Chemical analysis of organotypic cultures of mouse spinal cord in normal, demyelinative, and nondemyelinative conditions

Interaction between Gonadal Steroids and Neuroimmune System in Acute Experimental Autoimmune Encephalomyelitis (EAE) in Wistar Rats

Experimental autoimmune encephalomyelitis (EAE) is an inflammatory disease of the CNS mediated by autoreactive T lymphocytes directed against myelin antigens. Since neuroendocrine-immune dysfunction appears to contribute to the pathogenesis of autoimmune diseases, the present work was designed to study the effect of changes in the endocrine system on the development of acute EAE and the immune response against myelin basic protein (MBP). Intact and sham males and intact female Wistar rats showed the most severe clinical symptoms (acute period) 12-14 days post-inoculation (dpi). Then, they began gradually to recover, regaining the total ability to walk by 15-17 dpi. Male Wistar rats with altered levels of gonadal hormones by surgical castration showed an onset of the symptoms retarded 2-3 days with respect to the other EAE groups, showing neuropathological symptoms up to 27-28 dpi, and remaining with lower body weight even at 40 dpi. The castrated animals exhibited a specific delay in MBP-stimulated DTH reactivity that correlates with the delay in the onset of the clinical symptoms. Also significant lymphocyte proliferation to MBP was still present at 35 dpi that was absent in the sham group. The distribution of the IgG subclasses indicated that at 35 dpi castrated animals have a higher IgG2b/IgG1 ratio (35.1) in comparison to that presented by sham rats (4.8). Considering that at this time the castrated animals were not completely recuperated, these results could indicate an ongoing inflammatory immune response associated with Th1 activity in these animals. Also castrated animals developed antibodies to a diversity of MBP epitopes in comparison to sham rats, which presented a dominance of antibodies to MBP peptide p96-128. These results indicate that sex hormones levels regulate cell-mediated immunity and the specificity of anti-MBP antibodies related to the induction and development of acute EAE.

Age-related changes in the development of experimental autoimmune encephalomyelitis

A prominent feature of multiple sclerosis is its high incidence of onset in the third decade of life and its relatively rare onset in persons older than 50 years. In order to study age-related restriction of clinical expression, a comparative biochemical, immunological and histological study was undertaken during development of experimental autoimmune encephalomyelitis (EAE) in young (7 weeks) and middle-aged (15 months) Wistar rats. Young rats showed characteristic clinical signs 12-16 days postinduction, and then they spontaneously recuperated. In middle-aged rats, the incidence of clinical signs was significantly reduced, with a later onset of the disease. Similar biochemical and histological alterations were detected in both age groups, but they were present in a later stage in middle-aged animals. However, cellular and humoral immune responses to myelin basic protein (MBP) were observed 15 days postinduction in all EAE animals. The study of anti-MBP IgG isotype pattern in 7-week-old animals indicated a predominant Th1-type immune response during the acute stage of EAE, with antibodies predominantly recognizing the MBP 96-128 peptide. In contrast, 15-month-old animals showed a less prominent Th1 response, without any epitope dominance. The changes in immune function found in middle-aged animals may account for the different susceptibility and expression of EAE, and may also be relevant to the different clinical expression observed in multiple sclerosis with maturation.

Passive transfer of experimental autoimmune encephalomyelitis in Wistar rats: dissociation of clinical symptoms and biochemical alterations

