Glycosphingolipid carriers of carbohydrate antigens of human myeloid cells recognized by monoclonal antibodies

Sphingolipids and plasma membrane hydrolases in human primary bronchial cells during differentiation and their altered patterns in cystic fibrosis

Human primary bronchial epithelial cells differentiated in vitro represent a valuable tool to study lung diseases such as cystic fibrosis (CF), an inherited disorder caused by mutations in the gene coding for the Cystic Fibrosis Transmembrane Conductance Regulator. In CF, sphingolipids, a ubiquitous class of bioactive lipids mainly associated with the outer layer of the plasma membrane, seem to play a crucial role in the establishment of the severe lung complications. Nevertheless, no information on the involvement of sphingolipids and their metabolism in the differentiation of primary bronchial epithelial cells are available so far. Here we show that ceramide and globotriaosylceramide increased during cell differentiation, whereas glucosylceramide and gangliosides content decreased. In addition, we found that apical plasma membrane of differentiated bronchial cells is characterized by a higher content of sphingolipids in comparison to the other cell membranes and that activity of sphingolipids catabolic enzymes associated with this membrane results altered with respect to the total cell activities. In particular, the apical membrane of CF cells was characterized by high levels of ceramide and glucosylceramide, known to have proinflammatory activity. On this basis, our data further support the role of sphingolipids in the onset of CF lung pathology.

The Role of Glycosphingolipids in Immune Cell Functions

Glycosphingolipids (GSLs) exhibit a variety of functions in cellular differentiation and interaction. Also, they are known to play a role as receptors in pathogen invasion. A less well-explored feature is the role of GSLs in immune cell function which is the subject of this review article. Here we summarize knowledge on GSL expression patterns in different immune cells. We review the changes in GSL expression during immune cell development and differentiation, maturation, and activation. Furthermore, we review how immune cell GSLs impact membrane organization, molecular signaling, and trans-interactions in cellular cross-talk. Another aspect covered is the role of GSLs as targets of antibody-based immunity in cancer. We expect that recent advances in analytical and genome editing technologies will help in the coming years to further our knowledge on the role of GSLs as modulators of immune cell function.

Human platelets express gangliosides with LKE activity and ABH blood group activity

BACKGROUND

Platelets express several neutral glycosphingolipids with ABH and P blood group activity that may play a role in infectious, autoimmune, and alloimmune thrombocytopenia. In RBCs, sialylated glycosphingolipids or gangliosides with blood group activity have also been reported. To determine whether similar antigens are expressed by platelets, the total platelet ganglioside fraction was isolated and screened for blood-group-active glycosphingolipids.

STUDY DESIGN AND METHODS

Platelet gangliosides were isolated by organic extraction, base hydrolysis, anion exchange, silicic acid, and high-performance liquid chromatography. Gangliosides were identified and characterized by high-performance thin-layer chromatography-immunostaining with blood group-specific MoAbs and glycosidase digestion.

RESULTS

Group A, but not group O, platelets express five gangliosides with group A activity. Of five A MoAbs and lectins examined, only MoAbs Birma-1 and MHO4 recognized all five sialyl A bands. The sialyl A bands were sensitive to endoglycoceramidase and neuraminidase. One sialyl A band may represent a branched ganglioside with sialyl-I and group A activity. Platelets also express an LKE-active ganglioside consistent with sialyl-galactosylgloboside.

CONCLUSION

In addition to sialyl-iI and sialyl-Le(x) gangliosides, group A platelets express gangliosides with LKE activity and group A activity. Like RBCs, group A-active gangliosides may act as alloantigens and autoantigens to naturally occurring isohemagglutinins.

