Variant forms of?-2-l-fucosyltransferase in human submaxillary glands from blood group ABH ?secretor? and ?non-secretor? individuals

Human milk oligosaccharides and Lewis blood group: individual high-throughput sample profiling to enhance conclusions from functional studies

Human milk oligosaccharides (HMO) are discussed to play a crucial role in an infant's development. Lewis blood group epitopes, in particular, seem to remarkably contribute to the beneficial effects of HMO. In this regard, large-scale functional human studies could provide evidence of the variety of results from in vitro investigations, although increasing the amount and complexity of sample and data handling. Therefore, reliable screening approaches are needed. To predict the oligosaccharide pattern in milk, the routine serological Lewis blood group typing of blood samples can be applied due to the close relationship between the biosynthesis of HMO and the Lewis antigens on erythrocytes. However, the actual HMO profile of the individual samples does not necessarily correspond to the serological determinations. This review demonstrates the capabilities of merging the traditional serological Lewis blood group typing with the additional information provided by the comprehensive elucidation of individual HMO patterns by means of state-of-the-art analytics. Deduced from the association of the suggested HMO biosynthesis with the Lewis blood group, the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry profiles of oligosaccharides in individual milk samples exemplify the advantages and the limitations of sample assignment to distinct groups.

Ethnic differences in the expression of blood group antigens in the salivary gland secretory cells from German and Japanese non-secretor individuals

Type 1 ABO blood group antigens (peripheral core structure: Gal beta 1-3GlcNAc beta 1-R) are expressed mainly in endodermally-derived tissues, but are not synthesized in mesodermally-derived tissues. In the former tissues, H type 1 antigen is generated largely by alpha-2-L-fucosyltransferase encoded by secretor (Se) gene and acting on the terminal galactose of the type 1 precursor chain. This theory has been generally accepted, and it seems that the expression of ABO blood group antigens is absent, or expressed at a low level, in these tissues from non-secretor individuals. In this immunohistochemical study on the secretory cells of salivary glands, we found ethnic difference between German and Japanese non-secretor individuals in the expression of blood group antigens: i.e. the expression of the type 1 blood group antigens is present in these cells from Japanese non-secretor individuals but absent from German. A possible explanation is that another alpha-2-L-fucosyltransferase, independent of the secretor gene, is present in Japanese non-secretor individuals.

Porcine submaxillary gland GDP-L-fucose: beta-D-galactoside alpha-2-L-fucosyltransferase is likely a counterpart of the human Secretor gene-encoded blood group transferase

Partial amino acid sequence of GDP-L-fucose:beta-D-galactoside alpha-2-L-fucosyltransferase purified from porcine submaxillary glands was determined. Amino acid sequence analysis yielded 100, 93.3, and 84.2%, and 75, 46.6, and 84.2% sequence identity between 12-, 15-, and 19- amino acid tryptic peptides generated from porcine enzyme and amino acid residues 61-72, 111-125, and 308-326 and 89-100, 139-153, and 338-356 of the human Secretor and H type alpha-2-fucosyltransferases, respectively. Higher amino acid sequence homology of the porcine enzyme with the predicted sequence for the human Secretor locus as compared with H gene-encoded blood group beta-D-galactoside alpha-2-L-fucosyltransferase suggests that porcine alpha-2-fucosyltransferase highly corresponds to the human Secretor gene-encoded enzyme.

Quantitative analysis of Le(a) and Le(b) antigens in human saliva

We have measured the H type 1, Le(a) and Le(b) antigens in the saliva from 129 Japanese individuals by a time-resolved europium ion fluorometric immunoassay using artificial antigen-albumin complexes as the reference substances. We confirmed that the amount of Le(b) was larger than that of Le(a) in the saliva from secretors (Le(a-b+)) and vice versa in the saliva from nonsecretors (Le(a+b-)). Unexpectedly, we discovered appreciable amounts of Le(b) with small amounts of H type 1 in the saliva from the nonsecretors. The concentration of Le(b) was about 10, 6 and 35% of the concentration of the Le(a) in the saliva from the nonsecretors of the A, B and O groups, respectively. The possible formation of Le(b) from Le(a), in addition to the formation of Le(b) from H type 1, in the salivary glands is discussed.

