A human anti-neuronal autoantibody against GABAB receptor induces experimental autoimmune agrypnia

In the serum and cerebrospinal fluid of a patient with recurrent acute episodes of respiratory crises, autonomic symptoms and total insomnia (agrypnia), we identified a novel anti-neural complement fixing antibody directed against GABA(B) receptor (GABA(B)R). Patient purified IgG recognized a band of approximately 110 kDa on protein extracts of mouse cerebellum, cortex and brainstem and immunolabelled cultured Chinese hamster ovary (CHO) cells, transfected with human GABA(B)R1 and rat GABA(B)R2 receptors. Western blot analysis of transfected CHO homogenates showed the same band using both patient purified IgG and anti-GABA(B)R1 antibody. In order to verify the pathogenic role of these purified antibodies, we injected patient IgG intrathecally into cisterna magna of C57BL/6 mice pre-implanted with EEG electrodes and we observed severe ataxia followed by breathing depression and total suppression of slow wave sleep, as evidenced by EEG recording, in a dose-dependent manner. Immunohistochemistry on brain sections of mice injected with patient IgG showed the simultaneous presence of bound human IgG and C5b-9 deposits on Purkinje cells and cerebellar granular layer. After incubation with anti-GABA(B)R antibody, a marked reduction of receptor immunostaining was found with relative sparing of neuronal architecture. In conclusion we recognized an anti-neuronal autoantibody directed against GABA(B)R that is associated with autoimmune agrypnia and we showed that our patient purified IgG was able to induce in mice experimental autoimmune agrypnia characterized by a complex neurological syndrome affecting several CNS functions.

Immunolocalization and activation of nuclear factor-κB in the sciatic nerves of rats with experimental autoimmune neuritis

Recent data support an important role played by nuclear factor kappa B (NF-kappaB) in peripheral neuropathies. We investigated expression and activation of NF-kappaB in experimental autoimmune neuritis (EAN) in rat sciatic nerves removed after 7, 14 and 21 days after immunization. Immunoreactivity for the activated form of NF-kappaB was found in the nuclei of T cells and macrophages at days 14 and 21, and also in the nuclei of few Schwann cells and of vascular endothelial cells at all time points, especially during the peak stage. Western blot showed a single band corresponding to 65 kDa in all EAN animals. NF-kappaB DNA-binding activity was revealed by electrophoretic mobility shift assay. Our results support NF-kappaB activation in EAN during the induction stage as well as in the disease remission.

Inhibition of Ras attenuates the course of experimental autoimmune neuritis

EAN induced in Lewis rats by immunization with peripheral bovine myelin was treated by the Ras inhibitor farnesylthiosalicylate (FTS). Treatment from day 0 with FTS (5 mg/kg intraperitoneally twice daily) attenuated peak clinical scores (mean+/-S.E., 2.5+/-0.5 compared to 4.1+/-0.5 in saline treated controls, p=0.018, t-test) but not recovery. Treatment from day 10 with FTS attenuated peak disability (2.5+/-0.6, p=0.032 compared to saline treated controls) and improved recovery (0.84+/-0.42, untreated controls 2.4+/-0.6, p=0.028 by repeated measures ANOVA). Effects were confirmed by rotarod and nerve conduction studies. An inactive analogue, geranylthiosalicylate, had no clinical effect. Inhibition of Ras is of potential use in the treatment of inflammatory neuropathies.

Heterozygous null mutation of myelin P0 protein enhances susceptibility to autoimmune neuritis targeting P0 peptide

Mice with a heterozygous null mutation in myelin protein zero (P0(+/-)) develop late-onset clinical paralysis associated with inflammatory pathology in the peripheral nerves. Although the development of this illness is known to require T cells and macrophages, little is understood regarding the immunological defect in the mice. Here we report that young P0(+/-) mice, free from clinical manifestations, have a defect in central tolerance to P0, and are more prone to induction of experimental autoimmune neuritis (EAN) by sensitization against P0(180-199 )peptide. Notably, we found that the P0 gene is transcribed in the thymus of wild-type and the P0(+/-) mice in an amount proportional to the gene dosage. We then replaced the thymus of wild-type mice with that of the P0-deficient mice and vice versa. Immunization of these mice with P0(180-199 )revealed that a lower thymic P0 transcript would be associated with the higher recall T cell response to P0(180-199), thus accounting for the higher susceptibility of the P0(+/-) mice to P0-induced EAN. These results imply that a heterozygous mutation in an autoantigen could cause defective central tolerance to the autoantigen. As such, autoimmune T cells may play some role in "genetic" diseases caused by a heterozygous gene defect.

