Sural nerve biopsies in Guillain-Barre syndrome: axonal degeneration and macrophage-associated demyelination and absence of cytomegalovirus genome

Animal models of immune-mediated demyelinating polyneuropathies

Immune-mediated demyelinating polyneuropathies (IMDPs) are rare disorders in which dysregulated adaptive immune responses cause peripheral nerve demyelinating inflammation and axonal injury in susceptible individuals. Despite significant advances in understanding IMDP pathogenesis guided by patient data and representative mammalian models, specific therapies are lacking. Significant knowledge gaps in IMDP pathogenesis still exist, e.g. precise antigen(s) and mechanisms that initially trigger immune system activation and identification of large population disease susceptibility factors. The initial directional cues for antigen-specific effector or autoreactive leukocyte trafficking into peripheral nerves are also unknown. An overview of current animal models, with emphasis on the experimental autoimmune neuritis and spontaneous autoimmune peripheral polyneuropathy models, is provided. Insights on the initial directional cues for peripheral nerve tissue specific autoimmunity using a novel Major Histocompatibility Complex class II conditional knockout mouse strain are also discussed, suggesting an essential research tool to study cell- and time-dependent adaptive immunity in autoimmune diseases.

Development of a major histocompatibility complex class II conditional knockout mouse to study cell-specific and time-dependent adaptive immune responses in peripheral nerves

INTRODUCTION/AIMS

The precise relationship between molecular mimicry and tissue-specific autoimmunity is unknown. Major histocompatibility complex (MHC) class II antigen presenting cell-CD4+ T-cell receptor complex interactions are necessary for adaptive immunity. This study aimed to determine the role of endoneurial endothelial cell MHC class II in autoimmune polyneuropathy.

METHODS

Cryopreserved Guillain-Barré syndrome (GBS) patient sural nerve biopsies and sciatic nerves from the severe murine experimental autoimmune neuritis (sm-EAN) GBS model were studied. Cultured conditional ready MHC Class II antigen A-alpha chain (H2-Aa) embryonic stem cells were used to generate H2-Aaflox/+ C57BL/6 mice. Mice were backcrossed and intercrossed to the SJL background to generate H2-Aaflox/flox SJL mice, bred with hemizygous Tamoxifen-inducible von Willebrand factor Cre recombinase (vWF-iCre/+) SJL mice to generate H2-Aaflox/flox; vWF-iCre/+ mice to study microvascular endothelial cell adaptive immune responses. Sm-EAN was induced in Tamoxifen-treated H2-Aaflox/flox; vWF-iCre/+, H2-Aaflox/flox; +/+, H2-Aa+/+; vWF-iCre/+ and untreated H2-Aaflox/flox; vWF-iCre/+ adult female SJL mice. Neurobehavioral, electrophysiological and histopathological assessments were performed at predefined time points.

RESULTS

Endoneurial endothelial cell MHC class II expression was observed in normal and inflamed human and mouse peripheral nerves. Tamoxifen-treated H2-Aaflox/flox; vWF-iCre/+ mice were resistant to sm-EAN despite extensive MHC class II expression in lymphoid and non-lymphoid tissues.

DISCUSSION

A conditional MHC class II knockout mouse to study cell- and time-dependent adaptive immune responses in vivo was developed. Initial studies show microvascular endothelial cell MHC class II expression is necessary for peripheral nerve specific autoimmunity, as advocated by human in vitro adaptive immunity and ex vivo transplant rejection studies.

Pathology explains various mechanisms of auto-immune inflammatory peripheral neuropathies

Autoimmune neuropathies are a heterogeneous group of rare and disabling diseases in which the immune system is thought to target antigens in the peripheral nervous system: they usually respond to immune therapies. Guillain-Barré syndrome is divided into several subtypes including "acute inflammatory demyelinating polyradiculoneuropathy," "acute motor axonal neuropathy," "acute motor sensory neuropathy," and other variants. Chronic forms such as chronic inflammatory demyelinating polyneuropathy (CIDP) and other subtypes and polyneuropathy associated with IgM monoclonal gammopathy; autoimmune nodopathies also belong to this group of auto-immune neuropathies. It has been shown that immunoglobulin G from the serum of about 30% of CIDP patients immunolabels nodes of Ranvier or paranodes of myelinated axons. Whatever the cause of myelin damage of the peripheral nervous system, the initial attack on myelin by a dysimmune process may begin either at the internodal area or in the paranodal and nodal regions. The term "nodoparanodopathy" was first applied to some "axonal Guillain-Barré syndrome" subtypes, then extended to cases classified as CIDP bearing IgG4 antibodies against paranodal axoglial proteins. In these cases, paranodal dissection develops in the absence of macrophage-induced demyelination. In contrast, the mechanisms of demyelination of other dysimmune neuropathies induced by macrophages are unexplained, as no antibodies have been identified in such cases. The main objective of this presentation is to show that the pathology illustrates, confirms, and may explain such mechanisms.

Development of a major histocompatibility complex class II conditional knockout mouse to study cell-specific and time-dependent adaptive immune responses in peripheral nerves

Introduction

Major histocompatibility complex (MHC) class II professional antigen presenting cell-naïve CD4+ T cell interactions via the T-cell receptor complex are necessary for adaptive immunity. MHC class II upregulation in multiple cell types occurs in human autoimmune polyneuropathy patient biopsies, necessitating studies to ascertain cellular signaling pathways required for tissue-specific autoimmunity.

Methods

Cryopreserved Guillain-Barré syndrome (GBS) patient sural nerve biopsies and sciatic nerves from the severe murine experimental autoimmune neuritis (sm-EAN) GBS model were studied. Cultured conditional ready MHC Class II antigen A-alpha chain (H2-Aa) embryonic stem cells were used to generate H2-Aa flox/+ C57BL/6 mice. Mice were backcrossed and intercrossed to the SJL background to generate H2-Aa flox/flox SJL mice, bred with hemizygous Tamoxifen-inducible von Willebrand factor Cre recombinase (vWF-iCre/+) SJL mice to generate H2-Aa flox/flox ; vWF-iCre/+ to study microvascular endothelial cell adaptive immune responses. Sm-EAN was induced in adult female SJL Tamoxifen-treated H2-Aa flox/flox ; vWF-iCre/+ mice and H2-Aa flox/flox ; +/+ littermate controls. Neurobehavioral, electrophysiological and histopathological assessments were performed at predefined time points.

Results

Endoneurial endothelial cell MHC class II expression was observed in normal and inflamed human and mouse peripheral nerves. Adult female Tamoxifen-treated H2-Aa flox/flox ; vWF-iCre/+ did not develop sm-EAN despite extensive MHC class II expression in lymphoid and non-lymphoid tissues.

