Structure of sulfated glucuronyl glycolipids in the nervous system reacting with HNK-1 antibody and some IgM paraproteins in neuropathy

N-acetyl-D-glucosamine is present in cysts and trophozoites of Giardia lamblia and serves as receptor for wheatgerm agglutinin

Previously, on the basis of lectin binding and glycosidase digestion assays, we have suggested that N-acetyl-D-glucosamine residues (GlcNAc) are major structural components of both trophozoites and in vivo cysts of the intestinal parasite Giardia lamblia. In this report we confirm that GlcNAc is present both in trophozoites and in vitro cysts as assessed by lectin binding and glycosidase digestion assays, galactosyltransferase labeling, immunochemical analysis using antibodies specific for GlcNAc and its beta 1-4 oligomers, and by gas chromatography/mass spectrometry (GC/MS). The results show that wheatgerm agglutinin (WGA) binds specifically to intact trophozoites and in vitro cysts as well as to SDS-PAGE separated proteins. WGA binding to the separated proteins was markedly reduced after their digestion with N-acetyl-beta-D-glucosaminidase, supporting the conclusion that WGA is reacting with terminal beta-linked GlcNAc residues. Labeling of trophozoites and cysts by 3H-exogalactosylation with galactosyltransferase further confirmed the presence of terminal GlcNAc in both surface and intracellular glycoproteins. The presence of GlcNAc is also supported by microfluorometric analysis using antibodies to (GlcNAc)1, (GlcNAc)2, and (GlcNAc)3, which revealed a sugar-inhibitable binding of the antibody to live trophozoites. Finally, the presence of GlcNAc in both cysts and trophozoites was unequivocally confirmed by GC/MS analysis of detergent-extracted membranes and of glycoproteins isolated by affinity chromatography on WGA-agarose. GC/MS analysis also revealed mannose (Man), N-acetyl-D-galactosamine (GalNAc), fucose (Fuc), galactose (Gal), glucose (Glc) and N-acetylneuraminic acid (NANA) to be present in cysts. All these sugars were also present in trophozoites, except for GalNAc. The glycoproteins isolated by WGA affinity chromatography were 5- to 40-fold enriched in GlcNAc, further supporting the conclusion that WGA reacts with GlcNAc in Giardia. In summary, the data presented here provide biological and chemical evidence for GlcNAc in both cysts and trophozoites of G. lamblia and are consistent with previously published results from this and other laboratories.

Affinity immunoblotting detection of serum monoclonal immunoglobulins reactive with glycosphingolipids

The characterization of serum monoclonal IgM reactive with glycosphingolipid present in the nervous system is of major importance in patients with certain neuropathies. A rapid, sensitive and specific one-step method which permits such a characterization is described. Serum immunoglobulins separated by high resolution agarose electrophoresis are transferred to affinity filters (nitrocellulose sheets coated with glycolipids), and revealed with enzyme-tagged monospecific anti-immunoglobulin antibodies.

Oligosaccharide-related epitope specific for a brain-specific glycoprotein, 1D4 antigen

The characteristics of glycosylation of a brain-specific glycoprotein, 1D4 antigen, and the epitope recognized by its monoclonal antibody were studied. Removal of high-mannose and hybrid types of N-linked oligosaccharides by treatment with endoglycosidase H converted the molecular mass of the 1D4 antigen from 89 kDa to 78 kDa, but did not affect its reactivity with the 1D4 monoclonal antibody. Removal of all types of N-linked oligosaccharides by treatment with glycopeptidase F or removal of both N- and O-linked oligosaccharides by chemical treatment caused both reduction of the molecular mass of the antigen to 63 kDa and loss of its reactivity with the monoclonal antibody. These results suggest that the 1D4 monoclonal antibody recognizes a complex-type oligosaccharide-related epitope specific for the 1D4 antigen. Results also showed that N-linked glycosylation was not responsible for the charge heterogeneity of the 1D4 antigen. The oligosaccharide chain-related epitope was detected in rat brain but not in mouse, rabbit, or bovine brain, but the 1D4 antigen was recognized in rat and mouse brains with antiserum (polyclonal antibodies). These findings indicate that the oligosaccharide-related epitope is species specific. Furthermore, results with neuraminidase-treated 1D4 antigen indicated that sialic acids were not involved in the oligosaccharide-related epitope. These findings suggest that the 1D4 antigen may have the oligosaccharide structure specific for rat brain and itself.

Immunochemical analysis of a monoclonal antibody recognizing a terminal glucuronic acid-containing epitope of insect acidic glycolipids

A cloned, hybridoma cell-line was established that secreted the monoclonal antibody CAF-I following stimulation of the donor Balb/c mouse spleen cells by the total acidic fraction glycolipids of the third-instar larvae of Calliphora vicina (Insecta:Diptera). The monoclonal antibody isotype was IgG3 By qualitative (TLC-immunostaining) and semi-quantitative (enzyme-linked immunosorbent assay) methods, and comparison with the cross-reactivity of known monoclonal antibodies, the epitope was specifically located on the terminal, non-reducing end of the oligosaccharide chain of most of the insect acidic glycolipids. Following isolation of the two main acidic glycolipids of C. vicina larvae (A5c and Az5c), exoglycosidase treatment characterized the terminal disaccharide CAF-I epitope as glucuronic acid bound to subterminal galactose, both in the beta-anomeric configuration: G1cA beta-Ga1 beta-. The immunohistological distribution of this epitope in the dipteran, Drosophila melanogaster, showed its main expression to be in the imaginal discs and brain of the third-instar larva, and the retinula cells of the ommatidial elements of the compound eye retina of the adult female.

