Serum antibodies against glycosphingolipids in chronic relapsing experimental allergic encephalomyelitis. Demonstration by ELISA and relation to serum in vivo demyelinating activity

Structure and Biology of Self Lipid Antigens

Self lipid antigens induce selection and expansion of autoreactive T cells which have a role in immunoregulation and disease pathogenesis. Here we review the important biological rules which determine lipid immunogenicity. The impact of lipid structure, synthesis, traffic, membrane distribution and CD1 loading are discussed.

Serum ganglioside patterns in multiple sclerosis

The relative distribution of gangliosides was determined in the serum of 37 patients with multiple sclerosis (MS) and of 30 healthy subjects. There was a significant increase of GM1 and GD1a, and a decrease of GM3 proportion in the serum of relapsing-remitting MS patients (RRMS) during their first MS attack. The RRMS patients in relapse with a long duration of the disease had a significant decrease of GM1 and an increase of GD1a portion in the serum. An increase of GD1a, one of the major brain neuron ganglioside fraction, suggested the neuron injury in the early and with a long duration RRMS. The finding of an increase of GM1, the main human myelin ganglioside, during the first MS attack in RRMS patients confirms previous evidence for the possible involvement of gangliosides in the early pathological course of demyelination in MS.

The autoimmune reactivity to myelin oligodendrocyte glycoprotein (MOG) in multiple sclerosis is potentially pathogenic: effect of copolymer 1 on MOG-induced disease

Multiple sclerosis (MS), an autoimmune disease of the central nervous system (CNS) characterized by primary demyelination, is believed to result from an autoimmune attack against myelin components. In view of their ability to induce experimental autoimmune encephalomyelitis (EAE), an animal model for MS, the quantitatively major malign proteins--myelin basic protein (MBP) and proteolipid protein (PLP)--have been extensively studied as the relevant primary antigens in MS, and therapeutic approaches have been targeted to counteract autoimmune reactivity to MBP and PLP. Accordingly, copolymer 1, a random synthetic amino acid copolymer crossreactive with MBP and highly protective against the induction of EAE with MBP or PLP, is not being extensively tested in clinical studies as a therapeutic agent for MS. However, increasing evidence suggests that autoimmune reactivity against other CNS-specific myelin proteins could also be involved in the pathogenesis of MS. In this context, we have demonstrated that peripheral blood lymphocytes from patients with MS respond predominantly to myelin oligodendrocyte glycoprotein (MOG) rather than to MBP or PLP, suggesting an important role for cell reactivity against MOG in the pathogenesis of MS. We have demonstrated that T-cell reactivity in MOG can also be pathogenic by inducing neurological disease in H-2u and H-2b mice with the same peptide of MOG, pMOG 35-55. Most interestingly, the expression of the disease differed with the different MHC backgrounds. Induction of a differentially expressed disease in different strains of mice with the same myelin antigen makes this new model particularly relevant to MS, where different expression of the disease is seen in different patients. Therefore, notwithstanding the importance of the autoimmune reactivity to MBP and PLP in MS, the potentially pathogenic autoimmune reactivity to MOG must now also be taken into consideration in therapeutic approaches to MS. In this context, we have investigated the possible effect of copolymer 1 treatment on autoimmune reactivity to MOG and on the development of EAE induced by MOG. Copolymer 1 was found to inhibit the binding of MOG peptides to MHC molecules, as well as the proliferation of MOG-reactive T cells, in a dose-dependent manner. In parallel, injection of copolymer 1 concomitantly with the encephalitogenic MOG peptide exerted a strong protective effect against the development of EAE. These preliminary data on the effect of copolymer 1 on the autoimmune response to MOG in mice indicate that copolymer 1 may also be effective in cases of MS where the autoimmune response to MOG prevails, and should therefore be further investigated in this context.

