Biomedical Engineering Reference
In-Depth Information
Fig. 9.4
Positive immunomagnetic CD34
+
cell selection
The “naive” nature of UCB lymphocytes also permits the use of HLA-mismatched
grafts at 1-2 loci without higher risk for severe GvHD relative to BM transplant
from a full-matched unrelated donor. On the other hand, UCB is rich in primitive
NK cells, which possess impressive proliferative and cytotoxic capacities and can
induce Graft versus Leukemia (GvL) effect. The use of UCB is an accepted cell
source for pediatric patients for whom smaller cell count is enough for engraft-
ment, and for whom a matched unrelated allogeneic BM or peripheral blood SC
donor is unavailable. However, a higher risk of graft failure was noticed in children
weighing ³45 kg. Since the number of SCs in UCB is limited and the collection
can occur only in a single occasion—its use in adult patients can be more problem-
atic [
22-
25,
36
] .
UCB volume is typically 100 mL (range 40-240 mL) with a TNC count » 1 × 10
9
and CD34
+
approximately 3 × 10
6
per unit. UCB can easily be cryopreserved, thus
allowing for the establishment of HLA-typed SC banks. Because UCB-derived SC
banking requires high financial investment and organizational efforts, banking
efficiency should be optimized. An important determinant of banking efficiency is
the ratio of collections that can be cryopreserved and supplied for transplant.
Although there were reasons for removing UCB units that may be less amenable to
improvement, such as low volumes and low cell counts, a number of obstetric fac-
tors influencing the outcome of collections could be evaluated further, including the
time of cord clamping, length of gestation, length of labor, newborn's body weight,
and weight of the placenta [
24,
36
] .
