Observations on some immune properties of preimplantation rat blastocysts.

Rat blastocysts after 3, 24 or 72 hours in culture, were exposed to antiserum against rat embryo and mouse placenta in the presence of complement. The concomitant exposure damaged the trophoblastic cells and the inner cell mass. Differences were not observed in the nature and strength of the damage between blastocysts with or without zona pellucida. When the cultured blastocysts were exposed first to antisera and only later to complement, the damage seemed to be selective. In the 3 and 24 hour cultured blastocysts, only the trophoblastic cells were destroyed but not the inner cell mass. In the 72 hour cultures, the damage was inflicted to all cells including the inner cell mass, exposed after spreading of trophoblastic cells. The anti-rat embryo serum and the anti-mouse placenta serum had similar effects in low dilutions. In high dilution, the anti-rat embryo serum was more potent. Isolated inner cell masses were cultured up to 72 hours but did not attach to the dish nor spread. Nevertheless, the cells survived, proliferated and differentiated into an outer layer of seemingly endodermal cells.