Effects of recombinant human interleukin-3 in aplastic anemia.
 In a phase I/II study, nine patients with aplastic anemia were treated with recombinant human interleukin-3 (rhIL-3) to assess the toxicity and biologic effects of this multipotential hematopoietic growth factor.
 Doses ranging from 250 micrograms/m2 to 500 micrograms/m2 were administered as subcutaneous bolus injections daily for 15 days.
 An increase in platelet counts from 1,000/microL to 31,000/microL was induced by rhIL-3 in one patient, and an increase in reticulocyte counts by more than 10,000/microL in four patients.
 The blood leukocyte counts temporarily increased in eight patients 1.5- to 3.3-fold (median, 1.8-fold), mainly due to an increase in the number of neutrophils, eosinophils, lymphocytes, and monocytes.
 In two patients, bone marrow cellularity increased from 7% to 33% and from 10% to 80%, respectively, but without resulting in a substantial improvement of peripheral blood counts.
 Mild side effects (headache and flushing) were observed in some patients, while low-grade fever occurred in all patients.
 Transient thrombocytopenia necessitating discontinuation of rhIL-3 treatment occurred in one patient.
 In conclusion, rhIL-3 can stimulate hematopoiesis in patients with aplastic anemia; however, no lasting effects were obtained.
