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Health – Bone Marrow Transplant and Transfusion

Bone Marrow Transplant and Transfusion

 

Mrs Kayon Lee  

Biomedical Scientist

 

Bone marrow is the spongy tissue inside some of your bones, such as your hip and thigh bones. It contains stem cells. . Stem cells are immature cells in the bone marrow that give rise to all of your different blood cells. The stem cells can develop into the red blood cells that carry oxygen through your body, the white blood cells that fight infections, and the platelets that help with blood clotting. It creates all your blood cells (Red blood cells, white blood cells, and platelets).  The major function of bone marrow is to generate blood cells. Bone marrow contains two main types of stem cells. Hematopoietic stem cells, found in red marrow, are responsible for the production of blood cells.

 

A Bone Marrow Transplant (BMT) is a medical procedure to replace damaged or destroyed bone marrow with healthy bone marrow stem cells.   A bone marrow transplant can be used to: Replace diseased, non-functioning bone marrow with healthy functioning bone marrow.

When your bone marrow is destroyed by infections, cancer or chemotherapy, it will not be effective in making new blood cells. This means you will be vulnerable to infections, anaemia and bleeding disorders. A patient usually needs a bone marrow transplant when suffering from:

 

• Aplastic anaemia where marrow stops making new blood cells

• Sickle cell anaemia where they have misshapen red blood cells (genetic)

• Thalassemia where the body makes an abnormal form of haemoglobin, an integral part of red blood cells (genetic)

• Congenital neutropenia where they are genetically prone to recurring infections

• Forms of cancer that affect the marrow like leukaemia, lymphoma, and multiple myeloma

• Damaged bone marrow due to chemotherapy or radiation

However, there are two different types of BMT: Autologous – Allogeneic.  In autologous transplants, a patient’s own cells are harvested from the body before chemotherapy or radiation. After this treatment, the cells are again introduced into the body. This is if the patient has a healthy bone marrow. In allogeneic transplants, the cells of a donor are used. In this case, the donor needs to be a close genetic match (often a sibling, father or mother). Sometimes, when a relative is not available, matches are even found in a donor registry. The success of this transplant depends on how close the match is.

Before the BMT, a patient undergoes:

1.Chemotherapy- to kill all cancer cells or marrow cells. Since the part of the body that produces white blood cells is compromised, the patient is vulnerable to infections.

2. Matching- this involves typing human leukocyte antigen (HLA) tissue.

3.  

The antigens on the surface of these special white blood cells determine the genetic make-up of a person’s immune system. There are at least 100 HLA antigens; however, it is believed that there are a few major antigens that determine whether a donor and recipient match. The others are considered minor and their effect on a successful transplant is not as well defined. However, because the HLA matching doesn’t utilize blood-type and the recipient’s marrow is destroyed in the process, then if the donor’s marrow produces different red blood cells – then so will the recipient with time.  The recipient’s blood type eventually changes to the donor type. That means if you had a blood type of A+ prior to transplant and your donor had a blood type of O, eventually your blood type would become O. It may take several weeks, possibly months for your original blood type to disappear, but eventually it will.

 

What is interesting is that blood-typing is not being expressly necessary with the modern bone marrow transplant process. The danger of mixing two antagonistic blood types in vivo is that the recipient’s immune system attacks the foreign red blood cells resulting in body-wide rejection. However, because the immune system’s response capabilities are decimated by the destruction of the recipient’s bone marrow (usually accomplished via chemotherapy or radiation), it can’t mount much of an attack in the first place.

 

That’s not to say the body can’t mount an attack, or that the donor’s tissue can’t mount an attack on the recipient (Graft-Versus-Host-Disease [GVHD]) – but the better the HLA match the less likely issues are to arise, which is why we do the more accurate and relevant HLA matching instead of blood-typing. This also helps to minimized complications that are associated with BMT such as graft failure, where the transplanted cells do not start creating new cells as they are supposed to, bleeding in the lungs, brain, and other parts of the body anaemia, infections, nausea, diarrhoea, or vomiting, cataracts, early menopause or even organ failure.

 

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