In vitro sensitization to embryonic antigens.

Lymphoid cells from virgin, untreated BALB/c mice cultured 5 days on 12- or 13-day syngeneic mouse embryo fibroblasts (MEF) or on cells from a syngeneic 3-methylcholanthrene-induced mouse sarcoma (1315) were cytotoxic for 1315 tumor target cells when tested with a microcytotoxicity assay. They did not kill embryo or skin fibroblast target cells. Lymphoid cells cultured with 11-, 14- or 17-day MEF were not cytotoxic for cells from the 1315 tumor, from embryo or from adult skin. Lymphoid cells from multiparous BALB/c mice cultured on 11-, 12- or 13-day MEF, on line 1315 sarcoma cells or on skin fibroblasts were cytotoxic for tumor target cells. MEF were killed by multipara lymphoid cells that had been cultured on 11-, 12- or 13-day MEF or on the 1315 tumor line. Multipara lymphoid cells cultured on 1315 cells or 12-day MEF were cytotoxic for adult skin fibroblasts, while multipara lymphoid cells cultured on 14- or 15-day MEF were not cytotoxic for any of the target cells. The data thus indicate that lymphoid cells can mediate both primary and secondary immune reaction in vitro to antigens shared by neoplastic and normal embryonic cells, and that the primary reactions appear to be more specific to putatively embryonic tumor antigen(s) than the secondary ones.