THE TRANSPLANTATION OF HOMOLOGOUS TISSUE AND ITS SURGICAL APPLICATIONS Hunterian Lecture delivered at the Royal College of Surgeons of England on 18th March, 1952 by Michael F. A. Woodruff, M.D., M.S., F.R.C.S. Senior Lecturer in Surgery, University of Aberdeen ADVANCES IN OPERATIVE and anaesthetic technique have rendered almost every part of the body accessible to the surgeon, and the treatment of disease by radical excision of pathological tissues or organs has developed in a manner undreamed of half a century ago. We would, indeed, seem to be approaching the limit of progress in this direction. On the other hand advances in what may be termed surgical replacement therapy, i.e., the replacement of diseased, injured or absent structures by trans- plantation, have been by comparison meagre. The reason for this difference is easy to see. Progress in the clinical use of transplants, and in particular of transplants of homologous tissue (i.e., tissue derived from another individual), has been held up by lack of knowledge of the biological principles involved. I shall mention later some of John Hunter's own contributions to this subject.' It is a fair indication of the formidable nature of the problem that he did not get very far. Yet Hunter's influence has been of supreme importance in this as in so many other fields of surgery for he showed that great advances can come only as a result of accurate observation and scientific experiment. This lesson has been hard to learn. In the field of trans- plantation it has been largely ignored from Hunter's time until the last decade or two. Recently, however, biologists and surgeons have combined to attack the problem in a rational manner. Already much has been discovered and some of the knowledge gained has found clinical application. It is my purpose in this lecture to review the relevant experimental work and then to discuss the present status of homotransplantation in surgery and the prospects for the future. BASIC BIOLOGICAL PRINCIPLES Classification of Transplants We shall be concerned primarily with homotransplants, i.e., trans- plants made from one human being to another or from one animal to another of the same species. These may be classified in the following ways:- (1) According to the organ or tissue transplanted. Under this heading it is necessary to distinguish between normal and neoplastic tissue, and in the former case between tissue from adults, immature animals and embryos. 173 M. F. A. WOODRUFF (2) According to whether the material is transplanted fresh or after a period of storage. (3) According to the site to which the transplant is made. (4) As free transplants, parabiotic transplants and transplants by vascular anastomosis. A free transplant consists of an isolated piece of tissue which, if it becomes vascularized at all, does so as the result of ingrowth of vessels from the surrounding host tissue. In transplantation by parabiosis the donor and recipient are bound together. The transplant remains temporarily connected to the donor by a pedicle and thus continues to derive its blood supply from the donor. When a new blood supply has been established from the host the pedicle is severed and the animals are separated. In transplantation by vascular anastomosis continuity is established between the blood vessels of transplant and host at the time of operation. THE FATE OF HOMOTRANSPLANTS Assuming that the host survives we may distinguish four possibilities as regards the fate of the transplant: (1) The transplant becomes established and survives indefinitely. This need not imply that every single cell of the transplant survives. The term survival may properly be applied if most of the transplant survives or if, as sometimes happens, much of the transplant is destroyed but the lost tissue is subsequently replaced by regeneration from the surviving remnant. (2) The transplant is gradually replaced by similar tissue derived from the host. Although, finally, none of the original transplant remains, the gross appearance may suggest erroneously that the transplant has survived. This " creeping replacement" occurs characteristically with transplants of bone and large blood vessels. (3) The transplant survives for a time but is subsequently destroyed leaving either no trace or a mass ofscar tissue. We may say then that the transplant becomes established but undergoes secondary destruction. (4) The transplant is rapidly destroyed. In this event we may say that the transplant fails to become established or that it undergoes primary destruction. CRITERIA OF SURVIVAL Evidence of the survival of a transplant may be based on tests for functional activity or on biopsy findings. Tests for Functional Activity Tests for functional activity can be applied most readily to transplants of glandular tissue. They