and during the first recovery). Gangliosides were extracted from the spinal cord, analysed after purification by two-dimensional chromatography and quantified densitometrically. An increase of GM 1, the main rat myelin ganglioside, and a decrease of GT1b, suggested to play a role in mediating the interactions between oligodendroglia and axons, were observed during the development of the CREAE. These findings indicating significant ganglioside changes in CREAE give further support to the concept concerning the involvement of gangliosides in autoimmune demyelination.

Restoration of conduction in the spinal roots correlates with clinical recovery from experimental autoimmune encephalomyelitis

In the Lewis rat, acute experimental autoimmune encephalomyelitis (EAE) induced by inoculation with myelin basic protein (MBP) and adjuvants is characterized by tail and hindlimb weakness that resolves spontaneously after several days. In rats with neurological signs of this form of EAE (MBP-EAE) we have previously demonstrated demyelination and nerve conduction block in the proximal peripheral nervous system (PNS) and in the central nervous system (CNS). The present study was performed to assess conduction in the PNS and CNS, after recovery from acute MBP-EAE, using direct recordings from surgically exposed spinal roots and spinal cord dorsal columns. The study revealed that 1-2 weeks after clinical recovery from tail paralysis there was almost complete restoration of conduction in the sacral spinal roots but persistent severe conduction abnormalities in the dorsal columns. Significant restoration of conduction through the dorsal columns occurred over the following 2 weeks. These findings indicate that PNS conduction block due to a demyelinating polyradiculitis is a major cause of the neurological signs of acute MBP-EAE in the Lewis rat.

Experimental autoimmune peripheral neuritis induced in BALB/c mice by myelin basic protein-specific T cell clones

In vivo adoptive transfer of CD4+ T helper cell type 1 clones reactive with autologous myelin basic protein (MBP) may initiate an inflammatory demyelinating disease of the central nervous system called experimental autoimmune encephalomyelitis. Although MBP is also a component of peripheral nervous system (PNS) myelin, previous studies have failed to demonstrate inflammation in the PNS induced by MBP-reactive T cells. Here, we report on two MBP-specific T cell clones that preferentially initiate inflammatory and demyelinating peripheral neuritis when adoptively transferred to syngeneic recipients. The MBP epitope recognized by these clones spans the junction of exons 6 and 7 and, therefore, is present in the 21- and 18.5-kD but not the 14- and 17-kD MBP isoforms, in which exon 5 is spliced to exon 7. The data suggest that MBP may be processed and presented differently in the central nervous system and PNS, and they provide evidence for MBP as a potential target for autoimmune reactions in the PNS.

The proximal peripheral nervous system is a major site of demyelination in experimental autoimmune encephalomyelitis induced in the Lewis rat by a myelin basic protein-specific T cell clone

Experimental autoimmune encephalomyelitis (EAE) was induced in the Lewis rat by the passive transfer of a cytotoxic CD4+ T cell clone specific for the 72-89 peptide of guinea-pig myelin basic protein (MBP). Histological studies on rats with neurological signs showed that inflammation was present in the proximal peripheral nervous system (PNS), namely the spinal roots, as well as in the central nervous system (CNS). The main sites of demyelination were the spinal roots in the PNS, and the spinal cord root entry and exit zones in the CNS. The major involvement of the proximal PNS in autoimmune disease directed at MBP is in marked contrast to EAE induced by immunisation with myelin proteolipid protein, where the inflammation and demyelination are restricted to the CNS. These findings may have implications for the human inflammatory demyelinating diseases including multiple sclerosis, in which MBP is a putative target antigen.

Clinical and histological findings in proteolipid protein-induced experimental autoimmune encephalomyelitis (EAE) in the Lewis rat. Distribution of demyelination differs from that in EAE induced by other antigens

Proteolipid protein (PLP) is the major protein of central nervous system (CNS) myelin. In some species, intradermal inoculation with PLP and adjuvants causes experimental autoimmune encephalomyelitis (PLP-EAE) characterized by neurological signs of tail and limb weakness and by inflammation and demyelination in the CNS. A previous study found that inoculation of Lewis rats with 100 micrograms of PLP causes PLP-EAE with a low incidence of neurological signs and a highly variable clinical course. In the present study we assessed PLP-EAE produced by inoculation with 1000 micrograms of PLP per rat. Fifty-one of 59 (86%) Lewis rats developed neurological signs 8 to 20 days (mean = 12.0 +/- 2.0) after inoculation with 1000 micrograms of PLP. In such rats, mononuclear cell infiltrates were present in the brain and spinal cord while primary demyelination occurred mainly in the subpial regions of the spinal cord, especially in the dorsal root entry and ventral root exit zones. The histological findings were compared with those in acute EAE induced in the Lewis rat by inoculation with whole CNS tissue or with myelin basic protein: in PLP-EAE, in contrast to these other models, the disease was essentially restricted to the CNS. This form of EAE should be useful in future studies of the consequences of autoimmunity to PLP.

