Fetal antigens shared as transplantation rejection antigens on chemically induced mouse and hamster sarcomas.

We have previously reported that two chemically induced sarcomas of BALB/c mice (MCA-1315 and -1321) contained common transplantation antigens which could be detected by immunization of normal BALB/c mice with irradiated tumor cells of each line. This cross-protection could not be detected in animals surgically cured of these tumor lines and challenged with a high dose of tumor cells, but it was detectable in similar animals challenged with low doses of homologous tumor cells. In this report, we demonstrate that these chemically induced tumor lines carry fetal antigens which are recognized by cytotoxic or inhibitory mouse BALB/c maternal lymphocytes sen sitized during pregnancy to mouse fetal antigen. A similar fetal antigen determinant was observed on two chemically induced sarcomas of hamster which were likewise recognized by ham ster maternal lymphocytes derived from 10-day pregnant do nors. The time course of appearance and disappearance of spleen or exÃodate cells from pregnant mice capable of pro tecting BALB/c mice against challenge with these fetal antigenbearing 3-methylcholanthrene-induced tumor target cells was determined. Protective lymphocytes were not detected in primiparous mice two days prior to parturition and appeared after Day 10 in pregnancy. Among animals experiencing multiple pregnancies, low but reproducible levels of protector lympho cytes could be detected by Day 8 to 9, and protective lympho cytes persisted to parturition in these animals. Correlations of these results with previous reports from this laboratory con cerning the expression of fetal antigens in the membranes of embryonic and fetal cells of hamsters and mice are discussed. These data establish that common antigens shared as trans plantation rejection antigens between chemically induced sar comas of mice and hamsters are of fetal or embryonic origin.