HE PRODUCTION of differentiated hematopoietic cells
T involves a carefully orchestrated series of events involving self-renewal and differentiation of primitive pluripotential stem cells. There is a growing awareness of the complexity of the intrinsic and extrinsic controls built into the system to maintain its integrity.
The external influences are many and diverse, encompassing interactions of developing hematopoietic cells with extracellular matrix molecules, with a variety of stromal cell types and with growth factors. The area of hematopoietic growth factor (HGF) research has expanded dramatically in the last 2 to 3 years with the availability over 12 recombinant HGF materials in quantities allowing direct in vivo testing in both preclinical and clinical systems. ' HGF, variously characterized as a colony stimulating family of glycosylated polypeptides, have a biologic specificity defined by their ability to support proliferation and differentiation of hematopoietic cells of various lineages, usually in a semisolid clonal assay system.
Investigations of human granulocyte and granulocytemacrophage colony stimulating factors (G-CSF, GM-CSF), have prompting new strategies for the treatment of cancer. GM-and G-CSF are vital to the normal development of granulocytes. The factors act to accelerate the