Passive transfer of demyelination by experimental allergic neuritis serum

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.

Endoneurial injection of antisera to myelin antigens

When antisera to purified myelin antigens were injected into rat sciatic nerves, some produced significant demyelination, whereas others merely induced an inflammatory infiltrate. Extensive demyelination was produced by antisera to galactocerebroside and the peripheral nerve glycoprotein P0. Demyelination resulting from injections of antisera to ganglioside GM1, P2, myelin basic protein, sulfatide, and glucocerebroside did not exceed that produced by normal rabbit serum. Addition of guinea pig complement had no effect. It is of interest that the greatest demyelination followed injection of antisera to two molecules, galactocerebroside and P0, the main antigenic determinants of which present at the Schwann cell surface.

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.

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.

Cauda equina syndrome

Single or double-level compression of the lumbosacral nerve roots located in the dural sac results in a polyradicular symptomatology clinically diagnosed as cauda equina syndrome. The cauda equina nerve roots provide the sensory and motor innervation of most of the lower extremities, the pelvic floor and the sphincters. Therefore, in a fully developed cauda equina syndrome, multiple signs of sensory disorders may appear. These disorders include low-back pain, saddle anesthesia, bilateral sciatica, then motor weakness of the lower extremities or chronic paraplegia and, bladder dysfunction. Multiple etiologies can cause the cauda equina syndrome. Among them, non-neoplastic compressive etiologies such as herniated lumbosacral discs and spinal stenosis and spinal neoplasms play a significant role in the development of the cauda equina syndrome. Non-compressive etiologies of the cauda equina syndrome include ischemic insults, inflammatory conditions, spinal arachnoiditis and other infectious etiologies. The use of canine, porcine and rat models mimicking the cauda equina syndrome enabled discovery of the effects of the compression on nerve root neural and vascular anatomy, the impairment of impulse propagation and the changes of the neurotransmitters in the spinal cord after compression of cauda equina. The involvement of intrinsic spinal cord neurons in the compression-induced cauda equina syndrome includes anterograde, retrograde and transneuronal degeneration in the lumbosacral segments. Prominent changes of NADPH diaphorase exhibiting, Fos-like immunoreactive and heat shock protein HSP72 were detected in the lumbosacral segments in a short-and long-lasting compression of the cauda equina in the dog. Developments in the diagnosis and treatment of patients with back pain, sciatica and with a herniated lumbar disc are mentioned, including many treatment options available.

Lipid-free versus lipid-bound P2 protein-induced experimental allergic neuritis: clinicopathological, neurophysiological, and immunological study

The P2 protein of the peripheral nervous system myelin is a neuritogenic protein capable of inducing experimental allergic neuritis (EAN) in the Lewis rat. It has been suggested that the addition of some lipids to the protein isolated in the lipid-free form might enhance its immunogenicity. In this study, we compared lipid-free P2 (the EAN factor) and the corresponding lipid-bound form of the protein regarding their ability to induce EAN. Lipid-bound P2, copurified with all the myelin lipids, shows a conformation different from that of LF-P2. The timing of disease and the clinical scores of lipid-bound P2-induced EAN animals (n = 23) did not differ statistically from those injected with lipid-free P2 (n = 23), with only a tendency to higher clinical severity in the former group. Tail nerve conduction velocities did not differ in the two groups and in both were significantly lower in comparison to Freund adjuvant controls (n = 8). Inflammation and demyelination predominated in the spinal roots and were less evident in the sciatic nerve for both groups of animals. The ELISA determination of antibodies to lipid-free and lipid-bound P2 revealed the development of antibodies recognizing the lipid-free form of the protein in both groups of animals. Our results stand in contrast to results of previous studies performed after addition of exogenous lipids to the P2 purified in the lipid-free form and indicate that lipid-bound P2 is not significantly more immunogenic than lipid-depleted P2.

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.

Human autoimmune neuropathies

Peripheral nerve diseases are among the most prevalent disorders of the nervous system. Because of the accessibility of the peripheral nervous system (PNS) to direct physiological and pathological study, neuropathies have traditionally played a unique role in developing our understanding of basic mechanism of nervous system injury and repair. At present they are providing new insight into the mechanisms of immune injury to the nervous system. A rapidly growing catalogue of PNS disorders are now suspected to be immune-mediated, and in the best understood of these disorders, the molecular and cellular targets of immune attack are known, and the pathophysiology follows directly from the specific immune injury. This review summarizes the immunologically relevant features of the PNS, then considers selected immune-mediated neuropathies, focusing on pathogenetic mechanisms. Finally, the PNS is providing a testing ground for new immunotherapies and approaches to protection and regeneration, including the use of trophic factors. The current status of treatment and implications for future approaches is reviewed.

Effects of phospholipase A2 on lumbar nerve root structure and function

STUDY DESIGN

To investigate the effects of phospholipase A2 on the neurophysiology and histology of rat lumbar spinal nerves and the corresponding behavioral changes.

