Recurrent experimental allergic neuritis. An electron microscope study

Hepatitis B Precipitating Neurological Complications: A Chronic Inflammatory Demyelinating Polyneuropathy (CIDP) Conundrum

Hepatitis B virus stands as a prominent contributor to cirrhosis, hepatocellular carcinoma, and other liver-related fatalities. On the other hand, neurological manifestations in HBV-infected individuals are infrequently observed. Chronic inflammatory demyelinating polyneuropathy (CIDP) represents an immune-mediated neuropathy, known for its distinctive pattern of symmetrical involvement and weakness in both proximal and distal muscles. In this study, we present a noteworthy instance of chronic inflammatory demyelinating polyneuropathy (CIDP) occurring in a patient with chronic inactive hepatitis B infection.

YAP and TAZ regulate Schwann cell proliferation and differentiation during peripheral nerve regeneration

YAP and TAZ are effectors of the Hippo pathway that controls multicellular development by integrating chemical and mechanical signals. Peripheral nervous system development depends on the Hippo pathway. We previously showed that loss of YAP and TAZ impairs the development of peripheral nerve as well as Schwann cell myelination. The role of the Hippo pathway in peripheral nerve regeneration has just started to be explored. After injury, Schwann cells adopt new identities to promote regeneration by converting to a repair‐promoting phenotype. While the reprogramming of Schwann cells to repair cells has been well characterized, the maintenance of such repair phenotype cannot be sustained for a very long period, which limits nerve repair in human. First, we show that short or long‐term myelin maintenance is not affected by defect in YAP and TAZ expression. Using crush nerve injury and conditional mutagenesis in mice, we also show that YAP and TAZ are regulators of repair Schwann cell proliferation and differentiation. We found that YAP and TAZ are required in repair Schwann cells for their redifferentiation into myelinating Schwann cell following crush injury. In this present study, we describe how the Hippo pathway and YAP and TAZ regulate remyelination over time during peripheral nerve regeneration.

NRG1 type I dependent autoparacrine stimulation of Schwann cells in onion bulbs of peripheral neuropathies

In contrast to acute peripheral nerve injury, the molecular response of Schwann cells in chronic neuropathies remains poorly understood. Onion bulb structures are a pathological hallmark of demyelinating neuropathies, but the nature of these formations is unknown. Here, we show that Schwann cells induce the expression of Neuregulin-1 type I (NRG1-I), a paracrine growth factor, in various chronic demyelinating diseases. Genetic disruption of Schwann cell-derived NRG1 signalling in a mouse model of Charcot-Marie-Tooth Disease 1A (CMT1A), suppresses hypermyelination and the formation of onion bulbs. Transgenic overexpression of NRG1-I in Schwann cells on a wildtype background is sufficient to mediate an interaction between Schwann cells via an ErbB2 receptor-MEK/ERK signaling axis, which causes onion bulb formations and results in a peripheral neuropathy reminiscent of CMT1A. We suggest that diseased Schwann cells mount a regeneration program that is beneficial in acute nerve injury, but that overstimulation of Schwann cells in chronic neuropathies is detrimental.

Onion bulbs are a hallmark of demyelinating peripheral neuropathies. Here the authors identify Neuregulin-1 type I expression in Schwann cells as an essential mechanism involved in the formation of these characteristic structures.

Pathophysiology and biomarkers in chronic inflammatory demyelinating polyradiculoneuropathies

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an acquired dysimmune disorder characterized by strong heterogeneity in terms of clinical manifestations, prognostic and response to treatment. To date, its pathophysiology and potential target antigens are not totally identified despite substantial progress in the understanding of the involved molecular mechanisms. Recent researches in the field have underlined the importance of cell-mediated immunity (lymphocytesT CD4+, CD8+ and macrophages), the breakdown of blood-nerve barrier, a failure of T-cell regulation, and the disruption of nodal and paranodal organization at the node of Ranvier. This last point is possibly mediated by autoantibodies towards axoglial adhesion molecules which may disrupt sodium and potassium voltage-gated channels clustering leading to a failure of saltatory conduction and the apparition of conduction blocks. The purpose of this article is to overview the main pathophysiologic mechanisms and biomarkers identified in CIDP.

Overview of the pathogenesis and treatment of chronic inflammatory demyelinating polyneuropathy with intravenous immunoglobulins

Chronic inflammatory demyelinating polyneuropathy (CIDP) is an acquired heterogeneous disorder of immune origin affecting the peripheral nerves, causing motor weakness and sensory symptoms and signs. The precise pathophysiology of CIDP remains uncertain although B and T cell mechanisms are believed to be implicated. Intravenous immunoglobulins (IVIg) have been shown in a number of trials to be an effective treatment for CIDP. IVIg is thought to exert its immunomodulatory effects by affecting several components of the immune system including B-cells, T-cells, macrophages and complement. This article provides an overview of the pathogenesis of CIDP and of its treatment with IVIg.

