An organ transplant is a medical procedure in which an organ from one person (the donor) is surgically removed and then implanted into another person (the recipient). This can be done because the body's immune system will usually accept organs from other people, as it recognizes them as "foreign" and mounts an attack against them. However, in some cases, this can lead to a rejection of the transplanted organ by the recipient's immune system, which is why anti-rejection medication may be prescribed after such procedures. Organ transplantations are often performed when organs fail or have been damaged due to disease or injury, and they can save lives or significantly improve a person's quality of life. Common organ transplants include heart, liver, kidney, lung, pancreas, and intestine transplants.