BAD NEWS AND GOOD NEWS: THE PRESENT STATUS AND FUTURE PROSPECTS OF HUMAN KIDNEY TRANSPLANTATION JOHN P. MERRILL, M.D.* BOSTON
As the title of this paper suggests, the tide of kidney transplantation which began to flood in the early 50's seems to have approached slack water, if indeed not the ebb. On the other hand, there is increasing evidence that a new surge is in the making which will exceed the previous high water mark. Since any understanding of the present status of any art depends upon some knowledge of the past, it seems appropriate briefly to review the beginnings and early progress of transplantation of the human kidney. The first attempts at human kidney transplantation were made by French workers who have continued to be leaders in the field. Their early work was facilitated by a unique facet of the French penal system, the use of the guillotine to implement the death penalty. This source of very fresh and usually healthy cadaver kidneys was considerably simpler than the complicated legal and logistical system of procurement which we now employ. Nevertheless, it added nothing to the solution of the basic problem of transplantation, that of overcoming or "suppressing" the immunologic assault of the recipient upon the foreign antigens of the donor. In the early 50's our group, a coordinated team of internists, pathologists and surgeons, the latter headed by Dr. David Hume, embarked on a program of cadaver kidney transplantation following a series of laboratory experiments in dogs suggesting that the immune response might be modified, if only slightly. We were able to embark upon this venture by two timely developments: one, the first clinically successful artificial kidney which enabled us to keep severely uremic patients alive for weeks or months where no other form of therapy was available. Secondly, our success with this instrument coincided with the early work in cardiac surgery, a field in which the success rate was considerably lower than at the present time. Thus we too were able to obtain from time to time cadaver kidneys. In order to minimize the trauma of surgery, Dr. Hume devised a technique whereby the transplanted kidney was placed in a previously fashioned pocket in the thigh, the renal vessels anastomosed to the femoral vessels, and the donor ureter brought to the skin in a ureDirector, Renal Division, Peter Bent Brigham Hospital, 721 Huntington Avenue, Boston, Massachusetts 02115. *
171
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JOHN P. MERRILL
terostomy. Surprisingly, of some seven cases done in the early 50's five functioned well beyond what we might have expected from the animal work and with a minimum of immunosuppressive drugs. In 1954 Dr. Joseph Murray and Dr. J. Hartwell Harrison and I achieved the first truly successful kidney transplant. This was one between identical twins in whom of course no antigenic differences existed and therefore for whom the immunologic problem did not exist. However, in 1959 the Brigham Group transplanted a kidney from one nonidentical twin to his brother. Here there was clearcut evidence of antigenic disparity as evidenced by the rejection of a skin graft from the sick twin to the healthy one. Because of this antigenic difference, we attempted to suppress the immune response of the recipient to the donor antigens. For this we used an X-irradiation technique which had been proven in animal work to allow survival of skin grafts in animals. The lethal irradiation utilized in animals destroyed bone marrow, as well as antibody-forming cells and therefore required marrow grafting. This has not proven feasible in several human attempts. Our approach, therefore, was to use sub-lethal irradiation, i.e., enough radiation to suppress the immune response without destroying permanently the hematopoietic system. As one might imagine, there is very little data on which to estimate how much irradiation constituted a "sub-lethal dose" for the human. There was, however, one source from which a reasonable guess could be made. The dosage of irradiation, which was just below the lethal range, had been carefully calculated for the survivors of the Hiroshima atomic bomb blast. With the help of Dr. Shields Warren and information from this unfortunate event, we chose a dose of 450 Rads. of whole-body irradiation. Although the recipient's white count dropped virtually to zero, it eventually recovered spontaneously, the kidney survived, and the recipient is now alive and well some 16 years after surgery. Surgical techniques have changed since the first transplantation attempts. Because one could reasonably expect the kidney to survive for long periods, it was transplanted retroperitoneally into the pelvic fossa. The renal artery was anastamosed to the hypogastric artery, the renal vein to the iliac vein and the ureter implanted directly in the bladder. This is exactly the technique which is used today. Radiation was obviously too crude a tool and it was not until Dr. Joseph Murray and Dr. Roy Calne had demonstrated that Asathioprine, an analog of 6-Mercaptopurine, was an effective immunosuppressive agent in the dog that human kidney transplantation began on a large scale. Table I shows the immunosuppressive agents which have been utilized over the years. I think it is of interest to note that not only is the surgical technique identical to that used in 1959, but of all the agents
HUMAN KIDNEY TRANSPLANTATION
173
TABLE I Immunosuppression for Human Renal Allografts Prednisone (5) Radiation (?) Actinomycin (?) ECI (2) Indomethacin (?) Imuran (3)
ALG (?) TDF (?) Heparin (1) Vasodilators (?) Cyclophosphamide (3)
Numbers in parenthesis describe efficacy (5 = most effective).