We have used passive transfer of myelin-reactive lymphocytes in the Wistar rat model of experimental autoimmune encephalomyelitis (EAE) to investigate the nature of the central nervous system immunopathological alterations induced by these cells. Mononuclear cells from lymph nodes or spleen from sick myelin/complete Freund's adjuvant-immunized donors did not transfer clinical disease. However, depending on the previous treatment of the transferred cells, recipients develop central nervous system biochemical and histological alterations. Fresh cells from lymph nodes immediately transferred after procurement from the sick EAE donor rat were capable of inducing the most significant diminution in the content of myelin basic protein, sulfatides, and 2',3'-cyclic nucleotide-3'-phosphohydrolase activity, with concomitant inflammatory infiltrations of white matter, principally in spinal cord and cerebellar lobules. Similar alterations were observed when animals were injected with spleen mononuclear cells activated in the presence of a nonspecific mitogen as concanavalin A. However, antigen-specific activated spleen cells generated by culturing in the presence of bovine myelin induced alterations to a lesser degree. Results point to a dissociation of the clinical disease from the central nervous system biochemical and histopathological lesions occurring in the EAE-transferred Wistar rats and indicate that these alterations in EAE are induced principally by T cells activated in vivo rather than by cells activated in vitro by myelin antigens. Therefore, these findings suggest a possible participation of lymphocytes unlike the encephalitogenic T cells in the induction of the described alterations and provide a useful model to explore further the subclinical responses to this experimental disease.

Humoral response against myelin antigens in two strains of rats with different susceptibility to experimental allergic encephalomyelitis (EAE)

Lewis (Lw) rats are susceptible and Wistar (Wr) rats are usually resistant to the induction of experimental allergic encephalomyelitis (EAE). In this study we analyze the humoral response to myelin antigens, providing evidence for different B cell response to myelin basic protein (MBP) and other myelin proteins between these two strains of rats with different susceptibility to EAE. In fact, IgG anti-MBP titers in Wr rats were markedly higher than in Lw ones. Moreover, an inverse relationship between the amount of antigen injected to induced EAE and the level of anti-MBP antibodies was observed in Wr rats, while IgG anti-MBP varied in a positive dose-depending manner in sera from Lw rats. Also, sera from Wr rats analyzed by immunoblotting showed a strong reactivity with MBP and other myelin proteins, but sera from Lw rats reacted only with MBP. Evaluation of IgA and IgM against MBP in Wr rats showed again higher titers of these isotypes when compared with the titers observed in Lw rats. The distribution of IgG subclasses in sera from both strains indicated that Wr produced low titers of specific IgG1, while Lw rats did not produce specific IgG1. However, Wr rats showed high levels of IgG2a, IgG2b and IgG2c subclasses while lesser titers of these isotypes were observed in Lw animals. These findings indicate that both strains have the capacity to develop antibodies against portions of the MBP molecule, but antibody production is greater in the resistant Wistar rats suggesting a B cell activation in these animals, that could be related to their lower susceptibility.

Peritoneal antigen-presenting cells pulsed in vivo with myelin basic protein induce the suppression of experimental autoimmune encephalomyelitis (EAE) in Wistar rats

Suppression of Experimental Autoimmune Encephalomyelitis (EAE) can be achieved by i.p. administration of soluble myelin basic protein (MBP) in adult Wistar rats before the immunization. In the present work, we analyze the role of peritoneal antigen-presenting cells (APC) in the induction of tolerance to EAE. Peritoneal cells (PC) pulsed in vivo with MBP were obtained from rats that had been intraperitoneally injected 2 h previously with soluble MBP (MBP-PC) and then inoculated in recipient rats before the induction of EAE. Our findings show that the i.p. treatment of the animals with MBP-PC before the immunization was able to diminish the incidence and severity of the disease, reduce the histological alterations, abrogate the proliferative response against MBP and change the pattern of the humoral response to MBP. Moreover, when spleen mononuclear cells (MNC) from tolerant animals were cultured together with spleen MNC from sick animals, a dose-dependent inhibition of the proliferative response was observed, arguing for the presence of a regulatory cell population in the tolerant animals. It is also demonstrated that the MBP-PC are activated and their capability of inducing suppression of EAE is highly associated with the enhanced expression of MHC class II IA molecule. Our results show that peritoneal cells pulsed in vivo with MBP are able to induce tolerance and suggest that the up-regulation of MHC class II on MBP-PC is a necessary event for tolerance induction in our model.