Discussion

A conditional MHC class II knockout mouse to study cell- and time-dependent adaptive immune responses in vivo is developed. Initial studies show microvascular endothelial cell MHC class II expression is necessary for peripheral nerve specific autoimmunity, as advocated by human in vitro adaptive immunity and ex vivo transplant rejection studies.

Origin and Differentiation of Nerve-Associated Macrophages

The mature peripheral nervous system is a steady network structure yet shows remarkable regenerative properties. The interaction of peripheral nerves with myeloid cells has largely been investigated in the context of damage, following trauma or infection. Recently, specific macrophages dedicated to homeostatic peripheral nerves have come into focus. These macrophages are defined by tissue and nerve type, are seeded in part prenatally, and self-maintain via proliferation. Thus, they are markedly distinct from monocyte-derived macrophages invading after local disturbance of nerve integrity. The phenotypic and transcriptional adaptation of macrophages to the discrete nervous niche may exert axon guidance and nerve regeneration and thus contribute to the stability of the peripheral nervous network. Deciphering these conserved macrophage-nerve interactions offers new translational perspectives for chronic diseases of the peripheral nervous system, such as diabetic neuropathy and pain.

Biology of the human blood-nerve barrier in health and disease

A highly regulated endoneurial microenvironment is required for normal axonal function in peripheral nerves and nerve roots, which structurally consist of an outer collagenous epineurium, inner perineurium consisting of multiple concentric layers of specialized epithelioid myofibroblasts that surround the innermost endoneurium, which consists of myelinated and unmyelinated axons embedded in a looser mesh of collagen fibers. Endoneurial homeostasis is achieved by tight junction-forming endoneurial microvessels that control ion, solute, water, nutrient, macromolecule and leukocyte influx and efflux between the bloodstream and endoneurium, and the innermost layers of the perineurium that control interstitial fluid component flux between the freely permeable epineurium and endoneurium. Strictly speaking, endoneurial microvascular endothelium should be considered the blood-nerve barrier (BNB) due to direct communication with circulating blood. The mammalian BNB is considered the second most restrictive vascular system after the blood-brain barrier (BBB) based on classic in situ permeability studies. Structural alterations in endoneurial microvessels or interactions with hematogenous leukocytes have been described in several human peripheral neuropathies; however major advances in BNB biology in health and disease have been limited over the past 50 years. Guided by transcriptome and proteome studies of normal and pathologic human peripheral nerves, purified primary and immortalized human endoneurial endothelial cells that form the BNB and leukocytes from patients with well-characterized peripheral neuropathies, validated by in situ or ex vivo protein expression studies, data are emerging on the molecular and functional characteristics of the human BNB in health and in specific peripheral neuropathies, as well as chronic neuropathic pain. These early advancements have the potential to not only increase our understanding of how the BNB works and adapts or fails to adapt to varying insult, but provide insights relevant to pathogenic leukocyte trafficking, with translational potential and specific therapeutic application for chronic peripheral neuropathies and neuropathic pain.

Guillain-Barré syndrome, transverse myelitis and infectious diseases

Guillain-Barré syndrome (GBS) and transverse myelitis (TM) both represent immunologically mediated polyneuropathies of major clinical importance. Both are thought to have a genetic predisposition, but as of yet no specific genetic risk loci have been clearly defined. Both are considered autoimmune, but again the etiologies remain enigmatic. Both may be induced via molecular mimicry, particularly from infectious agents and vaccines, but clearly host factor and co-founding host responses will modulate disease susceptibility and natural history. GBS is an acute inflammatory immune-mediated polyradiculoneuropathy characterized by tingling, progressive weakness, autonomic dysfunction, and pain. Immune injury specifically takes place at the myelin sheath and related Schwann-cell components in acute inflammatory demyelinating polyneuropathy, whereas in acute motor axonal neuropathy membranes on the nerve axon (the axolemma) are the primary target for immune-related injury. Outbreaks of GBS have been reported, most frequently related to Campylobacter jejuni infection, however, other agents such as Zika Virus have been strongly associated. Patients with GBS related to infections frequently produce antibodies against human peripheral nerve gangliosides. In contrast, TM is an inflammatory disorder characterized by acute or subacute motor, sensory, and autonomic spinal cord dysfunction. There is interruption of ascending and descending neuroanatomical pathways on the transverse plane of the spinal cord similar to GBS. It has been suggested to be triggered by infectious agents and molecular mimicry. In this review, we will focus on the putative role of infectious agents as triggering factors of GBS and TM.

Inflammatory neuropathies: pathology, molecular markers and targets for specific therapeutic intervention

Inflammatory neuropathies encompass groups of heterogeneous disorders characterized by pathogenic immune-mediated hematogenous leukocyte infiltration of peripheral nerves, nerve roots or both, with resultant demyelination or axonal degeneration or both. Inflammatory neuropathies may be divided into three major disease categories: Guillain-Barré syndrome (particularly the acute inflammatory demyelinating polyradiculoneuropathy variant), chronic inflammatory demyelinating polyradiculoneuropathy and nonsystemic vasculitic neuropathy (or peripheral nerve vasculitis). Despite major advances in molecular biology, pathology and genetics, the pathogenesis of these disorders remains elusive. There is insufficient knowledge on the mechanisms of hematogenous leukocyte trafficking into the peripheral nervous system to guide the development of specific molecular therapies for immune-mediated inflammatory neuropathies compared to disorders such as psoriasis, inflammatory bowel disease, rheumatoid arthritis or multiple sclerosis. The recent isolation and characterization of human endoneurial endothelial cells that form the blood-nerve barrier provides an opportunity to elucidate leukocyte-endothelial cell interactions critical to the pathogenesis of inflammatory neuropathies at the interface between the systemic circulation and peripheral nerve endoneurium. This review discusses our current knowledge of the classic pathological features of inflammatory neuropathies, attempts at molecular classification and genetic determinants, the utilization of in vitro and in vivo animal models to determine pathogenic mechanisms at the interface between the systemic circulation and the peripheral nervous system relevant to these disorders and prospects for future potential molecular pathology biomarkers and targets for specific therapeutic intervention.

