Structural similarity of the terminal carbohydrate sequences of glycoproteins and glycolipids

Evidence for the presence of functional lipid rafts in immune cells of ectothermic organisms

The role of lipid rafts in non-mammalian leukocytes has been scarcely investigated. We performed biochemical and functional analysis of lipid rafts in fish leukocytes. Fish Flotillin-1 and a fish GM1-like molecule (fGM1-L) were found in low density detergent-resistant membranes (LD-DRM) in goldfish macrophages and catfish B lymphocytes, similarly to mammals. The presence of flotillin-1 and fGM1-L in LD-DRM was sensitive to increased detergent concentrations, and cholesterol extraction. Confocal microscopy analysis of flotillin-1 and fGM1-L in fish leukocytes showed a distinctive punctuated staining pattern, suggestive of pre-existing rafts. Confocal microscopy analysis of macrophages showed that the membrane of phagosomes containing serum-opsonized zymosan was enriched in fGM1-L, and zymosan phagocytosis was reduced after cholesterol extraction. The presence of flotillin-1 and fGM1-L in LD-DRM, the microscopic evidence of flotillin-1 and fGM1-L on fish macrophages and B-cells, and the sensitivity of phagocytosis to cholesterol extraction, indicate that lipid rafts are biochemically and functionally similar in leukocytes from fish and mammals.

Adhesion of Escherichia coli in urinary tract infection

In individuals prone to urinary tract infections the intestine is colonized by E. Coli strains that possess a combination of properties determining virulence. Such an E. coli strain may colonize the vaginal and periurethral area and ascend the urinary tract. The ability to attach to the mucosal surface is thought to be essential for E. coli to colonize and to remain in the urinary tract. Most E. coli from patients with urinary tract infection show one or both of two adherence properties. One may depend on the recognition by type 1 fimbriae of mannose-containing residues in the urinary slime. It is measured as mannose-sensitive haemagglutination and is found on most E. coli strains. The second adherence property is detected as attachment to human urinary tract epithelial cells and as mannose-resistant agglutination of human erythrocytes. This may depend on the recognition of globo-series glycolipids in the epithelial cell surface. Possession of this adherence factor is strongly related to virulence. Most strains from patients with acute pyelonephritis and cystitis have this property but it is rare in strains from patients with asymptomatic bacteriuria and strains from normal faeces. Local antibodies may interfere with bacterial attachment, thus possibly preventing the colonization that precedes urinary tract infection or modifying an established infection. Vaginal antibodies are known to coat E. coli from the stools. Antibodies in the urine of patients with acute pyelonephritis inhibit attachment of the infecting strain to uroepithelial cells. Antibodies directed against several bacterial surface structures, for example O antigen and fimbriae, are likely to inhibit attachment by steric hindrance or agglutination. The role of antibodies in adhesion-mediating structure such as fimbriae in susceptibility to and the outcome of human urinary tract infection remains to be investigated.

Affinity of galectin-8 and its carbohydrate recognition domains for ligands in solution and at the cell surface

Galectin-8 has two different carbohydrate recognition domains (CRDs), the N-terminal Gal-8N and the C-terminal Gal-8C linked by a peptide, and has various effects on cell adhesion and signaling. To understand the mechanism for these effects further, we compared the binding activities of galectin-8 in solution with its binding and activation of cells. We used glycan array analysis to broaden the specificity profile of the two galectin-8 CRDs, as well as intact galectin-8s (short and long linker), confirming the unique preference for sulfated and sialylated glycans of Gal-8N. Using a fluorescence anisotropy assay, we examined the solution affinities for a subset of these glycans, the highest being 50 nM for NeuAcalpha2,3Lac by Gal-8N. Thus, carbohydrate-protein interactions can be of high affinity without requiring multivalency. More importantly, using fluorescence polarization, we also gained information on how the affinity is built by multiple weak interactions between different fragments of the glycan and its carrier molecule and the galectin CRD subsites (A-E). In intact galectin-8 proteins, the two domains act independently of each other in solution, whereas at a surface they act together. Ligands with moderate or weak affinity for the isolated CRDs on the array are bound strongly by intact galectin-8s. Also galectin-8 binding and signaling at cell surfaces can be explained by combined binding of the two CRDs to low or medium affinity ligands, and their highest affinity ligands, such as sialylated galactosides, are not required.

Neutral glycolipids of Schistosoma mansoni as feasible antigens in the detection of schistosomiasis

The neutral glycolipid fraction from mouse-propagated, Schistosoma mansoni adult worms has been investigated as to its chromatographic and antigenic properties, and whether it fulfills the serodiagnostic antigen requirements of sensitivity and specificity in the detection of schistosomiasis. Serological analyses were performed by thin-layer chromatography immunostaining and ELISA. In the acute-phase form of mouse schistosomiasis, the kinetics of development of neutral glycolipid-specific antibody levels was correlated with the intensity of the initial infection and the response was dominated by IgG, as represented by the subclass IgG1. With the experimental animal helminthiases screened, glycolipid antigenicity fulfilled the fundamental traits for a serodiagnostic reagent. In the chronic-phase form of human schistosomiasis mansoni, neutral glycolipid-specific antibody levels were not correlated with the intensity of infection, as estimated from the faecal content of parasite eggs, whilst the isotypic response was dominated by IgM and IgG, the latter represented primarily by IgG1 and secondarily by IgG3. With other human helminthiases, glycolipid antigenicity was incomplete, in that, the specificity was only partially fulfilled. The reason for this incomplete specificity has been clarified, in part, by the detection of cryptic schistosomiasis infections in the cohorts of African patient sera examined.

