Transplant (surgery)

Transplants are a type of surgery. Both tissues and organs can be transplanted. Types of transplant:
An organ transplant is a kind of surgery where the person being operated on will need an organ replaced, and gets a healthy one from someone else, a donor. Usually the organ is taken from someone who is recently deceased, except for organs like bone marrow or kidneys, which can be taken without harming the donor too much.
The critical problem with all transplants is transplant rejection by the host's immune system. Unless the host and donor are a very close genetic match, the host's immune system will reject the transplant. To stop this happening, drugs are used to suppress, or limit, the host's immune system. This in turn makes the host more vulnerable to various kinds of infection.
To keep this problem to a minimum, transplants are only done when surgeons are satisfied that the host and donor are a fairly close match. Tests are done to see how good a match the donor's organ or tissue is to the proposed host.