Structure elucidation of the blood group B like and blood group I active octaantennary ceramide tetracontasaccharide from rabbit erythrocyte membranes by two-dimensional 1H NMR spectroscopy at 600 MHz

Carbohydrate-mediated binding and induction of acrosomal exocytosis in a boar sperm-somatic cell adhesion model

The molecular basis underlying the binding of spermatozoa to their homologous eggs and the subsequent induction of acrosomal exocytosis remain a major unresolved issue in mammalian fertilization. Novel cell adhesion systems are now being explored to advance this research. Triantennary and tetraantennary N-glycans have previously been implicated as the major carbohydrate sequences that mediate the initial binding of spermatozoa to the specialized egg coat (zona pellucida) in the murine and porcine models. Mouse spermatozoa also undergo binding to rabbit erythrocytes (rRBCs), presumably via the interaction of their lectin-like egg-binding proteins with branched polylactosamine sequences present on these somatic cells. Experiments presented in this study confirm that boar spermatozoa also bind to rRBCs. However, unlike mouse spermatozoa, boar spermatozoa also undergo acrosomal exocytosis within 30 min after binding to rRBCs. Both binding and induction of acrosomal exocytosis in this system did not require the participation of terminal Galalpha1-3Gal sequences that are found on rRBCs. Pronase glycopeptides derived from rRBCs inhibited the binding of boar sperm to porcine oocytes by 91% at a final concentration of 0.3 mg/ml under standard IVF conditions. Binding in this porcine cell adhesion model was also completely blocked at this concentration of glycopeptide. Thus, adhesion results from the interaction of the egg-binding protein expressed on the surface of boar spermatozoa with the glycans presented on rRBCs. This cell adhesion model will be useful for investigating the molecular basis of gamete binding and the induction of acrosomal exocytosis in the pig.

Identification of a GH110 subfamily of alpha 1,3-galactosidases: novel enzymes for removal of the alpha 3Gal xenotransplantation antigen

In search of alpha-galactosidases with improved kinetic properties for removal of the immunodominant alpha1,3-linked galactose residues of blood group B antigens, we recently identified a novel prokaryotic family of alpha-galactosidases (CAZy GH110) with highly restricted substrate specificity and neutral pH optimum (Liu, Q. P., Sulzenbacher, G., Yuan, H., Bennett, E. P., Pietz, G., Saunders, K., Spence, J., Nudelman, E., Levery, S. B., White, T., Neveu, J. M., Lane, W. S., Bourne, Y., Olsson, M. L., Henrissat, B., and Clausen, H. (2007) Nat. Biotechnol. 25, 454-464). One member of this family from Bacteroides fragilis had exquisite substrate specificity for the branched blood group B structure Galalpha1-3(Fucalpha1-2)Gal, whereas linear oligosaccharides terminated by alpha1,3-linked galactose such as the immunodominant xenotransplantation epitope Galalpha1-3Galbeta1-4GlcNAc did not serve as substrates. Here we demonstrate the existence of two distinct subfamilies of GH110 in B. fragilis and thetaiotaomicron strains. Members of one subfamily have exclusive specificity for the branched blood group B structures, whereas members of a newly identified subfamily represent linkage specific alpha1,3-galactosidases that act equally well on both branched blood group B and linear alpha1,3Gal structures. We determined by one-dimensional (1)H NMR spectroscopy that GH110 enzymes function with an inverting mechanism, which is in striking contrast to all other known alpha-galactosidases that use a retaining mechanism. The novel GH110 subfamily offers enzymes with highly improved performance in enzymatic removal of the immunodominant alpha3Gal xenotransplantation epitope.