Role of cytokines and Toll-like receptors in the immunopathogenesis of Guillain-Barré syndrome

Guillain-Barré syndrome (GBS) is an autoimmune disease of the peripheral nervous system, mostly triggered by an aberrant immune response to an infectious pathogen. Although several infections have been implicated in the pathogenesis of GBS, not all such infected individuals develop this disease. Moreover, infection with a single agent might also lead to different subtypes of GBS emphasizing the role of host factors in the development of GBS. The host factors regulate a broad range of inflammatory processes that are involved in the pathogenesis of autoimmune diseases including GBS. Evidences suggest that systemically and locally released cytokines and their involvement in immune-mediated demyelination and axonal damage of peripheral nerves are important in the pathogenesis of GBS. Toll-like receptors (TLRs) link innate and adaptive immunity through transcription of several proinflammatory cytokines. TLR genes may increase susceptibility to microbial infections; an attenuated immune response towards antigen and downregulation of cytokines occurs due to mutation in the gene. Herein, we discuss the crucial role of host factors such as cytokines and TLRs that activate the immune response and are involved in the pathogenesis of the disease.

Antibodies to gliomedin cause peripheral demyelinating neuropathy and the dismantling of the nodes of Ranvier

Guillain-Barré syndrome (GBS) and chronic inflammatory demyelinating polyneuropathy (CIDP) are conditions that affect peripheral nerves. The mechanisms that underlie demyelination in these neuropathies are unknown. Recently, we demonstrated that the node of Ranvier is the primary site of the immune attack in patients with GBS and CIDP. In particular, GBS patients have antibodies against gliomedin and neurofascin, two adhesion molecules that play a crucial role in the formation of nodes of Ranvier. We demonstrate that immunity toward gliomedin, but not neurofascin, induced a progressive neuropathy in Lewis rats characterized by conduction defects and demyelination in spinal nerves. The clinical symptoms closely followed the titers of anti-gliomedin IgG and were associated with an important deposition of IgG at nodes. Furthermore, passive transfer of antigliomedin IgG induced a severe demyelinating condition and conduction loss. In both active and passive models, the immune attack at nodes occasioned the loss of the nodal clusters for gliomedin, neurofascin-186, and voltage-gated sodium channels. These results indicate that primary immune reaction against gliomedin, a peripheral nervous system adhesion molecule, can be responsible for the initiation or progression of the demyelinating form of GBS. Furthermore, these autoantibodies affect saltatory propagation by dismantling nodal organization and sodium channel clusters. Antibodies reactive against nodal adhesion molecules thus likely participate in the pathologic process of GBS and CIDP.

From transcriptome analysis to therapeutic anti-CD40L treatment in the SOD1 model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of motor neurons. Using unbiased transcript profiling in an ALS mouse model, we identified a role for the co-stimulatory pathway, a key regulator of immune responses. Furthermore, we observed that this pathway is upregulated in the blood of 56% of human patients with ALS. A therapy using a monoclonal antibody to CD40L was developed that slows weight loss, delays paralysis and extends survival in an ALS mouse model. This work demonstrates that unbiased transcript profiling can identify cellular pathways responsive to therapeutic intervention in a preclinical model of human disease.

Pain hypersensitivity in rats with experimental autoimmune neuritis, an animal model of human inflammatory demyelinating neuropathy

Experimental autoimmune neuritis (EAN) is a T cell mediated autoimmune disease of the peripheral nervous system that serves as an animal model of the acute inflammatory demyelinating polyradiculoneuropathy in Guillain-Barre syndrome (GBS). Although pain is a common symptom of GBS occurring in 55-85% of cases, it is often overlooked and the underlying mechanisms are poorly understood. Here we examined whether animals with EAN exhibit signs of neuropathic pain including hyperalgesia and allodynia, and assessed their peripheral nerve autoimmune inflammation. We immunized Lewis rats with peripheral myelin P2 peptide (amino acids 57-81) emulsified with complete Freund's adjuvant, or with adjuvant only as control. P2-immunized rats developed mild to modest monophasic EAN with disease onset at day 8, peak at days 15-17, and full recovery by day 28 following immunization. Rats with EAN showed a significant decrease in withdrawal latency to thermal stimuli and withdrawal threshold to mechanical stimuli, in both hindpaws and forepaws, during the course of the disease. We observed a significant infiltration of T cells bearing alphabeta receptors, and a significant increase in antigen-presenting cells expressing MHC class II as well as macrophages, in EAN-affected rats. Our results demonstrate that animals with active EAN develop significant thermal hyperalgesia and mechanical allodynia, accompanied by pronounced autoimmune inflammation in peripheral nerves. These findings suggest that EAN is a useful model for the pain seen in many GBS patients, and may facilitate study of neuroimmune mechanisms underlying pain in autoimmune neuropathies.

Role of Nitric Oxide as Mediator of Nerve Injury in Inflammatory Neuropathies

Different lines of evidence suggest that nitric oxide (NO) plays a key role in the pathogenesis of inflammatory neuropathies; however, it is still unclear which structures in the peripheral nerve are the primary targets of NO-mediated nerve injury. To address this issue, we determined the expression of NO metabolites in sural nerve biopsies and in cerebrospinal fluid from patients with inflammatory neuropathies and studied the pathologic effects of NO in an in vitro model of myelinated Schwann cell-neuron cocultures. In cerebrospinal fluid samples, nitrite levels remained unaltered; however, nitrotyrosine, a marker for peroxynitrite formation, could be identified in nerve biopsies from patients with inflammatory neuropathies. In an in vitro model of Schwann cell neuron cocultures, high concentrations of NO induced robust demyelination, which was the result of NO-mediated axonal injury, whereas Schwann cell viability remained unaffected. These findings suggest that in contrast to Schwann cells, sensory neurons are the primary target of NO-mediated cytotoxicity and the loss of myelin is the result of selective damage to axons rather than a direct harmful effect to Schwann cells. Our findings imply that NO contributes to the pathologic changes seen in the inflamed peripheral nervous system, which is characterized by the features of axonal injury and subsequent myelin degradation, previously described as Wallerian-like degeneration.

Infections à Campylobacter jejuni et à cytomégalovirus (CMV) associées au syndrome de Guillain-Barré (SGB)

Guillain-Barre syndrome (GBS) is a rare disease triggered by postinfectious mechanisms. The disease concerns all ages, and is widely distributed around the world. The principal risks are respiratory failure, especially during the initial phase of the disease, and persisting deficit at long term. Among the infectious known agents, Campylobacter jejuni and CMV represent more than 40% of GBS causes. The clinical presentation, and the long-term prognosis of GBS related to these two etiologies are different. The physiopathological mechanisms of the nervous attack are probably also different. There is no proof, at this time, that anti-infectious treatment can improve the prognosis. The treatment is based on the early use of immunomodulatory treatments like intravenous immunoglobulins or plasma exchanges.

