HLA and amyotrophic lateral sclerosis: a systematic review and meta-analysis

Background: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease associated with loss of upper and lower motor neurones. It leads to death by respiratory failure and has a typical prognosis of 2-3 years. The immune system has been shown to play a role in the pathophysiology of ALS. Some of the most important immune genes are within the human leukocyte antigen (HLA) region, and a recent genome-wide association study (GWAS) has identified a risk allele for ALS within the HLA region. Older studies have also suggested an HLA association with ALS, with certain HLA alleles showing differing expression between patients and controls. This systematic review and meta-analysis examines the previous studies performed in this field.Methods: We used established publication search engines. Findings were excluded if they did not meet the selection criteria. We then undertook statistical meta-analysis on the eligible papers, using a fixed effects model.Results: There were eight eligible papers. There were three statistically significant meta-analysis findings, although these would not be significant after correction for multiple comparisons. The frequencies of HLA-A9 and HLA-DR4 genotypes were lower in ALS subjects than controls, and HLA-B35 was higher in ALS subjects.Discussion: This systematic review and meta-analysis do not confirm all the previously reported associations of HLA with ALS, but shows three alleles of interest. However, there are limitations to the studies, which include the use of older serotyping methodology and the small numbers of subjects. Given the recent GWAS association with HLA, further modern HLA studies are warranted.

Extra-motor abnormalities in amyotrophic lateral sclerosis: another layer of heterogeneity

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease defined by the presence of muscle weakness. The motor features of disease are heterogeneous in site of onset and progression. There are also extra-motor features in some patients. The genetic basis for extra-motor features is uncertain. The heterogeneity of ALS is an issue for clinical trials. Areas covered: This paper reviews the range and prevalence of extra-motor features associated with ALS, and highlights the current information about genetic associations with extra-motor features. Expert commentary: There are extra-motor features of ALS, but these are not found in all patients. The most common is cognitive abnormality. More data is required to ascertain whether extra-motor features arise with progression of disease. Extra-motor features are reported in patients with a range of causative genetic mutations, but are not found in all patients with these mutations. Further studies are required of the heterogeneity of ALS, and genotype/phenotype correlations are required, taking note of extra-motor features.

Serial measurements of phosphorylated neurofilament-heavy in the serum of subjects with amyotrophic lateral sclerosis

There is a need for a blood biomarker of disease activity in ALS. This marker needs to measure the loss of motor neurones. Phosphorylated neurofilament heavy chain (pNfH) in the serum is a biomarker of axonal injury. Previous studies have found that levels of pNfH are elevated in ALS. We have performed a serial study of pNfH levels in 98 subjects from our ALS clinic. There was significant elevation of levels of pNfH in subjects with ALS compared to controls, although there was considerable variability. In studies of individuals who had two or more serial samples, we found that the levels of pNfH increased over time in the early stage of disease. Levels were low in subjects with long survival. The rate of rise of pNfH was inversely correlated with survival. We suggest that the initial level of pNfH is a marker of disease severity and that changes in pNfH levels are markers of disease progression.

Elevation of the terminal complement activation products C5a and C5b-9 in ALS patient blood

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease, characterized by the progressive loss of motor neurons within the central nervous system. Neural degeneration and inflammatory processes, including activation of the complement system are hallmarks of this pathology. Our past work in ALS animal models (hSOD1 G93A rodents) has revealed that blockade of the receptor for complement activation fragment C5a (C5aR), improves ALS-like symptoms and extends survival. We now show that the levels of C5a and C5b-9, but not C3a nor C4a, are significantly elevated in plasma from ALS patients compared to healthy controls. C5a was also elevated within leukocytes from ALS patients suggesting heightened C5a receptor interaction. Overall, these findings indicate that there is enhanced peripheral immune complement terminal pathway activation in ALS, which may have relevance in the disease process.

Gender differences in autoimmune disease

Autoimmune diseases are a range of diseases in which the immune response to self-antigens results in damage or dysfunction of tissues. Autoimmune diseases can be systemic or can affect specific organs or body systems. For most autoimmune diseases there is a clear sex difference in prevalence, whereby females are generally more frequently affected than males. In this review, we consider gender differences in systemic and organ-specific autoimmune diseases, and we summarize human data that outlines the prevalence of common autoimmune diseases specific to adult males and females in countries commonly surveyed. We discuss possible mechanisms for sex specific differences including gender differences in immune response and organ vulnerability, reproductive capacity including pregnancy, sex hormones, genetic predisposition, parental inheritance, and epigenetics. Evidence demonstrates that gender has a significant influence on the development of autoimmune disease. Thus, considerations of gender should be at the forefront of all studies that attempt to define mechanisms that underpin autoimmune disease.

Growth hormone secretion is correlated with neuromuscular innervation rather than motor neuron number in early-symptomatic male amyotrophic lateral sclerosis mice

GH deficiency is thought to be involved in the pathogenesis of amyotrophic lateral sclerosis (ALS). However, therapy with GH and/or IGF-I has not shown benefit. To gain a better understanding of the role of GH secretion in ALS pathogenesis, we assessed endogenous GH secretion in wild-type and hSOD1(G93A) mice throughout the course of ALS disease. Male wild-type and hSOD1(G93A) mice were studied at the presymptomatic, onset, and end stages of disease. To assess the pathological features of disease, we measured motor neuron number and neuromuscular innervation. We report that GH secretion profile varies at different stages of disease progression in hSOD1(G93A) mice; compared with age-matched controls, GH secretion is unchanged prior to the onset of disease symptoms, elevated at the onset of disease symptoms, and reduced at the end stage of disease. In hSOD1(G93A) mice at the onset of disease, GH secretion is positively correlated with the percentage of neuromuscular innervation but not with motor neuron number. Moreover, this occurs in parallel with an elevation in the expression of muscle IGF-I relative to controls. Our data imply that increased GH secretion at symptom onset may be an endogenous endocrine response to increase the local production of muscle IGF-I to stimulate reinnervation of muscle, but that in the latter stages of disease this response no longer occurs.