Total synthesis of VIM-2 ganglioside isolated from human chronic myelogenous leukemia cells

A total synthesis of the tumor-associated glycolipid antigen, VIM-2, is described [2]. Phenyl 2,3,4-tri-O-benzoyl-6-O-benzyl-beta-D-galactopyranosyl-(1-->4)-6-O-benzy l-2- deoxy-2-phthalimido-1-thio-beta-D-glucopyranoside (7), a key intermediate prepared by condensation of phenyl 6-O-benzyl-2-deoxy-2-phthalimido-1-thio-beta-D-glucopyranoside (6) and 2,3,4-tri-O-benzoyl-6-O-benzyl-alpha-D-galactopyranosyl bromide (5), was glycosylated with methyl 2,3,4-tri-O-benzyl-1-thio-beta-L-fucopyranoside (8) to give the trisaccharide donor 9, which, on coupling with 2-(trimethylsilyl)ethyl 2,4,6-tri-O-benzyl-beta-D-galactopyranosyl-(1-->4)-2,3,6-tri-O-benzyl-be ta-D- glucopyranoside (10), afforded the pentasaccharide 11. The regioselective glycosylation of 12 (derived by O-debenzoylation of 11) with 7 gave the heptasaccharide 13, which was converted by treatment with hydrazine monohydrate and subsequent N-acetylation into the hexasaccharide acceptor 14. The stereo- and regio-selective glycosylation of 14 with methyl (phenyl 5-acetamido-4,7,8,9-O-benzoyl-3,5-dideoxy-2-thio-D-glycero-beta-D-galact o-2- nonulopyranosid)onate (16) gave the desired octasaccharide 18. Hydrogenolytic removal of the benzyl groups in 18 and successive O-acetylation, removal of the 2-(trimethylsilyl)ethyl group, and treatment with trichloroacetonitrile gave the alpha-trichloro-acetimidate 21, which was then coupled with (2S,3R,4E)-2-azido-3-O-(tert-butyldiphenylsilyl)-4-octade cene-1,3-diol (22) to give 23. Compound 23 was transformed, via selective reduction of the azido group, N-introduction of octadecanoic acid, O-desilylation, O-deacylation, and saponification of the methyl ester group, into the title VIM-2 ganglioside 26.

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.

Distribution of VIM-2 and SSEA-1 glycoconjugate epitopes among human leukocytes and leukemia cells

Anti-SSEA-1 which binds to glycoconjugates with a Gal beta 1-4(fuc alpha 1-3)GlcNAc epitope and VIM-2 which binds to gangliosides with a NeuAc alpha 2-3GlcNAc beta-4(FUC alpha 1-3) GlcNAc beta 1-3Gal-epitope were used to determine the expression of their corresponding carbohydrate antigens in human leukocytes and leukemia cells. Expression of these antigens was evaluated by immunohistochemical staining of plastic embedded sections of bone marrow or isolated cells, and by immunostaining of isolated glycosphingolipids separated by thin layer chromatography. The expression of both antigens was restricted to normal and leukemic myeloid cells. A range of positive immunohistochemical staining was found among normal marrow myeloid precursors, with myeloblasts giving weaker staining than more mature cells (promyelocytes, myelocytes, metamyelocytes). A similar trend was observed with leukemia cell lines, in that the myeloblastic cell line KG1 was weakly stained compared to the partially differentiated cell line HL-60. Immunohistochemical staining of marrows from acute leukemia patients showed that the VIM-2 antigen is more strongly expressed than the SSEA-1 antigen. Interestingly, both antibodies stained AMMoL cells more intensely than AML cells. Granulocytes from marrows of chronic myelogenous leukemia (CML) patients were intensely stained by both antibodies, whereas lymphocytic leukemias (acute lymphocytic, chronic lymphocytic and hairy cell marrows) were negative. Thus, although both antigens are restricted to myeloid cells there are differences in the level of expression depending on the level of cell maturity. Immunostaining of glycosphingolipids isolated from myeloid cells demonstrated that the SSEA-1 epitope is carried by several neutral glycosphingolipids and that the VIM-2 epitope is carried by three or more gangliosides. Major SSEA-1 glycosphingolipids, with seven to more than ten monosaccharides, are expressed by all myeloid cells regardless of the level of maturity, although quantitative differences are apparent in different patient samples. Two strongly immunoreactive VIM-2 gangliosides with ten and twelve monosaccharides, respectively were found in myeloid cells. The ratio of these two gangliosides varied dramatically, with greater amounts of the more complex ganglioside being present in most cell samples. Normal neutrophils and CML cells had much greater quantities of the VIM-2 gangliosides than acute leukemia cells. This observation correlates with our earlier findings that: (1) acute leukemia cells have less total ganglioside than granulocytes and (2) acute leukemia cells have a predominance of short chain gangliosides (i.e. less than five monosaccharide units). Finally, both CML cells and normal neutrophils express a shorter chain VIM-2 ganglioside, which was not detected in acute myelogenous leukemia cells.