Pathogenesis of chronic inflammatory demyelinating polyradiculoneuropathy

The acute lesions of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) consist of endoneurial foci of chemokine and chemokine receptor expression and T cell and macrophage activation. The myelin protein antigens, P2, P0, and PMP22, each induce experimental autoimmune neuritis in rodent models and might be autoantigens in CIDP. The strongest evidence incriminates P0, to which antibodies have been found in 20% of cases. Failure of regulatory T-cell mechanism is thought to underlie persistent or recurrent disease, differentiating CIDP from the acute inflammatory demyelinating polyradiculoneuropathy form of Guillain-Barré syndrome. Corticosteroids, intravenous immunoglobulin and plasma exchange each provide short term benefit but the possible long-term benefits of immunosuppressive drugs have yet to be confirmed in randomised, controlled trials.

A morphological and morphometric study of the peripheral process of the human vestibular nerve following posterior cranial fossa neurectomy

Three vestibular nerve specimens removed at transmeatal neurectomy were studied in order to understand better retrograde degeneration and regeneration after vestibular neurectomy in the posterior cranial fossa. In two cases this procedure followed retrolabyrinthine retrosigmoid posterior fossa vestibular neurectomy. The subjects, three patients with Menière's disease, were compared with one another and two autopsy controls with no known otological problem. The specimens were obtained at the distal end of the internal auditory canal and transversely sectioned. Many collapsed Schwann cell basement membranes were observed. The ratio of small-diameter nerve fibres increased significantly after neurectomy. Onion bulb formation around myelinated nerve fibres with small diameters and Schwann cell proliferation around the soma of vestibular ganglion cells reflected remyelination. We conclude that peripheral processes of vestibular nerve fibres can undergo retrograde degeneration and subsequent regeneration after transection of the central process.

Chronic inflammatory demyelinating polyneuropathy with multifocal CNS demyelination in an Afrid

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Chronic immune-related demyelinating neuropathies

In recent years many important advances have been made in the knowledge of the mechanisms that may produce peripheral nerve damage. Data in the literature indicate that in some chronic demyelinating neuropathy autoantibodies against myelin antigens may play a pathogenic role. The pathogenic role of T cells, cytokines, complement, and class II molecules has also been studied. Identification of specific immune-related demyelinating polyneuropathies provides clues to future therapeutic approaches. This paper focuses on the chronic inflammatory demyelinating polyneuropathy, chronic demyelinating neuropathies associated with monoclonal gammapathies of undetermined significance, and multifocal motor neuropathy, and reviews their clinical, patophysiological and immunological features.

An electrophysiological and histological study of trypsin induced demyelination

Ten-microliters quantities of trypsin or saline were injected into rat tibial nerve and the physiological and histological changes evaluated and compared to the focal demyelinating lesions induced by intraneural injection of rabbit EAN serum and proteinase K. The injection of trypsin produced progressive conduction block that was maximal on day 4, and a slowing of motor nerve conduction. Early retraction of myelin at paranodes, vesicular change, and macrophage stripping of myelin from nerve axons were seen on histological examination. At day 4, the first groups of completely demyelinated axons were seen, typically in a perivascular distribution. These changes were similar to those seen in the positive controls and thus support the postulate that proteolytic enzymes from macrophages--the dominant cellular species within the demyelinating lesion, play a central role in degradation of the myelin sheath in demyelinating diseases.

Molecular genetics and neuropathology of Charcot-Marie-Tooth disease type 1A

Charcot-Marie-Tooth (CMT) syndrome describes a genetically and clinically heterogeneous group of polyneuropathies. Electrophysiologically, at least two types of CMT can be distinguished; CMT1 which has decreased nerve conduction velocities (NCV) and CMT2 which has normal or near normal NCV with decreased amplitudes. For CMT1, three gene loci (on chromosomes 1, 17 and the X chromosome) have been mapped. The locus on chromosome 17, CMT type 1A (CMT1A), is responsible for the most common form of CMT which has recently been shown to be associated with a large DNA duplication. Recent data demonstrates that the CMT1A phenotype results from an inherited DNA rearrangement and a gene dosage effect. The trembler (Tr) and allelic tremblerJ (TrJ) mice have been proposed as animal models for CMT. Tr has similar electrophysiological and neuropathological features to CMT1 patients and maps to mouse chromosome 11 in a region of conserved synteny with human chromosome 17p. Tr and TrJ have recently been shown to have different point mutations in regions encoding putative transmembrane domains of the myelin specific protein PMP-22. The human peripheral nerve-specific PMP-22 gene maps within the CMT1A duplication. PMP-22 is thus a candidate gene for CMT1A. This paper describes the molecular genetics of CMT1A and sural nerve pathology in CMT1A patients with the CMT1A duplication.

