Experimental allergic neuritis in the Lewis rat: characterization of the activity of peripheral myelin and its major basic protein,P2

Peripheral neuropathy and monoclonal IgM with antibody activity against peripheral nerve myelin; effect of plasma exchange

Serum IgM antibodies directed against peripheral nerve myelin were demonstrated using enzyme-linked immunosorbent assay, mixed haemagglutination and indirect immunofluorescence in 3 patients with chronic polyneuropathy and monoclonal serum IgM. Isoelectric focusing followed by antigen immunofixation and autoradiography showed that the antimyelin antibodies co-migrated with the monoclonal IgM. Plasma exchange alone, without chemotherapy, proved beneficial in 2 patients. In one patient, plasma exchange was discontinued because of low IgG levels. Serum IgM and antimyelin antibodies decreased during plasma exchange and no increase beyond initial levels was noted after cessation of treatment.

Macrophage procoagulant activity as a measure of cell-mediated immunity to P2 protein of peripheral nerves in the Guillain-Barré syndrome

Cell-mediated and humoral immunity to purified nerve proteins has been assessed in GBS patients and compared with that of patients with other neurological diseases and healthy controls. A strong and specific cell-mediated response to the neuritogenic basic protein P2 occurred in 13/16 GBS patients tested. Extremely low levels of P2 (0.01 micrograms/culture) induced monocyte/macrophage procoagulant activity (MPCA) on peripheral blood mononuclear cells (PBM) from GBS patients (P = 0.007) whereas higher concentrations (2 micrograms/culture) of myelin basic protein (MBP) and sciatic nerve myelin (SNM) were required to stimulate similar levels of activity. These concentrations of nerve antigens failed to induce significant MPCA on peripheral blood mononuclear cells of patients with other neuropathies or healthy controls. Lipopolysaccharide, a non-specific stimulant of macrophage procoagulant activity, induced similar procoagulant levels on PBM from each group. The MPCA assay was a sensitive, quantitative and specific indicator of cell-mediated immunity to the neuritogenic peptide, P2 in GBS patients. Serum antibodies to P2, P0 and SNM were detected by a sensitive solid-phase radioimmunoassay. Naturally occurring antibodies to peripheral nerve antigens were observed in sera of healthy subjects and these levels were not significantly different from patients with GBS or those with other neuropathies. Our results indicate that the autoimmune cell-mediated response to the neuritogenic peptide P2 plays a major role in the pathogenesis of GBS.

Cerebrospinal fluid immunoglobulin abnormalities in systemic lupus erythematosus

Central nervous system (CNS) involvement is a common and important complication in systemic lupus erythematosus. The mechanisms for CNS involvement are poorly understood and reliable diagnostic procedures are lacking. Pairs of serum and cerebrospinal fluid (CSF) specimens from 17 patients with clinical and serological manifestations of systemic lupus erythematosus were analysed. All 11 patients with definite or suspect clinical CNS disorder revealed some kind of abnormality in the CSF, in contrast to three of seven systemic lupus erythematosus patients without CNS disorder. The most prominent findings in systemic lupus erythematosus patients with CNS disorder were immune aberrations with oligoclonal bands on agarose isoelectric focusing (AIF) and elevation of IgG and IgM index, probably reflecting intrathecal production of IgG and IgM respectively. Intrathecal production of antiviral antibodies was found in four of 12 patients by AIF followed by immunofixation and subsequent autoradiography. An enzyme-linked immunoabsorbent assay (ELISA) could not detect autoantibodies against structural brain antigens.

In vivo treatment of rats with monoclonal anti-T-cell antibodies. Immunohistochemical and functional analysis in normal rats and in experimental allergic neuritis

The effects of intraperitoneal injection of monoclonal anti-rat T-lymphocyte antibodies were evaluated immunohistochemically and functionally in normal rats and in rats with experimental allergic neuritis. In the normal animals a single injection of OX8 antibodies, reactive with suppressor/cytotoxic T cells, completely eliminated OX8-reactive cells from peripheral lymphoid organs and from circulation, whereas the 'pan' T-cell-reactive W3/13 antibodies and the helper T-cell-reactive W3/25 antibodies only caused a partial elimination of their respective target cells. Injection of the W3/13 and W3/25 antibodies but not of OX8 antibodies led to a diminished responsiveness to allogeneic stimulation in vitro for spleen cells obtained from the treated rats, whereas the OX8 injection caused a complete elimination of the in vitro cytotoxic response to allogeneic cells in the mixed lymphocyte reaction-activated spleen cell population. When Lewis rats were injected with peripheral nerve myelin and Freund's adjuvant for the induction of EAN, treatment with W3/13 antibodies completely prevented the onset of disease, whereas treatment with the OX8 antibodies exaggerated the disease symptoms.