OBJECTIVES

To study possible mechanisms of sciatica.

SUMMARY OF BACKGROUND DATA

The pathophysiology of sciatica is uncertain, although mechanical, chemical, and ischemic factors have been proposed.

METHODS

Phospholipase A2 was injected into the rat L4-L5 epidural space, and the rats were observed for 3 or 21 days. Behavioral studies were conducted daily during the survival period. On the 3rd or 21st day, extracellular nerve recordings were made from dorsal roots, to determine discharge properties and mechanical sensitivity. The nerve roots were then sectioned for a light-microscopic examination.

RESULTS

Motor weakness of hind limbs and altered sensation were observed. In the 3-day phospholipase A2 groups, squeezing the dorsal roots at the L4-L5 disc level (force = 0.8 g) evoked sustained ectopic discharge that lasted approximately 8 minutes. Squeezing the roots distal to the L4-L5 area did not result in sustained discharges. In sham, control, and 21-day phospholipase A2 groups, squeezing the dorsal roots elicited only a transient firing that lasted approximately 0.1 second. Loss of myelin was seen in the nerve root cross sections in the 3-day group, and remyelination was observed in the 21-day group. No abnormality was found in the control groups.

CONCLUSIONS

Based on these studies, it is hypothesized that phospholipase A2 causes demyelination that results in hypersensitive regions where ectopic discharge may be elicited by mechanical stimulation. These ectopic discharges may be a source of sciatica. We believe that, as long as these irritating factors are present, the hypersensitive nerve root nerve will continue to fire, and sciatic pain will persist.

Post-infectious encephalitis with anti-galactocerebroside antibody subsequent to Mycoplasma pneumoniae infection

Galactocerebroside (Gc) is a major component of myelin in both the peripheral and central nervous systems. Although it is regarded as an important glycolipid hapten of myelin in rabbit experimental allergic neuritis (EAN), its role in human demyelinating diseases is not known. We studied three post-infectious encephalitis (PIE) patients related to Mycoplasma pneumoniae infection. All three of three patients with encephalitis and M. pneumoniae infection were positive for Gc antibodies (100%), while 25% of 32 M. pneumoniae-infected patients without neurological disease were positive, and 3.8% of 52 healthy controls. This indicates anti-Gc antibody is induced by M. pneumoniae infection. One of the PIE patients, who had extraordinary high titer antibody to Gc, showed an extensive, diffuse white matter demyelination and poor recovery. Since circulating anti-Gc antibody induces central nervous system demyelination in animals with elevated antibody titers and disruption of the blood-brain barrier, anti-Gc antibody may have an important function in the increased demyelination in PIE patients after M. pneumoniae infection.

Ultrastructural changes in spinal nerve roots induced by autologous nucleus pulposus

STUDY DESIGN

Ultrastructural changes were analyzed by transmission electron microscopy in nerve roots exposed to autologous nucleus pulposus experimentally.

OBJECTIVES

To assess if ultrastructural changes were present in areas with no light microscopic changes in nerve roots exposed to autologous nucleus pulposus in a pig model.

SUMMARY OF BACKGROUND DATA

Previous analyses have shown that there is focal nerve fiber damage in nerve roots exposed to autologous nucleus pulposus in the pig. These changes could not fully explain the reduction in nerve conduction velocity seen in the same nerve roots. In the present study, the parts of the nerve roots that did not display breakdown of axons or myelin sheaths at the light microscopic level were analyzed regarding ultrastructural changes.

METHODS

In a previous study, nucleus pulposus was harvested from a lumbar disc and placed epidurally onto the cauda equina at the sacrococcygeal level in pigs. Retroperitoneal fat was used as control. After 1, 3, and 7 days, the nerve roots were excised and processed for light microscopy. Parts of the nerve roots that appeared normal at the light microscopic level were further processed for the present electron microscopic examination.

RESULTS

Significant ultrastructural changes, such as expansion of the Schwann cell cytoplasm and intracellular edema with vesicular swelling of the Schmidt-Lanterman incisures, were observed in nerve fibers with normal axons. Although present after nucleus pulposus and control application, the changes were more pronounced after the application of nucleus pulposus.

CONCLUSIONS

Epidural application of autologous nucleus pulposus without any pressure may induce not only nerve function impairment but also axonal injury and significant primary Schwann cell damage with vesicular swelling of Schmidt-Lanterman incisures. However, because axonal and Schwann cell changes affected only part of the nerve fibers, further causes of the impaired nerve conduction need to be determined.

