Donor Choice and Screening
Transplanted stem cells can come from the patient (autologous), an identical twin (syngenic), or a different individual (allogenic)(1). In the case of allogenic transplant, siblings are the first choice for donor cells. When a sibling is unavailable or not a match donor cells are found from a marrow donor registry program(2). These programs have lists of willing donors. For a donor to be considered they must match with the patient for at least 5 out of 6 HLA markers.
Before a stem cell donor is chosen, they must pass a thorough health exam(3). This includes an electrocardiogram, chest x-ray, blood chemistry, and blood count. The donor is also tested for various viral infections including, hepatitis, human immunodeficiency virus (HIV), and cytomegalovirus (presence of antibodies to CMV does not necessarily exclude a person from being a donor)(4).
There are three main sources of stem cells; donor bone marrow, donor blood, or cord blood(5).
Donor Bone Marrow
Marrow donation is a surgical procedure, done in an operating room under general anesthesia. A needle is inserted through the skin and into the pelvic bone and marrow is removed. This procedure is repeated until several pints are removed. The donor remains in the hospital until they recover from the effects of anesthesia and pain(5). The marrow is filtered, processed, and given to the recipient usually within 24 hours.
Donor Blood
Stem cells regularly leave the marrow and enter the bloodstream, but under normal conditions there are not enough of them (in the blood) for a successful transplant. Doctors can give a drug that encourages the stem cells to leave the marrow at a much higher rate. This drug is given to donors days before the cells are collected. On collection day the donor undergoes apheresis(5), a process where donor blood is passed through a machine that separates the blood into 4 components; blood plasma, red blood cells, white blood cells, and platelets (learn more about the blood - CBC). The stem cells are located in the platelet and white blood cell components so they are kept, but the rest of the blood is put back into the donor's body.
Cord Blood
Cord blood is taken from the umbilical cord and placenta after childbirth. Children and small adults can receive a transplant with cord blood stem cells. The umbilical cord and attached placenta are drained immediately after childbirth and the cells are frozen for later use.
Stem Cell Infusion
The infusion of stem cells is not much different from a regular blood transfusion. After the stem cells are harvested and processed, they are ready to be given to the recipient. The cells are collected in a blood transfusion bag and infused intravenously (through a vein) either through an IV or a vascular access device (VAD). Infusions may last several hours and patients are checked for signs of a reaction. Signs of a reaction may include fever, chills, hives, a drop in blood pressure, shortness of breath, nausea, and headache. Reactions are rare and can usually be easily managed.
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