Compound sensory action potential in normal and pathological human nerves

The compound sensory nerve action potential (SNAP) is the result of phase summation and cancellation of single fiber potentials (SFAPs) with amplitudes that depend on fiber diameter, and the amplitude and shape of the SNAP is determined by the distribution of fiber diameters. Conduction velocities at different conduction distances are determined by summation of SFAPs of varying fiber diameters, and differ in this respect, also, from the compound muscle action potential (CMAP) for which conduction velocities are determined by the very fastest fibers in the nerve. The effect and extent of temporal dispersion over increasing conduction distance is greater for the SNAP than CMAP, and demonstration of conduction block is therefore difficult. In addition, the effect of temporal dispersion on amplitude and shape is strongly dependent on the number of conducting fibers and their distribution, and, with fiber loss or increased conduction velocity variability changes of the SNAP may be smaller than expected from normal nerve. The biophysical characteristics of sensory and motor fibers differ, and this may to some extent determine divergent pathophysiological changes in sensory and motor fibers in different polyneuropathies. In this review, different factors that characterize sensory fibers and set the SNAP apart from the CMAP are discussed to emphasize the supplementary and complementary information that can be obtained from sensory conduction studies. Sensory conduction studies require particular effort and attention to theory and practical detail that may be time consuming.

Serum tumour necrosis factor-alpha and soluble tumour necrosis factor receptors levels in patients with Guillain-Barre syndrome

OBJECTIVES

To estimate the serum concentrations of Tumour Necrosis Factor alpha (TNF-alpha) and soluble TNF receptors (s TNF-RI and TNF-RII) in patients with Guillain-Barre syndrome (GBS), before and after treatment.

MATERIAL AND METHODS

The serum TNF-alpha and the soluble TNF receptors concentrations were measured by a sandwich enzyme-linked immunosorbent assay (ELISA) in 47 patients with GBS before and after the treatment - IVI therapy (n=26); Plasma Exchange (n=21).

RESULTS

At the time of admission, the serum TNF-alpha concentrations were elevated (32.5-182.5 pg/ml) in 41/47 GBS patients (87.2%). Following the treatment (IVIG or PE), there was a significant decrease in the serum TNF-alpha concentrations (8.5-58.5 pg/ml) in these 41 GBS patients. The soluble TNF receptors, particularly sTNF-RII concentrations were significantly increased in GBS patients treated by IVIG therapy.

CONCLUSIONS

The results of this indicated that (a) Elevated serum concentrations of TNF-alpha showed a positive correlation with the disease severity in patients with GBS. (b) The decrease in the serum TNF-alpha and increase in the serum soluble TNF receptors, particularly sTNF-RII showed a positive correlation with the neurological recovery in GBB patients following treatment.

Serum tumor necrosis factor-alpha in Guillain-Barré syndrome and its relation to plasma exchange

BACKGROUND

To correlate the serum tumor necrosis factor-alpha (TNFalpha) concentrations before, during and following plasma exchange in patients with Guillain-Barré syndrome (GBS). In this prospective study, 21 GBS patients were selected. Patients in clinical stages III to V were subjected to plasma exchange. The control group included equal numbers of age-matched patients with other neurological diseases and healthy voluntary blood donors. A sandwich ELISA method was applied to estimate serum TNFalpha concentrations in test and control groups.

REVIEW SUMMARY

Twelve GBS patients had elevated serum TNFalpha levels that ranged between 74 and 182 pg/mL. All 12 GBS patients showed a steady decrease in the TNFalpha concentration following plasma exchange and also showed a positive correlation with neurological recovery.

CONCLUSIONS

We conclude that serum TNFalpha concentrations are elevated in 57.1% of GBS patients and TNFalpha level decreases following plasma exchange.

Guillain-Barré syndrome serum and anti-Campylobacter antibody do not exacerbate experimental autoimmune neuritis

To investigate whether antibodies are pathogenic in Guillain-Barré syndrome (GBS), we injected pre-treatment serum from 11 GBS patients intraperitoneally into rats in which the blood-nerve barrier had been opened by induction of mild adoptive transfer experimental autoimmune neuritis. There was no significant clinical, neurophysiological or pathological difference between rats receiving GBS serum compared with those receiving control serum, except that GBS serum caused minor excess weight loss. Murine monoclonal antibody to Campylobacter jejuni and gangliosides also did not exacerbate disease. This experiment failed to show antibody-mediated disease exacerbation and so does not support an antibody-mediated mechanism in GBS.

The role of macrophages in immune-mediated damage to the peripheral nervous system

Macrophage-mediated segmental demyelination is the pathological hallmark of autoimmune demyelinating polyneuropathies, including the demyelinating form of Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy. Macrophages serve a multitude of functions throughout the entire pathogenetic process of autoimmune neuropathy. Resident endoneurial macrophages are likely to act as local antigen-presenting cells by their capability to express major histocompatibility complex antigens and costimulatory B7-molecules, and may thus be critical in triggering the autoimmune process. Hematogenous infiltrating macrophages then find their way into the peripheral nerve together with T-cells by the concerted action of adhesion molecules, matrix metalloproteases and chemotactic signals. Within the nerve, macrophages regulate inflammation by secreting several pro-inflammatory cytokines including IL-1, IL-6, IL-12 and TNF-alpha. Autoantibodies are likely to guide macrophages towards their myelin or primarily axonal targets, which then attack in a complement-dependent and receptor-mediated manner. In addition, non-specific tissue damage occurs through the secretion of toxic mediators and cytokines. Later, macrophages contribute to the termination of inflammation by promoting T-cell apoptosis and expressing anti-inflammatory cytokines including TGF-beta1 and IL-10. During recovery, they are tightly involved in allowing Schwann cell proliferation, remyelination and axonal regeneration to proceed. Macrophages, thus, play dual roles in autoimmune neuropathy, being detrimental in attacking nervous tissue but also salutary, when aiding in the termination of the inflammatory process and the promotion of recovery.

Prospective study of the usefulness of sural nerve biopsy

OBJECTIVE

This study aimed to determine the usefulness of sural nerve biopsy in neurological practice.

METHODS

The first prospective study of sural nerve biopsy in 50 consecutive patients was undertaken. The investigating neurologist declared the prebiopsy diagnosis and management plan and after 3 months an independent neurologist evaluated the contribution of the biopsy to diagnosis and management. An independent audit officer sought information from the patient about the adverse effects and value of the biopsy after 6 weeks and 6 months.

RESULTS

In seven cases the nerve biopsy changed the diagnosis, in 35 cases the biopsy confirmed the suspected diagnosis, and in eight cases the biopsy was non-contributory. The biopsy either changed or was helpful in guiding patient management in 60%, especially those with demyelinating neuropathy and multiple mononeuropathy. Seven patients reported having had infection and 10 reported increased pain at the biopsy site 6 months later.