Factors affecting the fine specificity and sensitivity of serum antiganglioside antibodies in ELISA

The major problem associated with ELISA of serum antiganglioside antibodies is the high background values (absorbancy of sera added to wells without ganglioside), which interfere with the accurate assessment of the fine specificity and sensitivity of these antibodies. This investigation identifies factors elevating the background values and/or decreasing the fine specificity, and describes strategies to minimize their influence. Using sera of neuropathy and melanoma patients, we found that highest background values were observed with the polystyrene 'tissue culture' microtiter plates; of the various 'non-tissue culture' microtiter plates tested, the lowest background values (> 0.060) were observed with Costar-3590 (H), Immunolon-3, Immunolon-1, Falcon-3915 (in increasing order). Background artifact of polystyrene microtest plates was significantly reduced by gamma irradiation (at 40 kRad) and/or use of detergent Tween-20 (0.1%) in the washing step. Even after controlling the background values, the fine specificity, namely, the ability of the antibody to distinguish between the target epitope of an antigen and epitopes of related antigens (when moles of antigen/well is constant) varied with different microtiter plates. Using sera with high affinity and specificity for GM2, GD3 or GM3, we observed that Immunolon-1, Immunolon-3 and particularly Falcon-3915 were superior for assessing the abilities of the antibodies to distinguish closely related epitopes found on other gangliosides. The reactivity of antiganglioside antibodies was more consistent after detergent treatment. The reactivity of antibodies to GD3 is significantly enhanced after treatment with Tween-20, but that of antibodies reacting to GM1 and GM2 is reduced. Fine specificity of the antiglycolipid antibodies was resolved better by coating glycolipids in mol/well rather than by weight/well. Based on these results, a protocol for a sensitive and reproducible ELISA for serum antiganglioside antibodies is recommended. The protocol takes into consideration the suitability of polystyrene plates, coating based on the number of molecules, pertinency of the solvent for coating, use of human serum albumin for blocking, dilution and washing steps and use of 0.1% Tween-20 to further minimize the background absorbancy.

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.

Induction of persistently demyelinated lesions in the rat following the repeated adoptive transfer of encephalitogenic T cells and demyelinating antibody

A chronic relapsing model of demyelinating experimental allergic encephalomyelitis (EAE) was induced in Lewis rats by the repeated co-transfer of encephalitogenic, myelin basic protein (MBP)-specific T cells in combination with a demyelinating monoclonal antibody (mAb) specific for the myelin oligodendrocyte glycoprotein (MOG). In controls, repeated injections of 5 x 10(5) MBP-specific T cells at intervals of 18-21 days resulted in an increasing resistance to the induction of further episodes of EAE. However, intravenous injection of the mAb 4 days after each T cell transfer overcame this 'vaccination' effect and induced severe clinical relapses associated with an increasing and persistent neurological deficit. Histological examination revealed that four cycles of treatment with T cells and mAb were sufficient to result in the formation of large plaques of demyelination in the spinal cord that failed to undergo significant remyelination within 60 days of the final injection of mAb. These lesions consisted of a matrix of astrocytic scar tissue traversed by numerous naked axons. These observations demonstrate that the formation of large, persistently, demyelinated lesions in a T cell-mediated model of EAE in the Lewis rat is dependent on the presence of an appropriate anti-myelin autoantibody response.

Induction of demyelination by intraneural injection of antibodies against sulfoglucuronyl paragloboside

Sulfoglucuronyl glycolipids (SGGLs) carry the glucuronyl 3-sulfate (HNK-1) epitope which is recognized by monoclonal IgM paraproteins from patients with demyelinating polyneuropathy. We report that intraneural injections of rat anti-SGGL antibodies induce demyelination in rat sciatic nerve, along with mild to moderate clinical symptoms. Morphologically, vesiculation and loosening of the myelin sheath were observed 3 h postinjection, followed by extensive demyelination and macrophage infiltration after 4 days. Since the anti-SGGL antibodies showed no cross-reactivity with other components in rat sciatic nerve, these results indicate that SGGLs alone can serve as the target antigens in demyelinating neuropathy.

