Bone marrow transplant
Bone marrow is the spongy tissue in the cavities of the bones. It is the blood cell 'factory'. Healthy bone marrow releases blood cells into the blood stream when they are mature and when required.
For a successful bone marrow transplant, the donor needs to have the same tissue type. If the donated marrow isn't a close match, the donor's marrow will reject the recipient's body. A person's tissue type can be checked with a simple blood test. In a transplant operation, the recipient's marrow is treated with drugs and x-rays. Then the donor marrow is injected into the recipient's blood. The donor marrow finds the bones and settles into the cavities.