[Guillain-Barre syndrome: etiology and pathogenesis]

Guillain-Barre syndrome (GBS) is a reactive, self-limited, monophasic disease triggered by a preceding bacterial or viral infection. GBS has also been linked to underlying systemic diseases, certain malignancies, surgery, pregnancy, trauma severe infection, and tissue transplantation (bone marrow and organs). Although its pathogenesis is unclear, it is likely to be a consequence of an immune mediated process. Therefore, we believe that GBS results from an aberrant immune response that somehow mistakenly attacks the nerve tissue of its host, most probably by recognizing a molecular similar epitope mechanism (molecular mimicry). Immune reactions against these epitopes result in acute inflammatory demyelinating neuropathy or acute axonal forms. GBS has a worldwide distribution with an annual incidence of approximately 1.2-8.6 cases per 100,000 people. Both genders are at similar risk (but there is a slight male predominance). All ages are affected, although the distribution is bimodal. The supporting measures are critically important to provide optimal treatment. Immunomodulation with plasma exchange and intravenous immunoglobulin treatments shorten the disease course. Outcome is generally good, with virtually full recovery in 70-80% of the patients. In this review physiopathological aspects and clinical implications of GBS are fully discussed.

Intranasal administration of recombinant mouse interleukin-12 increases inflammation and demyelination in chronic experimental autoimmune neuritis in Lewis rats

To examine whether interleukin (IL)-12 modulates ongoing chronic experimental autoimmune neuritis (EAN), we evaluated the effects of recombinant mouse IL-12 (rmIL-12) in Lewis rats with chronic EAN, induced by immunization with P0 peptide (180-199) plus complete Freund's adjuvant. Rats were treated intranasally with either 0.1 or 1 microg/rat/day rmIL-12 for 6 days from the onset of clinical chronic EAN, on days 5-10 postimmunization (p.i.). Only high-dose rmIL-12 exacerbated chronic EAN. This clinical effect was associated with higher numbers of inflammatory cells and more severe demyelination in sciatic nerve sections on days 15 and 80 p.i. compared with low-dose rmIL-12-treated rats and phosphate-buffered saline (PBS)-treated control rats. High-dose rmIL-12 increased significantly the lymph node mononuclear cell proliferation in response to P0 peptide 180-199 and IFN-gamma production in the sciatic nerves. These data indicate that intranasally administered IL-12 acts as a proinflammatory cytokine in chronic EAN. Effective inhibition of IL-12 in vivo could be considered for therapeutic use in chronic inflammatory demyelinating polyradiculoneuropathy.

Restimulation of resting autoreactive T cells by Schwann cells in vitro

This study demonstrates that rat Schwann cells can reactivate resting experimental allergic neuritis generating P(2) and P(2) peptide specific CD4(+) T cell lines. T cell proliferation was significantly greater to P(2) than to P(2) peptide (SP-26) or ovalbumin (OA). Four-level analysis of variance showed that T cell proliferation with endogenous or exogenous P(2) was not significantly different for Schwann cells plus cytokine IFN-gamma (P = 0.5071) unlike P(2) peptide or OA specific T cells (P = 0.0056 and 0.0003, respectively). Untreated Schwann cells were more effective inducers than irradiated or fixed Schwann cells. As stimulated CD4(+) P(2) T cells produce IFN-gamma and TNF-alpha, this could exacerbate blood nerve barrier breakdown that has been increasingly implicated in inflammatory demyelinating neuropathies (IDNs). This would permit entry of antibodies and complement, thereby contributing to the demyelination process. Schwann cell induced reactivation of CD4(+) T cells may therefore play a role in IDNs.

Depletion of Vbeta4 TCR does not induce resistance to EAN--further evidence for diversity of TCR usage

In EAN, TCR variable (V) gene usage is still controversial. A dominant usage of a TCR Vbeta4-associated idiotype has been reported. To assess the role of TCR Vbeta4 positive T-cells in susceptibility to induction of EAN, we suppressed the selection of this idiotype by neonatal treatment of Lewis rats with anti-TCR Vbeta4 monoclonal antibody (mAb). Anti-Vbeta4 treatment had no effect on development of clinical disease after immunization with the neuritogenic P2-peptide amino acids (aa) 53-78. Furthermore, lymph node cells from anti-Vbeta4 treated animals isolated after immunization with P2-peptide did not exhibit a reduced proliferative response towards whole P2-protein or P2-peptide. Our results indicate that T-cells utilizing other TCR V chains can functionally replace the neuritogenic cell population, which is dominant in stable T-cell lines.

Resistance and susceptibility to experimental autoimmune neuritis in Sprague-Dawley and Lewis rats correlate with different levels of autoreactive T and B cell responses to myelin antigens

Experimental autoimmune neuritis (EAN) is a CD4+ T cell-mediated, inflammatory demyelinating disease of the peripheral nervous system (PNS) that serves as a model for Guillain-Barré syndrome (GBS) in humans. Various mouse and rat strains show different susceptibilities to EAN that can be induced by immunization with bovine PNS myelin (BPM) + Freund's complete adjuvant (FCA). We examined PNS-induced T and B cell responses and cytokine protein production as well as mRNA expression to study the mechanisms behind susceptibility to EAN in Lewis rats and resistance in Sprague-Dawley (SD) rats. Lewis rats with EAN have elevated PNS myelin-reactive interferon-gamma (IFN-gamma) production, TNF-alpha mRNA expression, and increased B cell responses to PNS myelin antigens, but low PNS myelin-reactive transforming growth factor-beta (TGF-beta) and interleukin (IL)-10 mRNA expression in lymph node mononuclear cells (MNC). In contrast, resistance to EAN in SD rats is associated with reduced BPM and P2 peptide-reactive IFN-gamma production, TNF-alpha mRNA expression, and suppressed B cell responses to PNS myelin antigens as well as up-regulation of TGF-beta and IL-10 mRNA expression. Resistance to EAN is also associated with low-grade inflammation or absence of histological evidence of EAN. These results suggest that differential autoreactive T and B cells responses to PNS myelin antigens are strain specific, and the susceptibility to EAN is related to quantitative rather than qualitative differences in distribution between proinflammatory and anti-inflammatory cytokines.

