High Expression of the HNK-1/L2 Carbohydrate Epitope in the Major Glycoproteins of Shark Myelin

The major 24- and 28-kDa glycoproteins in shark PNS and CNS myelin express high levels of the adhesion-associated HNK-1/L2 carbohydrate epitope. The 28-kDa protein, but not the 24-kDa protein, cross-reacts strongly with one of two anti-bovine P0 antisera not previously tested against fish myelin proteins. Shark PNS and CNS myelin also contains smaller amounts of high-molecular-weight HNK-1-positive proteins, including a prominent broad band in the 65-85-kDa range. Although myelin-associated glycoprotein (MAG) is well known to react with HNK-1 in some mammals, monoclonal and polyclonal anti-MAG antibodies did not react with the high-molecular-weight HNK-1-positive material in shark myelin, a result suggesting that it is not a MAG-like protein. The high expression of the HNK-1/L2 epitope in glycoproteins of shark myelin, including the major P0-related ones, suggests that this adhesion-related carbohydrate structure may have had an important role in the molecular evolution of the myelinating process.     

Expression of carbohydrate epitopes L2/HNK-1 and L3 in the larva and imago of Drosophila melanogaster and Calliphora vicina

Summary The carbohydrate epitopes L2/HNK-1 and L3 belong to two overlapping families of adhesion molecules in the vertebrate, and probably the invertebrate nervous systems. To investigate their pattern of expression during the development of insects, cryosections of late third instar larvae and imagoes of Drosophila melanogaster and Calliphora vicina were studied by indirect immunofluorescence using several monoclonal antibodies to the L2/HNK-1 and one monoclonal antibody to the L3 epitope. Each monoclonal antibody to the L2/HNK-1 epitope showed a different immunohistological staining pattern, which differed from that of the L3 monoclonal antibody. In both insect species the immunohistological staining patterns for the two carbohydrate epitopes were similar at the two developmental stages, with immunoreactivity not confined to the nervous system. In larvae, immunoreactivities of the monoclonal antibodies L2.334 and L3.492 were predominantly associated with the extracellular matrix as indicated by co-localization with laminin, particularly in the imaginal discs, while L2.349 revealed a more cell surface-associated distribution. In imagoes, immunoreactivities were detectable in most organs studied.     

Identification of a peptide mimic of the L2/HNK-1 carbohydrate epitope

The L2/HNK-1 carbohydrate is carried by many neural recognition molecules and is involved in neural cell interactions during development, regeneration in the peripheral nervous system, synaptic plasticity, and autoimmune-based neuropathies. Its key structure consists of a sulfated glucuronic acid linked to lactosaminyl residues. Because of its biological importance but limited availability, the phage display method was used to isolate a collection of peptide mimics that bind specifically to an L2/HNK-1 antibody. The phages isolated from a 15-mer peptide library by adsorption to this antibody share a consensus sequence of amino acids. The peptide mimicked several important functions of the L2/HNK-1 carbohydrate, such as binding to motor neurons in vitro, and preferential promotion of in vitro neurite outgrowth from motor axons compared with sensory neurons. A scrambled version of the peptide had no activity. The combined observations indicate that we have isolated a mimic of the L2/HNK-1 carbohydrate that is able to act as its functional substitute.     

Determination of structural elements of the L2/HNK-1 carbohydrate epitope required for its function

The L2/HNK-1 carbohydrate epitope has been shown to carry an unusual 3-sulfoglucuronic acid linkedO-glycosidically through a neolactosyl-type back bone to a ceramide residue. Using monoclonal antibodies, the same or a closely related epitope has also been detectedN-glycosidically linked to glycoproteins, amongst them several neural cell adhesion molecules. We used synthetic glycolipids carrying sulfated or non-sulfated glucuronic acid attached to ceramide through glycans of different length to show that not only the sulfated glucuronic acid but also the neolactosyl-type backbone is essential for the recognition of the L2/HNK-1 carbohydrate by a monoclonal antibody, its binding to laminin and its role in neural cell migration and outgrowth of processes from neurons and astrocytes.Abbreviations mab monoclonal antibody - TLC thin layer chromatography - HRP horseradish peroxidase - glcA glucuronic acid - gal galactose - glcNAc N-acetyl-glucosamine - man mannose     

