Regulatory abnormalities in the marrow of patients with myelodysplastic syndromes.

Regulation of haemopoiesis in the marrow of patients with myelodysplastic syndromes (MDS) was evaluated by assaying (1) the production of haemopoietic regulators acting upon multipotent and committed progenitors by MDS marrow cells, and (2) the responsiveness of MDS marrow progenitors to stimulation with granulocyte colony-stimulating factor (G-CSF). The levels of multipotent progenitor cell colony-stimulating activity (CFU-GEMMCSA) in 7 d bone marrow-conditioned medium (BMCM) from MDS patients were markedly reduced as compared to controls. MDS BMCM also exhibited reduced levels of burst-promoting activity (BPA) for primitive erythroid (BFU-E) progenitors.