Thalidomide suppresses T- and B-cell responses to myelin antigen in experimental allergic neuritis

The effects of thalidomide and, for reference, dexamethasone on T- and B-cell functions were assayed in vitro in Lewis rats with experimental allergic neuritis induced by active immunization with bovine peripheral nerve myelin (BPM) and complete Freund's adjuvant. Thalidomide and dexamethasone at the concentration ranges 10(-5)-10(-7) g/ml and 4 x 10(-5)-4 x 10(-9) g/ml, respectively, both inhibited phytohemagglutinin (PHA)- and BPM-induced T-cell proliferation as well as levels of PHA- and BPM-reactive interferon (IFN)-gamma-secreting cells, reflecting the suppression of Th1-like cells. The effect of dexamethasone was most pronounced on PHA-induced T-cell proliferation and IFN-gamma secretion, whereas the effect of thalidomide was most pronounced on BPM-induced T-cell proliferation and IFN-gamma secretion. Thalidomide reduced the B-cell responses to both BPM and Mycobacterium tuberculosis purified protein derivative, but to a lesser extent than dexamethasone. The in vitro design described could be useful to evaluate compounds with putative immunomodulatory activities. The inhibitory effects of thalidomide on autoantigen-induced Th1-cell functions may warrant the use of this substance in T-cell-mediated autoimmune diseases.

Guillain-Barré as an autoimmune disease

Guillain-Barré syndrome (GBS) entails a demyelinating process of the peripheral nervous system. The etiopathogenesis of the syndrome is still a matter of debate although considerable progress has been accomplished in the recent years. Abundant evidence has been put forward so as to support the role of the immune system in initiating and perpetuating the ongoing damage culminating in the emergence of the clinically overt syndrome. As such, data on the involvement of the humoral immune pathways add to the information already presented with regard to cell-mediated mechanisms participating in disruption of peripheral nerve. The following review will focus on the current knowledge of these complex mechanisms and the relative significance of each in the pathogenesis of GBS.

Synergy between antibody and P2-reactive T cells in experimental allergic neuritis

Studies were conducted in experimental allergic neuritis (EAN) to evaluate the possible interaction of cellular and humoral immune mechanisms in the demyelinating process. EAN was induced in Lewis rats by passive transfer of T cells reactive to P2 myelin protein or by active immunisation with whole myelin. Animals were then given systemic antimyelin antibody or control serum and assessed clinically, electrophysiologically and with semiquantitative histological studies. Animals given intraperitoneal (i.p.) P2-reactive T cells and systemic antimyelin antibody developed much more severe disease than those given i.p. T cells alone (P < 0.001). In actively immunised animals, the addition of systemic antimyelin antibody did not significantly alter disease severity. We believe the more severe disease in animals receiving T cells and antimyelin antibody reflects synergy between cellular and humoral immune mechanisms whereby neural antigen-specific T cells breach the blood-nerve barrier, allowing demyelinating antibody access to the endoneurium. In EAN induced by active immunisation with whole myelin it is likely that both B and T cell activation occurs and that the more severe demyelination characteristic of this disease reflects the involvement of both humoral and cellular immunity.

Therapeutic effect of transforming growth factor-beta 2 on actively induced EAN but not adoptive transfer EAN

A possible effect of transforming growth factor type-beta 2 (TGF-beta 2) on autoimmune inflammation of the peripheral nervous system (PNS) was evaluated in experimental autoimmune neuritis (EAN) in Lewis rats, a disease model of the human Guillain-Barré syndrome. First, EAN was actively induced by immunization with a neuritogenic peptide corresponding to amino acids 53-78 of the bovine P2 protein. Intraperitoneal (i.p.) administration of 5 micrograms TGF-beta 2 per day after onset of clinical disease shortened the duration and ameliorated the severity of EAN compared to sham-injected control animals. Inflammatory infiltration and demyelination was significantly reduced in sciatic nerves of TGF-beta-treated animals, although expression of major histocompatibility complex (MHC) class II antigens was not down-regulated. Second, EAN was induced by adoptive transfer (AT) of activated P2-specific T-line cells (AT-EAN). Daily injections of 5 micrograms TGF-beta 2 i.p., beginning on the day of first clinical signs, failed to modify the clinical course of AT-EAN, although the antigen-induced activation of the neuritogenic T-line cells used for induction of disease was found to be partially sensitive to the inhibitory effect of TGF-beta in vitro. The experiments indicate that TGF-beta 2 holds promise as a therapeutic agent to combat autoimmunity in the PNS. They also suggest that the therapeutic efficacy of TGF-beta on rapidly developing disease such as AT-EAN is limited, as with other non-specific immunosuppressive drugs.