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.

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

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

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.

The role of myelin P2 protein in the production of experimental allergic neuritis

Myelin P2 protein has been proposed as the primary antigen in whole myelin-induced experimental allergic neuritis (EAN). We investigated the neuritogenic properties of P2 by sensitizing Lewis rats with complete Freund's adjuvant (CFA) containing P2, P2 plus phosphatidyl serine, or whole myelin containing an equivalent amount of P2. Animals were examined using a battery of clinical, electrophysiological, immunological, and morphological methods. Myelin-immunized rats developed the characteristic features of EAN. P2-sensitized rats developed a similar but much less intense disorder. When rats were sensitized with P2 in the presence of phosphatidyl serine, however, they developed radiculoneuropathy that was indistinguishable from myelin-induced EAN. Inoculation with phosphatidyl serine plus complete Freund's adjuvant or complete Freund's adjuvant alone had no detectable effect on peripheral nerves. These studies demonstrate that sensitization of rats with a single myelin antigen, P2 protein, is sufficient to induce the clinical, electrophysiological, and neuropathological features of EAN.

Dynamics of Ia-expressing cells and T lymphocytes of different subsets during experimental allergic neuritis in Lewis rats

Inflammatory cells were characterized by immunohistochemistry, utilizing monoclonal antibodies against cell surface antigens in frozen sections of sciatic nerves and nerve roots of Lewis rats, sacrificed during the course of experimental allergic neuritis. Large numbers of Ia-expressing irregular macrophage-like/dendritic cells, as well as W 3/13 reactive T lymphocytes of both W 3/25 reactive helper and ox8 reactive suppressor/cytotoxic phenotypes were seen within afflicted peripheral nervous tissue at the start of clinical symptoms and at the height of the disease. T lymphocytes of both helper and suppressor/cytotoxic phenotypes decreased concomitant with clinical recovery. During this period demyelination was still extensive and Ia-expressing macrophage-like/dendritic cells were abundant.

Peripheral nerve P2 basic protein and the Guillain-Barré syndrome. In vitro demonstration of P2-specific antibody-secreting cells

An immune response to the peripheral nerve basic protein P2 may be operative in the pathogenesis of the Guillain-Barré syndrome (GBS). A method is described for the purification of P2 of human origin. Purified P2 was used to investigate whether lymphocytes derived from peripheral blood of GBS patients are capable of producing P2-specific antibodies after stimulation with the antigen in vitro. Peripheral blood lymphocytes (PBL) from 5 GBS patients, from 3 patients with chronic idiopathic polyradiculoneuropathy (CIP) and from 3 normal controls were cultured in vitro in the presence of P2. PBL from the 5 GBS patients were shown to generate an antigen (P2)-specific antibody response. Contrariwise, PBL from the 3 CIP patients as well as from the 3 normal controls did not show this specific response.

Degradation of bovine P2 protein by bovine brain cathepsin D

Bovine brain cathepsin D cleaved bovine P2 protein to produce three major and several minor peptides. The major P2 peptides formed were shown by amino acid analysis and partial sequencing to be peptides 17-54, 20-58 and 65-131 with the latter predominating. In preliminary experiments, P2 peptide 65-131 did not induce experimental allergic neuritis in Lewis rats in equimolar amounts to the neuritogenic P2.

Attempts to transfer experimental allergic neuritis with lymphocytes

Attempts have been made to transfer experimental allergic neuritis (EAN) both by the intraneural and the intravenous injection of cells derived from Lewis rats with the disease into naive recipients of the same strain. Lymph node cells obtained 12 and 15 days after inoculation with bovine dorsal root in Freund's complete adjuvant were injected intraneurally. A small number of demyelinated axons were observed, but clinical weakness was not evident. Lymph node cells, lymph node cells cultured with concanavalin A, or cultured spleen cells from animals with EAN were transferred intravenously to normal rats. Uncultured lymph node cells were transferred to X-irradiated animals. There were no clinical or histological differences between these recipients and controls receiving cells from rats inoculated with Freund's adjuvant alone. The findings are discussed in relation to previous reports of attempts to transmit EAN by cell transfer.