Complement depletion affects demyelination and inflammation in experimental allergic neuritis

The effect of systemic complement depletion by cobra venom factor (CVF) on experimental allergic neuritis (EAN) was studied in rats immunized with variable amounts of bovine peripheral nerve myelin. Low-dose myelin EAN rats treated with CVF i.p. (n = 10) had lower clinical scores (0.3 +/- 0.7 vs. 1.1 +/- 1.1), less demyelination (0.4 +/- 0.8 vs. 1.9 +/- 1.1) and inflammation (0.6 +/- 1.2 vs. 2 +/- 1) than EAN animals treated with i.p. saline (n = 10). Endoneurial infiltrates had fewer ED1-positive (phagocytic) macrophages (0.4 +/- 0.5 vs. 1.6 +/- 1.1) and CD11bc-positive (expressing iC3b receptor or CR3) cells (1 +/- 0.8 vs. 2.5 +/- 0.8) (mean +/- S.D.) detected by immunocytochemistry. This effect was partially abrogated by immunizing animals with a higher dose of myelin. Our studies suggest that complement may play a role in the recruitment of macrophages into the endoneurium and in opsonizing myelin for phagocytosis.

The beta 2-adrenergic agonist terbutaline suppresses experimental allergic neuritis in Lewis rats

Treatment of rats with experimental allergic neuritis with the beta 2-adrenergic agonist terbutaline suppresses clinical symptoms, decreases demyelination and Wallerian degeneration in peripheral nerves and improves electrophysiological parameters. Treatment is highly effective when given from the time of immunization through the acute phase of illness, when given for the first 12 days after immunization and also when given after the onset of the disease.

Transfer of experimental allergic neuritis by intra neural injection of sensitized lymphocytes

The final mediators of immune injury in EAN were investigated by intraneural injection of sensitized lymphocytes. Unfractionated specifically sensitized cells caused conduction block which was evident within 24 h after injection, reached significance within 3 days and remained depressed for over 12 days. Pathological changes at the site of injection showed infiltrating lymphoid and mononuclear cells and significant demyelination. The latter was only evident several days after the electrophysiological changes. These effects were shown to be specific, as injection of LNC from normal rats or those immunized with CFA alone did not induce the changes. Fractionation of sensitized LNC into the CD4+ and CD8+ subsets of T-cells showed only the former caused a drop in the amplitude ratio of nerve conduction. These changes in conduction were comparable to those observed in rats immunized with myelin/CFA to induce active EAN. Cyclosporin A (CSA) was given to host animals to block production of cytokines by the injected cells. This inhibited macrophage accumulation at the site of injection, but did not stop the electrophysiological changes. This result suggested that there was direct T-cell damage rather than damage consequent upon macrophage activation. These studies developed a model in which the cellular and molecular mechanisms of conduction block and demyelination in EAN can be studied by direct injection of specifically sensitized LNC.

Antigalactocerebroside antibody increases demyelination in adoptive transfer experimental allergic neuritis

There is suggestive but inconclusive evidence for a contribution of T cells and antimyelin antibodies to the pathogenesis of the Guillain-Barré polyneuropathy. We have studied the potential synergism of cellular and humoral immunity in the adoptive transfer model of EAN. EAN was induced in Lewis rats by injecting varying doses of P2 peptide (SP26)-sensitized T lymphocytes. Disease severity was dose-dependent. The addition of intravenous GC-AB to a subclinical dose of SP26-sensitized T cells resulted in overt clinical disease and markedly enhanced demyelination. Intravenous injection of antibody alone had no effect. We conclude that activated neuritogenic T cells, while entering into peripheral nerves, alter the blood-nerve barrier, which gives circulating demyelinating antibodies access to the endoneurium. The observations support the concept of a synergistic role of T-cell autoimmunity and humoral responses in the inflammatory demyelination of Lewis rat EAN.

Peripheral nervous system demyelination from systemic transfer of experimental allergic neuritis serum

The ability of systemically transferred experimental allergic neuritis (EAN) serum to produce EAN lesions in recipient animals was studied. Seventeen Lewis rats received five daily 1-ml intraperitoneal (i.p.) injections of sera from rabbits with EAN induced with bovine myelin/complete Freund's adjuvant (CFA). Another 17 rats received similar injections of sera from rabbits inoculated with CFA alone. On day 0 (the first day of i.p. injections), all rats were injected in the proximal tibial branch of the right sciatic nerve with a single 10-microliters injection of 0.03 M 5-hydroxytryptamine (5-HT) in sterile 0.15 M saline. Proximal tibial branches of left sciatic nerves received similar single injections of saline alone. Animals were then studied using electrophysiological and histological techniques. In all animals, intraneural saline injection had no significant effect upon nerve conduction. In the presence of circulating CFA serum, 5-HT injection caused a mild gradual decrease in amplitude ratio becoming maximal by day 17 (P < 0.005) and partially resolving by day 28. In contrast, in the presence of circulating EAN serum, 5-HT injection caused a more rapid and severe decrease in amplitude ratio becoming maximal by days 6-10 (P < 0.001 day 6; P < 0.0001 day 10) and completely resolving by day 28. Histological analysis of nerves injected with 5-HT in CFA serum-treated animals showed areas of mild demyelination, axonal degeneration and some fibre loss consistent with needle trauma. In contrast, 5-HT-injected nerves in animals administered EAN serum showed areas of marked cellular infiltration and severe demyelination in association with numerous debris-filled infiltrating cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of A23187 in cultures containing only rat Schwann cells and sensory neurons