Chronic varied stress modulates experimental autoimmune encephalomyelitis in Wistar rats

Stress disturbs homeostasis by altering the equilibrium of various hormones which have a significant impact on immune responses. Few studies have examined the influence of stressors on autoimmune disease in animal models. In our work, we studied the effects of long-term exposure (14 days) to chronic varied stress (CVS) in a model of experimental autoimmune encephalomyelitis (EAE) in Wistar rats. We studied whether the exposure to CVS before or after the immune challenge would correlate with differences in the clinical course of the disease. We also examined whether the CVS would modulate the magnitude of the cellular or the humoral immune response. We observed opposite effects on the clinical signs in animals stressed before or after the immune challenge. The clinical signs of the disease were attenuated in animals stressed before but not after the immune challenge. Relationships were found in the modulation of the clinical severity related to the time of exposure to the CVS, the histological alterations and the proliferative results. Stressed animals with milder clinical signs presented an exacerbated humoral response against myelin antigens while stressed animals with more severe clinical symptoms exhibited a significantly diminished one. Besides, we detected the presence of specific IgG1 associated with the exposure to CVS before the induction of EAE. Our results show that, depending on the timing of the exposure of Wistar rats to the CVS, the neuroendocrine disbalance favors a more pronounced humoral or cellular profile of the response.

Suppression of experimental autoimmune encephalomyelitis (EAE) by intraperitoneal administration of soluble myelin antigens in Wistar rats

Intraperitoneal (i.p.) treatment of Wistar rats with bovine myelin (BM) or myelin basic protein (MBP) previously to immunization with BM-CFA showed a diminished incidence and severity of experimental autoimmune encephalomyelitis (EAE) (2/13 and 0/7, respectively) when compared with rats immunized with BM-CFA (11/17) or i.p. treated with ovalbumin (2/4). Concomitantly, animals treated with BM or MBP exhibited a marked reduction of proliferative response to MBP which was highly positive when spleen mononuclear cells from nontreated and ovalbumin treated animals were assayed. Rats that were treated with MBP before immunization produce IgA, IgM, total IgG and subclasses of IgG, IgG2a, IgG2b, IgG2c specific for MBP in similar levels than those observed in nontreated immunized animals. However, a higher incidence and level of IgG1 was observed in MBP treated rats, meanwhile rats i.p. treated with total BM showed a highly reduced humoral response. The herein presented results show that i.p. treatment with low amounts of soluble forms of myelin antigens markedly reduced the clinical symptoms of the disease, the histological alterations, the cellular proliferative response to MBP, and produced changes in the autoimmune humoral response.

Time course of biochemical and immunohistological alterations during experimental allergic encephalomyelitis

A comprehensive biochemical, immunological and histological study was undertaken during different stages of experimental allergic encephalomyelitis (EAE). Wistar rats with EAE induced by sensitization with bovine myelin showed a maximum decrease of body weight 14-16 days post-inoculation (dpi), coincident with the appearance of the paralysis symptom (acute period). Quantitation of some brain components indicated a temporal dissociation among the alterations observed. The higher diminution of myelin basic protein (MBP) occurred at 6 dpi and then increased to reach 21 dpi, a normal value. Also, the activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase was reduced by 40% with respect to control animals only at 6 dpi. The total lipid content was normal; however, among the individual lipids, sulfatides were principally degraded during the acute stage but the amount of cerebrosides was decreased during the recovery period (29-40 dpi). Free cholesterol was similar in both groups of animals, whereas cholesterol esters were detected in EAE animals from 14 to 40 dpi. Central nervous system meningeal and parenchymal infiltration with mononuclear cells was recognized principally at 14 dpi, but some of cells were still present at 40 dpi. Deposits of immunoglobulins in the infiltrated regions as well as in spinal cord motor neurons were observed among 14-29 dpi. Total circulating antibodies to MBP began to increase at 14 dpi, reaching a plateau at 21 dpi and then maintaining this value until 40 dpi. However, the population of anti-MBP antibodies that also recognizes the neuronal protein synapsin was only present at 14 dpi. The present results suggest that the neurological symptoms can be related to some early changes in the myelin membrane followed by alterations involving neuronal structures. The existence of immunological factors against some epitopes in MBP that also recognize a synaptosomal protein might account, at least in part, for the axonal damage and disruption of the normal interneuronal activity in EAE and lead together with the alterations in some specific myelin constituents and the concomitant CNS inflammatory process to the observed hindlimb paralysis.