Neuropathological findings in chronic relapsing experimental allergic neuritis induced in the Lewis rat by inoculation with intradural root myelin and treatment with low dose cyclosporin A

Experimental allergic neuritis (EAN) was induced in Lewis rats by inoculation with bovine intradural root myelin and adjuvants. Rats treated with subcutaneous cyclosporin A (CsA) (4 mg/kg on 3 days per week from the day of inoculation until day 29) developed a chronic relapsing course. Tissues from the spinal cord, nerve roots, dorsal root ganglia and sciatic nerve of CsA-treated rats sampled during relapses and remissions were studied by light and electron microscopy. Control rats that were not treated with CsA were studied during or after episodes of acute EAN. Both control and CsA-treated animals studied in the first episode of EAN had evidence of inflammation and primary demyelination of the nerve roots and dorsal root ganglia. In control and CsA-treated animals that had recovered from the first episode there was evidence of remyelination. In CsA-treated animals in the second episode there was severe inflammation and demyelination and remyelination of the nerve roots and dorsal root ganglia, and in addition there was significant demyelination and remyelination in the spinal nerves and sciatic nerves and dorsal columns of the spinal cord, particularly in later stages of disease. In later episodes there was less inflammation, but there was continuing demyelination and onion bulbs were present. In animals sampled after recovery from chronic relapsing EAN onion bulbs were present. Occasional small onion bulbs were also observed in control animals that were inoculated with higher doses of myelin. Plasma cells were present in the inflammatory lesions of later episodes. Mast cells were also observed at different stages of the disease. We conclude that the CsA form of chronic relapsing EAN has clinical and pathological similarities with the human disease, chronic inflammatory demyelinating polyradiculoneuropathy.

Interferon-gamma inhibition suppresses experimental allergic neuritis: modulation of major histocompatibility complex expression of Schwann cells in vitro

This study examines the modulation of major histocompatibility complex (MHC) expression on Lewis rat Schwann cells (Scs) cultured in the presence of dorsal root ganglion neurons (DRG). MHC class I and II molecules were induced on Scs using recombinant murine interferon-gamma (IFN-gamma), lymph node cells (LNC), removed at day 9 from Lewis rats with experimental allergic neuritis (EAN) and syngeneic T-cell line cells responsive to P2 basic protein. EAN LNC induced MHC class I on Scs but only IFN-gamma or P2-responsive T-cells induced MHC class II. Control LNC from animals injected with Freund's adjuvant alone or naive spleen cells did not induce MHC class II. P2 T-cells clustered in aggregates to the Scs. Similar studies were performed with inhibitors of IFN-gamma; hydrocortisone, cyclosporin A, dibutyryl cyclic AMP, methyl-xanthine and prostaglandin E2. Each agent produced a dose-dependent inhibition of MHC expression and prevented clustering of P2-responsive T-cells to Scs.

Unmyelinated fibers in sural nerve biopsies of chronic inflammatory demyelinating polyneuropathy

Seven patients aged 29 to 76 years with various clinical subtypes of chronic inflammatory demyelinating polyneuropathy (CIDP) were investigated. Sural nerve biopsies were performed between 7 months and 19 years after onset of disease. Quantitative electron microscopy revealed involvement of primary unmyelinated fibers (UF) in all cases. When compared with age-matched controls from the literature and two controls of our own, there was an increase of degenerating primary UF in all cases, a definite decrease of density per mm2 or number per nerve after subtraction of regenerates of myelinated and unmyelinated fibers in five cases, an increase of denervated Schwann cell complexes of the unmyelinated type in three cases, and an increased incidence of a high ratio (greater than or equal to 3) of primary UF per Schwann cell complex in five cases. Presumably due to the small number and heterogeneity of cases, the results did not correlate with type and duration of CIDP, but were obviously influenced by the degree of demyelination. The possible causes of UF damage in CIDP are discussed.

The effects of prophylactic cyclosporin A on experimental allergic neuritis (EAN) in the Lewis rat. Induction of relapsing EAN using low dose cyclosporin A

Experimental allergic neuritis (EAN) was induced in Lewis rats by inoculation with bovine intradural root myelin plus adjuvants. Animals treated with high dose (30 mg/kg) cyclosporin A (CsA) 3 times per week did not develop clinical EAN during the period of CsA treatment, but had an episode of EAN after cessation of CsA treatment. Animals treated with low dose (4 mg/kg) CsA 3 times per week developed EAN during the period of treatment, and after cessation of CsA treatment all of these animals developed relapsing EAN with disease continuing for up to four episodes. In contrast, 30-40% of untreated animals had a mild second episode of EAN but no further attacks. Histological studies performed in treated and untreated animals at the time of clinical episodes revealed inflammation and demyelination in the spinal roots and dorsal root ganglia. When animals were challenged with a second inoculation at age 7 months, one of 15 untreated control animals but none of the CsA treated animals developed an episode of EAN.

Inflammatory demyelinating neuropathy in C57BL/KaLwRij mice

Neuropathies associated with monoclonal gammopathy (MG) in humans have been extensively studied in the past few years, but experimental models have proved difficult to create. C57BL mice are prone to develop benign MG and it has been reported that some of these mice with benign IgG MG present an inflammatory demyelinating neuropathy (IDN). In order to verify such findings, the serum and the sciatic nerve of the first group of 28 C57BL/KaLwRij mice were examined: none of 10 mice with normal serum showed ultrastructural abnormalities in the sciatic nerve, while lesions of IDN were present in three out of 10 mice with benign IgG MD, in two out of seven with benign IgM MG, and in a mouse with Waldenström-like lymphoma. The second group of animals was studied in the same way; it was composed of seven C57BL mice with transplanted multiple myeloma, and six C57BL mice with Morbus Waldenström-like lymphoma. In none of these animals, which were younger than those of the first group, was any lesion of IDN observed.

