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

Lymphocyte development and ontogenetic changes in erythroid cells have been studied in chick-chick yolk sac-embryo chimeras constructed of histoincompatible partners. The results obtained indicate that the early chick yolk sac produces transiently erythroid stem cells whereas definitive erythrocytes are derived from the intraembryonic stem cells. Such a change from the yolk sac-derived cells into embryo-derived cells is not observed in the lymphocytes which are exclusively derived from the embryo-borne stem cells. Experiments with cell transfers from the chimeric yolk sacs demonstrate that erythropoietic and prebursal stem cells migrate from the early embryo to the yolk sac during the second to the seventh day of incubation. The results obtained also exclude the de novo generation of prebursal stem cells in the yolk sac.