are of two main kinds:- (1) We may test directly the functional activity of the transplant. For example we may study the output of fluid and electrolytes from a transplanted kidney or the uptake of radioactive iodine by a transplant 174 HUNTERIAN LECTURE of thyroid. Tests of this type are ideal in theory but may be difficult to apply in practice. (2) We may apply tests to the host as a whole and from these deduce the degree of activity of the transplant. Tests of this type are used with endocrine transplants; they are particularly useful when there has been a gross endocrine deficiency prior to transplantation. Thus, for example, after transplantation of adrenal tissue to an adrenalectomized recipient we may study the effect of A.C.T.H. on the level of circulating eosinophils (" Thorn test "). Tests of this type are often convenient in practice but do not distinguish increased functional activity due to the transplant from that due to recovery of function in host tissue. Tests Based on Biopsy The simplest procedure is to remove a piece of the transplant and to examine it histologically. This test is of great value, but it may fail to distinguish between survival of a transplant and creeping replacement by host tissue. Secondly, an attempt may be made to grow the material obtained at biopsy in tissue culture. This test is rarely employed. Finally, the biopsy specimen may be transplanted back to the original donor. This is the most certain test of survival. It has been widely used by Medawar in studying experimental transplants of skin. CONDITIONS DETERMINING THE SURVIVAL OF TRANS- PLANTS It will be helpful to consider first conditions necessary for the survival of transplants in general, whether autologous or homologous. These are as follows: (1) The transplant must be alive at the time of transplantation. (2) Infection must be controlled. (3) The transplant must have an adequate supply of nutrient material and there must be adequate means for the removal of waste products. Transplants by vascular anastomosis have an assured blood supply ab initio; subsequently, however, thrombosis may occur and lead to death of the transplant. With free transplants metabolic exchange depends initially on diffusion of fluid to and from the surrounding tissue. Transplants of avascular tissues like cornea and cartilage may continue to be nourished in this way indefinitely and the same may be true of very small transplants of tissues which are normally vascular; larger free transplants, however, must sooner or later become vascularized if they are to survive. The extraordinary growth which occurs, as Hunter showed, when the spur of a cock is transplanted to its comb (Fig. 1) almost certainly depends on the abundant blood supply available in the new site. (4) In the special case of transplants of endocrine tissue survival is much more likely if, at the time of transplantation, the host is severely deficient in the endocrine in question. This fact was first reported by 175 M. F. A. WOODRUFF Halsted and is known as Halsted's rule. In the case of thyroid trans- plants it has been shown that it is not the thyroid deficiency per se which is important but the increased production of pituitary thyrotrophin which this deficiency evokes. It seems likely that a similar mechanism operates with adrenal transplants.

Fig. 1. The effect of an abundant blood supply on the growth of a transplant. Hunter's specimen (R.C.S. 1, 532) showing the spur of a cock transplanted to its comb. There are probably other conditions which have not yet been elucidated; nevertheless, if due regard is paid to those which we have enumerated, it is easy to make autotranspiants of a variety of normal tissues which survive and function throughout the life of the individual. The common clinical example is autotranspiantation of skin, but experimentally endo- crine tissues, whole kidneys and even whole lungs have been successfully transplanted, the last two by vascular anastomosis. In the case of bone large transplants undergo creeping replacement but small ones probably survive indefinitely. With homotranspiants the results are very different. Long term survival is unusual and often the transplant is destroyed rapidly. Typically a homotransplant closely resembles an autotransplant for a few days or weeks, during which time it may become vascularized, but subsequently it undergoes secondary destruction. The difference in the reactions evoked by autotransplants and homo- transplants is illustrated in Figures 2 and 3. Figure 2 is a section of an intramuscular autotransplant of thyroid in a guinea pig removed after seven months; it shows healthy thyroid tissue with very little surrounding 176 HUNTERIAN LECTURE

Fig. 2. Section (x 50) of thyroid autotransplant to abdominal wall of guinea pig (7 months in situ).

