Biomedical Engineering Reference
In-Depth Information
of comparatively high numbers of HSCs in cord blood, the difficulty
of finding donors that match patients, and the lack of sufficient
numbers of bone marrow donors worldwide (Cairo and Wagner,
1997). Clinicians started using adult peripheral blood as an
alternative source of HSCs for treating individuals in cases where a
bone marrow donation could not be done (Cairo and Wagner,
1997). But when umbilical cord blood was shown to have higher
numbers of HSCs than peripheral blood - numbers that were on a
par with bone marrow - the desirability of using umbilical cord
blood instead was established.
The use of umbilical cord blood also means that a crucial problem
in the donor matching process can be overcome, namely the amount
of time it can take for an appropriate bone marrow donor to be
found (Kline, 2001). Given that many patients die while waiting for
a donor, the fact that cord blood can be frozen until needed
overcomes this difficulty (Kline, 2001). Another advantage is that
cord blood is argued to be less immunologically complicated than
bone marrow, thus making the process of tissue matching a little less
arduous and resulting in better outcomes for patients (Kline, 2001).
The process of tissue matching of bone marrow donors requires
up to six pairs of the cell markers known as haploid leukocyte
antigens (HLAs) to match (Kline, 2001). HLAs are found on the
surface of cells in bone marrow and are recognized by an individual's
immune system as either 'self' or 'non-self' (Kline, 2001). That is, if
the donor tissue matches all six markers (which is, unfortunately,
highly unlikely, with only a 25 per cent chance that even siblings will
have the same markers) then the tissue will be accepted by the
recipient (Kline, 2001). If the donor tissue does not match that of the
recipient, then the donor tissue is killed off by the recipient's immune
system, as the body recognizes it as foreign and treats the donor
tissue as though it is a virus (Kline, 2001). In immune-compromised
individuals, however, the donor tissue can actually kill the recipient's
tissue, in the most severe cases causing serious bodily dysfunction
and often ending in the death of the recipient in a disease known as
Graft versus Host Disease (Kline, 2001).
Umbilical cord blood, by contrast, does not have the fully
developed HLAs found in bone marrow from children and adults