utilized the two employed in the first cadaver transplant which survived for more than a year are those which remain the mainstay of our immunosuppressive effort today, i.e., Prednisone and Asathioprine. Antilymphocyte serum, or the globulin derived therefrom (ALG), has received numerous trials in the human and although extremely effective in the experimental animal, has not proved to be of great value in the human. I The hazards of agents which suppress the immune response in general are obvious. The first and foremost, of course, is infection. For several years we attempted to combat infection by using sterile techniques and isolation of the patient. It soon became apparent, however, that the problem was not that of organisms brought in to the patient's room by the professional staff, but opportunistic infections, including those of the patient's own gram negative flora, fungi, and viral agents which in a healthy individual do not ordinarily cause illness. Another less frequent, but even more dramatic complication of immunosuppressive therapy is the increased incidence of malignancy, particularly that of the reticuloendothelial cells, apparently caused by suppression of the surveillance mechanism by the immunosuppressive agents utilized. Side by side with the clinical efforts there grew up a vast body of experimental work aimed at delineating the details of the immune response and its effect upon the graft. From rather simple and naive descriptions there has arisen a vast and complicated body of knowledge describing the immune response to the transplantation of foreign tissue, i.e., allografts. Our present knowledge of these events is summarized in Fig. 1. Obviously, the magnitude of the immune response against foreign tissue depends upon the strength of the antigenic differences. Human transplantation antigens have now been well characterized and apparently reside of two sub-loci of a chromosome. Accurate serologic techniques now exist for identifying these antigens. Since each individual inherits one chromosome containing two of the sub-loci from each
174
JOHN P. MERRILL Slem Cell
FIG. 1. Overall scheme of the development of effector mechanisms in graft rejection. Bone marrow stem cells differentiate under the influence of the thymus gland into mature thymus-derived (T) lymphocytes or under the influence of an equivalent to the avian bursa of Fabricius into mature bone-marrow-derived (B) lymphocytes. Exposure to antigen (A) results in an interaction between T cells and B cells, and often involves macrophages. The sensitized B cells after mitoses develop into immunoglobulin-secreting cells (e.g., plasma cells), illustrated here by IgG and IgM. Such immunoglobulins may form immune complexes with antigen in the circulation which activate the complement sequence, or they may react directly with antigens on the blood vessel surface. Elaboration of secondary mediators, including the products of complement activation, results in vascular damage as illustrated. Sensitized T lymphocytes are the primary effector cells in cell-mediated immunity (CMI) and may react directly with antigens in the graft to exert a cytotoxic effect. In addition, T cells release factors, such as macrophage migration inhibition factor (MIF) which may accelerate the rate of mononuclear cell infiltration. In addition, it has been shown that unsensitized non-T cells (K cells) can be activated to exert cytotoxic effects by the fixation of IgG to target cells, followed by interaction of the IgG (Fc portion) with a receptor on the K cell. Non-immune B cells may have K cell activity, but since other mononuclear cells can react with IgG on target cells, the K cell is shown as having a separate lineage. Finally, platelet aggregation and thrombosis can occur following the endothelial damage induced by any of these mechanisms.
parent, there are four sub-loci containing a potential of 37 transplantation antigens which have been defined. The laws of genetics state that of five offspring born of the same parents, two have a chance of having four identical human transplantation antigens. Thus one would expect virtually no immune response when tissue is transplanted between these
175
HUMAN KIDNEY TRANSPLANTATION
two siblings. We know now, however, that there is certainly one and probably several other loci which cannot be identified by the usual serologic techniques. Of these perhaps the most important is the MLC-locus. This is the locus which is identified by the fact that cells from HLA identical siblings placed in lymphocyte culture (MLC) may stimulate each other and this fact we know now can result in the rejection of a transplant. This accounts for the surprising and unfortunate occurrence of renal allograft rejection, even between siblings who have been found to be antigenically identical by our serologic techniques. With this knowledge at hand, what are the clinical results of human kidney transplantation? These are shown in Table II taken from the 1974 Transplant Registry.2 If one looks only at the results of cadaver transplantation, one notices no improvement in graft survival and perhaps some worsening in the past three years. The fact that patient survival has improved is due to the realization that it is better to have the patient alive than the kidney and thus the dosage of immunosuppressive agents, with all their toxic side effects, has been reduced in order to improve the patient survival. As of this moment, therefore, the picture, at least as portrayed by the clinical results, seems bleak indeed. The future, however, looks somewhat brighter. Obviously, the ultimate aim of immunosuppressive therapy would be to produce specific immunologic nonresponsiveness, i.e., to produce in the recipient a state whereby he was unable to respond only to the antigens of the graft but could mount a normal immunologic offensive against gram negative bacteria, viruses, fungi, etc. At the present time it is possible to do this in the animal laboratory. However, in order to apply such results to the human, one must employ techniques which are not injurious to the recipient. I would like to mention one or two of these in attempting to assure you that perhaps the tide will begin to flood again. All antibodies are not destructive antibodies. For many years it has been known that some antibodies are "blocking antibodies". Essentially what this means is that these antibodies combine with the antigenic site of the donor but do not destroy the donor cell. In essence, having blocked TABLE II Survival Rate (%) Donor Source
Sibling Parent
Cadaver
1 yr. 2 yrs. 1 yr. 2 yrs. 1 yr. 2 yrs.