Blood group antigens on human erythrocytes-distribution, structure and possible functions

Human erythrocyte blood group antigens can be broadly divided into carbohydrates and proteins. The carbohydrate-dependent antigens (e.g., ABH, Lewis, Ii, P1, P-related, T and Tn) are covalently attached to proteins and/or sphingolipids, which are also widely distributed in body fluids, normal tissues and tumors. Blood group gene-specific glycosyltransferase regulate the synthesis of these antigens. Protein-dependent blood group antigens (e.g., MNSs, Gerbich, Rh, Kell, Duffy and Cromer-related) are carried on proteins, glycoproteins and proteins with glycosylphosphatidylinositol anchor. The functions of these molecules on human erythrocytes remain unknown; some of them may be involved in maintaining the erythrocyte shape. This review describes the distribution, structures and probable biological functions of some of these antigens in normal and pathological conditions.

Recognition of synthetic analogues of the acceptor, beta-D-Gal p-OR, by the blood-group H gene-specified glycosyltransferase

The acceptor-substrate specificity of a cloned alpha-(1-->2) fucosyltransferase has been explored using structural analogues of octyl beta-D-galactopyranoside (4). This monosaccharide is the minimum acceptor-substrate for the H-transferase, one of two enzymes responsible for the biosynthesis of the O blood-group antigen, which terminates in the sequence alpha-L-Fuc p-(1-->2)-beta-D-Galp. Galactoside 4 has a Km of 6 mM with this enzyme. Eighteen analogues of 4 have been prepared, including those where the hydroxyl groups at C-3, C-4, and C-6 have been replaced, independently, with deoxy, fluoro, O-methyl, amino, and acetamido functionalities. The C-3 and C-4 epimers have been prepared as has the C-5 de(hydroxymethyl)ated derivative. These compounds were screened as potential acceptors and inhibitors of the fucosyltransferase. The C-6 analogues that do not possess a charge show substrate activity with relative rates in the range of 27-316% that of 4. The C-3 modified analogues are inhibitors with estimated Ki values of 0.9-43 mM. Those analogues with modifications at C-4 were both poor inhibitors and acceptors.

Mosaic differentiation of human villus enterocytes: patchy expression of blood group A antigen in A nonsecretors

BACKGROUND

The authors have shown that a mosaicism of brush border antigens may occur spontaneously on enterocytes of small intestine in human adult-type hypolactasia. The present paper gives another example of spontaneously occurring mosaicism as indicated by the patchy expression of blood group antigens on villus enterocytes.

METHODS

Thirty-five individuals were examined by immunomorphological techniques with antibodies against blood group antigens.

RESULTS

In 4 of 16 A blood group individuals, the blood group antigens were expressed only in some villus enterocytes. The individuals with this mosaic pattern were all shown to be nonsecretors. The A antigen in the positive enterocytes of these individuals was only present as the ALe(b) structure, whereas ALe(y) and ALe(d) were also present in the secretors. The patches of positive enterocytes were randomly distributed along the villus wall.

CONCLUSIONS

A nonsecretor individuals express the blood group antigens only in some villus enterocytes; this mosaicism does not arise from a heterogeneous population of stem cells within the crypts but rather reflects subtle differences in the pattern of differentiation between monoclonally derived epithelial cells on the villus.

