Erythropoiesis and lymphopoiesis in the chick yolk-sac-embryo chimeras: contribution of yolk sac and intraembryonic stem cells

Lymphocyte development and ontogenetic changes in erythroid cells have been studied in chick-chick yolk-sac-embryo chimeras differing at the B locus antigens. Erythroid cells derived from the yolk sac or from the intraembryonic mesenchyme were demonstrated by mdi-rect immunofluorescence in the peripheral blood of these allogeneic chimeras. At 7 days of incubation, yolk-sac-derived red cells represent a majority in the peripheral blood. From 9 days of incubation onwards, embryo-derived erythrocytes appear in increasing proportions. making up approximately 90 % of the peripheral blood cells at 17-18 days of development. After hatching. no yolk-sac-derived V ERTEBRATE EMBRYOS of different species show developmental changes in their erythro-poiesis.”2 The early embryo elaborates a primitive re