History of Transplant Immunobiology (Part 1 of 2).
Rene J Duquesnoy, Ph.D.,
Professor of Pathology and Surgery,
University of Pittsburgh Medical Center
During the past quarter-century, transplant immunobiology has
established itself as a scientific discipline to study the mechanisms
by which a recipient rejects or accepts a transplant from a genetically
different donor. In the early history of transplantation, five
separate disciplines of investigators approached the problem of
graft rejection. They are the surgeons, the tumor specialists,
the Mendelian geneticists, the biologists and finally the immunologists.
Each had their own agenda and a lack in communication prevented
the recognition and application of conceptional advances in the
other disciplines. Nevertheless, most laws of transplant immunity
had already been defined during the first two decades of the twentieth
century. During the late 1960s, largely because of the work of
Sir Peter Medawar, transplant immunobiology became established
as a multidisciplinary science. This historical overview deals
with progress made in the different disciplines before that time.
Part 1 summarizes events before World War II and Part 2 deals
with milestones from the 1940s through the 1960s. Much of the
information have been extracted from seven historical reviews
by noted investigators who offer additional perspectives. These
references are listed at the end of this article.
The Transplant Surgeons
For several milennia, the replacement of diseased or injured organs with healthy ones has stimulated the imagination of humankind. In the mythological world, chimeric gods and heros have been transplanted with heads and other organs mostly from different species (these are examples of xenotransplants). In the early biblical times the prophet Ezekiel refers to cardiac transplantation:
"A new heart also I will give you, and a new spirit will be put within you; and I will take away the stony heart out of your flesh, and I will give you a heart of flesh".
The New Testament mentions transplant cases like Jesus of Nazareth restoring a high priest servant's ear cut off by Simon Peter's sword. Later on Saint Peter replanted the breasts of Saint Agatha pulled off during torture and Saint Mark replaced an a soldier's hand amputated during battle. These are examples of autotransplants.
In the fifth century BC, the legendary Chinese physician Pien Ch'iao exchanged the hearts between a man with a strong spirit but a weak will and a many with the opposite personality to cure the unbalanced equilibrium of the two men's energies.
A famous example of a cadaveric allograft is described in Jacopo da Varagine's Leggenda Aura in 348 CE. In the "miracle of the black leg", the twin brothers Saints Cosmas and Damian succesfully replaced the gangrenous leg of the Roman deacon Justinian with a leg from a recently buried Ethiopian Moor.
While it seems unlikely, that proper surgical techniques were available to perform these transplants, the practice of skin grafting has been known for many centuries. During the second century BC, the Indian surgeon Sushruta pioneered the skin grafting procedure for rhinoplasty, i.e. plastic surgery whereby the patient's own skin is used to do reconstruction of the nose. In those days, the cutting noses was a common practice to punish criminal offenders and of course, we should not discount the fights with knives and swords.
During the Renaissance, the Gaspare Tagliacozzi, a famous surgeon and anatomist from Bologna, Italy, used a flap from the upper arm to do reconstructive surgery on a person who had lost his nose. While autografts were generally successful, virtually all allografts failed. The practice of donation consent did not exist, since slaves were used as skin donors, and often they suffered serious (infectious) complications. Such cases of the "sympathetic nose" were criticized by Voltaire and other writers. In his play Hudibras , Samuel Butler states
"When the date of Nock was out, off dropt the sympathetic Snout".
Taglicozzi was well aware of the limitations of the allograft procedure. In 1596, in his treatise "De Curtorum Chirurgia per Insitionem", he concluded that
"The singular character of the individual entirely dissuades us from attempting this work on another person. For such is the force and power of individuality, that if any one should believe that he could achieve even the least part of the operation, we consider him plainly superstitious and badly grounded in physical science".
He seemed to have recognized the concept that individual differences were responsible for these allograft failures. Almost nothing was known about genetics until Mendel did his pioneering studies 250 years later.
Other early transplant-related activities dealt with the grafting of teeth; this was done on humans already in the 17th century. Around 1800, the renowned English surgeon John Hunter, reported successful transplants of human teeth into the highly vascularized comb of a cock (a xenograft). He also grafted a cock's spur into its comb and also a cock testes into a hen ("without altering the disposition of the hen"). Hunter concluded that
"Transplantation is founded on a disposition in all living substances to unite when brought into contact with each other".