Variability in the structural requirements for binding of human monoclonal anti-myelin-associated glycoprotein immunoglobulin M antibodies and HNK-1 to sphingoglycolipid antigens

A high proportion of patients with neuropathy have immunoglobulin M (IgM) paraproteins that react with carbohydrate determinants on the myelin-associated glycoprotein (MAG) and two sphingoglycolipids, 3-sulfoglucuronyl paragloboside (SGPG) and 3-sulfoglucuronyl lactosaminyl paragloboside. In order to characterize the fine specificities of these human antibodies further, the binding of 10 anti-MAG paraproteins to several chemically modified derivatives of SGPG was compared with the binding to intact SGPG by both TLC-overlay and enzyme-linked immunosorbent assay. The following derivatives were tested: the desulfated lipid, glucuronyl paragloboside (GPG); the methyl ester of GPG (MeGPG); the methyl ester of SGPG, 3-sulfomethylglucuronyl paragloboside (SMeGPG); and 3-sulfoglucosyl paragloboside (SGlcPG) produced by reduction of the carboxyl group of the glucuronic acid with sodium borohydride. All 10 IgM paraproteins and the related mouse IgM antibody, HNK-1, reacted most strongly with intact SGPG, but variations in the reactivity with the derivatives revealed striking differences in the structural requirements for binding between the antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Sulfated glucuronyl paragloboside in rat brain microvessels

In patients with neuropathy associated with paraproteinemia, there are monoclonal immunoglobulin M antibodies reacting with myelin-associated glycoprotein and sulfated glucuronyl glycolipids. There are indications that the monoclonal antibodies may be responsible for these neuropathies. However, the mechanism by which the antibodies gain access to the nervous tissue, which is separated by the blood-brain barrier or blood-nerve barrier, is still unknown. In this study, we examined the presence of the sulfated glucuronyl glycolipid antigens on brain endothelial cells. Microvessels were isolated from adult Lewis rat brain cortex. Sulfated glucuronyl paragloboside (SGPG) was detected in the acidic lipid fraction by a TLC immunostaining method. Immunofluorescence studies showed positive staining on the surface of microvessels. In addition, SGPG could be detected in the cultured endothelial cells of human umbilical vein. These findings suggest that the endothelial cells contain antigenic sites for interaction with the autoantibodies. This type of interaction may result in damages to the endothelial cell function and may be responsible for changes in the blood-brain barrier permeability and the ensuing penetration of large molecules, such as immunoglobulins, into the endoneurial space.

Localization of sulfated glucuronyl glycolipids in human dorsal root and sympathetic ganglia

Sulfated glucuronyl glycolipids (SGGLs) in human dorsal root ganglion (DRG) and sympathetic ganglion (SG) were analyzed biochemically and immunohistochemically. SGGLs were enriched in human DRG (1.02 +/- 0.23 micrograms/mg protein), whereas much lower concentrations of these glycolipids (0.043 +/- 0.23 micrograms/mg protein) were detected in SG. Myelin within DRG and SG was immunostained by anti-SGGL antiserum, although only a few myelinated fibers were seen in SG. Nerve cell bodies or unmyelinated fibers were not immunostained. Subcellular fractionation study of human DRG demonstrated that these glycolipids were not only enriched in myelin but also in the axolemma-enriched fraction. These data are consistent with the view that SGGLs may be expressed on myelinated fibers in myelin and axolemma, suggesting that these compounds may play an important role in regulating myelinogenesis.

Sulfoglucuronyl glycolipids bind laminin

Previous studies have shown that HNK-1 antibody reactive glycoconjugates, including the glycolipids 3-sulfoglucuronylneolactotetraosylceramide (SGGL-1) and 3-sulfoglucuronylneolactohexaosylceramide (SGGL-2), are temporally and spatially regulated antigens in the developing mammalian cortex. Extracellular matrix glycoprotein laminin is involved in cell adhesion by interacting with cell surface components and also promotes neurite outgrowth. Laminin has been shown to bind sulfatide. The interaction of sulfated glycolipids SGGL-1 and SGGL-2 with laminin was studied by employing a solid-phase radioimmunoassay and by HPTLC-immunoblotting. Laminin binding was detected with anti-laminin antibodies followed by 125I-labelled Protein A and autoradiography. Laminin binds SGGL-1 and SGGL-2, besides sulfatide, but does not bind significantly gangliosides and neutral glycolipids. The binding of SGGLs to laminin was two to three times less compared to sulfatide when compared on a molar basis. Desulfation of SGGLs and sulfatide by mild acid treatment resulted in abolition of laminin binding. On the other hand, chemical modification of glucuronic acid moiety by either esterification or reduction of the carboxyl group had no effect. This showed that the sulfate group was essential for laminin binding. Of the various glycosaminoglycans tested, only heparin inhibited the binding of laminin to SGGLs and sulfatide in a dose-dependent manner. This indicated that SGGLs and sulfatide bind to the heparin binding site present in the laminin molecule. The availability of HNK-1 reactive glycolipids and glycoproteins such as SGGLs and several neural cell adhesion molecules to bind laminin at critical stages of neural development may serve as important physiological signals.

Human monoclonal IgM with autoantibody activity against two gangliosides (GM1 and GD1b) in a patient with motor neuron syndrome

Small amounts of oligoclonal immunoglobulins were detected by Western blotting in the serum from a patient with motor neuron syndrome. The prominent one, a monoclonal IgM lambda, reacted strongly with the gangliosides GM1 and GD1b and more weakly with asialo GM1, as shown by immunoenzymatic staining of thin-layer chromatograms of gangliosides, ELISA on purified glycolipid coats and immunoadsorption with purified GM1. Affinity-chromatography with purified GM1 resulted in the purification of monoclonal IgM lambda. This purified IgM and its Fab fragments showed the same pattern of reactivity with gangliosides as that observed with whole serum. Such monoclonal IgM could be responsible for motor neuron diseases in some patients with overt or barely detectable monoclonal gammopathies.