Experimental autoimmune encephalomyelitis: antigen-induced inhibition of biochemical and immunohistological alterations

A comprehensive biochemical, immunological, and histological study was undertaken during suppression of experimental autoimmune encephalomyelitis (EAE) induced by antigen-specific inhibition of the immune response. Pretreatment of Wistar rats by intraperitoneal administration of low doses of saline-soluble bovine myelin or myelin basic protein (MBP) but not with ovalbumin suppresses the appearance of the clinical symptoms of EAE induced by sensitization with bovine myelin in complete Freund's adjuvant. Analysis of the central nervous system (CNS) of animals pretreated with MBP or whole myelin shows inhibition of the diminution of MBP and 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) activity observed in the EAE animals or in rats pretreated with ovalbumin. With respect to the CNS lipid content, these suppressive treatments abolish the increase in esterified cholesterol and partially revert the diminution in the content of cerebrosides and total cholesterol characteristic of the acute stage of the disease. Concomitantly, meningeal and parenchymal infiltration with mononuclear cells and deposits of immunoglobulins in the infiltrated regions as well as in spinal cord motor neurons were reduced. Analysis of the humoral response to myelin antigens shows that all EAE as well as treated animals developed antibodies to MBP and other myelin proteins. However, a higher incidence and level of these antibodies was observed in nontreated EAE animals and MBP- and ovalbumin-treated rats, while rats treated with total bovine myelin showed a highly reduced humoral response. The present results indicate that intraperitoneal treatment with soluble forms of myelin antigens, concomitant with the suppression of the clinical symptoms of the disease, markedly reduces the biochemical and histological alterations occurring in EAE animals and produces changes in the autoimmune humoral response.

Experimental allergic encephalomyelitis: characterization of T lymphocytes that bind myelin basic protein and synapsin

The immuno phenotypic profile of the mononuclear cells that bind myelin basic protein (MBP) and synapsin was investigated in lymph node cells from rats with experimental allergic encephalomyelitis induced by injection with MBP. Using a double immunofluorescent labeling technique, purified cells that bind one or both antigens were analyzed in different stages of the disease. The total MBP-bound lymphocytes increased at 14 days post-inoculation (dpi), had a CD4+/CD8+ ratio of two and were present until 29 dpi. Conversely, the apportionment of cells specific for MBP that also recognize synapsin reached a maximum value at 14 dpi coincidentally with the expression of the paralysis symptoms and then, they disappeared when the animal began to recover. This population amounted to about 40% of the total lymph node MBP-bound cells and had a CD4+/CD8+ ratio of one, indicating that the lymphocytes with MBP-synapsin crossreactivity could be principally implicated in a cytotoxic or suppressor activity.

Insulin-like growth factor I increases myelination and inhibits demyelination in cultured organotypic nerve tissue

The implication of insulin-like growth factor I (IGF-I) in the myelination and the repair of myelin that occur after a demyelinating process was evaluated in organotypic cultures of embryonic nerve tissue. The amount of myelin of mouse spinal cord explants exposed to media supplemented with IGF-I beginning on the first day of explantation was recorded by light-microscopic examination and quantitation of the 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) activity. After 9 days in vitro (DIV), the cultures treated with medium supplemented with 0.1-1 microgram/ml IGF-I showed a greater amount of myelin and an increase over the controls in CNPase activity between 50 and 80% at 16 DIV and 100% at 21 DIV. Total demyelination with a concomitant reduction of about 80% in the CNPase activity resulted when anti-white matter antiserum and complement were added to the nutrient medium of fully myelinated cultures. This effect was partially reverted when IGF-I was included in the demyelinating medium. The higher inhibition, about 50%, was obtained with concentrations of IGF-I between 0.1 and 0.5 micrograms/ml. To study the effect of IGF-I on remyelination, well-myelinated cultures were completely demyelinated, maintained in that state for 2 or 15 DIV and after that allowed to remyelinate for 14 days. Cultures exposed to medium supplemented with 0.01-0.1 microgram/ml IGF-I showed a degree of remyelination similar to that of the normal nutrient medium-fed cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification as synapsin of a synaptosomal protein immunoreacting with anti-myelin basic protein antiserum

