TRANSPLANTATION OF WHOLE HUMAN ORGANS

Personally, I am deeply honored to follow Professor Billingham on this program. It would take all my prescribed time to recount the debts owed by clinicians to Professor Billingham, to his senior collaborator Sir Peter Medawar, and to other members of the historically important research group that was assembled in England during the decade or more beginning in 1940. Most of what we know about the pathogenesis of graft rejection came from this team. In addition, the first reports of a really potent modern immunosuppressive agent, namely cortisone, came from Billingham. Krohn, and Medawar as early as 1951. Some of the first demonstrations of the induction of tolerance to homografts came from Billingham and Brent in their famous neonatal innoculation experiments in which, incidentally, they clearly defined for the first time many features of the graft-versus-host syndrome.

However, it is not my objective today to recapitulate these and other milestone achivements in the experimental laboratory.¹ Instead I have been assigned to talk about clinical organ transplantation. Perhaps the distinction of clinical versus laboratory experimentation is a reasonable one since a very definite and important body of knowledge has been contributed to basic biology by clinicians who have thereby elevated their efforts to a different plane from that of simple patient care.

THE MODEL OE RENAL TRANSPLANTATION

Much information has come from the accurate observation of patients subjected to the relatively simple operation of renal homotransplantation. With this procedure, the kidney is removed from the donor, usually transferred across to the opposite side of the recipient, and revascularized by anastomosing the renal vessels to appropriate vessels in the recipient's pelvis (fig. 1). Urinary drainage is customarily provided by anastomosing the homograft ureter to the bladder of the recipient patient (fig. 1).

Fig 1.

The operation of renal homotransplantation. The donor left kidney has been removed and transferred to the right iliac fossa of the recipient. See text for description. (By permission of Jour. Amer. Med. Assn. 187 (1964) : p. 734.)

I will say no more about the surgical technique of renal homotransplantation. Most of the rest of my remarks will be nonoperative and can be illustrated with figure 2. This twenty three-year old patient whose early course is illustrated was given a renal homograft by his younger brother in early 1963. For more than a year before the operation he had suffered with progressive renal disease. This was manifested by an abnormally low volume of daily urine excretion with consequent weight gain, and by a decrease almost to zero of the creatinine clearance measurement which is one of the most accurate ways of assessing kidney function. With kidney failure and the reduced capacity to remove waste products from the body, there is an increase in a number of undesirable metabolities of which the blood urea nitrogen (BUN) is most commonly measured as an index of renal function. In the months preceding transplantation this patient's BUN had increased markedly. He had been kept alive by intermittent treatments with the artificial kidney.

Fig. 2.

Classic rejection crisis in a patient being treated with Imuran^R. Deterioration of renal function began more than two weeks after transplantation. The rejection episode was treated by the addition of prednisone to the therapeutic program. Subsequent to reversal of rejection, the prednisone dose was rapidly reduced. Acti-C—Actinomycin C, one of the main immunosuppressive drugs: LN—Left nephrectomy at time of transplantation; RN—Right nephrectomy. Imuran^R is the trade name for azathioprine (By permission of Surg. Gynec. Obstet. 117 (1963) : p. 385).

After transplantation, the drug azathioprine (Imuran^R) was given in an attempt to prevent rejection. There was prompt and excellent function of the new kidney (fig. 2). Large volumes of urine were excreted. The creatinine clearance rose to normal (in fact to supernormal) levels, the BUN fell, and the patient felt better than he had at any time in the several preceding years. However, the initial untroubled convalescence was short-lived. After a little more than two postoperative weeks the new kidney began to fail (fig. 2). The creatinine clearance dropped sharply, the BUN rose secondarily, the urine volume diminished and the patient began to gain weight. In addition, there was an increase in the white cells in the patient's blood. He developed high blood pressure which required control by antihypertensive medications, became acutely febrile with temperatures of almost 40° C. and began to excrete protein into his urine (fig. 2). In short, all the manifestations of acute rejection had developed in spite of immunosuppressive therapy, namely signs of acute homograft failure plus an acute systemic febrile illness.

THE REVERSAL OF REJECTION AND “GRAFT ACCEPTANCE”

Before experience with this patient and others of the same era in the early 1960's. it had been assumed that rejection was one of biology's most vigorous and persevering reactions and that, once begun, it would continue to the death of the transplant. It was now proved that this assumption was false and that rejection was a highly reversible process. In the case depicted in figure 2, immunosuppressive treatment was intensified by the addition of one of the adrenal cortical steroid drugs known as prednisone, a potent analogue of the cortisone with which Professor Billingham had worked twelve years earlier. The findings of rejection disappeared almost as if by magic (fig. 2). The BUN fell, the creatinine clearance rose, and protein that had appeared in the urine disappeared as did the high blood pressure. The fever was gone within a few hours of the institution of the prednisone therapy. Rejection had thus been shown to be a reversible process. This was a fundamental disclosure by clinicians and one which had not been at all anticipated by previous workers in basic research laboratories.