Demyelination induced in aggregating brain cell cultures by a monoclonal antibody against myelin/oligodendrocyte glycoprotein

A monoclonal antibody (8-18C5) directed against myelin/oligodendrocyte glycoprotein (MOG) induced demyelination in aggregating brain cell cultures. With increasing doses of anti-MOG antibody in the presence of complement, myelin basic protein (MBP) concentration decreased in a dose-related manner. A similar, albeit less pronounced, effect was observed on specific activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase. In the absence of complement, anti-MOG antibody did not induce detectable demyelination. In contrast to the effect of anti-MOG antibody and as expected, anti-MBP antibody did not demyelinate aggregating brain cell cultures in the presence of complement. These results provide additional support to the suggestion that MOG, a quantitatively minor myelin component located on the external side of the myelin membrane, is a good target antigen for antibody-induced demyelination. Indeed, they show that a purified anti-MOG antibody directed against a single epitope on the glycoprotein can produce demyelination, not only in vivo as previously shown, but also in cultures. Such an observation has not been made with polyclonal antisera raised against purified myelin proteins like MBP and proteolipid protein, the major protein components of the myelin membrane, or myelin-associated glycoprotein. These observations may have important implications regarding the possible role of anti-MOG antibodies in demyelinating diseases.

Murine monoclonal anti-myelin basic protein (MBP) antibodies inhibit proliferation and cytotoxicity of MBP-specific human T cell clones

Myelin basic protein (MBP)-specific T cell clones, isolated from two patients with multiple sclerosis, expressed the CD4+ phenotype and induced MBP-dependent cytolysis of autologous Epstein-Barr virus (EBV)-transformed B cells. The proliferation and cytolytic activity of the T cell clones were inhibited by four of a panel of five murine monoclonal anti-MBP antibodies in a dose-dependent manner. An isotype-matched antibody with an irrelevant specificity did not have such an effect. These MBP-specific monoclonal antibodies did not block phytohemagglutinin-induced T cell proliferation or allospecific cytotoxicity. These results suggest that some antibodies directed at the autoantigen MBP may play a regulatory role in T cell activation, rather than a pathogenic role, for which there is currently little supporting evidence.

Identification of a common idiotype on myelin oligodendrocyte glycoprotein-specific autoantibodies in chronic relapsing experimental allergic encephalomyelitis

The myelin/oligodendrocyte glycoprotein (MOG) is a target antigen for autoantibody-mediated demyelination in chronic relapsing experimental allergic encephalomyelitis (CREAE) in the Strain 13 guinea pig. Anti-idiotypic antibodies directed against a demyelinating MOG-specific monoclonal antibody (8-18C5) have identified a cross-reactive idiotype in 10/10 CREAE sera. In nine of these sera inhibition studies demonstrated that this idiotype was at or in close proximity to the combination site of guinea pig anti-MOG autoantibodies. This cross-reactive anti-MOG idiotype may represent an important target for the anti-idiotypic regulation of demyelinating antibody responses in CREAE.

Chronic experimental autoimmune encephalomyelitis in the guinea pig. Presence of anti-M2 antibodies in central nervous system tissue and the possible role of M2 autoantigen in the induction of the disease

Experimental autoimmune encephalomyelitis (EAE) can be transferred adoptively with T cells sensitized to the basic protein of myelin (BP). However, in the guinea pig, the chronic form of EAE has not been found to be inducible with BP alone, nor has it been adoptively transferred. An antibody response to the central nervous system (CNS) myelin autoantigens was looked for in serum and target CNS tissue in S13 guinea pigs with isologous CNS tissue-induced chronic EAE. Antibody activity was estimated by an immunoenzymatic technique and by autoradiography, using immunoprecipitated and electrophoresed relevant radiolabelled antigens. In serum, IgG antibody response to BP and M2 reached its maximum level 30 to 40 d after immunization and then declined progressively until it became undetectable. On the other hand, while anti-BP antibodies were seldom detected in CNS tissue acid extract, anti-M2 IgG antibodies were always present in CNS tissue of chronic EAE animals, and the amount of these antibodies were related to the severity of symptoms and lesions. No antibody response to proteolipid or to galactocerebroside was detected in serum or CNS tissue. BP-immunized controls showed no chronic EAE and no response to M2 in their serum or CNS tissue. Inasmuch as M2 has been shown to be a glycoprotein of CNS myelin, and anti-M2 antibodies to have a demyelinating property, the latter would be responsible for CNS tissue demyelination in chronic EAE. A shared role of BP and M2 in the induction of chronic EAE in the guinea pig is suggested.

