Cell Interactions in the Ontogeny of the Hemopoietic System
In vivo and in vitro functional tests demonstrate the existence in adult animals of progenitor cells which differentiate into various mature blood cells, provided specific factors are available to them. These progenitors themselves are thought to derive from pluripotent or totipotent stem cells. It is still a major guestionmark whether the differentiating factors determine the commitment of progenitors towards one line of differentiation or whether these factors merely have a trophic action on cells committed through stochastic processes. Whichever the mechanism, the differentiating factors are provided to the progenitors within the microenvironments of hemopoietic organs. Thus functioning of the hemopoietic system is characterized by the interaction of two distinct cell lineages, on one hand the stromal cells which constitute the microenvironments, on the other hand the blood cell progenitors.
KeywordsVentral Wall Avian Embryo Differentiate Factor Mature Blood Cell Quail Embryo
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