Expression of Lewis histo-blood group glycolipids in the plasma of individuals of Le(a+b+) and partial secretor phenotypes

Blood group antigen expression is involved in C. albicans interaction with buccal epithelial cells

Human blood group polymorphisms are known to be determined by the expression of A, B or H antigens and the Lewis antigens. Protection against microbial infections has been associated with inheritance of polymorphisms in genes encoding and regulating the expression of ABH and Lewis antigens in bodily secretions and epithelial tissue surfaces, subsequently resulting in the presentation of different glycosylated terminal antigens on the cell surface. We investigated the role of blood group antigens in diversifying the glycosylation of buccal epithelial cells (BEC) that line the oral cavity. Specifically, we characterized and statistically evaluated the expression of histo-blood group (A, B, O) antigens on N-and O-linked glycans from BEC membrane proteins of various individuals that represented different blood group type and secretor status using a porous graphitic carbon liquid chromatography electrospray ionization mass spectrometry (PGC-LC-ESI-MS) based glycomics approach. From these BEC membrane proteins a total of 77 N-glycan and 96 O-glycan structures were structurally characterized from 19 individuals and relatively quantitated. The N-glycans from the secretor individuals did not express any A/B blood group determinants, but contained several terminal H-antigens. Apart from the non-secretors, the N-glycan profiles of BEC from all blood groups displayed similar glycan types, while varying in their relative intensities between individuals. However, multivariate analysis of the O-glycans from individuals displayed segregation patterns clearly associated with their blood group type and secretor status. In adhesion assays the oral pathogen Candida albicans showed a significantly higher interaction to blood group O type BECs relative to other blood groups.

Detection of four human milk groups with respect to Lewis-blood-group-dependent oligosaccharides by serologic and chromatographic analysis

Oligosaccharides from human milk samples obtained from individual donors were analyzed using high-pH anion-exchange chromatography. Three patterns of neutral oligosaccharides were detected corresponding to milk groups already described. These oligosaccharide groups correspond to the Lewis blood types Le(a-b+), Le(a+b-), and Le(a-b-). A new carbohydrate pattern was detected in a milk sample from a Le(a-b-) person in which only nonfucosylated oligosaccharides and compounds bearing alpha1,3-linked fucosyl residues were found. This finding led to the hypothesis that there exist 4 different oligosaccharide milk groups that fit well to the genetic basis of the Lewis blood group system.

Detection of four human milk groups with respect to Lewis blood group dependent oligosaccharides

Neutral oligosaccharides in human milk samples from approximately 50 women were analysed applying a recently developed high-pH anion-exchange chromatographic method. Three different oligosaccharide patterns could be detected in accordance with milk groups that had been already described. These oligosaccharide groups correspond to the Lewis blood types Le(a-b+), Le(a+b-) and Le(a-b-). In addition to these oligosaccharide patterns, a new carbohydrate pattern was detected in a milk sample from a Le(a-b-) individual. Here, only nonfucosylated oligosaccharides and compounds bearing alpha1,3 linked fucosyl residues were found, whereas structures with alpha1,2 and alpha1,4 fucosyl linkages were missing. This finding led to the hypothesis that there are four different oligosaccharide milk groups that fit well to the genetic basis of the Lewis blood group system.

Advances in molecular genetics of alpha-2- and alpha-3/4-fucosyltransferases

Fucosyltransferases are involved in the last steps of the biosynthesis of ABH and Lewis oligosaccharide antigens. Seven human genes (FUT1 to FUT7) and one pseudogene (Sec 1) have been cloned and localized on different chromosomes (9q34.3; 11q21; 19p13.3 and 19q13.3). Their locations and their high degree of primary sequence identity, suggest that they have appeared by successive duplications followed by translocation and divergent evolution. Their expression is tissue specific and they present a switch during human embryo-foetal development similar to that of hemoglobins. Polymorphic genes FUT1-FUT2 and FUT3-FUT5-FUT6 are organized in two clusters and each gene is partially or totally inactivated by different types of point mutations (nonsense, missense and frame shift), complete gene deletion or a fusion gene. The products of the monomorphic genes FUT4 and FUT7 seem implicated in cell-cell interactions during embryo-foetal development and in the leukocyte adhesion phenomena to endothelial cells in the adult. A phylogenetic tree of the 28 available nucleotide coding sequences of fucosyltransferases has allowed us to situate the duplication events with respect to the separation of species from the main evolutionary path (nematods, birds, mammals, primates and humans). Recently, using a computer approach a general structure of fucosyltransferases has been proposed, inspired from the crystalline structure of the beta-glucosyltransferase of bacteriophage T4. This folding contains two domains with an alternate succession alpha and beta chains. In this model the GDP-fucose binding site would be located between the two domains.