Occurrence and specificities of α3-fucosyltransferases

The Le(x) (CD15) carbohydrate antigen and sialylated and oligomeric derivatives thereof have been implicated in cell adhesion processes. Expression of these antigens is developmentally regulated and (re)occurrence of several members of this group has been reported in malignant transformation of cells. Studies on the enzymology and genetics of alpha 3-fucosyltransferases, glycosyltransferases that play a key role in the biosynthesis of these antigens, would yield insight in the regulation of expression of these carbohydrate structures. In this paper the existing literature on these enzymes is reviewed and placed in the context of cell adhesion and malignancy.

Blood group non-secretors have an increased inflammatory response to urinary tract infection

The aim of this study was to assess the possible relationship between secretor state and the inflammatory response to urinary tract infection (UTI). Girls with recurrent UTI were prospectively studied. They included 61 secretor and 23 non-secretor individuals with 604 episodes of recurrent UTI. The response to each UTI episode was measured as the levels of C-reactive protein, erythrocyte sedimentation rate and the body temperature as well as renal concentrating capacity and pyuria. The levels of C-reactive protein, erythrocyte sedimentation rate and the body temperature were significantly higher in non-secretors than in secretors (p less than 0.04). As a consequence, non-secretors had an increased probability of being assigned a diagnosis of acute pyelonephritis rather than asymptomatic bacteriuria (p less than 0.05). The higher inflammatory response in non-secretors was independent of the Gal alpha 1-4Gal beta adhesin expression of the infecting Escherichia coli strains. The increased inflammatory response to UTI in non-secretors might explain the accumulation of these individuals among patients with renal scarring.

Histochemical and cytochemical localization of blood group antigens

The oligosaccharide structures of blood group antigens are not the primary gene products; they are constructed in a stepwise manner by adding particular sugar to precursor oligosaccharides via several glycosyltransferases coded for by different blood group genes (Watkins 1966, 1978, 1980). Consequently, final profiles of antigens expressed in each cell type are influenced by many different factors such as the intrinsic composition of glycosyltransferase species which are defined by the genotype of the individuals, relative activity or amount of these enzymes (repression, derepression or induction of the enzymes), competition between enzymes with overlapping substrate specificity, the organization of the enzymes in membranes, utilizability of precursors and specific substrate sugars, and the activity level of degradating enzymes. Changes in the antigen profiles during maturation, differentiation and malignant transformation are thought to be intimately related to the variability of these factors. Although great importance attaches to histo- and cytochemical information on the distribution and levels of glycosyltransferases and messenger RNA corresponding to the relevant enzyme, detailed and precise localization of the blood group antigens and their variants is the base line for analyzing these complex factors. On the basis of individual genotype and histochemical findings about the antigen distribution and the interrelationship between cells and cellular components producing different antigenic structures (cellular and subcellular mosaicism), we can deduce precursor oligosaccharide levels as well as the status of gene activation and its primary product, glycosyltransferases. Thus, these findings are a prerequisite for further analysis at the molecular genetic level. As emphasized in this article, lectin staining or immunostaining methods with MAbs combined with glycosidase digestion procedures are powerful tools for in situ analysis of carbohydrate structures in histochemical systems. Although in some cases valuable results have been obtained by applying the technique, our knowledge concerning the distribution of complex carbohydrate structures is still far from satisfactory. Along with well defined MAbs and lectins, the key to developing our methods further is successful introduction of glycosidases, in particular, endoglycosidases since these reagents are indispensable for analyzing the inner core structures and glycoconjugate species of the blood group antigens. Application of these techniques at the ultrastructural level is an alluring possibility, even though many difficulties must be overcome. Although their functional roles have not yet been determined, a diverse array of macromolecules is known to be decorated with blood group-related antigens.(ABSTRACT TRUNCATED AT 400 WORDS)

Lewis blood group antigens in salivary glands and stratified epithelium: lack of regulation of Lewis antigen expression in ductal and buccal mucosal lining epithelia

