| Abstract: | Embryonal carcinoma cells from the PSA1 cell line will differentiate in vitro to form structures called embryoid bodies composed of an inner core of embryonal carcinoma cells surrounded by a basement membrane matrix and an outer layer of extra-embryonic endodermal cells. Immunization of rabbits with basement membranes isolated from embryoid bodies resulted in an antiserum, which binds to fixed extra-embryonic endodermal cells of either embryonic or teratocarcinoma origin but does not bind substantially to mouse embryonal carcinoma cells, fibroblasts, myoblasts or erythroleukemic cells. The F9-22 embryonal carcinoma cell line normally differentiates only to a very limited extent in vitro or in vivo. However, incubation of these cells in medium containing retinoic acid results in the appearance of cells resembling extra-embryonic endoderm. The embryoid body basement membrane antibodies were used to measure, by flow microfluorometry, the appearance of reactive cells in F9-22 cultures treated with retinoic acid. The kinetics of appearance of cells reactive with the basement membrane antibodies are similar to the kinetics of appearance of cells secreting plasminogen activator, a known marker of extraembryonic endoderm. |
