Istoricul transplantului de ţesuturi şi organe

Transplantul de organ (sinonim cu grefa de organ) înseamnă înlocuirea totală sau parţială a unui organ sau ţesut bolnav cu un organ sau ţesut sănătos, sau cu părţi ale acestuia, provenind de la un donator. Organul sau ţesutul prelevat pentru transplant (numit şi grefon) poate proveni de la donatori vii sau de la donatori decedaţi. Beneficiarul unui transplant este numit primitor.

ClasificareExistă mai multe tipuri de transplant, clasificate după originea grefonului

Homotransplant (allograft)Numit şi homogrefă, homotransplantul este un transplant efectuat între membrii ai aceleiaşi specii. Este cel mai frecvent tip de transplant folosit în practică. În majoritatea cazurilor sistemul imunitar al primitorului percepe organul transplantat ca pe un corp străin. De aceea, pentru a evita fenomenul imunologic de respingere a transplantului, primitorul trebuie să urmeze toată viaţa tratament imunosupresor. Sunt şi cazuri care nu impun tratament imunosupresor, cum ar fi transplantul de cornee.

Isograft (singenic)

Un caz particular de homotransplant îl constutuie transplantul între organisme genetic identice (între gemeni identici-monozigoti), care se comportă asemănător autotransplantului, din punct de vedere imunologic.

Heterotransplant (xenograft)Numit şi heterogrefă, heterotransplantul este un transplant efectuat între organisme aparţinând unor specii diferite. Fenomenul de respingere de transplant este mult mai puternic în cazul heterogrefelor. Unele heterotransplanturi sunt utilizate curent în medicina umană (de exemplu transplantul de valve cardiace de porc, la om). Multe heterotransplanturi se realizează experimental între diferite specii, în vederea studierii unei posibile aplicabilităţi la om (un exemplu în acest sens este transplantul experimental de ţesut insular pancreatic de la peşti la primate non-umane).

Autotransplant (autograft)Autotransplantul, numit şi autogrefă, este acel tip de transplant în care primitorului i se transplantează ţesuturi proprii, prelevate din altă parte a corpului. Această metodă are aplicabilitate numai în cazul transplantului de ţesuturi sau celule. Grefoanele se prelevează din zone regenerabile sau zone cu exces de ţesut. Sunt şi situaţii în care se prelevează ţesuturi non-indispensabile din unele zone, pentru a fi transplantate în zone unde sunt imperios necesare (în unele proceduri de by-pass arterial realizat din grefon venos).

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Dupa situsul de implantare, transplantul poate fi descris ca ortotopic sau heterotopic.

Transplantul ortotopic se refera la implantarea tesutului donor intr-o pozitie anatomic corecta la nivelul primitorului; transplantul heterotopic se refera la implantarea graftului intr-o zona diferita fata de cea normal anatomica

Preistorie

Cele mai vechi dovezi de autograft ortotopic au fost pastrate din epoca bronzului. O portiune circulara de os a fost detasata de calvarie pentru a diminua presiunea intracraniana şi mai târziu repozitionata ca autograft. Scrieri vechi din Egipt, China, India descriu incercari de transplantare. In Egiptul antic se practica deja transplantul de tesut epitelial. In aghiologia crestina se vorbeste despre faptul ca sfintii doctori fara de arginti, Cosma si Damian, in sec. al IV-lea au efectuat transplantul de gamba unui suferind, prelevand gamba de la un om mort de patru zile. Medicina a facut progrese enorme, dar multa vreme nu s-a preocupat de posibilitatea si fiabilitatea transplantului.

Un text indian de la 700 BC descrie o procedură de reconstrucţie nazala, care este foarte asemănătoare unor metode moderne.

Zorii transplantului modern

Transplant de organ a evoluat dupa dezvoltarea anesteziei şi antisepticelor chirurgicale. În 1540, un alchimist, Valerius Cordus, a sintetizat eterul si a observat efectele sale pe animale. Utilizarea de eter in chirurgie şi stomatologie a devenit foarte răspândită în secolul 19. Joseph Lister a pus bazele pionieratului in domeniul chirurgiei aseptice bazată pe descoperirile bacteriologice al lui Louis Pasteur.Alexis Carrel este cunoscut drept fondatorul transplantului de organ din cauza muncii de pionierat in tehnicile de chirurgie vasculara. Activitatea lui Carrel şi Charles Guthrie descrise în “Transplantul de organe si vene” a servit drept fundament pentru chirurgia vasculară şi a transplantul de organ. Un sistem de perfuzare pentru organe creat de Carrel şi Charles Lindbergh a dus la dezvoltarea bypassului cardiopulmonar de catre John Gibbon, ceea ce a deschis calea chirurgiei cardiace. Frank Mann a studiat transplantul renal si de inima, la Clinica Mayo în anii 1930. Primele transplanturi de organe la om au început cu allogrefa renala în 1936, si nu au reuşit până la descoperirea imunogeneticii şi pana la punerea în aplicare a drogurilor imunosupresoare.

Evoluţia donarii de organe şi a achiziţiei de organe

În anii 1960, transplantarea organelor de la donatorii cadavru parea să fie imposibilă. Donatori vii au fost unica sursa de organe pentru transplant. In

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Massachusetts General Hospital, a fost recoltat un ficat de la un ofiţer de poliţie a cărui inimă era functionala, dar cu leziuni cerebrale grave prin impuscare. Acest eveniment a dus la dezvoltarea conceptului de moarte cerebrala ca moarte, mai degrabă decât cel de încetare a circulaţiei, care era definita anterior ca moarte. Conceptul de moarte cerebrală a crescut foarte mult numărul de organe disponibile pentru donare şi a îmbunătăţit prezervarea si recoltarea organelor. După ce conceptul de moarte cerebrala a fost stabilit, s-a infiintat si dezvoltat un sistem de procurare a organelor pentru a asigura calitatea şi disponibilitatea acestora cât mai eficient posibil.