The expression of Lewis antigens is thought to be controlled by the Secretor and Lewis genes. While secretor status is known to regulate the expression of ABH antigens in many tissues, few studies have attempted to correlate Lewis antigen expression on erythrocytes and saliva with that of epithelial tissues. We examined the expression of Lewis a and b and related antigens in human epithelium of minor salivary glands and labial nonkeratinized oral mucosae from 16 individuals by immunohistology using monoclonal antibodies. The expression of these antigens, as detected by monoclonal antibodies (MAbs) used, was correlated with erythrocyte phenotype and saliva secretor status. In acinar cells of glands, Leb antigen was expressed only in secretors, and Lea only in nonsecretors. However, in gland ducts and oral mucosae, Leb was found in both secretors and nonsecretors, as well as in 2 cases of Lea-b-, secretors. Thus, antigen expression in acinar cells of minor salivary glands was correlated with the predicted genotypes, whereas inappropriate expression of Leb antigen was found in epithelial cells of gland ducts and oral mucosae. The present data indicate that the Lewis blood group phenotype is regulated differently in duct cells and stratified epithelium than in saliva and erythrocytes.

Structural characterization of sialylated tetrasaccharides and pentasaccharides with blood group H and Le(x) activity isolated from bovine submaxillary mucin

In this study we have investigated the structures of a sialylated tetrasaccharide and two sialylated pentasaccharides released from bovine submaxillary mucin by alkaline borohydride treatment and isolated by high-performance liquid chromatography. The tetrasaccharide contained NeuGc, while one of the pentasaccharides contained NeuAc and the other contained NeuGc. All three oligosaccharides contained the core type-3 structure (GlcNAc beta 1----3GalNAcol). The structures, determined by a combination of one- and two-dimensional 1H-NMR spectroscopy at 270 MHz and methylation analysis involving gas-liquid chromatography/mass spectrometry, were as follows: [formula: see text]. The oligosaccharides occurred in the approximate molar ratios, 1.0:0.6:0.3. This is the first report of these oligosaccharides in bovine submaxillary mucin. 1H-NMR data for structures A1/2c and A1/2e, which are novel structures, are presented for the first time. Oligosaccharide A1/2e contains the blood-group-H type-2 antigenic determinant while oligosaccharide A1/2d contains the Lewis(x) determinant.

Genetic control of the fucosylation of ABH precursor chains. Evidence for new epistatic interactions in different cells and tissues

The general structure of the ABH antigens is analysed taking into account six possible precursor chains and two alpha-2-fucosyltransferases. The classical genetic model with one structural gene and two regulatory genes for the synthesis of the H antigen and the events which prompted the proposal of the new model with two structural genes for the synthesis of H determinants are discussed. Three human alpha-3-fucosyltransferases with different acceptor specificity are presented. Myeloid type of alpha-3-fucosyltransferase, which transfers fucose on to H type 2, serum type of alpha-3-fucosyltransferase, which transfers fucose on to H type 2 and sialyl-N-acetyl-lactosamine and Lewis or alpha-3/4-fucosyltransferase, which transfers fucose on to H type 1 and H type 2 and the corresponding sialylated structures. The presence of different ABH and Lewis antigens in different tissues and the different epistatic interactions needed to account for their synthesis are analysed in terms of new epistatic interactions with either the known fucosyltransferases or with new fucosyltransferases.

Acceptor specificity and tissue distribution of three human alpha-3-fucosyltransferases