CONCLUSION

In a consecutive series of 50 cases, sural nerve biopsy altered the diagnosis in 14%, affected management in 60%, and caused persistent increased pain at the biopsy site in 33%.

Protective effect of Rolipram in experimental autoimmune neuritis: protection is associated with down-regulation of IFN-gamma and inflammatory chemokines as well as up-regulation of IL-4 in peripheral nervous system

Rolipram, a phosphodiesterase type 4 inhibitor, is reported to have anti-inflammatory effects. It can markedly downregulate antigen-driven T cell proliferation and suppress TNF-(alpha and TNF-beta production in vitro and in vivo, which have led to its use in the treatment of a number of autoimmune disorders including experimental autoimmune encephalomyelitis (EAE) and experimental autoimmune neuritis (EAN). EAN is a CD4+ T cell-mediated demyelinating autoimmune disease of peripheral nervous system (PNS) that represents an animal model for the study of the immunopathogenesis and immunotherapy of Guillain-Barré syndrome (GBS) in human. In the previous study, we reported that suppression of EAN by Rolipram was associated with down-regulated myelin antigen-induced T cell responses as well as downregulated IFN-gamma and TNF-alpha production. Here we report that EAN induced in Lewis rats by inoculation with the PNS P2 protein peptide 57-81 and Freund's complete adjuvant (FCA), was strongly suppressed by Rolipram administered twice daily intraperitoneally from day 9 post immunization (p.i.), i.e. after onset of clinical EAN to day 18 p.i. This clinical effect was associated with dose-dependent down-regulated production of IFN-gamma and the chemokines macrophage inflammatory protein-1 alpha (MIP-1 alpha, MIP-2 and monocyte chemotactic protein-1(MCP-1) as well as up-regulated IL-4 production in sciatic nerve sections from Rolipram-treated EAN rats at maximum of clinical EAN, i.e. on day 14 p.i.. These findings suggest that Rolipram may be useful in certain T cell-dependent autoimmune diseases and inflammatory neuropathies. These observations call for further studies on the potential role of Rolipram in the treatment of autoimmune diseases.

Inexcitability of nerves in a fulminant case of Guillain-Barré syndrome

A 45-year-old woman presented with a recent sensorimotor deficiency in all 4 limbs, and the next day she was totally paralyzed. A slight motor improvement began on day 27. The cerebrospinal fluid had normal cellularity, but the protein varied from 90 mg/dL on the first day to 800 mg/dL on day 15, and then 290 mg/dL on day 33. Electrophysiologic studies performed on days 15 and 23 revealed a universal peripheral nerve inexcitability. A superficial peroneal nerve biopsy was performed on day 23. Nine fascicles were examined on semi-thin sections and myelinated fiber damage varied greatly from one fascicle to another. At ultrastructural examination, certain axons were severely damaged, but the others were quite well preserved and were naked or wrapped in a myelin sheath presenting a multivesicular degeneration. A few fibers had a better-preserved myelin sheath that was sometimes dissociated by elongated processes from an invading histiocyte. Six cases of fulminant Guillain-Barré syndrome with inexcitability of nerves and ultrastructural examination of nerve fragments have been reported. Electrophysiologic study is often ambiguous and cannot determine the precise origin of such an axonal degeneration. Therefore, ultrastructural analysis of a nerve biopsy is mandatory in this setting.

Guillain-Barré syndrome occurring in two women after ketoacidosic comatose state disclosing an insulin-dependent diabetes mellitus

We report two women who presented with a Guillain-Barré syndrome just after a ketoacidosic comatose state disclosing an insulin-dependent diabetes mellitus. One had characteristic clinical signs and the other had major motor involvement. At neurophysiologic investigations, one had typical demyelinating neuropathy whereas the second had mainly axonal degeneration. At ultrastructural examination of a peripheral nerve biopsy, features of macrophage-associated demyelination were present in both nerve specimens, thus confirming the diagnosis of acute inflammatory demyelinating polyneuropathy, i.e., Guillain-Barré syndrome. Prominent axonal involvement was also present in the motor nerves of the second patient. Insulin therapy had to be permanently continued and these two cases are quite different from the transient diabetes sometimes observed in certain cases of Guillain-Barré syndrome. Both the latter and insulin-dependent diabetes mellitus probably have auto-immune mechanisms. It is likely that in our two patients both auto-immune diseases were triggered by a common event. Such cases of Guillain-Barré syndrome have to be distinguished from other acute diabetic neuropathies.

Phenotypic and functional properties of gamma delta T cells from patients with Guillain Barré syndrome

In this study we have examined the phenotypic and functional properties of circulating gamma delta T cells in patients with Guillain Barre syndrome (GBS), in normal healthy controls, and in patients with active multiple sclerosis (MS). Cells expressing the Vdelta2 T cell receptor showed elevated expression of the C-lectin receptor NKRP1A in both GBS and MS, suggestive of an activated state. However, in patients with GBS these cells failed to respond to pyrenil-pyrophosphate derivatives and Vdelta2 + T cell clones derived from these patients released lower levels of IFNgamma than Vdelta2 + clones derived from controls and MS patients. In contrast, in patients with GBS the Vdelta1 + subset was expanded, showed elevated expression of NKRPIA and Vdelta1 + clones derived from these patients secreted high levels of IL-4. Our findings of expanded NKRP-1A +, IL-4-producing Vdelta1 T cells in the GBS patients suggests the possibility that these cells are activated by the recognition of non-protein antigens in an MHC-unrestricted manner and contribute to the humoral response to glycolipids that is a hallmark of this disease.

