Biologic Characterization

Comparative flow cytometry analyses of the cellular content of UCB, BM, and PB units have been performed.3839 The absolute number of pluripotent HSCs was significantly reduced in UCB units as compared to BM and PB units. A mean of 0.21 X 106 cells/UCB unit was approximately 1/10 that of the other sources, but these HSCs were present at a higher frequency (UCB 3.39%, BM 1.47%, PB 1.82%). UCB units also possessed a significantly lower absolute number of myeloid-committed HSCs (26-65 fold) and fewer total lymphocytes (0.59 X 109 cells/unit) as compared to BM and PB sources. Of these lymphocytes, the frequency of B cells in UCB samples (18.5%) was similar to BM units and approximately twice that of PB units. The percentage of B-lineage-specific HSCs was greater in UCB units (3.79%) as compared to PB units, although no difference was detected in the frequency of immature CD19+CD20~ B cells and mature CD19+CD20+ B cells. The proportion of T cells in UCB samples (58%) was similar to that of BM, both of which were decreased as compared to PB samples (71.2%). T-lineage-specific HSCs were present at a three- to fourfold higher frequency in UCB units (12.1%) as compared to BM and PB units. UCB units also had a higher frequency of naïve CD45RA+CD45RO~ CD4+ and CD8+ cells. The percentage of NK cells (CD3CD16/56+) was highest in UCB units as compared to that in BM and PB sources (24.8%, 15.0%, and 8.5%, respectively).

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