The proliferative activity of myelopoiesis in myelodysplasia evaluated by multiparameter flow cytometry

Double staining of bone marrow cells for CD13 and CD33 leucocyte differentiatian antigens and for DNA content has allowed us to evaluate the proliferative capacity of myelopoiesis in patients with myelodysplastic syndromes (MDS) using flow cytometry. By analysing 39 patients (15 RA/RAS, 14 RAEB and 10 RAEB-t) and eight normal controls, we found significant differences in both the percentage of cells positive for these immature myeloid antigens between the FAB groups as well as in the fractions of CD13 and CD33 positive cells in S or S-G2M phase of the cell cycle. Moreover, a clear decrease in the immature myeloid cell proliferative activity upon progression within the FAB groups was evident. Finally, we found a significant negative association between the percentage of myeloblasts in the bone marrow and the proliferative activity of the immature myeloid cells, indicating that the block in differentiation in MDS patients might be coupled to a simultaneous block in proliferation, especially in advanced stages. These data suggest that the use of double parameter assays in the longitudinal follow-up of MDS patients might yield new information about the biology of MDS.