Isolation and Biochemical Characterization of a Neural Proteoglycan Expressing the L5 Carbohydrate Epitope

The monoclonal L5 antibody reacts with an N-glycosidically linked carbohydrate structure which is present on the neural cell adhesion molecule L1, neural chondroitin sulfate proteoglycans, and other not yet identified glycosylated proteins. Using this antibody, we isolated and characterized proteoglycans from adult mouse brain and cultured astrocytes biosynthetically labeled with Na2 35SO4 and a 3H-amino acid mixture. Our data suggest that the L5 proteoglycans of both sources are identical in their biochemical properties. The apparent molecular mass of the L5 proteoglycan is approximately 500 kDa. Digestion of the iodinated L5 proteoglycan from mouse brain and of the [35S]methionine-labeled L5 proteoglycan from cultured astrocytes with proteinase-free chondroitinases ABC and AC revealed three major core proteins with apparent molecular masses of approximately 380, 360, and 260 kDa. These represent molecularly distinct protein cores.     

L1/HNK-1 Carbohydrate- and β1 Integrin-Dependent Neural Cell Adhesion to Laminin-1

Abstract: We have shown recently that mouse small cerebellar neurons adhere to a short amino acid sequence of the G2 domain of the laminin α1 chain via the cell surface-expressed HNK-1 carbohydrate. Therefore, we were interested in identifying glycoproteins carrying the HNK-1 carbohydrate at the cell surface of these neurons. Adhesion of small cerebellar neurons to laminin is partially dependent on Ca²⁺, Mn²⁺, and Mg²⁺, indicating the involvement of integrins, which were identified as β1, α3, and α6. They could be shown to bind to laminin by a β1-dependent adhesion mechanism. None of these subunits was found to carry the HNK-1 carbohydrate. HNK-1-immunoreactive glycoproteins were immunoprecipitated and shown to consist of predominantly one molecular species, which was identified as the neural cell recognition molecule L1. L1 was demonstrated to bind in a concentration-dependent and saturating manner to laminin. The binding could be partially inhibited by Fab fragments of monoclonal antibodies against the HNK-1 carbohydrate and against the Ig-like domains of L1. Furthermore, antibodies to the Ig-like domains of L1 and β1 integrin inhibited partially cell adhesion to laminin. Determination of the association of L1, β1 integrin, and the HNK-1 carbohydrate on the cell surface of live cerebellar neurons by antibody-induced patching and copatching revealed HNK-1 to be linked to L1, but less so to β1 integrin. However, only negligible association was found between L1 and β1 integrin. Furthermore, it could be shown that adhesion to laminin is mediated by L1/HNK-1- and β1 integrin-dependent mechanisms that act at least partially independent of each other.     

Production and Characterization of Monoclonal Antibodies to the Major Peripheral Myelin Glycoprotein P0

Several monoclonal antibodies were generated against the major glycoprotein P0 of human peripheral nervous system myelin. Antibodies were selected for their reactivity with P0 in Western blots. The antibodies were of the immunoglobulin G subclass and reacted with the glycopeptidase F-treated P0, indicating that the reactive epitope resides in the protein backbone. In fresh frozen and paraffin-embedded sections of central and peripheral nervous system of rat and human, P0 antibody 592 reacted with myelin sheaths of peripheral, but not central, nervous system.     