Glycans with N-acetyllactosamine type 2-like residues covering adult Schistosoma mansoni, and glycomimesis as a putative mechanism of immune evasion

Glycans at the surface of adult Schistosoma mansoni were investigated with gold-labelled lectins. The fragile complex of the glycans with the outer membranes could be preserved for electron microscopy by avoiding extensive pre-fixation with aldehydes and by introducing osmium-ferrocyanide as a membrane fixative. Male and female worms were entirely covered with glycans that intensely bound lectins from Erythrina cristagalli and Datura stramonium, suggesting that galactose(beta 1-4)N-acetylglucosamine residues occur in high numbers in the surface glycans. Similar staining was obtained with lectins from Triticum vulgaris, Glycine max and Ricinus communis agglutinin I, which react with N-acetylglucosamine or terminal galactose residues and bind non-selectively with high affinity to N-acetyllactosamine. Fucose, N-acetylgalactose and sialic acid were not detected with lectins and sialidase treatment. The tegument contained an abundance of glycans with the same lectin reactivities as the surface-expressed molecules, indicating that the worms synthesize and replenish their surface glycans and do not merely adsorb host substances. Glycomimesis is discussed as a mechanism of immune evasion in view of N-acetyllactosamine being a common and weakly immunogenic component in glycans of vertebrate hosts. S. mansoni might disguise themselves with the glycans against attack by immune effectors.

Binding of the fibrillar CS3 adhesin of enterotoxigenic Escherichia coli to rabbit intestinal glycoproteins is competitively prevented by GalNAc beta 1-4Gal-containing glycoconjugates

We have attempted to characterize the binding specificity of the coli surface 3 (CS3) subcomponent of colonization factor antigen II of enterotoxigenic Escherichia coli, by means of an immunoblot method in which the binding of fimbriated bacteria to sodium dodecyl sulfate-polyacrylamide gel electrophoresis-separated rabbit intestinal cell membranes was evaluated. Isolated CS3 fibrillae as well as bacteria expressing CS3 on their surface bound to several intestinal cell membrane structures, i.e., structures present in the electrophoretic front and in the 30- to 35-kDa range and, most prominently, 120- to 140-kDa structures. Delipidization and protein digestion of the rabbit brush borders revealed that CS3 bound to structures of a proteinaceous nature. Sodium meta-periodate oxidation of the intestinal cell membranes abolished all their CS3 binding activity, indicating that CS3 bound to carbohydrate moieties of glycoproteins. The binding of CS3 to the separated intestinal proteins could also be inhibited by preincubation with the lectin derived from Maackia amurensis, indicating that CS3 bound to galactoproteins in the rabbit intestine. Inhibition experiments using equimolar amounts of various gangliosides demonstrated that GM1, asialo-GM1, and GM2 inhibited the binding of CS3 equally well, whereas GM3 was not as effective. These results suggested that the critical CS3 binding epitope consisted of the carbohydrate sequence GalNAc beta 1-4Gal. This was supported by electron microscopic experiments showing that this disaccharide, O linked to bovine serum albumin via a spacer, localized around CS3-positive bacteria but not at all around corresponding CS3-negative mutants. Furthermore, CS3-expressing bacteria recognized this neoglycoprotein when it was immobilized on nitrocellulose. The GalNAc beta 1-4Gal disaccharide has also been implicated as a binding structure for other pathogenic bacteria such as enteropathogenic E. coli and Pseudomonas aeruginosa.

Histochemistry with Helix pomatia agglutinin in human germ cell tumors: detection of nongerminomatous components and correlation between HPA reactivity and radiosensitivity in germinomas

Binding sites of Helix pomatia agglutinin (HPA) were examined in 32 patients with intracranial human germ cell tumors. HPA reactivity was found in vascular endothelial cells and erythrocytes of patients with blood type A or AB. HPA-positive neoplastic cells were seen in one yolk sac carcinoma in a patient with blood group A, and in embryonal carcinomas and teratomas irrespective of blood group type. Although in 10 out of 18 germinomas neoplastic cells were totally negative for HPA, another 8 germinomas showed HPA-positive neoplastic cells which were distributed sporadically or in an area and independent of blood group types. HPA-negative germinoma patients showed a very good response to radiotherapy, whereas 4 out of 8 HPA-positive tumors showed poor radiosensitivity, with a residual lesion seen on computed tomography even after the total radiation dose of 40-50 Gy. These findings suggest that HPA-positive neoplastic cells in germinomas indicate components of differentiation of non-germinomatous germ cells. HPA-positive germinomas might be less radiosensitive than HPA-negative germinomas.

The expression of H-like blood group glycolipids in small cell carcinoma of the lung

Monoclonal antibody SM1 has been shown to be preferentially reactive with small cell carcinoma of the lung (SCCL) cell lines by fluorescent and radioimmunoassay membrane staining (1). Using solid phase indirect radioimmunoassay, the antigen is not detected in non-SCCL lung carcinomas histologically classified as squamous carcinoma, adenocarcinoma or large cell carcinoma, and other tumors, viz; pheochromocytoma, a mesoderm derived lymphoblastic leukemia cell line or in normal human brain, heart, liver, colon, endothelial tissues of the aorta and blood vessels, skin, omentum, muscle, lung parenchyma and is weakly reactive with bronchial mucosa, pancreas, and kidney. The membrane antigens detected by SM1 were isolated from small cell carcinoma of the lung (SCCL) cell line, SW2, using anion exchange chromatography and thin layer chromatography, and were further analysed by exoglycosidase and endoglycosidase treatments followed by chemical staining and immunostaining with SM1 and other antibodies. We show here that SM1 antibody reacts with a group of fucose-containing neutral glycolipids and gangliosides many of which are cross-reactive with antibodies to H antigens.