In 1954 s-a realizat primul transplant fiabil de rinichi, iar in 1967 primul transplant de inima. Ulterior, performantele au continuat, actualmente realizandu-se transplantul de: rinichi, ficat, pancreas, inima, plaman, inima-plaman (din 1981). Actualmente se vorbeste de posibilitatea transplantului de parti ale creierului si chiar de transplant de cap. In ceea ce priveste tipurile de transplant, actualmente se efectueaza transplanturi de tesuturi: sange, vene, oase lungi, valve cardiace, cornee, maduva osoasa, piele; transplant de celule izolate, transplant de organe regenerabile (ficatul) si neregenerabile duble (rinichii), unice (inima, plaman, intestin subtire, pancreas).

Posibilitatea teoretica a fiabilitatii heterotransplantului ridica multe probleme, dintre care putem aminti cateva:

- riscul esecului datorat reactiei de respingere pe care o va avea organismul uman cand organul de animal va intra in contact cu sangele uman. In asemenea situatii, se stabileste imediat o reactie antigen-anticorp cu activarea complementului si distrugerea endoteliului vascular. In ciuda incercarilor de a bloca aceasta reactie a organismului primitor, rezultatele nu sunt concludente si nici validate.

Istoria transplantului de organe si tesuturi in RomaniaPrimele incercari de transplant de organe in Romania dateaza inca de la inceputul secolului XX si se datoreaza doctorului Florescu care, lucrand in cadrul laboratorului de chirurgie experimentala al Facultatii de Medicina din Bucuresti a efectuat mai multe transplante experimentale de rinichi. Operatiile nu au fost incununate de succes, iar Dr. Florescu a considerat ca aceasta se datoreaza unui unghi de implantare deficitar al vaselor sanguine (rinichii deveneau pana la urma necrotici), motiv pentru care a incercat diferite locuri din organism pentru transplant in speranta ca va gasi unghiul potrivit. Acest lucru nu s-a intamplat, desigur, si experimentele au fost abandonate.

In 1958 Prof. Dr. Agrippa Ionescu realizeaza primul transplant de piele intr-un cadru spitalicesc organizat, iar in 1962 este efectuat primul transplant de cornee. In a doua jumatate a secolului trecut, Sergiu Duca la Cluj-Napoca si Vladimir

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Fluture la Timisoara si Dumitru Popescu-Falticeni impreuna cu Emil Papahagi la Spritalul de Urgenta Floreasca Bucuresti, efectueaza transplant experimental de ficat.

Primul transplant reusit al unui organ solid din Romania la om a fost cel efectuat de Profesorul Eugeniu Proca, in februarie 1980 la Spitalul Fundeni, cu rinichi de la donator in viata (mama receptorului). Acest transplant a fost urmat la scurt timp de un transplant renal de la donator decedat, efectuat la Timisoara de o echipa condusa de Prof. Dr. Petru Dragan. Pana in decembrie 1989 se efectueaza doar transplanturi de rinichi si acestea intr-un numar relativ redus.

In anul 1992 se pun bazele primului program modern de transplant renal din Romania, de catre Prof. Dr. Mihai Lucan, la Clinica de Urologie a Spitalului Judetean Cluj-Napoca (devenita ulterior Institutul Clinic de Urologie si Transplant Renal Cluj-Napoca).

Incepand din 1995 se intensifica eforturile de organizare a unei retele nationale de transplant, desfasurate in mai multe etape :

stabilirea protocolului de diagnostic si declarare a mortii cerebrale (Prof. Dr. Dan Tulbure)

stabilirea conditiilor de prelevare a organelor de la donatorul decedat din punct de vedere medico-legal (Prof. Dr. Vladimir Belis)

campanie in mass-media de explicare a mortii cerebrale si de promovare a donarii de organe

efectuarea primelor prelevari multiorgane (1997); in februarie a fost prelevat un rinichi de la o donatoare aflata in moarte cerebrala in Clinica de Chirurgie Generala a Spitalului Fundeni (echipa chirurgicala Irinel Popescu, Ioanel Sinescu, Vladislav Brasoveanu, Radu Soare, anestezist Dan Tulbure), iar in iunie o prelevare de ficat si rinichi la Spitalul de Urgenta Floreasca (echipa chirurgicala a fost coordonata de Prof. Dr. Irinel Popescu, iar echipa anestezica de Dr. Ioana Grintescu). Un rol important a revenit ulterior Spitalului Judetean Targu-Mures, unde Prof. Dr. Radu Deac si Dr. Pia Moldovan au reusit sa mentina in conditii fiziologice mai multi donatori in moarte cerebrala, iar familiile acestora au fost de acord cu donarea

incepe formarea coordonatorilor de transplant, primul dintre acestia fiind Dr. Victor Zota, actualul Director al Agentiei Nationale de Transplant. Se stabilesc regulile repartitiei organelor la nivel national si al schimburilor de organe cu alte tari europene cu care se semneaza acorduri de cooperare

in 1997 ia fiinta asociatia profesionala "ROMTRANSPLANT" care va juca un rol important, atat pe plan stiintific, cat si pe plan organizatoric, in dezvoltarea transplantului romanesc. Cele 5 congrese nationale, cu participare internationala, ale acestei asociatii (1998 :

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Cluj-Napoca - presedinte Prof. Dr. Mihai Lucan; 2000 : Bucuresti - presedinte Prof. Dr. Irinel Popescu; 2002 : Targu-Mures - presedinte Prof. Dr. Radu Deac; 2004 : Constanta-Eforie Nord - presedinte Prof. Dr. Vasile Sarbu si 2006 : Cluj-Napoca - presedinte Prof. Dr. Mihai Lucan) au reprezentat momente de referinta din toate punctele de vedere