Developmental Expression of HNK-1-Reactive Antigens in the Rat Cerebellum and Localization of Sulfoglucuronyl Glycolipids in Molecular Layer and Deep Cerebellar Nuclei

Monoclonal antibody HNK-1-reactive carbohydrate epitope is expressed on proteins, proteoglycans, and sulfoglucuronyl glycolipids (SGGLs). The developmental expression of these HNK-1-reactive antigens was studied in rat cerebellum. The expression of sulfoglucuronyl lacto-N-neotetraosylceramide (SGGL-1) was biphasic with an initial maximum at postnatal day one (PD 1), followed by a second rise in the level at PD 20. The level of sulfoglucuronyl lacto-N-norhexaosyl ceramide (SGGL-2) in cerebellum was low until PD 15 and then increased to a plateau at PD 20. The levels of SGGLs increased during postnatal development of the cerebellum, contrary to their diminishing expression in the cerebral cortex. The expression of HNK-1-reactive glycoproteins decreased with development of the rat cerebellum from PD 1. Several HNK-1-reactive glycoproteins with apparent molecular masses between 150 and 325 kDa were visualized between PD 1 and PD 10. However, beyond PD 10, only two HNK-1-reactive bands at 160 and 180 kDa remained. The latter appeared to be neural cell adhesion molecule, N-CAM-180. A diffuse HNK-1-reactive band seen at the top of polyacrylamide electrophoretic gels was due mostly to proteoglycans. This band increased in its reactivity to HNK-1 between PD 15 and PD 25 and then decreased in the adult cerebellum. The lipid antigens were shown by two complementary methodologies to be localized primarily in the molecular layer and deep cerebellar nuclei as opposed to the granular layer and white matter. A fixation procedure which eliminates HNK-1-reactive epitope on glycoproteins and proteoglycans, but does not affect glycolipids, allowed selective immunoreactivity in the molecular layer and deep cerebellar nuclei.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Sulfation of glucuronic acid in the linkage tetrasaccharide by HNK-1 sulfotransferase is an inhibitory signal for the expression of a chondroitin sulfate chain on thrombomodulin

HNK-1 (human natural killer-1) carbohydrate epitope (HSO₃-3GlcAβ1-3Galβ1-4GlcNAc-) recognized by a HNK-1 monoclonal antibody is highly expressed in the nervous system and biosynthesized by a glucuronyltransferase (GlcAT-P or GlcAT-S), and sulfotransferase (HNK-1ST). A similar oligosaccharide (HSO₃-3GlcAβ1-3Galβ1-3Galβ1-4Xyl) also recognized by the HNK-1 antibody had been found in a glycosaminoglycan (GAG)-protein linkage region of α-thrombomodulin (TM) from human urine. However, which sulfotransferase is involved in sulfation of the terminal GlcA in the GAG-protein linkage region remains unclear. In this study, using CHO-K1 cells in which neither GlcAT-P nor GlcAT-S is endogenously expressed, we found that HNK-1ST has the ability to produce HNK-1 immunoreactivity on α-TM. We also demonstrated that HNK-1ST caused the suppression of chondroitin sulfate (CS) synthesis on TM and a reduction of its anti-coagulant activity. Moreover, using an in vitro enzyme assay system, the HNK-1-positive TM was found not to be utilized as a substrate for CS-polymerizing enzymes (chondroitin synthase (ChSy) and chondroitin polymerizing factor (ChPF)). These results suggest that HNK-1ST is involved in 3-O-sulfation of the terminal GlcA of the linkage tetrasaccharide which acts as an inhibitory signal for the initiation of CS biosynthesis on TM.     