The tissue distribution of the 3 alpha-fucosyl-N-acetyl lactosamine determinant recognized by the CD15 monoclonal antibodies CMRF-7 and 27

Two monoclonal antibodies, CMRF-7 and 27, which react with cells of the granulocytic series, were obtained from hybridomas cloned from separate fusions. Biochemical studies indicate that both antibodies are of the CD15 group and react with the antigenic determinant 3 alpha-fucosyl-N-acetyl lactosamine (hapten X) expressed on some glycolipids and several different granulocyte glycoproteins with a wide range of molecular weights. The antigen was found on some promyelocytes and more differentiated granulocytes, including neutrophils and some eosinophils, but not basophils. Monocytes, lymphocytes, and erythrocytes were negative for CMRF-7 but neuraminidase treatment revealed "cryptic" sites on monocytes and some lymphoid cells. The antibody CMRF-7 reacted with the majority of acute myeloid leukemia blasts in the FAB categories M2-M5 but less frequently with M1 blasts and was positive with only 5/43 acute lymphoid leukemias. Immunoperoxidase staining of other normal human tissues indicates that this determinant is found on a range of epithelial cells in skin, the gastrointestinal tract and the genitourinary system. In addition some parts of the central nervous tissue and some endocrine organs stained with these antibodies.

A mucin containing the X, Y, and H type 2 carbohydrate determinants is shed by carcinoma cells

Monoclonal antibody BR 15-6A directed to the Y carbohydrate determinant (Fuc alpha 1----2Gal beta 1----4GlcNAc(3----1Fuc) beta 1----3Gal beta 1----4Glc beta 1----1Cer) reacted with the cell surface and conditioned media of colorectal and breast carcinoma cell lines. Double determinant immunoassays using BR 15-6A as detector antibody showed that the Y determinant is part of a high molecular weight mucin that coexpressed other carbohydrate antigens based on a type 2 chain (X, H type 2). Type 1 chain carbohydrates such as sialylated Lewisa, Lewisa and Lewisb blood group antigens were predominantly expressed on a separate mucin molecule as determined by double-determinant immunoassays with other anticarbohydrate monoclonal antibodies. The X, Y, and H type 2-bearing mucin was present in conditioned media of the majority of colorectal carcinoma cell lines and in all three breast cancer cell lines tested. Thus, monoclonal antibodies against X, Y, and H type 2 determinants are potentially useful in the serodiagnosis of gastrointestinal and breast cancer.

Carbohydrates as antigenic determinants of glycoproteins

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Sulphate groups are involved in the antigenicity of keratan sulphate and mask i antigen expression on their poly-N-acetyllactosamine backbones. An immunochemical and chromatographic study of keratan sulphate oligosaccharides after desulphation or nitrosation