[Cell therapy and its risks]

Parenteral administration of fresh cells, frozen cells (snapfrozen cell suspensions) or lyophilized cells (sicca cells), is known as cellular or cell therapy. While the German Health Office (BGA) provisionally banned the use of dried cell preparations in 1987, injection of fresh cells is still allowed. There have been repeated reports of life-threatening, and even fatal, complications of this type of therapy. Since it involves the administration of heterologous biological material, most of the complications that have been observed have been of the allergic/hyperergic type resembling experimental allergic encephalomyelitis (EAE) and experimental allergic neuritis (EAN). When evaluating the risks of this form of alternative-medical treatment, the well-known risks of injection therapy must also be borne in mind. In the case of cell therapy, too, the hoped for effect must be weighed against the risks of the procedure, and our guiding principle must be: nil nocere.

Detection and quantification of antibodies to the extracellular domain of P0 during experimental allergic neuritis

Quantification of the peripheral nerve myelin glycoprotein P0 and antibodies to P0 is difficult due to insolubility of P0 in physiological solutions. We have overcome this problem by using the water-soluble recombinant form of the extracellular domain of P0 (P0-ED) and describe newly developed assays which allow detection and quantitation of P0 and antibodies to P0, in serum and cerebrospinal fluid (CSF). These sensitive and specific assays based on the ELISA technique were used to study humoral immune responses to P0 during experimental autoimmune ("allergic") neuritis (EAN). In order to establish these tests, monoclonal antibodies to different epitopes of rodent and human P0-ED were produced. A two-antibody sandwich-ELISA allowing quantitation of P0 (lower detection limit of 0.5 ng/ml or 30 fmol/ml) and an antibody-capture ELISA (lower detection limit 1 ng specific antibody/ml) to detect antibodies to P0 in serum and CSF were developed. EAN was induced in rats by active immunization with bovine myelin or the neuritogenic protein P2 or by adoptive transfer using P2 specific CD4 positive T cells. Serum and CSF were assayed for the presence of P0-ED and antibodies to P0-ED or P2. Antibodies to P0-ED were detected during active myelin-induced EAN, but not during P2-induced or adoptive transfer EAN. The anti-P0-ED antibodies in the CSF showed a correlation with disease activity. In contrast, in the same model antibodies to P2 persisted long after the disease ceased. No soluble P0-like fragments could be found in serum or CSF during any of the three types of EAN. We conclude that P0 may be a B-cell epitope in EAN. These findings warrant a screen for antibodies to P0-ED in human immune neuropathies.

Effects of ganglioside administration on experimental autoimmune neuritis induced by peripheral nerve myelin or P2-specific T cell lines

We studied the effects of ganglioside administration in two animal models of inflammatory demyelinating polyneuropathy. We administered a mixture of bovine brain gangliosides intraperitoneally to Lewis rats with myelin-induced or T cell line-mediated experimental autoimmune neuritis (EAN). Under the experimental conditions we had chosen, we only detected marginal but not statistically significant effects on disease course and severity, as evidenced by motor function, electrophysiological findings, and morphological signs of inflammation and demyelination. There was no significant induction of antibody production against gangliosides, and we did not detect signs of increased cellular reactivity towards gangliosides. We conclude that the administration of gangliosides modulates EAN at best marginally, and does not induce a cellular or humoral immune reaction.

Cell adhesion molecules of the immunoglobulin supergene family as tissue-specific autoantigens: induction of experimental allergic neuritis (EAN) by P0 protein-specific T cell lines

The P0 glycoprotein is a homophilic cell adhesion molecule of the immunoglobulin supergene family which is responsible for maintaining the structure of compact internodal myelin in the peripheral nervous system (PNS). Utilizing a panel of synthetic P0 peptides two distinct T cell epitopes have been identified that can induce T cell-mediated experimental autoimmune neuritis (EAN) in the Lewis rat. One T cell epitope (amino acid residues 56-71), is located within the extracellular, immunoglobulin-like domain of P0, while the other disease-inducing T cell epitope (residues 180-199) is located within the proteins cytoplasmic carboxyterminal domain. The adoptive transfer of 10(6) CD4+ T line cells specific for either of these peptide antigens induced EAN in syngeneic recipients. However, while the pathogenic response induced by both peptide-specific T cell lines was identical, their epitopes differ markedly in their immunologic properties in vivo. In particular while the response to peptide p180-199 was immunodominant in animals immunized with either purified P0 protein or the native membrane-bound P0 protein in autologous rat peripheral nerve myelin, no response to peptide p56-71 was detected, indicating that this epitope is cryptic. This study provides the first experimental evidence that the immunoglobulin-like domains of members of the immunoglobulin supergene family can function as target autoantigens in T cell-mediated autoimmune disease.

