ABSTRACT
In recent years, a large number of extracellular growth factors which regulate hematopoietic cell development have been molecularly cloned, expressed as active proteins, and utilized in the clinic. The intracellular events that are triggered when these growth factors interact with their receptors have also begun to be defined. Nevertheless, most of the molecular machinery that regulates blood cell development remains enigmatic and difficult to access. This situation applies particularly to normal blood cells because of the difficulty of applying modern molecular analytic techniques to the small numbers of cells that are ordinarily available for such investigations.