Immune responses to myelin antigens in Guillain-Barré syndrome

Antibodies to nerve antigens were sought in the sera of 17 patients with acute Guillain-Barré syndrome (GBS), 11 with chronic relapsing demyelinating poly-radiculoneuropathy (CRP), 20 with other neuropathies (ON), 15 with other neurological diseases (OND) and 19 normal subjects. Complement-fixing antibodies to a suspension of human peripheral nerve tissue were identified in only 2 patients with GBS and 1 with chronic progressive neuropathy. Five GBS sera gave complement fixation reactions with rabbit sciatic nerve. The sera were also tested for galactocerebroside (Gal-C) binding activity using a solid phase assay. The range of values in all groups was the same, although the mean values for patients with GBS, ON and OND were higher than those of normal subjects. In a radioimmunoassay for antibodies to bovine P2 slightly more radiolabelled antigen was precipitated by the GBS group of sera than by sera from the other groups, but only one serum from the GBS and another from the CRP patients precipitated more than 10% of the label. Addition of bovine P2 to cultures of peripheral blood mononuclear cells from 11 patients with GBS did not cause significant stimulation. Immunoassay for antibody to myelin basic protein (MBP) showed an increased proportion of sera with low binding activity in the GBS and CRP groups. The results suggest that humoral immune responses to potentially neuritogenic antigens are found with marginally increased frequency in patients with GBS and CRP.

IgM and IgG responses during chronic relapsing experimental allergic encephalomyelitis (r-EAE)

During chronic relapsing experimental allergic encephalomyelitis (r-EAE) in guinea pigs, serum IgM and IgG concentrations increased markedly early in disease. Serum IgM and IgG increased similarly in control animals immunized with Freund's incomplete adjuvant (FIA) and Mycobacterium tuberculosis (MT). In the chronic phase of r-EAE but not in control animals, elevated IgM was also found in central nervous system (CNS) extracts, suggesting intrathecal IgM synthesis. IgG antibodies against myelin and myelin basic protein (MBP) were regularly detected in r-EAE sera from day 21 post inoculation (p.i.), reaching maximum levels in the early chronic phase. IgG antibodies against galactocerebroside (GC) and galactose appeared in some r-EAE sera. Oligoclonal IgG bands were demonstrated in all r-EAE guinea pig sera 21-26 days p.i. The bands in serum decreased in number and strength in the chronic phase. They could be traced to antibodies against MT in 4 of 10 animals, but not to antibodies against myelin, MBP, GC or galactose. Oligoclonal IgG bands were also regularly visualized in r-EAE CNS 124 days p.i., suggesting persistent intrathecal IgG synthesis. They varied in number and migration between different regions of individual CNS. Oligoclonal CNS IgG was related to antibodies against MT in only one of 7 animals, and in no case to antibodies against myelin.

Circulating lymphocyte subpopulations in experimental allergic neuritis

T-cell subsets in the peripheral blood were analyzed using monoclonal antibodies during the development of experimental allergic neuritis in Lewis rats. Percentages of helper and suppressor cells and ratios of helper/suppressor cells did not exceed normal limits during the development of the disease.

Spontaneous and experimental neuritis and the distribution of the myelin protein P2 in the nervous system

The P2 contents of nervous tissues from the human, rabbit, guinea pig, and Lewis rat were measured by radioimmunoassay. The ventral spinal roots contained more P2 than any other tissue. Human dorsal roots and peripheral nerves contained 41-65% of the amount in human ventral roots. Human olfactory and optic nerves and brain contained 1.1-2.7%, spinal cord, 2.8%, cranial nerve VIII, 11%, and cerebral grey matter, 0%. The relative amounts in the rabbit nervous system were similar except that the spinal cord contained 20% of the amount in the ventral roots. Qualitative estimates in the guinea pig showed that the spinal roots and peripheral nerves contained more P2 than the spinal cord, and that none was present in the brain. In the Lewis rat, P2 could be detected in the spinal roots and peripheral nerves but not in the CNS. The distribution of P2 in the human nervous system parallels the incidence and severity of lesions in acute polyradiculoneuritis. It also explains the absence of any lesions in the CNS when experimental allergic neuritis is induced in the Lewis rat.