Graft
Patient
79.9 73.7 71.7 61.1 50.6 42.6
90.9 86.8 86.6 81.8 71.8 65.6
176
JOHN P. MERRILL
the donor antigenic site, they prevent its combination with antibodies which can be destructive. We know now that in most cases antibodies composed of. immunoglobulin are double-ended, that is they have two combining sites; one to combine with the antigen and the second to combine with components of serum complement which result eventually in the "complement cascade" which causes a sequence of events destroying the cell. It is now possible to split the immunoglobulin molecule into two fragments, one of which contains the combining site but not the complement fixing site. This is a true blocking antibody. We have prepared such antibodies in dogs and injecting them into the recipient dog have transplanted kidneys which have survived some 4 to 5 times the normal control period.3 The importance of this experiment, of course, is that such blocking antibodies are specific for donor antigen and do not result in total immunosuppression. Thus the dog (or the patient) can retain the graft without becoming susceptible to other invasive antigens such as viruses, fungi, gram negative bacteria, etc. Furthermore, such antibodies are available from patients who have received transfusions of human blood and thus become sensitized to human antigens. Most important is that the administration of human immune globulin, even fragmented as we have proposed, is perfectly acceptable to the FDA. In our own laboratory we have shown that antibodies to tissue antigens apparently are not the total answer to tissue rejection. HLA identical siblings, for example, may reject grafts because of differences at the MLC locus. Dr. Strom in our group has demonstrated that the so-called enhancing or blocking antibody is produced by the antigen located at the MLC site and that the HLA or toxic antibodies may be absorbed out with platelets and red blood cells, thus leaving only a "blocking antibody". Finally, Dr. Strom in an elegant experiment has shown that sensitized lymphocytes, certainly responsible in part for killing of tissue grafts, may have their killing ability modified by the administration of agents which increase the cellular content of cyclic-AMP. Two such drugs have been available for clinical use for many years. They are isoproterenol and aminophyllin. These agents markedly decrease the killing ability of sensitized cells and in combination this decrease is cumulative.4 The initial studies were done in vitro, but in vivo the results are exciting. Rats which without any pretreatment would ordinarily destroy an allografted kidney within 7-9 days, are alive and well 3 to 4 months after the administration of isoproterenol and aminophyllin. Again, since these agents may be used in humans, their promise for the modification of allografts, particularly kidney transplants in humans, suggest that not all the news is bad.
HUMAN KIDNEY TRANSPLANTATION
1. 2.
3. 4.
177
REFERENCES MERRILL, J. P.: Diagnosis and Management of Rejection in Allografted Kidneys. Transplantation Proc. 111: 287, 1971. Advisory Committee to the Renal Transplant Registry (1973): The Eleventh Report of the Human Renal Transplant Registry. J. Amer. Med. Assoc. 226: 1197. WREN, S. F. G., et al.: Passive Enhancement of Canine Renal Allografts with Polyspecific F (AB') 2 Fragments. Surgery 76: 1, 112-120, 1974. STROM, T. B., et al.: The Modulating Influence of Cyclic Nucleotides Upon LymphocyteMediated Cytotoxicity. J. Exp. Med. 138: 2, 381-393, 1973.