This view seems compatible with the modern concept about the relation between microchimerism and allograft acceptance.
In 1804, G. Baronio in Milan, reported successful skin transplants between sheep and other animals of the same and from different species. Other investigators were much less successful with such allografts and xenografts. In Paris, Paul Bert, a pupil of Claude Bernard, described in his 1863 thesis "De la Greffe Animale", many kinds of allogeneic and xenogeneic skin transplants. He could not duplicate Baronio's results. In parabiosis experiments, Bert established a cross circulation between rats by using belladonna injections ("la greffe siamoise")
The techniques of Reverdin (1869) and Thiers (1874) for covering granulating surfaces with small pieces of epidermis lead to therapeutically acceptable skin grafting procedures. There were no indications of long-term graft survival. Successful allogeneic skin transplants have been reported. One case involves Sir Winston Churchill, who during the Sudanese war in 1898, was asked to donate a piece of skin for an injured fellow officer. The doctor, a 'great raw-boned' Irishman, spoke to Churchill:
"Oi'll have to take it of you, Ye've heeard of a man being flayed aloive?
Well this is it what it feels loike."
(This is quite a unique approach for obtaining informed donor consent!).
And Churchill wrote:
" A piece of skin and some flesh about the size of a shilling from the inside of my arm. This precious fragment was grafted to my friend's wound. It remains there to this day and did him lasting good in many ways. I for my part keep the scar as a souvenir."
Evidently, an example of a long-term success of a skin allograft!
Corneal transplant procedures were developed during the 19th century. In 1837, the Irishman Samuel Bigger performed a successful transplant of a full-thickness cornea into the blind eye of a pet gazelle. Continuing improvement in the grafting procedure and increasing success rates in experimental animals led to the first successful human corneal transplant in 1906. Corneal transplantation became a standard procedure in ophthalmology practice, its success was in marked contrast to the high failure rate of skin grafts.
Because of the advances in suturing techniques towards the end of the 19th century, surgeons began to transplant organs, especially kidneys between dogs. Several reports claimed success and long-term graft survival. In Lyon, the French surgeon Jaboulay tested pig and goat kidney transplants in humans. Alexis Carrell perfected the vascular anastomosis technique and this led to all kinds of experimental transplants including the grafting of a dog's head onto the neck of another dog. All these allogeneic and xenogeneic transplants were invariably unsuccessful as was the first human cadaveric kidney transplant performed in 1933 by the Ukranian surgeon Voronoy.
Although nobody understood the reasons for the high failure rate, the contention was that the major problems had been solved and that little work remained to perfect transplantation. C.C. Guthrie, who worked with Carrell, noted that
"...The outlook is by no means hopeless and the principles of immunity, which yield such brilliant results in many other fields, would seem to be worthy of being tested in this case".
Indeed, the field of immunology had undergone a dramatic expansion during the past few decades as illustrated by the following examples:
It should be noted that most immunological concepts in those days pertained to humoral immunity and nothing was known about cellular immunity and lymphocyte function.
During the first quarter of the 20th century, a relatively few
number of studies were reported on the immune basis of skin graft
failures. Underwood (1914) suggested that an "anaphylactic
hypersensitivity" was responsible for allograft rejection.
With repeat skin transplants on children, Holman (1924) reported
that a "second set" of transplants from the same donor
"did not take but disappeared simultaneously with the first
group of isografts". Davis (1917) and Shawan (1919) suggested
that blood groups might play a determining role in allograft success
The Tumor Specialists
Most of the information about the immune basis of allogeneic transplant failures would come from the studies of the tumor specialists. Stimulated by the rapid advances in vaccination against microbial agents, the tumor researchers attempted similar approaches for the treatment of cancer. However, preventive immunization or serum therapy of naturally occurring tumors was generally unsuccessful. This led to the development of transplantable tumor lines in experimental animals. In 1912, Georg Schöne's book: "Heteroplastische und Homoplastische Transplantation" summarized the experimental work reported in about 500 publications during the first decade. He coined the term: "Transplantationsimmunität" and formulated the following rules:
As Silverstein points out in his 1989 book "A History of Immunology", the "laws of transplantation" were substantially defined already in 1912. On the other hand, Leslie Brent concludes in his recent book "A History of Transplantation Immunology" that this credit to Schöne is not wholly justified. A subsequent review published in 1916 by Tyzzer on "Tumor Immunity" confirmed Schöne's findings . Tyzzer further pointed out that
In 1929, Woglom's book "Immunity to Transplantable Tumors" represents a review of 600 reports published since Schöne's book. His additional conclusions include
While considerable evidence had accumulated for an immune basis of tumor allograft rejection, only humoral mechanisms were considered. However, serum antibodies were never effective in controlling in vivo tumor growth. In those days, the concept of cellular (i.e. lymphocyte-mediated) immunity was not recognized although Da Fano (1910) reported that rejecting tumor allografts contained large numbers of lymphocytes rather than polymorphonuclear leukocytes. These findings are similar to those of Tyzzer who also noted that the lymphoid response was infiltrative and proliferative.
