More About BMT and Chimerism
Bone Marrow Transplantation
A major risk associated with a conventional bone marrow transplant (BMT) is Graft versus Host Disease (GvHD). GvHD occurs when mature immune cells (B, T and NK cells) present in the bone marrow graft recognize the recipient's body (the host) as foreign and attack it. GcHD can affect the skin, liver, and the gastrointestinal tract. In its severe form, GvHD is often fatal. In this trial, the risk of GvHD may be reduced.The second risk is failure of the new bone marrow to engraft or to take up residence in the recipient's body.
The bone marrow to be transplanted will be processed using a special technique that removes most of the mature immune cells that can cause GvHD to occur. The process also leaves behind special cells called "Facilitating Cells" in the marrow that facilitate engraftment or encourage it to take hold and start making blood cells in the new host.
This unique process for graft engineering was developed at the Institute for Cellular Therapeutics and has been tested in many leukemia patients with encouraging results.
Mixed Chimerism
A state in which two bone marrow systems are present and functioning in one person is called a "mixed chimerism". In this state both the donor's and the recipient's bone marrow produce blood cells. When both bone marrows produce immune cells that mature in one body, the two systems learn to recognize each other as part of the same body and do not attack each other. The combined system has characteristics of both systems.Part of the function of bone marrow is to generate the cells that make up a person's immune system. Many people who have BMT have serious diseases of the immune system, like leukemia, which make it necessary to wipe out (ablate) their diseased system before transplant, leaving as few as possible of their own abnormal immune cells. However, it would be better for patients with working immune systems (such as those with sickle cell disease or other genetic disorders of the blood) to retain their own immune functions, while being able to reap the benefits of BMT by the production of normal blood cells that their own body cannot make.
Mixed chimerism is also of benefit to persons who receive solid organ transplants. When a person is given the bone marrow as well as the organ of another person, the recipient's body will recognize the organ and the chances of rejection may be decreased.
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