Review article: Molecular physiology of granulocyte-macrophage colony-stimulating factor

EMATOPOIESIS IS A quantitatively imposing pro- H cess in the adult, where about 3 x lo9 erythroid cells/kg and lo9 myeloid celis/kg are generated each day. Twenty-five years ago, in vitro assays were developed to detect factors that could stimulate the growth of colonies from immature bone marrow (BM)-derived progenitors.'.' These systems have made it possible to identify and characterize the factors regulating myelopoiesis. The appli-cation of molecular biologic approaches to study he-matopoiesis facilitated the cloning of genes encoding the hematopoietic growth factors and their production in mam-malian cells, yeast, and bacteria in quantities sufficient for in vitro and in vivo studies. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is one of a family of glycopro-tein cytokines that have potent effects in stimulating prolif-eration, maturation, and function of hematopoietic cells. Although GM-CSF was the first, several hematopoietic growth factors are now used in clinical trials. Most of the effects observed using GM-CSF in vitro have been shown to occur in vivo either in animal models or in human subjects. In this review, I shall summarize the basic science studies on GM-CSF, because others have recently reviewed the literature on the clinical applications of GM-CSF and other hematopoietins.'-&apos