DISCUSSION DR. GORDON WALKER (Baltimore): I wonder if I could ask Dr. Merrill whether he would be willing to modulate his stand about the bad news a bit. It's fair to say, I think, that in the land of the blind, the one-eyed man is likely to be king, and if you look at where kidney transplantation has come (due largely to the efforts of Dr. Merrill and his collegues initially), it's a far cry from what a patient with chronic uremia faced just about fifteen or eighteen years ago. Perhaps we shouldn't be too harsh on ourselves if only roughly a little less than one out of two has a good result when you put a kidney in. We have recently looked at our experience with about a hundred thirty transplants, largely cadaver based. About 85 per cent of them were cadavers, and the graft survivals for five years using life table techniques was a little better than 40 per cent which is a little better than the overall data in registry. But more importantly nearly 85 per cent survived for the five years which is really a very substantial form of treatment for a disease that was recently uniformly fatal. There were a couple of things that emerged from looking at that data that I would like to ask about, one was that when we examined mean creatinine values over the first four years, there really was no tendency for the mean value to rise. If a rejection occurred, the standard error would grow very substantially and then shrink as that kidney disappeared. But in the ones remaining, there was no tendency for the creatinine to rise. I was surprised at this. I would have thought that if, as we suppose, there is some kind of chronic rejection going on in all of the patients who have cadaver kidneys, there ought to be some evidence of progressive destruction of renal tissue, but we didn't see it. The other thing we couldn't convince ourselves, (and I think this is important because of the implications to a patient with respect to risk) that we did very much by treating threatened rejections once it appeared, that a rejection had reached a level of severity that permitted it to be clinical recognizable. If you will let me exclude what happened in the first three or four weeks after transplant (because we were a lot less confident about what we're dealing with often there), the remainder of the individuals seems to go ahead and lose their kidneys whether we treated them vigorously or not. I think that is an important point, because it may be we are simply selecting those patients who will accept kidneys and we shouldn't worry about vigorous treatment of rejection at least at our present state of knowledge. I would like to ask you if you could shed light on either of those two presumptions from our present data examinations. DR. MERRILL: Let me take the last one first. I certainly agree with you. I think what we are doing when we treat rejection vigorously, or have to, is indeed picking out individuals who have some incompatibility such as at the MLC locus which we haven't recognized. And their prognosis is a lot worse if you take a large series, not necessarily individually, but certainly statistically it is. It is so bad in fact that Dr. Sam Kountz, who, as you know, has done as many of these as any of us, will not treat a patient twice for rejection. He takes the kidney out and puts in a new one if he has to treat the first rejection vigorously. So that certainly is correct. I am still discouraged unfortunately because in spite of the fact, and I
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JOHN P. MERRILL
gather your 85 per cent was patient survival and not cadaver kidney function survival, is that correct? DR. WALKER: Yes. DR. MERRILL: It is certainly true that the patient survival has improved. I deliberately did not put that on the slide, but it's improved because we've had the good sense to do just exactly what you are suggesting, and that is not to kill our patients who are bad matches with immunosuppressive therapy. However, If you look at the number of patients who receive cadaver kidneys and fail and do not go back on the dialysis program, their mortality is greater than the mortality for the dialysis program alone. This means you are subjecting your patient to a much increased risk for less than a 50 per cent chance that he is going to get a functioning kidney. And this is what is bad news. I must add also something that I didn't because I didn't want to bring tears to all your eyes, but there are other bad things that are happening. The recurrence rate for nephritis for instance is 15 per cent, and in a certain kind of nephritis it is 40 per cent and there is nothing that we seem to be able to do about it. Furthermore although all of us said if you get by without a rise in creatinine for two years, you are absolutely fine, we are now seeing rejections with recurrent nephritis 5, 6 and even 7 years after transplantation now. I think the last word is not in yet and hopefully with some of the newer tools, we will be able to modify that gloomy view. DR. ROBERT J. GLASER (Palo Alto): In that connection, John, Dr. Harrison Sadler and his group at the University of California Medical Center in San Francisco, have been studying the quality of life in patients who have had renal transplants. Although there is no question about an increased survival, a very large number of these people have a very difficult existance. Many lose their jobs and end up on welfare. The incidence of divorce is high. Has that been your experience? DR. MERRILL: Oh, absolutely. These people, of course, may live in constant fear of kidney rejection, and the effects of prednisone. The instances of aseptic necrosis of the hip is absolutely incredible. 15 per cent of our people have aseptic necrosis of the hip. These are out-patients whose kidneys were functioning perfectly well. I believe it is because it got started during the dialysis period, but it does represent a problem and you point out they have a good many psychologic and social problems as well. DR. ROBERT H. FURMAN (Indianapolis): I wonder, John, while we're on such gloomy aspects of the situation, do you envision problems with carcinogenicity in the management of the immune aspects? DR. MERRILL: I thought I mentioned that, perhaps not. There is, of course, a marked increase in the incidence of malignant tumors of the reticuloendothelial system in these individuals. However if you plot the number of tumors against the number of transplants, it is not enough to deter us, but it is about 15 to 25 times more than for the age-sex matched population at risk. Many of these patients, both during the process of dialysis and even after transplantation, show marked hyperlipidemia, triglyceridemea, and since many of them die of vascular disease contracted during dialysis and even enhanced after transplantation, this remains a problem too.