The second equally important thing learned from these early cases can also be demonstrated by the case summarized in figure 2. In the weeks after rejection had been reversed in this patient, the prednisone dose was very rapidly reduced, and eventually it was discontinued altogether after only about five months (fig. 3). Then the azathioprine dose was also lowered until within a year the patient was receiving only about half the daily quantity that at the outset had failed to prevent the onset of a moderately severe rejection.

Fig. 3.

The long-term course of the patient whose early convalescence is depicted in figure 2. Note that prednisone was discontinued after five months and that the dose of azathioprine was eventually cut approximately in half. In spite of these adjustments, the patient has never had another episode rejection. He is in perfect health almost eight years after operation.

It is quite possible that all immunosuppressive therapy could be stopped in the patient I just described, who is still alive with perfect renal function after almost eight years. Although we have never felt justified in taking the final drastic step of stopping treatment in any human recipient, we have tested the hypothesis in dogs such as that shown in figure 4. The animal had his own liver removed and replaced with the liver of a non-related mongrel donor in March, 1964. He was treated with azathioprine for four postoperative months. The drug was then discontinued and no therapy has been provided since. The animal remains alive two-thirds of a canine lifetime later.

Fig. 4.

On March 23, 1964, this dog's own liver was removed and replaced with the liver of a non-related mongrel donor. The animal was treated with azathioprine for 4 months and all therapy then stopped. He remains in perfect health 6 2/3 years after transplantation.

I will summarize the two concepts that I hope I have clearly stated. First, rejection is a highly reversible process. Second, a favorable change often occurs after transplantation by virtue of which the host comes to tolerate better the presence of the homograft, thereby allowing immunosuppression to be reduced. If either of these statements were not true, organ transplantation would not be feasible. The fact that they are true is the inside story of clinical transplantation.

THE MECHANISM OE GRAFT ACCEPTANCE

Although it has been accepted that rejection is a reversible process and that a homograft may come to be more or less tolerated by its new host, the explanation for the eventual privileged state of the transplant is by no means clear. It is probable that more than one immunologic pathway is involved.

Tolerance

A classical possibility is that the continuous presence of a transplanted organ in a host being treated with immunosuppressive therapy leads to a selective loss of responsiveness to the antigens of the homograft. The technical term for this would be “tolerance.” That antigen stimulation plus immunosuppression can lead to a state of narrow-range tolerance has not been seriously questioned since Schwartz first called attention to this possibility in 1959. In the concept presented in figure 5, it is suggested that a specific fraction of the lymphocyte population is stimulated to action and that these sensitized cells are thereby rendered more susceptible to the killing effect of the immunosuppressive agent than the rest of the lymphocyte population. There is evidence that I do not have time to review here that at least partial tolerance is often accidentally produced in the course of clinical transplantation. From animal work, it would be expected that removal of the thymus gland (fig. 5) would facilitate this process by removing the source of reinforcements to the cell line under attack.

Fig. 5.

Hypothetical mechanisms by which nonspecific immunosuppression may lead to selective abrogation of the host immune response. Special susceptibility to these agents of a fraction of the lymphoid population could lead to exhaustion of a clone and, hence, tolerance. Since maintenance of such cell lines even in adult life is apparently thymus-dependent in experimental animals, thymectomy would be expected to aid the process; this appears to be true in rodents, hut such an effect of thymus removal has not been detected in dogs or humans. A possible protective role is also shown in immunoglobulins elaborated by the replicating cells. Conceivably the antibodies could act either at the site of the antigen (enhancement) or by affecting the macrophage processing of the antigen. See text for discussion. (By permission of W. B. Saunders Co., 1969.)

Enhancement

However, other lines of evidence have strongly indicated that tolerance is not the only mechanism by which graft acceptance is achieved. If tolerance were present, it should then be possible to transplant tissues and organs from the same donor to a recipient carrying an “accepted” homograft and to have these new tissues escape rejection. This has very often not been the case in experiments specifically designed to study this point. The conclusion has been that the graft itself may undergo alteration. Lately there has been much speculation that the primary-grafts achieve their relative state of invulnerability partly by a process known as enhancement. Here the hypothesis is that antigraft antibodies are produced in response to the homograft antigens and that they return to coat or protect the transplant by some means which is not understood (fig. 5).