Identification of ancillary fim genes affecting fimA expression in Salmonella typhimurium

Regulation of the gene, fimA, encoding the major fimbrial subunit of S. typhimurium S6704 was examined by using a lambda fimA-lacZ lysogen. Transformation of the lambda fimA-lacZ lysogen with various derivatives of the recombinant plasmid that encodes type 1 fimbrial expression, pISF101, indicated that two regions of this plasmid alter beta-galactosidase production. One plasmid is a deletion resulting in the loss of a 28-kDa polypeptide downstream of fimA, while the other plasmid encodes a 24- and a 27-kDa polypeptide. Northern (RNA) blot analyses indicated that the steady-state fimA mRNA levels of these transformants were high. In addition, phenotypic expression of type 1 fimbriae by agar-grown cultures is observed only in those transformants bearing plasmids which show increased beta-galactosidase and fimA mRNA levels.

Glycolipid of human pancreatic cancer; the appearance of neolacto-series (type 2 chain) glycolipid and the presence of incompatible blood group antigen in tumor tissues

Glycolipid isolated from normal and cancerous human pancreatic tissues were characterized chemically and immunologically. The major neutral glycolipids in both normal and cancerous tissues were composed of globo-series glycolipids and lacto-series glycolipids. The mole percentage of fucolipids in the total neutral glycolipids of normal tissues was 20-40%, and in general the fucolipids corresponded to blood group glycolipids related to the patient's blood group, however, in cancerous tissues the amount of these fucolipids was decreased. Immunostaining revealed that normal tissues contained only lacto-series (type 1 chain) glycolipids. In contrast, cancerous tissues contained the neolacto-series (type 2 chain) glycolipids as well as the lacto-series glycolipids. Incompatible blood group antigens, A active glycolipids in a blood type O patient and B active glycolipids in a blood type A patient, were also detectable in the neutral glycolipid fractions of the pancreatic cancer tissues.

Effects of retinoic acid on chick tail bud development

The present study describes the teratogenic effects of retinoic acid (RA) on the development of the chick tail bud. Chick embryos were recovered 48 hours after treatment at HH stages 11 to 16 with various dosages of RA by subblastodermal injection. At the gross level, RA treatment resulted in varying degrees of caudal regression, scoliosis, limb malformations, and open posterior neuropores among the survivors. Histological examination of tail buds from treated embryos revealed defects which included total dysplasia of caudal structures, the presence of accessory neural tube and notochord tissue, and abnormal fusions of the notochord to the neural tube and tailgut. The incidence, severity, and location of the defects were dependent on the dose of the teratogen, and the stage of development at the time of treatment. The defects resembled those induced in previous studies by treatment with sialic acid binding lectins such as wheat germ agglutinin and limulus polyphemus lectin (Griffith and Wiley, '90b).

Glycoconjugate histochemistry in the glycocalyx of guinea pig middle ear mucosa

An attempt was made to determine the composition of oligosaccharide side chains in the apical cell surface glycocalices of the middle ear epithelium. This glycoconjugate is located on the innermost luminal surface, but its function is still unknown. The lectins evaluated included Triticum vulgare, Canavalia ensiformis, Maclura pomifera, Arachis hypogaea, Ricinus communis I (RCA-I), and Limax flavus. The staining results obtained with the six different lectin probes in the Lowicryl K4M-embedded guinea pig middle ear mucosa suggest that the glycocalyx contains beta-D-N-acetylglucosamine, sialic acid, and beta-D-galactose in the major carbohydrate moiety. The present study also indicates that a polarity exists on the cell surfaces in the distribution pattern of the carbohydrate component, especially those of beta-galactosyl residues, as revealed by RCA-I binding. This may imply functional separation of the epithelial cells.

Type I pili mediate gram-negative bacterial adherence to intact tracheal epithelium

We have investigated the role of pili in mediating gram-negative bacterial adherence to an intact tracheal epithelium. Type 1 pili, but not P or Pseudomonas pili, markedly increased bacterial adherence. The adherence-promoting effect of Type 1 pili was due to the mannose-binding Type 1 pili adhesin, as both alpha-methyl mannoside and concanavalin A blocked adherence of Type 1 piliated bacteria. The Type 1 pili-binding site on tracheal epithelium appears to be a mannose-containing glycoprotein. Clearance of Type 1 piliated bacteria from the lung parenchyma was assessed by depositing the bacteria into a lobe; no difference in clearance rates between Type 1 and nonpiliated bacteria was present. Type 1 pili may enhance the ability of gram-negative bacteria to adhere to and colonize the lower respiratory tract.

Structural similarity of the type-specific group B streptococcal polysaccharides and the carbohydrate units of tissue glycoproteins: evaluation of possible cross-reactivity

Type-specific capsular polysaccharides of group B streptococci show striking structural similarity with the terminal sugar sequences of tissue glycoconjugates. The polysaccharides have been put forward as vaccines against neonatal meningitis. A potential source of hazard in immunization of pregnant mothers may be the presence of the cross-reactive components in adult or fetal tissues. A radioactive ligand binding assay was used to test human immune sera to type Ia, II and III group B streptococcal polysaccharides for binding to tissue-derived glycopeptides showing structural similarities with the streptococcal polysaccharides. Of the 13 glycopeptides of human and rat tissues studied, representing a wide selection of structures known to occur in glycoproteins, only two showed some reactivity with the antisera. The reactivity with human small intestinal glycopeptides could be explained by the presence of natural blood group A antibodies, and was not related to the streptococcal group B antibodies. The basis of the reactivity of a high-molecular-weight glycopeptide from rat kidney with some of the sera was unknown, but was unrelated to the vaccination and clearly could not be inhibited with the streptococcal polysaccharides. Thus, no immunological cross-reactions of the tissue glycopeptides studied could be demonstrated with the group B streptococcal antisera.

