COMPARISON OF THE COEXPRESSION OF CD38, CD33 AND HLA-DR ANTIGENS ON CD34(+) PURIFIED CELLS FROM HUMAN CORD-BLOOD AND BONE-MARROW

Human umbilical cord blood (UCB) cells are currently considered as a potential source of stem cells for transplantation. However, it remains unclear whether a single collection of UCB contains enough progenitors to allow a successful engraftment in adult patients, We were interested in the comparison of the frequency of primitive progenitors in UCB and in human bone marrow (BM), UCB and BM CD34(+) cells were purified and compared for their coexpression of CD38, CD33 and HLA-DR. UCB and BM mononuclear fractions were enriched in CD34(+) cells using the CEPRATE(TM) LC system (CellPro, Bothell, WA), Double-labeling analysis with a flow cytometer showed that 67.9 +/- 7.2% of UCB CD34(+) cells are CD38(-), while in BM only 10.9 +/- 4.9% of CD34(+) are CD38(-) (p < 0.001). Moreover, our study indicated that a significantly higher percentage of UCB CD34(+) is CD33(-) (97.1 +/- 1.2%) compared to BM (61.8 +/- 8.6%) (p = 0.013), The coexpression of CD34 with HLA-DR was not significantly different in UCB and in BM (respectively, 86.3 +/- 2.7% and 92.7 +/- 5.1%), On the other hand, in vitro assays showed that the number of multipotent (colony-forming units granulocyte-erythroid-macrophage-megakaryocyte [CFU-GEMM]), myeloid (colony-forming units granulocyte-macrophage [CFU-GM]) and erythroid (burst-forming units-erythroid [BFU-E]) progenitors is lower in the CD34(+) population from UCB than from BM. In conclusion, in UCB, we have found a significantly higher percentage of CD34(+) cells which lacked the expression of CD38 and CD33 antigens suggesting that UCB contains higher proportions of immature progenitor cells (CD34(+)CD38(-) and CD34(+)CD33(-)) than BM. It seems thus likely that fewer UCB CD34(+) cells than BM CD34(+) cells would be required for sustained engraftment following transplantation.