Comparative multi-color flow cytometric analysis of cell surface antigens in bone marrow hematopoietic progenitors between refractory anemia and aplastic anemia

Abstract 

Refractory anemia (RA) in myelodysplastic syndrome (MDS) without prominent dysplasia closely resemble the mild type of aplastic anemia (AA) in their hematological features. This sometimes makes it difficult to distinguish clearly between the two diseases. Using the multi-color flow cytometric technique, we compared cell surface antigen expression patterns on bone marrow hematopoietic progenitor cells which were isolated as a CD34 positive- CD45 dull positive with low side scatter intensity (CD34⁺CD45^dull+SSC^low) population in flow cytogram between RA (n=12) and AA (n=11). The antigens analyzed in CD34⁺CD45^dull+SSC^low mononuclear cells were: CD38 and CD71 for cell growth-related antigens, CD 33 and CD13 for myeloid and monocytoid lineage-associated antigens, CD7 and CD19 for lymphoid lineage, and CD14 for a monocytic lineage specific antigen. The percentages of CD34⁺CD45^dull+SSC^low cells in bone marrow non-erythroid mononuclear cells, and the expression frequencies of CD38, CD71, CD33 and CD13 antigens in CD34⁺CD45^dull+SSC^low progenitors were all significantly decreased in AA compared to normal bone marrows (n=7) (P<0.005). In contrast, in RA bone marrows the percentages of CD34⁺CD45^dull+SSC^low cells showed wide distribution and the cell surface antigen expression patterns varied among each case: some cases showed low frequencies of CD38 and CD71 expression as well as AA, whereas the others showed high expression frequency of specific antigen(s) which may reflect the clonal expansion of an abnormal clone in bone marrow. An MDS patient who had progressed from RA to RAEB showed further projecting pattern of expression of CD38 and CD33 in CD34⁺CD45^dull+SSC^low population in accordance with the disease progression. These data suggest that analysis of cell surface antigen expression patterns of CD34⁺CD45^dull+SSC^low progenitor cells by multi-color flow cytometry appears to be a useful method for qualitative and quantitative assessment of marrow progenitor states in AA and RA, therefore this method could be helpful for early detection of clonal evolution in MDS.

Keywords: Myelodysplastic syndrome, Refractory anemia, Aplastic anemia, Flow cytometry, Hematopoietic progenitors, CD34, Bone marrow

Abbreviations: CMMoL, chronic myelomonocytic leukemia, FAB classification, French–American–British classification, MDS, myelodysplastic syndromes, nd, not done, NS, no significance, PID T_1/2, plasma iron disappearance time, post-MDS AML, myelodysplastic syndromes patients progress to acute leukemic phase, RA, refractory anemia, RAEB, refractory anemia with excess of blasts, RAEB-T, refractory anemia with excess of blasts in transformation, RARS, refractory anemia with ringed sideroblasts, % RCU, red cell iron utilization, SSC, side scatter