The Beneficence of Neonatal Hematopoiesis

Abstract

THE fetus and the newborn are highly endowed with the capacity to produce blood,¹ and the site-specific stages and switches through which the accelerated blood production moves during development² are becoming particularly fascinating as the regulatory proteins that influence them are identified.³ The production of red cells begins in the yolk sac only a few weeks after conception. Yolk-sac erythrocytes are very large nucleated cells that uniquely express the products of certain genes, such as embryonic globin. When hematopoiesis is completed in the yolk sac, it moves on to the liver, and that organ fills with nucleated red cells. Relatively . . .