Serum from approximately 40% of patients with the acute Guillain-Barré syndrome (GBS) selectively destroys myelin and myelin-related Schwann cells in cultures containing only rat dorsal root ganglion neurons and Schwann cells. To determine if the effects of GBS serum on myelin and myelin-related Schwann cells could be mediated through elevations in the intracellular concentration of calcium ions, we compared the effects of cytotoxic serum to A23187, a divalent cation ionophore. Both myelin- and nonmyelin-related Schwann cells were killed along with neurons in the presence of A23187 and extracellular calcium ions. Myelin sheaths also underwent vesicular disruption. The ultrastructural appearance of myelin and myelin-related Schwann cell lysis caused by A23187 were essentially identical to damage produced by GBS serum. These observations suggest that GBS serum factors might damage myelin and myelin-related Schwann cells in culture by an increase in myelin-related Schwann cell permeability to extracellular calcium ions. In contrast, A23187 causes necrosis of Schwann cells and neurons as well as myelin lysis by a nonselective increase in membrane permeability to extracellular calcium ions.

IgG immunoadsorption in experimental allergic neuritis: effect on antibody levels and clinical course

The effect of IgG immunoadsorption upon the course of chronic experimental allergic neuritis (EAN) is described. Miniature membrane plasma separators coupled with a Protein A (PA)-Sepharose immunoadsorbent column were used to perform upon conscious rabbits 5 IgG immunoadsorption treatments over 6 days. Quantitation of anti-myelin IgG and IgM by ELISA revealed that 55-65% of plasma IgG was removed per treatment. Rapid post-treatment antibody rebound was observed for anti-myelin IgG although no antibody overshoot above control levels could be observed. Anti-myelin IgM levels remained relatively unaffected by PA immunoadsorption. Comparisons of clinical scores between control and treatment animals showed that IgG immunoadsorption was significantly beneficial (day 1 post-treatment p less than 0.001; day 2 post-treatment p less than 0.05). However, rapid relapse was observed in all treatment animals such that by day 3 post-treatment no significant clinical difference between control and treatment groups could be observed. IgG immunoadsorption suppresses the clinical progression of chronic EAN in a manner similar to that seen with plasma exchange. This finding suggests that antibody modulates early disease pathogenesis.

A fulminant case of Guillain-Barré syndrome: topographic and fibre size related analysis of demyelinating changes

In a necropsy case of early fulminant Guillain-Barré syndrome, demyelinating changes were observed throughout the peripheral nervous system, most conspicuous in the spinal nerve roots. The central/peripheral nervous system transition regions and most proximal zones of the roots escaped damage. In some root areas there were widespread early changes in myelin sheaths in the absence of significant infiltrates of inflammatory cells. In the fibre size analytical study, small myelinated fibres were preferentially involved.

Demyelination induced by intraneural injection of human antimyelin-associated glycoprotein antibodies

IgM monoclonal antibodies present in the sera from some patients with peripheral neuropathy react with an antigenic carbohydrate determinant that is present on the myelin-associated glycoprotein (MAG) and other peripheral nerve glycoproteins and glycolipids. It is generally believed that the neuropathy in these patients may be caused by antibody- mediated nerve damage. Intraneural injection of serum from patients with this disease produced an extensive inflammatory, macrophage-mediated demyelination of feline peripheral nerve. This only occurred with very fresh sera which had been supplemented with additional complement. Injection of sera from normal subjects failed to produce any demyelination. These results are in accordance with a recent study by Hays et al. and contradict earlier negative reports of similar studies. It is important to note that the pathology observed in these experimental studies bears little resemblance to that seen in the human neuropathy, and caution must therefore be exercised when interpreting this data in relation to the pathogenic mechanisms that might operate in the human disease.

Guillain-Barré syndrome and serum activities of gamma-glutamyltransferase and glutamic-pyruvic transaminase

Objective laboratory indicators of alcohol consumption (mean corpuscular volume and serum glutamic-pyruvic transaminase (GPT), glutamyltransferase (gamma-GT), and glutamic-oxaloacetic transaminase (GOT] were measured in 18 patients with Guillain-Barré syndrome (GBS) and 710 control patients. All of the indicators examined were more frequently found to be pathological in GBS patients, reaching significance for gamma-GT and GPT. Some explanations for this result are discussed. It is concluded that alcohol consumption may be a risk factor for GBS.

A prospective study of acute idiopathic neuropathy. III. Immunological studies

The immune responses of 100 patients who presented with an acute idiopathic neuropathy were compared with those of age and sex matched controls. Blood lymphocytes and their subsets were counted with a fluorescent activated cell sorter. CD8+ (putative suppressor) lymphocytes were significantly reduced in the first week of the disease but total lymphocytes, total T and CD4+ (putative helper) cells were not altered. This reduction depended on the nature of the preceding infection. Serum complement C3 and C4 concentrations remained normal and immune complexes were rarely detected with a C1q binding assay. Complement-fixing antibodies to human peripheral nerve antigens were discovered in the serum of 7% of patients but only 1% of controls. Complement-fixing antibodies to galactocerebroside were not discovered in any sera. Enzyme-linked immunoassays detected increased antibody responses to galactocerebroside but none at all to human P2 myelin protein in the patient sera. Forty microliter of serum from five patients injected into the sciatic nerves of rats did not induce significantly more demyelination than the serum from control patients. It is concluded that auto-immune responses can only be detected by these techniques in a small minority of patients with acute idiopathic neuropathy.