Impairments to the GH-IGF-I axis in hSOD1G93A mice give insight into possible mechanisms of GH dysregulation in patients with amyotrophic lateral sclerosis

GH deficiency has been found in subjects with amyotrophic lateral sclerosis (ALS). Disrupted endocrine function could contribute to the progressive muscle loss and hypermetabolism seen in ALS. It is not possible to study all the elements of the GH-IGF-I axis in ALS patients. Consequently, it remains unclear whether dysfunctional GH secretion contributes to disease pathogenesis and why GH and IGF-I directed treatment strategies are ineffective in human ALS. The hSOD1(G93A) transgenic mouse model is useful for the detailed investigation of the pathogenesis of ALS. We report that symptomatic male hSOD1(G93A) transgenic mice exhibit a deficiency in GH secretion similar to that seen in human ALS. Further characterization of the GH-IGF-I axis in hSOD1(G93A) mice reveals central and peripheral abnormalities that are not found in wild-type age-matched controls. Specifically, we observe aberrant endogenous pulsatile GH secretion, reduced pituitary GH content, and decreased circulating levels of IGF-I, indicating global GH deficiency in hSOD1(G93A) mice. Furthermore, a reduction in the expression of the IGF-I receptor α-subunit in skeletal muscle and lumbar spinal cords of hSOD1(G93A) mice suggests impaired IGF-I signaling within these tissues. This is the first account of disrupted GH secretion in a transgenic mouse model of ALS. These observations are essential for the development of effective GH and IGF-I targeted therapies in ALS.

The relationship between Bayesian motor unit number estimation and histological measurements of motor neurons in wild-type and SOD1(G93A) mice

OBJECTIVE

To assess the relationship between Bayesian MUNE and histological motor neuron counts in wild-type mice and in an animal model of ALS.

METHODS

We performed Bayesian MUNE paired with histological counts of motor neurons in the lumbar spinal cord of wild-type mice and transgenic SOD1(G93A) mice that show progressive weakness over time. We evaluated the number of acetylcholine endplates that were innervated by a presynaptic nerve.

RESULTS

In wild-type mice, the motor unit number in the gastrocnemius muscle estimated by Bayesian MUNE was approximately half the number of motor neurons in the region of the spinal cord that contains the cell bodies of the motor neurons supplying the hindlimb crural flexor muscles. In SOD1(G93A) mice, motor neuron numbers declined over time. This was associated with motor endplate denervation at the end-stage of disease.

CONCLUSION

The number of motor neurons in the spinal cord of wild-type mice is proportional to the number of motor units estimated by Bayesian MUNE. In SOD1(G93A) mice, there is a lower number of estimated motor units compared to the number of spinal cord motor neurons at the end-stage of disease, and this is associated with disruption of the neuromuscular junction.

SIGNIFICANCE

Our finding that the Bayesian MUNE method gives estimates of motor unit numbers that are proportional to the numbers of motor neurons in the spinal cord supports the clinical use of Bayesian MUNE in monitoring motor unit loss in ALS patients.

The Role of immune and inflammatory mechanisms in ALS

Amyotrophic lateral sclerosis (ALS) is a severe progressive neurodegenerative disease. The cause is unknown, but genetic abnormalities have been identified in subjects with familial ALS and also in subjects with sporadic ALS. Environmental factors such as occupational exposure have been shown to be risk factors for the development of ALS. Patients differ in their clinical features and differ in the clinical course of disease. Immune abnormalities have been found in the central nervous system by pathological studies and also in the blood and CSF of subjects with ALS. Inflammation and immune abnormalities are also found in animals with a model of ALS due to mutations in the SOD1 gene. Previously it has been considered that immune abnormalities might contribute to the pathogenesis of disease. However more recently it has become apparent that an immune response can occur as a response to damage to the nervous system and this can be protective.

Levels of phosphorylated axonal neurofilament subunit H (pNfH) are increased in acute ischemic stroke

For the study of stroke outcomes, there is the need for measurements of severity of stroke damage. Phosphorylated neurofilament heavy protein (pNfH) levels are elevated in axonal injury. We have measured levels of pNfH in stroke and correlated these levels with measures of stroke severity. Blood samples were collected from 54 ischaemic stroke patients at day 1, week 1 (days 7-10) and weeks 3-6, and an ELISA was used to measure pNfH levels in each patient at each time-point. Serum pNfH levels were significantly elevated in stroke patients compared to healthy controls. The levels were low at day 1, higher at day 7 and reached a peak at week 3, the latest day that we assessed. Significant associations were found between the pNfH levels at week 3 and early and stroke severity, size and outcome. Blood pNfH levels that reflect the severity of ischaemic stroke, are correlated with outcome and rise during the weeks after stroke. This may be a useful measure of tissue damage in stroke.

T cells from patients with Guillain-Barré syndrome produce interferon-gamma in response to stimulation with the ganglioside GM1

Guillain-Barré syndrome (GBS) is an acquired demyelinating neuropathy, characterized by infiltration of peripheral nerves with macrophages and T cells. There have been reports of antibodies to glycolipids in GBS. We have previously found T cell reactivity to glycolipids in patients with the demyelinating form of GBS. This study was performed to characterize the cytokines produced by these T cells. Peripheral blood lymphocytes from patients with GBS, chronic inflammatory demyelinating polyradiculoneuropathy, healthy control patients and other neuropathies were incubated with the ganglioside GM1 and transferred to enzyme-linked immunospot plates. The average number per well of spot-forming cells (SFC) in the absence of antigen was counted. The average spontaneous SFC number was subtracted from the average SFC number in the presence of GM1, to produce a corrected SFC. There was significantly increased production of interferon-gamma but not interleukin-5 in response to stimulation with the ganglioside GM1. This could indicate that SFC have a role in pathogenesis of disease.

Immune and inflammatory responses to stroke: good or bad?

Inflammatory and immune responses play important roles following ischaemic stroke. Inflammatory responses contribute to damage and also contribute to repair. Injury to tissue triggers an immune response. This is initiated through activation of the innate immune system. In stroke there is microglial activation. This is followed by an influx of lymphocytes and macrophages into the brain, triggered by production of pro-inflammatory cytokines. This inflammatory response contributes to further tissue injury. There is also a systemic immune response to stroke, and there is a degree of immunosuppression that may contribute to the stroke patient's risk of infection. This immunosuppressive response may also be protective, with regulatory lymphocytes producing cytokines and growth factors that are neuroprotective. The specific targets of the immune response after stroke are not known, and the details of the immune and inflammatory responses are only partly understood. The role of inflammation and immune responses after stroke is twofold. The immune system may contribute to damage after stroke, but may also contribute to repair processes. The possibility that some of the immune response after stroke may be neuroprotective is exciting and suggests that deliberate enhancement of these responses may be a therapeutic option.