Chronic experimental allergic neuritis in Lewis rats

An experimental chronic relapsing demyelinating neuropathy was produced by immunizing adult Lewis rats with bovine myelin in low (2.5 mg) and high (5 mg) doses, with and without Mycobacterium tuberculosis in the adjuvant. Each regime produced a similar disease course: acute severe hind limb weakness was followed by apparent recovery and then reappearance of mild neurological deficit with occasional spontaneous exacerbations. The partially recovered animals were relatively resistant to reimmunization with myelin. Immunization of four-week-old rats with myelin in complete adjuvant produced disease with a similar course. Subsequent immunization of these juvenile rats with adjuvant alone precipitated exacerbations. In the late stages, the prominent changes in peripheral nerves and nerve roots were axon loss, axonal regeneration and remyelination while inflammatory cell infiltration was confined to occasional foci. Onion bulb formation was extremely common in the dorsal root ganglia and affected in particular the nerve fibres close to the dorsal root ganglion cells. The cells forming the onion bulbs resembled the satellite cells surrounding the axon hillocks. Onion bulb formation also occurred in the portion of the ventral roots adjacent to the dorsal root ganglion but was rare elsewhere. Immunocytochemistry revealed only occasional lymphocyte infiltration but there was increased Class I and Class II MHC antigen expression throughout the peripheral nervous system. The results are relevant to the interpretation of biopsies from patients with chronic demyelinating neuropathy of possible inflammatory or autoimmune origin.

Sural nerve biopsy in chronic inflammatory demyelinating polyradiculoneuropathy

We compared histologic features of sural nerve biopsies in 14 patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) with those in other forms of neuropathy. In CIDP endoneurial pericapillary cellular infiltrates were found in 4 patients (29%), onion bulbs in 5 patients (36%), and predominant demyelination in 7 patients (50%). None of these abnormalities was specific, but cellular infiltrates and onion bulbs appear to be diagnostically useful when combined with clinical information. To detect macrophage infiltration of myelin, cell nuclei were counter-stained in 20 teased fiber preparations. Nine patients with CIDP had a significantly higher mean number of cells per centimeter of teased fiber than 11 patients with other neuropathies. Despite overlap, significant infiltration of myelin detected by this method suggests CIDP in an appropriate clinical setting.

Disease patterns in experimental allergic neuritis (EAN) in the Lewis rat. Is EAN a good model for the Guillain-Barré syndrome?

Lewis rats develop experimental allergic neuritis (EAN) when injected with bovine dorsal root (BDR) emulsified in complete Freund's adjuvant (CFA). In this study the susceptibility to EAN and subsequent relapse was studied in animals ranging from 4 to 25 weeks of age. Older animals exhibited a severe acute illness which was monophasic over the period of observation, whereas younger animals developed a less severe and frequently relapsing illness. Very young animals often relapsed more than once and sometimes to a more severe degree than shown in their first attack. Older animals which were in the late recovery stage of EAN (44 days after injection with BDR/CFA) were completely resistant to a second challenge with antigen. Young adult animals also developed resistance but not as strongly as the older animals. Animals first injected at weaning developed resistance as in the adults, but the analysis is complicated by the occurrence of spontaneous relapses. Because of differences in disease pattern between EAN and acute inflammatory polyneuropathy (Guillain-Barré syndrome) in man, caution should be exercised in drawing too close a parallel between the animal model and the human disease. The affinities may be closer to chronic relapsing inflammatory polyradiculopathy in man.

Double myelination of axons in the sympathetic nervous system of the mouse. II. Mechanisms of formation

The phenomenon termed 'double myelination', present in sympathetic nerve of normal adult rats and mice, comprises regions of a myelinated axon which are concentrically ensheathed by additional (outer) myelinating Schwann cells. Evidence has been presented that in some instances the outer Schwann cell fails to make contact with an axon, yet its myelin sheath characteristically remains ultrastructurally intact. The present study has sought to identify and analyse configurations intermediate between single and double myelination, in order to determine the mechanism(s) underlying the formation of double ensheathment. Superior cervical ganglia from normal male mice aged 12-24 months were prepared for electron microscopy by systemic aldehyde perfusion. Regions of interest were extensively serial-sectioned for detailed electron microscopical analysis and reconstruction. The earliest evidence for alteration to the expected intimate ensheathment of axons by myelinating Schwann cells involved invasion of supernumerary Schwann cells and their processes at the node of Ranvier, resulting in displacement of the paranodal pockets from axonal contact. Similar paranodal displacement occurred at heminodes as a result of lateral extension and invasion of processes from the adjacent Schwann cell (i.e. the cell investing the unmyelinated domain of the axon). Subsequently, processes of the invading cell extended progressively into internodal regions, located at all times between the plasma membranes of the axon and displaced Schwann cell. The cytoplasmic pockets at the remaining paranode were then subject to invasion. At various stages of displacement myelin formation commenced within the invading cell, representing the first acquisition of double myelin ensheathment in the development of the configuration. Involvement of haematogenous cells in displacement was not detected. There was also evidence consistent with paranodal displacement by adjacent pre-existing myelinating cells, but this additional mechanism appeared minor relative to the involvement of (initially) non-myelinating Schwann cells. We found no evidence for the alternative possibility that Schwann cells could synthesize a myelin sheath around a pre-existing myelinated axon de novo, independent of any direct axonal contact. These results are consistent with the well-established requirement for axonal contact by Schwann cells engaging in initial myelin formation, in the sense that the myelin sheath of the outer cell was synthesized prior to its displacement, and that a myelin sheath was not formed by the invading cell until it had invested the axon in a 1:1 relationship.(ABSTRACT TRUNCATED AT 400 WORDS)

