Introduction and overview of hematopoietic growth factors.

Blood cell development is regulated by a variety of hematopoietic growth factors that mediate the growth, maturation, and activation of hematopoietic cell elements. Several of these factors have been isolated and are now being produced by means of recombinant DNA techniques in quantities sufficient for study and clinical use. Three factors in particular have recently received considerable attention in the clinical arena: recombinant human granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF), and erythropoietin (EPO). Although both may prove to be clinically useful, G-CSF and GM-CSF have distinct and different biological characteristics. The regulatory action of G-CSF is apparently lineage-specific for the proliferation and maturation of neutrophil granulocytes. GM-CSF is less restricted in its actions, affecting all granulocytes, especially eosinophil granulocytes. It also stimulates the proliferation and activation of monocyte-macrophages and induces these cells to produce a number of cytokines. EPO mediates the growth of erythroid progenitors into mature erythrocytes. The CSFs and EPO have many potential clinical applications, including enhancing myeloid effector cell production and function, rendering malignant cells more susceptible to killing by cycle-specific agents, and correcting the anemia of end-stage renal disease.