P2 protein-induced experimental allergic neuritis. An ultrastructural study

Experimental allergic neuritis (EAN) was induced in 2 groups of inbred Lewis rats by sensitization with P2 protein and peripheral nervous system (PNS) myelin, both purified from bovine intradural roots. Light- and electronmicroscopic study of P2-induced EAN revealed demyelinative lesions in spinal ganglia and root nerves and less frequently in peripheral nerves and root entry zones. Both small and large myelinated fibers were demyelinated, contradictory to the reported selective binding of anti-P2 antibodies to myelin of large fibers. The early lesions were characterised by perivenular lymphocytic infiltration, and subsequent "dissolution" of myelin sheath was associated with invasive of phagocytic cells. The distribution of demyelinative lesions and patterns of demyelination resembled those of PNS myelin-induced EAN except that the disease was milder and dissolution of myelin and intramyelinic edema were more frequently found in P2-induced EAN. The abundance of demyelination in P2-induced EAN strikes contrast to the scarcity of myelin change in experimental allergic encephalomyelitis (EAE) induced by myelin basic protein immunization.

Ia-expressing cells and T lymphocytes of different subsets in peripheral nerve tissue during experimental allergic neuritis in Lewis rats

Inflammatory infiltrates in sciatic nerves during the acute phase of experimental allergic neuritis in the Lewis rat have been characterized with regard to occurrence and distribution of Ia-expressing cells and T-lymphocyte subsets by the help of an immunohistochemical double-staining technique, enabling the simultaneous visualization of T lymphocytes and Ia-expressing non-T cells. Large numbers of Ia-expressing irregular macrophage-like/dendritic cells were seen both within inflammatory infiltrates and within afflicted nervous tissue. Many W3/13-reactive T lymphocytes of both 'helper' and 'suppressor/cytoxic' phenotypes appeared in close contact with these Ia-expressing non-T cells, particularly within the infiltrates. B lymphocytes and plasma cells were relatively few and mainly found close to endoneurial vessels.

A general model of the P2 protein of peripheral nervous system myelin based on secondary structure predictions, tertiary folding principles, and experimental observations

The amino acid sequence of the P2 protein of peripheral myelin was analyzed with regard to regions of probable alpha-helix, beta-structure, beta-turn, and unordered conformation by means of several algorithms commonly used to predict secondary structure in proteins. Because of the high beta-sheet content and virtual absence of alpha-helix shown by the circular dichroic spectra of the protein, a bias was introduced into the algorithms to favor the beta-structure over the alpha-helical conformation. In order to define those beta-sheet residues that could lie on the external hydrophilic surface of the protein and those that could lie in its hydrophobic interior, the predicted beta-strands were examined for charged and uncharged amino acids located at alternating positions in the sequence. The sequential beta-strands in the predicted secondary structure were then ordered into beta-sheets and aligned according to generally accepted tertiary folding principles and certain chemical properties peculiar to the P2 protein. The general model of the P2 protein that emerged was a "Greek key" beta-barrel, consisting of eight antiparallel beta-strands with a two-stranded ribbon of antiparallel beta-structure emerging from one end. The model has an uncharged, hydrophobic core and a highly hydrophilic surface. The two Cys residues, which form a disulfide, occur in a loop connecting two adjacent antiparallel strands. Two hydrophilic loops, each containing a cluster of acidic residues and a single Phe, protrude from one end of the molecule. The general model is consistent with many of the properties of the actual protein, including the relatively weak nature of its association with myelin lipids and the positions of amino acid substitutions. Alternative beta-strand orderings yield three specific models having different interstrand connections across the barrel ends.

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.