Based on the capacity to transfer alpha-L-fucose onto type-1 and type-2 synthetic blood group H and sialylated acceptors, a comparison of the alpha-3-fucosyltransferase activities of different human tissues is shown. Three distinct acceptor specificity patterns are described: (I) myeloid alpha-3-fucosyltransferase pattern, in which leukocytes and brain enzymes transfer fucose actively onto H type-2 acceptor and poorly onto sialylated N-acetyllactosamine: (II) plasma alpha-3-fucosyltransferase (EC 2.4.1.152), in which plasma and hepatocyte enzymes transfer, in addition, onto the sialylated N-acetyllactosamine; (III) Lewis alpha-3 4-fucosyltransferase (EC 2.4.1.65), in which gall-bladder kidney and milk enzymes transfer, in addition, onto type-1 acceptors. The small amount (less than 10%) of alpha-3-fucosyltransferase activity found in the plasma of an alpha-3-fucosyltransferase-deficient individual had a myeloid-type acceptor pattern, suggesting that this small proportion of the plasma enzyme is derived from leukocytes. In addition to the three acceptor specificity patterns, these enzyme activities can be differentiated by their optimum pH: 8.0-8.7 for the enzymes from myeloid cells and brain. 7.2-8.0 for liver enzymes and 6.0-7.2 for gallbladder enzymes. Milk samples had two alpha-3-fucosyltransferase activities, the Lewis or alpha-3/4-fucosyltransferase under control of the Lewis gene and an alpha-3-fucosyltransferase with plasma acceptor pattern which was independent of the control of the Lewis gene. The apparent affinity for GDP-fucose of the myeloid-like enzyme was weaker than those of the plasma and Lewis-like enzymes. The apparent affinities for H type 2 and sialylated N-acetyllactosamine were stronger for exocrine secretions as compared to the plasma and myeloid enzymes. The plasma type of alpha-3-fucosyltransferase activity was more sensitive to N-ethylmaleimide and heat inactivation than the samples with myeloid-like alpha-3-fucosyltransferase activity.

Overrepresentation of blood group non-secretors in adults with renal scarring

Host factors are important in the pathogenesis of pyelonephritic renal scarring. The present study used blood group secretor state as a population marker to determine if patients developing renal scarring are a selected subgroup of individuals with urinary tract infections (UTI). Non-secretors represented 15/43 (35%) of the patients with renal scarring but only 7/41 (17%) of the patients without renal scarring (p = 0.059 and NS respectively vs. healthy controls 22%). The frequency of non-secretors among P1 phenotype patients with renal scarring was 38% (p = 0.05 vs. healthy controls). Among the patients born after the introduction of regular use of antibiotic treatment for UTI the frequency of non-secretors was 55% in the scarred group compared to 13% in the unscarred group (p = 0.011). Thus, in this younger group of patients with renal scarring 6/10 (60%) of the non-secretors developed renal scars compared to 5/32 (16%) of the secretors (p less than 0.05). Our data confirm that blood group non-secretors are overrepresented in patients with non obstructive renal scarring suggesting that blood group non-secretor state might be a host marker to consider for the subgroup of individuals with recurrent UTI at risk to develop renal scars. Renal function was not influenced by blood group secretor state. The mean glomerular filtration rate within the scarred group was similar for secretors and non-secretors (80 ml/min X 1.73 m2 and 79 ml/min X 1.73 m2, respectively). Whether blood group secretor state also is involved in the scarring process remains to be investigated.

Purification of the blood group H gene associated alpha-2-L-fucosyltransferase from human plasma

The alpha-2-L-fucosyltransferase in human plasma has been freed from alpha-3-L-fucosyltransferase activity and purified approximately 200,000-fold by a series of steps involving ammonium sulphate precipitation, hydrophobic chromatography on Phenyl Sepharose 4B and affinity chromatography first on GDP-adipate-Sepharose and then on GDP-hexanolamine-Sepharose. The purified alpha-2-L-fucosyltransferase had a M(r) on gel filtration HPLC of 158,000 and showed optimal activity in the pH range 6.5-7.0. The enzyme transferred fucose equally well to Type 1 (Gal beta 1-3GlcNAc) and Type 2 (Gal beta 1-4GlcNAc) substrates but Type 3 (Gal beta 1-3GalNAc) structures were less efficient acceptors. Competition experiments indicated that a single enzyme species in the purified preparation was responsible for reactivity with the Type 1 and Type 2 structures. Thus the differences in conformation between the Type 1 and Type 2 disaccharides do not appear to influence the capacities of their terminal non-reducing beta-D-galactosyl residues to function as acceptor substrates for the alpha-2-L-fucosyltransferase expressed by the blood group H gene in haemopoietic tissue.