Failure of Antigen Processing

A third possibility might be that the processing of the homograft antigens is somehow selectively prevented or made inefficient.

DRUGS AND GRAFT ACCEPTANCE

Each of the systemic immunosuppressive agents in wide use today (see below) as well as other less commonly employed drugs, can cause general immunologic crippling. Consequently, it has been customary to categorize as non-specific all the treatment protocols in which they have been employed. The implied criticism of using a bludgeon where a therapeutic scalpel would be preferable is not without justification. Nevertheless, the observations which I have just given you in capsule summary have indicated, to my mind incontrovertibly, that whole organ homotransplantation in conjunction with non-specific immunosuppressive therapy can and often does lead to selective abrogation of the host rejection response. The degree to which this objective is achieved is by all odds the most important determinant of prognosis in any given case.

The attempts to understand the resulting graft acceptance have been prompted by much more than idle curiosity, since it would be highly desirable to meet the conditions of graft acceptance before arrival of the homografts rather than hoping to achieve these conditions accidentally secondary to the actual transplantation. If this could be accomplished in advance, rejection could be prevented with far less crippling of the immune apparatus in the postoperative period. Numerous recent reports from several centers suggest that this objective may be realizable.

DRUG COMBINATIONS

The concepts which I have outlined are. I believe, the most important ones in understanding why the future prospects of organ transplantation are bright. I would now like to discuss an additional point of considerable practical interest which is the synergism that can be obtained using pharmacologic agents in combination for the prevention and reversal of rejection. In fact, the modern era of clinical transplantation was ushered in by the demonstration that azathioprine and prednisone could be advantageously used together with an effect exceeding the simple sum of the individual drugs. I have already given an example of the pharmacologic combination of these two agents (fig. 2).

A third potent immunosuppressive agent that has been widely employed has been heterologous antilymphocyte globulin (ALG). ALG is obtained from the serum of animals (such as horses) previously immunized against the lymphoid tissue of the species to be treated. For example, horses can be innoculated with human lymphocytes obtained from spleens, lymph nodes, or thymus glands (fig. 6). The ALG is then, extracted from the serum of the immunized animal. When given subcutaneously, intramuscularly, or intravenously, it has been shown to mitigate or prevent rejection. Moreover, it has an additive effect when administered with either azathioprine or prednisone.

Fig. 6.

Preparation in the horse of heterologous antilymphocyte globulin (ALG) for use in patients.

In our clinics, ALG has been administered as a third agent, added to azathioprine and prednisone (fig. 7) in all organ recipients treated since May, 1966. In most cases the course of ALG therapy has been limited to the first four postoperative months, during that critical time when “graft acceptance” is hoped for (see earlier). We have referred to this treatment program as a triple drug regimen as opposed to a double drug regimen consisting of azathioprine and prednisone only that was used before 1966.

Fig. 7.

The course of a patient who received antilymphocyte globulin (ALG) before and for the first 4 months after renal homotransplantation. The donor was an older brother. There was no early rejection. Prednisone therapy was started 40 days postoperatively. Note the insidious onset of late rejection after cessation of globulin therapy. This was treated by a moderate increase in the maintenance doses of steroids. This delayed complication occurred in only 2 of the first 20 recipients of intra familial homografts who were treated with ALG. It has been seen with about the same low frequency in subsequent cases. (By permission of Surg. Gynec. Obstet. 126 (1968): p. 1023.)

BENEFITS OF CLINICAL RENAL TRANSPLANTATION

With the background I have given you, I would now like to allude to the results that have actually been obtained with renal transplantation at the University of Colorado in an attempt to say something about the practical value of this procedure. The first case was in March of 1962. Since then more than 300 renal homotransplantations have been carried out. What I have to tell you about results today will be concerned only with those cases treated two years or longer ago. In this way, the pitfalls will be avoided of recounting the recent and relatively meaningless experience. There have been 189 cases with the long-term follow-up.

Related Cases

A positive judgment about the practical value of renal homotransplantation was not difficult with related donor and recipient since even at the beginning there was a substantial benefit if homografts were obtained from family members. Shown in figure 8 is the graphic fate of 131 consecutive patients who received kidneys from siblings, parents, or more distantly related donors such as aunts, uncles, and cousins. The followup in Series 1 is now 6½ to 8 years, in Series 2 from 4½ to 6 years, and in Series 3 from 2½ to 4⅓ years,

Fig. 8.

Life-survival curves in the three series of intrafamilial renal homotransplantations described in the text. In Series 3, the patients have been studied for at least 2½ years. The follow-ups in Series 2 and 1 are for a minimum of 4½ and 6½ years, respectively. At the end of each survival curve a numerator and denominator are given. The denominator tells the number of living patients, and the numerator denotes the number of original homografts that are still functioning.