Detection of Multisulphated N-Linked Glycans in the L2/HNK-1 Carbohydrate Epitope Expressing Neural Adhesion Molecule P0

P0, the most abundant glycoprotein of PNS myelin, is a homophilic and heterophilic adhesion molecule. P0 is known to contain a glycoform population that expresses the L2/HNK-1 carbohydrate epitope found on other neural adhesion molecules, and to be functionally implicated centrally in neural cell adhesion and neurite outgrowth. This carbohydrate epitope has been characterized previously from glycolipid structures and contains a sulphated glucuronic acid residue. However, the L2/HNK-1 carbohydrate epitope has not been characterized in glycoproteins. Because P0 possesses only one glycosylation sequon, the number of P0 glycoforms is equal to the heterogeneity of the glycan species. Here we report that the carbohydrate analysis of L2/HNK-1-reactive P0 showed the presence of anionic structures containing sialic acid and sulphate in various combinations. At least one sulphate residue was present in 80% of the monosaccharide sequences, and 20% contained three sulphates. High-resolution P4 gel chromatography of the desialylated and desulphated oligosaccharides showed substantial heterogeneity of monosaccharide sequences. Sequential exoglycosidase digestions indicated that the majority of the structures were of the hybrid class, although the sulphated structures were found to be endoglycosidase H-resistant.     

Developmental Changes in the Molecular Weights of Polypeptides in the Human CNS That Carry the HNK-1 Epitope and Bind Phaseolus vulgaris Lectins

The binding patterns of electrophoresed polypeptides from homogenates of human frontal lobe, cerebellum, and spinal cord obtained at various stages of development were determined for several lectins with specificities for a wide range of oligosaccharides. A discrete developmental change in the molecular-weight pattern was seen only among polypeptides binding the two Phaseolus vulgaris agglutinins, E-phytohemagglutinin (E-PHA) and L-PHA. With increasing maturity, the apparent molecular weights of the major polypeptides binding these two lectins progressively decreased. Furthermore, at all stages of development, E-PHA and L-PHA bound to the same polypeptides as the monoclonal antibody HNK-1, which recognizes a carbohydrate epitope on polypeptides that may play roles in cell adhesion. Based on the carbohydrate specificities of the two PHAs, we conclude that it is likely that the HNK-1 epitope resides on a triantennary N-linked oligosaccharide bisected by N-acetylglucosamine.     

Comparison of the N-Linked Oligosaccharide Structures of the Two Major Human Myelin Glycoproteins MAG and P0: Assessment of the Structures Bearing the Epitope for HNK-1 and Human Monoclonal Immunoglobulin M Found in Demyelinating Neuropathy

The epitope for HNK-1 and patient's monoclonal autoantibodies in demyelinating polyneuropathy associated with immunoglobulin M gammopathy is borne by different types of N-linked oligosaccharide structures in human P0 and myelin-associated glycoprotein (MAG). Fourteen glycopeptide fractions bearing different oligosaccharide structures were obtained from either MAG or P0 glycopeptides by serial lectin affinity chromatography on concanavalin A-Sepharose, Phaseolus vulgaris erythrophytohemagglutinin-agarose, Pisum sativum agglutinin-agarose, and Phaseolus vulgaris leucophytohemagglutinin-agarose. As shown by dot-TLC plate immunostaining, the same MAG and P0 glycopeptide fractions were recognized by HNK-1 and patient's immunoglobulin M, confirming that these antibodies display similar specificities. The antigenic carbohydrate was present in glycopeptide fractions that either interact with Pisum sativum agglutinin-agarose or were bound by Aleuria aurantia agglutinin-digoxigenin, indicating that these structures contained alpha(1-6)fucose residues. This study demonstrates that the L2/HNK-1 epitope is borne mainly or even exclusively by N-linked oligosaccharide structures alpha(1-6)fucosylated in the core.     