Rat brain proteins able to react with anti-myelin basic protein antiserum, raised under conditions to induce experimental allergic encephalomyelitis in rabbits, were examined by immunoblot methods after sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Apart from the four forms of myelin basic protein present in rat brain, the antiserum detected other proteins of higher molecular weight. Subcellular fractionation shows that these high-molecular-weight proteins are relatively concentrated in a synaptosome-enriched fraction compared to a myelin fraction. A major protein fraction immunorelated to myelin basic protein migrated in the gels as a doublet with apparent molecular weights of approximately 80K and 86K; these proteins were tentatively identified as synapsin Ia and Ib. A purified synapsin preparation analyzed by immunoblot after two-dimensional gel electrophoresis also reacted with anti-myelin basic protein antisera. When the serum was purified by affinity chromatography on a myelin basic protein-conjugated Sepharose column the nonadsorbed material lost this activity whereas the eluted antibodies reacted with myelin basic protein and synapsin. In addition, sequence amino acid comparison of decapeptides showed some homology between these two proteins. A possible implication of immunological agents against myelin basic protein cross-reacting with extra-myelin proteins in the process of experimental allergic encephalomyelitis is considered.

An in vitro micromethod for the quantitative assessment of central demyelination

We report the development of a simple and reliable method for the study of demyelination in vitro based on the measurement of 2':3'-cyclic nucleotide 3'-phosphodiesterase in isolated myelin. Using only small quantities of myelin (equivalent to 100 micrograms of myelin protein) the system was tested under conditions that are believed to approximate those found at the site of an inflammatory demyelinating lesion. Treatment with a combination of trypsin, phospholipase A2, and lysophosphatidylcholine was used to evaluate the method. This microsystem has the potential not only for testing the myelinotoxicity of soluble factors but also for investigating the involvement of inflammatory cells in the demyelinating process. Myelin degradation by elicited peritoneal macrophages could be demonstrated at relatively high densities of these cells. Nylon wool purified lymph node T cells from myelin basic protein-primed SJL/J mice, after selective expansion with antigen and interleukin 2, failed to induce any significant myelin breakdown unless a limited number of syngeneic activated macrophages were also present. T cells from mice that had been inoculated with keyhole limpet haemocyanin failed to show any effect. The advantages of this technique over other in vitro systems are that it enables the study of demyelination using syngeneic sources of myelin and defined cell populations.

Effect of antiglycolipid antisera on the lipid composition of cultured mouse spinal cords

To examine the effect of antiglycolipid antibodies on demyelination, myelinated cultures of embryonic mouse spinal cords were treated by antigalactocerebroside (anti-GC), anti-GM1; and anti-GM4 antisera, and the lipid composition of the cultures were studied. The anti-GC antiserum-treated cultures, which exhibited severe morphologic signs of demyelination, revealed a significant reduction of cerebroside. The anti-GM4 or anti-GM1 antiserum-treated cultures, which exhibited mild degrees of demyelination, also had low contents of cerebroside. These results support our previous data showing that antiglycolipid antibodies cause demyelination in cultured mouse spinal cords, and suggest a possible role of myelin-specific glycolipids in the demyelination process.