Antisera to the ganglioside GM1 do not have anti-myelin or anti-axon activities in vitro

Four antisera to the ganglioside GM1 were tested for effects on myelin and axons when applied to mouse spinal cord-dorsal root ganglia explant cultures. None of the antisera to GM1 caused myelination inhibition or demyelination, while an antiserum to galactocerebroside caused both. Antisera to GM1 did not inhibit axonal outgrowth or destroy mature outgrowth zone axons, while an antiserum to a rat brain axolemma-enriched fraction did both. These results suggest that antibodies to GM1 do not have significant anti-myelin or anti-axon activity.

Monoclonal autoantibodies derived from multiple sclerosis patients and control persons and their reactivities with antigens of the central nervous system

Peripheral blood B lymphocytes of multiple sclerosis (MS) patients and control persons were transformed with Epstein-Barr virus. Antibody production of transformed cells against isolated human myelin was investigated by enzyme-linked immunosorbent assay (ELISA). Cells producing reactive antibodies were cloned and propagated to produce monoclonal antibodies (mAbs). These mAbs did also react with acetone fixed frozen sections of normal human white matter, as determined by indirect immunofluorescence staining. Some of the mAbs derived from MS patients and a control person with a central nervous system cyst agglutinated liposomes made from lipids of a chloroform/methanol extract of human myelin, whereas mAbs derived from four glioma patients were negative in these tests. The reactive antibodies were investigated further using agglutination tests with liposomes made from pure auxiliary lipids (cholesterol and lecithin) or containing in addition either galactocerebroside, sulfatide or a mixture of bovine brain gangliosides. The great majority of myelin liposome agglutinating antibodies reacted with all types of liposomes, including those made from pure auxiliary lipids. Investigations by ELISA suggest that phospholipids are the reactive components, at least for some of these mAbs. Some antibodies reacted with liposomes containing galactocerebroside or sulfatide, others only with sulfatide containing liposomes. Antibodies showing these specificities were only obtained from MS patients.

Autoantibody responses in the cerebrospinal fluid of guinea pigs with chronic relapsing experimental allergic encephalomyelitis

We report the use of the ELISA technique to measure IgG specific for whole cord, myelin, myelin basic protein and Mycobacterium tuberculosis in the cerebrospinal fluid (CSF) of Strain 13 guinea pigs in different stages of chronic relapsing experimental allergic encephalomyelitis (CR-EAE). Specific antibody levels to all 4 antigen preparations were related to the severity of clinical signs, with the highest levels of IgG in the CSF of guinea pigs in relapse or in stable chronic disease. Total IgG levels in the CSF, though elevated throughout the course of CR-EAE, did not show any association with the category of disease. Control animals inoculated with complete Freund's adjuvant (CFA) alone showed CSF IgG levels specific for M. tuberculosis that were not significantly different from those in animals with chronic EAE, indicating that CFA may itself induce a late-acting increase in blood-brain barrier permeability.