In aprilie 2000 este efectuat primul transplant hepatic cu supravietuirea bolnavului de catre Prof. Dr. Irinel Popescu la Spitalul Fundeni, iar in octombrie 2000, primul transplant de ficat de la donator in viata, de catre aceeasi echipa (transplant de la mama la fiica).In anul 2001 Prof. Dr. Margit Serban efectueaza in centrul universitar Timisoara primul transplant medular, urmata, la scurt timp, de echipa Spitalului Fundeni (Prof. Dr. Dan Colita, Prof. Dr. Constantin Arion).In 2003 echipa de la Spitalul Judetean Constanta (Prof. Dr. Vasile Sarbu, Dr. Simona Dima) efectueaza primul autotransplant de insule pancreatice, in 2004 la Institutul de Urologie si Transplant Cluj-Napoca Prof. Dr. Mihai Lucan efectueaza primul transplant combinat de rinichi si pancreas, iar in 2005 la Institutul Clinic Fundeni (Prof. Dr. Irinel Popescu, Dr. Simona Dima) se efectueaza primul allotransplant de insule pancreatice la un bolnav cu ciroza si diabet, caruia i s-a efectuat un transplant combinat de ficat si insule pancreatice. Transplantul de celule stem a fost efectuat pentru prima data in anul 2004 pentru o afectiune a miocardului (Prof. Dr. Stefan Dragulescu, Prof. Dr. Virgil Paunescu - la Institutul de Cardiologie din Timisoara), si in anul 2005 pentru o afectiune a ficatului (Prof. Dr. Irinel Popescu, Dr. Simona Dima - la Institutul Clinic Fundeni). In tot acest timp, atat legislatia, cat si cadrul organizatoric au cunoscut imbunatatiri permanente.In anul 1998 a fost introdusa prima lege moderna a transplantului din Romania - Legea nr. 2/1998 "privind prelevarea si transplantul de tesuturi si organe umane" in care erau specificate toate conditiile de prelevare si transplantare a organelor si tesuturilor. Aceasta a fost inlocuita in prezent de Titlul VI "Efectuarea prelevarii si transplantului de organe, tesuturi si celule de origine umane in scop terapeutic" din Legea 95/2006 "privind reforma in domeniul sanatatii" in care apare, in plus, un capitol detaliat asupra transplantului de celule si tesuturi, iar reglementarile privind transplantul de organe sunt aduse la zi. Alinierea la legislatia europeana este si rezultatul prezentei unui reprezentant al Romaniei (Prof. Dr. Irinel Popescu) in Comisia de transplant de organe si tesuturi a Consiliului Europei.In anul 2004 apare Legea nr. 588, de infiintare a Agentiei Nationale de Transplant, iar Dr. Victor Zota este numit Director Executiv al Agentiei, care este instalata in actualul sediu si incadrata cu o schema de personal. Prof. Dr. Irinel Popescu devine presedinte al Consiliului Stiintific al Agentiei.

Ca rezultat al activitatii de transplant, in prezent in Romania s-au efectuat peste 1000 de transplante renale (in centrele universitare Bucuresti, Cluj-Napoca,

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Timisoara, Iasi, Constanta si Oradea), peste 100 de transplante hepatice in Institutul Clinic Fundeni, peste 50 de transplanturi medulare, peste 30 de transplante cardiace, etc.

Early history of transplantation immunology

The predominant early theory regarding the mechanism of rejection was malnutrition of grafted tissue as suggested by Paul Ehrlich in 1906. Similarly, in 1910, Carrel noted that physiological disturbances in transplanted organs were likely caused by biological factors. Soon thereafter, Viennese pathologist Karl Landsteiner discovered the ABO blood group system that eventually led to the introduction of clinical blood transfusion. Sir Peter Medawar, who was awarded the Nobel Prize for his pioneering work, defined for the first time the immunologic nature of skin allograft rejection in humans. He confirmed that these reactions are immunologic based on data from extensive animal experimentation. In addition, George Snell observed that tumor grafts of normal tissues were accepted between inbred animals but not between animals of different strains.

As early as 1914, the fact that lymphocytes infiltrated grafts was recognized; however, many years elapsed before an understanding of the molecular basis of T-lymphocyte activation as a cause of acute rejection was developed. Over the years, researchers recognized that the principal targets of the immune response are the major histocompatability complex (MHC) molecules on the graft. The T lymphocytes of the recipient recognize the MHC by 2 different pathways. The direct pathway initiates CD8+ cytotoxic T cells by interaction of human leukocyte antigen (HLA); the indirect pathway activates CD4+ helper T cells and leads to a delayed-type hypersensitivity response, cell-mediated toxicity, and alloantibody production.

Advances in transplantation immunology

The genes responsible for immunologic reactions leading to graft rejection were termed histocompatibility genes. Peter Gorer further established that the major histocompatibility locus was antigene II, and thus named the locus histocompatibility II. Further work in the area of immunohematology by Jean Dausset led to the knowledge that MHC genes are the most important markers of an individual's biological identity. Dausset noted that MHC genes are required for the presentation of peptide antigens to T-cell receptors, and they play a vital role in transplantation immunology. Ralph Zinkernagel and Peter Doherty added to the growing pool of immunological knowledge and stated that the role of the MHC is to "signal changes in self to the immune system."

Research on humans led to the discovery that genetic control of the HLA resides on chromosome 6 in a supergene region known as the MHC. Class I MHC

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antigens include HLA-A, HLA-B, and HLA-C. Furthermore, the class II MHC antigens important in transplantation are governed by HLA-DR, HLA-DP, and HLA-DQ. These regions on chromosome 6 are tightly linked and constitute a haplotype.

Manipulating the immune system

Knowledge of immunology led to the first successful kidney transplantation between identical twins, in 1954. The initial work in this field began with the recognition that organ allografts may be transplantable. Peter Medawar performed skin grafts for victims of burns during World War II. However, the grafts only succeeded when performed between identical twins.

At Peter Bent Brigham Hospital in Boston, the possibility of treating end-stage renal disease by kidney grafting was under active investigation. In 1952, David Hume made early attempts at allografting the kidney from an unrelated donor and found that the kidney graft functioned well for a short period. One of their grafts survived several months, and Hume reasoned that chronic uremia likely suppressed the immune function of the recipient.

Joseph E. Murray performed the first successful identical twin renal transplantation at Peter Bent Brigham Hospital in Boston. In 1959, this team performed the first successful fraternal twin transplantation. Despite massive irradiation of the host prior to transplantation, these attempts were largely unsuccessful. Nonetheless, their efforts set the stage for the evaluation of rejection and mechanisms to avoid it.

Over the next 25-year period, discoveries in immunosuppression paved the way for attempts at manipulating the recipient's immune system. These research efforts eventually led to the discovery of lymphocyte function, the role of the thymus in the ontogeny of the immune system (1961), the delineation of the human MHC (1963), the distinction of the T- and B-lymphocyte subsets (1968), and the demonstration of the MHC-restricted nature of the adaptive immune response (1974).

