Colony-stimulating activity in the serum of patients with hemopoietic malignancies after intensive chemotherapy/radiotherapy: its augmentation by GM-CSF in vivo and interleukin 4 in vitro.

Colony-stimulating activity (CSA) in the serum of patients with hematological malignancies increased substantially after intensive therapy with cyclophosphamide/busulfan, cyclophosphamide/total body irradiation, or melphalan/total body irradiation. This was not dependent on patients receiving allogeneic bone marrow transplantation (ABMT) or autologous bone marrow rescue (ABMR). In 44 of 62 patients CSA was maximum approximately 7 days after chemotherapy/radiotherapy, whereas in 18 of 62 patients CSA was maximum between 9 and 20 days after therapy and decreased thereafter. The time course of CSA was not dependent on disease and was not affected by recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) given as a continuous infusion for 14 days after therapy; however, serum from patients receiving rhGM-CSF produced significantly more colonies from donor bone marrow than serum from patients who did not receive the cytokine (p = 0.013). Despite the early peak in CSA in the majority of patients, there was no correlation between the time at which CSA was maximum and the return of patients' neutrophils to 500/microliters. Recombinant human interleukin 4 (IL-4) increased the number of granulocyte-macrophage colony-forming unit colonies, principally granulocyte colony-forming unit colonies, from normal bone marrow exposed to patients' serum after intensive therapy and antibody to GM-CSF reduced colony numbers. The results suggest that after intensive therapy granulocyte colony-stimulating factor (G-CSF) as well as GM-CSF is released into the serum and, in addition to acting directly with G-CSF, IL-4 may stimulate mononuclear cells to produce and/or release G-CSF.