Analysis of protein-linked glycosylation in a sperm-somatic cell adhesion system

Murine sperm initiate fertilization by binding to the specialized extracellular matrix of their complementary eggs, known as the zona pellucida. On the basis of data reported in this study, mouse sperm also bind to rabbit erythrocytes with higher affinity than they do to murine eggs. This unusual interaction between a germ cell and a somatic cell ("sperm-somatic cell adhesion system") is also carbohydrate dependent based on its sensitivity to mild periodate oxidation. To determine what types of carbohydrate sequences could be involved in this interaction, the protein-linked oligosaccharides of rabbit erythrocytes were sequenced using novel matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry methods that enabled the analysis of individual components up to m/z 9000. The N-glycans are primarily complex biantennary and triantennary types terminated with Galalpha1-3Gal sequences. The majority of these oligosaccharides also possess one antenna consisting of a highly branched polylactosamine-type sequence that is also associated with many glycosphingolipids that coat rabbit erythrocytes. These erythrocytes also express Core 1 and Core 2 O-glycans terminated primarily with Galalpha1-3Gal sequences and to a lesser extent sialic acid. These results confirm that rabbit erythrocytes and mouse eggs present very different types of carbohydrate sequences on their surfaces. However, oligosaccharides terminated with beta1-6-linked N-acetyllactosamine or its alpha1-3 galactosylated analog are expressed on both the mouse zona pellucida and this somatic cell type. The far more abundant presentation of such sequences on rabbit erythrocytes compared with murine eggs could explain why mouse sperm display such exceptional affinity for this somatic cell type.

Molecular Models for Murine Sperm-Egg Binding

Murine sperm initiate fertilization by binding to the specialized extracellular matrix of mouse eggs, known as the zona pellucida. Over the past decade, powerful genetic, biophysical, and biochemical techniques have been employed to gain new insights into this interaction. Evidence from these studies does not support either of two major models for binding first proposed over two decades ago. Two more recently established models suggest that protein-protein interactions predominate during this initial stage of fertilization. Another model proposes that about 75-80% of the murine sperm bound to zona pellucida under well defined in vitro conditions is carbohydrate dependent, with the remaining sperm bound via protein-protein interactions. Mounting evidence suggests that the carbohydrate sequences coating the murine egg could be employed as specific immune recognition markers. Continued investigation of this system may resolve many of these controversial findings and reveal novel functions for murine zona pellucida glycoproteins.

Polyglycosylceramides recognized by Helicobacter pylori: analysis by matrix-assisted laser desorption/ionization mass spectrometry after degradation with endo-beta-galactosidase and by fast atom bombardment mass spectrometry of permethylated undegraded material

Human erythrocyte polyglycosylceramides (PGCs) are recognized by the gastric pathogen Helicobacter pylori and are based on a successively extended and highly branched N-acetyllactosamine core linked to ceramide and substituted by fucose and sialic acid. As a step in the identification of the binding epitope we earlier characterized intact PGCs by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, MALDI-TOF MS (Karlsson,H., Johansson,L., Miller-Podraza,H., and Karlsson,K-A. [1999] Glycobiology, 9, 765-778). In the present work, PGCs from human blood group O erythrocytes were digested with endo-ss-galactosidase (Bacterioides fragilis), an enzyme which cleaves the bond 3Galss1-4GlcNAc in linear but not branched poly-N-acetyllactosamine chains. The enzymatic digestion resulted in a mixture of neutral and sialic acid-containing glycolipids together with terminal and internal sequences of mainly neutral oligosaccharides. The products were analyzed by MALDI-TOF MS in both positive and negative ion mode which gave spectra where the ions could be assigned to structures of the neutral and acidic components, respectively. Among glycolipids found were [structure in text] where R could be H, Fuc or NeuAc. Also observed were structures as [structure in text] which indicated linear extension along both branches. Observed at higher masses were fully branched structures obtained by stepwise extension with [structure in text] where R could be H, Fuc or NeuAc. Most probably further branching may occur along both the (1-->3)- and the (1-->6)-linked branches to give a partly dendritic structure. Structures with more than one sialic acid substituted could not be observed in the MALDI spectrum. Complementary information of the terminal sequences was obtained by FAB-MS analysis of permethylated undegraded PGCs. High-temperature gas chromatography/mass spectrometry of reduced and permethylated products from enzyme hydrolysis documented that Fuc was present in a blood group O sequence, Fuc-Hex-HexN-. Fucose may be placed on short (monolactosamine) or longer branches, while sialic acid seems to be restricted to monolactosamine branches. The conclusion is that human erythrocyte PGCs display microheterogeneity within terminal and internal parts of the poly-N-acetyllactosamine chains. The first branch from the ceramide end may be located at the second or third Gal and possibly also on the first Gal. Other branches may occur on every N-acetyllactosamine unit in fully branched domains, or there may be linear extensions between branches resulting in incompletely branched structures. The extended linear sequences may be present in both 3- and 6-linked antennae. Terminal structures are based on one, two or maybe higher number of N-acetyllactosamine units.

