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Colony-stimulating factors in the pathogenesis and treatment of disease.

Clinical trials of colony-stimulating factors in the treatment of various haematological and infectious diseases have been initiated. This review summarizes the recent evidence from studies in vitro and in vivo which provide support for the role of these haemopoietic growth factors in the pathogenesis and potential therapy of such conditions. The production of haemopoietic cells is dependent on the sequential actions of glycoprotein growth factors at all stages from the multipotential stem cell in the fetal liver or adult bone marrow to the mature cell in the periphery. The characterization of these growth factors over the past 20 years followed the initial observation that the growth of single haemopoietic progenitor cells to form colonies in vitro depends on the presence of exogenous stimuli, hence the generic term 'colony-stimulating factor' (CSF).' The CSFs induce the proliferation of progenitor cells and influence their progressive commitment to various differentiation pathways, and they have been classified according to the specific lineages on which they exhibit their most obvious effect. For example, erythropoietin (Epo), perhaps the haemopoietic growth factor most familiar to clinicians, acts relatively late in the erythroid differentiation pathway, stimulating both proliferation and haemoglobinization. However, this review will be restricted to a discussion of the non-erythroid CSFs which include multi-potential CSF (Multi-CSF, interleukin 3), granulocyte-macrophage CSF (GMCSF), granulocyte CSF (G-CSF), macrophage CSF (M-CSF) and eosinophil CSF (Eo-CSF, interleukin 5) (Figure 1). Recently the use of recombinant DNA technology has allowed molecular cloning ofthe genes encoding most of these factors, their expression in bacteria, yeast or mammalian cells, and the production of purified material in high yield for further laboratory investigations and clinical trials. Structure