Glycosphingolipid carriers of carbohydrate antigens of human myeloid cells recognized by monoclonal antibodies

Abstract

Six monoclonal antibodies with known specificities for the carbohydrate antigens i, X or Y, and seven anti-myeloid antibodies (determinants unknown) selected for their differing reaction patterns with human leucocytes were tested in chromatogram binding assays for reactions with myeloid cell glycolipids derived from normal human granulocytes and chronic myelogenous leukemia cells. Antigenicities were found exclusively on minor glycolipids which were barely or not at all detectable with orcinol-sulphuric acid stain. Among these, a neutral glycosphingolipid bound the anti-i antibody Den and chromatographed as the ceramide octasaccharide, Gal β1 → 4GlcNAc β1 → 3Gal β1 → 4GlcNAc β1 → 3Gal β1 → 4GlcNAc β1 → 3Gal β1 → 4Glc-Cer. Several species of neutral glycosphingolipids with six to more than ten monosaccharides were detected which carry the X antigen and others the Y antigen: Gal β1 → 4(Fuc α1 → 3)GlcNAc and Fuc α1 → 2Gal β1 → 4(Fuc α1 → 3)GlcNAc, respectively. In addition, three new types of carbohydrate specificities were detected among the myeloid cell glycolipids. Two were associated with neutral glycolipids: the first, recognised by anti-myeloid antibodies VIM-1 and VIM-10, was expressed on a distinct set of glycolipids with six or more monosaccharides, and the second, recognized by VIM-8, was expressed on glycolipids with more than ten monosaccharides. The third specificity, recognised by the anti-myeloid antibody VIM-2, was expressed on slow migrating sialoglycolipids with backbone structures of the poly- N-acetyllactosamine type that are susceptible to degradation with endo-β-galactosidase. Thus, we conclude that the i and Y antigens occur among the glycolipids of normal myeloid and chronic myelogenous leukemia cells and that a high proportion of hybridoma antibodies raised against differentiation antigens of myeloid cells are directed at carbohydrate structures.