Chronic experimental allergic neuritis. An electrophysiological and histological study in the rabbit

Ten adult outbred New Zealand white rabbits were inoculated with a single multiportal dose of purified bovine peripheral nerve myelin and Freund's adjuvant containing 500 mg of nerve antigen. Seven animals developed chronic relapsing or progressive disease which was followed by clinical examination for 14 months. Electrophysiological studies showed marked slowing of motor conduction velocity, dispersion of the evoked muscle action potential (MAP) and reduction in amplitude of the MAP derived from distal stimulation. Histological examination of the peripheral nervous system showed at 12 months a marked hypertrophic neuropathy in the nerve roots with well developed onion bulbs, active demyelination and a moderate nerve fibre loss. It is suggested that these animals provide a reliable and predictable model for human chronic inflammatory demyelinating polyneuropathy (CIDP) which should prove valuable for therapeutic trials and studies of pathogenetic mechanisms.

The C57BL mice: an animal model for inflammatory demyelinating polyneuropathy

Recently it has been reported that the C57BL mice can be used as a model of benign monoclonal gammopathy (MG). Since experimental models have until now failed to reproduce specific lesions of human dysglobulinemic polyneuropathies, we decided to investigate the peripheral nerve of these mice. The sciatic nerve and the serum from 14 C57BL mice were examined: 9 of these animals were found to have an IgG, kappa light chain MG, while in the other 5 no abnormalities were detected in the serum. In the 14 mice, features of demyelination were found in certain fibers, as well as onion-bulb formations around other myelinated fibers. Features of active demyelination were found in 10 animals and it must be underlined that three of these had no serum abnormalities. The decrease of the conduction velocities and the temperature coefficients Q10 of the C57BL mice suggest a good correlation between morphological and functional parameters. This strongly suggests that this strain of mice provides a suitable model for inflammatory demyelinating polyneuropathy (IDPN).

Chronic relapsing experimental allergic neuritis in Lewis rats: effects of thymectomy and splenectomy

Experimental allergic neuritis (EAN) was induced in Lewis rats aged 4 months by the inoculation of whole bovine dorsal root with Freund's complete adjuvant. Prolonged follow-up demonstrated that a relapsing course is a regular feature of the disorder in animals at this age. Although the initial disease episode was the most severe, clinical recovery from subsequent relapses was less satisfactory, this probably being related to persistent morphological abnormalities in the peripheral nervous system. Antecedent thymectomy, splenectomy, or the two combined, had little effect on the clinical course of the disorder, apart from reducing the duration of relapses. This was only statistically significant following combined thymectomy/splenectomy. Histological abnormalities, however, tended to be less severe in the operated as compared with normal control or sham-operated animals with EAN. The animals must have attained an immunocompetent state at the time of thymectomy and/or splenectomy. The capacity to develop EAN presumably resides in the draining lymph nodes and the occurrence of relapses is due to the continuing presence of antigen at the injection sites.

Chronic experimental allergic neuritis (EAN) in juvenile guinea pigs: immunological comparison with acute EAN in adult guinea pigs

In order to approach the mechanism of chronic or relapsing course in human chronic inflammatory demyelinating polyradiculoneuropathy, we established a chronic model of experimental allergic neuritis (EAN) in juvenile guinea pigs, and investigated the underlying cellular immune phenomenon in comparison with acute EAN in adult animals of the same strain. Two-week-old Hartley guinea pigs, sensitized with bovine peripheral nerve homogenate, developed chronic or relapsing EAN, whereas all adult animals developed acute monophasic EAN. Morphological examination of both the chronic and acute forms revealed scattered demyelination and mononuclear cell infiltrates which were essentially restricted to the peripheral nervous system, and indistinguishable from each other. Both the in vitro lymphocyte mitogenic response and in vivo skin testing revealed a significantly lower response to neuritogenic antigens (P2 protein and peripheral nerve myelin) in juvenile chronic EAN than in adult acute EAN throughout their respective courses. In addition, we showed, by means of assessing peripheral blood lymphocyte number and its subpopulations, that normal 2-week-old Hartley guinea pigs have not fully developed immunologically. These observations suggested that there was some immunological incompetence especially in cellular immunity in 2-week-old juvenile guinea pigs and that this might be one possible factor leading to chronic EAN.

