The fate of heterotopic isografts and allografts of mouse yolk sac epithelium.

As a contribution to the problem of the immunological privilege of the fetus it was decided to investigate the fate of yolk sac grafts in mice. Ten-day post-coitum mouse visceral yolk sac was transplanted to a dermal tunnel in the flank of isogeneic animals. In this site the yolk sac was capable of surviving for at least 15 days past the normal duration of pregnancy. Yolk sac was transplanted to a similar site in allogeneic animals and was found to be destroyed by an immunological reaction within 13 days. Orthotopic skin grafts between the same strains of mice used in the yolk sac transplantation were rejected in first-set fashion within 13 days. A limited series of host animals, previously sensitized by visceral yolk sac, rejected orthotopic skin grafts in second-set fashion. These findings indicate that the cells of the visceral yolk sac in the mouse contain transplantation antigens. Possible reasons why such antigens do not lead to fetal rejection during pregnancy are considered.