BALANCE BETWEEN HUMAN PERIPHERAL-BLOOD CFU-GEMM AND CFU-MEG IN SUSTAINED AND ACUTE THROMBOCYTOPENIA

Quantitative variations of blood cell progenitors were studied in thro mbocytopenic post-chemotherapy patients and in healthy plateletpheresi s donors with the aim of better understanding in the reasons for their varying presence in peripheral blood. In 6 post-chemotherapy patients with severe thrombocytopenia on days 21-27 after initiation of chemot herapy when white blood cell counts were observed between the most and least immature progenitors: levels of CFU-Meg were significantly lowe r than control values whereas levels of CFU-GEMM were 2-fold higher th an in controls. Results suggest that an activator distinct from the kn own poietins may stimulate very immature progenitors. In 15 plateletph eresis donors, numbers of CFU-GEMM and CFU-Meg were greatly increased, respectively 5.5-fold and 10-fold, following plateletpheresis. Data o nce again indicate a major role of CFU-GEMM in the production of matur e blood cells. As the most immature progenitors and thrombocytopoiesis stimulating factor(s) are both present in peripheral blood, such fact ors may be responsible for the initial engagement of these very early progenitors into a specific cell line.