Neu5Acalpha3Gal is part of the Helicobacter pylori binding epitope in polyglycosylceramides of human erythrocytes

The sialic acid dependent binding by the human pathogen Helicobacter pylori to polyglycosylceramides of human erythrocytes was investigated. Polyglycosylceramides, complex glycosphingolipids with a branched N-acetyllactosamine core, were isolated from human erythrocytes, blood group O, and subfractionated after peracetylation by anion-exchange chromatography. Three subfractions were deacetylated, analysed by matrix-assisted laser desorption ionization-time of flight MS and 2D 1H NMR spectroscopy. The observed mass ranges were m/z = 3093-7622, 3968-7255 and 3459-7987 in the mass spectra of the first, second and third fractions, respectively. The observed ions agreed with the general formula Hex(x+2)HexNAcxFucyNeu5AczCer. Two-dimensional 1H total correlation spectra of the mixtures showed that the first fraction contained 3-linked sialic acid and the second and third fractions contained both 3-linked and 6-linked sialic acid. Thin-layer chromatogram binding assays using the lectins from Maackia amurensis, specific for Neu5Acalpha3Galbeta4GlcNAc, and Sambucus nigra, specific for Neu5Acalpha6Gal/GalNAc, were used to confirm this distribution. H. pylori recognized all three fractions in the binding assay, indicating that the 3-linked, rather than 6-linked, sialic acid is essential for binding.

Fingerprinting of large oligosaccharides linked to ceramide by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: highly heterogeneous polyglycosylceramides of human erythrocytes with receptor activity for Helicobacter pylori

Highly microheterogeneous polyglycosylceramides (PGCs) of human erythrocytes with an average composition of about 25 monosaccharides linked to ceramide were analyzed by matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS). The human gastric pathogen Helicobacter pylori was earlier shown to bind this glycosphingolipid mixture by thin-layer chromatogram binding assay. The receptor activity was present along the whole nonresolved chromatographic interval. Mass spectra of intact PGCs were compared with corresponding spectra of oligosaccharides enzymatically released from the ceramides. Two subfractions of PGCs containing less than one and more than one sialic acid residue per molecule were used. MALDI-MS spectra were recorded in both linear and reflectron mode with the accuracies of </=0.08% and </=0.02%, respectively, which allowed determination of the constituent parts of the detected ions in form of ceramide and number of hexoses, N-acetylhexosamines, fucoses and sialic acids. Molecular species were found based on ceramide with mainly sphingosine and fatty acids 24:0 and 24:1 (with less amounts of 22:0), and with a total number of monosaccharides ranging from 11 (neutral, m/z = 2605 for [M+Na](+)) to 41 (one sialic acid, m/z = 8057 for [M-H](-)). The saccharide composition obtained supported a successively extended and branched N -acetyllactosamine core with substitutions of fucoses (0 up to 8) and sialic acid (0 to 1). The reliable molecular analysis of large oligosaccharides linked to ceramide using this approach will be of great help for the further structure analysis in order to define the epitope for the sialic acid-dependent binding by the bacterium.

alpha-Gal epitopes in animal tissue glycoproteins and glycolipids

alpha-Gal terminated saccharides are present on the cell surface both as glycolipids and glycoproteins in all mammals except Old World monkeys and humans. The structural diversity among identified saccharides terminated by this epitope in animal tissues is steadily increasing. The majority of these saccharides have the alpha-Gal linked to lactosamine but other core saccharides exist. The alpha-Gal terminated saccharides are recognized by the immune system as a specific antigen and antibodies directed to the alpha-Gal, which do not cross-react with the classic blood group B trisaccharide, are found in man and Old World monkeys. Similar to other complex carbohydrate cell surface antigens, the alpha-Gal epitope is heterogeneously distributed in different organs and in different cells within an organ. It is present on the vascular endothelium and it is the primary target for human naturally occurring antibodies following pig to primate/man xenotransplantation leading to hyperacute rejection of the graft. Important for the future will be to further structurally characterize this antigen system, its cellular/subcellular distribution, and to identify possible of additional glycosyltransferases, related to the already described alpha 1,3galactosyltransferase that may explain the structural diversity. Such information will be of importance in the studies of, for example, the pathogenesis of autoimmune diseases and for the production of genetically modified pigs to prevent xenograft rejection.