Loss of sulfoglucuronyl and other neolactoglycolipids in Purkinje cell abnormality murine mutants

A significant reduction in the content of two members of the sulfoglucuronyl-neolacto series of glycolipids (SGGLs), 3-sulfoglucuronyl-lacto-N-neotetraosylceramide (SGGL-1) and 3-sulfoglucuronyl lacto-N-norhexaosylceramide (SGGL-2), in the cerebellum of the Purkinje cell abnormality mutants, Purkinje cell degeneration (pcd/pcd), lurcher (Lc/+), and staggerer (sg/sg), was also confirmed in the mildly affected nervous (nr/nr) mutant. The expression of SGGLs was studied during development of the pcd/pcd mutant cerebellum, and it was shown that the rate of decline in the level of SGGLs practically coincided with the loss of Purkinje cell perikarya. This indicated that SGGLs are primarily localized in Purkinje cells and that initially, at least, there is no genetic defect in the biosynthesis of SGGLs in the mutant. The precursors of SGGLs, viz., lacto-N-neotetraosylceramide (paragloboside) and lacto-N-norhexaosylceramide, as well as other glycolipids derived from these precursors, such as X-determinant fucoglycolipids and disialosyllacto-N-neotetraosylceramide, were also present in normal cerebellum. Levels of paragloboside and its other derivatives, similar to SGGLs, were also significantly reduced in the Purkinje cell abnormality mutants pcd/pcd, sg/sg, Lc/+, and nr/nr but were normal in other cerebellar mutants, such as quaking (qk/qk), weaver (wv/wv), and reeler (rl/rl), where Purkinje cells are not involved. Thus, the entire paragloboside family of glycolipids is primarily associated with Purkinje cells in the cerebellum. Although levels of monoclonal antibody HNK-1-reactive glycolipids were reduced in the Purkinje cell abnormality mutants, HNK-1-reactive glycoproteins were not affected in these mutants.

Identification of disialosyl paragloboside and O-acetyldisialosyl paragloboside in cerebellum and embryonic cerebrum

The lacto series of glycolipids are only minor constituents in mammalian CNS and are found mostly during development. Expression of a significant amount (70 micrograms of neuraminic acid/g dry weight) of disialosyl-lacto-N-neotetraosylceramide (LD1) in adult mouse cerebellum is reported for the first time in the nervous system. The structure of this ganglioside was determined by hydrolysis with various glycosidases, immunochemical tests, sugar and fatty acid analyses after permethylation and capillary GLC-mass spectrometry, sugar linkage analysis of permethylated alditol acetates, and fast-atom bombardment-mass spectrometry of the native ganglioside. The structure of LD1 was determined to be NeuAc-NeuAc alpha 2-3Gal beta 1-4GlcNAc beta 1-3Gal beta 1-4Glc beta 1-1-ceramide. The major fatty acid was 18:0, and the long-chain base was C18-sphingenine. Mouse cerebellum also contained O-acetyl-LD1 and several other O-acetylated gangliosides as recognized by monoclonal antibodies ME311 and 3G5. The levels of LD1 and O-acetyl-LD1 in cerebellum increased during postnatal development. During development of the Purkinje cell degeneration mutant, pcd/pcd, the levels of both of these gangliosides in the cerebellum declined with the loss of Purkinje cells, a finding indicating that these gangliosides are primarily associated with Purkinje cells. In the cortex, LD1, O-acetyl-LD1, and O-acetyl GD3, like GD3, are developmentally regulated antigens and are only expressed in the fetal cortex and not to any significant extent in the adult.

Characterization of HNK-1 bearing glycoproteins in human peripheral nerve myelin

The HNK-1 carbohydrate epitope, which is shared by several members of the immunoglobulin gene super-family, is also the target epitope for IgM anti-MAG autoantibodies in patients with demyelinating neuropathy. By Western blot analysis, there are 7 HNK-1 immunoreactive glycoproteins in human peripheral nerve myelin, two of which have previously been identified as the myelin associated glycoprotein (MAG) and the P0 glycoprotein. In this study, the remaining HNK-1 bearing glycoprotein bands were characterized by immunoblot and NH2-terminal sequence analysis, and were all identified as degradation products or aggregates of the Po glycoprotein. MAG and P0 are therefore the only HNK-1 bearing glycoproteins in human peripheral nerve myelin.

Binding of the J1 adhesion molecules to extracellular matrix constituents

The J1 glycoproteins can be obtained in multiple forms in the soluble fraction of developing and adult mouse brain tissue. They are recovered as two forms of apparent molecular weights of 160,000 and 180,000 (J1-160) from adult mouse brain and as forms of apparent molecular weights of 200,000 and 220,000 (J1-220) from developing brain. J1-160 and J1-220 share common epitopes but are considered as separate entities, with J1-220 being immunochemically closely related if not identical to tenascin. Based on the observation that J1 immunoreactivity appears on basement membrane and interstitial collagens after denervation of the neuromuscular junction in adult rodents, we became interested in investigating the binding properties of J1 glycoproteins to extracellular matrix constituents in vitro. Both J1-160 and J1-220 bound to collagens type I-VI and IX but not to laminin, fibronectin, bovine serum albumin, or gelatin under hypotonic buffer conditions. Under isotonic buffer conditions, J1-220 bound to all collagen types, whereas J1-160 bound only to collagen types V and VI with values that could be examined by Scatchard analysis. Binding of J1-220 to collagens displayed two binding constants (KD) between 1.5 and 4.4 X 10(-9) and 1.8 and 5.5 X 10(-8) M, respectively, under hypotonic buffer conditions and a single KD of 2.1-8.0 X 10(-8) M under isotonic buffer conditions. Binding of J1-160 to collagens had an apparent KD of 1.9-8.0 X 10(-9) M under hypotonic buffer conditions. Under isotonic buffer conditions, binding constants of J1-160 to collagen types V and VI were approximately 2 X 10(-8) M. Binding of J1-220 to collagen type I could be inhibited by J1-220, J1-160, and collagen type VI but not by fibronectin or gelatin. Conversely, binding of J1-160 was inhibited by J1-220, J1-160, and collagen type VI (in order of decreasing efficacy of competition). J1-160 and J1-220 were retained on a heparin-agarose column and eluted in a salt gradient at approximately 0.5 M NaCl. The formation of the J1-heparin complexes was inhibited 100-fold more efficiently by heparin than by chondroitin sulfate. These experiments show that J1 glycoproteins resemble in many respects the extracellular matrix constituents fibronectin, laminin, vitronectin, and von Willebrand factor.

