Inside the bones of the body is a soft substance called marrow. It may need to be replaced if damaged. A bone marrow transplant involves transplanting healthy stem cells from a donor into a patient's body. For this reason it is also called stem cell transplant (SCT). Just as blood has multiple groups, stem cells also have multiple tissue groups, called HLA (human leukocyte antigens). HLA match between donor and recipient is essential in this transplantation.
* Autologous transplant
In this case the patient himself is the donor. In some cancer treatments, good stem cells are collected from the patient's body before high dose chemo or radiation. The stored cells are transplanted two days after the chemo has completely depleted the bone marrow. In this case, since the patient himself is the donor, the question of HLA match does not arise.
Allogeneic transplant
In this case the donor will be another person. There are several types of this substitution-
* Matched Sibling Transplant: We get HLA from our parents at birth. So it is possible to have 100 percent HLA match between brothers and sisters. But there are exceptions. Although less in number, in some cases there is no HLA match between siblings.
* Haplotype Mismatched Transplant: In this case either of the parents is the donor. Since the mother and father come from two separate families, up to 50 percent of the child's HLA match is possible with either of them.
* Matched unrelated transplant: In this case the donor is an unknown person outside the family. A computer matches the recipient's tissue group to match the donor. However, this method is quite time consuming and expensive. But this is the only way to have a completely successful transplant outside of a matched sibling transplant.
Umbilical cord blood transplant: In this case, stem cells are collected from the umbilical cord of the newborn and transplanted. Before the transplant, the donor is given a growth factor injection. This injection stimulates the blood to bring the stem cells into the bloodstream. After collecting it, the stem cells are injected into the patient's blood through a vein, which travels through the blood circulation system to all the bones in the body. It is transplanted there and starts producing normal blood cells. This is called engraftment. The stem cell transplant is done two days after chemotherapy has drained all the marrow from the patient's bones. This evacuation time is quite risky. At this time, there is a risk of various types of infections as the body has no immunity at all. In allogeneic transplantation, it takes about two to three weeks for the donor's stem cells to become the patient's own cells. Different infections can occur in the body even during adaptation of the 'foreign body' i.e. the donor cell to the recipient's body. But in autologous transplantation, the patient is the donor himself, so there is no problem of GVHD in this case. Before and after the transplant, the patient is kept in the hospital for several days with medical support and under the observation of an experienced doctor.
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