An ELISA technique for quantitation of human xenoantibodies binding to pig cells: application in patients with pig kidneys extracorporeally connected to the circulation

A quantitative ELISA technique for determination of human anti-pig xenoantibody number in serum samples has been established using pig lymphocytes and pig/rabbit erythrocytes as target cells and a pool of serum from human blood group AB donors. The number of low affinity antibodies binding to the cells was determined by quantitation following the use of aqueous washing of the cells and separation of bound and unbound antibodies with the phthalate oil method. The efficiency of different soluble Gal(alpha)1-3Gal-terminating di- and tri-saccharides to inhibit antibody binding was tested and found to vary between 70-90% at a saccharide concentration of 10 mg/ml. The assay was used to evaluate the antibody changes in two patients who, after plasmapheresis treatments, had pig kidneys extracorporeally connected to their blood circulation. The number of anti-pig IgM/IgG antibodies bound to each pig lymphocyte were reduced from 5,600/13,200 to 1,300/3,100 in patient 1 and from 1,200/6,500 to 500/2,100 in patient 2 by three consecutive daily plasmapheresis treatments. Although the lymphocytotoxic titers were reduced to very low levels, the antibody numbers still present in the blood of patient 1 caused a hyperacute rejection of the pig kidney. However, the antibody levels in patient 2 did not cause rejection of this kidney during 15 min perfusion time. A strong anti-pig antibody response 3 weeks after the perfusion experiment was found in patient 1 as shown by 27,600/245,300 IgM/IgG molecules bound to pig lymphocytes corresponding to an increase of lymphocytotoxic titer from 8 to 512. The second patient showed a much weaker immune response with 1,400/19,800 IgM/IgG antibodies corresponding to a lymphocytotoxic titer increase from 8 to 32. The use of this quantitation technique enables more accurate investigation of antibody binding to xenogenic target cells than conventional titration techniques.

Screening for the presence of polyglycosylceramides in various tissues: partial characterization of blood group-active complex glycosphingolipids of rabbit and dog small intestines

Twenty different human and animal tissues were investigated for the presence of polyglycosylceramides. The glycolipids were isolated by peracetylation of dry tissue residues left after conventional lipid extraction, followed by extraction with chloroform and subsequent Sephadex LH-20, Sephadex LH-60 and silica gel chromatography. In most of the cases only trace amounts of complex glycolipids were found. Distinct bands of glycosphingolipids migrating on TLC plates in a region of brain gangliosides and below were observed in bovine erythrocytes, human leukocytes and human colon mucosa. Definite fractions of polyglycosylceramides were isolated from rabbit small intestine, dog small intestine, human placenta and human leukocytes. The polyglycosylceramides of dog and rabbit intestine were characterized by colorimetric analysis, methylation analysis, mass spectrometry and immunological assays. The dog material contained branched carbohydrate chains with repeated fucosylated N-acetyllactosamine units. Rabbit intestine polyglycosylceramides resembled rabbit erythrocyte polyglycosylceramides with Hex-Hex- terminal determinants but were more complex in respect of sugar composition and structure. The material isolated from dog intestine showed A, H, Le(x) and Le(y) blood group activities. Polyglycosylceramides of human erythrocytes, placenta and leukocytes showed strong binding affinity for Helicobacter pylori, while polyglycosylceramide fractions from rabbit and dog intestine were receptor-inactive for this bacterium or displayed only weak and poorly reproducible binding.

