A transplant rejection is the body's destruction of a newly
introduced organ or tissue. A person's immune system does not recognize the
cells of the transplanted material, which triggers it into action to kill the
transplanted tissues.
The immune system's response eventually makes the organ or tissue
unable to function.
Medicines are given to suppress the immune system. But
taking them can make it easy for a person to get sick. Having a suppressed
immune system makes it hard for a person to fight off all types of
infections. But transplants are usually successful.