Analysis of the expression of adhesion molecules on CD34+ progenitors from bone marrow, umbilical cord blood and G-CSF mobilized peripheral blood

Umbilical cord blood (UCB) and leukapheresis products (LP) are increasingly used as an alternative source of CD34+ hematopoietic progenitor cells (HPC) in transplantation settings. We have investigated 35 samples of LP, 12 of UCB and 9 of bone marrow (BM) to assess possible differences in the expression of adhesion molecules (CAMs) and differentiation antigens. Such expression was also evaluated in terms of mean fluorescence intensity ratio (MFIr) obtained dividing the MFI of the positive sample by that of the isotype matched control. The highest percentage of hematopoietic progenitors cells (HPC) was found in LP (P = .002). Conversely, CD34 MFIr was higher for UCB HPC (P = .012). Progenitors from UCB and BM showed a large percentage of CD49d (P = .002) with an higher MFIr (P 90% of CD34+ cells from the 3 sources. CD13 and CD33 showed a lower expression on BM HPC. An higher percentage of CD34+/Thyl+/ HLA-DR(=) cells was observed in UCB while CD34+/CD38+/HLA-DR- and CD34+/CD38-/HLA-DR- cells predominated in BM. In conclusion, LP is the richest source of CD34+ progenitors while UCB precursors showed more numerous CD34+/Thyl+ cells and a 'dim' expression of C-kit: both characteristics belong to more clonogenic precursors. UCB progenitors expressed a CD49d and L-selectin MFIr which were similar to that of BM and LP stem cells, respectively. Both LP and UCB have a pattern of adhesion and differentiation molecules consistent with the presence of long term proliferating HPC, this explains, at least in part, why they may represent a valid alternative to BM as a source of CD34+ progenitors for transplantation.