Attempts to suppress experimental allergic neuritis in the rat by pretreatment with antigen

The injection of bovine dorsal root antigen in complete Freund's adjuvant can be used to produce experimental allergic neuritis (EAN) in rats. In this study attempts were made to prevent the development of the disease by prior injections of antigen. It was found that eight intradermal (i.d.) injections of antigen in either incomplete Freund's adjuvant or in saline failed to suppress EAN. A single intraperitoneal (i.p.) injection of antigen in saline produced only minimal protection against the disease. However, it was found that rats which had been given a primary course of EAN were subsequently completely unresponsive to a second injection of antigen.

The treatment of experimental allergic neuritis by plasma exchange

Experimental allergic neuritis (EAN) is a demyelinating disease of the peripheral nervous system that can be induced in laboratory animals. This disorder has been considered to show many similarities to acute inflammatory polyneuropathy (Guillain-Barré syndrome, GBS). Reports that plasma exchange may benefit patients with GBS prompted the investigation of the effect of plasma exchange in EAN. A controlled study was performed on New Zealand White rabbits. Sixteen animals were allocated to control or treatment groups at the onset of the disease. Clinical assessment on days 7 and 14 showed that treated animals were less severely affected neurologically (P = 0.05, day 7; P less than 0.001 day 14), with a commensurate reduction in the severity of the histological lesions in peripheral nerves.

The response of the (myelinating) Schwann cell population to multiple episodes of demyelination

The effects of multiple intraneural injections of the known demyelinating agent lysophosphatidyl choline, LPC, have been studied in the sciatic nerves of adult mice. Up to six separate episodes of demyelination were induced at the same site within the tibial fascicle. Demyelination and subsequent remyelination occurred after each injection. The number of Schwann cells produced during each repair programme exceeded the number required for remyelination and some of the surplus cells temporarily remained associated with the remyelinating axon/Schwann cell units as supernumerary Schwann cells. There was a progressive decline in the proportion of promyelinated axons as the number of injections of LPC increased. The proposition that this could have reflected a more rapid repair following demyelination of thinly (re)myelinated axons was investigated in double LPC-injected nerves. No structures resembling onion bulbs characteristic of hypertrophic neuropathies in man were seen during the course of this study.

Studies with antisera against peripheral nervous system myelin and myelin basic proteins. I. Effects of antiserum upon living cultures of nervous tissue

We studied the effects of antiserum against rat peripheral nervous system (PNS) myelin, rat or chicken central nervous system myelin basic protein (BP), or rabbit P2 protein from PNS myelin on myelinated cultures containing only rat dorsal root ganglion neurons and Schwann cells. While anti-PNS myelin serum consistently produced segmental PNS demyelination, anti-BP serum and anti-P2 serum did not. The culture results suggest that the myelin PNS proteins P1 (identical to basic protein from central nervous system myelin) and P2 are not exposed on the extracellular surfaces of myelin-related Schwann cells in tissue culture.

Chronic idiopathic polyneuropathy treated with azathioprine

The results of azathioprine therapy in five patients with chronic progressive or relapsing idiopathic inflammatory polyneuropathy are described. In four patients a sustained improvement followed treatment and in the other patient azathioprine successfully replaced corticosteroid therapy. The improvement was often delayed for up to three months. The literature on the use of azathioprine in chronic polyneuropathy is reviewed. We suggest that there is a place for azathioprine treatment in patients with chronic idiopathic polyneuropathy resistant or intolerant to corticosteroid treatment.

Double myelination of axons in the sympathetic nervous system

Relationships between axons and Schwann cells in myelinated fibres of the superior cervical (sympathetic) ganglion have been examined in normal adult rats. In cross-sections through the ganglion up to 4% of myelinated fibres were focally encircled by an additional myelinating Schwann cell, forming regions termed 'double myelination'. In these regions and elsewhere in the ganglion, the structure of the inner fibre (axons and myelinating Schwann cell) conformed to the relationships expected on the basis of numerous previous investigations on normal peripheral nerve. However, the outer Schwann cell and myelin sheath, which formed an annulus around the inner fibre, was remarkable in that it apparently made no direct contact either with the centrally enclosed axons or with an neighbouring axon, yet appeared largely if not completely intact. In addition, the increasing frequency of double myelination in older animals and the rarity of myelin degeneration in the same ganglia indicate that the outer Schwann cell, and in particular its myelin sheath, persist for some period in an isolated form. Double myelination was not located in non-sympathetic peripheral nerve samples from the same animals. Double myelination may result from the displacement of one myelin internode by the interposition of another Schwann cell rendering the original Schwann cell redundant. There was no involvement of haematogenous cells as occurs in some demyelinating conditions. While some parallels may be found with previous studies, this would appear to be the first report of apparent survival of myelin in a Schwann cell not making, as far as could be determined in the present study, at least partial direct axonal contact. These observations on sympathetic nerve may provide a new perspective on axon-Schwann cell signalling.

