No abstract

Two monoclonal antibodies (MC631 and MC813‐70) raised against 4‐ to 8‐cell stage mouse embryos and a human teratocarcinoma cell line, respectively, detect the stage‐specific embryonic antigens, the previously defined SSEA‐3 and SSEA‐4, described herein. These antibodies were both reactive with a unique globo‐series ganglioside with the structure shown below: (formula; see text) The antibodies were found to recognize sequential regions of this ganglioside, i.e., MC813‐70 recognizes the terminal ‘a’ structure whereas antibody MC631 recognizes the internal ‘b’ structure. Thus, a set of two antibodies defines this unique embryonic antigen. During differentiation of human teratocarcinoma 2102Ep cells, the globo‐series glycolipids defined by these antibodies decrease and the lacto‐series glycolipids, reacting with the SSEA‐1 antibody appear. This antigenic conversion suggests that a shift of glycolipid synthesis from globo‐series to lacto‐series glycolipids occurs during differentiation of human teratocarcinoma and perhaps of pre‐implantation mouse embryos.

L-selectin, a lectin-like receptor, mediates rolling of lymphocytes on high endothelial venules (HEVs) in secondary lymphoid organs by interacting with HEV ligands. These ligands consist of a complex of sialomucins, candidates for which are glycosylation- dependent cell adhesion molecule 1 (GlyCAM-1), CD34, and podocalyxin. The ligands must be sialylated, fucosylated, and sulfated for optimal recognition by L-selectin. Our previous structural characterization of GlyCAM-1 has demonstrated two sulfation modifications, Gal-6-sulfate and GlcNAc-6-sulfate in the context of sialyl Lewis x. We now report the cloning of a Gal-6-sulfotransferase and a GlcNAc-6-sulfotransferase, which can modify GlyCAM-1 and CD34. The Gal-6-sulfotransferase shows a wide tissue distribution. In contrast, the GlcNAc-6-sulfotransferase is highly restricted to HEVs, as revealed by Northern analysis and in situ hybridization. Expression of either enzyme in Chinese hamster ovary cells, along with CD34 and fucosyltransferase VII, results in ligand activity, as detected by binding of an L-selectin/IgM chimera. When coexpressed, the two sulfotransferases synergize to produce strongly enhanced chimera binding.