Peripheral demyelination and remyelination initiated by the calcium-selective ionophore ionomycin: in vivo observations

Incubation of nerve with Ca2+ and the divalent cation ionophores A23187 or ionomycin, causes a prompt vesiculation of the myelin at the paranodes and Schmidt-Lanterman incisures. The vesiculation appears to be dependent upon a rise in the intracellular calcium concentration of the affected Schwann cells. To determine whether a similar vesiculation might occur in vivo, and to examine the long term consequences of ionophore exposure, the sciatic nerves of rats and mice were injected with ionomycin and examined histologically after intervals of 1 h to 75 days. A prompt myelin vesiculation was again observed, and this spread from the paranodes and incisures to invade regions of formerly compact myelin: segmentally demyelinated axons were common 7 days post-injection. The lesions were large, and involved up to 95% of the fibres in the mouse. There was little evidence of either Schwann cell necrosis, or axonal degeneration in either species. The appearance and spatio-temporal progression of the lesion was strikingly similar to that seen after the intraneural injection of lysophosphatidylcholine or phospholipase A2. However, in the ionophore lesion, not all the demyelination was effected by myelin vesiculation, for up to 30% of the affected fibres showed evidence of macrophage-mediated stripping. Macrophage stripping was confined to internodes already affected by vesiculation. Most of the myelin debris was removed by macrophages, and myelin debris was only rarely observed within Schwann cells. Remyelination was initiated in nearly all the affected fibres by 21 days, and by 2 months all affected fibres were invested with thin, new myelin sheaths. These findings may be relevant to immune-mediated demyelination in the peripheral nervous system.

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).

Complement depletion suppresses Lewis rat experimental allergic neuritis

Lewis rats immunized with myelin and complete Freund's adjuvant were treated with cobra venom factor (CVF) which depletes the C3 component of complement. CVF given at day 9 delayed the onset of experimental allergic neuritis (EAN) by 2-3 days and when given at days 9 and 12 delayed the onset of EAN by 4-5 days. Lumbar nerve roots of CVF-treated rats had significantly less demyelination than those from control EAN rats.

Demyelination in vivo by Guillain-Barré syndrome and other human serum

Serum from patients with acute inflammatory polyneuropathy (the Guillain-Barré syndrome, GBS) demyelinates peripheral nerves in vivo more intensely than control human serum. To clarify the processes leading to demyelination we injected rat sciatic nerves with serum from GBS and control subjects in the presence of complement and examined the sequential morphologic changes over 7 days. One day after injection, five of six GBS sera but none of seven control sera caused vesicular demyelination; 3-5 days after injection both GBS and control sera produced macrophage-mediated demyelination. These observations suggest that GBS serum can initiate acute myelin injury through a humoral mechanism that is disease associated. This response appears to be distinct from delayed cell-mediated serum-induced demyelination that is not disease specific.

An X-ray diffraction study of changes in myelin structure during experimental allergic neuritis

In order to determine whether the structure of the myelin membranes is modified during experimental allergic neuritis (EAN), we have performed X-ray diffraction studies of in vivo and of isolated sciatic nerves from Lewis rats exposed to different EAN-producing treatments. We have observed a decrease of the intensities in the X-ray reflections without changes in spatial resolution. The level of decrease correlated with the severity of the demyelinating lesions. In comparison to nerves from normal healthy rats the electron density profile of sciatic nerve myelin from animals in acute stages of EAN showed small differences at both cytoplasmic and extracellular spaces of the myelin membrane. Dynamic X-ray diffraction patterns recorded kinetically in vivo from a nerve injected intraneurally with a neuritogenic antiserum do not show additional reflections characteristic of a distinct lattice of increased periodicity, suggesting that the early stages of demyelination do not involve an intermediate ordered state.

