Natural cytotoxicity in the mouse embryo. I. Evidence for the presence of natural cytotoxic function in the yolk sac of the 10-day mouse embryo.

Yolk sac cells from 10-day mouse embryos have natural cytotoxic activity directed against YAC-1 tumor targets but not against P815 tumor targets. Other embryonic tissues tested, including TG-16 embryonal carcinoma, fetal thymus, and fetal liver, do not display natural cytotoxic activity comparable to the yolk sac activity. The correlations between yolk sac natural cytotoxic function, and adult NK and promonocyte cytotoxic functions are briefly discussed.