Prevention of experimental allergic neuritis in the Lewis rat with bovine P2 protein

Protective doses of bovine P2 protein (5, 15 or 50 micrograms) in incomplete Freund's adjuvant (IFA) were administered to Lewis rats and were followed 2, 4 or 10 weeks later by challenging doses of either 250 micrograms bovine P2 or 2.5 mg bovine PNS myelin in complete Freund's adjuvant (CFA). Protection from experimental allergic neuritis (EAN) could be achieved with a single dose of 5 micrograms of P2 in IFA. There was little difference between prophylactic 5 micrograms and 15 micrograms doses of P2. The degree of protection depended upon the interval between protective innoculation and challenge. Protection was partial at 2 weeks and maximal at 4 weeks at which time there was complete protection against P2-induced EAN and less complete protection from myelin-induced disease. Complete protection at 4 weeks from myelin-induced EAN was achieved with a 50 micrograms dose. Protection lasted for at least 10 weeks (the longest interval assessed) and was complete with respect to P2-induced EAN. Partial protection was observed in myelin-challenged animals after 10 weeks with the level of protection greater than that observed after 2 weeks.

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.

Experimental autoimmune encephalomyelitis. An anatomically-based explanation of clinical progression in rodents

Lactate accumulation was measured soon after decapitation in three adjacent lower spinal cord regions of rats with EAE. Results indicate that during EAE, and in correlation with the onset of clinical signs of both initial attack and short-term relapse, a differential focal increase in lactate accumulation occurs in rat spinal cord compared to Freund's Complete Adjuvant controls, with greater increase occurring in more caudal segments. A [14C]antipyrine method of estimating relative spinal cord blood flow failed to find evidence that the lactate accumulations were due to focal ischemia. Subsequent measurement of isotopic water and total protein increases in the same cord regions indicated that a slight but significant increase in vasogenic edema occurs in correlation with the increase in lactate accumulation and the onset of EAE clinical signs. The data are interpreted as lending support to a speculative theory of paralysis induced by edema during EAE, in which nerve root endoneurium is postulated as the functionally vulnerable site. More specifically, it is hypothesized that the ascending progression of clinical signs of EAE in rodents can be explained on an anatomical basis by progressive disturbance of the nodes of Ranvier in nerve root myelinated fibers.

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.

The role of macrophages in demyelination in experimental allergic neuritis

The role of macrophages and serum factors in demyelination in experimental allergic neuritis (EAN) was examined by a simple in vitro method. Cultivated rabbit peritoneal macrophages, preincubated with serum obtained from rabbit EAN produced by sensitization with bovine spinal nerve roots, could agglutinate and phagocytize purified bovine or rabbit peripheral nerve myelin. Sera from normal animals or from controls given adjuvant alone could not. Adhesion and phagocytosis were inhibited if EAN sera were absorbed with peripheral nerve myelin. Rabbit red blood cells were not phagocytized by macrophages exposed to EAN serum. Concomitant to these observations, three lysosomal acid hydrolases: acid proteinase, acid phosphatase and beta-glucuronidase, were assayed with respect to their topographical and chronological distribution. In the group examined at clinical onset, increases in the specific activities were 1.5-3.0-fold in the spinal roots and 1.0-1.5-fold in the sciatic nerves compared with control. The degree of increase in total activities per whole root or sciatic nerve was much higher for specific activities. The topographical distribution of the increase closely corresponded to the histological distribution of EAN lesions. These observations suggested that the increased lysosomal activity originated from lysosomal-rich infiltrating cells. These observations strongly indicated the significant role of macrophages activated by EAN serum in the demyelination of EAN.

Inflammatory myopathy: a review of etiologic and pathogenetic factors

Human idiopathic inflammatory myopathy is an acquired disorder with an annual incidence of two to five cases per million. A genetic influence on host susceptibility may also play a role. With the marked heterogeneity of the disease one of the major challenges is to identify subsets that might share a more uniform pathogenesis and manifest a less diverse profile of clinical findings, histopathological abnormalities, and natural history. Dermatomyositis can be distinguished by clinical appearance and pathological changes, but the recognition of additional disease subsets remains very inexact. Current evidence suggests that dermatomyositis occurs as a result of a vasculopathy, but immune mechanisms involved in other categories of idiopathic inflammatory myopathy may also involve cell-mediated immunity and possibly multiple mechanisms. Even though viral-induced muscle inflammation occurs in humans, there is no convincing evidence for a viral cause of idiopathic inflammatory myopathy. Experimental allergic myositis may be produced by the injection of animals with skeletal muscle homogenates and complete Freund's adjuvant, but the myositogenic factor is unknown and the parallels between experimental allergic myositis and human idiopathic inflammatory myopathy are limited.