An Immunoglobulin M Monoclonal Antibody, Recognizing a Subset of Acetylcholinesterase Molecules from Electric Organs of Electrophorus and Torpedo, Belongs to the HNK-1 Anti-Carbohydrate Family

An immunoglobulin M (IgM) monoclonal antibody (mAb Elec-39), obtained against asymmetric acetylcholinesterase (AChE) from Electrophorus electric organs, also reacts with a fraction of globular AChE (amphiphilic G2 form) from Torpedo electric organs. This antibody does not react with asymmetric AChE from Torpedo electric organs or with the enzyme from other tissues of Electrophorus or Torpedo. The corresponding epitope is removed by endoglycosidase F, showing that it is a carbohydrate. The subsets of Torpedo G2 that react or do not react with Elec-39 (Elec-39+ and Elec-39-) differ in their electrophoretic mobility under nondenaturing conditions; the Elec-39+ component also binds the lectins from Pisum sativum and Lens culinaris. Whereas the Elec-39- component is present at the earliest developmental stages examined, an Elec-39+ component becomes distinguishable only around the 70-mm stage. Its proportion increases progressively, but later than the rapid accumulation of the total G2 form. In immunoblots, mAb Elec-39 recognizes a number of proteins other than AChE from various tissues of several species. The specificity of Elec-39 resembles that of a family of anti-carbohydrate antibodies that includes HNK-1, L2, NC-1, NSP-4, as well as IgMs that occur in human neuropathies. Although some human neuropathy IgMs that recognize the myelin-associated glycoprotein did not react with Elec-39+ AChE, mAbs HNK-1, NC-1, and NSP-4 showed the same selectivity as Elec-39 for Torpedo G2 AChE, but differed in the formation of immune complexes.     

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)     

Rapid Communication: Human Peripheral Myelin Protein-22 Carries the L2/HNK-1 Carbohydrate Adhesion Epitope

Abstract: Molecular genetic studies have established that mutations in the gene encoding the 22-kDa peripheral myelin protein (PMP-22) are responsible for hereditary peripheral neuropathies in the trembler mouse and in a subset of humans with Charcot-Marie-Tooth disease, type 1a. The function of the PMP-22 protein remains unknown. Several studies on myelin proteins in the PNS have indicated that the L2/HNK-1 epitope, which is believed to be both a ligand for cellular adhesion and a target for autoimmune monoclonal IgM neuritis, may be found on heretofore unidentified proteins with a molecular mass of 19–28 kDa. In this report, we provide immunological evidence that at least one of these proteins is PMP-22.     

Expression patterns of HNK-1 carbohydrate and serotonin in sea urchin, amphioxus, and lamprey, with reference to the possible evolutionary origin of the neural crest

We examined deuterostome invertebrates, the sea urchin and amphioxus, and an extant primitive vertebrate, the lamprey, for the presence of structures expressing the HNK-1 carbohydrate and serotonin. In sea urchin embryos and larvae, HNK-1 positive cells were localized in the ciliary bands and in their precursor ectoderm. Serotonergic cells were exclusively observed in the apical organs. In juvenile amphioxus, primary sensory neurons in the dorsal nerve cords were HNK-1 immunoreactive. The juvenile amphioxus nerve cords contained anti-serotonin immunoreactive nerve fibers that seem to be the Rohde axons extending from amphioxus interneurons, the Rohde cells. In lamprey embryos, migrating neural crest cells and primary sensory neurons, including Rohon-Beard cells, expressed the HNK-1 carbohydrate. Lamprey larvae (ammocoetes) contained cell aggregates expressing both the HNK-1 carbohydrate and serotonin in the pronephros and in the regions adjacent to the gut epithelium. Some of these cell aggregates were present in the anti-serotonin positive visceral motor nerve net. Motor neurons and Müller fibers were serotonergic in ammocoetes. Comparison of the expression patterns of HNK-1 carbohydrate among sea urchins, amphioxus and lampreys seem to suggest the possible evolutionary origin of the neural crest, that is, ciliary bands in dipleurula-type ancestors evolved into primary sensory neurons in chordate ancestors, as inferred from Garstang's auricularia hypothesis, and the neural crest originated from the primary sensory neurons.     

