Overview of myeloid growth factors

Initial steps in dissecting the regulatory influences on the process of hematopoiesis have involved the characterization of humoral modulators able to stimulate in vitro colony formation by myeloid progenitors. Several colony-stimulating factors (CSFs) have been molecularly characterized and produced in quantity through the use of recombinant DNA technology. Investigation of the myeloid CSFs indicate that they are potent stimulators of the production of mature neutrophils, monocytes, eosinophils, and, in some cases, augment platelets and red cell elaboration. CSFs also have important direct effects on mature circulating leukocytes. Granulocyte-CSF and granulocyte-macrophage-CSF prime neutrophils for enhanced function including enhanced oxidative metabolism, phagocytosis, and cytotoxicity. Granulocyte-macrophage colony-stimulating factor and interleukin-3 have stimulatory action on eosinophils and macrophages while the effects of macrophage-CSF appear to be limited to cells of the mononuclear phagocyte series. The development of the myeloid growth factors as therapeutic agents offers the prospect of unique strategies for enhancing overall host defense. Results of clinical trials with some of these factors suggest beneficial effects in a variety of settings.