title: Repetitive A epitope (type 3 chain A) defined by blood group A1-specific monoclonal antibody TH-1: chemical basis of qualitative A1 and A2 distinction.
abstract: The IgG2a monoclonal antibody TH-1, which reacts specifically with blood group A1 but with neither A2 nor O erythrocytes, has been established. The antibody reacted only with A1 erythrocytes in hemagglutination and antibody absorption assays; it did not react with A2 erythrocytes, even after trypsin or sialidase treatment. This antibody detected, on TLC immunostaining, a series of glycolipids from A1 erythrocytes but virtually none or very weak bands from A2 erythrocytes. It did not react with type 1 or type 2 chain A, or with globo-A. The simplest reactive component was isolated from a previously assigned Ab fraction by HPTLC of acetylated compounds. The structure of the reactive component was characterized by 1H NMR spectroscopy, methylation analysis, and enzymatic degradation, as shown below: (Formula: see text). The structure is essentially a repetitive A epitope attached to type 2 chain and is hereby called type 3 chain A. The determinant can be carried on extended and/or branched structures, but it was not detectable in glycoproteins. The structure was characteristic of A1 erythrocytes and present in only trace amounts in A2 erythrocytes. The precursor H (Fuc alpha 1----2Gal beta 1----3GalNAc alpha 1----3[Fuc alpha 1----2]Gal beta 1----4GlcNAc beta 1----R; type 3 chain H) was present in greater quantity in A2 erythrocytes than in A1 erythrocytes, but it was absent in both O and B erythrocytes. The A1 transferase apparently can transfer alpha-GalNAc to type 3 chain H, while the A2 transferase may not have this ability.
authors.forename: H
authors.initials: H
authors.lastname: Clausen
authors.forename: S B
authors.initials: SB
authors.lastname: Levery
authors.forename: E
authors.initials: E
authors.lastname: Nudelman
authors.forename: S
authors.initials: S
authors.lastname: Tsuchiya
authors.forename: S
authors.initials: S
authors.lastname: Hakomori
mesh_terms: D000017:ABO Blood-Group System / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D002240:Carbohydrate Sequence; D000939:Epitopes / Q000276:immunology; D006017:Glycolipids / Q000276:immunology; D006023:Glycoproteins / Q000276:immunology; D006801:Humans
chemical_list: D000017:ABO Blood-Group System; D000911:Antibodies, Monoclonal; D000939:Epitopes; D006017:Glycolipids; D006023:Glycoproteins