人乳头瘤病毒11型L1主要衣壳蛋白的B细胞表位多肽作为疫苗的研究

分析了人乳头瘤病毒11型(HPV11)L1主要衣壳蛋白的B细胞优势表位,并以此为基础研制表位多肽疫苗。研究中采用Goldkey和．PC／Gene软件系统,分析HPV11的L1主要衣壳蛋白的二级结构、抗原性、B细胞表位,并引人氨基酸抗原性指数,综合评估其B细胞优势表位。Fmoc固相合成表位多肽,高效液相层析方法纯化,毛细管电泳分析其纯度。与0．2ml佐剂完全乳化后,按50μg／只的剂量免疫小鼠,进行动物水平的免疫效果评价。取免疫小鼠血清,与HPV11 DNA阳性的尖锐湿疣患者的疣体上清液结合,鉴定免疫后小鼠所产生抗体的特异性。发现HPV11的L1主要衣壳蛋白的第426～439位和第487～501位具有较高的免疫原性,可明显诱导小鼠血清抗体滴度升高,且该抗体与人尖锐湿疣的疣体组织上清液呈阳性反应。说明所选这两个肽段为HPV11的L1主要衣壳蛋白的B细胞优势表位,但是否具有功能特异性,尚需进一步研究。     

HPV18 L2保守中和表位肽协同MF59与CpG-ODN免疫可诱发广谱中和抗体反应

摘要 目的：人乳头瘤病毒(HPV)次要外壳蛋白L2保守中和表位肽可诱发交叉中和抗体,研究L2保守中和表位肽免疫原性的特点利于HPV通用疫苗的研发。HPV18是第二常见的优势流行高危型,但18L2保守表位肽的免疫活性未见报道。方法：本研究采用化学法合成HPV18 L2N端多肽(18RG-1)并偶联KLH获得18RG1-KLH肽;联合MF59/CpG-ODN复合佐剂或弗氏佐剂皮下免疫BALB/c小鼠5次,用假病毒中和实验检测抗血清针对α6、α7、α9及α11亚属中多个致癌型HPV的中和抗体。结果： MF59/CpG-ODN复合佐剂多肽组抗血清对所有6种检测型别的中和活性与弗氏佐剂多肽组的相当。MF59/CpG-ODN佐剂多肽组抗血清具有广谱中和活性,中和范围至少包括14种致癌型HPV,中和抗体滴度最高的为HPV45 (438)和HPV18 (325),其次为HPV68 (163)和HPV70 (150),这四种优势中和型别均为α7亚属。结论：首次发现HPV18 L2 RG1保守中和表位免疫血清可诱发广谱中和抗体反应 (其中对α7亚属的HPV中和活性最强,为优势中和型别)。研究结果为基于L2保守表位的广谱HPV疫苗研发奠定基础。     

Human Myelin/Oligodendrocyte Glycoprotein: A New Member of the L2/HNK-1 Family

Abstract— Myelin/oligodendrocyte glycoprotein (MOG) is a quantitatively minor component of CMS myelin. In this study, human MOG was found to express the L2/HNK-1 epitope on N-linked oligosaccharide structures. This carbohydrate epitope has been found previously in three other characterized human myelin glycoproteins: the my-elin-associated glycoprotein, P₀, and the oligodendrocyte-myelin glycoprotein. It seems, therefore, that the L2/HNK-1 epitope is expressed frequently in human myelin glycoproteins. Serial lectin affinity chromatography of ¹⁴C-glycopeptides indicated that MOG N -oligosaccharide structures are mainly of the complex type, accounting for 77.8% of total radioactivity. In contrast with myelin-asso-ciated glycoprotein and P₀, which express the L2/HNK-1 epitope on fucosylated structures, in MOG the epitope was detected on all glycopeptide fractions obtained by serial lectin affinity chromatography, although a preferential expression of the L2/HNK-1 epitope was observed on fucosylated structures. Finally, the data indicated that, as for other human myelin glycoproteins, only a subpopulation of MOG molecules expresses the L2/HNK-1 epitope.