Chronic relapsing polyneuritis. A light- and electron-microscopic study

The clinico-pathologic findings in two patients with chronic relapsing polyneuritis are reported. The patients had several attacks of diffuse polyneuritis followed by partial recovery. The tendency to persisting disability increased following relapses and in the late stages there was a progressive motor deterioration suggesting a continuing activity of nerve damage. The biopsies of peripheral nerves, obtained in the advanced stages of the disease, showed severe loss of myelinated fibers and aspects of repeated demyelination and remyelination, with formation of onion bulb complexes. Completely demyelinated axons together with remyelinating fibers as well as remyelinated fibers invested by macrophages were seen at the same time. The clinical and pathological evidences suggest that in chronic relapsing polyneuritis, at least in the late stages of the disease, besides clinical relapses, there is a continuing activity of nerve damage. Thus, due to this ongoing activity of demyelination and remyelination, the elimination of the supernumerary Schwann cells does not take place satisfactorily and hypertrophic changes of the nerve fascicles are produced.

The treatment of chronic relapsing and chronic progressive idiopathic inflammatory polyneuropathy by plasma exchange

Observations are reported on the effects of plasma exchange on three patients with chronic relapsing idiopathic inflammatory polyneuropathy and three with the chronic progressive form of this disorder. Substantial temporary improvement occurred in two of the chronic relapsing cases in relation to repeated plasma exchanges, but only slight improvement in the remainder. A striking feature was the rapidity of the effect in the patients that improved. The significance of these observations in relation to pathogenesis and to clinical management of the disorder is discussed.

Chronic relapsing (dysimmune) polyneuropathy: pathogenesis and treatment

Chronic relapsing polyneuropathy is a distinct dysschwannian/demyelinating polyneuropathy characterized by usually slow onset, progressive or relapsing-remitting course, elevated cerebrospinal fluid (CSF) protein, marked slowing of nerve conduction velocity, segmental demyelination demonstrable in sural nerve biopsies, and absence of systemic illness or abnormal serum immunoglobulins. The cause of the disorder and the mechanisms underlying its chronicity and relapsing-remitting course are not clear. Immunoglobulin deposition observed in sural nerve biopsies and abnormal immunoglobulin patterns in the "CSF in some cases suggest a dysimmune pathogenesis; thus the term chronic relapsing (dysimmune) polyneuropathy (CRDP) is preferred. The disease is a treatable form of idiopathic polyneuropathy. In our series of 25 patients with CRDP, treatment with high-single-dose daily prednisone, slowly tapered to an alternate-day program, has been very successful in the majority. A low (10 to 20 mg) alternate-day-single-dose program, maintained indefinitely, seems to be required to prevent future recurrences. Evidence is provided that other immunosuppressants (azathioprine, cyclophosphamide, poly-ICLC) and possibly plasmapheresis, alone or in conjunction with corticosteroids, may have a beneficial role in controlling difficult cases of chronic relapsing polyneuropathy.

Experimental allergic neuritis induced by galactocerebroside

Experimental allergic neuritis (EAN), an animal model of human demyelinative neuritis, was induced by sensitization with galactocerebroside, a glycolipid hapten common in central and peripheral nervous system myelin. Between two months and one year after the initial sensitization, 11 of 24 rabbits immunized repeatedly with bovine brain galactocerebroside (GC) in complete Freund's adjuvant developed a neurological disorder manifested by flaccid quadriparesis, limb hypesthesia, and respiratory paralysis. Seventeen of 20 autopsied rabbits, including all those with clinical illness, had small multiple perivascular foci of demyelinative lesions in roots, dorsal root ganglia, proximal peripheral nerves adjacent to ganglia, and, less frequently, in distal nerves. No change was found in the central nervous system. Demyelination started around venules, with splitting and vesiculation of the outer myelin sheaths of adjacent fibers, and later progressed to form confluent lesions. The lesions were associated with infiltration of phagocytic mononuclear cells, mostly macrophages, which insinuated themselves between myelin lamellae, phagocytized myelin, and subsequently denuded axons. Perivenular infiltration of small lymphocytes, comparable to that seen in whole nerve- induced EAN, was not encountered. The distribution of demyelinative lesions seems to correspond to areas known to have a defective blood-nerve barrier.

Antiserum-mediated demyelination: relationship between remyelination and functional recovery

A focal demyelinative lesion of peripheral nerve was produced by intraneural injection of either antiserum from rabbits with experimental allergic neuritis or experimental allergic encephalomyelitis or antiserum to galactocerebroside. We studied the relationship between clinical and electrophysiological recovery from this lesion and the morphological pattern of remyelination. Foot muscles on the the injected side weakened within an hour of injection and remained paralyzed for 7 days; strength gradually returned to normal by 16 days after injection. Electrophysiological conduction block, apparent within a few hours of injection, persisted for about 7 days. At 8 days we detected dispersed, very low amplitude muscle action potentials with long latency. Morphologically, demyelinated axons were surrounded by Schwann cells at 7 days after injection, but compacted myelin was not present. After 8 days, remyelinating axons became surrounded by thickening compacted myelin. The time of onset of remyelination and the rate of remyelination up to 14 days following the injection were independent of axon size. The onset of clinical and electrophysiological recovery from the lesion corresponded to the appearance of 2 to 8 myelin lamellae around each remyelinating axon. At 37 days after injection, when conduction velocities had returned to preinjection values, myelin thickness of remyelinating fibers had increased to approximately one-third that of control nerves.