As the title of this paper suggests, the tide of kidney transplantation which began to flood in the early 50's seems to have approached slack water, if indeed not the ebb. On the other hand, there is increasing evidence that a new surge is in the making which will exceed the previous high water mark. Since any understanding of the present status of any art depends upon some knowledge of the past, it seems appropriate briefly to review the beginnings and early progress of transplantation of the human kidney. The first attempts at human kidney transplantation were made by French workers who have continued to be leaders in the field. Their early work was facilitated by a unique facet of the French penal system, the use of the guillotine to implement the death penalty. This source of very fresh and usually healthy cadaver kidneys was considerably simpler than the complicated legal and logistical system of procurement which we now employ. Nevertheless, it added nothing to the solution of the basic problem of transplantation, that of overcoming or "suppressing" the immunologic assault of the recipient upon the foreign antigens of the donor. In the early 50's our group, a coordinated team of internists, pathologists and surgeons, the latter headed by Dr. David Hume, embarked on a program of cadaver kidney transplantation following a series of laboratory experiments in dogs suggesting that the immune response might be modified, if only slightly. We were able to embark upon this venture by two timely developments: one, the first clinically successful artificial kidney which enabled us to keep severely uremic patients alive for weeks or months where no other form of therapy was available. Secondly, our success with this instrument coincided with the early work in cardiac surgery, a field in which the success rate was considerably lower than at the present time. Thus we too were able to obtain from time to time cadaver kidneys. In order to minimize the trauma of surgery, Dr. Hume devised a technique whereby the transplanted kidney was placed in a previously fashioned pocket in the thigh, the renal vessels anastomosed to the femoral vessels, and the donor ureter brought to the skin in a ureDirector, Renal Division, Peter Bent Brigham Hospital, 721 Huntington Avenue, Boston, Massachusetts 02115. *
171
172
JOHN P. MERRILL
terostomy. Surprisingly, of some seven cases done in the early 50's five functioned well beyond what we might have expected from the animal work and with a minimum of immunosuppressive drugs. In 1954 Dr. Joseph Murray and Dr. J. Hartwell Harrison and I achieved the first truly successful kidney transplant. This was one between identical twins in whom of course no antigenic differences existed and therefore for whom the immunologic problem did not exist. However, in 1959 the Brigham Group transplanted a kidney from one nonidentical twin to his brother. Here there was clearcut evidence of antigenic disparity as evidenced by the rejection of a skin graft from the sick twin to the healthy one. Because of this antigenic difference, we attempted to suppress the immune response of the recipient to the donor antigens. For this we used an X-irradiation technique which had been proven in animal work to allow survival of skin grafts in animals. The lethal irradiation utilized in animals destroyed bone marrow, as well as antibody-forming cells and therefore required marrow grafting. This has not proven feasible in several human attempts. Our approach, therefore, was to use sub-lethal irradiation, i.e., enough radiation to suppress the immune response without destroying permanently the hematopoietic system. As one might imagine, there is very little data on which to estimate how much irradiation constituted a "sub-lethal dose" for the human. There was, however, one source from which a reasonable guess could be made. The dosage of irradiation, which was just below the lethal range, had been carefully calculated for the survivors of the Hiroshima atomic bomb blast. With the help of Dr. Shields Warren and information from this unfortunate event, we chose a dose of 450 Rads. of whole-body irradiation. Although the recipient's white count dropped virtually to zero, it eventually recovered spontaneously, the kidney survived, and the recipient is now alive and well some 16 years after surgery. Surgical techniques have changed since the first transplantation attempts. Because one could reasonably expect the kidney to survive for long periods, it was transplanted retroperitoneally into the pelvic fossa. The renal artery was anastamosed to the hypogastric artery, the renal vein to the iliac vein and the ureter implanted directly in the bladder. This is exactly the technique which is used today. Radiation was obviously too crude a tool and it was not until Dr. Joseph Murray and Dr. Roy Calne had demonstrated that Asathioprine, an analog of 6-Mercaptopurine, was an effective immunosuppressive agent in the dog that human kidney transplantation began on a large scale. Table I shows the immunosuppressive agents which have been utilized over the years. I think it is of interest to note that not only is the surgical technique identical to that used in 1959, but of all the agents
HUMAN KIDNEY TRANSPLANTATION
173
TABLE I Immunosuppression for Human Renal Allografts Prednisone (5) Radiation (?) Actinomycin (?) ECI (2) Indomethacin (?) Imuran (3)
ALG (?) TDF (?) Heparin (1) Vasodilators (?) Cyclophosphamide (3)
Numbers in parenthesis describe efficacy (5 = most effective).
