Expression of hematopoietic growth factor receptors on early hematopoietic precursors: detection and regulation.

Since the original isolation of colony-stimulating factors from human serum, conditioned medium of murine or human cell lines, or freshly isolated human mononuclear cells, a revolutionary explosion of ideas has occurred in our understanding of molecular controls of the hematopoietic stem cell self-renewal and differentiation. With the availability of techniques of molecular cloning in the early 1 980s, the first hematopoietically activated cytokines led to molecular clones expressed in bacteria, yeast, or mammalian cellular systems. There then followed a development of techniques leading to the molecular cloning and expression of many hematopoietic growth factors and their receptors, as well as the primary, secondary, and tertiary molecules in signal transduction into activation of specific genes for differentiation or self-renewal. The clinical use of these factors in the diagnosis, treatment, and incorporation into new cell therapies for a variety of diseases is a subject of current interest.