Induction of experimental autoimmune encephalomyelitis in guinea pigs using myelin basic protein and myelin glycolipids

Strain 13 guinea pigs were immunized with galactocerebroside, asialo-GM1 (GA1) or GM4 ganglioside in association with myelin basic protein (MBP) in complete Freund's adjuvant (CFA) to produce experimental autoimmune encephalomyelitis (EAE). The clinical and pathological features, serum antibodies, and lipid compositions of affected brains and spinal cords were compared with those of guinea pigs immunized with MBP, in CFA, alone. Perivascular demyelination was seen in brains from all guinea pigs immunized with GA1/MBP. The incidence and degree of demyelination in this group were significantly higher than in the group immunized with only MBP. The onset of EAE was slightly, but significantly, retarded in groups of animals immunized with GM4/MBP and there was no detectable demyelination. Otherwise, no significant differences were detected between groups. Augmentation of EAE by myelin glycolipids may provide some important clues in understanding the mechanism of demyelinating diseases.

A treatable multifocal motor neuropathy with antibodies to GM1 ganglioside

We report 2 patients with a treatable, immune-mediated motor polyneuropathy associated with antibodies to defined neural antigens. In these patients asymmetrical weakness developed in one arm and progressed over 2 to 3 years to involve the other arm, legs, and trunk. Both patients were initially diagnosed as having lower motor neuron forms of amyotrophic lateral sclerosis. However, repeated electrophysiological testing eventually showed multifocal conduction blocks in motor but not sensory fibers compatible with patchy selective demyelination. Serum testing by thin-layer chromatography and enzyme-linked immunosorbent assay revealed that both patients had high titers of antibody directed against GM1 and other gangliosides. Initial therapeutic trials of prednisone (100 mg daily for 4 to 6 months) and plasmapheresis were unsuccessful. Treatment with cyclophosphamide, however, was followed by marked improvement in strength in both patients.

Experimental allergic encephalomyelitis: the balance between encephalitogenic T lymphocytes and demyelinating antibodies determines size and structure of demyelinated lesions

The effect of a circulating monoclonal antibody recognizing an antigen located on the surface of myelin sheaths (myelin/oligodendroglia glycoprotein, MOG) on clinical and histopathological expression of experimental allergic encephalomyelitis (EAE) was tested in a model of EAE passively transferred by monospecific T lymphocytes. Intravenous injection of anti-MOG antibody at the onset of the disease massively augmented clinical impairment as well as primary demyelination. The structure of the CNS lesions depended on the balance between encephalitogenic T cells and anti-MOG antibody: when EAE was induced with high numbers of T cells, circulating anti-MOG antibody resulted in ubiquitous perivenous demyelination in the spinal cord and medulla oblongata. On the contrary, focal confluent demyelinated lesions were observed in animals injected with low numbers of T cells (even as few as 10(4] and anti-MOG antibody. Our studies, thus, indicate that the formation of inflammatory demyelinating lesions may be due to a synergistic action of cellular and humoral immune mechanisms.

Antibody responses in chronic relapsing experimental allergic encephalomyelitis: correlation of serum demyelinating activity with antibody titre to the myelin/oligodendrocyte glycoprotein (MOG)

Antibody responses to the myelin/oligodendrocyte glycoprotein (MOG) and myelin basic protein (MBP) were determined in the sera of Hartley guinea pigs with chronic relapsing experimental allergic encephalomyelitis (CREAE) using an enzyme-linked immunoassay. The sera were also tested for in vivo demyelinating activity by infusion into the subarachnoid space of normal rats. In contrast to the MBP titres, the anti-MOG antibody titres showed good correlation with the in vivo demyelinating activity of the sera (r = 0.91, P less than 0.001). This result suggests that antibodies directed against MOG may be involved in the pathogenesis of demyelination in CREAE.

