[Granulopoiesis and its regulation]

Abstract

The neutrophil granulocytes are derived, in the present state of our knowledge, from a hemocytoblast identical with that of the other blood cells, defined by its power to form in vivo clones of multiple composition, defining their characteristic of totipotential undifferentiated cell. The way in which the clone-forming cell evolves in vivo towards granulopoiesis, depends on a genetic factor, phenomena of derepression and an extrinsic factor, the origin of which is probably cellular. Differentiation of the hemocytoblast leads to a cell, the destiny of which is then fixed, which may then form clones in vitro in semi-solid medium (clone-forming cell in vitro or CFC). This cell is definitely a true entity. A humoral factor of macrophage origin intervenes to ensure granulopoiesis in vivo (clone-stimulating factor CSF3. The phenomena which regulate this granulopoiesis then cause to intervene various biochemical forms of this clone-stimulating factor and an inhibitor, the reality of which is not yet definitely demonstrated in vivo. Laboratory animals and cell culture of human normal and leukemic granular cells now supplies experimental models which permit studies of the granular differentiation of the hemocytoblast completed by kinetic studies in vivo to make rapid progress, especially in our knowledge of the human leukemic process.