Pathogenesis of Guillain-Barré syndrome

Recent neurophysiological and pathological studies have led to a reclassification of the diseases that underlie Guillain-Barré syndrome (GBS) into acute inflammatory demyelinating polyradiculoneuropathy (AIDP), acute motor and sensory axonal neuropathy (AMSAN) and acute motor axonal neuropathy (AMAN). The Fisher syndrome of ophthalmoplegia, ataxia and areflexia is the most striking of several related conditions. Significant antecedent events include Campylobacter jejuni (4-66%), cytomegalovirus (5-15%), Epstein-Barr virus (2-10%), and Mycoplasma pneumoniae (1-5%) infections. These infections are not uniquely associated with any clinical subtype but severe axonal degeneration is more common following C. jejuni and severe sensory impairment following cytomegalovirus. Strong evidence supports an important role for antibodies to gangliosides in pathogenesis. In particular antibodies to ganglioside GM1 are present in 14-50% of patients with GBS, and are more common in cases with severe axonal degeneration associated with any subtype. Antibodies to ganglioside GQ1b are very closely associated with Fisher syndrome, its formes frustes and related syndromes. Ganglioside-like epitopes exist in the bacterial wall of C. jejuni. Infection by this and other organisms triggers an antibody response in patients with GBS but not in those with uncomplicated enteritis. The development of GBS is likely to be a consequence of special properties of the infecting organism, since some strains such as Penner 0:19 and 0:41 are particularly associated with GBS but not with enteritis. It is also likely to be a consequence of the immunogenetic background of the patient since few patients develop GBS after infection even with one of these strains. Attempts to match the subtypes of GBS to the fine specificity of anti-ganglioside antibodies and to functional effects in experimental models continue but have not yet fully explained the pathogenesis. T cells are also involved in the pathogenesis of most or perhaps all forms of GBS. T cell responses to any of three myelin proteins, P2, PO and PMP22, are sufficient to induce experimental autoimmune neuritis. Activated T cells are present in the circulation in the acute stage, up-regulate matrix metalloproteinases, cross the blood-nerve barrier and encounter their cognate antigens. Identification of the specificity of these T cell responses is still at a preliminary stage. The invasion of intact myelin sheaths by activated macrophages is difficult to explain according to a purely T cell mediated mechanism. The different patterns of GBS are probably due to the diverse interplay between antibodies and T cells of differing specificities.

The diagnostic value of sural nerve T cells in chronic inflammatory demyelinating polyneuropathy

BACKGROUND

T-cell infiltrates in sural nerve biopsy specimens of patients with inflammatory neuropathies have been reported, suggesting a role for T cells in the pathogenesis, but the specificity of the presence and localization of sural nerve T cells in chronic inflammatory demyelinating polyneuropathy (CIDP) is unknown.

OBJECTIVE

To study the diagnostic value of the number and distribution of sural nerve T cells in CIDP.

METHODS

We performed a quantitative immunohistochemical examination of T cells in sural nerve biopsy specimens taken from 23 patients with a CIDP and compared them with sural nerves of 15 patients with a chronic idiopathic axonal polyneuropathy (CIAP), 5 patients with a vasculitic neuropathy, and 10 normal controls.

RESULTS

T cells were found in sural nerves of all CIDP patients as well as in all disease and normal controls. Only six CIDP patients had increased numbers and densities of T cells compared with CIAP patients and controls. Based on the distribution of endoneurial or epineurial T cells, it was not possible to differentiate CIDP patients from CIAP patients or normal controls. In patients and controls perivascular epineurial T cells predominated. Increased numbers and densities of sural nerve T cells in patients with CIDP were associated with female sex, a more severe disease course, worse outcome, highly elevated CSF protein level, and a larger sural nerve area, but not with loss of myelinated nerve fibers in the sural nerve biopsy sample or demyelinating features on electrophysiologic examination.

CONCLUSIONS

In the majority of CIDP patients, the number and distribution of T cells in sural nerve biopsy samples were similar to patients with noninflammatory neuropathies and normal controls. Only large numbers of sural nerve T cells are specific for inflammatory neuropathies and therefore of diagnostic value for CIDP.

Linomide suppresses experimental autoimmune neuritis in Lewis rats by inhibiting myelin antigen-reactive T and B cell responses

Linomide (quinoline-3-carboxamide) is a synthetic immunomodulator that suppresses several experimental autoimmune diseases. Here we report the effects of Linomide on experimental autoimmune neuritis (EAN), a CD4+ T cell-mediated animal model of acute Guillain-Barré syndrome (GBS) in humans. EAN induced in Lewis rats by inoculation with bovine peripheral nervous system (PNS) myelin and Freund's complete adjuvant was strongly suppressed by Linomide administered daily subcutaneously from the day of inoculation. Linomide dose-dependently delayed the interval between immunization and onset of clinical EAN, as well as the severity of EAN symptoms. These clinical effects were associated with dose-dependent down-modulation of PNS antigen-induced T and B cell responses and with suppression of the proinflammatory cytokines IL-12, interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF-alpha) mRNA. In PNS sections, Linomide suppressed IL-12 and TNF-alpha, and up-regulated IL-10 mRNA expression. These findings suggest that Linomide could be useful in certain T cell-dependent autoimmune diseases.

Subacute inflammatory polyneuropathy: two cases with plasmacytoid histiocytes in the endoneurium

Inflammatory polyneuropathies are mainly known by their acute form, Guillain-Barré syndrome, but there are also chronic cases and all are considered as having an autoimmune mechanism. In each form, peripheral nerve biopsies show scattered macrophages in the endoneurium and in certain cases macrophages invade the Schwann cell cytoplasm and destroy the myelin sheath. In rarer cases there is a primary axonal degeneration. The authors studied two chronic cases, which both exhibited mixed primitive axonal and demyelinating lesions, with peculiar histiocytes in the endoneurium. These rounded cells were characteristically well marked by KP1 but showed well-developed rough endoplasmic reticulum cysternae at ultrastructural examination. Such plasmacytoid histiocytes have mainly been studied in subacute lymphadenopathies and have been only briefly illustrated in a few cases of peripheral neuropathies due to Lyme disease or HIV infection. The two cases reported here had no associated diseases and probably correspond to a peculiar subacute autoimmune reaction.

The distribution of CD1 molecules in inflammatory neuropathy

The CD1 molecules have been shown to present non-protein antigens, such as complex lipids to Mycobacteria, and may be important in presenting glycolipids which are involved in inflammatory neuropathies. To study the expression of CD1 molecules in peripheral nerve, we examined nerve biopsies from two patients with acute inflammatory demyelinating polyradiculoneuropathy (AIDP), five with acute axonal neuropathy, six with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), nine with chronic axonal neuropathy, six with vasculitic neuropathy and three with no histological abnormality. Immunocytochemical studies showed strong labelling of CD1b on endoneurial macrophages (CD68+) and on myelinated nerve fibres in both AIDP patients, but it was rarely observed in the other patients. Weaker staining was seen on endoneurial macrophages and/or other endoneurial cells in some of the patients with other peripheral neuropathies, but none of the control nerves. CD1a had a weaker, but similar pattern. There was endoneurial infiltration of CD4+ and CD8+ T cells in the AIDP and CIDP nerves and sometimes in the other peripheral neuropathy nerves, but not in the normal nerves. Most T cells had alpha beta+ T cell receptors (TCR), but gamma delta+ TCR T cells were found in the nerves of both AIDP patients and sometimes in the nerves of other patients with peripheral neuropathy. Staining for mannose receptor was almost universal, being more intense in AIDP, chronic axonal neuropathy and vasculitis patients. We conclude that CD1 molecule expression is upregulated in peripheral neuropathy, especially in association with inflammation.