Recombinant EPF/chaperonin 10 promotes the survival of O4-positive pro-oligodendrocytes prepared from neonatal rat brain

Chaperonin 10 (cpn 10) is a small heat-shock protein that is usually intracellular. Early pregnancy factor (EPF), a biologically active protein that was first described in the serum of pregnant mammals, is homologous to cpn 10. EPF/cpn 10 has been reported to have effects on immunomodulation and cell survival and to inhibit activation of toll-like receptors by lipopolysaccharide. We found that recombinant EPF/cpn 10 was able to suppress experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, which is a disease causing inflammation and demyelination of the brain and spinal cord. This beneficial effect could be due to anti-inflammatory and/or cell survival properties of EPF/cpn 10. We aimed to assess the effects of cpn 10 on cells of the oligodendrocyte lineage because oligodendrocytes are the brain cells that produce myelin and that are depleted in multiple sclerosis. Two forms of recombinant EPF/cpn 10 were prepared in the pGEX expression system and in the baculovirus expression system. Purified O4(+) pro-oligodendrocytes were prepared from the brains of day-old Wistar rats and isolated by cell sorting with flow cytometry. Single cells were dispensed into micro-well plates and tested for survival in the presence of a range of concentrations of the two forms of cpn 10. We also studied the effects of bFGF, PDGF, IGF-1 and insulin as controls. With cpn 10 present, there was enhanced survival of O4(+) cells.

Postural orthostatic tachycardia syndrome: an underrecognized disorder

BACKGROUND

Postural orthostatic tachycardia syndrome (POTS), a clinical syndrome of orthostatic intolerance characterized by excessive tachycardia and symptoms of cerebral hypoperfusion on standing, is not well recognized in Australia. The aim was to study the clinical symptomatology, results of autonomic testing and outcome in patients with POTS.

METHODS

Sixteen subjects from a tertiary referral centre who met the criteria for POTS were studied between January 2003 and January 2006. Ten of these patients consented to be interviewed using a validated autonomic symptom questionnaire. Heart rate responses to deep breathing and the Valsalva manoeuvre were measured using Colin BP-508 machine (WR Medical Electronic Co., Stillwater, MN, USA). Tilt studies were carried out for 10 min to 80 degrees of head-up tilting. Patient outcome was assessed as functionally normal, able to stand 30 min without symptoms, able to work and carry out recreational activities or worse on follow up.

RESULTS

The mean age of 10 subjects was 24.9 +/- 6.8 years, six being women. The mean duration of symptoms was 70.7 months (range 3-228 months). The common presenting orthostatic symptoms were light-headedness (100%), palpitations (90%), pallor (90%), weakness (80%) and clammy skin (80%). The mean heart rate increment during the tilt study was 51.7 +/- 14.3 b.p.m. The mean duration of follow up was 8.9 months (range 1-16 months). Only five patients were functioning normally at the follow-up visit.

CONCLUSION

POTS is an underrecognized but persistent autonomic disorder in young patients with a variety of symptoms and variable outcome.

Antibody responses to peptides of peripheral nerve myelin proteins P0 and P2 in patients with inflammatory demyelinating neuropathy

BACKGROUND

Antibodies with reactivity to peripheral nerve myelin have previously been found in the serum, and bound to peripheral nerves of patients with Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP).

AIM

To investigate the presence of antibodies reactive to specific peptide sequences within the myelin proteins P0 and P2 in patients with GBS, in patients with CIDP, in healthy controls and in patients with other neuropathies (ON).

METHODS

Blood was obtained from 48 patients with GBS, 36 with CIDP, 48 with ON and 38 controls. ELISA was used to detect antibody responses to peptides of the human peripheral myelin proteins P0 and P2. Blood samples were collected from patients with GBS in early, peak and recovery stages of GBS to analyse antibody levels throughout the course of the disease.

RESULTS

Significantly increased total IgG levels were found in patients with GBS compared with other groups. A higher percentage of patients with GBS at the peak of disease had antibody reactivity to P2(14-25) compared with patients with CIDP and control groups. In patients with GBS and CIDP, the percentages of patients with antibody reactivity to P2(61-70), and peptides derived from P0, were comparable to the control groups. Although some individual patients with GBS had high titres of reactivity to the peptide antigens tested, most patients with GBS and CIDP had levels of antibody similar to controls.

CONCLUSION

Our data suggest that increased IgG levels and increased antibody reactivity to P2(14-25) in patients with GBS at the peak of disease may play a contributory role in the disease process in some patients with demyelinating forms of GBS.

The stimulus–response curve and motor unit variability in normal subjects and subjects with amyotrophic lateral sclerosis

The behavior and stability of motor units (MUs) in response to electrical stimulation of different intensities can be assessed with the stimulus-response curve, which is a graphical representation of the size of the compound muscle action potential (CMAP) in relation to stimulus intensity. To examine MU characteristics across the whole stimulus range, the variability of CMAP responses to electrical stimulation, and the differences that occur between normal and disease states, the curve was studied in 11 normal subjects and 16 subjects with amyotrophic lateral sclerosis (ALS). In normal subjects, the curve showed a gradual increase in CMAP size with increasing stimulus intensity, although one or two discrete steps were sometimes observed in the upper half of the curve, indicating the activation of large MUs at higher intensities. In ALS subjects, large discrete steps, due to loss of MUs and collateral sprouting, were frequently present. Variability of the CMAP responses was greater than baseline variability, indicating variability of MU responses, and at certain levels this variability was up to 100 microVms. The stimulus-response curve shows differences between normal and ALS subjects and provides information on MU activation and variability throughout the curve.

T cell reactivity to P0, P2, PMP-22, and myelin basic protein in patients with Guillain-Barre syndrome and chronic inflammatory demyelinating polyradiculoneuropathy

OBJECTIVES

It has been suggested that autoimmunity to peripheral myelin proteins is involved in the pathogenesis of Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). We aimed to compare reactivity of peripheral blood mononuclear cells (PBMC) to antigens of peripheral myelin proteins in patients with GBS and patients with CIDP with that of healthy controls and patients with other non-immune mediated neuropathies (ON).

METHODS

We prepared PBMC from blood from 83 healthy controls and from 64 patients with GBS, 54 with CIDP, and 62 with ON. PBMC were tested in antigen specific proliferation assays against peptides from myelin proteins P0, P2, PMP22, and myelin basic protein (MBP), which is identical to myelin P1, and against whole human MBP. Interferon-gamma (IFN-gamma) and interleukin (IL)-5 enzyme linked immunospot (ELISPOT) assays were also performed in some subjects to assess spontaneous and peripheral myelin antigen specific PBMC cytokine secretion.