Early efforts at immunosuppression

Initial attempts at controlling rejection began with experiments involving total body irradiation. The initial evidence came in 1958 from Paris, France, where Mathe, a hematologist, treated 6 Yugoslavians who were accidentally irradiated on a previous occasion. The bone marrow homografts in these patients were successful, which led the way for irradiation to be used in other organ transplantation. Unfortunately, for renal transplantation, irradiation alone led to dismal outcomes, with only 2 reported successes: a single case by Merrill in 1960 and another by Hamburger in 1962.

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Further efforts to avoid and control rejection of transplanted organs led to the investigations of medications. Robert Schwartz and William Dameshek showed that the drug 6-mercaptopurine could prevent rabbits from producing antibodies to foreign proteins. In 1961, Joseph Murray prescribed 6-mercaptopurine for the first time to a human kidney transplant recipient. The patient unfortunately died from drug toxicity. Roy Calne at the Peter Bent Brigham Hospital experimented with 6-mercaptopurine and its close relative azathioprine, after he had disappointing experience with total body irradiation.

Azathioprine used alone was not very effective in human transplantation. Careful studies undertaken by Thomas E. Starzl in the early 1960s, while he was in Denver, demonstrated that a combination of corticosteroids and azathioprine led to much better success. The work of Thomas Starzl transformed clinical transplantation into a clinical service and ushered in the proliferation of transplantation programs in kidney transplantation worldwide. Cortisone had been discovered in 1936, as an adrenal gland steroid with immunosuppressive properties. Prednisone, a cortisone derivative, was used subsequently in cadaveric kidney transplant recipients. In 1964, David Hume noted that prednisone not only was useful in preventing graft failure in regular doses, but it was useful for reversing renal allograft rejection in larger doses. However, continued use of corticosteroids permanently alters normal immune function and produces other very serious adverse effects.

Discovery of cyclosporine

In 1972, Swiss biochemist Jean-François Borel discovered cyclosporine in natural fungal byproducts. Cyclosporine improved graft rejection in animals by inhibiting T-lymphocyte activity. Roy Calne investigated the effects of cyclosporin in dogs with renal allografts and pigs with orthotopic heart grafts. His work proved that cyclosporine was a much better immunosuppressive agent than corticosteroids, azathioprine, or a combination of both. Calne also found that cyclosporine was nephrotoxic; work by other investigators on devising safe protocols for cyclosporine led to marked improvement not only in kidney transplantation, but also in successful transplantation of the lungs, heart, heart and lungs, pancreas, and liver.

In the late 1970s, cyclosporine increased the 1-year survival rate of liver allografts from 18% to 68%. Although cyclosporine is generally associated with significant adverse effects, administration of small doses in a controlled protocol results in minimal adverse events.

Cocktail approach

The cocktail approach, which combines cyclosporine with steroids and azathioprine, was found to be the most effective approach to immunosuppression for organ transplantation patients over the next 10-15 years. More recently, this combination has been replaced by regimens that include

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newer immunosuppressive agents. Tacrolimus has almost completely replaced cyclosporine in liver and pancreas transplantation, and it is used in 50% or more of kidney recipients around the world. Mycophenolate mofetil has largely replaced azathioprine in most organ transplantation procedures. Additional new immunosuppressive agents that have been approved include sirolimus, daclizumab, basiliximab, and antithymocyte globulin (Thymoglobulin). Furthermore, a number of new regimens are being explored that attempt steroid withdrawal or avoidance, or calcineurin inhibitor withdrawal or avoidance.

Heart And Heart-lung Transplantation

Early experimentation

In 1905, Carrel and Guthrie performed the first cardiac transplantation in animals at the University of Chicago. This was a heterotopic experimental transplantation. Parts of a small dog were transplanted into the neck of a larger dog by anastomosing the cut ends of the jugular vein and carotid artery to the aorta, the pulmonary artery, one of the vena cavae, and the pulmonary vein. In 1933, Mann transplanted a canine heart into the carotid-jugular circulation with establishment of coronary perfusion. The longest survival was 8 days, and he observed evidence of allograft rejection as the heart was infiltrated with lymphocytes, mononuclear cells, and polymorphonuclear cells. The work of Marcus and colleagues at Chicago Medical School contributed to donor graft preservation and improved coronary perfusion techniques.

Pioneering work by Demikhov

Vladimir Demikhov's research greatly advanced the field of experimental cardiac transplantation. His published works documented many experiments, including transplantation of the head, transplantation of halves of the body, and surgical combination of 2 animals with the creation of single circulation. His initial work in cardiac transplantation involved canine heterotopic cardiac transplants to the inguinal region. His monograph reported a long series of 250 experimental efforts at transplanting a heterotopic intrathoracic cardiac graft.

On June 30, 1946, Demikhov transplanted a heterotopic heart and lung; the animal survived for 9 hours and 26 minutes. A subsequent experiment on a dog resulted in 25 days of survival, and the cause of death was probably dehiscence of the tracheobronchial suture line.

Graft preservation

Experiments in orthotopic transplantation began with Demikhov, who attempted to maintain donor and recipient perfusion during anastomosis. Problems associated with maintaining the recipient during transfer and preserving the graft were addressed by Neptune and colleagues. Neptune's team transplanted the entire heart-lung block and maintained both the donor and recipient in a cooler

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to maintain hypothermia. Webb and Howard demonstrated that canine hearts that were heparinized and flushed in potassium citrate could survive prolonged periods at low temperature. When transplanted heterotopically, the function of these organs returned. Webb and Howard also performed successful orthotopic heart-lung transplantations in which the recipient was maintained with cardiopulmonary bypass during transfer.

Advances in surgical techniques

In 1958, Goldberg and colleagues at the University of Maryland performed orthotopic cardiac transplantations using an innovative technique in which the left auricle was anastomosed with the left atrium. This circumvented the problems associated with anastomoses of individual pulmonary veins. This technique was further refined by Cass and Brock, who used right and left atrial cuffs.

In 1960, Richard Lower and Norman Shumway described the modern surgical technique of orthotopic cardiac transplantation. The recipient was kept alive on cardiopulmonary bypass; the donor heart was immersed in cold saline; and anastomoses were performed to the atria, pulmonary artery, and aorta. The dogs that underwent transplantation survived and resumed their regular activity; this generated an immense interest in cardiac transplantation and further experimental work by other investigators, including D.A. Blumenstock, who in 1963 reported that 50 of his dogs survived for periods ranging from 1-42 days. Deaths in these dogs occurred secondary to acute rejection. Subsequent investigators used immunosuppression and improved long-term survival; the immunosuppressive drugs used included steroids, cyclosporine, and azathioprine.