utilized the two employed in the first cadaver transplant which survived for more than a year are those which remain the mainstay of our immunosuppressive effort today, i.e., Prednisone and Asathioprine. Antilymphocyte serum, or the globulin derived therefrom (ALG), has received numerous trials in the human and although extremely effective in the experimental animal, has not proved to be of great value in the human. I The hazards of agents which suppress the immune response in general are obvious. The first and foremost, of course, is infection. For several years we attempted to combat infection by using sterile techniques and isolation of the patient. It soon became apparent, however, that the problem was not that of organisms brought in to the patient's room by the professional staff, but opportunistic infections, including those of the patient's own gram negative flora, fungi, and viral agents which in a healthy individual do not ordinarily cause illness. Another less frequent, but even more dramatic complication of immunosuppressive therapy is the increased incidence of malignancy, particularly that of the reticuloendothelial cells, apparently caused by suppression of the surveillance mechanism by the immunosuppressive agents utilized. Side by side with the clinical efforts there grew up a vast body of experimental work aimed at delineating the details of the immune response and its effect upon the graft. From rather simple and naive descriptions there has arisen a vast and complicated body of knowledge describing the immune response to the transplantation of foreign tissue, i.e., allografts. Our present knowledge of these events is summarized in Fig. 1. Obviously, the magnitude of the immune response against foreign tissue depends upon the strength of the antigenic differences. Human transplantation antigens have now been well characterized and apparently reside of two sub-loci of a chromosome. Accurate serologic techniques now exist for identifying these antigens. Since each individual inherits one chromosome containing two of the sub-loci from each
174
JOHN P. MERRILL Slem Cell
FIG. 1. Overall scheme of the development of effector mechanisms in graft rejection. Bone marrow stem cells differentiate under the influence of the thymus gland into mature thymus-derived (T) lymphocytes or under the influence of an equivalent to the avian bursa of Fabricius into mature bone-marrow-derived (B) lymphocytes. Exposure to antigen (A) results in an interaction between T cells and B cells, and often involves macrophages. The sensitized B cells after mitoses develop into immunoglobulin-secreting cells (e.g., plasma cells), illustrated here by IgG and IgM. Such immunoglobulins may form immune complexes with antigen in the circulation which activate the complement sequence, or they may react directly with antigens on the blood vessel surface. Elaboration of secondary mediators, including the products of complement activation, results in vascular damage as illustrated. Sensitized T lymphocytes are the primary effector cells in cell-mediated immunity (CMI) and may react directly with antigens in the graft to exert a cytotoxic effect. In addition, T cells release factors, such as macrophage migration inhibition factor (MIF) which may accelerate the rate of mononuclear cell infiltration. In addition, it has been shown that unsensitized non-T cells (K cells) can be activated to exert cytotoxic effects by the fixation of IgG to target cells, followed by interaction of the IgG (Fc portion) with a receptor on the K cell. Non-immune B cells may have K cell activity, but since other mononuclear cells can react with IgG on target cells, the K cell is shown as having a separate lineage. Finally, platelet aggregation and thrombosis can occur following the endothelial damage induced by any of these mechanisms.
parent, there are four sub-loci containing a potential of 37 transplantation antigens which have been defined. The laws of genetics state that of five offspring born of the same parents, two have a chance of having four identical human transplantation antigens. Thus one would expect virtually no immune response when tissue is transplanted between these
175
HUMAN KIDNEY TRANSPLANTATION
two siblings. We know now, however, that there is certainly one and probably several other loci which cannot be identified by the usual serologic techniques. Of these perhaps the most important is the MLC-locus. This is the locus which is identified by the fact that cells from HLA identical siblings placed in lymphocyte culture (MLC) may stimulate each other and this fact we know now can result in the rejection of a transplant. This accounts for the surprising and unfortunate occurrence of renal allograft rejection, even between siblings who have been found to be antigenically identical by our serologic techniques. With this knowledge at hand, what are the clinical results of human kidney transplantation? These are shown in Table II taken from the 1974 Transplant Registry.2 If one looks only at the results of cadaver transplantation, one notices no improvement in graft survival and perhaps some worsening in the past three years. The fact that patient survival has improved is due to the realization that it is better to have the patient alive than the kidney and thus the dosage of immunosuppressive agents, with all their toxic side effects, has been reduced in order to improve the patient survival. As of this moment, therefore, the picture, at least as portrayed by the clinical results, seems bleak indeed. The future, however, looks somewhat brighter. Obviously, the ultimate aim of immunosuppressive therapy would be to produce specific immunologic nonresponsiveness, i.e., to produce in the recipient a state whereby he was unable to respond only to the antigens of the graft but could mount a normal immunologic offensive against gram negative bacteria, viruses, fungi, etc. At the present time it is possible to do this in the animal laboratory. However, in order to apply such results to the human, one must employ techniques which are not injurious to the recipient. I would like to mention one or two of these in attempting to assure you that perhaps the tide will begin to flood again. All antibodies are not destructive antibodies. For many years it has been known that some antibodies are "blocking antibodies". Essentially what this means is that these antibodies combine with the antigenic site of the donor but do not destroy the donor cell. In essence, having blocked TABLE II Survival Rate (%) Donor Source
Sibling Parent
Cadaver
1 yr. 2 yrs. 1 yr. 2 yrs. 1 yr. 2 yrs.
