[The determination of myeloid-committed stem cells in systemic disorders of myelopoiesis: implications for physiopathology, diagnosis and prognosis].

Myeloid committed stem cells belong to a subpopulation of small nucleated cells, which are defined by their capacity to form colonies of mature myeloid cells in agar-medium. They are termed "Colony forming Unit, CFUC", and such cells are detectable in bone marrow and peripheral blood. Bone marrow cells from 15 control patients with regular myelopoiesis contained 86 +/- 46 CFUC/10(5) bone marrow cells and 23 +/- 14 CFUC/ml blood. In 10 patients with aplastic anemia, only 0-10, 5 CFUC/10(5) BM-cells were found and no CFUC were detectable in the peripheral blood. 17 patients with chronic myeloid leukaemia showed a moderate elevation of bone marrow CFUC (X = 105), while the circulating CFUC were markedly elevated (105-42.000/ml). The circulating CFUC were closely correlated with the number of leukocytes (p less than 0,001). In 12 patients with primary osteomyelofibrosis, the number of circulating CFUC was also (raised (325-22.199/ml) and again, a correlation with the number of leukocytes was observed (p less than 0,05). As, on the other hand, there was no difference in the leukocyte count between the control group and patients with osteomyelosclerosis, the simultaneous assessment of circulating leukocytes and CFUC proves a diagnostic tool. Pancytopenia with a hypercellular bone marrow results from either neoplastic or metabolic alterations of haemopoiesis; in pancytopenia with neoplastic infiltration or transformation, the number of CFUC was lowered, whereas it was slightly elevated in pancytopenia due to metabolic alterations. In patients with acute leukaemia, only a minority of cells was capable of proliferation in vitro. The growth of leukaemic cells in culture, their prolonged survival along with the expression of functional properties may be clinically used for a more subtle classification of blast populations. The data on patients with acute leukaemia indicate, that basic mechanisms of normal blood cell regulation operate in leukaemic haemopoiesis as well.