What is Cord Blood?
After a baby is born and the
umbilical cord is cut, some blood remains in the blood vessels of the
placenta and the portion of the umbilical cord that remains attached to
it. After birth, the baby no longer needs this extra blood. This blood
is called placental blood or umbilical cord blood: "cord blood" for
short.
Cord blood contains all the
normal elements of blood - red blood cells, white blood cells, platelets
and plasma. But it is also rich in hematopoietic (blood-forming) stem
cells, similar to those found in bone marrow. This is why cord blood
can be used for transplantation as an alternative to bone marrow.
Cord blood is being used
increasingly on an experimental basis as a source of stem cells, as an
alternative to bone marrow. Most cord blood transplants have been
performed in patients with blood and immune system diseases. Cord Blood
transplants have also been performed for patients with genetic or
metabolic diseases. More than 80 different diseases have been treated
to date with unrelated cord blood transplants. [Click here to see a list of diseases treated with cord blood from the NYBC's National Cord Blood Program (PDF)]
Scientists are investigating the
possibility that stem cells in cord blood may be able to replace cells
of other tissues such as nerve or heart cells. Whether cord blood can
be used to treat other kinds of diseases will be learned from this
research.
1. Cord blood donated to a public bank
provides another source of hope for patients who have no matching donor
in their own family, no unrelated donor in bone marrow donor registries
that is a suitable match or no time to find a donor. As with bone
marrow, cord blood stem cells may be capable of generating all the
cellular elements in the blood and immune system.
2. Donated bone marrow or
peripheral blood containing mobilized stem cells have been the
traditional sources of hematopoietic stem cells for transplantation.
Their donors should be closely matched to the recipient; that is,
matched at least for the HLA-A, -B, -C and -DRB1 alleles. Since there
are usually two alleles for each, in a perfect match, the donor will
have the same eight alleles as the patient, an 8/8 match. A perfect
match is most likely to occur among family members. Among brothers or
sisters of a patient, for example, each has a 25% chance of being a
perfect match. Because the average number of children in U.S. families
is slightly more than two, about 3 out of 10 patients will find such a
match among their own siblings. Other blood relatives also may be
well-matched but the chance is much lower.
When no relative is available,
some other source of stem cells must be found. Bone marrow from
unrelated donors has helped solve this problem for thousands of
patients. Marrow donor registries around the world have recruited
fourteen million volunteers willing to donate their bone marrow to a
perfect stranger. The largest registry in the United States is the
National Marrow Donor Program (NMDP) currently, the “Be the Match”
Registry, which lists some 5.5 million volunteers.
3. Many patients who need a bone
marrow transplant, however, cannot find a suitable donor - no relative
that matches and no match among volunteer bone marrow donors. According
to a report from the U.S. Government Accounting Office (GAO) released
in October 2002, 10,000-15,000 people in the U.S. each year have a
disease that could be treated with a transplant, but have no
HLA-matched related donor. About one-third of these patients tried to
find unrelated marrow donors through the NMDP but only 25% of them (9%
of the total who might benefit) actually could get a transplant. The
odds were even worse for African-American and other ethnic minority
groups. This was one reason for the broad legislative support behind
the Stem Cell Therapeutic and Research Act of 2005.
4. A cord blood transplant may
not have to be a perfect match to the patient. Adult bone marrow
contains immune cells (so-called T-lymphocytes or T-cells) that are
“fully mature”. When transplanted, these T-cells may attack the
patient's cells as “foreign”, causing a condition called graft vs. host
disease (GvHD), which can be severe and even lethal. T-cells in cord
blood do not appear to be as "immunologically mature" as those in bone
marrow. As a result, cord blood transplants may be less likely than
bone marrow to cause GvHD and, when it does occur, it appears to be
less severe. [Click
here to read more about the advantages of cord blood].
Because cord blood transplants may cause less GvHD, it
appears that the match to the patient does not need to be perfect. In
fact, most cord blood transplants so far have been 5/6 or 4/6 matches
for HLA-A, -B and -DRB1 antigens. This means that patients who cannot
find a perfectly matched bone marrow donor may have a chance to find a
suitable cord blood transplant. Patients with rare HLA types,
African-Americans and members of other minority groups, therefore, could
benefit especially from this stem cell resource. [Click here to read about cord blood's significance for ethnic minorities]. for more read
http://www.nationalcordbloodprogram.org/qa/why_do_we_need_it.html
http://www.nationalcordbloodprogram.org/qa/why_do_we_need_it.html
