Evidence for a membrane carrier molecule common to embryonal and tumour-specific antigenic determinants expressed by a mouse transplantable tumour.

Rabbits were primed with membrane antigens solubilized from BALB/c embryo cells. After boosting with membrane antigens solubilized from a syngeneic transplantable adenocarcinoma, they developed a 'secondary' response against tumour-specific antigenic determinants. The antibodies against these determinants neither reacted with nor were absorbed by the antigens prepared from embryonal cells. However, the antigen displaying the tumour-specific determinants was bound by a reversed immunoadsorbent of insoluble anti-embryo antibodies. Indirect immunofluorescence experiments performed on adenocarcinoma cells in culture showed that, under conditions where redistribution of cell membrane components was induced, the anti-embryo antiserum aggregated the tumour-specific determinants. The purification of embryo and tumour-specific antigens achieved by affinity chromatography on insoluble antibody columns yielded three polypeptides of molecular weight close to 25,000, 20,000, and 10,000 Daltons respectively. It is suggested that the antigenic determinants responsible for tumour and embryo specificities in adenocarcinoma were located on the same molecule, or, more likely, on molecules which are closely associated in the plasma membrane and that do not dissociated in bile salts.