Anti-myelin antibodies in cerebrospinal fluid and serum of patients with meningopolyneuritis Garin-Bujadoux-Bannwarth and other neurological diseases

Anti-myelin antibodies (AMA) of IgG, IgM, and IgA class were investigated by ELISA in CSF and serum from patients with meningopolyneuritis Garin-Bujadoux-Bannwarth (GBB), other inflammatory diseases of the nervous system (ID) comprising meningoencephalitis (ME), multiple sclerosis (MS), and Guillain-Barré syndrome (GBS), and various noninflammatory neurological diseases (NID). Anti-Borrelia antibodies (ABA) were determined by ELISA in GBB patients. In CSF, a high incidence of IgG-AMA, IgM-AMA, and IgA-AMA was found in GBB as compared with ID and NID. On average, positive AMA titers were higher in GBB than in ID and NID, IgM-AMA titers in GBB being most prominent. In serum, AMA were found in all but 2 patients investigated. On average, IgM-AMA titers were higher in GBB and MS than in other diseases; IgG-AMA titers in GBB and ME were relatively low. Antibody indices, calculated from titer values and Ig concentrations in CSF and serum, indicate intrathecal synthesis mainly of IgG- and IgA-AMA, and of IgG- and IgM-ABA. Participation of AMA in the pathogenesis of GBB may be envisaged, but needs further confirmation.

IgM and IgG antibodies to phenolic glycolipid I from Mycobacterium leprae in leprosy: insight into patient monitoring, erythema nodosum leprosum, and bacillary persistence

Serum IgM and IgG antibodies against Mycobacterium leprae-derived phenolic glycolipid I (PG) were determined in leprosy patients, contacts, and controls by enzyme-linked immunosorbent assay (ELISA). Anti-PG IgM levels increased from the tuberculoid (TT) to the lepromatous (LL) pole of the disease spectrum. There was a positive linear correlation between anti-PG IgM and bacillary index (BI). Patients with erythema nodosum leprosum (ENL) had lower levels of serum anti-PG IgM than non-ENL patients of comparable BI, suggesting that anti-PG IgM is involved in the pathogenesis of ENL. Initial observations indicate that high anti-PG IgM levels in bacillary-negative patients might reflect bacillary persistence. A study of 2 different substrate reagents in the ELISA [2,2'-azino-di(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), 0.1 mM H2O2, serum diluted 1:20, and o-phenylenediamine (OPD), 5 mM H2O2, serum diluted 1:300] showed generally good correlation in detection of anti-PG IgM. However the OPD system detected more paucibacillary disease (BT), while the ABTS system detected the significant effect of ENL on the relationship between BI and anti-PG IgM. Anti-PG IgM was clearly dominant over anti-PG IgG. However, certain patients, including several patients who had upgraded from LL and borderline lepromatous leprosy (BL), showed high levels of anti-PG IgG. Since studies have shown that LL patients are selectively deficient in cell-mediated immunity, T-cell products may be required for the IgM to IgG isotype switch. We conclude that anti-PG IgM is useful for monitoring the bacillary load in individual patients and should prove useful for leprosy control strategies.

Chronic experimental autoimmune encephalomyelitis. Circulating autoantibodies bind predominantly determinants expressed by complexes of basic protein and lipids of myelin

Chronic relapsing experimental autoimmune encephalomyelitis (CREAE) was induced by immunising juvenile strain 13 guinea pigs with homologous spinal cord tissue in adjuvant. Thirteen animals were killed in the early chronic (5-12 weeks post immunisation) and 8 in the late chronic phase (after 15 weeks pi). Plasma titres of antibodies to an isolated myelin preparation were determined by enzyme linked immunoassay. Elevated titres of these antibodies were detected between 5-26 weeks pi, varied by 10-fold between different individuals, and had no direct relationship to clinical status or time pi. Of 20 CREAE plasma with anti-myelin immunoglobulins (Igs), only 3 contained substantial amounts of antibodies to myelin lipid and these were all from animals in the late chronic phase. By contrast 15/20 of the samples contained antibodies which appeared to require lipid-protein interactions for optimal binding to antigens in isolated myelin. There was a close correlation between plasma titres of antibodies to isolated myelin and to purified myelin basic protein (MBP). Even in samples with a moderately high lipid requirement for binding to isolated myelin, purified MBP could inhibit at least 50% of the binding. These observations suggest that MBP-lipid complexes are dominant immunogens in CREAE. Gross inflammation and myelin loss in spinal cords from these CREAE guinea pigs were determined by light microscopy. Substantial inflammation was apparent in some animals between 7 and 26 weeks pi. The most severe myelin loss was observed in late chronic phase animals having plasma anti-myelin Igs with a variety of specificities. The data suggest that circulating antibodies to myelin lipids or MBP-lipid complexes could contribute to demyelination in CREAE but their titres do not correlate with the extent of this process.