Conduction properties of central demyelinated and remyelinated axons, and their relation to symptom production in demyelinating disorders

The conduction properties of central demyelinated and remyelinated axons are discussed, and related to the expression of symptoms in central demyelinating disease. The mechanisms underlying the block and restoration of conduction in segmentally demyelinated axons are described, together with the range of deficits expressed by the conducting axons. These abnormalities are related to clinical relapses and remissions, and to the phenomena of weakness, fatigue, the temperature sensitivity of symptoms, and the generation of 'positive' symptoms (e.g. Uhthoff's and Lhermitte's symptoms). The potential role of circulating 'blocking factors' in the symptomatology of central demyelinating disease is examined, and some approaches are advanced for the symptomatic therapy of such diseases.

Astrocytic hypertrophy: an important pathological feature of chronic experimental autoimmune encephalitis in aged rats

Experimental autoimmune encephalomyelitis (EAE) was induced in young (2-3 month old), middle-aged (12-13 month old) and geriatric (24-26 month old) Lewis (JC) rats by active immunisation with myelin basic protein (MBP) in complete Freund's adjuvant (CFA). It was found that aged Lewis (JC) rats developed a more chronic form of EAE than younger rats of the same strain, a phenomenon observed in both male and female rats despite males developing more severe disease than females at all ages. Middle-aged recipients also developed more severe disease than young recipients when EAE was induced by the adoptive transfer of lymphocytes from actively immunised young donors, suggesting that disease chronicity in middle-aged animals is a property of the central nervous system (CNS) milieu. Histological studies demonstrated that disease chronicity did not correlate with the number of inflammatory lesions in the CNS, young animals containing substantial numbers of CNS lesions following recovery and lesions being largely absent from middle-aged animals which still exhibited signs of disease. No significant differences were found in the degree of fibrin deposition or demyelination between young and middle-aged or symptomatic and asymptomatic animals. However, astrocytic hypertrophy was found to correlate with manifestation of disease in both young and middle-aged animals and in particular with disease chronicity in middle-aged animals. In parallel studies, no significant differences were found in the levels of the inflammatory mediators tumor necrosis factor (TNF)-alpha, prostaglandin E (PGE)2, reactive nitrogen intermediates (RNI) and corticosterone in young and middle-aged animals. However, markedly elevated corticosterone levels were found in both young and middle-aged animals with the development of clinical signs which returned to baseline levels with the resolution of clinical signs. Elevated levels of RNI were evident in animals immediately prior to and during the early stages of symptomatic EAE. Although these results suggest that nitric oxide may play a role in the pathogenesis of disease, whereas corticosterone may play a role in the immunoregulation of the disease, these factors cannot explain differences in disease chronicity evident in middle-aged animals.(ABSTRACT TRUNCATED AT 400 WORDS)

T cells specific for the myelin oligodendrocyte glycoprotein mediate an unusual autoimmune inflammatory response in the central nervous system

Myelin oligodendrocyte glycoprotein (MOG)-specific T cells mediate an autoimmune inflammatory response in the central nervous system (CNS) that differs radically from conventional models of T cell-mediated experimental allergic encephalomyelitis (EAE). Using synthetic peptides an encephalitogenic T cell epitope of MOG for the Lewis rat was identified within the extracellular IgG V-like domain of the protein, amino acids 44-53 (FSRVVHLYRN). The adoptive transfer of CD4+ T cells specific for this epitope induce an intense, dose-dependent inflammatory response in the CNS of naive syngeneic recipients. However, unlike the inflammatory response induced by myelin basic protein (MBP)-specific T cell lines, inflammation mediated by the MOG peptide-specific T cells failed to induce a gross neurological deficit. This unexpected observation was not due to a reduction in the overall inflammatory response in the CNS, but was specifically associated with a decrease in the extent of parenchymal (as opposed to perivascular) inflammation, a selective decrease in the number of ED1+ macrophages infiltrating the CNS, and a total lack of peripheral nerve inflammation. The decreased recruitment of macrophages into the CNS could not be ascribed to deficiencies in the synthesis of interferon-gamma, tumor necrosis factor-alpha, interleukin (IL)-6 or IL-2 by the T cell line. Moreover, this sub-clinical inflammatory response induced severe blood-brain barrier dysfunction as demonstrated by the induction of severe clinical disease following intravenous injection of a demyelinating MOG-specific monoclonal antibody. The neurological deficit in EAE thus exhibits an unexpected dependence on the identity of the target autoantigen, which determines the extent and nature of the local inflammatory response and ultimately the extent of the neurological deficit.