Matrix metalloproteinases MMP-9 and MMP-7 are expressed in experimental autoimmune neuritis and the Guillain-Barré syndrome

Matrix metalloproteinases (MMPs) are a family of enzymes that may be implicated in the pathogenesis of inflammatory demyelinating disorders such as multiple sclerosis. The present study investigated the expression of 92-kd gelatinase (MMP-9) and five other MMPs in sciatic nerve from Lewis rats with autoimmune experimental neuritis (EAN), an experimental model of the Guillain-Barré syndrome (GBS). Quantitative polymerase chain reaction analysis revealed an up-regulation of MMP-9 mRNA with peak levels concurrent with maximal disease severity. Increased mRNA expression was associated with enhanced enzyme activity, as detected by gelatin zymography. Immunohistochemically, MMP-9 could be localized primarily around blood vessels within the epineurium and endoneurium in diseased but not normal sciatic nerve. Among all other MMPs investigated, mRNA levels of matrilysin (MMP-7) were found to be up-regulated at the peak of the disorder, remaining at high levels throughout the clinical recovery phase of the disease. To apply these findings to human disease, sural nerve biopsies from GBS patients were examined. By using immunohistochemistry, positive immunoreactivity against MMP-9 and MMP-7 was noted and corroborated by demonstrating augmented mRNA expression in comparison with noninflammatory neuropathies. Furthermore, increased MMP-9 activity was detected by zymography. These findings indicate that 92-kd gelatinase and matrilysin are selectively up-regulated during EAN and expressed in nerves of GBS patients and thus may contribute to the pathogenesis of inflammatory demyelination of the peripheral nervous system.

Circulating tumor necrosis factor-alpha correlates with electrodiagnostic abnormalities in Guillain-Barré syndrome

Autoimmune damage to peripheral nerves, mediated by activated T lymphocytes and macrophages, underlies the pathogenesis of inflammatory demyelination in Guillain-Barré syndrome. Both T lymphocytes and macrophages secrete tumor necrosis factor-alpha, a cytokine that exerts toxic effects on myelin, Schwann cells, and endothelial cells. The reportedly high serum levels of this cytokine in patients with Guillain-Barré syndrome may reflect the degree of immune activation rather than a direct pathogenic effect. We compared serum levels of tumor necrosis factor-alpha, interleukin-1 beta, and soluble interleukin-2 receptor with well-established electrodiagnostic criteria for primary demyelination in 23 patients with Guillain-Barré syndrome, to assess the relationship between these cytokines and peripheral myelin damage. High serum levels of tumor necrosis factor-alpha were associated with prolonged distal motor latencies and slowed motor conduction velocities, prolonged or absent F-wave responses, and reduced amplitude of distal compound muscle action potentials. No significant correlation was observed between electrodiagnostic criteria for primary demyelination and serum levels of interleukin-1 beta or soluble interleukin-2 receptor. These findings suggest a putative role of tumor necrosis factor-alpha in the pathogenesis of peripheral nerve demyelination in Guillain-Barré syndrome.

Cytomegalovirus infections and anti-GM2 antibodies in Guillain-Barré syndrome

To investigate whether antecedent cytomegalovirus (CMV) infections in patients with Guillain-Barré syndrome are associated with the presence of specific antiganglioside antibodies, acute phase serum samples from 130 patients with Guillain-Barré syndrome and 200 controls were tested. Anti-GM2 IgM antibodies were found more often in patients with Guillain-Barré syndrome with CMV infection (22%) than in patients without the infection (2%) (P = 0.003). CMV infections may elicit anti-GM2 antibodies in susceptible patients, which may contribute to the pathogenesis of Guillain-Barré syndrome associated with CMV.

T cell receptor V beta gene usage in Guillain-Barré syndrome

We set out to determine whether the T cell receptor (TCR) V beta gene usage in acute inflammatory demyelinating polyradiculoneuropathy (AIDP) is restricted. We separated activated from non-activated peripheral blood T cells with anti-IL2 receptor (anti-CD25) antibody-labelled magnetic beads from four AIDP patients and four normal control (NC) subjects. The TCR V beta gene usage of circulating activated and non-activated T cells was heterogeneous in all the patients and controls, but the activated T cells of all four of the AIDP patients showed a more limited usage of V beta genes and enhanced V beta 15 usage, as compared to the non-activated T cells. This was not seen in the healthy controls. The activated and non-activated T cells from a patient with acute motor and sensory axonal neuropathy (AMSAN) showed a similar V beta gene usage to that of the controls. From a further patient with AIDP, we studied the V beta gene usage of short-term T cell lines reactive to the peripheral nerve myelin proteins P2, P0 and the P0 peptide amino acid sequence 194-208. The V beta gene usage of the lines was heterogeneous, with enhanced usage of V beta 15 in the cell line responsive to the Pzero peptide. We conclude that T cells activated during the immune response associated with AIDP preferentially used V beta 15, which may indicate a restricted response to a common antigen, or a role for an as yet undefined superantigen in the pathogenesis of AIDP.

Isolation and characterisation of T lymphocytes from sural nerve biopsies in patients with Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy

OBJECTIVES

To characterise cultured T lymphocytes from nerve biopsies in patients with Guillain-Barré syndrome and chronic inflammatory demyelinating polyneuropathy (CIDP).

METHODS

Sural nerve biopsies, obtained from six patients with Guillain-Barré syndrome, four with CIDP, and six controls with other neuropathies, were cultured with 20 U/ml recombinant interleukin-2 (IL-2) for eight weeks. Flow cytometry was used to determine the phenotype of cultured T lymphocytes. Their proliferative responses to a range of bacterial antigens were also examined.

RESULTS

T cell lines were established from four of six patients with Guillain-Barré syndrome, one of four with CIDP, one patient with peripheral nerve vasculitis, and none of five controls with non-inflammatory neuropathies. One of these T cell lines from a patient with Guillain-Barré syndrome, preceded by Campylobacter jejuni infection, consisted entirely of gamma delta TCR+ T lymphocytes. The peripheral blood of this patient also contained an increased frequency of gamma delta T cells when stimulated with C jejuni. The nerve derived T cell lines failed to show a proliferative response to bacterial antigens or to a preparation of myelin proteins.

