Bone marrow transplantation is indicated for a number of illnesses and at a specific moment in the treatment of the illness.
When the bone marrow of a patient is not functioning normally and is no longer producing normal haematopoietic stem cells, a bone marrow transplant can be proposed. Depending on the patient and his/her pathology, one of two types of transplant may be carried out :
- either an autograft, using the patient’s own bone marrow cells,
- or an allograft (or allogeneic transplant), which allows the replacement of the diseased bone marrow with an healthy bone marrow taken from a compatible donor (related or unrelated) and to use the immune system of the healthy donor to fight the recipient’s illness.
The two indications for an allograft
The purpose of a bone marrow transplant is to cure serious and often fatal illnesses such as :
- Cancerous illnesses (80% of cases)
These are leukaemias, other blood cancers and certain diseases of the lymph node system.
- Non-malignant illnesses
These include medullary aplasias, in which the bone marrow stops functioning consequently to hepatitis or poisoning or with no evident cause.
This category may also include severe infant immunodeficiencies or hereditary diseases in which the creation of red blood cells is disrupted (thalassaemia or drepanocytosis).
The steps involved in preparing the patient for the transplant
Before the transplant, the patient must undergo a transplant preparation procedure, called “conditioning regimen”, the purpose of which is to destroy the remaining malignant cells in the recipient’s body and, for marrow allografts, to destroy the recipient’s immune system in order to avoid rejection of the transplant.
The methods used are radiotherapy and chemotherapy, combined in varying degrees according to each individual situation.
How is the transplant carried out ?
Generally, the haematopoietic stem cells are injected 24-48 hours after the end of the preparation procedure.
The bone marrow is transplanted into the patient by intravenous injection, like a transfusion, as soon as possible after collection (between 12 and 36 hours).
In rare cases, frozen stem cells are thawed by immersing them in sterile water at 37°C and immediately injected into the patient’s blood.
How is the bone marrow transported ?
Bone marrow does not keep for long. It is therefore transferred from the donor to the patient as quickly as possible (between 12 and 36 hours).
Generally, after collection, the bone marrow is maintained at ambient temperature during its transfer to the place of transplantation. If the journey is too long, it may be refrigerated at 4°C.
Under specific circumstances, the bone marrow cells may be frozen for reasons purely connected with logistics’ difficulties.