New method for the isolation of polyglycosylceramides from human erythrocyte membranes

A new procedure was developed for the isolation of long-chain, highly polar glycosphingolipids from human erythrocytes. The membrane material left after extraction of membrane lipids with organic solvents was peracetylated in a mixture of formamide, pyridine and acetic anhydride, and the acetylated products were then extracted with chloroform. The material was fractionated and purified by means of Sephadex LH-20, Sephadex LH-60 and silica-gel chromatography. The final preparations were mixtures of highly polar glycosphingolipids containing from 7 to 31 sugar residues relative to sphingosine. GC-MS analysis of the sugar part of the isolated fractions showed the presence of branched polyglycosyl chains of N-acetyllactosaminyl type. Endo-beta-galactosidase (Bacteroides fragilis) liberated from the deacetylated material two glycosphingolipids, which were identified by fast atom bombardment-mass spectrometry as Hex-Cer and HexNAc-Hex-Hex-Cer with sphingosine and mainly 24 and 22 carbon fatty acids. Endoglycoceramidase (Rhodococcus) degraded polyglycosylceramides to free ceramides and free polysaccharides. The released sugars were fractionated by high-pH ion-exchange chromatography into fractions differing in sialic acid content. The procedure presented in this paper can be used for large and small scale preparations of complex glycosphingolipids. It proved to be especially suitable for screening for polyglycosylceramides in different tissues.

Elongation of both branches of biantennary backbones of oligo-(N-acetyllactosamino)glycans by human serum (1----3)-N-acetyl-beta-D- glucosaminyltransferase

Partial reactions catalyzed by a (1----3)-N-acetyl-beta-D- glucosaminyltransferase (EC2.4.1.149), known to be present in human serum, were studied by use of biantennary "backbone" saccharides of oligo-N-acetyllactosamine-type as acceptors. Incubation of the radiolabeled blood-group I-active hexasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-Galp- (1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Galp-(1----4)-D-GlcNAc (1) and UDP-GlcNAc with serum gave first a transient 1:1 mixture of two isomeric heptasaccharides, beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D- GlcpNAc-(1----3)-[beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D- Galp-(1----4)-D-GlcNAc (2) and beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-GlcpNAc-(1----3)- beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Galp-(1----4)-D-Glc NAc (3), showing that both branches of 1 react equally well. The two heptasaccharides reacted further in the incubation mixture to form the radiolabeled octasaccharide, beta-D-GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[be ta-D- GlcpNAc-(1----3)-beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)]-beta-D-Ga lp- (1----4)-D-GlcNAc (4); during this second reaction, the composition of the heptasaccharide mixture remained unchanged, indicating that 2 and 3 reacted at approximately equal rates. The heptasaccharides 2 and 3 could not be separated from each other, but they could be detected, identified, and quantitatively determined by stepwise enzymic degradations. Partial (1----3)-N-acetyl-beta-D-glucosaminylation reactions, carried out with another acceptor, the branched pentasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----3)-[beta-D-Galp-(1----4)-beta- D- GlcpNAc-(1----6)]-beta-D-Gal (11), revealed that it reacted also equally well at both branches.(ABSTRACT TRUNCATED AT 400 WORDS)

1H NMR studies of a biosynthetic lacto-ganglio hybrid glycosphingolipid: confirmation of structure, interpretation of "anomalous" chemical shifts, and evidence for interresidue amide-amide hydrogen bonding

Glycosphingolipids bearing GlcNAc beta 1----3 and GalNAc beta 1----4 linked to beta-Gal of lactosylceramide (lacto-ganglio hybrids), first isolated from a murine myelogenous leukemia cell line [Kannagi, R., Levery, S. B., & Hakomori, S. (1984) J. Biol. Chem. 259, 8444-8451], have since been found as normal components of mullet roe and English sole liver. In order to clarify the biosynthetic pathways responsible for its occurrence both as a product of normal tissues and as a possible mammalian cancer-associated antigen, the lacto-ganglio hybrid core structure LcGg4Cer was synthesized from Lc3Cer using a GalNAc beta 1----4 transferase preparation from English sole liver. A preliminary characterization of the enzyme, which may be identical to the GalNAc T-1 responsible for synthesis of GM2 ganglioside, is presented. The enzymatically synthesized product was analyzed by 1- and 2-D 1H NMR spectroscopy, confirmining its primary structure as GalNAc beta 1----4-(GlcNAc beta 1----3)Gal beta 1----4Glc beta 1----1Cer. In addition to assigning all nonexchangeable glycosyl proton resonances, measurements of several properties of the amide NH protons, including chemical shift, coupling constants, exchange rates, and temperature shift coefficients, were obtained and compared to those in the simpler constituent triglycosylceramides, Lc3- and Gg3Cer. An approximate three-dimensional structure for LcGg4Cer is proposed, consistent with all data obtained, which should be useful in discussing the results of 1H NMR analysis of compounds containing this core tetrasaccharide. The structure is characterized by an unusual arrangement of terminal N-acetylhexosamine residues, resulting in a pi-H hydrogen-bonding interaction between their acetamido groups.