Role of nonspecific myelin destruction by delayed type hypersensitivity in primary demyelination

To clarify the role of nonspecific myelin destruction mediated by delayed type hypersensitivity (DTH) in primary demyelination, DTH to tuberculin was induced within the endoneurium by intraneural injection of purified protein derivative (PPD) or sonicated Mycobacterium tuberculosis into the sciatic nerves of Lewis rats and guinea pigs which had previously been sensitized to tuberculin. The morphological features of the nerves proximal to the site of needle insertion were assessed 5 days after injection. By changing the PPD concentration of solution for intraneural injection, various degrees of DTH reaction could be produced in the nerve. Infiltration of mononuclear cells including macrophages was observed around the vessels and in the vicinity of the myelin sheaths. Although nonspecific damage of axons, myelin sheaths and Schwann cells was observed in areas heavily infiltrated with inflammatory cells, primary demyelination was hardly recognized. Another group of Lewis rats previously immunized with galactocerebroside (GC), the major glycolipid hapten of myelin, in Freund's complete adjuvant received intraneural injection of PPD or GC liposomes. Neither cellular nor humoral immunity to GC was detected in these rats. The nerves injected with GC liposomes showed no inflammatory cell infiltration except for a few macrophages containing liposomes and those injected with PPD showed infiltration of mononuclear cells without primary demyelination. Our findings reveal that nonspecific myelin destruction induced by DTH does not play an important role in immune-mediated demyelination.

Plasma exchange in chronic inflammatory demyelinating polyradiculoneuropathy

Plasma exchange has been reported to be efficacious in chronic inflammatory demyelinating polyradiculoneuropathy. We performed a prospective double-blind trial in which patients with static or worsening disease were randomly assigned to plasma exchange (n = 15) or to sham exchange (n = 14) for three weeks. After three weeks, we observed statistically significant differences in combined measurements of nerve conduction (total, motor, proximal, velocity, and amplitude) favoring patients who had received plasma exchange. Improvement to a greater degree than for any patient receiving sham exchange was detected in the neurologic-disability score in five patients (P = 0.025) and in subset scores for weakness and reflex in four patients (P less than 0.057). We conclude that for some patients with chronic inflammatory demyelinating polyradiculoneuropathy, plasma exchange has an ameliorating effect on neurologic dysfunction and nerve conduction, but in others no improvement is observed. Because plasma was replaced with normal serum albumin, a humoral factor or factors may have a role in the neurologic deficit of this disorder.

Relapsing inflammatory demyelinating polyneuropathy in a diabetic patient

Inflammatory demyelinating polyradiculoneuropathies exhibit well-known ultrastructural lesions of the peripheral nerve, both in acute cases, i.e., Guillain-Barré syndrome, and in relapsing, sub-acute and chronic cases. We present a case of relapsing inflammatory demyelinating polyradiculoneuropathy in a diabetic patient with a biopsy exhibiting these lesions, as well as a widening of the outermost myelin lamellae in some fibers. Such associated lesions are classic in experimental inflammatory demyelinating polyradiculoneuropathies, but have not been reported in human pathology.

Autonomic dysfunction in experimental allergic neuritis

Beat-to-beat variation (R-R variation) in the electrocardiogram was studied in experimental allergic neuritis in the Sprague-Dawley rat. Reduced R-R variations were found in 2 of 10 animals, probably as a sign of autonomic dysfunction. The vagal nerves from these two animals, studied in vitro, showed disturbed conduction. In one animal prolonged conduction latencies to supramaximal electrical stimuli were found. Vagal nerves from controls and from animals without clinical symptoms showed normal conduction. Histologically, the vagal nerves from affected animals showed a slight inflammatory cell infiltration and signs of demyelination but there was no evidence of involvement of the brainstem vasomotor nuclei. Thus, we suggest that the autonomic dysfunction in experimental allergic neuritis, measured as reduced R-R variations, is caused by a peripheral vagal neuropathy.

Ethylene oxide polyneuropathy: clinical follow-up study with morphometric and electron microscopic findings in a sural nerve biopsy

A case is reported of ethylene oxide polyneuropathy after 5 months of exposure. There was symmetrical distal weakness of both lower extremities and transitory reduced nerve conduction velocities with increased latencies. Sural nerve biopsy revealed nerve fibre degeneration of the Wallerian type, associated with reduction of axonal cross-sectional areas and some degree of nerve fibre regeneration that could be confirmed morphometrically. In addition, there was conspicuous paranodal vesicular disintegration of individual myelin lamellae. Unusual cisternae with introverted hemidesmosomes were noted in endoneurial fibroblasts.

Autonomic nerves in experimental allergic neuritis in the rat

After experimental allergic neuritis (EAN) was induced in 16 male Lewis rats with bovine peripheral myelin and adjuvants, peripheral nerves were examined morphologically at intervals of 12-21 days post inoculation (dpi). Signs of motor involvement were present in ten rats and were first elicited 12 dpi. They ranged from tail droop to complete lower limb paralysis. Autonomic nervous system (ANS) involvement was studied by contrasting morphological findings in the cervical sympathetic nerves (CSN), which are poorly myelinated and vagal nerves (VN) which contain numerous myelinated fibers in the endoneurium. Edema, perivenular infiltrates, and demyelination appeared in the VN of seven of nine neurologically affected rats, while the CSN showed edema and infiltrates in only one rat. ELISA assays were negative for anti-galactocerebroside antibody, and electron microscopy failed to show abnormalities of Schwann cells.

