Marrow or "bone marrow" is the soft tissue in the cavities of bones that is involved in the production of all blood cells in the body. Every year, thousands of people need donated marrow to treat a range of diseases and blood disorders.
The crucial element in marrow is blood stem cells, immature cells from which all blood cells develop. Most blood stem cells develop into new red blood cells, white blood cells, and platelets; some also divide to form more stem cells. Those that float in the blood system are called peripheral blood stem cells.
Marrow transplants are used to treat many serious illnesses including aplastic anemia, severe combined immune deficiency, sickle cell anemia, and a range of cancers including leukemia, Hodgkin's disease, malignant lymphomas, multiple myeloma and solid tumors.
If the transplant is successful, the new transplanted marrow makes a home in the recipient's bones and begins to divide into more stem cells and produce normal healthy blood cells.
Whenever possible, patients donate marrow to themselves, in large part because the transplant is much more likely to succeed. This is called an "autologous" transplant and it is the most commonly performed marrow transplant.
In typical autologous transplants, marrow taken from patients is irradiated to kill any malignant cells in it. In the meantime, heavy doses of chemotherapy and radiation, designed to kill the patients' cancerous cells may also destroy their remaining bone marrow. With the patients in strict quarantine because their immune systems are seriously compromised, the "cleansed" marrow is then transplanted back into them.
When an autologous transplant is not possible or desirable, marrow must come from a living donor. Marrow donors must be between 18 and 60 years old, and have no history of hepatitis, heart disease, cancer or HIV/AIDS.
A common, life-threatening effect of a transplant with marrow from a donor is graft-versus-host disease (GVHD). This occurs when the donor's lymphocytes-immune system cells that are always present in marrow-attack the recipient.
The best way to avoid or minimize GVHD is to use marrow from a brother or sister whose marrow has human leukocyte antigens (HLA) that are perfectly matched with the patient's HLA. Every person has three sets of HLA, and inherits one part of each set from each parent. Thus, the chance of a perfect match between siblings is one-in-four.
When a perfectly matched donor is not available, other immediate family members, and then extended relatives, are tested. At the same time, a computerized search for a match is made on donor registries. Unlike organ and tissue transplantation, for which variables like ethnicity and race are irrelevant, an individual is more likely to find a transplantable marrow match from people with a similar biological or ethnic background.
The odds of identifying an unrelated compatible marrow donor are about 1 in 20,000, and a bit higher within some ethnic and racial groups.
When people sign up with a marrow registry to be donors, they give blood, which is tested to find its HLA characteristics. This data is then entered into the registry's database. The cost is about $60 per person. Government and other programs often pay such charges, which are also tax deductible.
Many donor registries exist in the U.S. including the National Marrow Donor Program; most share information in helping to match donors with recipients.
Once a donor and recipient are matched, one of two procedures is used to take marrow from the donor:
Marrow is taken through a needle placed into the donor's pelvic (hip) bone while the patient is under anesthesia. The procedure is performed in a hospital operating room and takes 1 to 2 hours. Donors typically give about 2 to 3 percent of their marrow, which grows back within a few weeks.
For 4 to 5 days before transplantation, donors are given a drug called filgrastim to increase the number of stem cells in the blood. These stem cells are then removed over a 4 to 5 hour period. This is done through a process called apheresis in which the blood flows from an intravenous needle in the donors' arm through a machine that extracts stem cells and returns the rest of the blood through a needle in the donor's other arm.
The marrow or the blood stem cells are collected in sealed plastic packs - similar to blood collection packs - and placed in a special container, which is hand-carried to the patient's transplant center.
The marrow or stem cells are transfused directly into the patient's blood via an intravenous needle in the arm. In a successful transplant, the transplanted cells begin to function and multiply just like they were the patient's own.
The umbilical cord from a newborn baby is a good source of blood stem cells. Because cord cells are all so immature, they may elicit less of an immune response and also have less chance of causing graft-versus-host-disease than do marrow and blood stem cells taken from an adult donor. Since the first cord blood stem cell transplant in 1988, more than 2,000 have been done worldwide.
There is no cost to donate cord blood. Expectant mothers should consult with their doctor or contact their local blood bank, since arrangements must be made prior to delivery. Potential cord blood donors must sign a consent form and give a medical history and a blood sample to rule out presence of any infectious disease.
Following the baby's birth, the umbilical cord is collected, frozen and stored for future use by patients in need of transplants.
For more information about marrow donation, visit the National Marrow Donor Program at http://www.marrow.org/.