Demonstration of serum IgG antibodies against myelin during the course of relapsing experimental allergic encephalomyelitis in guinea pigs

Chronic relapsing allergic encephalomyelitis (r-EAE) was induced in a local strain of guinea pigs. By the use of isoelectric focusing (IF) followed by antigen immunofixation and autoradiography, antibodies directed against central nervous system (CNS) myelin were detected in 21 of 23 sera sampled during the course of r-EAE. Previous absorption of the sera with CNS myelin reduced or abolished antibody activity on autoradiograms. One r-EAE guinea pig developed definite oligoclonal IgG bands in serum while in 7 r-EAE animals faint oligoclonal IgG bands were present. The mobility of oligoclonal IgG bands differed from the mobility of antimyelin antibody bands on autoradiograms. The significance of these findings has not been definitely elucidated but the antimyelin antibodies may possibly be involved in the pathogenesis of the disease while oligoclonal IgG bands may represent an epiphenomenon not pathogenetically related to r-EAE.

Immunocytochemical study of the appearance of P2 in developing rat peripheral nerve: comparison with other myelin components

Using indirect immunofluorescence on both dissociated cell cultures and frozen sections from rat sciatic nerve, dorsal root ganglion and superior cervical ganglion, we have examined the development and distribution of the peripheral myelin protein P2. It first appears in development in sciatic nerve and dorsal root ganglion on the first day of birth, at about the same time as P0 and P1. Like galactocerebroside, P0 and P1, P2 disappears gradually from dissociated Schwann cells in culture. In adult sciatic nerve, and dorsal and ventral roots, it shows an uneven distribution and is absent from some myelinated axons. In electron micrographs the onset of myelination in the sciatic nerve occurs between the day of birth (day 0) and the first day after birth (day 1). Immunofluorescence studies on freshly dissociated cell suspensions, frozen sections and dissociated cell cultures at these early time points indicate that the myelin glycolipids galactocerebroside and sulphatide are present on the surface of many schwann cells at least one day before myelination starts while the myelin proteins P0, P1 and P2 are not detected until myelination begins. This suggests that the early appearance of galactocerebroside and sulphatide is an important step preceding the formation of compact myelin.

Antibodies to P2 and P1 myelin antigens in experimental allergic neuritis and allergic encephalomyelitis

We confirmed earlier observations that experimental allergic neuritis (EAN) in Lewis rats induced by injection of bovine peripheral nerve myelin in complete Freund's adjuvant is not accompanied by development of experimental allergic encephalomyelitis. However, sera of these animals contained elevated titers of antibodies against central nervous system myelin basic protein (BP), likely induced by peripheral nerve P1 protein. Anti-BP antibodies were not seen in sera of rats with EAN induced by peripheral nerve P2 protein. Lack of encephalogenicity of bovine myelin in Lewis rats does not reflect simply lack of immune responses induced against BP.

Conformation of bovine nerve root P2 protein: characteristics of the molecule from circular dichroism spectra

Circular dichroism (CD) was used to study the conformations of bovine nerve root P2 basic protein, its reduced and carboxymethylated derivative (RCM-P2), and its large cyanogen bromide fragment (CN1). Data in the far UV show that both the parent protein and RCM-P2 have conformations dominated by a large amount of beta structure. However, the CN1 peptide appears to exist in a largely unordered conformation. Since CN1 lacks short (20 residue) amino- and carboxy-terminal segments of the P2 protein, the spectral data suggest that these regions are important for determining and/or maintaining folding of the P2 protein in aqueous solutions. The P2 protein was found to have a distinctive CD spectrum in the near UV. The characteristics of molar ellipticities indicate that the spectrum contains significant contributions from tyrosine residues, and that these contributions suggest different environments for the two tyrosines in P2 protein. Both environments depend on protein conformation, since CD side chain absorptions are lost when P2 protein is denatured with 5 M urea.

Long term culture of bovine oligodendroglia isolated with a Percoll gradient

Oligodendroglia were isolated from calf central nervous system (CNS) white matter by trypsinization in phosphate buffered saline and separation by centrifugation through Percoll. Using antisera to phenotypic markers and double labelling experiments we were able to identify essentially all cells in the cultures. The cells obtained were: (1) viable; (2) had intact plasma membranes and well preserved organelles, ribosomes and mitochondria; and (3) were greater than or equal to 95% oligodendroglia 16-20 h after isolation as determined by ability to bind antigalactocerebroside antibodies (anti-GalC). Oligodendroglia could be cultured for several weeks to months. Oligodendroglia established and maintained processes which bound anti-GalC. Myelin basic protein could be demonstrated in the cytoplasm of 40-60% of oligodendroglia cell bodies but not in the processes.

