I-active antigen of human erythrocyte membrane

Partial characterization of the human erythrocyte receptor for rabbit haemorrhagic disease virus

An important, well known property of the rabbit haemorrhagic disease virus is its ability to agglutinate human red blood cells. Accordingly, red cells from human adult donors were agglutinated despite their blood group ABO status, and treatments with proteases or glycosidases did not prevent agglutination. However, we discovered that the cells from human umbilical cords or foetuses were not agglutinated. In order to identify the viral receptor on human erythrocytes, glycolipids and glycoproteins from adult red cells were separated and tested for their potency in inhibiting agglutination. The bulk of the biological activity was associated with the highly glycosylated glycolipids (polyglycosylceramides), whereas a lower but significant activity was also associated with neutral glycolipids. No activity was found in the lipid-free sialoglycoprotein fractions. All these data strongly suggest that the RHDV receptor on human red cells corresponds to a development antigen which is not expressed on foetal cells and is mainly carried by glycolipids. Faint activity was also found in membranes from sheep red cells, suggesting that a similar glycolipid component is carried by these animal cells.

[Characterization of murine monoclonal antibodies against fetal erythrocytes]

Balb/c mice were immunized against papain-treated fetal erythrocytes and splenocytes were fused with Sp2/0-Ag-14 myeloma cells. Several hybrids secreting antibodies directed against antigenic determinants predominantly exposed on fetal and cord cells were selected and cloned twice. Antibodies NaM61-1A2 and NaM61-768 (IgM class) were shown to be specific for an endo-beta-galactosidase-sensitive oligosaccharide chain. The antigen, strongly expressed on fetal and cord cells, was identified as the i blood group antigen. The antibodies represent powerful blood group reagents to be use in conventional agglutination techniques as well as in the gel typing system and in indirect flow cytometry. The antibody NaM46-4A8 (IgG class) is specific for an antigenic structure expressed on fetal cells and accessible only after papain, ficin, bromelin and endo-beta galactosidase treatment. The antigen was not identified.

Structure and blood-group I activity of poly(glycosyl)-ceramides

Nitrous acid deamination of N-deacetylated blood-group O poly(glycosyl)ceramides resulted in a complete degradation of the glycolipids to give O-beta-D-galactopyranosyl-(1 leads to 4)-2,5-anhydro-D-mannose, O-alpha-L-fucopyranosyl-(1 leads to 2)-O-beta-D-galactopyranosyl-(1 leads to 4)-2,5-anhydro-D-mannose, lactosylceramide, and small proportions of free 2,5-anhydro-D-mannose. A series of straight-chain glycolipids containing up to six glycosyl residues and comprising alternating 3-O-substituted D-galactosyl and 4-O-substituted 2-acetamido-2-deoxy-D-glucosyl residues was isolated from partial acid hydrolyzates of poly(glycosyl)ceramides. Branching points of 3,6-di-O-substituted and 6-O-substituted D-galactosyl residues were observed only in fractions containing more than six glycosyl residues. Sequential periodate oxidation of poly(glycosyl)ceramides gradually eliminated the branching points. This elimination was not complete, even after four cycles of degradation. The ability of poly(glycosyl)ceramides to precipitate with anti-I serums disappeared after two cycles of degradation. These results suggest a general structure for poly(glycosyl)ceramides. I blood-group activity of the glycolipids would depend on the periodical arrangement of branched side-chains.

ABO(H) blood group antigens of the human erythrocyte membrane: contribution of glycoprotein and glycolipid

Formaldehyde-fixed human erythrocytes were extracted with sodium dodecyl sulfate and with three other solvent systems, at least two of which are known to remove glycolipids quantitatively. The extracted cells possessed the ability to absorb the ABO blood group-specific antibody at about one-third the level of unextracted cells. Treatment of fresh cells with pronase also reduced the ability of the cells to absorb the antibody, further supporting the presence of ABO blood group active glycoprotein in the membrane. Trypsinization of red cells, while removing PAS-1 and partly PAS-2, did not lead to any decrease in the activity. Papainization also did not diminish the activity, although PAS-1, PAS-2, and PAS-3 were removed from the cells. Thus, both glycolipid and glycoprotein contribute to ABO antigens of erythrocytes. Also, none of the three major glycoproteins of the membrane bears this activity.

The I, i, and HI blood group antigens in extracts of human erythrocytes

Extracts of stromata of human adult and newborn (cord) erythrocytes were prepared with n-butanol. The aqueous phase and butanol phase extracts were examined for the presence of blood group I, i, HI and H substances in inhibition of agglutination experiments. The recovery of HI activity in both the aqueous and butanol phase extracts of adult red cells but only in the aqueous phase of cord cells is reported heare for the first time. The i specificity was present in the aqueous phase but not in the butanol phase of cord erythrocytes, also not previously reported. Although the recovery of I but not i substance in aqueous phase extracts of adult cells had been shown by other workers, examination of the butanol phase extracts for I and i substances had not been documented. In the present study, Ii substances were not demonstrable in any of the butanol phase extracts of adult and cord erythrocytes.