Saccharide residues in human gingiva as revealed with fluorochrome-coupled lectins

The histochemical binding of 16 fluorochrome-conjugated lectins to human marginal gingiva was investigated. Of a total of 14 galactose/N-acetylgalactosamine (Gal/GalNAc)-specific lectins, Dolichos biflorus (DBA), Helix pomatia (HPA), and Helix aspersa agglutinins (HAA) were blood group A-reactive whereas Griffonia simplicifolia I-B4 (GSA-I-B4) and Sophora japonica (SJA) agglutinins were blood group B-reactive. HPA, HAA and GSA-I-B4 bound to all suprabasal epithelial cells and to vascular endothelia in tissues with compatible blood groups and detected only upper epithelial cells in tissues lacking the respective blood group antigens. SJA, on the other hand, bound to suprabasal epithelial cells and to endothelial cells in specimens from blood group B, AB and A individuals. DBA gave a heterogeneous labeling of upper epithelial cells in blood group A, AB and B specimens but not in O specimens and did not react with endothelia in any of the tissue samples. DBA bound, instead, consistently to mast cells in gingival lamina propria. Of the other Gal/GalNAc-reactive lectins, 2 bound to suprabasal epithelial cells and 7 to all viable cell layers in gingival epithelium. The binding of these lectins was blood group-independent. Of the fucose-specific lectins, Ulex europaeus agglutinin I (UEA-I) gave an intense suprabasal cell membrane-type of epithelial fluorescence in blood group O specimens and a more diffuse staining in other specimens and recognized endothelial cells in a blood group-independent way. Anguilla anguilla agglutinin (AAA) gave a blood group-independent epithelial staining and bound heterogeneously to endothelial cells only in blood group O samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Lectinophagocytosis mediated by bacterial surface lectins

The evidence showing that non-opsonic recognition of bacteria by phagocytes involve interaction between bacterial surface lectin and sugars on the phagocytic cells is summarized. This process, termed lectinophagocytosis, probably occur in vivo as evident from experimental infections with mixed phenotypes one of which express mannose specific (MS) lectin which mediate lectinophagocytosis of the bacteria and the other does not. In all cases studied, the lectin bearing phenotype survived better in phagocytes-poor sites and the phenotype which does not express this lectin survived better in phagocytes-rich sites. Due to the phase variation phenomenon, an off-on switch allowing the bacterial clone to alternate between lectin expressing and non-expressing phenotypes, the invading bacteria grow as a mixture of phenotypes. The phenotype expressing fimbrial lectin for which receptors are accessible on phagocytic cells undergo lectinophagocytosis. The phenotypes not expressing fimbrial lectin or expressing lectin for which receptors are not available on phagocytic cells may escape phagocytosis and proliferate. It is postulated that pathogenesis of inflammation and tissue damage following infections with MS lectin bearing bacteria may be partly due to both bacterial proliferation resulting in the release of toxic products and to lectinophagocytosis associated with the release of inflammatory agents.

Absence of a stratum corneum antigen in disorders of epidermal cell proliferation: detection with an anti-ganglioside GM3 antibody

We have investigated the distribution of ganglioside GM3 in normal skin with 8G9D8, a monoclonal antibody against GM3, and found binding to the stratum corneum. By electron microscopy, strong deposition of antibody was seen at the corneocyte envelope/"plasma membrane" region. Significantly decreased to absent binding to the stratum corneum was shown in a variety of disorders of excessive keratinocyte proliferation, including squamous cell carcinomas, psoriasis, and bullous and non-bullous forms of congenital ichthyosiform erythrodermas, as well as in the hyperplastic cornoid lamellae of porokeratosis. The 8G9D8 antibody recognizes the carbohydrate sequence N-acetylneuraminic acid alpha 2----3 galactose beta 1----4 glucose (or N-acetylglucosamine). Thus, in addition to ganglioside GM3, 8G9D8 may bind to glycoproteins or another glycolipid of the stratum corneum with a shared carbohydrate sequence. The carbohydrate sequence recognized by 8G9D8, whether attached to an epidermal glycoprotein or glycolipid, may prove to be important in keratinocyte proliferation and differentiation.

(Neo)glycoproteins as tools in neuropathology: histochemical patterns of the extent of expression of endogenous carbohydrate-binding receptors, like lectins, in meningiomas

Biotinylated (neo)glycoproteins were used to specifically detect endogenous sugar receptors such as lectins in sections of formaldehydefixed, paraffin-embedded tissue from meningiomas. The histochemical methods used consisted of the application of a carrier protein and various covalently linked sugar moieties, available mainly through chemical synthesis, in an optimized standard protocol. They proved valuable in elucidating differential binding patterns within the various meningioma subtypes. alpha-Fucoside-, beta-galactoside-, alpha-mannoside- and beta-xyloside-specific carbohydrate-binding receptors were detected in all the tumor subclasses examined, although the levels of expression exhibited pronounced quantitative differences. In addition, differences in the extent of histochemical staining were observed, using a labelled carrier protein, derived from N-acetylglucosamine and mannose-6-phosphate moieties, respectively. Quantitative differences in the reaction intensity were also measured in the respective subtypes. Receptors for N-acetyl-D-galactosamine were detected only in the analplastic forms, while glucuronic acid-specific receptors were only present in the meningotheliomatous meningioma. In contrast to the other types, malignant meningiomas failed to show cytoplasmic staining with the alpha-glucoside-specific maltose-(BSA-biotin). Distinct differences in the pattern of expression of endogenous sugar receptors, evaluated by a standard protocol, provided further evidence for a possible additional subtype of meningioma, the submalignant meningioma. Our results suggest that labelled (neo)glycoproteins could be used routinely as tools for assessing the expression of endogenous sugar receptors in diagnostic neuro-oncology.