The use of protease inhibitors in experimental allergic neuritis

In experimental allergic neuritis (EAN) break-down of myelin is attributed to macrophages, which among other factors contain and secrete proteases. In vitro studies have shown that cathepsin D, an acidic aspartyl endopeptidase, and plasmin can degrade myelin proteins. In order to elucidate a potential therapeutic effect of protease inhibitors we treated Lewis rats, immunized with bovine peripheral nervous system myelin, with epsilon-amino-caproic acid (EACA) or pepstatin. EACA or pepstatin was administered twice daily by intraperitoneal injection beginning on day 6 postimmunization or from the onset of disease (on day 12) through day 24. Compared to saline-treated controls, animals treated with either of the inhibitors showed delayed development of clinical signs and electrophysiological abnormalities. Maximal severity and the further course of disease, however, were not different in control and treated groups. Immunohistological evaluation of sciatic nerve specimens on day 24 postimmunization showed equal numbers of cells positive for ED1 (macrophages) and cathepsin D in all animal groups. There was also no difference in the spontaneous proteolytic activity of the sciatic nerve homogenates at pH 2.8, 5.0, and 7.4. Incubation of the homogenates with pepstatin, however, significantly reduced proteolytic activity at pH 2.8 and 5.0, while EACA had no effect at any pH tested. These results imply that treatment to limit the infiltration of cathepsin D-positive cells or to reduce the induction or activity of cathepsin D may provide a therapeutic avenue for treating inflammatory demyelination of the peripheral nervous system.

Chronic relapsing experimental allergic neuritis induced by repeated transfer of P2-protein reactive T cell lines

Chronic relapsing experimental allergic neuritis (crEAN) was induced by repeated transfers of P2-protein reactive T lymphocyte lines. Clinically, each intravenous transfer of P2-reactive T cells induced a relapse of the disease with weight loss and flaccid paresis of the hindlimbs followed by recovery. After multiple transfers, recovery from disease was incomplete, leading to increasing neurological deficit during the remissions. The pathology of the lesions during exacerbations was characterized by massive inflammation in the peripheral nervous system, associated with extensive endoneurial oedema, nerve fibre destruction and wallerian degeneration. Selective primary demyelination and remyelination was found in the minority of affected nerve fibres. No onion bulbs were present in chronic lesions. In the central nervous system partial degeneration of the posterior columns reflected the extent of wallerian degeneration in the peripheral nerves and spinal roots. In addition, during stages of active disease some T lymphocytes and upregulation of Ia antigen expression were found in the spinal cord.

Peptide 53-78 of myelin P2 protein is a T cell epitope for the induction of experimental autoimmune neuritis

We have recently described the clinical and pathological features of experimental autoimmune neuritis (EAN) in Lewis rats inoculated with varying doses of a synthetic peptide corresponding to the amino acid residues 53-78 of bovine P2 protein (SP-26). Immunization with this synthetic peptide was able to induce severe clinical and pathological characteristics of EAN. We are now reporting that, SP-26 T cell lines derived from spleen and lymph node cell populations of such immunized rats, upon being triggered by SP-26, can adoptively transfer severe clinical and histological signs of EAN to naive syngeneic recipients. The disease appears 7-8 days postinoculation of the cells and persist 5-10 days. The pathological features were indistinguishable from SP-26-induced active EAN which appears 12-15 days after sensitization. Examination of the surface phenotype of the cells that were used for the passive transfer of EAN by FACS analysis, showed majority of the cells to be CD4+, Ia+ cells.

Response of the axon and barrier endothelium to experimental allergic neuritis induced by autoreactive T cell lines

Experimental allergic neuritis was induced in Lewis rats by inoculation with autoreactive T cell lines sensitized to residue 57-81 of P2 myelin protein. Control rats received cells derived from immunization to complete Freund's adjuvant alone. Endoneurial fluid pressure (EFP) was measured in both sciatic nerves at 0, 3, 5, 7, 9, and 11 days post-inoculation (PI). The temporal evolution of inflammatory disease was studied by correlating EFP with a morphometric analysis of the nerve microenvironment and with electron microscopic observations. Both edema, as evidenced by increased endoneurial extracellular space, and inflammation paralleled the time course of the EFP increase, reaching peak values at 7 days PI and declining to near-normal values after 11 days. Wallerian degeneration was detectable at 7 days and increased 9 days after inoculation. Axonal damage appeared at the height of the inflammatory process, when edema and increased EFP were maximal. Evidence of demyelination was apparent by 7 days and persisted through 11 days. The onset of edema was associated with changes in venular endothelial cells which tended to lose their normal scaphoid appearance and assumed rhomboid configurations reminiscent of high endothelial venules. At that point, the barrier endothelium was visibly disrupted with the loss of tight junctions and separation of adjacent cells. Specific cell-cell interactions took place between endothelial cells and infiltrating leukocytes as they immigrated into the endoneurial compartment. There was evidence of altered perineurial permeability with fibrin deposition and leukocyte infiltration between the layers of the perineurial sheath.

