ICSBP-transcript numbers, increasing upon in vivo treatment with IFN-α, correlated with impairment ofbcr-abl-transcript (•), leukocyte (□), and lymphocyte (▪) numbers. The sample at diagnosis exhibits few ICSBPtranscripts, even with only 1% blast cells (lane 1). Samples during IFN-α treatment showed an increase of ICSBP (lane 2: after 3 weeks, bone marrow; lane 3: 6 weeks; lane 4: 36 weeks), and a decrease of ICSBP after IFN-α was withdrawn (lane 5: 68 weeks). The mean of three experiments is displayed. All analyzed metaphases during the patient's course were 100% Philadelphia-chromosome positive. The relative equivalence points (EP) of bcr-abl and the reference gene, pbgd, were determined by quantitative PCR.