Quantitation of myelination and demyelination by the measurement of myelin basic protein by ELISA

Utilizing a competitive inhibition enzyme-linked immunosorbent assay (ELISA) we measured the amount of myelin basic protein (MBP) in brain, liver, and kidney of newborn mouse and compared these values with myelinated cerebellar explant cultures under various conditions. Explant cultures demyelinated with anti-myelin serum showed a 90% decrease in MBP when compared with controls. These results correlated with myelination and demyelination as observed by light microscopy. Newborn tissues including brain showed only negligible activity for MBP. This technique provides a sensitive and objective method for quantitating in-vitro demyelination.

The interaction of myelin basic protein with tubulin and the inhibition of tubulin carboxypeptidase activity

Tubulin carboxypeptidase was found to be inhibited by myelin basic protein in a concentration dependent manner. The inhibition was produced by the interaction between myelin basic protein with the substrate. As a consequence of this interaction, turbid insoluble aggregates were formed at either 5 degrees or 37 degrees C. The turbidity increased by increasing the myelin basic protein concentration and it reached a plateau at a molar ratio of myelin basic protein to tubulin dimer of about 6. At plateau, the molar ration in the insoluble aggregates was about 6. When tubulin was in excess, the formation of the insoluble aggregates was diminished. However, if the excess of tubulin was added after the formation of the aggregates, the turbidity was not significantly affected. Turbidity was diminished by increasing the ionic strength.

Effect of insulin, proinsulin and pancreatic extract on myelination and remyelination in organotypic nerve tissue in culture

The effect of insulin, proinsulin and crude pancreatic extract was studied in organotypic nerve tissue cultures, principally in relation to the development of myelin. Cultures were exposed to media supplemented with these substances beginning on the first day of explantation. By 4 days in vitro, there was a good neuritic outgrowth from all the fragments. That from the insulin and pancreatic extract-fed were more profuse and extended further than from the control group. By 8-12 days in vitro it was also possible to observe more myelinated axons in these treated groups. The pattern of changes in the myelin associated enzyme activity, 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) paralleled the differential increase in myelination. Insulin-fed cultures showed a more rapid increase in CNPase activity, which, after 21 days in vitro reached a plateau about 30-50% over that of the controls. Cultures treated with pancreatic extract showed a similar pattern of increased activity, while in proinsulin-treated explants the activity was only significantly higher after 21 days in vitro. To study the effect of these substances on remyelination, well myelinated cultures were completely demyelinated by exposure to anti-white matter antiserum and were subsequently exposed to the same normal control or supplemented media. The amount of myelin and concomitantly the CNPase activity increased rapidly and in the same proportion between the various groups as was observed previously during primary myelination. Insulin as well as crude pancreatic extract and, to some extent, proinsulin demonstrated a marked effect on the time of onset and principally on the total amount of myelin developed by treated cultures as compared to those maintained in normal nutrient medium.

Antisera to different glycolipids induce myelin alterations in mouse spinal cord tissue cultures

To study the demyelinative effects of antibodies to glycolipids, well-myelinated cultures of mouse spinal cord tissue were exposed to antisera against galactocerebroside and two gangliosides (GM1 and GM4), as well as to anti-white matter antiserum. The demyelinative process was evaluated by morphologic and biochemical techniques. Cultures exposed to anti-white matter and anti-galactocerebroside antisera showed the most marked changes. These consisted of a decrease in the number of oligodendroglial cells and dissolution and phagocytosis of myelin. Concomitantly, the activity of 2',3'-cyclic nucleotide-3'-phosphohydrolase (CNPase) was decreased by 60-70%. This occurred within 24 h of exposure to a relatively low concentration of serum (10%). Cultures exposed to anti-GM1 and anti-GM4 antisera showed similar changes but to a lesser degree. The CNPase activity was decreased about 30% within 48 h of exposure to a 25% concentration of these antisera. This diminution represents about a 20% loss of myelin, an observation corroborated by electron microscopy where myelin but not oligodendroglial cell loss was observed. Therefore, in addition to anti-galactocerebroside activity, which was previously found to be the major antibody responsible for the demyelinating activity induced by anti-whole CNS tissue antiserum, these data suggest that antibodies to gangliosides like GM1 and GM4 might also play a role in immune-mediated demyelination, including perhaps, the human demyelinating diseases.