Endogenous sugar-binding proteins in human breast tissue and benign and malignant breast lesions

Binding of carbohydrate moieties was detected in tissue sections of human breast by employing two types of labeled ligands: neoglycoproteins (chemically glycosylated, histochemically inert carrier protein) and desialylated naturally occurring glycoproteins. Paraffin-embedded, formalin-fixed sections from 40 benign and malignant breast lesions were examined for the presence and distribution of endogenous sugar receptors, employing a panel of 13 biotinylated neoglycoproteins, representing carbohydrates commonly found in naturally occurring glycoconjugates, and four biotinylated glycoproteins. Benign and malignant breast lesions revealed staining with mannosylated carrier neoglycoprotein in comparison to normal breast. A mixed pattern of staining localization and intensity was seen for different types of malignancy with this neoglycoprotein. Similarly, receptors for lactose and N-acetylglucosamine could only be detected within the cytoplasm for certain types of malignancy. Their nuclear localization, however, could also be seen in normal breast specimens. The extent of staining with different glycoproteins, containing different types of galactoside-terminal sugar chains, also appeared to differ between various types of breast cancer. The detection of endogenous sugar receptors by neoglycoproteins is proposed to contribute to an understanding of malignancy-associated alterations in the structure of their potential physiological ligands, the glycoconjugates. Changes in the structure and abundance of such glycoconjugates have commonly been detected with the use of plant lectins in histopathologic studies.

Polysaccharide and glycolipid composition in Tritrichomonas foetus

1. The polysaccharide and glycolipid composition in Tritrichomonas foetus was studied by paper, thin-layer and gas-liquid chromatographic analysis. 2. The carbohydrate components of the polysaccharide were glucose (47%), galactose (34%) and mannose (19%). N-acetylneuraminic acid was the sialic acid derivative characterized in the flagellate whole cells. 3. The sialic acid density was estimated as 2.7 x 10(7) residues/cell. 4. The long-chain base dihydrosphingosine, the carbohydrates galactose (67%), glucose (21%) and mannose (12%) as well as the fatty acids myristic (48%) and palmitic (52%) acids were characterized as components of the total glycolipids of T. foetus. 5. Total glycolipids were fractionated: a galactocerebroside and a ganglioside were identified.

Structural features and antigenic properties of carbohydrate-containing components of Trypanosoma conorhini

Aqueous and phenolic extracts of Trypanosoma conorhini were fractionated and high molecular weight, carbohydrate-rich fractions obtained. Their antigenic characteristics, reactivity with lectins and partial chemical structure were determined. The major component, the phenolic extract, was electrophoretically diffuse and consisted of 15% protein, 5% phosphorus, hexosamine, and 67% neutral carbohydrate, which contained mannose, galactose, and xylose in a molar ratio of 1.0:1.8:1.8. Chemical analyses and lectin agglutination experiments showed nonreducing end-groups of beta-D-galactopyranose, beta-xylopyranose, and alpha-D-mannopyranose. Phosphate esters occurred, apparently, at O-6 of hexopyranosyl units. Hexosamine was present as nonacetylated units of 2-amino-2-deoxy-alpha-D-glucopyranosyl units that were extremely resistant to acid hydrolysis. On double immunodiffusion tests, the major component gave a precipitation line with rabbit serum against whole cells of Trypanosoma cruzi, suggesting the presence of common antigenic determinant(s) on the cell surface of each trypanosomatid.

Binding of laminin to brain gangliosides and inhibition of laminin-neuron interaction by the gangliosides

Binding of laminin to glycolipids of neuronal membranes was studied with a thin-layer chromatography overlay assay. The major brain ganglioside GD1A was the main binding component, when chromatograms containing the same molar amount of the different brain gangliosides and the brain sulfatide were incubated with laminin at physiological ionic strength. The possible role of laminin binding to brain gangliosides in laminin-neuron interactions was studied with adhesion assays. It was found that binding of rat brain neurons to laminin is blocked by 10-40 microM brain gangliosides but not by sulfatide. The inhibition by the gangliosides is suggested to be due to competition with the cell surface interaction sites of laminin and not to binding of the gangliosides to the cells. Our findings support the idea that the adhesive and neurite-promoting effect of laminin is dependent on its interaction with gangliosides at the neuronal cell surfaces.