Human heart transplantation

By the mid 1960s, surgical techniques, methods of recipient support, and methods of myocardial protection had been described. In addition, transplant allograft rejection had been reported, and methods of diagnosing and treating rejection were available. Legal and logistic issues were the next hurdles that prevented heart transplantation in humans. On December 3, 1967, the first successful human cardiac transplantation was performed by Christiaan Barnard at Groote Schuur Hospital in Cape Town, South Africa. The transplant recipient was a 54-year-old man with end-stage ischemic heart disease; the donor was a young man with a severe brain injury. The recipient initially recovered but subsequently died of Pseudomonas pneumonia 18 days later.

In 1967, Barnard described the operation: "The achievement did not come as a surprise to the medical world. Steady progress towards this goal has been made by immunologists, biochemists, surgeons, and specialists in other branches of medical science all over the world during the past decade to ensure that this, the ultimate in cardiac surgery, would be a success."

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On December 6, 1967, Adrian Kantrowitz performed a transplantation from an anencephalic infant to an 18-month-old child using deep hypothermia and circulatory arrest. Although the surgery went well, postoperatively, the recipient developed metabolic and respiratory acidosis, leading to cardiac arrest, and survived only 6.5 hours. The autopsy showed diffuse atelectasis of both lungs.

After multiple attempts at cardiac transplantation in the late 1960s, poor outcomes were achieved and interest in this procedure waned. However, during the 1970s, an organized approach to cardiac transplantation (mostly by the group at Stanford University) improved the 1-year survival rate from 22% in 1968 to 65% in 1978. This success occurred because of improved management of infectious complications, better donor and recipient selection, and improved capabilities of diagnosing and aggressively treating rejection. The widespread adoption of cyclosporine use in the 1980s resulted in increased worldwide enthusiasm for cardiac transplantation and much-improved long-term survival.

Human heart-lung transplantation

Denton Cooley performed the first clinical heart-lung transplantation on September 15, 1968. The team replaced the heart and lungs of a 2-month-old infant who had an atrioventricular canal defect with the heart and lungs of an anencephalic infant donor; the recipient survived only 14 hours, succumbing to respiratory failure. In 1982, Bruce A. Reitz published the first successful clinical series of heart-lung transplantations; the use of cyclosporine and the Stanford University's group experience with experimental cardiopulmonary transplantation were important contributing factors.

Lung Transplantation

Early experiments

Experiments in lung transplantation were underway during the 1940s, long before human heart transplantation became a reality. In May of 1947, Demikhov performed the first canine transplantation of the lungs alone. In November, 1947, Demikhov reported a successful transplantation of the lower lobe in a dog, which survived 7 days. Juvenelle performed early experiments in autografting and reimplantation. Neptune and colleagues began to use the atrial cuff method for anastomosis. With proper atrial cuff anastomosis, pulmonary hypertension, which was observed in earlier experimentation as part of the reimplantation response, could be avoided.

Advances in bronchial anastomosis

Bronchial dehiscence plagued Demikhov's experiments in 1947. Haglin developed a method for reestablishing the bronchial circulation by vascular anastomosis. The Toronto Lung Transplant Group used a technique of omentopexy to reinforce the bronchial anastomosis. Subsequently, telescoping

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the bronchial anastomosis to a depth of one cartilaginous ring was shown to be equally effective, and thus omentopexy became unnecessary.

Additional advances occurred in the area of lung preservation; these methods were crucial for successful transplantation. Initial techniques included hypothermia and flush perfusion of the pulmonary vasculature in the unventilated lung. The positive index inspiratory pressure during the procurement procedure increases interalveolar surfactant, which minimizes pulmonary complications in the graft. Insufflating the lung with 100% oxygen during procurement coupled with the administration of prostacyclin into the pulmonary circulation has resulted in acceptable graft function after 6-8 hours of ischemic time.

Further advances

Lung allografts in mongrel dogs and inbred beagles were performed by Metras in Marseilles, France, and Blumenstock in Cooperstown, NY. Thomas and Blumenstock experimented with immunosuppressive regimens to combat lung transplant rejection. A 300-day survival in a lung allograft recipient was achieved with the help of immunosuppressive agents. Another hurdle that needed to be overcome concerned the healing of tracheal and bronchial anastomoses. The Toronto Lung Transplant Group demonstrated that better immunosuppression with cyclosporine led to improved healing of the bronchial anastomosis.

Human lung transplantation

James D. Hardy and his team performed the first single-lung transplantation in a human at the University of Mississippi Medical Center on June 11, 1963. A 58-year-old man with unresectable left lung cancer and obstructive pneumonitis was the recipient. The donor was a patient who died from a massive myocardial infarction. The lung transplant recipient received immunosuppression with azathioprine and irradiation. Unfortunately, the patient died on the eighth postoperative day because of progressive renal failure despite peritoneal dialysis. However, at autopsy, the vascular and bronchial anastomoses were intact and evidence of rejection in the transplanted lung was absent.

Fritz Derom of the University of Ghent in Belgium transplanted a lung in the 1960s into a recipient who had end-stage respiratory failure due to silicosis. The patient improved significantly and lived for 10.5 months after the operation. This group of investigators from Ghent was the first to successfully treat and reverse episodes of rejection and acquired infectious complications in the recipient.

The growth of lung transplantation was slow due to unclear eligibility criteria for lung transplant recipients, and, despite clear improvement in function after transplantation, survival benefits were less clear. In fact, at least one study

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showed patients with end-stage lung disease survived longer than transplant recipients. By 1978, 38 human lung transplantations had been performed. Bronchial disruption and the inability to differentiate infection from rejection appeared to be the major problems. Improved healing of the bronchial anastomosis was found after the introduction of cyclosporine, and this may have been due in part to the lower routine doses of corticosteroids.