RESULTS

Antigen specific PBMC proliferation assays showed no significant elevation of peptide specific T cell responsiveness in patients with GBS or CIDP compared with healthy controls or patients with ON. Levels of spontaneous ELISPOT IFN-gamma secretion were increased in patients with GBS and significantly increased in those with CIDP compared with healthy controls and patients with ON. No convincing differences in antigen specific ELISPOT IFN-gamma secretion levels to individual peptides were detectable in patients with GBS. The proportion of patients with CIDP with an increased number of PBMC producing IFN-gamma in response to peptide PMP-22(51-64) was significantly increased compared with healthy controls and patients with ON. No significant differences in antigen specific ELISPOT IL-5 secretion levels were detectable in patients with GBS or CIDP compared with controls, but levels of spontaneous IL-5 secretion were significantly higher in patients with CIDP than in healthy controls or patients with ON.

CONCLUSIONS

Although the lack of significantly increased antigen specific PBMC proliferation in GBS and CIDP does not support a role for T cells, the more sensitive ELISPOT technique detected increased numbers of PBMC secreting IFN-gamma spontaneously in 25% of patients with GBS, providing further evidence for a role of T cells in the immunopathology of GBS. Increased numbers of spontaneous IFN-gamma and IL-5 secreting cells, and increased IFN-gamma secretion in response to PMP-22(51-64), in patients with CIDP provide further evidence for a role of myelin specific T cells in CIDP.

The effects of pregnancy on myelin basic protein-induced experimental autoimmune encephalomyelitis in Lewis rats: suppression of clinical disease, modulation of cytokine expression in the spinal cord inflammatory infiltrate and suppression of lymphocyte proliferation by pregnancy sera

PROBLEM

The present study was performed to explore the effects of pregnancy on experimental autoimmune encephalomyelitis (EAE) induced in Lewis rats by inoculation with myelin basic protein (MBP) (MBP-EAE).

METHOD OF STUDY

MBP-EAE was induced in pregnant and non-pregnant rats and severity of disease evaluated. Serum from pregnant and non-pregnant rats was used in standard lymphocyte proliferation assays. Real-time polymerase chain reaction (PCR) was used to investigate the expression of cytokine mRNA in the inflammatory cells obtained from the spinal cord of rats on day 15 after inoculation.

RESULTS

Pregnant rats developed less severe disease than non-pregnant rats. Serum from pregnant rats suppressed the proliferation of T lymphocytes in response to MBP. There was significantly increased expression of IL-4, IL-10 and TNF-alpha mRNA in the spinal cord infiltrate of pregnant rats.

CONCLUSION

Circulating humoral factors and alteration in cytokine production by inflammatory cells may contribute to the suppression of EAE in pregnant rats.

Cyclosporin A treatment modulates cytokine mRNA expression by inflammatory cells extracted from the spinal cord of rats with experimental autoimmune encephalomyelitis induced by inoculation with myelin basic protein

In Lewis rats, treatment with high doses of cyclosporin A (CsA) suppresses clinical signs of experimental autoimmune encephalomyelitis (EAE), although disease occurs when treatment is ceased. Treatment with low doses of CsA causes EAE to take a chronic relapsing course. We have previously shown that CsA treatment causes a decline in the number of T cells and increased inflammatory cell apoptosis in the spinal cord. The present study was undertaken to assess whether CsA therapy also modulates cytokine mRNA expression by inflammatory cells in the spinal cord of rats with EAE, looking for changes that might contribute to the observed effects of CsA on the course of EAE. EAE was induced in Lewis rats by inoculation with myelin basic protein and adjuvants. At the peak of neurological signs, on day 14 after inoculation, rats were given a single intraperitoneal injection of saline, or CsA at a dose of 8, 16, 32 or 64 mg/kg. The next day, rats were sacrificed, the spinal cords removed, inflammatory cells were extracted from the cords, and mRNA isolated from these cells. Expression of cytokine mRNA was assessed by semi-quantitative reverse transcription polymerase chain reaction (PCR) and by quantitative real-time PCR. With both techniques, we found that CsA suppressed the expression of interferon-gamma mRNA and interleukin-2 (IL-2) mRNA. With real-time PCR, we found that CsA caused significantly increased expression of transforming growth factor-beta mRNA. With the different techniques, we observed no consistent pattern of alteration of expression of interleukin-10 or interleukin-4 mRNA. It is possible that these changes in cytokine mRNA expression contribute to the modulation of the clinical course of EAE that is produced by CsA treatment.

Early pregnancy factor suppresses experimental autoimmune encephalomyelitis induced in Lewis rats with myelin basic protein and in SJL/J mice with myelin proteolipid protein peptide 139-151

Early pregnancy factor (EPF) is a secreted protein with immunosuppressive and growth factor properties. During pregnancy, it appears in maternal serum within 6-24 h of fertilization, is present for at least the first two-thirds of pregnancy in all species studied and is essential for embryonic survival. It is a homologue of chaperonin 10, a heat shock protein, but, unlike other members of this family, EPF has an extracellular role. As it has the ability to modulate CD4+ T cell-dependent immune responses, its role in treatment of experimental autoimmune encephalomyelitis (EAE) was investigated. EAE is a CD4+ T cell-mediated disease, the best available animal model of multiple sclerosis (MS). Two models of EAE were investigated, acute EAE induced in Lewis rats by inoculation with myelin basic protein (MBP-EAE) and chronic relapsing EAE induced in SJL/J mice by inoculation with myelin proteolipid protein peptide (residues 139-151) (PLP-EAE). EPF, delivered intraperitoneally or orally to rats or intraperitoneally to mice, suppressed clinical signs of disease. Mice with PLP-EAE were also treated with interferon-beta, with and without EPF. Both EPF and IFN-beta suppressed clinical signs of EAE and, when administered together, gave greater suppression than when given separately. These findings suggest that EPF may be a potential candidate for use in treatment of MS and may be of use in combined therapy with IFN-beta.

Surges of increased T cell reactivity to an encephalitogenic region of myelin proteolipid protein occur more often in patients with multiple sclerosis than in healthy subjects

We have previously shown that patients with multiple sclerosis (MS) have increased T cell responses to the immunodominant region (residues 184-209) of myelin proteolipid protein (PLP). The present study investigated whether this reactivity fluctuates over time and correlates with disease activity. We performed monthly limiting dilution assays for 12-16 mo in four healthy subjects and five patients with relapsing-remitting MS to quantify the frequencies of circulating T cells proliferating in response to PLP(41-58), PLP(184-199), PLP(190-209), myelin basic protein (MBP), MBP(82-100), and tetanus toxoid. Disease activity was monitored by clinical assessment and gadolinium-enhanced magnetic resonance imaging of the brain. There were fluctuations in the frequencies of autoreactive T cells in all subjects. Compared with healthy controls, MS patients had significantly more frequent surges of T cells reactive to the 184-209 region of PLP, but infrequent surges of T cell reactivity to MBP(82-100). There was temporal clustering of the surges of T cell reactivity to MBP(82-100) and MBP, suggesting T cell activation by environmental stimuli. Some clinical relapses were preceded by surges of T cell reactivity to PLP(184-209), and in one patient there was significant correlation between the frequency of T cells reactive to PLP(184-199) and the total number of gadolinium-enhancing magnetic resonance imaging lesions. However, other relapses were not associated with surges of T cell reactivity to the Ags tested. T cells reactive to PLP(184-209) may contribute to the development of some of the CNS lesions in MS.