Thomsen-Friedenreich-related antigen in non-neoplastic ureter urothelium and transitional cell tumours of the urinary bladder. An immunohistochemical study employing the monoclonal antibody 49H.8

This study, which is part of a larger immunohistochemical investigation of blood-group antigens in non-neoplastic urothelium and bladder cancer, reports our findings on the expression of an antigen related to the cryptic Thomsen-Friedenreich antigen (beta Gal 1-3 GalNAc) of erythrocytes. De-waxed sections of 19 ureters and of 93 transitional cell tumours, either untreated or pretreated with neuraminidase, were subjected to an indirect immunoperoxidase staining, employing the monoclonal antibody 49H.8. Staining results were compared to Lewis-secretor types, morphology, and in tumours to the clinical course as regards recurrence rate and the development of either stroma invasive recurrence or papillomatosis as well. Ureters not subjected to neuraminidase were unstained, whereas urothelium in 12 of 19 ureters subjected to neuraminidase showed staining. Serial dilution of antibody disclosed quantitative differences related to the Lewis-secretor types. Lea+b- urothelium, i.e., non-secretor urothelium, had the highest end-point titers. Endothelium was unstained. Thirty-six of the 93 tumours showed staining without prior neuraminidase treatment, 31 showed staining after neuraminidase treatment only, while 26 were unstained. Staining correlated with the pathological stage and grade (p less than 0.05), but not with the clinical course (p greater than 0.05). The results do not support previous observations on the prognostic value of Thomsen-Friedenreich antigen determination in superficial bladder cancer.

Blood group-related antigens as markers of malignant potential and heterogeneity in human carcinomas

The expression of BGR-Ags is often aberrant in human carcinomas. The observation that BGR-Ag expression in human bladder carcinomas correlates with prognosis for patients with these tumors is especially interesting in light of the numerous reports of correlations between cell surface glycosylation and malignant phenotype in experimental animal tumors. Many observations suggest how this relation might be mediated. It seems reasonable to anticipate that the study of the BGR-Ags and their expression in carcinoma may emerge from its current predominantly descriptive phase and become an important part of the investigation of human tumor biology.

Isolation and characterization of a neutral glycosphingolipid from the epimastigote form of Trypanosoma mega

A glycosphingolipid fraction from Trypanosoma mega was isolated after acetylation and was further purified on a silicic acid column. Final purification was by preparative thin-layer chromatography. The carbohydrate components of the glycolipid were fucose and galactose in approximately equimolar amounts. The neutral glycolipid of T. mega has a sphingosine base composition that consists of sphingosine and traces of dihydrosphingosine. Fatty acids forming amide groups with the sphingosine bases were analyzed by gas-liquid chromatography-mass spectrometry and are a mixture of normal and alpha-hydroxy fatty acids. Normal C16:0, C18:0, and 2-hydroxy C18:0 are the predominant fatty acids.

Binding specificity of monoclonal antibodies to ganglioside, Fuc-GM1

The binding specificity of thirteen mouse monoclonal antibodies reacting with Fuc-GM1, Fuc alpha 1-2Gal beta 1-3GalNAc beta 1-4(NeuAc alpha 2-3)-Gal beta 1-4Glc beta 1-1Cer, a ganglioside found to be associated with small cell lung carcinoma (O. Nilsson et al. (1984) Glycoconjugate J. 1, 43-49) was studied. The results are based upon radioimmunodetection of their binding to structurally related glycolipids adsorbed to microtiter plates or chromatographed on thin-layer plates. Four of thirteen antibodies reacted only with Fuc-GM1 and both the fucose and the sialic residues were necessary for binding. Optimal binding was obtained when the sialic acid was N-acetylneuraminic acid. When this sialic acid residue was substituted with N-glycoloylneuraminic acid the binding activity was reduced and up to 10-times more Fuc-GM1 was needed for detection. The ceramide composition did not influence the binding. The other nine monoclonal antibodies cross-reacted with glycolipids containing structures closely related to Fuc-GM1 and differed from the specific ones by recognizing a smaller portion of the carbohydrate moiety in Fuc-GM1. These results indicate that anticarbohydrate monoclonal antibodies, recognizing structures involving a large proportion of the sugar in the glycolipid, possess a high specificity and might be useful for detection of tumor-associated ganglioside antigen.

Thin layer chromatography overlay technique in the analysis of the binding of the solubilized protoxin of Bacillus thuringiensis var. kurstaki to an insect glycosphingolipid of known structure

The hypothesis tested was that a particular glycoconjugate(s) in the exposed cell-surface membrane of susceptible insect cells acts as a receptor and/or modulator for the specific interaction with the protoxin/activated toxin of the delta-endotoxin of Bacillus thuringiensis var. kurstaki. As candidates, the total neutral and acidic fraction glycolipids, and the isolated neutral glycosphingolipid components, were screened for binding activity by the thin layer chromatogram overlay technique. The main protoxin/activated toxin-binding glycolipid in the neutral fraction (5B) had the structure: Gal(alpha 1-3)GalNAc(beta 1-4)GlcNAc(beta 1-3)Man(beta 1-4)Glc(beta 1-1)Cer. The main protoxin/activated toxin-binding glycolipid in the acidic fraction was designated band 1, the structure of which is at present unknown. The possibility that the component 5B carbohydrate sequence may also function as a toxin-binding site of relevant insect plasma membrane glycoproteins is discussed.

Population heterogeneity in the surface expression of Ulex europaeus I-lectin (UEA I)-binding sites in cultured malignant and transformed cells

We studied the binding of fluorochrome-coupled Ulex europaeus I-lectin (UEA-I) to cultured malignant cells: all human malignant and transformed cells and also mouse teratocarcinoma cells examined gave a homogeneous cell membrane-type of surface staining only in some of the cells. Such a population heterogeneity appeared to be independent of the cell cycle. Instead, other lectin conjugates used bound homogeneously to all cells. In permeabilized cells, a juxtanuclear reticular staining of the Golgi apparatus was seen in the UEA-I-positive cells. No staining of the pericellular matrix components, produced by malignant cells grown in serum-free culture medium, could be obtained with TRITC-UEA-I. UEA-I-lectin recognized most polypeptides from A8387 fibrosarcoma cells and HeLa cells, metabolically labeled with [3H]fucose. Furthermore, surface labelling of these cells with the neuraminidase-galactose oxidase/sodium borohydride method disclosed that both UEA-I and Ricinus communis agglutinin I revealed the same major surface glycoproteins. Results with metabolically labelled cells showed, in addition, that UEA-I-lectin did not bind to secreted glycoproteins produced by A8387 cells and recognized by other lectins. The results indicate that transformed and malignant cells show a distinct population heterogeneity in their expression of some cell surface-associated fucosyl glycoconjugates. The results also suggest that malignant cells can glycosylate their membrane and secreted glycoproteins in a different manner.

