Interleukin-3. Its biology and potential uses in pediatric hematology/oncology.

The hematopoietic growth factor interleukin (IL)-3 is a potent regulator of blood cell proliferation. It promotes the survival, proliferation, and development of hematopoietic stem cells and committed progenitor cells of the granulocyte-macrophage, erythrocyte, eosinophil, basophil, megakaryocyte, mast cell, and lymphocyte lineages. In addition, IL-3 enhances mature myeloid cell functions such as phagocytosis and activation of basophils and eosinophils, as well as monocyte cytotoxicity. The first phase of clinical trials suggested that IL-3 may augment myelopoiesis in a number of clinical conditions. It may be efficacious for treatment of primary marrow disorders, including myelodysplastic syndromes and aplastic anemia. However, replacement therapy with IL-3 alone is probably not sufficient to obtain maximal stimulation of myelopoiesis. Preclinical and clinical studies published to date suggest that sequential use or combinations of growth factors will be needed to obtain optimal hematopoietic responses.