Results of testing for anti-GM1 antibodies

We used an ELISA technique to measure IgG and IgM antibodies to the ganglioside GM1, with the results expressed in arbitrary units. We tested 1007 sera from patients with peripheral neuropathy or muscle weakness. For IgG and IgM antibodies, the distribution of results differed significantly from a normal distribution. In the patient group, 81 of 1007 sera had elevated levels of IgG antibodies (> 10 units). Of these, 11 patients had very high levels (> 50 units). These 11 patients had diagnoses of GBS (4), motor neurone disease (3) or non-specific idiopathic neuropathy (4). For IgM antibodies, 115 of 1007 sera were positive (> 20 units). Of these, 18 patients had very high levels (> 50 units). These 18 patients had diagnoses of Guillain-Barré syndrome or Miller Fisher syndrome (4), multifocal motor neuropathy (4), motor neurone disease (2), non-specific neuropathy (2). We conclude that anti-GM1 antibodies in high titre are uncommon. Patients with multifocal motor neuropathy have high levels of antibody. However, patients with other disorders may also have high levels, so that anti-GM1 antibody levels alone are not a specific test for multifocal motor neuropathy. We found that antibodies to GM1 were present in the sera of patients with chronic idiopathic neuropathy, leading us to suggest that these antibodies may sometimes arise as a secondary response to disease.

Chronic inflammatory demyelinating polyradiculoneuropathy and severe peripheral oedema: a renal explanation

Inflammatory demyelinating neuropathies have been associated with membranous and focal sclerosing glomerulonephritis. Here we describe a 58 year old man with a clinical history, physical examination and laboratory investigations consistent with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), who also had severe lower limb and sacral oedema resistant to medical therapy. Mild proteinuria was present and a renal biopsy showed features consistent with focal sclerosing glomerulonephritis (FSGN). The patient's weakness and oedema did not respond to i.v. immunoglobulin or plasmapheresis but responded to high dose oral prednisone. The oedema was not explained by immobility, hypoproteinaemia or local factors. The occurrence of the oedema in a person with CIDP and FSGN and its improvement with prednisone, together with improvement in CIDP and FSGN, suggests that it was immune mediated, possibly due to increased capillary permeability. The presence of renal disease in patients with inflammatory demyelinating neuropathies may be more common than currently realised.

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.

Cytokine expression by inflammatory cells obtained from the spinal cords of Lewis rats with experimental autoimmune encephalomyelitis induced by inoculation with myelin basic protein and adjuvants

Inflammatory cells were obtained from the spinal cords of rats with acute experimental autoimmune encephalomyelitis (EAE) induced by inoculation with myelin basic protein (MBP) and adjuvants. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to investigate the expression of mRNA for interleukin-2 (IL-2), IL-4, IL-10 and interferon-gamma (IFN-gamma) by cells from groups of rats studied 10-21 days after inoculation. On all days of study, the inflammatory cells, which were predominantly lymphocytes, expressed mRNA for IL-2, IL-4, IL-10 and IFN-gamma. In the mRNA from normal rat spinal cord tissue, there was little expression of cytokine mRNA. Cells from a short-term MBP-reactive T cell line expressed all the cytokines. Densitometry was used to measure the products of PCR, to assess the expression of each cytokine relative to that of beta-actin. IL-2 mRNA was expressed throughout the course of disease and reached a peak on day 18, during late clinical recovery. IFN-gamma was expressed throughout the course of the disease and was also high during late recovery. IL-4 mRNA was present in the spinal cord throughout the course of the disease, with a slight rise during late recovery. Relative expression of IL-10 rose to a peak on days 17-19, during late recovery from clinical disease. This study indicates that IL-2, IL-4, IL-10 and IFN-gamma are expressed by inflammatory cells in the spinal cord in EAE, with the relative expression of all cytokines being high during late clinical recovery.

Microglia are more susceptible than macrophages to apoptosis in the central nervous system in experimental autoimmune encephalomyelitis through a mechanism not involving Fas (CD95)

Morphological studies have shown that macrophages and microglia undergo apoptosis in the central nervous system (CNS) in acute experimental autoimmune encephalomyelitis (EAE) in the Lewis rat. To assess the relative levels of macrophage and microglial apoptosis, and the molecular mechanisms involved in this process, we used three-colour flow cytometry to identify CD45lowCD11b/c+ microglial cells and CD45highCD11b/c+ macrophages in the inflammatory cells isolated from the spinal cords of Lewis rats 13 days after immunization with myelin basic protein (MBP) and complete Freund's adjuvant. Simultaneously, we analyzed the DNA content of these cell populations to assess the proportions of cells undergoing apoptosis and in different stages of the cell cycle or examined their expression of three apoptosis-regulating proteins, i.e. Fas (CD95), Fas ligand (FasL) and Bcl-2. Microglia were highly vulnerable to apoptosis and were over-represented in the apoptotic population. Macrophages were less susceptible to apoptosis than microglia and underwent mitosis more frequently than microglia. The different susceptibilities of microglia and macrophages to apoptosis did not appear to be due to variations in Fas, FasL or Bcl-2 expression, as the proportions of microglia and macrophages expressing these proteins were similar, and were relatively high. Furthermore, in contrast to T cell apoptosis, apoptosis of microglia/macrophages did not occur more frequently in cells expressing Fas or FasL, or less frequently in cells expressing Bcl-2. These results indicate that the apoptosis of microglia and CNS macrophages in EAE is not mediated through the Fas pathway, and that Bcl-2 expression does not protect them from apoptosis. Expression of FasL by macrophages and microglia may contribute to the pathogenesis and immunoregulation of EAE through interactions with Fas+ oligodendrocytes and Fas+ T cells. The high level of microglial apoptosis in EAE indicates that microglial apoptosis may be an important homeostatic mechanism for controlling the number of microglia in the CNS following microglial activation and proliferation.