Plasma exchange and prednisone in acute inflammatory polyradiculoneuropathy: a controlled randomized trial

A controlled-randomized trial of plasma exchange combined with prednisone was compared to supportive care alone in patients with acute inflammatory polyradiculoneuropathy (AIP). The design of this study differs from other reported trials of plasma exchange in AIP because prednisone was used in the treatment group to prevent the possibility of antibody rebound. Furthermore, in this study, detailed muscle strength testing formed the principal basis for assessment of therapeutic efficacy while in the British, North American, and French studies, a functional assessment scale was used. Analysis of our data revealed no significant improvement in the treated group over the controls. The sample size, albeit small (12 treated and 13 controls), had the power (95% chance) to detect a change of two British Medical Research Council grades of strength between the groups. The difference in our results versus others (North American and French studies) probably reflects the adverse effects of prednisone on recovery in AIP. An additional consideration is that plasma exchange may have an overall modest effect on the course of AIP, less appreciated when individual muscles are tested compared to assessment by large functional categories.

Acute inflammatory demyelinating polyneuropathy in a diabetic patient: predominance of vesicular disruption in myelin sheaths

A diabetic woman underwent an incision of the right big toe for an abscess and developed a typical Guillain-Barré syndrome 48 h later. A biopsy of a peripheral nerve, performed 10 days later, showed modifications usually seen in diabetic patients, as well as the characteristic ultrastructural modifications of the Guillain-Barré syndrome (GBS). Moreover, 22% of myelinated fibers exhibited vesicular disruption of the myelin sheaths. This lesion is rarely encountered on the biopsies of peripheral nerve in GBS and concerns only a few myelinated fibers. Such a prominence of myelinic vesicular disruption and its occurrence in a diabetic patient are discussed.

Blood-nerve barrier studies in experimental allergic neuritis

The integrity of the blood-nerve barrier (BNB) was studied during the development of experimental allergic neuritis (EAN). Lewis rats immunized with bovine nerve or myelin plus complete Freund's adjuvant developed histological lesions of EAN in nerve roots by 10-12 days and in sciatic nerves by 12-14 days. Evans blue-albumin (EBA) and horseradish peroxidase (HRP) were injected i.v. 1 h prior to killing on days 6-18. Perivascular and diffuse endoneurial leakage of the tracers was seen in nerve roots by 10-12 days post immunization (p.i.) and in sciatic nerves by 12-14 days. This coincided with the appearance of endoneurial infiltration with inflammatory cells and endoneurial proteinaceous edema at a time when Schwann cell and myelin changes were still minimal. Therefore, an alteration in BNB permeability occurs early in EAN, coincident with inflammatory cell infiltration. This could be an expression of delayed hypersensitivity, yet it would also facilitate the entry of anti-myelin antibodies into the endoneurium where they could initiate demyelination.

Acute canine idiopathic polyneuropathy (ACIP) serum demyelinates peripheral nerve in vivo

We examined the in vivo demyelinating activity of serum from dogs with acute canine idiopathic polyneuropathy (ACIP), a Guillain-Barré syndrome (GBS)-like illness. Sera from 6 ACIP cases demyelinated rat sciatic nerves more intensely than 11 control sera. Serum activity increased after guinea pig serum (gps) was added, although gps alone had little effect. ACIP sera did not bind more to whole nerve cross sections or Schwann cells in vitro than control sera, and did not contain elevated antigalactocerebroside titers. We do not as yet know the pathogenic importance of the demyelinating factor in ACIP and control dog serum, or understand its relationship to the demyelinating constituent in serum from humans with GBS.

Abnormal serum factors in Guillain-Barré syndrome

The Guillain-Barré Syndrome (GBS) is generally considered to be a cell-mediated immunopathologic disease of the peripheral nervous system (PNS), although the evidence for this is indirect. Both in vitro and in vivo studies of sera from experimental animals with autoimmune demyelinating neuropathies suggest that serum factors, including antibodies to PNS myelin and/or Schwann cells, may be important in the pathogenesis of some of these disorders. More recently, similar in vitro and in vivo techniques, including the production of demyelination following intraneural injection in the rat have been employed to study sera from patients with GBS. The results of these studies demonstrate the presence of factor(s), as yet not fully characterized, that may be important in mediating demyelination. Moreover, in some patients with chronic or relapsing demyelinative inflammatory neuropathies and monoclonal gammopathy, there is evidence of antimyelin antibodies to PNS myelin. Further studies of serum from patients with acute GBS and these other neuropathies may clarify the role of serum factors in acquired inflammatory diseases of the PNS.