Secretor state and renal scarring in girls with recurrent pyelonephritis

The non-secretor phenotype was significantly associated with the occurrence of renal scarring among patients with recurrent pyelonephritis. Girls (n = 77) with recurrent pyelonephritis were followed from the first known episode of infection for up to twelve years with repeated radiological investigations. They were divided into two categories: those with renal scars (n = 35) and those who did not develop scars (n = 42). There was a significant over-representation of non-secretors among the patients with scarring, (14/35, 40%) compared to the healthy controls (21.8%, P less than 0.05). The frequency of non-secretors among the girls who did not develop scars in spite of repeated episodes of acute pyelonephritis was not significantly different from the healthy controls (9/42, 21% n.s.). This study provides a basis for analysis of the influence of secretor state on host-parasite interaction in the urinary tract.

A hypothesis on the dual significance of ABH, Lewis and related antigens

ABH and related antigens appeared a long time ago in the evolution of vertebrates on tissues in contact with the external environment, which suggests that the polymorphism given by these antigens might play a role in the relationships of the species with pathogens. However, they are also oncodevelopmental markers and some recent experimental data suggest that they might play a role in cell-cell recognition at some stages of development. This type of function is difficult to reconcile with the polymorphic nature of these markers unless one considers that the glycosyltransferases necessary for the synthesis of the active structures are encoded by various members of multigene families. Some non-polymorphic members of the families would have their expression limited in time and space during development, leading to the same antigenic patterns in every individual, and these could reappear in some tumours, while the expression of other polymorphic members (A/B/O, H/h, Se/se, Le/le), leading to a variety of antigenic phenotypes, would be expressed at later stages and remain so during the whole life of the individual. The corresponding antigens could disappear from some cancer cells. It is argued that the ABH and related antigens would have primarily been involved in cell-cell recognition phenomena. The polymorphism would have evolved later from gene duplication under environmental pressure, the expression on erythrocytes which occurred very late in evolutionary time probably being of very little biological significance.

Histochemical demonstration of O-glycosidically linked, type 3 based ABH antigens in human pancreas using lectin staining and glycosidase digestion procedures

Histochemical analyses of the chemical structures of sugar sequences with or without blood group specificity were carried out by combined stepwise digestion of tissue sections with exo- and endoglycosidases and subsequent lectin stainings in formalin-fixed, paraffin-embedded human pancreas. In acinar cells from blood group A or AB secretor individuals, sequential digestion with alpha-N-acetylgalactosaminidase and alpha-L-fucosidase imparted reactivity with peanut agglutinin (PNA) in cells reactive with Dolichos biflorus agglutinin as well as those with Ulex europaeus agglutinin I(UEA-I). Simple fucosidase digestion imparted the PNA reactivity only in UEA-I reactive cells. Sequential digestion with alpha-galactosidase and fucosidase likewise liberated the PNA binding sites in Griffonia simplicifolia agglutinin I-B4 reactive cells from blood group B and AB secretors. Sialidase digestion liberated the PNA binding sites not only in acinar cells but also intercalated duct cells, islet cells of Langerhans and endothelial cells. The PNA reactivity obtained by these enzyme digestions was eliminted by endo-alpha-N-acetylgalactosaminidase (endo-GalNAcdase) digestion. Preexisting PNA affinity in acinar cells from non-secretors was also susceptible to endo-GalNAcdase treatment. Following the endo-GalNAcdase digestion, fucosidase or sialidase digestion recovered the PNA reactivity in acinar cells from nonsecretors. These results show that ABH determinants carried on O-glycosidically linked type 3 chain (D-galactose-(beta 1-3)-N-acetyl-D-galactosamine alpha 1-serine or threonine) are secreted in pancreatic acinar cells and suggest that product coded by the secretor gene is required for the complete conversion of type 3 precursor chains into H determinants.