Conditions were established for desulphation of hexa-, octa-, deca- and larger oligosaccharides derived from corneal keratan sulphate after treatment with endo-beta-galactosidase. The antigenicities of the desulphated oligosaccharides were compared with those of the native oligosaccharides in chromatogram binding, plastic-plate binding or inhibition of binding assays using a novel microimmunochemical approach with oligosaccharide-lipid conjugates (neoglycolipids). The results clearly show that sulphate residues are essential components of the antigenic determinant(s) recognised by three monoclonal antibodies to keratan sulphate, 5-D-4, 1-B-4 and MZ15, but they mask the i antigen activity of the linear poly-(N-acetyllactosamine) backbones of this glycosaminoglycan. Immunochemical assays, before and after beta-N-acetylglucosaminidase treatment of desulphated linear hexa-, octa- and decasaccharides derived from keratan sulphate, indicate that for reaction with one anti-i antibody, Den, there is an absolute requirement for the non-reducing beta-galactosyl residue of the i antigen structure to be in the terminal position, but with a second anti-i antibody, Tho, there is in addition some reactivity with the i antigen structure having an N-acetylglucosamine residue at the non-reducing end. The chromatographic properties after desulphation or nitrosation of a minor keratan sulphate oligosaccharide (a dodecasaccharide), which reacts especially well with antibody 5-D-4, have provided the first evidence for the presence of glucosamine residues that may be N-sulphated in corneal keratan sulphate.

Glycosphingolipid immunostaining: detection of antibody binding with an avidin-biotin enzyme system

Glycosphingolipids carrying carbohydrate sequences recognized by antibodies and lectins can be detected on thin layer chromatograms using an avidin-biotin enzyme system (ABC reagents). This same method can be used to detect glycosphingolipids blot-transferred from thin layer chromatograms to nitrocellulose. This method has certain advantages over the original radioimmunoassay method, including development of positive bands in minutes after incubation with the substrate, avoidance of handling hazardous radioactive materials and stability of reagents. We have demonstrated the usefulness of this method for immunostaining glycosphingolipids with both monoclonal and polyclonal anti-carbohydrate antibodies. These reagents have previously been used to detect carbohydrate antigens in tissues and isolated cells and now it is possible to use the same reagents for the detection of glycosphingolipid antigens on chromatograms.

Association of the Y hapten with glycoproteins, glycolipids and carcinoembryonic antigen in colorectal carcinoma

The expression of the Y hapten (Fuc alpha 1----2Gal beta 1----4[Fuc alpha 1----3]GlcNAc-) defined by the monoclonal antibody C14/1/46/10 (abbreviated to C14), is frequently elevated in colo-rectal tumours in comparison to adjacent, apparently normal tissues. This determinant was shown to be expressed upon glycoproteins of approximately 200 kDa, which were isolated by immunoadsorbent chromatography from detergent-solubilized subcellular membranes and cytosol from colo-rectal carcinoma. In addition, the Y hapten was expressed upon purified carcinoembryonic antigen (CEA, 180 kDa). However, monoclonal antibodies specifically reactive with CEA or cross-reactive with CEA and NCA-1 (normal cross-reacting antigen) failed to react with the C14 defined antigens of 200 kDa. Further diversity in the expression of molecules bearing the Y hapten was established following its identification in the glycolipid fraction of colo-rectal carcinoma.

Biosynthesis of glycosphingolipids by human myeloid leukemia cells

We have performed comparative studies of the neutral glycosphingolipids synthesized by three human myeloid leukemia cell lines, K562, KG1, and HL-60, which were metabolically labeled with [14C]galactose, to evaluate changes in neutral glycosphingolipid synthesis with myeloid cell differentiation. Individual neutral glycosphingolipids containing one to four sugars were purified by a combination of the following methods: diethylaminoethyl-Sephadex column chromatography, acetylation-Florisil column chromatography, and high-performance liquid chromatography using an Iatrobead column. Compounds with one sugar were analyzed by thin-layer chromatography on borate plates. This analysis showed that HL-60 cells synthesize only glucosylceramide, whereas K562 and KG1 cells synthesize predominately glucosylceramide, but also a small amount of galactosylceramide. Compounds with two to four sugars were characterized by treatment with exo- and endoglycosidases. The results showed that K562 and KG1 cells are similar to cells from patients with acute leukemia in expressing two series (globo and neolacto) of natural glycosphingolipids, whereas the HL-60 cells are similar to mature human myeloid cells in expressing only one series (neolacto). Therefore, human myeloid leukemia cells blocked at different stages of differentiation vary in their ability to synthesize neutral glycosphingolipids.