The 71 patients in Series 1 and 2 were treated with azathioprine and prednisone. About two-thirds of these patients lived for at least two years and subsequent deaths have been relatively uncommon, so that 57 per cent of the combined Series 1 and 2 survive to date after 4½ to 8 years. The patients of Series 3 had heterologous antilympho-cyte globulin (ALG) in addition to azathioprine and prednisone. In the 60 cases of Series 3, the survival at one year was 92 per cent, at two years 88 per cent, and currently after 2½ to 4⅓ years it is 85 per cent.

The overall results were not remarkably influenced by the type of donor-recipient consanguinity. The present survival is about 70 per cent in all related recipients treated in Denver from 2½ to 8 years ago, without regard to the kinship of the donor whether these were siblings, parents, or more distant relatives (table 1).

TABLE 1.

Effect of Type of Donor Consanguinity upon Recipient Survival after Renal Homotransplantation

Sibling	44/66	(67%)
Parental	40/55	(73%)
Others	7/10 (2½ to 8 years)	(70%)

With the 58 transplantations between non-relatives (both living volunteers or recently deceased cadavers) the results were inferior to those with blood relatives. In figure 9 the Series 1, 2, and 3 conform roughly to the same intervals already defined above in the related cases. In the 1962 and 1963 era, only 33 per cent (6 of 18) of the unrelated recipients survived for a year. From 1964 to 1966, this figure rose to 52 per cent (12 of 23). In Series 3 the one-year survival in the non-related cases was S2 per cent or 14 of 17 patients. Subsequent to one year in all three series the losses continued at a rather steady rate, far more frequently than in the related cases so that only 19 (or 33 per cent) of these 58 recipients remain alive today. Even in the ALG-treated patients of Series 3, the final survival in non-related cases has drifted off so that it is now 65 per cent. Thus, a very considerable improvement should still be possible with future cases of transplantation from non-relatives. This is particularly important to realize when talking about the transplantation of the organs other than the kidney, including the liver and the heart, in which cases non-related cadaver organs must essentially always be used.

Fig. 9.

Life-survival curves in the three series of non-related renal homotransplantations described in the text. The minimum follow-ups in Series 1, 2, and 3 are 6½, 5½, and 1½ years. The significance of the numerators and denominators at the end of each curve is the same as in figure 8.

EXTRARENAL ORGANS

That concludes my remarks about renal transplantation. I hope it has been made clear that transplantation of other organs such as the liver, heart, and lung involves simply the application of the principles that have been elucidated with the kidney.

The Liver

Next to the kidney the greatest experience at the University of Colorado has been with liver homografts. So far we have had nine patients with incurable liver ailments who have lived for at least one year after removal of their own diseased livers and substitution of homo-grafts. The longest survival after liver replacement has now been almost 2½ years (fig. 10). That patient, an avid baseball fan now living in the Minneapolis area, has been restored to an almost completely normal life. He was born without bile ducts with which to drain the liver and lived a nightmare from one crisis to the next until the transplantation was carried out when he was almost 4 years old. He is now 6½ years old and with excellent liver function. He returns to Denver every three months or so for a checkup but otherwise lives quite a normal life.

Fig. 10.

Long-term survivor after liver replacement. The transplantation was almost 2½ years ago.

The one-year survival after liver transplantation in our hands has been approximately 30 per cent. Since many of the deaths have been due to surgical technical accidents of one or other, it is certain that this figure will improve as more experience is accumulated.

Heart Transplantation

We have performed three heart replacements, in September, 1968, in September, 1969, and in October, 1970. The first of these patients died of a fungus brain abscess after four months. The third one succumbed from an uncontrolled cardiac rejection twelve days after operation. The second recipient who is now fourteen months postoperative has had a perfect result. He is shown in figure 11 while on a stroll with two small companions. At the time the picture was taken, the child on his right was almost 2½ years after liver transplantation. The child on his left received a renal homograft more than seven years previously. While seemingly a heterogeneous collection, all three of these patients have had to face the same kinds of problems and have received similar kinds of treatment.

Fig. 11.

Three whole organ recipients: left, liver; center, heart; and right, kidney.

SUMMARY

Long-term survival has been obtained in humans after transplantation of kidneys, livers, and hearts. With all these organs, rejection has been shown to be a reversible process. In many cases, the stringency of the immunosuppression required to prevent homograft loss diminishes with the passage of time. With the demonstration that useful life can be prolonged with organ-transplantation procedures, the feasibility stage of this kind of treatment has passed. Nevertheless, transplantation is still an imperfect kind of therapy in which there is a need for future improvement.