Migration of prebursal stem cells from the early chicken embryo to the yolk sac.

Allogeneic yolk sac-embryo chimaeras were constructed by association of B15B15 yolk sac and B2B2 embryo on day 2 of incubation. Five days later yolk sac cells from the chimaeras were injected intravenously into 14-day-old irradiated embryos, using recipients of B2B2 and B15B15 genotypes. One week after hatching, cells in the bursa of Fabricius and peripheral blood erythrocytes were studied for Ia-like antigens and B alloantigens, respectively, to determine whether they were derived from the embryo or yolk sac part of the chimaera. The results obtained demonstrate that prebursal and erythropoietic stem cells migrate from the early embryo to the yolk sac during the 2nd to the 7th day of incubation. They also exclude the de novo generation of prebursal stem cells in the yolk sac.