TRANSPLANTS AND ORGAN DONATION

TRANSPLANTS AND ORGAN DONATION. Transplantation (grafting) is the replacement of a failing organ or tissue by a functioning one. Transplantation was a dream in antiquity. The Hindu deity Ganesha had his head replaced by an elephant's head soon after birth (Rig-Veda, 1500 b.c.). In the Christian tradition Saints Cosmas and Damian (fl. 3rd century a.d.) are famous for replacing the diseased leg of a true believer with the leg of a dark-skinned Moor, thereby becoming the patron saints of physicians and surgeons.

Transplantation may be from the same person (autologous), from the same species (homologous—the allograft can come from a genetically identical twin, genetically close parent or sibling, living unrelated person, or cadaver) or from a different species (xenotransplant).

Human tissues carry highly specific antigens, which cause the immune system to react to "foreign" materials. An antigen is a substance that when introduced into an organism evokes the production of substances—antibodies—that destroy or neutralize the antigen. Grafts of a person's own tissue (such as skin grafts) are therefore well tolerated. Homologous grafts are plagued by attempted rejection by the recipient human. The biological acceptability of the graft is measured by tissue typing of the donor and recipient using the human leucocyte antigen, or HLA, panels. The closer the match between the donor and the recipient, the greater the chance of graft acceptance and function. Xenotransplantation is as yet entirely experimental because of tissue rejection and the possibility of transmitting animal diseases to the human recipient.

Organ transplantation has two sets of problems. The first relate to the recipient: the magnitude of the procedure and the intricacies of the surgical technique, the avoidance of rejection (acute or chronic) of the grafted tissue because of antigens in the tissue, and temporary and long-term suppression of the recipient's immune processes, with resulting infections and cancers. The second set of problems relates to the graft itself: the source of the graft and its collection, preservation, and transport to the recipient. Associated problems are ethical and economic, including the expense of the procedure and the cost of long-term monitoring and support of the patient.

Many of the technical problems associated with transplantation are gradually being overcome, and solutions are being constantly improved. Obtaining donor organs and distributing them equitably remain critical problems.

Transplantation is well established for skin, teeth, bone, blood, bone marrow, cornea, heart, kidney, liver, and to a lesser extent for the lung, pancreas, and intestines. On occasion two transplants are combined, such as heart and lungor pancreas and kidney.

Grafting an individual's own skin was well known to the ancient Hindus and has been widely used in the Western world since the middle of the nineteenth century. Skin grafting is a major resource in treating large wounds and burns. Artificially grown skin analogues and frozen pigskin can temporarily meet massive immediate needs.

Blood transfusion was attempted in the seventeenth century in France and England but was abandoned because of adverse reactions, including death. The identification of blood types in the early twentieth century and the discovery of methods of separating and preserving blood and its components have made transfusion a common and effective therapy. An important side effect of World War II and later conflicts has been improvement in all aspects of blood transfusion—collection, preservation, and delivery. The recognition of HLA types was based largely on the practices of blood transfusion and skin grafting. Transplantation of bone marrow and stem cells (precursors from which blood cells develop) is used to treat patients with malignancies of the blood and lymphatic system, such as the leukemia and lymphoma. Donor cells may be from the patient or from antigenmatched donor(s). Usually the patient's bone marrow (with the stem cells) is totally destroyed by chemotherapy, sometimes with whole body irradiation afterward. Donor cells are then introduced into the body, with the expectation that they will take over the production of new blood cells.

The commonest organ transplanted is the kidney. The first successful kidney transplant was done in 1954 in the United States between identical twins; before immunosuppressive procedures were developed, twins were the most successful donors. Transplantation between twins evokes the least immune reactions as the HLA types of twins are identical or nearly so. In 2001, about 14,000 kidney transplants were performed in the United States, 63 percent using kidneys obtained from cadavers. Patient survival using cadaveric donor kidneys is more than 90 percent at 1 year after surgery, and 60 to 90 percent at 5 years. For living donor kidneys, survival is above 98 percent at 1 year and 71 to 98 percent at 5 years. Corneal transplants have a high rate of success because the cornea does not have blood vessels and hence is not highly antigenic. Cadaver corneas can be successfully preserved and stored in eye banks for delivery as needed. More than 30,000 corneas are grafted each year in the United States.

