In vivo recruitment of GM-CSF-response myelopoietic progenitor cells by interleukin-3 in aplastic anemia.

Previous studies have indicated that colony-stimulating factors may stimulate myelopoiesis and thus increase the number of circulating white blood cells in patients with hematopoietic failure including aplastic anemia. However, long-term administration of the factor was required to maintain its response. In the present article we report on a patient with severe aplastic anemia undergoing treatment with recombinant human (rh) granulocyte-macrophage colony-stimulating factor (GM-CSF). After an initial response, the patient became refractory to GM-CSF. However, treatment with interleukin (IL)-3 restored responsiveness to GM-CSF, suggesting that IL-3 may have replenished the bone marrow with myelopoietic progenitor cells sensitive to the action of GM-CSF. This observation suggests the value of application of sequentially acting hematopoietic growth factors in aplastic anemia patients.