Two hybrid cell lines were prepared by the fusion of mouse myeloma cells with the spleen cells of BALB/c mice that had been immunized with the glycolipid ganglio-N-triosylceramide (asialo GM2). The specificity of the monoclonal antibodies produced by these hybridomas, one an IgM and the other an IgG3, has been defined by hemagglutination inhibition, complement fixation, and lysis of glycolipid liposomes by antibody and complement. A major determinant recognized by the IgM antibody is the nonreducing terminal N-acetylgalactosamine including the C6 primary hydroxyl group, but excluding the C2-acetamide group of N-acetylgalactosamine, because oxidation with galactose oxidase produced a structure showing only minimal cross-reaction with the IgM but replacement of the N-acetyl group with an N-n-butyryl group produced a glycolipid that reacts with IgM antibody to the same extent as with the unmodified glycoplipd. A major determinant recognized by the IgG3 antibody is the terminal N-acetylgalactosamine including the C2-acetamido group, but excluding the C6 primary hydroxyl group of N-acetylgalactosamine, because replacement of the N-acetyl group with an N-n-butyryl group produced a glycolipid that did not react with the IgG3 antibody; in striking contrast the IgG3 antibody reacted with the C6-oxidized glycolipid as well as with the native glycolipid. Neither antibody reacted significantly with any other natural glycolipids tested including several that are structurally related to asialo GM2 such as ganglioside GM2, ganglio-N-tetraosylceramide (asialo GM1), or ceramide dihexoside. These results indicated that in addition to the fine structure specificity described above both antibodies recognize the nonreducing terminal GalNAc beta 1 leads to 4Gal structure. The strict antigenic specificity of these monoclonal anti-glycolipid antibodies indicates their great potential as specific probes for cell surface studies.

Blood group I activities of the purified glycosphingolipid lacto-N-iso-octaosyl ceramide (Fromula: see text) and 8 of its analogues have been evaluated with 11 anti-I sera including 5 anti-I sera previously tested. All but one of the antisera were inhibited by the lacto-N-iso-octaosyl structure. Three types of I-specificity could be distinguished although none of the anti-I sera was identical in its inhibition patterns with the nine glycophingolipid analogues. The anti-I sera Ma and Woj represent the first type and require an intact Galbeta1 leads to 4GlcNAcbeta1 leads to 6 chain, the anti-I sera Step, Gra, Ver, and Ful represent the second type which requires Galbeta1 leads to 4GlcNAcbeta1 leads to 3 chain with branching, and the anti-I sera Phi, Da, Sch, and Low belong to the third type which requires both branches to be intact. Anti-I antibodies varry in their ability to react with their antigenic determinants in the presence of external substitutions with alpha-linked galactose or sialic acid.

Blood group ABH determinants in human erythrocytes are carried by four kinds of glycolipid carbohydrate chains, differing in their structural complexity. They are Aa, Ab, Ac, and Ad for A variants, and H1, H2, H3, and H4 for H variants (Table I and Fig 1). Based on the surface labeling of A variants and on the reactivity of erythrocytes to antibodies directed against H3 and against its degradation products, it is concluded that complex variants of A or H determinants (Ac and Ad/or H3 and H4) are absent or significantly low in fetal erythrocytes (80-150 days after gestation) and in new born erythrocytes, whereas these complex structures are fully developed in adult erythrocytes. In contrast, A determinants linked to simpler carbohydrate chains (Aa, Ab variants) are fully developed before birth and do not show significant change after birth. The precursor of blood group carbohydrate chains seems to be abundant in fetal or newborn erythrocytes. This assumption is based on the higher reactivity of fetal or newborn erythrocytes to an antibody, which is directed against the precursor N-acetylglucosaminly beta1 leads to 3 galactosyl beta1 leads to 4 glucosylceramide than in adult erythorocytes. Reactions of glycolipids of gastrointestinal mucosa, with antibodies directed against H3 glycolipid and its degradation products, were compared to that of gastrointestinal tumors. The reaction to bela Glc NAc1 leads to 3 beta Gall leads to 4 Glc leads to ceramide (structure 4), which is the precursor of all blood group glycolipids, was consistently high in many cases of tumor glycolipid than that of normal glycolipid. This as well as other evidence supports a general concept that the process of ontogenesis of a blood group carbohydrate chain occurs as step-by-step elongation and arborization, and that blocking of such a development of a carbohydrate chain occurs in the process of oncogenesis.