Unilateral and bilateral sequential lung transplantation

Lessons were learned from en bloc heart-lung transplantation, in which single distal tracheal anastomosis and maintenance of collateral circulation to the airway achieved much better anastomotic healing. Limiting the length of the donor bronchus and extrinsic revascularization by wrapping the anastomosis with omentum led to advancements in anastomotic techniques. This culminated in a successful single-lung transplantation, a procedure pioneered by the Toronto Lung Transplant Group under the leadership of Joel Cooper and Griffith Pearson.

Subsequently, lung transplantation was performed by G.J Magovern and A.J Yates at the University of Pittsburgh; this patient survived only a short time. In 1983, the Toronto Lung Transplant Group consisting of Cooper, Pearson, and Patterson accomplished long-term survival following a successful single-lung transplantation.

Isolated single-lung transplantation was performed for patients with end-stage chronic obstructive pulmonary disease and advanced pulmonary fibrosis. This technique was later expanded to bilateral sequential single-lung transplantation (ie, isolated double-lung transplantation) for patients with bronchiectasis and cystic fibrosis. Over time, bilateral sequential single-lung transplantation became the procedure of choice because en bloc double-lung transplantation was a procedure of considerable technical complexity. More recently, use of living donors for lobar allografts has been demonstrated to be a useful alternative for selected patients who require isolated lung transplantation.

Long-term survival of lung transplant recipients

One-year survival rates for lung and heart-lung transplantations worldwide remain lower (70% and 62%, respectively) compared with heart transplantations (83%). The 5-year survival rates are 70% for heart and 45-50% for lung transplantations. Long-term patient survival rates are dismal for all thoracic grafts: 22.3% at 18 years for heart, 20% at 9 years for lung, and 25% at 12 years for heart-lung recipients. The most significant factors responsible for immediate mortality are related to either the patient's medical condition (patient in intensive care unit prior to transplantation and/or requires mechanical ventilation) or the underlying diagnosis. The factors responsible for late mortality continue to be infection and the presence of chronic rejection manifested pathologically as bronchiolitis obliterans syndrome.

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Bronchiolitis obliterans syndrome occurs in at least 40% of patients by 2 years and is the cause of death in 50% of those affected. The focus has now shifted to the treatment of chronic rejection and bronchiolitis obliterans syndrome as opposed to technical proficiency. Enhanced induction and maintenance immunosuppression along with aggressive treatment of acute rejections may delay the incidence of bronchiolitis obliterans syndrome and improve graft survival.

Kidney Transplantation

Renal transplantation is the present-day, state-of-the-art therapy for patients with end-stage renal disease. The history of successful renal transplantation parallels the advancement of transplantation immunobiology. Experiments in the early 1900s and continued advances in surgery, nephrology, and immunology helped accomplish this feat.

Early experiments

Experimental intra-abdominal renal grafts were being performed in animals in the 1930s and 1940s. Autografts generally survived, although homografts were rejected. On December 25, 1952, Hamburger performed the world's first renal transplantation in a 15-year-old roofer who injured his solitary kidney. The donor of the graft was the patient's mother. The graft functioned immediately following surgery, but it unfortunately ceased to function on the 22nd postoperative day. The patient died 10 days later due to the unavailability of hemodialysis. However, this event had a considerable impact on the scientific community. Surgical inspection of the graft revealed that immunological rejection, rather than stenosis or thrombosis of the renal artery, led to graft failure.

Successful kidney transplantation

Joseph Murray and Hartwell Harrison performed the first transplantation of a kidney graft between identical twins on December 23, 1954. This success was followed by subsequent attempts by Murray and Merrill that led to 7 successful transplantations between identical twins in Boston. Most of the recipients of identical twin kidney grafts performed by Joseph Murray did well; some still have functioning kidneys more than 30 years after transplantation. However, the attempts at cadaveric renal transplantation universally resulted in graft failure due to rejection.

The first attempts to control the immune system used total body irradiation. In 1958, a Boston-area woman who was accidentally irradiated with 6 Gy received a functional renal graft, although the patient died from bone marrow aplasia. In 1959, Hamburger and Merrill irradiated 2 transplant recipients with a total dose of 4.5-4.8 Gy; the donors were nonidentical twins. Both of these recipients had successful outcomes. The patients survived 20 and 26 years, respectively. In

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June 1960, Kuss and colleagues were faced with rejection in a kidney transplant recipient who received the graft from an unselected donor. The use of 6-mercaptopurine in this patient, an immunosuppressive agent previously studied in animals, reversed the rejection process and ushered in the era of medications for the prevention and treatment of rejection. In 1964, Crosnier performed another cadaveric transplantation with long-term successful function.

In the early 1960s, the pioneering work of Thomas Starzl led to further advancements. His contributions were systematic studies using azathioprine and prednisone therapy to prolong graft survival. Following the demonstration of antilymphocyte serum efficacy by Waksman, Starzl conducted the first clinical trial of antilymphocyte globulin as an adjunct to azathioprine and prednisone in human kidney transplantation.

Long-term graft survival

At present, the 1-year patient survival rate for living donors is 98%, and the 1-year patient survival rate for cadaveric transplants is 95%. The graft half-life for living donors is approximately 20 years, and the graft half-life for cadaveric donors is 12 years.

The outcome data from the United Network for Organ Sharing annual report of 2002 shows that the 1-year survival rate for grafts from living donors ranges from 88.1-95% and the rate for cadaveric grafts increased from 79.7% to 87.1%. Furthermore, the half-life for grafts from living donors increased steadily from 12.7 to 21.6 years, and that for cadaveric grafts increased from 7.9 to 13.8 years. These short-term improvements are the possible result of cyclosporine; its effect on the long-term survival of kidney transplants is not known. Kidney graft failure occurs because of chronic rejection, graft dysfunction, and nephrotoxicity, causing the patient to need dialysis and often a new organ. The development of new therapeutic approaches to prevent chronic rejection is needed to prolong the long-term survival of kidney transplants.

Liver And Pancreas Transplantation

Liver transplantation

Early history of liver transplantation

The history of liver transplantation began with experimentation by Stuart Welch in Albany, NY, in 1955. Welch described the experimental transplantation of an auxiliary liver to the right paravertebral gutter in mongrel dogs. Experiments at the University of Miami from 1956-1958 led the way to orthotopic liver transplantation. In 1958, orthotopic liver transplantations following hepatectomy were performed, although these attempts were marred by poor performance of the transplanted liver. The operative procedures were further refined by Jack Cannon at the University of California at Los Angeles in 1956 and by several

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investigators in Boston and Chicago from 1958-1960. These animals did not survive for more than 4 days due to a lack of effective immunosuppression; however, technical principles such as optimal portal revascularization, allograft preservation, and other techniques were perfected.

