A kill normal cells of the myeloid lineage and kill other cells that produce hematopoietic cytokines. Injection of a cytokine such as G-CSF, which stimulates myelopoiesis under normal circumstances, accelerates the recovery of myeloid cells following cytotoxic therapy in cancer patients or following immune-depression treatment for blood cell transplantation. Injection of this cytokine to bone marrow or peripheral blood cell donors before grafting and injection after grafting can increase the success of blood cell transplants. Because of the important functions of mature cells such as granulocytes and other myeloid cells, the increased survival and function of mature cells induced by CSFs can also be clinically helpful to patients with deficiencies in myeloid cell production and functions (reviewed in ref. 27). The finding that apparently normal granulocyte development can be induced in culture with cells from patients with infantile congenital agranulocytosis (8, 121) has led to promising clinical results with G-CSF in children with this genetic disease (122). It has also been shown that injection of erythropoietin, which stimulates the development of erythroid cells, can correct the anemia in patients with chronic renal failure (123).