For a bone marrow transplant finding the right donor can be hard. Usually parents and family members can be tested to avoid issues of graft-versus-host-disease (GvHD) as a biological parent and a sibling’s genes have greater compatibility.
Bone marrow is a spongy tissue found inside of our bones; it has immature cells called stem cells. It is responsible for creating RBC, WBC, and platelets which are crucial components of blood. A bone marrow transplant is carried out to cure many diseases; it is a procedure to replace the faulty bone marrow with a healthy one. The new and healthy bone marrow will ensure patient's recovery.
A bone marrow transplant is performed in two ways- with patient’s own healthy stem cells, if available or with the help of a donor. A donor can be anyone from the family like parents, siblings or relative or it can be a total stranger too. Special tests are performed to find the suitable donor such as human leukocyte antigen (HLA) or histocompatibility typing and DNA typing. With a greater difference in the match of these tests, higher the chance that the donor’s cells will not accept the transplant resulting in failure which will cause a reaction called graft-versus-host disease (GvHD).
To find an ideal match of the donor is rare, thereby performing tests on all possible family members is recommended. Following are four types of donor categories which can fulfill the desired needs of the patient :
1.Matching donors : the donor is histocompatible with the patient who happens to be a relative or sibling, which is rare. Also known as identical tissue typing. The donor is HLA match who is a relative, sibling, parent or a grandparent with same HLA tissue typing. Every one of us has two sets of chromosomes (one from the father and one from the mother) with 4 genes per set. There is one in four or 25% chances that any sibling will inherit the exact same sets of HLA genes as of the patient. Hence, the probability of having the same set of genes in sibling is mere 25%. Hence, not every family member can be a bone marrow donor.
2.Partially matched donors : a biological parent is always a half-match since the child inherits half of the total genes from each of the parent. But to use these partially matched cells, they are treated especially before the transplant to avoid the severe case of GvHD.
3.Autologous donors : in this type of transplant, the oncologist uses patient’s own healthy cells prior to the transplant surgery. For treatment of brain tumor, lymphomas, sarcomas, etc. this procedure can be used. The cells are harvested and freeze until the main transplant surgery. The main advantage of this surgery is an absence of GvHD while the biggest risk is relapsing of cancer.
4.Alternative donors : there are two types of alternative donor namely-unrelated donors and umbilical cord cells.
These are the donors with no connection at all with the recipient. Unrelated donors if willing to donate their own bone marrow if matched, can be used for the replacement. Also, the umbilical cord cells are harvested right after the birth. These cells are stored and preserved until used for a transplant. Since these are immature, budding cells, so the risk of GvHD is minimalized.
Considering the fact that the bone marrow transplant surgery requires the closest match. The oncologist looks for the best match in order to avoid GvHD. With that being said, the chances with family member narrow downs to 25%, which can cause a failure of the transplant. The commonly asked question to the oncologist whether or not a family member can be a donor to the patient? As discussed there is a narrow chance with a sibling or any of the parent. But it is worth to look for a donor within the family since to find a donor on the waitlist can be exhausting. With proper consultation and guidance, a donor can be found.