Induction of severe experimental autoimmune neuritis with a synthetic peptide corresponding to the 53-78 amino acid sequence of the myelin P2 protein

We generated a synthetic peptide (SP-26), corresponding to the amino acid residues 53-78 of bovine P2 protein, which induced severe clinical and pathological characteristics of experimental autoimmune neuritis (EAN) in Lewis rats. Lymph node cell populations from SP-26-immunized rats elicited a proliferative response to the peptide and to the P2 protein. After 16 cycles of antigen stimulation with the peptide, the SP-26 T cell line shows a decreased response to P2, but not to SP-26. Fluorescence-activated cell sorter (FACS) analysis of a SP-26 T cell line indicated the majority of cells to be of CD4+ CD8-. This report demonstrates that the synthetic peptide SP-26 can induce severe EAN in Lewis rats in a dose-dependent manner. Furthermore, specific T cell lines reactive to SP-26 can be generated from the lymph nodes of SP-26-immunized rats.

New minimum length requirement for a T cell epitope for experimental allergic neuritis

The bovine P2 protein induces experimental allergic neuritis (EAN) in Lewis rats. Using synthetic peptides representing regions of the P2 protein sequence and P2-specific neuritogenic T cell lines, we have demonstrated that the minimum peptide length requirement for the T cell epitope for EAN is residues 61-70 of the P2 protein having the sequence EISFKLGQEF. Adding a threonine at the NH2 terminus of this peptide reproduces residues 60-70 of the P2 protein sequence and significantly enhances the neuritogenic capability of this peptide.

In vivo monoclonal antibody treatment with Ox19 (anti-rat CD5) causes disease relapse and terminates P2-induced immunospecific tolerance in experimental allergic neuritis

The role of CD5+ lymphocytes in the recovery phase and on immunospecific protection against experimental allergic neuritis (EAN) was examined in Lewis rats by in vivo treatment with Ox19, a mouse anti-rat CD5 monoclonal antibody. Animals pretreated with the peripheral nerve basic protein P2 and thereby rendered resistant to the disease showed clinical signs of EAN after intraperitoneal (i.p.) Ox19 injection given at the same time as the rechallenge with neuritogenic doses of myelin in Freund's complete adjuvant. Non-pretreated rats recovered from signs of EAN developed a clinical relapse after i.p. Ox19 injections. Taken together, these data suggest an important regulatory role of the CD5 receptor in the immune response.

The role of macrophages and eicosanoids in the pathogenesis of experimental allergic neuritis. Serial clinical, electrophysiological, biochemical and morphological observations

Experimental allergic neuritis (EAN) can be prevented or ameliorated by global blockade of macrophages. How these cells damage peripheral nervous tissue in this autoimmune demyelinating polyneuropathy is not fully understood. Since macrophages exert a number of their inflammatory actions by the release of arachidonic acid-derived eicosanoids, we investigated the possible role of these mediators in the pathogenesis of EAN. Lewis rats with myelin-induced EAN were treated before and after onset of clinical signs. Administration of corticosteroids or of the cyclo-oxygenase inhibitors indomethacin and BW755c before the onset of neurological signs suppressed the disease, as judged by clinical assessment, serial electrophysiological testing and histological examination, while initiation of drug treatment on day 13 postimmunization still markedly attenuated the course of EAN. The selective lipoxygenase blocker nafazatrom had only a slight effect. Determination of the production by macrophages ex vivo of eicosanoids corroborated the predicted site of action of the pharmacological compounds applied. We infer that macrophage-derived proinflammatory arachidonic acid metabolites significantly contribute to functional and tissue damage in EAN. Our results may be relevant to future pharmacological treatment of the acute Guillain-Barré syndrome.

The role of macrophages in experimental autoimmune neuritis induced by a P2-specific T-cell line

A P2-specific T-cell line with a helper/inducer phenotype (W3/25+) mediates experimental autoimmune neuritis in the Lewis rat after adoptive transfer to naive recipients. Moderately severe disease was induced in these experiments by the injection of 1 x 10(7) T cells. Motor and mixed afferent nerve conduction, F responses, H reflexes, and lumbar somatosensory evoked potentials were monitored, and morphological alterations were scored semiquantitatively at the end of the experiments. The role of macrophages and macrophage-derived inflammatory mediators in the effector phase of the disease was investigated by administering different inhibitors of macrophage metabolism, including silica, dexamethasone, and a variety of cyclooxygenase and lipoxygenase blockers. Silica and dexamethasone suppressed the clinical, electrophysiological, and morphological manifestations of the disease almost completely, indicating that macrophages are essential for the generation of inflammatory lesions. The inhibitors of arachidonic acid conversion failed to mitigate the severity of the disease. This is in contrast to observations in actively induced experimental autoimmune neuritis in which eicosanoid biosynthesis seems to play a decisive role in the pathogenesis of the disease.

Ciclosporin A prevents P2 T cell line-mediated experimental autoimmune neuritis (AT-EAN) in rat

Adoptive transfer experimental autoimmune neuritis (AT-EAN) produced in Lewis rats by injection of P2-reactive T lymphocyte line cells offers the unique possibility to study the exclusive contribution of cell-mediated immune responses to the pathogenesis of autoimmune disease of the peripheral nervous system (PNS). It further lends itself to the evaluation of novel therapeutic approaches that may bear relevance to the human acute Guillain-Barré syndrome. The effects of the immunosuppressive agent ciclosporin A on the clinical, electrophysiological and morphological expression of AT-EAN were examined. We found that ciclosporin A suppressed development of the disease. In view of the known actions of ciclosporin A on T cells, these results indicate the requirement of activation and clonal proliferation of T lymphocytes to produce myelin damage in autoimmune diseases of the PNS.

