Two
monoclonal antibodies (TRA-1-60 and TRA-1-81) recognizing distinct
cell surface antigens on human
embryonal carcinoma (EC) cells were produced and characterized. These
antibodies reacted strongly with undifferentiated human EC cells in indirect radioimmunoassays (RIA) and immunofluorescence (IF) assays, but only weakly or not at all with cells derived from pluripotent EC cells differentiating in vitro or in xenograft
tumors, nor with other
germ cell tumor cell lines that did not also express the typical features of human EC cells. They did not react with murine
teratocarcinoma cell lines. A survey of other human tumor cell lines and normal human tissues disclosed that molecules recognized by these
antibodies are not confined to human EC cells but that cross-reacting
epitopes appear on several neoplastic and normal tissues, although in a different anatomical pattern for each antibody. Both
antibodies immunoprecipitated a major
polypeptide (apparent molecular weight approximately 240,000) and a minor
polypeptide (apparent molecular weight approximately 415,000) from lysates of 125I surface-labeled human EC cells, in this respect resembling another
monoclonal antibody, 8-7D, previously described by Blaineau et al. (1,2) However, sequential immunoprecipitation revealed that each of the three
antibodies reacted with different molecules of slightly different molecular weights. The
epitopes defined by the present
antibodies differ from those recognized by the other human EC cell-specific
monoclonal antibodies that have been described and provide new markers for studying the differentiation of pluripotent human EC cells.