Correlation between 2',3'-cyclic nucleotide 3'-phosphohydrolase activity and demyelination in vitro using a syngeneic system

Cultures of myelinated SJL/J fetal mouse spinal cord were incubated with serum and lymphoid cells from syngeneic animals with experimental allergic encephalomyelitis (EAE) induced by syngeneic spinal cord homogenate (SSCH) in complete Freund's adjuvant or others injected with complete Freund's adjuvant alone. After 24 or 48 h of exposure, demyelination was determined by light microscopic examination and quantification of 2',3'-cyclic nucleotide 3'-phosphohydrolase activity. Cultures exposed to spleen or lymph node cells from SSCH-sensitized animals showed the greatest alterations in myelin and decreases in 2',3'-cyclic nucleotide 3'-phosphohydrolase activity whereas serum from these animals had less effect. Cells and serum from complete Freund's adjuvant-injected control animals also induced structural changes in myelin that were significantly less than changes induced by cells and serum from animals with EAE. These experiments show that lymphoid cells and serum obtained from SJL/J mice with acute EAE affected myelin biochemistry and morphology in syngeneic CNS cultures.

Role of complement in demyelination in vitro by multiple sclerosis serum and other neurological disease sera

Multiple sclerosis (MS) sera can demyelinate and cause selective cellular changes to organ cultures of rodent CNS which suggests possible immunoglobulin involvement. The complement dependence of this serum action was investigated using complement-inactivating agents and radiolabelled rat cerebellar cultures. After heat inactivation at 56 degrees C, the in vitro effects of MS, chronic relapsing experimental allergic encephalomyelitis (cr-EAE) and Guillain-Barré syndrome (GBS) sera were severely reduced or eliminated as measured by radiolabel release. On introducing a source of fresh complement, the cr-EAE and GBS serum effects were largely restored whereas MS serum effects remained suppressed. Inactivation of serum complement with mercaptoethanol and Zymosan was associated with marked reduction in serum myelinotoxicity; some restoration of in vitro effects was possible on adding fresh complement although this occurred to a greater extent with cr-EAE and GBS than with MS sera. Inactivation of the alternative complement pathway brought a limited reduction in MS serum activity in vitro which was not restored with fresh complement. It is concluded that complement is involved only to a limited extent in MS serum myelinotoxic effects and that MS serum effects in vitro are due to several components of which thermolabile substances make a significant contribution and are as yet uncharacterised.

Quantitative chemical analysis of demyelination in cultured mouse spinal cord

These studies were designed to determine whether chemical parameters can be used to quantify the demyelinative potency of anti-CNS sera or other demyelinating factors as revealed by cultured nerve tissue. The activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) and the amount of some major myelin lipids were measured in cultured embryonic mouse spinal cord during different stages of demyelination. Cultures exposed to anti-white matter serum for various times (6-60 h) or various concentrations (2.5-25%) showed a decrease (up to -70%) in CNPase activity. This change paralleled the degree of demyelination as evaluated by light microscopic examination. Cultures exposed to normal rabbit serum under the same conditions did not show changes in the amount of myelin or in the activity of CNPase. Conversely, changes in the lipid content did not correlate with the morphologic evaluation of demyelination. Glycolipids were found to decrease in cultures exposed to anti-white matter as well as in those exposed to normal rabbit sera. The decrease in cerebrosides was higher with anti-white matter serum than with normal serum, but sulfatides were altered in similar amounts in both groups. In contrast, under the same conditions, the amount of total protein or other lipid such as total cholesterol is not altered. Therefore, biochemical analysis of some myelin components could constitute a more sensitive and reliable quantitative method for early evaluation of the time course of demyelination in cultured nerve tissues.