H, A and A1 reactivity in two Polynesian groups

Polynesian O bloods from Samoans and Tokelau Islanders have the same mean H reactivity as Caucasian, and their A1 bloods the same A1 content. However, Polynesian A1 bloods have significantly greater H reactivity than Caucasian, and the Tokelau Islanders also showed enhanced A and IT. It is suggested that the Polynesian AHI molecular conformation must differ from the Caucasian pattern, providing an arrangement of antigen sites more favourable to some antigen-antibody reactions.

Isolation and characterization of poly(glycosyl)ceramides (megaloglycolipids) with A, H and I blood-group activities

Very complex glycosphingolipids with A, H and I blood-group activities were isolated from human erythrocyte membranes. The membranes were obtained from erythrocytes of blood group A, A2 and O respectively. A general formula for the antigens is: (Fuc)3-4(Gal)n(LlcNAc)n-2(Glc)1(Sphingosine)1(where Fus is fucose, Gal is galactose, GlcNAc is N-acetylglucosamine and Glc is glucose) with values of n ranging from 10-27. A-active preparations contain additionally 2-3 residues of N-acetylgalactosamine. In view of the unusual complexity of these compounds they were designated poly(glycosyl)ceramides (formerly megaloglycolipids). Individual poly(glycosyl)ceramide fractions were isolated from A erythrocytes and were found to differ by about 8 glycosyl residues per molecule forming a series of compounds with 22, 30, 38, 51 and 59 glycosyl residues per mole. Structural studies indicate that the main sequence of poly(glycosyl)ceramides consists of the residues of galactopyranose and 2-deoxy-2-acetamidoglucopyranose substituted at 3 and 4 position respectively. These residues are probably alternating. N-Acdtylglucosamine substituted at 3 position was not found in poly(glycosyl)ceramides. Brances of poly(glycosyl)ceramides originate from 3 and 6 position of galactopyranosyl residues. The number of branches is proportional to the degree of molecular complexity. In poly(glycosyl)ceramides isolated from A and A2 erythrocytes the branches are terminated with the following structures GalNAc alpha 1 leads to 3 [Fuc alpha 1 leads to 2] Gal; Fuc alpha 1 leads to 2 Gal and Gal (presumably Gal beta 1 leads to 4 GlcNAc). In poly(glycosyl)ceramides from A cells the total number of A and H-active structures per average molecule of 30-35 glycosyl residues amounts to 2.1 and 1.2 respectively while the number of terminal galactose structures is 1.8. For poly(glycosyl)ceramides from A2 erythrocytes the corresponding figures are 0.75, 3.5, and 2.1 respectively. Poly(glycosyl)ceramides from O cells comprise about 3.8 H-active structures and 1.8 terminal galactopyranosyl residues. In poly(glycosyl)ceramides with high "n" values the number of terminal galactose structures is increased. These fractions display high blood-group I activity. However, the removal of terminal galactose with beta-galactosidase affects I-activity only slightly.

Separation of ABH, I, Ss antigenic activity from the MN-active sialoglycoprotein of the human erythrocyte membrane

The erythrocyte sialoglycoprotein was purified from cells with complementary ABO(H), MN and Ss phenotypes. Serological examination of the sialoglycoprotein preparations demonstrated that this molecule does not carry the ABO(H), I or Ss antigens. The results also suggest that Ss activity may be associated with a minor erythorcyte glycoprotein. The characteristics of the ABO(H) and I antigens are consistent with earlier suggestions that these antigens are carried on complex glycolipids.

Reactions of erythrocyte glycoproteins and their degradation products with various anti-I sera

Three fractions of erythrocyte glycoproteins obtained from Sepharose 4-B chromatography were tested for I activity with ten serologically differentiated anti-I sera. The most active was fraction I, eluted at the void volume and containing the lowest amount of alkali-labile oligosaccharide chains. The desialization of glycoproteins increased their activity toward anti-I-s and anti-I-D sera, and did not change or decreased the activity toward anti-I-F sera. The most abundant fraction II (major sialoglycoprotein of erythrocyte membranes) showed no or only a very weak I activity, but I-active glycopeptides were isolated from products of digestion of fraction II with trypsin. The major product of digestion, sialoglycopeptide IIT-2 showed I activity only after alkaline elimination of alkali-labile oligosaccharide chains. The results indicate that I receptors are present in hindered form on apparently I-inactive components of erythrocyte membrane.