Molecular basis for erythrocyte Le(a+ b+) and salivary ABH partial-secretor phenotypes: expression of a FUT2 secretor allele with an A-->T mutation at nucleotide 385 correlates with reduced alpha(1,2) fucosyltransferase activity

The SewA385T mutation of the FUT2 gene was found to correlate with both the erthrocyte Le(a + b+) and/or salivary ABH partial-secretor phenotypes of Polynesians. Constructs with FUT1 and FUT2 wild type genes, and the FUT2 SewA385T, seG428A and seC571T mutated alleles, were cloned into pcDNAI, and expressed in COS-7 cells. COS-7 cells transfected with the SewA385T allele had weak, but detectable, alpha(1,2)fucosyltransferase activity, with an acceptor substrate pattern similar to the wild type FUT2 gene. Comparative kinetic studies from cell extracts with mutated SewA385T and wild type FUT2 alleles gave similar Km values, but less enzyme activity was present in cells transfected with SewA385T (Vmax 230 pmol h-1 mg-1), as compared to those transfected with FUT2 (Vmax 1030 pmol h-1 mg-1), suggesting that the mutated enzyme is more unstable. These results confirm that the molecular basis for the erythrocyte Le(a + b+), and the associated ABH salivary partial-secretor phenotype, is an amino acid change of Ile129-->Phe in the secretor alpha(1,2)fucosyltransferase.

Comparison of the Lewis phenotypes among the different population groups of Taiwan

In Caucasians, three red cell Lewis phenotypes are observed, namely Le (a+b-), Le (a-b+) and Le (a-b-). For Chinese living in Taiwan the Le (a+b-) phenotype is replaced by the Le (a+b+) phenotype so that the three red cell Lewis phenotypes observed in Chinese are Le (a+b+), Le (a-b+) and Le (a-b-). In addition, Chinese individuals with Le (a-b-) red cells can be subdivided into two groups, namely those who secrete both ABH and Lewis substances in saliva and those who secrete only ABH substances in saliva. However, four red cell Lewis phenotypes Le (a+b-), Le (a+b+), Le (a-b+) and Le (a-b-) are observed among some of the indigenous groups living in Taiwan. Red cell Le (a+b-) individuals among these indigenous groups can also be subdivided into at least two groups, namely those with Le(a) and Le(b) in saliva (plus varying amounts of ABH substances) and those with just Le(a) in saliva. The former are most likely a weak form of the red cell Le (a+b+) phenotype while the latter appear to be similar to the Caucasian red cell Le (a+b-) phenotype. There was also one red cell Le (a+b-) individual whose saliva had a small amount of A substance as well as Lea substance and therefore appeared to be intermediate between the above two forms of the Le (a+b-) phenotype.

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.

Molecular cloning and expression of a third type of rabbit GDP-L-fucose:beta-D-galactoside 2-alpha-L-fucosyltransferase

Recent molecular investigation revealed that two closely related structural genes encode distinct GDP-L-fucose:beta-D-galactoside 2-alpha-L-fucosyltransferases (alpha1,2-fucosyltransferases). Some human cancer cells or tissues may express an aberrant alpha1, 2-fucosyltransferase other than H- and Secretor-type alpha1, 2-fucosyltransferase. However, definite evidence of the existence of a third type of alpha1,2-fucosyltransferase has not been demonstrated. Here we report the molecular cloning of a third type of rabbit alpha1,2-fucosyltransferase (RFT-III) from a rabbit genomic DNA library. The DNA sequence included an open reading frame coding for 347 amino acids, and the deduced amino acid sequence of RFT-III showed 59 and 80% identity with those of the previously reported two types of rabbit alpha1,2-fucosyltransferase, RFT-I and RFT-II, respectively. COS-7 cells transfected with the RFT-III gene exhibited alpha1,2-fucosyltransferase activity toward phenyl-beta-Gal as a substrate. Neuro2a (a murine neuroblastoma cell line) cells transfected with the RFT-III gene expressed fucosyl GM1 (type 3 H) but not Ulex europaeus agglutinin-1 lectin reactive antigens (type 2 H). Kinetic studies revealed that RFT-III exhibits higher affinity to types 1 (Galbeta1, 3GlcNAc) and 3 (Galbeta1, 3GalNAc) than to type 2 (Galbeta1, 4GlcNAc) oligosaccharides, which suggests that RFT-III as well as RFT-II is a Secretor-type alpha1, 2-fucosyltransferase. RFT-III was expressed in the adult gastrointestinal tract. The RFT-I, -II, and -III genes were assigned within 90 kilobases on pulsed field gel electrophoresis analysis. These results constitute direct evidence that, at least in one mammalian species, three active alpha1,2-fucosyltransferases exist.