Increased immunoreactivity to two overlapping peptides of myelin proteolipid protein in multiple sclerosis

We tested the proliferative responses of peripheral blood mononuclear cells from 61 patients with multiple sclerosis, 56 healthy control subjects and 52 patients with other neurological diseases to seven synthetic peptides of myelin proteolipid protein (PLP) and 19 synthetic peptides of myelin basic protein (MBP). Increased proliferative responses to two overlapping PLP peptides, PLP184-199 and PLP190-209 were found significantly more frequently in blood from patients with relapsing-remitting or secondary progressive multiple sclerosis (52.3%), but not from those with primary progressive multiple sclerosis (18.2%), than in that from healthy control subjects (8.9%) and patients with other neurological diseases (20.8%). Reactivity to these PLP peptides was most frequently seen in blood from patients with multiple sclerosis of 6-15 years duration and with moderate to severe disability (Kurtzke's Expanded Disability Status Scale > 4.0); the blood from 15 of 19 patients in this group reacted to one or both of the peptides. Both peptides could be recognized by short-term T-cell lines specific for whole PLP, and lines specific for one or other of the two overlapping peptides were able to recognize whole PLP, indicating that these peptides can be processed naturally from the intact molecule. This region of PLP is encephalitogenic in a number of strains of mice. Samples from multiple sclerosis patients did not react more frequently to any of the MBP peptides than those from healthy control subjects. The proportions of patients with other neurological diseases whose blood responded to the MBP peptides that most frequently elicited responses in blood from multiple sclerosis patients were significantly lower than the proportions of multiple sclerosis patients and healthy control subjects whose blood responded to these peptides.

Increased apoptosis of T lymphocytes and macrophages in the central and peripheral nervous systems of Lewis rats with experimental autoimmune encephalomyelitis treated with dexamethasone

Using light and electron microscopic histological and immunocytochemical techniques, we investigated the effects of the glucocorticoid dexamethasone on T cell and macrophage apoptosis in the central nervous system (CNS) and peripheral nervous system (PNS) of Lewis rats with acute experimental autoimmune encephalomyelitis (EAE) induced with myelin basic protein (MBP). A single subcutaneous injection of dexamethasone markedly augmented T cell and macrophage apoptosis in the CNS and PNS and microglial apoptosis in the CNS within 6 hours (h). Pre-embedding immunolabeling revealed that dexamethasone increased the number of apoptotic CD5+ cells (T cells or activated B cells), alphabeta T cells, and CD11b+ cells (macrophages/microglia) in the meninges, perivascular spaces, and CNS parenchyma. The induction of increased apoptosis was dose-dependent. Daily dexamethasone treatment suppressed the neurological signs of EAE. However, the daily injection of a dose of dexamethasone (0.25 mg/kg), which, after a single dose, did not induce increased apoptosis in the CNS or PNS, was as effective in inhibiting the neurological signs of EAE as the high dose (4 mg/kg), which induced a marked increase in apoptosis. This indicates that the beneficial clinical effect of glucocorticoid therapy in EAE does not depend on the induction of increased apoptosis. The daily administration of dexamethasone for 5 days induced a relapse that commenced 5 days after cessation of treatment, with the severity of the relapse tending to increase with dexamethasone dosage.

Corticosteroid treatment of experimental autoimmune encephalomyelitis in the Lewis rat results in loss of V beta 8.2+ and myelin basic protein-reactive cells from the spinal cord, with increased total T-cell apoptosis but reduced apoptosis of V beta 8.2+ cells

We have studied the effects of corticosteroid treatment on the numbers of lymphocytes obtained from the spinal cords of Lewis rats with acute experimental autoimmune encephalomyelitis (EAE) induced by inoculation with myelin basic protein (MBP) and adjuvants. Flow cytometric studies showed that treatment with dexamethasone (4 mg/kg) 8-12 h prior to study on day 14 after inoculation resulted in a reduction in the numbers of CD5+, TCR alpha beta + and V beta 8.2+ cells in the spinal cord. Limiting dilution analysis indicated that dexamethasone treatment 12 h prior to study on day 12 after inoculation reduced the frequencies of MBP-reactive and interleukin-2-responsive lymphocytes in the spinal cord to low levels, but reduced the frequency of concanavalin-A-responsive lymphocytes to a lesser extent. Using propidium iodide staining of nuclear chromatin we also studied lymphocyte apoptosis. Greater numbers of apoptotic cells were found in the cells extracted from the spinal cords of rats, examined on day 14, that had been treated 1-12 h previously with dexamethasone, than in saline-treated controls. This increased level of apoptosis was observed in the CD5+ and TCR alpha beta + cell populations. At 1-4 h after dexamethasone treatment there was a reduction in the selective apoptosis of V beta 8.2+ cells that normally occurs during spontaneous recovery from EAE. Therefore apoptosis of V beta 8.2+ cells cannot explain the reduction in the numbers of V beta 8.2+ cells and MBP-reactive cells in the CNS after dexamethasone treatment. By 8-12 h after dexamethasone treatment the selectivity of the apoptotic process was restored. These studies suggest that a reduction in the number of T-lymphocytes in the central nervous system contributes to the beneficial effects of corticosteroids in EAE.

A study of human T-cell lines generated from multiple sclerosis patients and controls by stimulation with peptides of myelin basic protein

We generated T-cell lines from the peripheral blood of controls and of patients with multiple sclerosis (MS) by stimulation with overlapping synthetic peptides representing the entire sequences of all four isoforms of human myelin basic protein (MBP). The T-cell lines reacted to a wide range of epitopes in the major isoforms of MBP and to epitopes that were present only in the minor isoforms. Many MS patients and controls had T-cells responding to one or more cryptic MBP epitopes, as indicated by the generation of a peptide-specific T-cell line(s) by stimulation with synthetic peptides but not by stimulation with whole MBP. About one-third of the peptide-generated lines were cytotoxic. Although we have shown that this technique of peptide stimulation is effective in generating human antiviral cytotoxic CD8+ T-cell lines, all the cytotoxic MBP-specific lines generated by this method were predominantly CD4+. Our study did not reveal any significant differences, between MS patients and controls, in reactivity to epitopes within any of the isoforms of MBP.

