Regulated expression of an introduced MHC H-2K bm1 gene in murine embryonal carcinoma cells.

The transplantation antigens H-2K, H-2D and H-2L are developmentally regulated, highly polymorphic cell surface proteins encoded by the major histocompatibility gene complex (MHC). First detectable on the early embryo, they are subsequently expressed on most somatic cells of the adult mouse in association with the protein beta2-microglobulin (beta 2 M; ref. 5). Cultured F embryonal carcinoma (EC) cells can be induced to differentiate along alternative pathways to form either parietal or visceral9 extra-embryonic endoderm, each concomitant with a change in morphology and pattern of gene expression. Previous reports have demonstrated an increased level of transplantation antigens in differentiated F9 EC cells, but the cell types expressing them were not defined. Here we show that the level of MHC H-2Kb and beta 2 M transcripts is increased during both pathways of this differentiation. Expression of a foreign MHC H-2Kbm1 gene was found to be regulated in a similar manner when the gene was introduced into EC cells. In contrast, an introduced rabbit beta-globin gene was not regulated but expressed constitutively.