A second nonsecretor allele of the blood group alpha(1,2)fucosyl-transferase gene (FUT2)

While screening Le(a+b+)Polynesian DNA samples for a candidate Se(w) allele, a point mutation (C571-->T) resulting in a new stop codon (Arg191-->stop) in the alpha(1,2)fucosyltransferase gene (FUT2) was identified. This point mutation resulted in the gaining of a new restriction enzyme cleavage site (DdeI), which allowed restriction enzyme cleavage screening of 40 selected Polynesians and 42 random Caucasians. The nonsecretor phenotype in two of the three nonsecretor Polynesians analyzed was due to homozygosity for the 'new' mutation, whereas the third Polynesian nonsecretor (with Caucasian ancestors) was due to homozygosity of the 'old' (Trp143-->stop) mutation. The nonsecretor phenotype in all Caucasians analyzed was a consequence of homozygosity for the 'old' mutation. Both the new and the old nonsecretor mutations were identified in the heterozygous state in some secretor-positive Polynesians, while only the old mutation was found in the heterozygous state in Caucasians of the same phenotype.

Correlation of a missense mutation in the human Secretor alpha 1,2-fucosyltransferase gene with the Lewis(a+b+) phenotype: a potential molecular basis for the weak Secretor allele (Sew)

A missense mutation (A385 to T), predicting an Ile129 to Phe substitution, in the human Secretor alpha 1,2-fucosyltransferase gene was present in double dose in Lewis(a+b+) individuals, but not in Lewis(a-b+) individuals. Co-segregation of the Lewis(a+b+) phenotype with homozygosity for the mutation was also verified. These results yield a potential molecular basis for the weak Secretor allele (Sew) accounting for the Lewis(a+b+) phenotype.

Immunochemical and immunohistological expression of Lewis histo-blood group antigens in small intestine including individuals of the Le(a+b+) and Le(a-b-) nonsecretor phenotypes

Histological samples and total non-acid glycosphingolipids were prepared from small intestine of human cadavers with the Le(a+b+) and Le(a-b-) nonsecretor phenotypes and contrasted with the more common Lewis phenotypes. Glycolipid fractions were analysed by thin-layer chromatography and tested for Lewis activity with monoclonal antibodies reactive to Lewis epitopes. Paraffin-embedded small intestine sections were also fluorescently immunostained with anti-Lewis antibodies. Unlike the common Lewis positive phenotypes, we were immunochemically able to demonstrate the copresence of large amounts of Lea and Leb glycolipids in the Le(a+b+) sample. In addition we demonstrated increased formation of extended Lewis structures in this phenotype. By immunohistochemistry Lea, Leb and type 1 precursor chain epitopes could be demonstrated in the brush border. These results show that the expression of the Le(a+b+) phenotype at the erythrocyte phenotyping level parallels the small intestinal expression of this phenotype, and the patterns of Lewis antigen expressions are unique to this phenotype. By immunohistochemistry and immunochemistry we also demonstrated the presence of trace amounts of Lewis active glycoconjugates in the small intestine of the Le(a-b-) nonsecretor and Le(a+b-) samples. In the Le(a-b-) nonsecretor Lea and Leb activity was absent and type 1 precursor was present in brush border, while Leb activity was immunohistologically demonstrated in the Golgi apparatus of the deep glands. Trace amounts of both Lea and Leb glycolipids were identified in this sample. In parallel trace Leb activity could also be detected in the glycolipids of the Le(a+b-) sample and could be immunohistologically demonstrated to be fully expressed in occasional cells in the deep glands of the small intestine, a pattern quite dissimilar to that of the Le(a-b-) nonsecretor.(ABSTRACT TRUNCATED AT 250 WORDS)