More than 5,000 liver transplantations were done in the United States in 2001. Some of these transplants were portions of livers from living donors. In living adult liver donors, significant surgical complications and even a few deaths have raised some questions about the procedure. Though this is a controversial procedure, the great demand for donor livers will certainly keep this practice going. The heart is the fourth most common organ replaced. The first heart transplantation was done in South Africa in 1967; the high risk made it very controversial at the time. In 2000, almost 2,200 heart transplants were performed in the United States. Graft rejection remains a problem, and immunosuppresion (with its attendant dangers) has to be continued lifelong. If patients do not have other significant diseases, they return to near-normal functioning. More than 80 percent of patients function satisfactorily 1 year after surgery, and 60 to 70 percent at 5 years. At any given time, thousands of patients are waiting for donated organs. With progressive technical improvement in keeping seriously ill patients alive and making transplantation less risky, the need for organs continues to rise. Bioengineering is the application of engineering principles to biology—this includes the artificial production of cells and organs, or that of equipment that can perform functions of organs such as the kidneys or the heart. Bioengineered cells and tissues are a promising field in transplantation. Bioengineered skin is widely used for short-term coverage. Bioengineered corneas appear to be promising. Primitive heart-muscle cells (myoblasts) are being transplanted into diseased hearts, chondrocytes or cartilage cells are being cultured for use in degenerated joints, and there is considerable interest in xenografts.

Since 1968 a Uniform Anatomical Gift Act allows adults to donate their organs for transplantation after death. In every state, some form of donor card is associated with driver's licenses, and health care providers in most states are required to ask permission for postmortem organ procurement. (In some European countries consent for organ donation is presumed.) The United Network for Organ Sharing (UNOS) was established in 1977 to coordinate the distribution of kidneys and later other organs nationally and to maintain a registry of persons awaiting transplant. The UNOS generally prefers that donated organ(s) be used in the local community. All transplant centers are required to join the network and abide by its rules. By May 2002, UNOS membership included 255 Transplant Centers, 156 Histocompatibility Laboratories, and 59 Operating Organ Procurement Organizations. With all these efforts, the shortage of organs persists.

BIBLIOGRAPHY

Cooper, David K. C., and Robert P. Lanza. Xeno: The Promise of Transplanting Animal Organs into Humans. Oxford and New York: Oxford University Press, 2000.

Fox, Renée C., and Judith P. Swazey, with the assistance of Judith C. Watkins. Spare Parts: Organ Replacement in American Society. New York: Oxford University Press, 1992.

Lock, Margaret M. Twice Dead: Organ Transplants and the Reinvention of Death. Berkeley: University of California Press, 2002.

Munson, Ronald. Raising the Dead: Organ Transplants, Ethics, and Society. Oxford and New York: Oxford University Press, 2002.

Murray, Joseph E. Surgery of the Soul: Reflections on a Curious Career. Canton, Mass.: Science History Publications, 2001.

Parr, Elizabeth, and Janet Mize. Coping With an Organ Transplant: A Practical Guide to Understanding, Preparing For, and Living With an Organ Transplant. New York: Avery, 2001.

United States Congress, House Committee on Commerce. Organ and Bone Marrow Transplant Program Reauthorization Act of 1995: Report (to Accompany S. 1324). Washington, D.C.: U.S. General Printing Office, 1996.

United States Congress, House Committee on Commerce, Subcommittee on Health and the Environment. Organ Procurement and Transplantation Network Amendments of 1999: Report Together with Dissenting Views (to Accompany H.R. 2418). Washington, D.C.: U.S. General Printing Office, 1999.

United States Congress, House Committee on Government Reform and Oversight, Subcommittee on Human Resources. Oversight of the National Organ Procurement and Transplantation Network: Hearing Before the Subcommittee on Human Resources of the Committee on Government Reform and Oversight. 105th Cong., 2nd sess., 8 April 1998. Washington, D.C.: General Printing Office, 1998.

Youngner, Stuart J., Renée C. Fox, and Laurence J. O'Connell, eds. Organ Transplantation: Meanings and Realities. Madison: University of Wisconsin Press, 1996.

Internet Sources
For current national statistical data, see the Web sites of the Scientific Registry of Transplant Recipients, http://ustransplant.org/annual.html, and the United Network for Organ Sharing, http://www.unos.org/frame_default.asp.

For general information for patients, updated regularly, see http://www.nlm.nih.gov/medlineplus.

Ranes C. Chakravorty

See also Medicine and Surgery .