Induction of experimental allergic neuritis in the BN rat: P2 protein-specific T cells overcome resistance to actively induced disease

T lymphocyte lines specific for the peripheral nerve myelin protein P2 were selected from the lymph nodes of Brown Norway (BN) rats immunized with bovine P2 protein in complete Freund's adjuvant. These T cells expressed the W3/25+, OX8-phenotype and responded specifically to bovine P2 protein, but not to PPD or bovine basic protein, in T cell proliferation assays. When injected i.v. into syngeneic recipients, BN P2-specific T cell lines induced both clinical and histologic signs of experimental allergic neuritis (EAN), overcoming the resistance of this rat strain to actively induced EAN. Although the histopathology of the disease was indistinguishable from that seen in T cell-mediated EAN in the Lewis rat, disease onset was considerably later, 7 to 8 days after cell transfer, as opposed to 4 days in Lewis. This lag phase between inoculation and disease onset could not be further reduced even by raising the cell dose to 50 X 10(6) cells/host. The fine specificity of the T cell response to P2 differs between Lewis- and BN-derived T cell lines. At least one neuritogenic epitope for each strain was present in the cyanogen bromide-derived peptide CB2 (residues 21-113), as shown by the ability of CB2-specific T cell lines derived from each strain to transfer EAN to the appropriate host strain. However, neuritogenic BN T lines fail to mount a response to the sequence 53-78 (SP4), which encompasses an epitope that is neuritogenic for Lewis rats. These results demonstrate that the resistance of BN rats to actively induced EAN is not due to the lack of appropriate P2-specific autoreactive T cell clones in the normal T repertoire. Furthermore, the results suggest that two distinct epitopes of P2 are responsible for EAN in Lewis and BN rats.

Relation of clinical, serological, morphological, and electrophysiological findings in galactocerebroside-induced experimental allergic neuritis

Rabbits were immunised repeatedly with bovine brain galactocerebroside. Almost all animals developed overt polyradiculoneuropathy. Circulating IgG antibodies to galactocerebroside in the serum and deposits of IgG in the spinal roots were detectable weeks before definite clinical, morphological, and electrophysiological alterations occurred. The levels of IgG antibody titres to galactocerebroside did not correlate with the severity of the clinical disease and of nerve conduction slowing. Remyelination and a virtually complete recovery of nerve dysfunction occurred although circulating antibodies to galactocerebroside were still present.

Conduction failure and nerve conduction slowing in experimental allergic neuritis induced by P2-specific T-cell lines

P2-specific T cells (LiP2/A) mediate experimental allergic neuritis (EAN) in the Lewis rat after adoptive transfer to naive recipients. After a latent period of 4 days, injection of 2 X 10(6) line cells induced fulminant paraplegia and complete conduction failure in the peripheral nerves and roots, resembling acute axonal breakdown. Injection with 10(6) cells caused milder clinical signs, nerve conduction failure, and conduction slowing. Clinical and electrophysiological recovery from adoptively transferred EAN was nearly complete and its time course was inversely correlated to the initial severity of EAN. These findings suggest that EAN induced by the P2-specific T-cell line can lead to a profound and rapidly evolving nerve dysfunction in a dose-dependent fashion.

Experimental allergic neuritis induced in SJL mice by bovine P2

Bovine myelin or bovine myelin-derived P2 protein was injected into 4 inbred mouse strains. SJL mice developed neurological deficit, and histological lesions characteristic of experimental allergic neuritis. BALB/C, CBA and C57.B1/6 mice were relatively resistant to disease induction by this method.

Transfer of experimental allergic neuritis with P2-reactive T-cell lines

Experimental allergic neuritis (EAN) was induced in normal Lewis rats by systemic passive transfer of T-cell lines responding to P2 protein. These cells had predominantly helper phenotype and could induce EAN within 7 days following adoptive transfer. There was no anti-P2 antibody response in the recipients of the P2-reactive cells recovered from donors with high anti-P2 antibody levels. This study provides direct evidence that T cells are important for the induction of EAN. Furthermore, there was no evidence of a pathogenic role for anti-P2 antibody in passive EAN.

A permanent rat T cell line that mediates experimental allergic neuritis in the Lewis rat in vivo

A rat T cell line of the "helper" phenotype (W3/25-positive, OX 8-negative) has been derived from Lewis rats inoculated with P2 protein isolated from bovine PNS myelin. The line LiP2/A is exquisitely specific for P2 protein, exhibiting no reactivity to bovine basic protein or to PPD. In addition to responding strongly to the intact P2 protein, the line cells show some response to a synthetic peptide containing the neuritogenic amino acid sequence of P2 protein (SP-B, residues 66-78). Intravenous inoculation of naive rats with as few as 10(4) activated LiP2/A cells leads to the onset of mild clinical signs of experimental allergic neuritis. Higher doses of cells lead to more severe clinical disease. Histologic examination of clinically ill animals confirmed the disease as EAN. The pathologic lesions were confined to the PNS and spared the central nervous system. The lesions consisted of marked perivascular cuffs and infiltrates of inflammatory cells associated with marked degenerative changes--demyelination and some axonal degeneration.

