Granulopoiesis in Chronic Granulocytic Leukaemia*

Summary: The disappearance from the blood was studied of (1) leucocytes of patients with chronic granulocytic leukaemia labelled in vitro with DF32P and irradiated with 1500 rad, and (2) in vitro labelled normal marrow leucocytes. These studies made it possible to estimate the intravascular phase of the lifespan of mature leukaemic neutrophils and to compute the granulocyte turnover rate when immature leucocytes (myelocytes) were present in the blood. The studies support the hypothesis that immaturity of the leucocytes per se may result in their sequestration from the blood stream. The results suggest that granulocyte production is increased in chronic granulocytic leukaemia in relapse, and that the tendency for the leucocytosis to occur may be potentiated by a prolongation of the lifespan of the mature neutrophils. However, this prolongation is only manifest in the presence of leucocytosis.