Severity of demyelination in vivo correlates with serum myelination inhibition activity in guinea pigs having a new form of experimental allergic encephalomyelitis

Guinea pigs received a suboptimal transfer of lymphocytes sensitized to myelin basic protein (BP) and were then immunized with guinea pig BP, BP plus chicken brain or chicken myelin, or chicken brain alone. Sera from these animals were tested for the presence of myelinotoxic antibodies, as detected by the myelination inhibition assay. Myelination inhibition activity correlated with the histologic severity of demyelination.

Ganglioside GM1, a molecular target for immunological and toxic attacks: similarity of neuropathological lesions induced by ganglioside-antiserum and cholera toxin

Ganglioside-antisera, the ganglioside GM1-ligands, cholera toxin (CT), and CT subunit B, respectively, were injected into the lumbosacral subarachnoid space of normal rats. The cytotoxic effects of the injected compounds on the peripheral and central nervous system were investigated by light and electron microscopy; the severity of CNS lesions was evaluated by quantitation of macrophages containing debris. In contrast to control sera and GM2-antiserum, antisera against a mixture of the major brain gangliosides GM1, GD1a, GD1b, and GT1b (MaBG) or against GM1 induced demyelination in spinal roots and spinal cord, as well as alterations of astroglia. CT induced the same cytotoxic effects as MaBG- and GM1-antisera, whereas CT subunit B was without effect. The ineffectiveness of GM2-antiserum is obviously due to the very low concentration of the specific binding target, GM2, on cell surfaces; that of CT subunit B to the lack of the cytotoxic operator, subunit A. Our results indicate that a similar pattern of neuropathological lesions may be effected by different cytotoxic mechanisms through attachment of the cytotoxic agent onto the cell surface via a common target molecule, and further substantiate the role of GM1-antibodies in the pathogenesis of demyelination.

Peripheral nervous system lesions in experimental allergic encephalomyelitis. Ultrastructural distribution of T cells and Ia-antigen

The distribution of T cells and Ia-antigen in peripheral nervous system (PNS) lesions of experimental allergic encephalomyelitis was studied by light- and electron-microscopic immunocytochemical techniques. Sprague Dawley rats, sensitized with guinea pig spinal cord tissue, developed a biphasic disease with acute inflammatory and chronic inflammatory demyelinating lesions in the PNS. In both the acute non-demyelinating and the chronic demyelinating disease inflammatory infiltrates were composed of T cells and Ia-positive monocytes/macrophages. Dependent upon the stage of the disease a variable percentage of T-lymphocytes carried the Ox 8 antigen (suppressor/cytotoxic cells). In demyelinating lesions no evidence for an interaction of T cells with myelin or Schwann cells was observed, thus arguing against a direct T-cell cytotoxicity in demyelination. The whole sequence of myelin destruction and digestion was performed by W3/13-, Ia+ mononuclear cells with ultrastructural features of monocytes/macrophages. In contrast to the acute inflammatory stage of the disease, high titers of anti-myelin antibodies were present in sera of affected animals sampled during the chronic inflammatory demyelinating stage. The sera from the latter animals also showed pronounced in vivo demyelinating activity when transferred into the cerebrospinal fluid (CSF) of normal recipient rats. It is thus suggested that demyelination in this model is induced by a co-operation of cell-mediated and humoral immune mechanisms. We did not find evidence for Ia-antigen expression on local elements of the PNS (Schwann cells, axons, or endothelial cells).