Evidence for the expression of a glucuronic acid-containing epitope in the central nervous system of two insects (Calliphora vicina, Diptera; Tenebrio molitor, Coleoptera)

The monoclonal antibody CAF-I recognises a glucuronic acid-containing epitope present on various acidic glycosphingolipids of Calliphora vicina. Immunohistochemistry was performed on CAF-I-labelled whole-mount preparations of the central nervous system, visualised by peroxidase-conjugated second antibody. A differential, temporal and spatial expression of this epitope in metamorphosing nervous tissue was outlined, that apparently characterises homologous neuronal populations in two phylogenetically distinct holometabolous insects, i.e. Calliphora vicina and Tenebrio molitor. Implications for a functional interpretation of insect glyco(sphingo)lipids in tissue development are discussed.

Human neuroectoderm-derived cell line secretes fibronectin that shares the HNK-1/10C5 carbohydrate epitope with neural cell adhesion molecules

A human malignant melanoma cell line, Melur, secretes several glycoproteins that contain a unique carbohydrate epitope shared by neural cell adhesion molecules and recognized by the monoclonal antibodies HNK-1, L2, and 10C5. In this report, we present evidence that one of the major melanoma glycoproteins containing the HNK-1/10C5 epitope is the cell adhesion molecule, fibronectin, or a fibronectin-like molecule. Melanoma-derived fibronectin was isolated from serum-free conditioned medium by gelatin-Sepharose affinity adsorption and shown to react with monoclonal antibodies HNK-1 and 10C5 in Western blot analysis. HNK-1-containing fibronectin was purified on a gelatin-Sepharose column followed by an affinity column using a monoclonal antibody against the HNK-1 carbohydrate. The purified HNK-1-fibronectin then could be incorporated into the extracellular matrix of hamster fibroblasts in vitro, and such a matrix was detectable using the HNK-1 monoclonal antibody in an immunofluorescence assay. Of the seven neuroectoderm-derived tumor cell lines tested, only the Melur melanoma cell secreted fibronectin containing the HNK-1 carbohydrate. Identification of human neuroectoderm-derived fibronectin as a potential carrier of the HNK-1 carbohydrate suggests a new role for fibronectin in neural development and regeneration, and represents a new model for studying the function of this carbohydrate domain in neural cell adhesion.

Autoimmune mechanisms in peripheral neuropathies

In certain patients with demyelinating neuropathy and plasma cell dyscrasia, there are IgM monoclonal antibodies that recognize a carbohydrate epitope shared by myelin-associated glycoprotein (MAG) and at least two acidic glycolipids in the peripheral nervous system (PNS). The structures of the two acidic lipids have been elucidated as a new class of glycosphingolipids, termed sulfoglucuronyl glycolipids (SGGLs). SGGLs have been demonstrated to be present in myelin, axolemma, and other glia-related membranes in PNS of several animal species, as well as in human dorsal root ganglia and sympathetic ganglia. In rabbits sensitized with sulfoglucuronyl paragloboside (SGPG), a major SGGL in PNS, antibodies developed with reactivities toward SGPG and MAG. The animals also showed moderate weakness, a slowed nerve conduction velocity, and evidence of conduction block. Recently we also found SGPG in rat brain microvessels. This finding supports our hypothesis that autoantibodies may first interact with endothelial cell-bound antigens and that this might change the permeability of the blood-brain or blood-nerve barrier to permit the entry of these autoantibodies into the nervous system. Our data are consistent with the concept that an autoimmune response against the sulfoglucuronyl residue may participate in the pathogenesis of immune-mediated neuropathy.

Antibodies to gangliosides and myelin proteins in Guillain-Barré syndrome

An earlier investigation from our laboratory (Ilyas AA, Wilson HJ, Quarles RH, et al. Serum antibodies to gangliosides in Guillain-Barré syndrome. Ann Neurol 1988;23:440-447) demonstrating the presence of high levels of antiganglioside ganglioside antibodies in the sera of 5 of 26 patients with Guillain-Barré Syndrome (GBS) but not in control sera is summarized. The ganglioside antigens varied among the 5 patients with positive findings, and the antiganglioside antibodies decreased concurrently with clinical improvement in those patients for whom longitudinal samples were available for analysis. The results are discussed in the context of antibodies to acidic glycolipids in other types of neuropathy and other studies on antiglycolipid antibodies in GBS. Data showing the occurrence of lower levels of antibodies to P2 protein, P0 glycoprotein, and myelin-associated glycoprotein in some of the GBS patients are also summarized. The findings from our laboratory combined with the results of others make it unlikely that antiganglioside antibodies have a notable pathogenic effect in most patients with GBS, but the possibility remains that they are of pathogenic importance in some patients with the highest antibody titers.