Graft
Patient
79.9 73.7 71.7 61.1 50.6 42.6
90.9 86.8 86.6 81.8 71.8 65.6
176
JOHN P. MERRILL
the donor antigenic site, they prevent its combination with antibodies which can be destructive. We know now that in most cases antibodies composed of. immunoglobulin are double-ended, that is they have two combining sites; one to combine with the antigen and the second to combine with components of serum complement which result eventually in the "complement cascade" which causes a sequence of events destroying the cell. It is now possible to split the immunoglobulin molecule into two fragments, one of which contains the combining site but not the complement fixing site. This is a true blocking antibody. We have prepared such antibodies in dogs and injecting them into the recipient dog have transplanted kidneys which have survived some 4 to 5 times the normal control period.3 The importance of this experiment, of course, is that such blocking antibodies are specific for donor antigen and do not result in total immunosuppression. Thus the dog (or the patient) can retain the graft without becoming susceptible to other invasive antigens such as viruses, fungi, gram negative bacteria, etc. Furthermore, such antibodies are available from patients who have received transfusions of human blood and thus become sensitized to human antigens. Most important is that the administration of human immune globulin, even fragmented as we have proposed, is perfectly acceptable to the FDA. In our own laboratory we have shown that antibodies to tissue antigens apparently are not the total answer to tissue rejection. HLA identical siblings, for example, may reject grafts because of differences at the MLC locus. Dr. Strom in our group has demonstrated that the so-called enhancing or blocking antibody is produced by the antigen located at the MLC site and that the HLA or toxic antibodies may be absorbed out with platelets and red blood cells, thus leaving only a "blocking antibody". Finally, Dr. Strom in an elegant experiment has shown that sensitized lymphocytes, certainly responsible in part for killing of tissue grafts, may have their killing ability modified by the administration of agents which increase the cellular content of cyclic-AMP. Two such drugs have been available for clinical use for many years. They are isoproterenol and aminophyllin. These agents markedly decrease the killing ability of sensitized cells and in combination this decrease is cumulative.4 The initial studies were done in vitro, but in vivo the results are exciting. Rats which without any pretreatment would ordinarily destroy an allografted kidney within 7-9 days, are alive and well 3 to 4 months after the administration of isoproterenol and aminophyllin. Again, since these agents may be used in humans, their promise for the modification of allografts, particularly kidney transplants in humans, suggest that not all the news is bad.
HUMAN KIDNEY TRANSPLANTATION
1. 2.
3. 4.
177
REFERENCES MERRILL, J. P.: Diagnosis and Management of Rejection in Allografted Kidneys. Transplantation Proc. 111: 287, 1971. Advisory Committee to the Renal Transplant Registry (1973): The Eleventh Report of the Human Renal Transplant Registry. J. Amer. Med. Assoc. 226: 1197. WREN, S. F. G., et al.: Passive Enhancement of Canine Renal Allografts with Polyspecific F (AB') 2 Fragments. Surgery 76: 1, 112-120, 1974. STROM, T. B., et al.: The Modulating Influence of Cyclic Nucleotides Upon LymphocyteMediated Cytotoxicity. J. Exp. Med. 138: 2, 381-393, 1973.