Expression of ABH and X (Lex) antigens in various cells

Using a panel of reagents specific to the various subtypes of ABH antigens, it could be demonstrated that platelets carry ABH type 2 monofucosylated determinants on intrinsic glycoproteins. The presence of these antigens is controlled by the H gene and correlates with the presence of alpha-2-L-fucosyltransferase and the absence of alpha-3-L-fucosyltransferase. In contrast, intrinsic ABH antigens were not found on mononuclear cells, correlating with the absence of alpha-2-L-fucosyltransferase on these cells. However, after transformation with the Epstein-Barr virus and stimulation with 12-O-tetradecanoylphorbol-13-O-acetate (TPA), B lymphocytes were found to express the H antigen under control of the H gene and not the Se gene. The lymphoblastoid cell lines also expressed the X and sialylated X antigens which are normally markers of the myeloid lineage. These antigens are also normally found in epithelial cells of the digestive tract, kidney proximal convoluted tubules and hepatocytes. The alpha-3-L-fucosyltransferase responsible for the synthesis of this antigen is present in the serum but we report the existence of two individuals, a mother and her daughter, who lack more than 90% of this serum enzyme. The young girl suffers from a congenital kidney anomaly: oligomeganephronic hypoplasia. Her kidney tubules are devoid of X antigen. However, she and her mother have the X antigen on their granulocytes and its sialylated form on their monocytes. It therefore appears that there are distinct genetic controls for the expression of antigen X in different body compartments. This would be quite similar to the H and Se gene controls in tissues of distinct embryological origins.

Regulation of expression of carbohydrate blood group antigens

The carbohydrate antigens associated with the human ABO and Lewis blood group systems are excellent models for the study of the genetic regulation of glycoconjugate biosynthesis because their expression on erythrocytes and in saliva has been thoroughly investigated in terms of classical genetics and the chemical structures and pathways for the formation of the antigens are now well understood. The primary protein products of the blood group genes are believed to be the glycosyltransferase enzymes that complete the biosynthesis of the determinants. The important controlling factors still to be elucidated are the genetic and environmental influences leading to the tissue specific expression of these antigens. The 3 types of regulation mechanisms discussed in this review are those arising: 1) from the specificity requirements of the glycosyltransferases encoded by the blood group genes; 2) from the competition or co-operation of glycosyltransferases encoded by genes at the same or independent loci; and 3) from the existence and tissue distribution of glycosyltransferases with related, but not identical, substrate specificities.

Biosynthetic pathways for the Leb and Y glycolipids in the gastric carcinoma cell line KATO III as analyzed by a novel assay

The biosynthetic pathways for the difucosylated type 1 and 2 glycolipids, Leb and Y, respectively, were investigated in the gastric carcinoma cell line KATO III, using a novel chromatogram binding assay. The type of fucosylation obtained was deduced from the binding pattern of monoclonal antibodies specific for the biosynthesized glycolipid products using microsomal fractions as the source of enzyme, pure glycolipids and non-radioactive GDP-fucose as acceptor and donor substrates, respectively. The Leb glycolipid (Fuc alpha 1----2Gal beta 1----3GlcNAc(4----1 alpha Fuc) beta 1----3LacCer) was synthesized mainly via the blood group H, type 1, precursor (Fuc alpha 1----2Gal beta 1----3GlcNAc beta 1----3LacCer). However, the Lea glycolipid (Gal beta 1----3GlcNAc(4----1 alpha Fuc)beta 1----3LacCer) also served as a precursor for the alpha 1----2 fucosyltransferase, thus allowing conversion of Lea to Leb. This biosynthetic route represents either an "aberrant" specificity of the Fuc alpha 1----2 transferase associated with these gastric carcinoma cells and/or a new member of the alpha 1----2 fucosyltransferase family. The Y glycolipid (Fuc alpha 1----2Gal beta 1----4GlcNAc(3----1 alpha Fuc)beta 1----3LacCer) was synthesized exclusively via the classical pathway using the blood group H type 2 glycolipid (Fuc alpha 1----2Gal beta 1----4GlcNAc beta 1----3LacCer) as precursor. The X glycolipid (Gal beta 1----4GlcNAc(3----1 alpha Fuc)beta 1----3LacCer) did not serve as an acceptor substrate for the alpha 1----2 fucosyltransferase(s) present. The use of non-radioactive sugar-nucleotides as donor substrate, defined glycolipid precursors as acceptor substrates and of specific monoclonal anti-glycolipid antibodies for detection provides a rapid and highly specific assay for analyzing biosynthetic pathways of glycosyltransferases.