CONCLUSIONS

A new technique to isolate T cells from nerve biopsies in patients with Guillain-Barré syndrome and CIDP is reported. This technique may prove to be a useful tool in the investigation of the pathogenesis of other inflammatory neuropathies such as peripheral nerve vasculitis. The isolation of a gamma delta TCR+ nerve T cell line is of interest because of the possibility that these cells might respond to glycolipid epitopes common to C jejuni and peripheral nerve gangliosides.

Inflammatory infiltrates in sural nerve biopsies in Guillain-Barre syndrome and chronic inflammatory demyelinating neuropathy

Prompted by observations in experimental autoimmune neuritis we reanalyzed immunohistochemically the inflammatory infiltrates in sural nerve biopsies of 22 cases with Guillain-Barre syndrome (GBS) and 13 cases with chronic inflammatory demyelinating polyneuropathy (CIDP). Endoneurial infiltration of CD3+ T cells was found in 20 cases of GBS (median 5.5 cells/mm(2)) and in 10 cases of CIDP (5 cells). Epineurial T cells were present in all GBS cases (19.5 cells) and in 11 CIDP cases (21 cells). CD68+ macrophages were abundant in these neuropathies and often occurred in endoneurial perivascular clusters. In GBS subgroups the number of endoneurial T cells was significantly higher in patients with hypoesthesia and abnormal electrophysiological findings in the sural nerve. In CIDP hypoesthesia was associated with significantly higher numbers of macrophages. Our study also indicates that other factors including the time point of biopsy or previous corticosteroid treatment may influence the inflammatory cell profile. Quantifying cell infiltration may aid in establishing the diagnosis of an immunoneuropathy in patients with mild and noncharacteristic pathology.

Immunopathogenesis and treatment of the Guillain-Barré syndrome--Part I

The etiology of the Guillain-Barré syndrome (GBS) still remains elusive. Recent years have witnessed important advances in the delineation of the mechanisms that may operate to produce nerve damage. Evidence gathered from cell biology, immunology, and immunopathology studies in patients with GBS and animals with experimental autoimmune neuritis (EAN) indicate that GBS results from aberrant immune responses against components of peripheral nerve. Autoreactive T lymphocytes specific for the myelin antigens P0 and P2 and circulating antibodies to these antigens and various glycoproteins and glycolipids have been identified but their pathogenic role remains unclear. The multiplicity of these factors and the involvement of several antigen nonspecific proinflammatory mechanisms suggest that a complex interaction of immune pathways results in nerve damage. Data on disturbed humoral immunity with particular emphasis on glycolipid antibodies and on activation of autoreactive T lymphocytes and macrophages will be reviewed. Possible mechanisms underlying initiation of peripheral nerve-directed immune responses will be discussed with particular emphasis on the recently highlighted association with Campylobacter jejuni infection.

Increased CSF C4d in demyelinating neuropathy indicates the radicular involvement

Plasma and cerebrospinal fluid (CSF) levels of C4d and the circulating immune complex (CIC) to C1q were measured in 12 patients with chronic inflammatory demyelinating polyneuropathy and Guillain-Barré syndrome. CSF C4d values more than 2 SD from the mean of 8 cervical spongylosis cases were demonstrated in the patients with proximal demyelination. The CSF C4d probably originated from both intrathecal synthesis and the systemic circulation. CSF levels of C4d may serve as a sensitive indicator for the radicular involvement in demyelinating polyneuropathy.

Elevated serum levels of tumor necrosis factor-alpha in Guillain-Barré syndrome

Activated T lymphocytes and macrophages play a putative role in the the pathogenesis of Guillain-Barré syndrome. Both cell types secrete tumor necrosis factor-alpha, a cytokine that has well-recognized toxic effects on myelin, Schwann cells, and endothelial cells. We determined serum and cerebrospinal fluid concentrations of tumor necrosis factor alpha in 26 patients with Guillain-Barré syndrome, 27 patients with other polyneuropathies, 30 patients with neurological diseases of the central nervous system, and 14 healthy control subjects. Markedly increased serum levels were detected in 14 patients (54%) with Guillain-Barré syndrome and to a significantly lesser extent, in patients with other polyneuropathies (26%) and in neurological control subjects (23%). Tumor necrosis factor-alpha was not detected in the cerebrospinal fluid of patients with Guillain-Barré syndrome or other polyneuropathies. Increased serum concentrations in patients with Guillain-Barré syndrome correlated directly with disease severity and these concentrations returned to normal in parallel with clinical recovery. These findings emphasize the complexity of the immune response in patients with Guillain-Barré syndrome and suggest that tumor necrosis factor-alpha may be important in the pathogenesis of peripheral demyelination in this disorder.

Acute neuromuscular respiratory paralysis

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Immunoelectronmicroscopical demonstration of major histocompatibility class II antigen: expression on endothelial and perivascular cells but not Schwann cells in human neuropathy

A pre-embedding technique for identifying major histocompatibility (MHC) class II antigen with monoclonal antibody LN3 at the electron microscope level by immunogold silver enhancement was applied to sections from 12 human nerve biopsies. Many perivascular mononuclear cells in the epineurium, perineurium and endoneurium expressed MHC class II antigen and had the morphological appearance of macrophages. Cell processes expressing MHC class II antigen extended throughout the endoneurium, often close to Schwann cells. No MHC class II expression was identified on myelinating or non-myelinating Schwann cells. The endothelial cells of epineurial blood vessels expressed MHC class II antigen on their luminal surfaces more often and more strongly than those of the endoneurial vessels. These observations indicate that perivascular cells in both the endoneurium and perineurium commonly express the molecules necessary to present antigen to CD4+ T lymphocytes, but Schwann cells do not.

Electrophysiological changes in the acute "axonal" form of Guillain-Barre syndrome

The acute "axonal" form of Guillain-Barre syndrome is characterized by rapid progression to severe widespread paralysis and respiratory dependence within 2-5 days of the onset of weakness with very poor and delayed recovery. In 3 cases studied within the first 7 days, the maximum thenar, hypothenar, tibialis anterior, and extensor digitorum brevis "M" potentials were either very reduced in size or absent in response to stimulation at the usual most distal sites of stimulation at the wrist, fibular head, and/or ankle. In the latter instances, advancing the site of stimulation closer to the motor point often evoked an M response. Furthermore, continued distal advance of the site of stimulation evoked progressively larger sized M potentials. Over succeeding days even these very distally evoked M potentials disappeared. Maximum conduction velocities in motor nerve fibers just prior to total loss of excitability were often very reduced. The pattern in these cases is most consistent with progressive loss of excitability and conduction in nerve fibers undergoing axonal degeneration, although coexisting primary demyelination in the terminal segment could not be excluded as the basis for the sometimes very slowed conduction velocities.