DISCUSSION DR. GORDON WALKER (Baltimore): I wonder if I could ask Dr. Merrill whether he would be willing to modulate his stand about the bad news a bit. It's fair to say, I think, that in the land of the blind, the one-eyed man is likely to be king, and if you look at where kidney transplantation has come (due largely to the efforts of Dr. Merrill and his collegues initially), it's a far cry from what a patient with chronic uremia faced just about fifteen or eighteen years ago. Perhaps we shouldn't be too harsh on ourselves if only roughly a little less than one out of two has a good result when you put a kidney in. We have recently looked at our experience with about a hundred thirty transplants, largely cadaver based. About 85 per cent of them were cadavers, and the graft survivals for five years using life table techniques was a little better than 40 per cent which is a little better than the overall data in registry. But more importantly nearly 85 per cent survived for the five years which is really a very substantial form of treatment for a disease that was recently uniformly fatal. There were a couple of things that emerged from looking at that data that I would like to ask about, one was that when we examined mean creatinine values over the first four years, there really was no tendency for the mean value to rise. If a rejection occurred, the standard error would grow very substantially and then shrink as that kidney disappeared. But in the ones remaining, there was no tendency for the creatinine to rise. I was surprised at this. I would have thought that if, as we suppose, there is some kind of chronic rejection going on in all of the patients who have cadaver kidneys, there ought to be some evidence of progressive destruction of renal tissue, but we didn't see it. The other thing we couldn't convince ourselves, (and I think this is important because of the implications to a patient with respect to risk) that we did very much by treating threatened rejections once it appeared, that a rejection had reached a level of severity that permitted it to be clinical recognizable. If you will let me exclude what happened in the first three or four weeks after transplant (because we were a lot less confident about what we're dealing with often there), the remainder of the individuals seems to go ahead and lose their kidneys whether we treated them vigorously or not. I think that is an important point, because it may be we are simply selecting those patients who will accept kidneys and we shouldn't worry about vigorous treatment of rejection at least at our present state of knowledge. I would like to ask you if you could shed light on either of those two presumptions from our present data examinations. DR. MERRILL: Let me take the last one first. I certainly agree with you. I think what we are doing when we treat rejection vigorously, or have to, is indeed picking out individuals who have some incompatibility such as at the MLC locus which we haven't recognized. And their prognosis is a lot worse if you take a large series, not necessarily individually, but certainly statistically it is. It is so bad in fact that Dr. Sam Kountz, who, as you know, has done as many of these as any of us, will not treat a patient twice for rejection. He takes the kidney out and puts in a new one if he has to treat the first rejection vigorously. So that certainly is correct. I am still discouraged unfortunately because in spite of the fact, and I
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gather your 85 per cent was patient survival and not cadaver kidney function survival, is that correct? DR. WALKER: Yes. DR. MERRILL: It is certainly true that the patient survival has improved. I deliberately did not put that on the slide, but it's improved because we've had the good sense to do just exactly what you are suggesting, and that is not to kill our patients who are bad matches with immunosuppressive therapy. However, If you look at the number of patients who receive cadaver kidneys and fail and do not go back on the dialysis program, their mortality is greater than the mortality for the dialysis program alone. This means you are subjecting your patient to a much increased risk for less than a 50 per cent chance that he is going to get a functioning kidney. And this is what is bad news. I must add also something that I didn't because I didn't want to bring tears to all your eyes, but there are other bad things that are happening. The recurrence rate for nephritis for instance is 15 per cent, and in a certain kind of nephritis it is 40 per cent and there is nothing that we seem to be able to do about it. Furthermore although all of us said if you get by without a rise in creatinine for two years, you are absolutely fine, we are now seeing rejections with recurrent nephritis 5, 6 and even 7 years after transplantation now. I think the last word is not in yet and hopefully with some of the newer tools, we will be able to modify that gloomy view. DR. ROBERT J. GLASER (Palo Alto): In that connection, John, Dr. Harrison Sadler and his group at the University of California Medical Center in San Francisco, have been studying the quality of life in patients who have had renal transplants. Although there is no question about an increased survival, a very large number of these people have a very difficult existance. Many lose their jobs and end up on welfare. The incidence of divorce is high. Has that been your experience? DR. MERRILL: Oh, absolutely. These people, of course, may live in constant fear of kidney rejection, and the effects of prednisone. The instances of aseptic necrosis of the hip is absolutely incredible. 15 per cent of our people have aseptic necrosis of the hip. These are out-patients whose kidneys were functioning perfectly well. I believe it is because it got started during the dialysis period, but it does represent a problem and you point out they have a good many psychologic and social problems as well. DR. ROBERT H. FURMAN (Indianapolis): I wonder, John, while we're on such gloomy aspects of the situation, do you envision problems with carcinogenicity in the management of the immune aspects? DR. MERRILL: I thought I mentioned that, perhaps not. There is, of course, a marked increase in the incidence of malignant tumors of the reticuloendothelial system in these individuals. However if you plot the number of tumors against the number of transplants, it is not enough to deter us, but it is about 15 to 25 times more than for the age-sex matched population at risk. Many of these patients, both during the process of dialysis and even after transplantation, show marked hyperlipidemia, triglyceridemea, and since many of them die of vascular disease contracted during dialysis and even enhanced after transplantation, this remains a problem too.