Tumor-associated blood group antigen expressions and immunoglobulins associated with tumors

As outlined in Figures 1 and 2, the biosynthetic pathways for the expression of the A, B and H, and the Lewis determinant carbohydrate sequence structures, as well as sialylated structures, involves both type 1 and type 2 precursor chains (which may be present as glycolipids and N- or O-linked glycoproteins), and many glycosyltransferases. For tumor cells, there appears to be increased expressions of fucosyl- and sialyltransferases yielding such structures as the Le(x), sialyl-Le(a), and many other similar determinants, which are not found on the normal cell progenitor of the tumor. The types of structures expressed on tumor cells is dependent on the particular fucosyl-, sialyl- and other glycosyltransferase genes activated in the transformation and tumor progression events, the availability of the substrates for the glycosyltransferases (both the precursor sequences and the nucleotide-sugar substrates) which is partly dependent on metabolites available to the tumor mass, and on the genotype of the individual regarding particular glycosyltransferases. Both the loss of A, B and/or H blood group antigen expressions of tumor cells and the relative expressions of the Lewis and sialylated-oligosaccharide determinants may be a consequence of the competing biosynthetic pathways and the glycosyltransferases for common substrate sequences, as well as due to the loss of particular glycosyltransferases concomitant with transformation. All of these factors probably account for the variable expressions of the complex of carbohydrate sequence determinants when comparing tumor sections of different individuals as well as the heterogeneity of expression of particular determinants within a single tumor tissue section. As described above, the A, B and/or H determinants, and the precursor sequences, are also expressed to differing extents on epithelial cells depending on the tissue type and cellular location in the tissue. Thus, the differentiation state of the particular epithelial cell also determines the quantity and types of carbohydrate sequences expressed. However, because of the complex nature of the competing biosynthetic pathways for the carbohydrate sequences of glycolipids and glycoproteins, and the relative activations of fucosyl- and sialyltransferases of tumor cells, it would seem that simple deductions as to the state of differentiation of particular tumors with A, B, H and precursor sequence expressions is not warranted.(ABSTRACT TRUNCATED AT 400 WORDS)

Genetics of ABO, H, Lewis, X and related antigens

The present knowledge on chemical, enzymatic, serologic and genetic aspects of ABH antigens is reviewed in an effort to produce a simple and coherent genetic model for the biosynthesis of these antigens and chemically related structures. The genetic control of type 1 (Le(a), Le(b), Le(c) and Le(d)), type 2 (X, Y, I, and H), type 3 and type 4 ABH and related antigens in different animal and human tissues is analyzed, taking into account the properties of the glycosyltransferases which are involved in their synthesis and considering possible competition for common acceptor and donor substrates. The phylogeny of ABH determinants shows that they appeared as tissular antigens much earlier than as red cell antigens. The ontogeny of ABH antigens suggests that they behave as differentiation antigens, and an effort is made to correlate their tissular distribution in the adult with the embryological origin of each tissue.