Experimental allergic neuritis: demyelination induced by P2 alone and non-specific enhancement by cerebroside

Experimental allergic neuritis was induced in male inbred Lewis rats immunized with myelin, P2 alone, P2 mixed with galactocerebroside and P2 mixed with glucocerebroside. Neurological deficit started significantly earlier in myelin-immunized rats than in P2-immunized rats. Although myelin-immunized rats appeared most severely affected, differences between the groups in maximum neurological deficit were not significant. The course of the disease of the P2-galactocerebroside-immunized animals did not differ from that of the P2-glucocerebroside-immunized group. Histologically, cellular infiltration and demyelination were more conspicuous 12 days after immunization in the group immunized with myelin than in the other rats. After 21 days, primary demyelination was prominent in all groups: its frequency and severity were similar in the myelin-immunized and P2-immunized animals. The P2-galactocerebroside-immunized group had significantly more frequent demyelination than the P2-immunized group. Wallerian degeneration was prominent in all groups at this stage. We conclude that P2 alone does induce demyelination and that galactocerebroside added to the immunizing emulsion enhances the response but no more than the non-myelin lipid glucocerebroside.

Experimental neuritis induced by a mixture of neural antigens and influenza vaccines. A possible model for Guillain-Barré syndrome

We describe the development in rats of a possible model for Guillain-Barré syndrome (GBS): experimental neuritis (EN). The clinical symptoms, histopathology and the presence of antibody to nervous tissue are features that EN has in common with both GBS and experimental allergic neuritis (EAN), another GBS model. However, EN may be a more appropriate model than EAN for studying the role of autoimmune reactions in diseases such as GBS, which are triggered by various viruses or antigens, since EN depends on such agents being administered concomitantly with the syngeneic tissue.

The passive transfer of severe allergic neuritis in Lewis rats with lymphoid cells preincubated with P2 protein

The passive transfer of both clinical signs and histologic lesions characteristic of allergic neuritis was successfully performed in Lewis rats using pooled spleen and lymph node cells, or T lymphocytes therefrom, if first preincubated in petri dishes with P2 protein for 72 hr. For passive transfer, cells were taken from donors 8-16 days after sensitization with P2 protein or myelin in Freund's complete adjuvant, and administered via the tail vein; clinical signs appeared 12-13 days later. This study supports the importance of cell-mediated immunity in EAN and the antigenic role of the P2 protein.

Induction of allergic neuritis in rhesus monkeys

Experimental allergic neuritis (EAN) was induced in rhesus monkey (Macaca mulatta) following sensitization with rabbit nerve (PNS) myelin in complete Freund's adjuvant (CFA) or with bovine P2 protein complexed with phosphatidyl serine (P2-lipid) in CFA. The response of monkeys receiving PNS myelin in CFA differed from the previous studies where monkeys developed clinical signs of fatal EAN within 15-20 days following sensitization. The monkeys in this study (6) showed a much longer delay (40-114 days) before the appearance of severe clinical signs, and 4 of the 6 animals survived without further attack (1 year). Monkeys (4) injected with P2-lipid (2:1 ratio; w/w) developed severe clinical signs of EAN which was fetal in 3 cases. Peripheral lymphocytes from monkeys sensitized to the P2-lipid showed a much stronger mitogeneic response to P2 protein than those from the PNS myelin-sensitized monkeys. on quantitation of the circulating anti-P2 antibodies, the P2-sensitized monkeys generally had much titers than those sensitized with PNS myelin.

Late onset of Guillain-Barré syndrome

The Guillain-Barré syndrome (GBS) usually occurs within one month of the precipitating cause. It is the purpose of this paper to show that typical cases may, however, appear weeks to months later. We have reviewed the collected data on these cases and suggest that they provide evidence which is in favour of a humoral, rather than a cell-mediated, aetiology for GBS.

Results of endoneural injection of Guillain-Barré serum in Lewis rats

We previously studied the neurophysiologic effect of endoneural injection of serum from patients with acute inflammatory-demyelinating polyradiculoneuropathy into the sciatic nerve of Sprague-Dawley rats and did not observe a statistically significant difference between the results with that serum and control serum at 1 week. Because of potential strain susceptibility to acute inflammatory-demyelinating polyradiculoneuropathy serum after endoneural injection, the syngeneic Lewis rat--which is more susceptible than other strains of rats to experimental allergic neuritis (considered to be an experimental model of acute inflammatory-demyelinating polyradiculoneuropathy)--was studied. We used sera from five severely affected patients and also used a more sensitive (compared with our earlier studies) electrophysiologic approach that included in vivo monophasic compound action potential recordings and paired pulses. No statistically significant differences in conduction velocity, amplitude, indices of dispersion, or time-integral percentage were found between disease and control sera at 1 week. We conclude that the human acute inflammatory-demyelinating polyradiculoneuropathy serum tested did not contain measurable demyelinating activity for rat nerve in excess of that of control serum.