Tissues or organs of the body are defined as an allotransplant, if from another person; an autotransplant, if from the patient him or herself – for example, a skin graft (see GRAFT; SKIN-GRAFTING); and a xenotransplant, if from an animal.

The pioneering success was achieved with transplantation of kidneys in the 1960s. In 2014 in the UK, 4431 organ transplants and 3575 corneal transplants were undertaken. Nearly 3000 of these were kidney-only transplants, including 139 in children and about 1 in 3 from a living donor. The current 5 year survival rate for a transplanted kidney is 80–90% and the ten year survival 70–85%. Other organs that have been transplanted with increasing success are the heart, lungs, liver, bone marrow, intestines, pancreas and the cornea of the eye. Nearly 900 liver (or liver lobe) transplants are conducted each year in the UK, along with about 200 heart transplants and lung transplants, and 175 of the pancreas (usually together with a kidney). The major outstanding problems are that patients still die while on waiting lists to receive a donation because of donor shortages; and that, once a successful operation has been performed, the recipient's body must be prevented from rejecting and destroying the transplanted organ. Such rejection is part of the normal protective mechanism of the body (see IMMUNITY). Good progress has been made in techniques of tissue-typing and immunosuppression to overcome the problem. Drugs are now available that can suppress the immune reactions of the recipient, which are responsible for the rejection of the transplanted organ. Notable among these are CICLOSPORIN A, which revolutionised the success rate, tacrolimus, a macrolide immunosuppressant and anti-lymphocytic serum (ALS), which reduces the activity of the lymphocytes (see LYMPHOCYTE) – cells which play an important part in maintaining the integrity of the body against foreign bodies.

The reasons for lack of donors are complex but include the reluctance of the public and doctors to consider organ donation; poor organisation for recovery of donor kidneys; and worries about the diagnosis of death. Patients who may become suitable donors after death are those who have suffered severe and irreversible brain damage – since such patients will be dependent upon artificial ventilation. Patients with malignant disease or systemic infection, and patients with renal disease, including chronic hypertension, are unsuitable.

In the UK, if a patient carries a signed donor card or has otherwise recorded his or her wishes, there is no legal requirement to establish lack of objection on the part of close relatives – although it is good practice to take account of their views. If a relative objects, despite the known request by the patient, staff will need to judge, according to the circumstances of the case, whether it is wise to proceed with organ removal. If a patient who has died is not known to have requested that his or her organs be removed for transplantation after death, the designated person may only authorise the removal if, having made such reasonable enquiry as may be practical, he or she has no reason to believe (a) that the deceased had expressed an objection to his or her body being so dealt with after death, or (b) that the surviving spouse or any surviving relative of the deceased objects to the body being so dealt with. The staff of hospitals and organ exchange organisations must respect the wishes of the donor, the recipient and their families with respect to anonymity.

It is considered ethical (see ETHICS) to maintain artificial ventilation and heartbeat until removal of organs has been completed. This is essential in the case of heart and liver transplants, and many doctors think it is desirable when removing kidneys. Official criteria have been issued in Britain to recognise when BRAIN-STEM DEATH has occurred. This is an important protection for patients and relatives when someone with a terminal condition – usually as a result of an accident – is considered as a possible organ donor. See also www.uktransplant.org.uk.