The PO protein of chick sciatic nerve myelin: purification and partial characterization

The PO protein of the myelin of chick sciatic nerve was isolated and purified by propanoic acid extraction of peripheral nervous system (PNS) myelin, delipidation, Sepharose CL-6B chromatography in the presence of sodium dodecyl sulfate (SDS), and preparative SDS-polyacrylamide gel electrophoresis (PAGE). Approximately 15% of the PO protein in the sciatic nerve myelin was recovered in a homogeneous state. The purified protein monomer has an apparent molecular weight of 32.1K as determined by gel electrophoresis. The PO protein undergoes extensive aggregation during exhaustive dialysis and freeze-drying and yields stable dimers, trimers, and tetramers. The aggregation of the PO protein after freeze-drying is independent of the presence of a reducing agent (2-mercaptoethanol) in the solubilizing medium. The PO protein is a glycoprotein. The amino acid composition of the chick PO protein indicates a definite species difference when compared with mammalian PO proteins although the NH2-terminal isoleucine residue seems to have been retained during evolution.

Immune responses in experimental allergic neuritis

The antibody and cell mediated immune responses were investigated in inbred Lewis rats with experimental allergic neuritis (EAN) induced by either P2, a protein purified from the bovine cauda equina nerve roots, or whole bovine nerve root myelin. In the P2 immunised animals both antibodies to P2 detected by radioimmunoassay and cell-mediated immunity to P2 assayed by skin testing appeared before the onset of EAN and persisted during and after the disease. In the myelin immunised animals the antibody titres were lower and somewhat delayed and the skin tests became negative at the height of the disease. Complement-fixing antibodies to galactocerebroside, which have been implicated in the production of demyelination under some circumstances, could not be detected in the serum after immunisation with either P2 or myelin. EAN was transferred passively with lymph node cells from rats immunised with either P2 or myelin although anti-P2 antibodies could not be detected in the serum of recipients with EAN. The results favour a cell-mediated immune response to P2 as the most important pathogenetic mechanism in EAN induced wtih whole myelin in the rat.

Degradation of the P0, P1, and Pr proteins in peripheral nervous system myelin by plasmin: implications regarding the role of macrophages in demyelinating diseases

Activated macrophages secrete a variety of neutral proteinases, including plasminogen activator. Since macrophages are implicated in primary demyelination in the peripheral nervous system (PNS) in Guillain-Barré syndrome and experimental allergic neuritis, we have investigated the ability of plasmin and of conditioned media from cultured macrophages, in the presence of plasminogen, to degrade the proteins in bovine and rat PNS myelin. The results indicate that (a) the major glycoprotein P0 and the basic P1 and Pr proteins in PNS myelin are extremely sensitive to plasmin, perhaps more so than is the basic protein in CNS myelin; (b) the initial product of degradation of P0 by plasmin has a molecular weight higher than that of the "X" protein; (c) large degradation products of P0 are relatively insensitive to further degradation; and (d) the neuritogenic P2 protein in PNS myelin is quite resistant to the action of plasmin. Results similar to those with plasmin were obtained with conditioned media from macrophages and macrophage-like cell lines together with plasminogen activator, and the degradation of the PNS myelin proteins, Po and P1, under these conditions was inhibited by p-nitrophenylguanidinobenzoate, an inhibitor of plasmin and plasminogen activator. The results suggest that the macrophage plasminogen activator could participate in inflammatory demyelination in the PNS.

Enrichment of Schwann cell cultures from neonatal rat sciatic nerve by differential adhesion

A novel method of Schwann cell purification from neonatal rat sciatic nerve has been developed using differential adhesion. After enzymatic and mechanical dissociation, the cell digest is allowed to settle on polylysine-coated glass coverslips for 30 min with intermittent shaking. After an 18-h incubation, bipolar cells comprise greater than 95% of the non-adherent population. Indirect immunofluorescence with the cell-specific markers rabbit anti-galactocerebroside and rabbit anti-bovine-P-2 basic protein antiserum confirmed light microscopic identification of these bipolar cells as Schwann cells. Rabbit anti-human fibronectin specifically labeled fibroblasts which comprised less than 5% of the cell population, but did not bind to Schwann cells. Schwann cells isolated by differential adhesion were injected into a rabbit. When absorbed with cultured rat skin fibroblasts, serum from this rabbit specifically surface labeled greater than 99% of the bipolar and round cells after 18 h and 5 days in vitro and also labeled Schwann cells in fetal rat dorsal root ganglia cultures, but not fibroblasts or neurons.

