HUMAN UMBILICAL-CORD BLOOD - IMMUNOPHENOTYPIC HETEROGENEITY OF CD34(+) HEMATOPOIETIC PROGENITOR CELLS

Background. Human umbilical cord blood (HUCB) is a possible alternativ e to bone marrow (BM) and mobilized peripheral blood (PB) for transpla ntation of hematopoietic progenitors. The aim of this study was to eva luate the phenotypic profile of CD34(+) progenitors present in HUCB. M aterials and Methods. A flow cytometric analysis was performed on 20 H UCB samples, using a large panel of monoclonal antibodies recognizing different lineage or activation antigens, in double labeling with CD34 . Results. A total of 13,897 +/- 2,529 cells/mu L, 0.84 +/- 0.83% of w hich were CD34(+), was found. The large majority of CD34(+) cells were committed toward initial myeloid differentiation (CD33(+), CD13(+)) a nd expressed the transferrin receptor (CD71). A substantial proportion of these cells (about 40%) co-expressed CD45RA and CD117, while a ver y small number displayed markers of advanced myeloid commitment, such as CD14, CD15 and CD41 (less than 2%), or those of lymphoid differenti ation: CD2, CD5, CD7, CD10 and CD19 (less than 6%). About 11% of HUCB CD34(+) cells were primitive progenitors, as suggested by the absence of HLA-DR and CD38 on their surface. Conclusions. As previously observ ed in BM and mobilized PB, the phenotype of HUCB CD34(+) cells is quit e heterogeneous. In particular, HUCB contains subpopulations of both e arly and committed hematopoietic progenitors which may represent a val id source for transplantation.