Apoptosis in the nervous system in experimental allergic encephalomyelitis

We report here for the first time the occurrence of apoptosis of cells in the spinal cord in experimental allergic encephalomyelitis (EAE), an autoimmune, T-cell-mediated demyelinating disease. Four different forms of EAE were studied in the Lewis rat: (i) acute EAE induced by inoculation with whole spinal cord and adjuvants; (ii) acute EAE induced by inoculation with myelin basic protein (MBP) and adjuvants; (iii) acute EAE induced by the passive transfer of MBP-sensitized spleen cells; (iv) chronic relapsing EAE induced by inoculation with whole spinal cord and adjuvants followed by treatment with low-dose cyclosporin A. Cells undergoing apoptosis were recognized at light and electron microscopy by the presence of either crescentic masses of condensed chromatin lying against the nuclear envelope or rounded masses of uniformly dense chromatin. They were found in both the white and grey matter of the spinal cord in all 4 forms of this disease. Although it was not possible to identify definitively the types of cells undergoing apoptosis, the size and location of some of the affected cells suggested that they were oligodendrocytes. As there is now a large body of evidence that T-cell-induced target cell death takes the form of apoptosis, it is attractive to hypothesize that oligodendrocyte apoptosis is occurring in EAE as a result of oligodendrocyte-directed T-cell cytotoxicity. However, other apoptotic cells were located within the myelin sheath, meninges and perivascular spaces and were clearly not oligodendrocytes but were most likely blood-derived mononuclear cells. The sparsity of their cytoplasm and the absence of phagocytosed material suggested that they were mainly lymphocytes rather than macrophages. Apoptosis has been shown to be involved in deleting autoreactive T-cells during the normal development of tolerance. Thus apoptotic deletion of myelin/oligodendrocyte-specific lymphocytes in the central nervous system in EAE might explain both the subsidence of inflammation and the acquisition of tolerance in this autoimmune disease.

Motor neuron destruction in guinea pigs immunized with bovine spinal cord ventral horn homogenate: experimental autoimmune gray matter disease

Guinea pigs immunized with bovine spinal cord ventral horn homogenate develop muscle weakness with electromyographic and morphologic evidence of denervation. Pathological examination demonstrates a loss of motoneurons and scattered inflammatory foci primarily localized to the spinal cord. Immunohistochemical techniques document the presence of immunoglobulin G at the motor end plate and around the external membrane and within the cytoplasm of motoneurons. This syndrome of experimental autoimmune gray matter disease (EAGMD) differs from experimental autoimmune motor neuron disease induced by inoculation with purified motoneurons and also differs from experimental autoimmune encephalomyelitis. The existence of two different forms of immune-mediated motoneuron destruction suggests that a number of cytoplasmic and membrane antigens may give rise to an immunologically based attack on the motor system.

Demyelination and early remyelination in experimental allergic encephalomyelitis passively transferred with myelin basic protein-sensitized lymphocytes in the Lewis rat

Histological studies were performed on Lewis rats with experimental allergic encephalomyelitis (EAE) passively transferred by myelin basic protein (MBP)-sensitized syngeneic spleen cells in order to determine the relationship between demyelination and neurological signs. Neither inflammation nor demyelination was present on the day prior to the onset of neurological signs but both were present in the spinal roots and spinal cord on the day of onset of tail weakness (4 days after passive transfer). Demyelination and the neurological signs both increased over the next 48 h. There was evidence that the caudal roots were more severely affected than the rostral roots. The peripheral nerves were spared. Demyelination in the spinal cord was concentrated in the dorsal root entry and ventral root exit zones. The initial stages of repair of demyelinated spinal root fibres by Schwann cells were observed on the earliest day that clinical recovery commenced (day 7). At this time some demyelinated fibres were closely associated with debris-free Schwann cells, and occasional fibres were completely invested by 1-2 layers of Schwann cell cytoplasm. Remyelination (compact myelin lamellae formation) by Schwann cells was first observed in the spinal roots on day 9. By the time of complete clinical recovery (day 11) the majority of affected spinal root cores had thin new myelin sheaths. Repair of central nervous system myelin by oligodendrocytes was slower than peripheral nervous system myelin repair. Investment of demyelinated spinal cord axons by oligodendrocytes was observed on day 9, and remyelination by these cells was seen on day 10. We conclude that the neurological signs of passively induced MBP-EAE can be accounted for by demyelination of the lumbar, sacral and coccygeal spinal roots and spinal cord root entry and exit zones, and that the subsequent clinical recovery can be explained by investment and remyelination of demyelinated peripheral and central nervous system fibres by Schwann cells and oligodendrocytes respectively.

Normal rat serum cytotoxicity against syngeneic oligodendrocytes. Complement activation and attack in the absence of anti-myelin antibodies

The role of complement in mediating oligodendrocyte and myelin injury has been investigated by studying the effects of normal adult rat serum on syngeneic cultured neonatal glial cells. Rat serum has cytotoxic activity directed against oligodendrocytes but not astrocytes, the potency of which increases with cell maturation. The effects of heat inactivation, decomplemented rat serum, EGTA treatment, removal of any possible anti-myelin antibody by absorption using syngeneic myelin and absence of surface staining for immunoglobulins on serum-treated oligodendrocytes, C9 depletion and reconstitution, and oligodendrocyte staining for surface C9 demonstrate that this cytotoxicity is mediated by complement via antibody independent activation of the classical pathway and is membrane attack complex dependent. These findings significantly extend the previous demonstration of complement activation by extracted myelin, and may have significance for the pathogenesis of demyelinating diseases.