Apoptosis of V beta 8.2+ T lymphocytes in the spinal cord during recovery from experimental autoimmune encephalomyelitis induced in Lewis rats by inoculation with myelin basic protein

To study T cell apoptosis during spontaneous recovery from experimental autoimmune encephalomyelitis (EAE), we extracted lymphocytes from the spinal cords of Lewis rats with EAE induced by inoculation with myelin basic protein (MBP) and adjuvants. Using flow cytometry we assessed the numbers of CD5+ and TCR alpha beta + lymphocytes, as well as V beta 8.2+ lymphocytes, which constitute the predominant encephalitogenic MBP-reactive cells in Lewis rats. Rats developed neurological signs of disease 10-12 days after inoculation. The peak of disease was on day 14 after inoculation and was followed by clinical recovery. The numbers of CD5+, TCR alpha beta + and V beta 8.2+ cells obtained from the spinal cord were greatest on day 13. During spontaneous clinical recovery, there was a decline in the numbers of all the cells studied, with a selective loss of V beta 8.2+ cells from the CD5+ and TCR alpha beta + populations. To determine whether the decline in lymphocyte numbers was due to apoptosis, we used simultaneous surface labelling and propidium iodide staining of the DNA of the cells extracted from the spinal cord. From day 14 onwards, there was selective enrichment of V beta 8.2+ cells in the apoptotic population, and the percentage of V beta 8.2+ cells undergoing apoptosis was greater than the percentages of CD5+ and TCR alpha beta + cells undergoing apoptosis. These findings indicate that recovery from acute EAE is associated with the selective apoptosis, in the central nervous system, of these disease-relevant cells. The findings in this study of actively induced EAE are similar to those of our previous study of EAE induced by transfer of encephalitogenic MBP-specific T cells (Z. Tabi et al., Eur. J. Immunol. 24: 2609-2617, 1994) and further support the hypothesis that selective apoptosis of autoreactive T cells in the central nervous system is of primary importance in spontaneous recovery from EAE.

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.

Antigen-specific down-regulation of myelin basic protein-reactive T cells during spontaneous recovery from experimental autoimmune encephalomyelitis: further evidence of apoptotic deletion of autoreactive T cells in the central nervous system

Experimental autoimmune encephalomyelitis (EAE) was induced in Lewis rats by the i.v. injection of 10(7) cloned V beta 8.2+ T cells specific for the 72-89 peptide of guinea pig myelin basic protein (MBP). Some animals were injected simultaneously with 10(7) cloned T cells specific for ovalbumin (OVA). Lymphocytes were isolated from the spinal cord and from the peripheral lymphoid organs of these rats and the frequencies of MBP-peptide-specific or OVA-specific proliferating cells were estimated by limiting dilution analysis at different times after cell transfer. The frequencies of cells specific for MBP72-89 or OVA in the spinal cord were highest 5 days after cell transfer (MBP72-89, 1 in 1149; OVA, 1 in 1116). On day 7, when the rats were recovering, the frequency of cells specific for MBP72-89 in the spinal cord fell dramatically to < 1 in 10(5), while that of OVA-specific cells decreased to a much lesser extent (1 in 7001). The frequencies of MBP72-89-specific cells in the peripheral lymphoid organs during and after recovery were also much lower than those of OVA-specific cells. A similar pattern of down-regulation of the MBP-peptide-specific, but not the OVA-specific, T cell response was observed in the spleen and mesenteric lymph nodes (MLN) of rats 38 days after the active induction of EAE by immunization with equal amounts of MBP and OVA in adjuvants. In the passively transferred model, cells isolated from the spinal cord and MLN on day 7 did not regain responsiveness to MBP72-89 after incubation with high levels of IL-2, indicating that the unresponsiveness was not due to T cell anergy. Thus this study demonstrates that there is a specific down-regulation of the MBP72-89-specific T cell response during spontaneous recovery from EAE.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Apoptotic elimination of V beta 8.2+ cells from the central nervous system during recovery from experimental autoimmune encephalomyelitis induced by the passive transfer of V beta 8.2+ encephalitogenic T cells

A CD4+V beta 8.2+ T cell clone specific for the peptide 72-89 of guinea pig myelin basic protein (GMBP) was used to induce acute experimental autoimmune encephalomyelitis (EAE) in Lewis rats. To assess apoptosis in inflammatory cells infiltrating the central nervous system (CNS), we extracted cells from the spinal cord, enriched them for T cells and performed flow-cytometric analysis of their DNA stained with propidium iodide. The presence of apoptosis was confirmed by the demonstration of DNA fragmentation on gel electrophoresis. A gradual increase in the proportion of apoptotic cells was observed between 4 and 7 days after the transfer of the encephalitogenic T cells. The highest frequency of apoptotic cells (9.2 +/- 1.2%) was observed 7 days after cell transfer, when clinical recovery commenced. Passive transfer of ovalbumin-specific cells resulted in only a background level (0.8%) of apoptosis in the CNS. We conclude that the apoptotic process selectively eliminates autoreactive T cells from the CNS as: (a) there was a selective disappearance of disease-relevant CD5+V beta 8.2+ cells from the CNS during the course of EAE; (b) there was a decrease in the frequency of CNS-infiltrating T cells reactive to the GMBP 72-89 peptide during the course of EAE, and in a standard proliferation assay there was a loss of in vitro reactivity of CNS-infiltrating cells to this peptide, but not to a non-CNS antigen (ovalbumin); (c) simultaneous surface labeling and DNA analysis of CNS-infiltrating cells revealed that the frequency of V beta 8.2+ cells was about sevenfold higher in the apoptotic T cell population than in the normal (non-apoptotic) T cell population; and (d) we were unable to detect recirculation of the V beta 8.2+ cells to lymphoid organs after their frequency decreased in the CNS. The selective apoptotic elimination of autoreactive T cells from the target organ of this spontaneously resolving autoimmune disease may have implications for the understanding of the mechanism by which an autoimmune attack is terminated and for the design of therapeutic strategies to facilitate this process.

Conduction abnormalities are restricted to the central nervous system in experimental autoimmune encephalomyelitis induced by inoculation with proteolipid protein but not with myelin basic protein

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory demyelinating disease of the central nervous system (CNS) and can be induced by inoculation of animals with homogenized CNS tissue or highly purified myelin proteins such as myelin basic protein (MBP) or proteolipid protein (PLP). It is widely studied as a possible animal model of multiple sclerosis. We performed the present neurophysiological study to define the location of nerve conduction abnormalities in EAE induced by immunization with PLP (PLP-EAE) and in EAE induced by immunization with MBP (MBP-EAE) in the Lewis rat. In rats with tail weakness due to acute PLP-EAE, conduction was normal in the spinal nerve roots and peripheral nerves but there was evidence of conduction block in a high proportion of the fibres in the dorsal columns of the lumbosacral spinal cord. In contrast, in acute MBP-EAE, there was conduction block in a high proportion of fibres in the sacral dorsal and ventral roots of the peripheral nervous system (PNS) and in the dorsal columns of the lumbosacral spinal cord. The distribution of nerve conduction abnormalities is consistent with previous histological studies showing that inflammation and primary demyelination are restricted to the CNS in PLP-EAE, but are present in the CNS and in the spinal roots of the PNS in MBP-EAE. The restriction of functional abnormalities to the CNS in PLP-EAE but not in MBP-EAE may have implications for the human inflammatory demyelinating diseases, including multiple sclerosis.