Anti-GM1 ganglioside antibodies with differing fine specificities in patients with multifocal motor neuropathy

Antibodies to gangliosides were detected in sera from three of 19 patients with chronic inflammatory polyneuropathy (CIP) by a thin-layer chromatogram overlay technique. All three of the patients fell into a clinical subset of the group that had multifocal motor neuropathy, and in all three patients the antibodies reacted with GM1 ganglioside. However, the fine specificities of the antibodies differed as demonstrated by cross-reactivity with different gangliosides in each of the three patients. The antibodies in patient 1 reacted with GM1, GD1b, and asialo-GM1 suggesting that the terminal Gal(beta 1-3)GalNAc moiety that is common to these three glycolipids is an important part of the epitope(s). This was confirmed by showing reactivity of the antibodies with Gal(beta 1-3)GalNAc conjugated to bovine serum albumin. Patient 2 had antibodies that did not react with GD1b, but cross-reacted with GM2 ganglioside suggesting that the epitope(s) involved the inner portion of the oligosaccharide moiety that is shared between GM1 and GM2. Patient 3 had antibodies that reacted with GM1 and asialo-GM1, but they did not cross-react with either GD1b or GM2. These results provide further evidence for a relationship between motor nerve syndromes and anti-GM1 antibodies and also suggest that GM1 could be a principal target antigen since other reactive gangliosides differed among the patients. However, the possible pathogenic effects of anti-GM1 antibodies on motor nerves remain to be established.

Anti-myelin-associated glycoprotein IgM antibody titers in neuropathy associated with macroglobulinemia

Twenty-seven patients with neuropathy and IgM monoclonal gammopathy were tested for antigen specificity of the M-protein and for anti-myelin-associated glycoprotein (MAG) IgM levels by immunoblot. In 16 patients (59.2%) the M-protein reacted with MAG and with cross-reactive glycoconjugates. Anti-MAG IgM titers in these patients ranged between 1:12,800 and 1:100,000. A fainter IgM reactivity with MAG and related glycoconjugates was detected in 3 additional patients with neuropathy, but also in 8 of 24 patients with IgM M-protein without neuropathy (33.3%). This reactivity was not due to the M-protein and corresponded to antibody titers of 1:400 or less in all but 1 patient with a titer of 1:3,200. Low titers of anti-MAG IgM (1:200 or less) were also detected in 17 of 101 control patients without IgM M-proteins (16.8%), while 1 patient with neuropathy of unknown cause had anti-MAG IgMK titers of 1:25,600. In 1 patient with neuropathy and IgM M-protein that was not anti-MAG, the M-protein bound to other antigens in nerve, while in 6, other possible causes or mechanisms for the neuropathy were found. In this study, high titers of anti-MAG IgM antibodies were always associated with neuropathy. The presence of low levels of anti-MAG IgM in a significant proportion of controls suggests that monoclonal expansion of naturally occurring B-cell clones secreting anti-MAG IgM may be responsible for the high incidence of this antigen specificity of the M-protein.

Motor neuropathy with activity of monoclonal IgM antibody to GD1a ganglioside

A patient with motor neuropathy associated with monoclonal IgM protein is reported. Using enzyme-linked immunosorbent assays, the antibody activity of the monoclonal IgM was shown to be directed against GD1a ganglioside, a new and so far unreported specificity.

Ganglioside function in the development and repair of the nervous system. From basic science to clinical application

Gangliosides play important roles in the normal physiological operations of the nervous system, in particular that of the brain. Changes in ganglioside composition occur in the mammalian brain not only during development, but also in aging and in several neuropathological situations. Gangliosides may modulate the ability of the brain to modify its response to cues or signals from the microenvironment. For example, cultured neurons are known to respond to exogenous ganglioside with changes characteristic of cell differentiation. Gangliosides can amplify the responses of neurons to extrinsic protein factors (neuronotrophic factors) that are normal constituents of the neuron's environment. The systemic administration of monosialoganglioside also potentiates trophic actions in vivo and improves neural responses following various types of injury to the adult mammalian central nervous system. The possible molecular mechanism(s) underlying the ganglioside effects may reflect an action in modulating ligand-receptor linked transfer of information across the plasma membrane of the cell.

Myelin-associated glycoprotein (MAG) and rat brain-specific 1B236 protein: mapping of epitopes and demonstration of immunological identity

The myelin-associated glycoprotein (MAG) and the brain 1B236 protein are 100-kDa glycoproteins containing 30% carbohydrate that exist in two developmentally regulated forms and are specific to the nervous system. Recent cDNA cloning experiments in several laboratories using primarily immunological means of identification have determined the complete primary sequence of a rat brain glycoprotein that seems to correspond to both MAG and 1B236, suggesting that these proteins are identical. However, MAG was previously considered to be an oligodendrocyte/myelin specific component in the CNS at all ages, whereas 1B236 was thought to be primarily a neuronal component in adult rats but synthesized by oligodendrocytes at the time of active myelination. The composite term 1B236/MAG was proposed to describe the molecule identified by the cDNAs. In order to explore further the relationship between MAG and 1B236, as well as their developmentally regulated forms, experiments were carried out on rat samples utilizing synthetic peptides corresponding to sequences throughout the 1B236 molecule, antisera raised to synthetic peptides in the C-terminus of 1B236 that distinguish between the two developmentally regulated forms, and well-characterized polyclonal and monoclonal antibodies raised to purified MAG. Epitope mapping demonstrated that reactive sites were distributed throughout the extracellular and intracellular domains of 1B236/MAG. Only antibodies reacting with the smaller of the two forms of 1B236/MAG detected the glycoprotein in the peripheral nervous system. Both anti-MAG and anti-1B236 antibodies revealed a drastic reduction of the level of 1B236/MAG in 25-day-old myelin-deficient rats and in adult quaking mice, and both types of antibodies revealed a slight shift of 1B236/MAG toward higher apparent Mr in quaking mice as had previously been reported for MAG. The results indicate that MAG and 1B236 are almost certainly identical since they cannot be distinguished immunologically by the reagents available and that quantitatively most of the glycoprotein is associated with oligodendrocytes and myelin rather than neurons at all ages.