Partial immunochemical identity between (Na+ + K+)-ATPase and a membrane component extractable with chloroform: methanol

An IgG fraction prepared from an antiserum against a holoenzyme preparation of (Na+ + K+)-ATPase precipitated a single antigen when samples of holoenzyme were subjected to crossed immunoelectrophoresis but precipitated an additional, immunochemically-related antigen when a plasma membrane-enriched fraction was subjected to crossed immunoelectrophoresis under the same conditions. The immunochemically-related antigen could be extracted from the plasma membrane fraction with CHCl3:CH3OH.

Galactose-rich glycoproteins are on the cell surface of herpes virus-infected cells. 1. Surface labeling and serial lectin binding studies of Asn-linked oligosaccharides of glycoprotein gC

Cell-surface glycoproteins of mock-infected and herpes simplex virus type 1 (HSV-1)-infected BHK-21 and HEp-2 cells were radiolabeled by incubation with galactose oxidase followed by reduction with NaB3H4. The incorporation of radiolabel into glycoconjugates in both BHK-21 and HEp-2 cells was increased several fold following infection with HSV, showing an increase in surface-exposed Gal residues in the infected cells. This was further confirmed by an increase in binding of cell-surface-labeled glycoproteins gC and gB from HSV-infected BHK-21 cells to Ricinus communis agglutinin I, which is specific for beta-D-Gal residues. Prior treatment of cells with Clostridium perfringens neuraminidase enhanced the surface radiolabeling by the galactose oxidase/NaB3H4 method: HEp-2 cells exhibited over sixfold enhancement in labeling, while BHK-21 cells showed only a slight increase. HSV glycoprotein gC was the predominant cell-surface glycoprotein radiolabeled by the galactose oxidase/NaB3H4 method in virus-infected BHK-21 cells. The glycoprotein gC was purified by immunoaffinity column chromatography on monoclonal anti-gC-antibody-Sepharose. The radiolabel in the glycopeptides of gC was resistant to beta elimination, showing that it was associated only with Asn-linked oligosaccharides. A serial lectin affinity chromatography of glycopeptides on columns of concanavalin A-Sepharose, lentil (Lens culinaris) lectin-Sepharose, and Ricin I-agarose allowed the assignment of minimal oligosaccharide structures bearing terminal Gal residues in gC.

Isolation of variants of BALB/c 3T3 cells defective in complex ganglioside biosynthesis

In an attempt to clarify the relationship between altered glycosphingolipid metabolism and other aspects of the transformed phenotype, we have isolated variants of BALB/c 3T3 cells (clone A31) which are defective in synthesis of the more complex gangliosides (GM2, GM1 and GD1a). The selection protocol was based on the specificity of cholera toxin for ganglioside GM1, and the ability to lyse cells which bound toxin using anti-toxin and complement. Following treatment of cells with ethane methane sulfonate (EMS), populations resistant to lysis were obtained after 5-6 rounds of selection, despite a low and rather variable killing efficiency (75-95%). Five out of six clones isolated from such populations showed reduced toxin-binding capacity and loss of gangliosides more complex than GM3, as determined by metabolic labelling with [1-14C] palmitate. An identical phenotype was displayed by a variant isolated from a non-mutagenized population of cells. The phenotype remained stable for several months in culture and for over at least 40 cell doublings. Ganglioside nomenclature is according to Svennerholm [24].

Carbohydrate structure in tumor immunity

Researchers have endeavored to define surface alterations associated with neoplasia for at least 25 years. In comparisons of normal tissues with animal and human tumors, cultured cells before and after transformation with oncogenic agents, tumorigenic and nontumorigenic transformed cells, metastatic and nonmetastatic tumor cells, high- and low-metastatic variants, and tumor cells before and after induction of differentiation to a less malignant phenotype, a consistent finding has been some form of alteration in surface carbohydrate structures. These changes in glycolipids, glycoproteins and glycosaminoglycans are reviewed, and their structures are illustrated. Both nucleotide sugar biosynthesis and glycosyltransferase changes have been associated with these alterations. In some cases, alterations in transformed cells were related to growth, rather than transformation. In others, the altered glycoconjugates are truly tumor-associated. There is evidence that cell surface glycoconjugates may function in growth control. Altered carbohydrate structures could also serve as receptors for growth promoting factors and be directly responsible for altered growth control. Recent studies with monoclonal antibodies indicate that the vast majority of antibodies recognizing tumor-associated antigens are detecting altered carbohydrate structures. Mechanisms by which the immune system can recognize these carbohydrate structures are considered, and immune recognition of tumor-associated carbohydrate structural alterations is explored. A number of these hypotheses relating to alterations in glycosylation, growth control, and tumor immunity deserve further investigation.