Murphy and Rous (1912) described the histological predominance of lymphocytes in fowl sarcoma rejection model. Injection of sarcoma cells in chicken (as well as duck and pigeon) embryos resulted in uninhibited growth during the early days of gestation. Thereafter, the tumors were rejected and this coincided with the appearance of lymphocytes. Tumor rejection occured also after transfer of adult lymphocytes into the embryo. These data indicated for the first time a relation between the ontogeny of the immune response and transplant rejection. Further studies by Murphy have shown that lymphopenia inhibits tumor rejection and that X-irradiation causes lymphopenia and depresses antibody formation. Unfortunately, the functional role of the lymphocyte remained a mystery until the late 1950s.
It should be noted that other investigators did not ascribe to
the immune basis of tumor allograft rejection. In his 1930 Book
"Transplantation and Individuality", the prominent
biologist Leo Loeb recognized the genetic basis of individual
differences and transplantation incompatibility. Rather than considering
immune mechanisms, he argued that rejection resulted because the
graft could not make the connections necessary to the survival
in the new environment of the recipient. His concepts were based
on Ehrlich's "athrepsia" theory which considers nutritional
needs of tissues and cells
The Mendelian Geneticists
In 1903, the Danish geneticist Jensen first demonstrated with a breeding stock of albino mice that genetic differences control rejection of transplantable tumors. Loeb (1908) and Tyzzer (1909) reported similar findings with inbred "Japanese waltzing mice". Clarence C Little (1916) used inbred mouse strains by brother-sister mating and concluded in 1924 that
"...The genetics of tissue transplantation is likely to become in the not distant future of far greater importance".
In 1929 he founded the Jackson Memorial Laboratory at Bar Harbor, Maine and George D Snell was hired in 1935. As the editor of the book "The Biology of the Laboratory Mouse" , Snell was inspired by Little's chapter "The Genetics of Tumor Transplantation" to pursue a research carreer in mouse genetics which lead him to the discovery of the H (or histocompatibility ) locus that controls tumor graft rejection.
During the late thirties, the Englishman Peter A Gorer performed serological studies with sera from rabbits immunized with mouse red blood cells which led to the discovery of antigen II expressed by certain mouse strains. Grafting of albino mouse sarcoma cells induced the development of anti-antigen II antibodies by the tumor-resistant Auguti and Black mice. All tumor-susceptible cross-bred mice expressed antigen II and specific antibodies killed tumor cells in vitro. In 1946, Gorer visited Snell and H and II were combined as H-2, " a Major Histocompatibility Gene" and nine alleles were identified. These investigators developed a highly productive research collaboration which established the major strains of inbred laboratory mice and more than twenty so-called congenic-resistant mouse lines that differ only at H-2, most of them are still being used in immunology research.
Progress in Transplantation Immunology during the Nineteen-Thirties
The nineteen-thirties was a period of decline of transplantation immunology-related research. The surgeons concluded that, except for corneal grafting, all attempts at skin and organ transplants will fail due to rejection. Immunosuppression by X-irradiation turned out not to be practical, and the immunity hypothesis of rejection was largely discarded. The tumor researchers had lost faith in the approach of treating cancer via vaccination or transplantation. The geneticists shifted their interest towards "pure" genetics by breeding inbred strains of mice and by studying gene polymorphisms.
And then came World War II (article to be continued in part 2).