Identification of a sulfoglycolipid epitope shared by cells of neuroectodermal and hematopoietic origin

Monoclonal antibody (mAb) SNH.1 detects an epitope which is restricted to cells of neuroectodermal and hematopoietic origin. The mAb was obtained by immunization of a mouse with liposomes containing a crude extract of human melanoma acidic glycolipids. The SNH.1 antigen isolated from melanoma was identified as a sulfated glycolipid, closely related or identical to sulfogalactosyl-ceramide. When tested with different lipids, mAb SNH.1 reacted as well with other sulfoglycolipids. The staining of mAb SNH.1 is restricted to the cytoplasm and often localized to the perinuclear region. Therefore, the SNH.1 mAb epitope may be detectable only during the biosynthesis of sulfoglycolipids.

CD36 directly mediates cytoadherence of Plasmodium falciparum parasitized erythrocytes

Erythrocytes infected with P. falciparum express knob-like adhesion structures that allow the infected cells to cling to the postcapilliary endothelium of characteristic host organs. At present, the mechanism of cytoadherence is not fully understood. While parasitized erythrocytes have been shown to specifically bind to the platelet/matrix molecule thrombospondin, adherence to suitable target cells can also be blocked by monoclonal antibody OKM5, which recognizes a surface molecule expressed by hematopoietic cells and endothelium. In apparent reconciliation of these findings, it has been reported that the OKM5 antigen (CD36) is a receptor for thrombospondin. Here we report that expression of a CD36 cDNA clone in COS cells supports cytoadherence of parasitized erythrocytes but does not support increased binding of purified human thrombospondin.

Immunohistochemical localization of Forssman glycosphingolipid-positive macrophages and reticular cells in murine lymphoid tissue

Forssman (Fo) glycolipid antigen, as detected by a monoclonal antibody (mAb), is expressed by a subpopulation of murine macrophages in the spleen and peripheral lymph nodes. The histological distribution of Fo antigen in spleen and lymph nodes was studied by immunostaining of cryosections, and was compared with the staining pattern of four other mAbs known to recognize macrophage subpopulations: F4/80, Mac-1, MOMA-1, and ERTR-9. Fo+ macrophages were found exclusively in the red pulp of the spleen and the medulla of inguinal and axial lymph nodes. Macrophages in the other lymphoid organs were Fo-. Besides macrophages, reticular cells in T-dependent areas of spleen and lymph nodes were Fo+. Attempts to grow colonies of Fo+ macrophages from either bone marrow or spleen precursors were negative. While the usual number of F4/80+ colonies was obtained, only a few, small clusters of Fo+ macrophages were formed, which speaks against an early commitment of precursors to express Fo.

IgM gammopathy and polyneuropathy react with an antigenic glycolipid present in human central nervous system

An immunological mechanism may be responsible for the peripheral neuropathies associated with the IgM monoclonal gammopathies. Myelin-associated glycoprotein, and sulfated glucuronic acid-glycosphingolipids of the paragloboside type specific of peripheral nervous system (PNS), have been found to be targets for these antibodies. We report here on the presence of a glycolipid antigen present in central nervous system white matter in 7 of 12 patients with IgM monoclonal gammopathy and neuropathy whose IgM reacts also with the specific sulfated glycolipids of PNS. Immunodetection of the antibodies was performed on thin-layer plates after separation of the glycosphingolipids from peripheral nerve and white matter. The lipid antigen had a migration on thin-layer chromatography close to sulfogalactosylceramide but the sulfatide standard did not react with the monoclonal IgM.

Antibodies to the mammalian adhesion molecule J1/tenascin and its carbohydrate epitope L2/HNK-1 label the receptor lymph cavities of insect sensilla

Data from light- and electronimmunocytochemistry gave evidence that the antibodies to the mammalian adhesion molecule J1/tenascin and its carbohydrate structure L2/HNK-1 react with immunoreactive structures present in the inner and outer receptor lymph cavities of antennal sensilla of the honey bee. Immunoreactivity was additionally present in the cytoplasm of the enveloping cells surrounding the receptor lymph cavities. Cell contacts between enveloping cells and between dendrites and enveloping cells were never observed to be antigen positive.

N-linked oligosaccharides are not required for neuron-neuron interactions mediated by neural cell adhesion molecule

Recent studies have described the role of various regions of the neural cell adhesion molecule (NCAM) in cell-cell interactions. Monoclonal antibodies (L2/HNK-1) directed against a sulfated, glucuronic acid-containing, N-linked carbohydrate epitope have also been shown to inhibit NCAM-mediated neural cell adhesion. In the present study we show that dissociated retinal neurons in an in vitro model system can bind as well to normal NCAM as to NCAM lacking the L2/HNK-1 epitope or to glycopeptidase F-treated NCAM. These data suggest that N-linked oligosaccharide chains do not confer upon NCAM the adhesional properties associated with its role in neuron-neuron interactions.

Alterations of cell-surface carbohydrates during differentiation and development

Expression of many cell-surface carbohydrates is controlled temporally and spatially by developmental programs. This subject is reviewed from 5 viewpoints: structural changes revealed by chemical analysis, cell-surface markers useful for cell identification and separation, core proteins carrying the developmentally regulated carbohydrate chain, glycosyltransferases responsible for the change and the biological meaning of the phenomenon. The differentiation systems covered are mainly early mammalian embryogenesis and the differentiation of blood and nerve cells.