Human liver transplantation

Thomas Starzl attempted human liver transplantation in 1963, at the University of Colorado. Despite years of research into organ preservation, surgical technique, and understanding the physiological interrelationship of the liver with other intra-abdominal viscera, this did not prepare his team for the unexpected difficulties encountered in patients with end-stage liver disease and extensive portal hypertension. The first patient did not survive surgery, and 2 others died 7.5 and 22 days postoperatively. Subsequent similar failures in Boston and Paris led to a worldwide moratorium on liver transplantation.

Initial attempts were unsuccessful because of a combination of technical difficulties and the unavailability of effective means to prevent rejection. As increased experience was achieved and with improvements in immunosuppression, prolonged liver recipient survivals were achieved. From 1963 to 1979, 170 patients underwent liver transplantation at the University of Colorado; 56 survived for 1 year, 25 for 13-22 years, and several remain alive with follow-ups of 17-31 years. In 1968, Roy Calne of Cambridge University founded the second liver transplantation program. As with renal grafts, the long-term survival rate after liver transplantation remained poor (18-30% one-year patient survival) until the advent of cyclosporine.

Pancreas transplantation

Experiments in pancreas transplantation began long before the discovery of insulin. In 1891, pieces of dog pancreas autotransplanted beneath the skin prevented diabetes after removal of the intra-abdominal pancreas. Subsequent experimentation with intrasplenic transplantation did not succeed because of graft necrosis. In 1916, sliced human pancreas was transplanted into 2 patients, but the grafts were completely absorbed. The first pancreatic xenotransplantation was performed in 1893 in London; a 15-year-old boy underwent subcutaneous implantation of a pancreas.

Despite extensive animal experimentation, pancreatic transplantation did not become a reality until 1966 when W.D. Kelly performed the first human, whole-organ pancreatic transplantation for treatment of type 1 diabetes mellitus. Because of poor outcomes, few procedures were performed until 1978. Much of the early work was performed by Sutherland and colleagues at the University of Minnesota. With improved immunosuppressive regimens and newer surgical techniques, the 1980s ushered in a new era in pancreas transplantation. According to the International Pancreas Transplant Registry, nearly 10,000 pancreatic transplantations were recorded by 1998.

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Most of the pancreatic transplantations have been performed in patients with type 1 diabetes mellitus and a lack of insulin production. The most common indication is renal failure; therefore, the pancreas transplantation is typically performed simultaneously with a kidney transplantation. In some patients with hypoglycemic unawareness or other diabetic complications, isolated pancreas transplantation has been performed. However, the results have been somewhat inferior to those of the combined procedure.

Various technical concerns must be considered in patients undergoing pancreas transplantation, including whether or not the venous drainage should be into the systemic circulation or into the portal vein. Another controversial topic is whether the exocrine secretions should be drained enterically or into the bladder as initially described. The complications of graft pancreatitis and bladder leakage that plagued early experiences with pancreas transplantation have largely been resolved as a result of both better technical expertise and fewer rejection- and immunosuppression-related complications.

Cell Transplantation

Bone marrow transplantation

Early history

The history of bone marrow transplantation (BMT) dates back to 1939 when Osgood unsuccessfully infused a few milliliters of marrow into patients with aplastic anemia. In 1949, Jacobson discovered that shielding the spleen protected mice from lethal irradiation. Lorenz performed allogenic BMT in animals protected by total irradiation. His findings, and research by Barnes and colleagues, demonstrated that a cellular rather than a humoral factor played a role in graft survival. Vanbekkum, DeVries, and other scientists performed important experiments to study immunological reactions in transplantation recipients. They demonstrated that successfully grafted allogeneic marrow cells could later produce an immunological reaction against host tissues; this phenomenon is now known as graft versus host disease (GVHD).

Experimental canine studies during the 1960s resulted in important discoveries that were applicable to human transplantation. Total body irradiation did not seem to prevent GVHD; mismatched canine leukocyte antigen always resulted in graft rejection or GVHD. Methotrexate was also found to be an immunosuppressive agent that could prevent or ameliorate the graft versus host reaction.

Human bone marrow transplantation

Although initial attempts at allogeneic BMT in the 1950s and 1960s were unsuccessful, renewed attempts occurred after additional knowledge of the HLA system was obtained. Getty performed a successful allogeneic marrow graft in a

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patient with severe combined immunologic deficiency using a sibling donor with identical HLA. Two similar successes were reported around the same time. These patients did not require immunosuppressive therapy and survived for more than 25 years. In the 1970s and 1980s, clinical BMT required matched HLA haplotypes between the donor and recipient. Although earlier BMT procedures occurred between siblings, current molecular techniques have enabled the precise characterization of MHC genes and have allowed the possibility of matching unrelated individuals.

Stem cell transplantation

In the 1970s, researchers performed a large number of BMT procedures using HLA-matched sibling donors for patients with end-stage leukemia or aplastic anemia. These endeavors resulted in mixed success because BMT was only considered for patients with advanced leukemia after conventional therapy failed. In the 1980s and 1990s, researchers noted that BMT performed at first remission or after first relapse resulted in significantly prolonged survival. BMT procedures for treating other disorders, such as thalassemia major and sickle cell disease, were also successful when the procedure was performed at an earlier stage.

Because stem cells have been shown to be present in peripheral blood, these cells have now been used for autologous grafting. In 1989, Gluckman successfully transplanted cord-blood stem cells, which are immature and less likely to cause GVHD. Extensive studies reviewed by Korngold and Brent have established the role of both T cells and histocompatibility systems in the GVHD reaction. Even with HLA-matched sibling donors, GVHD occurs half of all patients. Although corticosteroids and methotrexate partially ameliorated GVHD in early studies, cyclosporine in combination with other drugs have proven superior in subsequent studies.

