Presence of common surface antigens(s) on endodermal tumors and embryonal tissues of rats, hamsters and mice.

Antiserum against yolk-sac carcinoma of rat was prepared in rabbits. After appropriate absorption in vitro or in vivo this antiserum was examined on different tumors and normal tissues or rat, hamster and mouse. The methods used were indirect immunofluorescence and indirect immunoperoxidase staining and cytotoxicity tests. The immune serum was found to react with the cell membrane of different rat and hamster yolk-sac carcinomas. It reacted also with the cell surface of rat hepatoma cells. By absorption on hyalin and blocking with amniotic fluid it was shown that the antigen was neither a basement membrane component nor alpha-fetoprotein. The antiserum was cytotoxic to yolk-sac carcinoma and hepatoma cells. The immune reaction was limited to the cell membrane, as observed in immunofluorescence and in immunoperoxidase staining. The specificity of the antiserum was proved by cross-absorptions with various tumor lines and by removing its activity with the soluble fraction of yolk-sac carcinoma cells. Non-endodermal rat and hamster tumor lines did not react with the anti-yolk-sac carcinoma immune serum. Most normal adult tissues, including spermatozoa, were negative, but a positive reaction was observed in ovaries and on glandular cells of the uterus. In embryonal tissues this surface antigen(s) was detected in the endoderm of 8-day-old rat embryos 7-day-old mouse embryos and in yolk-sac endoderm of both species. The data indicate that the antigen(s) is associated with endodermal differentiation.