[Regulation of hematopoiesis].

Hematopoiesis is regulated by a tiny population of cells, the stem cells and committed progenitors. These cells are under the influence of hematopoietic growth factors most of which are produced immediately in their environments. Their fates are strongly influenced by those growth factors. The growth factors interact with specific receptors that are present on progenitor surfaces and may in fact induce changes in the levels of those receptors. The receptors form dimers or heterodimers to pass proliferative and differentiation signals into the cell. We do not yet know exactly how that signalling is accomplished, but will probably known much more about it in the next year or so.