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

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

Detection of the L2/HNK-1 carbohydrate epitope on glycoproteins and acidic glycolipids of the insect Calliphora vicina

The same or a very similar carbohydrate determinant, as represented by some sulfated, glucuronic acid-containing glycosphingolipids of human peripheral nerve, occurs on several adhesion molecules in the mammalian nervous system. In the present study, the occurrence of this epitope on glycoproteins and glycolipids of the fly, Calliphora vicina, was investigated by Western blot analysis and thin-layer chromatogram immunostaining. Several monoclonal antibodies recognizing an epitope on various neural cell adhesion molecules, designated L2 (334, 336, 349, and 412); the monoclonal antibody HNK-1 (recognizing an epitope on human natural killer cells); and a human IgM M-protein were found to react by Western blot analysis with various glycoproteins from larval and adult brains, although the intensity of staining of bands recognized by each antibody varied. Acidic glycolipids from pupae were also recognized, but only by the L2 antibody 334 and IgM M-protein. After desulfation of the acidic glycolipid fraction, the immunostaining pattern remained the same, an observation suggesting that the L2/HNK-1 epitope on insect acidic glycolipids contains a nonsulfated, glucuronic acid moiety. These observations indicate that the L2/HNK-1 carbohydrate structure occurs not only in vertebrates but also in insects on both glycoproteins and glycolipids, a finding suggesting a high degree of phylogenetic stability of this functionally important carbohydrate.

Identification and characterization of gangliosides reacting with IgM paraproteins in three patients with neuropathy associated with biclonal gammopathy

IgM monoclonal antibodies from three patients with polyneuropathy associated with biclonal gammopathy reacted with monosialoganglioside GM1 on thin-layer chromatograms. An IgM paraprotein in one of the patients with a predominantly motor neuropathy also reacted strongly with the ganglioside GD1b and asialo-GM1. All three of these antigenic lipids have a Gal(beta 1-3)GalNAc moiety in common which would appear to be the antigenic determinant. However, this IgM also cross-reacted weakly with paragloboside which has an N-acetyllactosaminyl [Gal(beta 1-4)GlcNAc] terminal structure. The specificity of the other paraprotein in this patient is not known. The IgM paraproteins reacting with GM1 in both of the other patients exhibited different specificity because they did not react with GD1b and asialo-GM1, but reacted strongly with GM2 ganglioside. The data suggest that the epitope for both of these IgMs is in the GalNAc(beta 1-4)(NeuAc alpha 2-3)Gal(beta 1-4)Glc region of the gangliosides that is common to both GM2 and GM1. The second IgM paraproteins in both of these latter patients react with the myelin-associated glycoprotein (MAG) and two 3-sulfoglucuronyl glycolipids that share antigenic determinants with MAG.

Preparation and characterization of antibodies against a sulfated glucuronic acid-containing glycosphingolipid

In some patients with demyelinating neuropathy there are immunoglobulin M paraproteins that react with carbohydrate determinants shared by myelin-associated glycoprotein (MAG) and two peripheral nerve acidic glycolipids, termed sulfoglucuronosylglycosphingolipids (SGGLs). To study the antigenicity of these glycolipids, we immunized three New Zealand white rabbits with sulfoglucuronosylparagloboside (SGPG), a major SGGL in peripheral nerve, emulsified in Freund's complete adjuvant and keyhole limpet hemocyanin. All three rabbits inoculated with SGPG showed weight loss and mild weakness, predominantly in their hind feet, 2-5 weeks postinoculation (PI). Two of the three rabbits again showed moderate weakness 3 and 8 months PI, respectively. Electrophysiological studies demonstrated a slowed nerve conduction velocity in the sciatic nerve. Anti-SGPG antibody titers in sera were detected at dilutions of 1:1,000 to 1:2,500 by an enzyme-linked immunosorbent assay. Although all three rabbit sera reacted with SGGLs, two reacted with a desulfated form of SGPG and the other did not, suggesting a fine heterogeneity in antigenic specificity. As with sera from patients with demyelinative paraproteinemia, all rabbit sera reacted with MAG in human CNS and PNS myelin. They also reacted with MAG from bovine CNS myelin as well as several low-molecular-weight glycoproteins in bovine peripheral nerve myelin. Thus, we demonstrated that the rabbit antisera generated against SGPG have the same or similar antigenic specificity as those of the anti-MAG M-proteins from patients with neuropathy. The results suggest that an autoimmune response against the sulfoglucuronosyl residue may participate in the immunopathogenesis of this type of neuropathy.

NK cells in patients with peripheral neuropathy and IgM monoclonal protein reacting with the myelin-associated glycoprotein (MAG)

We studied Leu 7+ cell distribution and natural killer (NK) activity in the peripheral blood of six patients who had peripheral neuropathy and monoclonal IgM protein directed against myelin-associated glycoprotein (anti-MAG IgM). We did not find any difference between patients and control subjects (healthy or polyneuropathic, some with IgM monoclonal paraprotein but without anti-MAG activity). The presence of autologous sera did not interfere with these results. We noted an increase in Leu 11+ cell percentages after pre-incubation of the patient cells with autologous sera but the phenotypes of cells from control subjects did not change after incubation with autologous or patient sera.

Developmental and pathophysiological aspects of the myelin-associated glycoprotein

1. A glycoslylated sulfate-containing protein known as myelin-associated glycoprotein (MAG) appears to be unique to the central and peripheral nervous systems. This component has been characterized and cDNA clones have been isolated. 2. MAG is a member of the immunoglobulin superfamily. The principal form of MAG synthesized in brain during active myelination has an apparent molecular weight of 100,000. Alternate exon splicing leads to an additional 5000-dalton smaller form with a different C terminus. 3. In patients with multiple sclerosis, MAG is rapidly lost in areas of active disease. It is immunologically reactive in patients with benign monoclonal gammopathy associated with peripheral neuropathy. 4. The role of MAG in the formation of the myelin sheath and its participation in autoimmune neurological disorders are outlined.

