ABSTRACT
Irradiated chicken are injected with haemopoietic tissues from adult or 11-day-old embryos. Development of stem cells gives rise to well-defined erythrocytic colonies on the surface of the tibial marrow. Erythropoietic production appears to be similar from adult marrow and embryonic blood stem cells; production from injected vitelline stem cells seems to be between 3 and 4 times higher than that of adult marrow stem cells. Results are discussed on the basis of two hypotheses:
–existence of an extramedullary erythropoietic site in the host after vitelline cells grafting;
–development of vitelline stem cells in the host marrow with kinetic patterns different from those of grafted adult marrow or embryonic blood stem cells.
Anyway, the 11-day-old embryo appears to contain at least two types of blood stem cells with distinctive properties. Developmental origin, relationship and future of these different stem cells remain to be analysed.