T and Tn, general carcinoma autoantigens

Primary and metastatic carcinomas are epithelial in origin and comprise by far the largest group of malignant tumors in humans. In most of these tumors, T and Tn antigens, whose epitopes have been synthesized, are uncovered and immunoreactive. In all other tissues T and Tn antigens are masked and not accessible to the immune system; they are generally precursors in normal complex carbohydrate chains. Thus, carcinomas have antigens recognized as foreign by the patients' immune system. The expression of T and Tn antigens has pathogenic and clinical consequences, and the antigens themselves are powerful histological markers in carcinoma diagnosis and frequently in prognosis. Most patients distinguish their carcinoma from all other cells, as shown by strong autoimmune responses to T antigen. These responses are readily measured by assays, and they allow detection of carcinomas with greater sensitivity and specificity frequently earlier than previously possible. Moreover, the extent of T and Tn expression often correlates with carcinoma differentiation; on a molecular level, clustered T- and Tn-active structures on carcinoma cell surfaces may be involved in invasion.

Distribution of carbohydrate residues in normal skin

Sections of biopsies of normal skin obtained from 11 individuals were incubated with 8 lectins using an avidin-biotin complex (ABC). All sections when incubated with the appropriate lectin showed the presence of the following carbohydrate residues: L-fucose, beta-(1-4)-D-GlcNAc)2 (N-acetylglucosamine), acetylneuraminic acid, Gal-beta-(1-3)-GalNAc (N-acetyl-galactosamine), beta-D-galactose, alpha-D-glucose, and alpha-D-mannose. In addition, sections of individuals with blood group A showed alpha-D-GalNAc and sections of individuals with blood group B showed alpha-D-galactose. In the stratum (str.) basale, carbohydrates were present in small quantities, but as the cells matured and moved upward, the incorporation of carbohydrates into the cell membranes increased considerably. In the str. granulosum, lectin reactivity was absent in many sections, probably due to masking by phospholipids. The dark cells in the eccrine glands showed reactivity with all lectins except in the one nonsecretor with blood group A1, whose dark cells showed no L-fucose and alpha-D-GalNAc. The endothelial cells of the blood vessels showed lectin reactivity except when incubated with concanavalin A. The sebaceous glands showed both cytoplasmic and membrane staining when incubated with various lectins.

Identification and isolation of Lewis blood group antigens from human saliva using monoclonal antibodies

Solid-phase radioimmunoassay, polyacrylamide gel electrophoresis and thin-layer chromatography were used to compare, identify, and characterize the Lewis antigens from human salivas, using monoclonal antibodies directed to the Lea and Leb determinants. Sialylated Lea glycolipid was detected in saliva from individuals with Le(a+ b+) and Le(a+ b-) phenotypes. Immunoaffinity chromatography of the saliva from individuals with different phenotypes revealed a glycoprotein of molecular weight greater than 200 kD bearing the Lewis antigenic determinants.

Cell adhesion mediated by a purified fucosyltransferase

Human embryonic skin fibroblasts attach and spread on surfaces on which a fucosyltransferase purified from human milk has been immobilized. The adhesion-enhancing effect of the transferase involves specific interactions of the enzyme surface with the cell surface carbohydrate acceptors, as suggested by the following findings. About 80% of human embryonic skin fibroblasts attach and spread in 1 hr on fucosyltransferase surfaces; in contrast, bovine serum albumin, fetuin, asialofetuin, and asialotransferrin surfaces fail to enhance adhesion. The adhesion-mediating activity of the transferase is destroyed by alkylation of the sulfhydryl groups or by heating. The adhesion on fucosyltransferase surfaces is inhibited by glycoprotein, glycolipid, and oligosaccharide acceptors containing the sugar sequence galactosyl-(beta 1 leads to 4)-N-acetylglucosamine, in agreement with the substrate specificity of the enzyme. The results suggest that glycosyltransferases are able to stimulate cell adhesion in a manner similar to that proposed for lectins.

A monoclonal antibody which detects a cell surface antigen on murine embryonal carcinoma and early mouse embryo stages may recognize a carbohydrate determinant involving alpha-linked galactose

A rat monoclonal antibody (5D4) apparently specific for murine embryonal carcinoma cells and cells of the pre-implantation embryo is described. It does not react with differentiated cells from a variety of different tumours and tissues of the mouse. Biochemical studies show that the molecules that carry 5D4 antigen are resistant to protease digestion on the cell surface but susceptible to procedures which affect carbohydrate structure. It is likely that this antibody detects a carbohydrate bearing determinant which may include an alpha-linked galactose residue.

Identical lectin binding patterns of human melanocytes and melanoma cells in vitro

Cell surface glycoconjugate patterns of human epidermal cells and of melanoma cells (MC) in primary culture derived from 11 primary and metastatic melanomas were investigated using fluorescent and horseradish peroxidase conjugated lectins for visualization at the light and electron microscopic level. The lectin labeling profiles of human melanocytes (M) and MC were found to be identical. According to their binding patterns, the lectins tested were grouped into three categories: (1) lectins binding to both keratinocytes (K) and M/MC, irrespective of neuraminidase pretreatment (concanavalin-A, wheatgerm agglutinin, succinylated wheatgerm agglutinin); (2) lectins binding to K but not to M/MC, irrespective of neuraminidase pretreatment (Ulex europaeus agglutinin I); (3) lectins binding to K, but to M/MC only after neuraminidase pretreatment (soybean, Helix pomatia, and peanut agglutinins). Untreated M were reactive for soybean and peanut agglutinins only at contact sites with K. Since the lectins from soybean, Helix, and peanut bind specifically to D-galactose and N-acetyl-D-galactosamine residues, we conclude that these particular glycoconjugates are normally masked by sialic acid on M/MC surfaces and can be unmasked by neuraminidase. These features, which have been previously observed in guinea pig M, appear to be interspecies surface markers of melanocytic cells which remain unaltered in the course of malignant transformation.