FLOW-CYTOMETRY CHARACTERIZATION OF CD34+ CELLS IN BONE-MARROW, CYTAPHERESIS PRODUCTS, AND CORD BLOOD AT BIRTH

The average content of MNC fractions in CD34+ cells was found to be 1.16 % in normal bone marrow, (BM ; n = 10), 0.90 % in cytapheresis products after mobilization with HD cytostatics (CP ; n = 22), and 0.73 % in umbilical cord blood at birth (UB ; n = 7). In each group the size of the lineage free subfraction of CD34+ cell was determined by use of the MoAb anti CD38, which is absent in uncommitted early precursors. This minor subpopulation shows differences in all three products (5.8 % in CP vs 12 % in UB and 19.4 % in BM). Significant differences exist, if the relative size of subpopulations being committed to the different lineages are compared; for this purpose double immunofluorescence was performed with the MoAb CD71, CD33, CD10 and CD5, which are thought to be lineage specific in hematopoietic cells. The erythroid progenitors were prevalent in CP and UB (80 % and 72.2 %) and lower in BM (43.8 %); also the myeloid marker was more frequent in CP and UB than in BM (68.9 % and 69.1 % vs 32.9 %). B-cell lineage was also more frequent in CP and UB (66.7 % and 77 %) than in BM (32.4 %), as was T-cell lineage (45.4 % and 42 % vs 11.4 %). These results suggest, that circulating hematopoietic cells tend to be committed at a higher degree than those found in bone marrow.