Recycling bone marrow transplantation.

Recycling bone marrow transplantation 

Traditionally, a patient's sibling has been the donor of choice for a bone marrow transplant, reducing the chance of adverse immune reactions in the recipient. But with the size of an average U.S. family decreasing, health officials worry that locating a well-matched donor is like finding a shrinking needle in an ever-enlarging haystack. Thus, researchers are remodeling bone marrow transplantation techniques so less-well-matched donors, or even the recipients themselves, can supply the necessary cells. Included in those studies are two that use specialized equipment to isolated needed cells from those that cause immune reactions.

Scientists at the University of Nebraska College of Medicine in Omaha are using the recipient's own blood, rather than the usual bone marrow from the hip bone, to supply the "primitive" stem cells that differentiate into the various types of blood cells. Autologous (where the recipient is the donor) bone marrow transplants have been used for about a decade in some cancer patients to minimize chemotherapy's devastating effect on blood cell counts. But cancer or irradiation therapy in the pelvic area, along with discomfort associated with marrow punctures, make the blood an attractive alternative.

In a recently completed study, Anne Kessinger and her colleagues treated 26 patients undergoing chemotherapy with autologous stem cells. Twenty-five quickly showed bone marrow recovery (one patient died of other causes two days after transplant). Using a centrifuge that separates cells on the basis of weight, the researchers had collected the medium-sized stem cells and returned the remaining blood to the patient. To obtain sufficient numbers of cells, six or seven daily four-hour collection sessions are necessary, says Kessinger. In addition to the time involved, another factor that must be considered is the possible transfer of cancer cells with the stem cells in those cancers that are easily spread through the bloodstream. The next step, she says, is to expand the technology so anyone can donate stem cells.

At Johns Hopkins University in Baltimore, Albert D. Donnenberg uses a method called counterflow centrifugal elutriation (CCE) to remove lymphocytes from bone marrow. Lymphocytes are white blood cells responsible for immune reactions, which can be dangerous in graft-versus-host (GVH) disease seen in bone marrow transplants but beneficial when the donor's immunity against infection is transferred to the immune-compromised transplant recipient. In a preliminary study of 32 patients, the Hopkins group removed nearly all lymphocytes from donor bone marrow before transplant. The result, says Donnenberg, was a significant reduction in GVH cases. To optimize the phenomenon of immunity transfer, the scientists also started a separate study in which the donor is injected with an antigen one week prior to marrow collection to boost immunity against specific infection. The recipient is injected with the same antigen (tetanus and diphtheria toxoids have been used thus far) on the day of transplantation.