Sulfoglucuronyl neolactoglycolipids in adult cerebellum: specific absence in murine mutants with Purkinje cell abnormality

It is shown here that glycolipids of the sulfoglucuronyl neolacto series (SGGLs) are present in the adult rodent cerebellum. SGGLs were not detected in the cerebellar murine mutants lurcher, Purkinje cell degeneration, and staggerer, in which Purkinje cell loss is the primary defect. SGGLs were present, however, in normal amounts in weaver and reeler mutants, in which there is a major and relatively specific loss of granule cells without obvious deficiency in Purkinje cells. In the myelin-deficient quaking mutant, the expression of SGGLs also was nearly normal. The loss of SGGLs in Purkinje cell-deficient mutants was specific, since most of the major lipids were not affected significantly and only the percentage composition of other lipids, such as sulfatides and gangliosides, was altered in the mutants. These and other results strongly suggest that SGGLs and other glycolipids of the paragloboside family are localized specifically in Purkinje cells and their arbors in the adult cerebellum. This is the first demonstration of the localization of a specific glycolipid and its analogs in a specific cell type in the nervous system.

Serum antibodies to gangliosides in Guillain-Barré syndrome

To determine whether antibodies to acidic glycolipids of nervous tissue are present in patients with Guillain-Barré syndrome (GBS), sera from patients with GBS and appropriate control subjects were tested by a thin-layer chromatogram overlay technique. Chromatograms on which the whole ganglioside fractions from peripheral nerve and brain had been separated were overlaid with appropriate dilutions of the patients' sera (1:100 or greater), and antibody binding was revealed with a radiolabeled or peroxidase-labeled second antibody. Antibodies to ganglioside antigens were detected in 5 of 26 patients with GBS. IgG antibodies in 1 patient reacted strongly with LM1 (sialosyl paragloboside), the major ganglioside of human peripheral nervous system myelin, and its hexaose analog (sialosyl lactosaminyl paragloboside), a minor ganglioside of human peripheral nervous system myelin. The antibody titer in this patient fell 8-fold over 6 weeks coincident with clinical improvement. IgG from 2 other patients with GBS reacted with GD1b ganglioside, and the antibody titers in these patients also decreased substantially with clinical improvement. IgM antibodies in the sera from 2 other patients reacted with GD1a and GT1b gangliosides, which have a shared terminal carbohydrate sequence. Antibodies to gangliosides were not detected in the sera from 19 patients with other neurological diseases or from 10 normal subjects, and the frequency with which antiganglioside antibodies occurred in the patients with GBS was significantly greater than that in the combined control subjects (p less than 0.01). The results demonstrate relatively high levels of antibodies to gangliosides in some GBS patients.

Spatial regulation of axonal glycoprotein expression on subsets of embryonic spinal neurons

The identification of surface proteins restricted to subsets of embryonic axons and growth cones may provide information on the mechanisms underlying axon fasciculation and pathway selection in the vertebrate nervous system. We describe here the characterization of a 135 kd cell surface glycoprotein, TAG-1, that is expressed transiently on subsets of embryonic spinal cord axons and growth cones. TAG-1 is immunochemically distinct from the cell adhesion molecules N-CAM and L1 (NILE) and is expressed on commissural and motor neurons over the period of initial axon extension. Moreover, TAG-1 and L1 appear to be segregated on different segments of the same embryonic spinal axons. These observations provide evidence that axonal guidance and pathway selection in vertebrates may be regulated in part by the transient and selective expression of distinct surface glycoproteins on subsets of developing neurons.

Distribution of glucuronic acid-and-sulfate-containing glycoproteins in the central nervous system of the adult mouse

The distribution of glucuronic acid-and-sulfate-containing carbohydrate (GSC) epitope recognized by two monoclonal antibodies, HNK-1 and 4F4, was studied by immunocytochemistry in adult mouse brain. Both antibodies recognized proteins ranging in molecular weight from 60 to above 250 kDa in Western blot but no glycolipid was recognized in the adult brain. With both light and electron microscopic study, two patterns of staining are observed: diffuse neuropil staining, and individual neuronal somata staining. The diffuse neuropil staining is concentrated in discrete anatomically defined areas. At the EM level, this immunoreactivity is associated with numerous dendrites or astrocytic processes. At cell somata, most of neurons are stained only at Golgi apparatus (type 2); however, a distinct population of cells showed membranous staining (type 1) as well. Type 1 membranous immunoreactivity is observed only in membrane adjacent to astrocytic processes. In the cerebral cortex, type 1 neurons are found in layers III and V-VIa of somatosensory cortex, but only in layers V-VIa in most other cortical fields. Other areas containing type 1 neurons include the globus pallidus, the thalamic reticular nucleus, the hippocampus, the deep cerebellar nuclei, and a majority of the primary sensory and motor nuclei in the brainstem. The subpopulation of type 1 neurons show an overlap in distribution and morphology with some GABA-containing cells.

Antibodies to sulfated glucuronic acid containing glycosphingolipids in neuropathy associated with anti-MAG antibodies and in normal subjects

Serum of patients with neuropathy and IgM monoclonal antibodies (M-proteins) that bind to the myelin-associated glycoprotein (MAG) were tested for binding to the major cross-reactive sulfated glucuronic acid containing glycosphingolipid, sulfated glucuronic acid paragloboside (SGPG). IgM binding to the glycolipid was detectable at serum dilutions of 1:10,000 and reactivity was greatest at 4 degrees C. Low titers of IgM binding to the glycolipid were also detected in sera from normal subjects and from patients with neurologic or rheumatologic diseases without serum M-proteins. Binding activity was present in 25% of the sera tested, and titers ranged between 1:25 and 1:400. One patient with peripheral neuropathy, however, had a measurable titer of 1:12,800 in the absence of monoclonal gammopathy. The study indicates that cold reacting anti-SGPG IgM antibodies are frequent constituents of the normal human antibody repertoire, and that monoclonal or polyclonal expansion of B cells that secrete these antibodies, is associated with peripheral neuropathy.