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.

Inflammatory cells, microglia and MHC class II antigen-positive cells in the spinal cord of Lewis rats with acute and chronic relapsing experimental autoimmune encephalomyelitis

Chronic relapsing experimental autoimmune encephalomyelitis (CR-EAE) was induced in Lewis rats by inoculation with guinea pig spinal cord and adjuvants and treatment with low dose cyclosporin A (CsA). Acute EAE was induced by the same method without CsA treatment. Immunocytochemistry and flow cytometry were used to assess inflammatory cells and MHC class II (Ia) antigen expression in the central nervous system of these rats. The inflammatory infiltrate was composed mainly of CD4+ T cells and macrophages, and alpha beta T cells constituted about 65% of the CD2+ T cells. After recovery from acute EAE and during the first remission of CR-EAE, the number of T cells was significantly less than in the preceding episodes. The number of T cells was higher in the second episode of CR-EAE than in the first remission. Throughout the course of CR-EAE, the majority of the CD2+ T cells were CD45RC-. The ratio of IL-2R+ cells to CD2+ cells ranged from 10.5 to 24.0%. The ratio of CD4+ T cells to B cells was lower in the later episodes of CR-EAE than in the first episode. Ia antigen was expressed on infiltrating round cells at all stages of CR-EAE and on microglial cells (identified by dendritic morphology) with increasing intensity throughout the course of CR-EAE. With flow cytometry, the number of Ia+ cells obtained from the spinal cord rose throughout the course of CR-EAE. The number of FSClowOX1low cells, which we consider represent microglia, also increased during the course of CR-EAE.

Macrophage apoptosis in the central nervous system in experimental autoimmune encephalomyelitis

Using light and electron microscopy, we have demonstrated that macrophage apoptosis (programmed cell death) occurs in the central nervous system (CNS) in Lewis rats with acute experimental autoimmune encephalomyelitis (EAE) and chronic relapsing EAE. Apoptotic macrophages were identified by the presence of an apoptotic nucleus in a cell with cytoplasm containing myelin debris but no intermediate filaments. They were found in the meninges, perivascular spaces and in the parenchyma of the white and grey matter of the spinal cord. In acute EAE the apoptotic macrophages were most frequently seen at the time of maximal neurological signs and during the early stages of clinical recovery. Several possible mechanisms may be responsible for the macrophage apoptosis: the release or withdrawal of cytokines; T-cell cytotoxicity; the effect of activated macrophage products, such as nitric oxide; and a direct effect of endogenous glucocorticoids. Macrophage apoptosis, together with the T-cell apoptosis we have previously described in the CNS in EAE, may contribute to the down-regulation of this autoimmune disease.

Expression of CD45RC and Ia antigen in the spinal cord in acute experimental allergic encephalomyelitis: an immunocytochemical and flow cytometric study

We performed immunocytochemical studies to analyze the inflammatory infiltrate and major histocompatibility complex class II (Ia) antigen expression in the spinal cord of Lewis rats with acute experimental allergic encephalomyelitis (EAE) induced by inoculation with myelin basic protein and adjuvants. Using antibodies to lymphocyte markers and other monoclonal antibodies we found that during clinical episodes the inflammatory infiltrate was chiefly composed of T lymphocytes and macrophages. The majority of cells in the inflammatory infiltrate were stained by the W3/25 antibody to CD4 and a proportion was stained by OX22 which labels the high molecular weight form of the leucocyte common antigen (CD45RC). CD8+ T cells were sparse and B cells were not detected. There was minimal staining with the OX39 antibody to the interleukin-2 receptor. Presumptive microglia, identified by their dendritic morphology, expressed Ia antigen during the clinical episodes and after recovery. The prominence of Ia antigen expression after recovery could indicate that this Ia expression was associated with downregulation of the encephalitogenic immune response. We also performed flow cytometry studies on cells extracted from the spinal cord of rats before and during attacks of EAE. With flow cytometry, we found that in established disease a mean of 83(SD, 23)% of CD2+ cells were CD4+, and a mean of 27(SD, 12)% of CD2+ cells were CD45RC+. In rats sampled on the first day of signs, a mean of 43(SD, 22)% of CD2+ cells were CD45RC+. In the cells extracted from the spinal cord of rats with established disease a mean of 47(SD, 32)% of macrophages were CD45RC+. Our study has combined an immunocytochemical assessment of tissue sections with quantitative flow cytometry assessment of cells extracted from the spinal cord of rats with acute EAE. We have shown that the majority of T lymphocytes in the spinal cord are CD45RC-. We have also found prominent Ia expression on dendritic cells in acute EAE and after clinical recovery.

Apoptosis of alpha beta T lymphocytes in the nervous system in experimental autoimmune encephalomyelitis: its possible implications for recovery and acquired tolerance

We have recently shown that apoptosis, an active process of cellular self-destruction, occurs in the central nervous system in Lewis rats with acute experimental autoimmune encephalomyelitis (EAE) induced by inoculation with myelin basic protein (MBP) and adjuvants. Conventional light and electron microscopic studies suggested that some of the apoptotic cells were oligodendrocytes and that others were hematogenous mononuclear cells. To determine whether any of the apoptotic cells were T lymphocytes, we used the technique of pre-embedding immunolabelling which allows sufficient preservation of the ultrastructure to permit recognition of apoptotic changes while at the same time preserving surface antigens so that the identity of the apoptotic cells can be determined by immunocytochemistry. Light microscopic immunocytochemistry using the monoclonal antibodies OX-34 (CD2) and R73 (alpha beta T-cell receptor) revealed that 10% of the CD2+ cells and 5% of the alpha beta T lymphocytes in the parenchyma of the spinal cord were dying by apoptosis. The presence of apoptotic alpha beta T cells was confirmed by electron microscopy. About half of all the apoptotic cells within the spinal cord were labelled by these antibodies. It is possible that some of the unlabelled apoptotic cells were also T lymphocytes but that others were glial cells such as oligodendrocytes. One possible interpretation of this T-cell apoptosis is that it represents activation-induced cell death, which has recently been shown to provide a mechanism of clonal elimination of mature as well as immature autoreactive T cells. Another possible interpretation is that it is a result of corticosterone released during the course of EAE. The apoptotic elimination of target-antigen-specific lymphocytes within the target organ in this autoimmune disease may contribute to the subsidence of inflammation and, if ongoing, to the development of tolerance.