Structure of bovine P2 basic protein: sequence of a carboxyterminal segment that is a neuritogen in rabbits

The sequence of the carboxyterminal 18 amino acids released by cyanogen bromide digestion of the bovine P2 protein was determined. It has several interesting structural and immunological properties. It contains the only two half-cystines in the molecule that have the capacity to form an intrachain disulfide bond. Using the rabbit as a test animal, this carboxyterminal peptide was capable of producing experimental allergic neuritis. The sequence of this peptide is Val-Val-Glu-Cys-Lys-Met-Lys-Asp-Val-Val-Cys-Thr-Arg-Ile-Tyr-Glu-Lys-Val.

Treatment of acute inflammatory polyneuropathy

Most patients with acute inflammatory polyneuropathy (AIP) recover spontaneously, but the time course of the illness is unpredictable so that the results of treatment are difficult to assess. Three decades of retrospective reports of steroid treatment fail to demonstrate any striking beneficial effect. In a randomized trial of prednisolone, starting dose 60 mg daily, 21 treated patients improved more slowly than 19 untreated patients. By contrast, in rats immunized with bovine nerve root myelin, prednisolone at 10 mg/kg reduced the severity and duration of experimental allergic neuritis (EAN), the putative animal model for AIP. This discrepancy might reflect the greater difficulty of clinical as opposed to animal therapeutic trials or indicate that EAN is not the appropriate model for the human disease. Immunosuppressive drugs, plasmapheresis and other agents have also been employed, but their efficacy cannot be decided from the available case report. The role of similar agents in chronic progressive and relapsing inflammatory neuropathy cannot yet be resolved, but in some patients steroids do appear to be valuable.

The protein antigens of peripheral nerve myelin

Peripheral nervous system (PNS) tissue contains a variety of proteins, lipids, and carbohydrates that may serve as immunogens in proving immune responses, as antigens participating in immunological reactions, or as both types of agents. Three proteins P0, P1, and P2, account for approximately 70% of PNS myelin proteins. P0 is the major PNS myelin protein and is restricted to the PNS. P1 is similar to, if not identical with, myelin basic protein, the component of central nervous system myelin which induces experimental allergic encephalomyelitis. P2 has neuritogenic properties for inducing experimental allergic neuritis and may be involved in immune-mediated PNS myelin injury in humans. The complete amino acid sequence for P2 has recently been delineated, and its neuritogenic, immunogenic, and antigenic features can now be further characterized.

The neuritogenicity and encephalitogenicity of P2 in the rat, guinea-pig and rabbit

In inbred Lewis rats, P2 basic protein from bovine peripheral nervous system (PNS) myelin produced experimental allergic neuritis (EAN) without involvement of the brain or spinal cord. In guinea-pigs, bovine P2 did not produce EAN but large doses produced mild experimental allergic encephalomyelitis (EAE). In rabbits, bovine P2 produced both mild EAE and EAN. Human P2 produced severe EAN in the Lewis rat, but only mild EAN with quite marked EAE in the guinea-pig. Material cross-reacting with bovine P on immunodiffusion was identified in the extracts from the nerves of all three species but only in the spinal cord of the guinea-pig and rabbit, not in the rat spinal cord. The species differences in response to immunisation with P2 cannot be simply explained by the presence or absence of P2 in their PNS or CNS, but may reflect differences in the immune response.

Passive transfer of demyelination by experimental allergic neuritis serum

Serum from rabbits with experimental allergic neuritis (EAN) when injected into rat sciatic nerves produced rapidly evolving demyelination followed by remyelination. Myelinating and non-meylinating Schwann cells as well as myelin itself were damaged by 15 min after injection. Myelin degradation was well advanced prior to involvement by macrophages at 12 h. The demyelinating factor was myelin-specific and complement-dependent. The evidence suggests that the EAN antigen may reside in Schwann cell membranes as well as in myelin.