In vivo demyelinating activity of sera from animals with chronic experimental allergic encephalomyelitis. Antibody nature of the demyelinating factor and the role of complement

Sera from guinea pigs and rats with chronic experimental allergic encephalomyelitis were injected into the cerebrospinal fluid (CSF) of normal recipient rats. Guinea pig sera induced demyelination in the central and (or) peripheral nervous system, whereas injection of rat sera resulted in demyelination in the peripheral nervous system only. Control sera did not induce demyelination. Demyelinating activity in guinea pig sera was confined to the IgG-fraction; in rat sera the IgG- as well as the IgM-fraction were able to induce demyelination. The demyelinating activity was abolished when the sera were absorbed with with sensitising antigen (guinea pig spinal cord tissue) or when immunoglobulins were removed from the sera. When chronic EAE sera from rats were injected into the CSF of rats, complement was not required for the induction of demyeLination. The presence of complement, however, augmented the demyelinating activity. Decomplemented chronic EAE sera from guinea pigs failed to induce demyelination after injection into the CSF of rats. Injection of control and non-demyelinating or demyelinating EAE sera into the subarachnoid space of normal recipient rats induced a weak inflammatory response with increased numbers of large mononuclear cells in the meninges. It is discussed that in vivo a complex interaction of antibodies, complement and effector cells is responsible for induction of demyelination.

51Cr release cytotoxicity radioimmunoassay to detect immune cytotoxic reactions to rat Schwann cells in vitro

Monolayers of rat Schwann cells incubated with 51Cr were used as targets for a cytotoxicity assay employing rabbit antiserum to galactocerebroside (R anti-GalC). Specific 51Cr release was demonstrated which was heat sensitive and complement-dependent. The assay was readily performed, reproducible and quantitative, and should prove useful in assessing anti-Schwann cell cytotoxic activity of experimental and human serum.

Nerve fibres in spinal cord impact injuries. Part 1. Changes in the myelin sheath during the initial 5 weeks

The spinal cords of cats were subjected to an impact injury using a "weight dropping" technique and sequential changes in the sheaths of non-degenerate myelinated fibres studied over a 3-week period. By 1 1/2 h after impact fibres showed retraction of some lateral loops from one paranode. The extent and severity of this change increased over the first week so that partial and full thickness demyelination were seen frequently. Partial demyelination most commonly resulted from the internodal termination of the innermost lamellae at an internodal location often associated with a Schmidt-Lantermann incisure. Remyelination by both Schwann cells and oligodendroglia occurred at the end of the second week. Oligodendroglial myelin showed many features of immaturity, similar to those found during development. It is suggested that the very earliest myelin damage is mechanical but is aggravated by other factor(s) one of which is probably ischaemia. Within the most severely injured areas there is death of oligodendroglia and any surviving axons are remyelinated principally by Schwann cells. In intermediate and minimally damaged areas of white matter oligodendroglial remyelination predominates.

Intraneural injection of lymphocytes in experimental allergic neuritis

Passive transfer of experimental allergic neuritis (EAN) lymph node cells (LNC) by intraneural injection did not produce significant demyelination. EAN-LNC stimulated with myelin in vitro produced mild demyelination while those incubated with Concanavalin A had no effect. The lack of demyelination by unstimulated EAN-LNC is in contrast to the marked demyelination produced by intraneural injection of EAN serum. The mononuclear cell infiltration and demyelination of classical EAN seem to require both cellular and humoral immune responses.

The treatment of inflammatory polyneuropathy by plasma exchange

Observations are reported on six patients with inflammatory polyneuropathy who were treated by plasma exchange. In four cases the polyneuropathy was acute and in two it was chronic or relapsing. Two acute cases and one chronic relapsing case had plasma exchange during a rapidly progressive phase of the disease, and showed a prompt and substantial recovery of function. The other three patients were exchanged when disease activity had reached a plateau. Only minor degrees of improvement were seen in two of these cases. One patient showed an initial mild deterioration before subsequent recovery. There were no significant side effects. These findings are discussed in relation to the pathogenesis and clinical management of inflammatory polyneuropathy.

Acute conduction block associated with experimental antiserum-mediated demyelination of peripheral nerve

Intraneural injection of antisera from rabbits with high antigalactocerebroside antibody levels into rat sciatic nerve produced acute nerve conduction block. This was first apparent in some motor axons between 30 and 60 minutes after injection and progressed to completion within 2 to 4 hours. Concurrent morphological evidence of demyelination was present, but structural changes at the time of onset of block were mild and were restricted to the myelin and Schwann cell, particularly at the paranodal areas and Schmidt-Lanterman clefts. It is suggested that paranodal lesions could account for the observed conduction block.

In vivo demyelinating activity of sera from patients with Guillain-Barré syndrome

The in vivo demyelinating capacity of sera from 27 patients with Guillain-Barré syndrome (GBS) and 47 other individuals was studied by intraneural injection into rat sciatic nerves. The morphological features of the nerves in cross section taken just proximal to the site of needle insertion was assessed 48 hours after injection and the extent of demyelination was quantitated. All 27 GBS serum samples were obtained in the first three weeks of clinical disease. Of these, 11 (41%) produced demyelination. Demyelinative activity of GBS sera correlated only with severity of clinical disease (p less than 0.01). The extent of demyelination after intraneural injection of human sera was less intense on average than that produced by sera from animals with experimental allergic neuritis. Three of 40 (7.5%) sera obtained from normal subjects and patients with other neurological diseases also caused in vivo demyelination, although the activity was weaker and occurred less often than with GBS serum.