Stage-specific embryonic antigens (SSEA-3 and -4) are epitopes of a unique globo-series ganglioside isolated from human teratocarcinoma cells.

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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.