Present status of bone marrow and stem cell transplantation

Following major efforts to determine the effectiveness of autologous BMT in the 1970s and 1980s, autologous BMT has become the therapy of choice for patients with malignant lymphoma and for selected patients with acute myelocytic leukemia and other malignancies. Recent research has also shown that a large number of stem cells from peripheral blood could be harvested following cytotoxic chemotherapy and specifically after growth factor administration. Following high-dose chemotherapy, peripheral blood stem cell therapy results in more rapid recovery of platelets than BMT. In the future, stem cell transplantation may allow many patients to attain a state of minimal residual disease so that other treatments, such as chemotherapy maintenance, monoclonal antibodies, vaccines, nonspecific immune modulators, and dendritic cell infusions, may be performed.

Pancreatic islet cell transplantation

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Experiments in 1964 and 1965 proved that islet cells could be isolated by digestion of a whole pancreas and remain viable. Ballinger and Pelacy reported the first experimental islet cell transplantation in 1970. Approximately 500 isolated islet cells were transplanted intraperitoneally in diabetic rats, with subsequent long-term amelioration of diabetes. Following these findings, Kemp described a newer method of implantation, by intraportal injection and embolization of islet cells into the liver. This technique improved control of diabetes much more quickly than intraperitoneal transplantation.

Islet cell transplantations in humans are usually allografts, which have higher rates of failure and require lifelong immunosuppression. C. Ricordi has performed much of the previous work on islet cell transplantation. The causes of islet cell graft failure include failure of the initial engraftment, insufficient islet cell mass, rejection, and islet injury caused by immunosuppressive agents. Islet cell autograft transplantation in patients with chronic painful pancreatitis does not require immunosuppression, and patients have better success rates. Because current immunosuppressive drugs affect islet function, the development of more effective and less toxic immunosuppressive drugs may improve the success rate of islet cell transplantation.

Edmonton protocol

James Shapiro and his team at the University of Alberta in Edmonton, Canada, began a series of islet transplantations in March, 1999, which has revolutionized the field and helped achieve remarkable success rates. The Edmonton protocol consists of percutaneous intraportal injection of blood type–matched islet cells under local anesthesia in the radiology department of a hospital. Once the islet cells embolize into the liver, they develop a blood supply and begin producing insulin. Most of the recipients of this therapy required 2 procedures performed over an average of 29 days in order to produce enough insulin to avoid exogenous insulin administration for maintenance of euglycemia. In the first published series of 7 consecutive patients with type 1 diabetes undergoing islet cell transplantation under this protocol, insulin independence was achieved in 80% of those monitored for 2 years. Much of the success of this protocol is attributed to the novel glucocorticoid-free immunosuppression regimenused.

In the past 5 years, more than 500 patients with type 1 diabetes mellitus received islet transplants at over 50 institutions worldwide. However, islet function inevitably decays over time. The benefits of islet transplantation are improved control of glycosylated hemoglobin and reduced risk of recurrent hypoglycemia. Further work is needed to develop successful living donor islet transplantation, single donor protocols, improved engraftment, islet proliferation in vitro and in the recipient, alternative islet sources, and new immunosuppressive drugs.

Xenotransplantation

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Allograft transplantation has become the therapy of choice for end-stage organ failure in the 21st century. However, because of the lack of donor organs, the use of biomechanical and nonhuman organs is being explored as a potential solution to this shortage. Xenotransplantation is defined as the transplantation of tissue from a donor of one species to a recipient of a different species.

Early history of xenotransplantation

Xenotransplantation was actually performed long before clinical allotransplantation. In 1905, French surgeon Princeteau transplanted a slice of rabbit kidney into a uremic child. Despite noted improvement of renal function, the child died of pneumonia. Although many other examples of xenografts of different organs have been reported from this early period, human xenografts were quickly abandoned because they uniformly failed.

More recently, in 1960, Reemtsma performed a kidney transplantation from a chimpanzee donor into a human recipient; aggressive immunosuppression led to a 9-month survival. In 1984, Bailey performed an orthotopic transplantation of a baboon heart into a human neonate with a hypoplastic left ventricle; the graft functioned for 20 days. Despite aggressive immunosuppression, graft failure occurred secondary to vascular rejection. A baboon-to-human liver transplantation was performed by Starzl in 1993. This graft functioned well for a time, although the patient died several months later from severe sepsis and organ rejection. Other xenotransplant efforts include transplantation of dopaminergic porcine fetal neural cells to the basal ganglia in order to treat Parkinson disease. Deacon et al performed one such transplantation in 1997.

Several obstacles to xenotransplantation have been uncovered through these human and other animal experiments, including the presence of alpha 1,3-galactose (alpha Gal) antibodies on the surface of animal cells, which are not present on human cells and are attacked by natural antibodies within normal human circulation. Along with the immunological barriers found, the animal organs may produce signals and proteins that are similar but not identical to humans, which can affect their function.

The future of xenotransplantation

The future of clinical xenotransplantation appears to be progressing in 2 directions. Cellular xenografts, such as pancreatic islet cell transplantation and neural cell transplantation, may be protected from rejection because of the absence of vascular tissues. In addition, the consequences of rejection may not be overly severe. In contrast, xenotransplantation may, in the future, be used as a lifesaving procedure for critically ill patients who are waiting for allografts but are dying because of the shortage of organs. This technique may be particularly helpful for patients with acute liver failure or cardiac failure.

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The answers may come with the creation of transgenic animals to overcome the immunologic barriers, and, eventually society may see the introduction of elective xenotransplantation as an alternative to allotransplantation. Many researchers hope that successful xenotransplantation procedures will eventually overcome the ever-increasing donor deficit and provide immense benefit to the large number of patients who require transplantation and currently have little hope of receiving a cadaveric allograft.

Keywords

autograft, isograft, syngeneic graft, allograft, homograft, xenograft, heterograft, heart transplantation, lung transplantation, kidney transplantation, bone marrow transplantation, BMT, liver transplantation, OLT, xenotransplantation, immunosuppression, total body irradiation, graft vs host disease, graft versus host disease, graft-versus-host disease, GVHD, graft rejection, major histocompatability complex, MHC, human leukocyte antigen, HLA, transplant, xenotransplant, organ donation, organ donor, UNOS, United Network for Organ Sharing, organ transplantation, orthotropic transplantation, heterotropic transplantation, pancreatic transplant, pancreas transplant, pancreatic transplantation, pancreas transplantation, National Transplant Act

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