O-specific polysaccharides of Hafnia alvei lipopolysaccharides isolated from two serologically related strains: ATCC 13337 and 1187. A serological and structural study using chemical methods, gas chromatography/mass spectrometry and NMR spectroscopy at 500 MHz

The O-specific polysaccharides of Hafnia alvei ATCC 13337 standard strain and 1187 strain have been isolated and characterized. By means of 1H-NMR spectroscopy, methylation analysis and periodate oxidation, the repeating unit of the polysaccharides could be allocated the respective structures. (formula; see text) where Acyl = D-3-hydroxybutyryl, and 3-O-acetylation was to about 66%. The structural similarity of the polysaccharides was confirmed in the serological study; their epitopes were determined and the importance of various structural elements for the serological specificity was discussed.

Novel tri-and tetrasialosylpoly-N-acetyllactosaminyl gangliosides of human placenta: structure determination of pentadeca- and eicosaglycosylceramides by methylation analysis, fast atom bombardment mass spectrometry, and 1H NMR spectroscopy

A series of highly polar neolacto series (poly-N-acetyllactosaminyl) gangliosides were isolated from human placenta tissue and purified by HPLC and preparative HPTLC. Two of these ganglioside fractions (G-12 and G-13) were analyzed by 500-MHz 1H NMR spectroscopy, GC-EIMS, +FAB-MS, and sequential exoglycosidase treatments. Their structures have been identified as being of the repeating N-acetyllactosamine type, multiply branched through GlcNAc beta 1----6/3 linkages, with every nonreducing Gal terminal alpha 2----3-sialosylated, as shown below. These are among the highest molecular weight glycosphingolipids whose detailed oligosaccharide structures are presently known. (formula; see text).

ABH and related histo-blood group antigens; immunochemical differences in carrier isotypes and their distribution

This review summarizes present knowledge of the chemistry of histo-blood group ABH and related antigens. Recent advances in analytical carbohydrate chemistry (particularly mass spectrometry and NMR spectroscopy) and the introduction of monoclonal antibodies (MoAbs) have made it possible to distinguish structural variants of histo-blood group ABH antigens. Polymorphism of ABH antigens is induced by: (i) variations in peripheral core structure, of which four (type 1, 2, 3 and 4) are known in man; (ii) variation in inner core by branching process (blood group iI), leading to variation of unbranched vs. branched ABH determinants; (iii) biosynthetic interaction with other glycosyltransferases (Lewis, P. T/Tn blood systems) capable of acting on the same substrate as the ABH-defined transferases, and finally (iv) the nature of the glycoconjugate (glycolipid, glycoprotein of N- or O-linked type). ABH variants induced by item (i) above have been clearly distinguished qualitatively by MoAbs; e.g., at least six types of A determinants can be distinguished by qualitatively different classes of antibody. The variants induced by item (ii) create mono- vs. bivalent antigens which may be responsible for observed differences in antibody-binding affinity. Detailed studies of the chemistry of these antigens have increased our insight into blood groups, providing the basis for blood group iI and A subgrouping, as well as a relation between the ABH and Lewis, P, and T/Tn systems. A survey of the literature on distribution patterns of ABH variants is presented. It has been assumed that expression of histo-blood group antigens is developmentally regulated. Relationships between histo-blood group expression, development, differentiation and maturation, as well as malignant transformation, are discussed.