Neuritogenic and chemical properties of guinea pig anterior and posterior root myelin

In relapsing experimental allergic encephalomyelitis, recurrent demyelination was found in the anterior roots and dorsal root ganglia with minimal involvement of the posterior roots. To determine whether this is an antigen-related phenomenon, the distribution, type and intensity of the lesions in the proximal PNS of guinea pigs immunized with anterior roots or myelin were compared to those of animals immunized with posterior roots or myelin. Homologous anterior roots were less neuritogenic than posterior roots or posterior root myelin. Thin layer chromatography of myelin samples from anterior and posterior roots, dorsal root ganglia and sciatic nerve revealed the presence of a sulfogalactoglycerolipid, tentatively identified as sulfated galactosylglyceride (SGG) in all but the posterior root myelin samples. Although the PNS lesions of relapsing experimental allergic encephalomyelitis appear to recapitulate the regional distribution of SGG, the reason why its presence in anterior roots myelin renders them less neuritogenic is at present not clear.

Relapsing neuropathy due to tetanus toxoid. Report of a case

A unique case history is presented, of a 42-year-old patient who has suffered three episodes of a demyelinating neuropathy, each of which followed an injection of tetanus toxoid. The clinical features on each occasion were characteristic of acute idiopathic polyneuropathy; a rapid onset of a mainly motor neuropathy with eventual recovery. Nerve conduction studies performed during the second and third episodes demonstrated grossly slowed motor conduction velocities. The sural nerve was biopsied after the third episode, and the features seen on light and electron microscopy included prominent hypertrophic changes, mononuclear cells associated with most "onion bulbs" and macrophage mediated demyelination. Studies of blastogenesis and macrophage migration inhibition, showed T lymphocyte responsiveness to both peripheral nerve myelin and tetanus toxoid. Typing for antigens of the HLA system indicated that the patient was homozygous for HLAB8.

Peripheral nervous system pathology in relapsing experimental allergic encephalomyelitis

A recurrent type of primary demyelination was found in the anterior roots and dorsal root ganglia of strain 13 guinea-pigs with relapsing experimental allergic encephalomyelitis. Single nerve fibre studies revealed a predominant nodal--paranodal distribution of the destruction of myelin in these nerves. Damage of the Schwann cell--axolemmal junction was found in the majority of the abnormal nodes of Ranvier. This was accompanied by the formation of supernumerary adaxonal Schwann cell processes which further altered the normal myelinating cell--axon relationship. It is concluded that variations in antigenic composition may play a role in the selective involvement of the anterior roots. The pathogenesis of the observed nodal changes is discussed.

The peroneal muscular atrophy syndrome. Clinical, genetic, electrophysiological and nerve biopsy studies. Part 2. Observations on pathological changes in sural nerve biopsies

The light-and electron-microscopic, single teased nerve and morphometric studies of a series of 17 sural nerve biopsies from patients with personeal muscular atrophy are presented. The cases are divided into the following groups according to the criteria of Davis, Bradley and Madrid (1977): Hypertrophic Neuropathy Group; Intermediate Group; Neuronal Sensorimotor Group; Neuronal Motor Group. The Hypertrophic Neuropathy Group had nerve hypertrophy and marked segmental demyelination and onion bulb formation. The Intermediate Group also had segmental demyelilination and onion bulb formation, but nerve hypertrophy was not seen, and axonal degeneration and regeneration were prominent. The Neuronal Sensorimotor Group cases were all sporadic, and showed some onion bulbs, paranodal demyelination and evidence of axonal degeneration and regeneration. The sensory nerve biopsy in the Neuronal Motor Group showed no major abnormality apart from some cluster formation indicating axonal regeneration. The data tend to support the classification of peroneal muscular atrophy proposed by Davis et al. (1977), though there was overlap between the groups in individual pathological parameters.

Dynamic aspects of peripheral nerve changes in progressive neural muscular atrophy: light- and electronmicroscopic studies of serial nerve biopsies

Serial nerve biopsies were performed at an early, and at an advanced stage of the disease in 2 patients with progressive neural muscular atrophy. The early biopsy showed a complete loss of the large diameter and thickly myelinated fibres, as well as an expansion of the endoneurial interstitium in both cases. Myelinated and unmyelinated fibres exhibited axonal degeneration in all biopsies occasionally. "Onion bulb" formation, a typical feature of peripheral neuropathy in neural muscular atrophy, was found to be prominent only in the latter biopsies. As regards the formal pathogenesis of hypertrophic neuropathy in neural muscular atrophy, axonal dystrophy and interstitial changes of the endoneurium were regarded as primary phenomena, demyelination and "onion bulb" formation as secondary. A possible causal relation between axonal dystrophy and interstitial changes, observed in these cases, is discussed in the light of the present literature.