Fig. 3. Section (x45) of thyroid homotransplant to abdominal wall of guinea pig (6 weeks in situ). 177 14 M. F. A. WOODRUFF reaction. Figure 3 is a section of an intramuscular homotransplant of thyroid, also in a guinea pig, removed after only six weeks ; there is gross round cell infiltration and no recognisable thyroid tissue remains. Experi- ence with similar transplants indicates that it would have disappeared completely if left a few weeks longer. Both the recipient animals had been thyroidectomized prior to transplantation. In addition to provoking a reaction which brings about its own destruction, a homotransplant, especially a massive transplant or one made by parabiosis, may adversely affect the recipient. This is well illustrated by a case described by Gillies (1935) in which a parabiotic transplant of skin was made to a child from its mother. The transplant " took" and was thereupon severed from the mother but subsequently it suddenly became blue and at the same time the child developed a high temperature and appeared desperately ill. The transplant was removed and within an hour the condition of the child had greatly improved. In another case the donor became anaemic and the recipient polycy- thaemic before they were separated, apparently owing to the formation of an arterio-venous fistula. There are important exceptions to the rule that homotransplants are rapidly destroyed, viz.:- (1) Homotransplants between identical twins or between animals of a closely inbred strain behave like autotransplants and may survive indefinitely. (2) Homotransplants of certain tissues such as cartilage often survive for months or years. (3) Homotransplants to certain sites, notably the anterior chamber of the eye, may survive indefinitely. (4) The period of survival of a homotransplant may be increased by various experimental procedures. These will be discussed later. (5) Occasionally a homotransplant survives quite unexpectedly. It is conceivable that tissue groups exist comparable to the well known blood groups and that survival occurs when donor and host happen to belong to the same group. It must be emphasized, however, that blood group compatibility is not sufficient to ensure successful homotransplantation and that if tissue groups exist their number must be very large. In rabbits, for example, Medawar (1945) has calculated that the number of skin groups must be at least 127, and that they may be very much larger. Before leaving this subject it is worth noting that the earlier workers, including Hunter, failed to distinguish between homotransplants and autotransplants. There would seem to be several reasons for this:- (1) The fact that homotransplants often survive for a considerable time before being destroyed and occasionally survive indefinitely. (2) Lack of proper criteria of survival, and failure to distinguish between survival and replacement by host tissue. This is a prolific source of error with transplants of skin. 178 HUNTERIAN LECTURE (3) A fixed idea that " the living principle is the same in all animals." Hunter had the necessary facts but missed the correct interpretation. You may remember that he found that the spur of a cock failed to grow when transplanted to a hen; and that of a hen transplanted to a cock also apparently often failed, though if it did take it grew to the same size as the spur on the opposite leg of the recipient. It is perhaps comforting, when one has 'failed to draw the correct inference from a set of facts, to reflect that even the very elect have fallen into the same error. NATURE OF THE REACTION TO HOMOLOGOUS TISSUE Many theories have been propounded to explain the destruction of homotransplants but only one-the theory of actively acquired immunity -has a solid experimental foundation. This theory we owe largely to Medawar (1944, 1945). He showed that in both man and the rabbit second-set homotransplants (i.e., transplants made to an animal which had received one or more transplants from the same donor on a previous occasion) survived for a much shorter time than the original transplants. Medawar (1946) also showed that the period of survival of skin homotransplants in the rabbit was reduced if the recipient received previous intradermal injections of a suspension of leucocytes from the prospective donor. He postulated, therefore, that the destruction of skin homotransplants is the result of an actively acquired immunity and that, in the rabbit at any rate, there is an antigen common to leucocytes and to skin. Subsequent experiments with other tissues have helped to confirm the theory. The nature of the immunity to homologous tissue remains obscure. Search for circulating antibodies has, for the most part, proved fruit- less and it has therefore been suggested that homotransplant immunity is akin to tuberculin hypersensitivity. This, however, is a matter of speculation which we need not pursue here. My own experiments (Woodruff and Woodruff, 1950) with thyroid transplants, in addition to confirming Medawar's theory, have led me to formulate a further hypothesis which I have termed the hypothesis of the critical period. This has important surgical implications so I would like to describe the experiments on which it is based. These were all performed in guinea pigs. Free transplants of thyroid were used and the recipients were all thyroidectomized. It was first shown that homotransplants made to the anterior chamber of the eye, unlike subcutaneous homotransplants, commonly became vascularized and survived indefinitely. The fact that the transplants became vascularized is emphasized because Medawar (1948) found that skin homotransplants in the anterior chamber survived only if they remained avascular. The reason for this difference in the behaviour of transplants of skin and thyroid has not been elucidated. Secondly, it was found that, if a subcutaneous homotransplant from the same donor was made at the same time as, or a month preceding, a 179 14-2 M. F. A. WOODRUFF transplant to the anterior chamber, both transplants were destroyed. It was therefore concluded that a subcutaneous transplant is antigenic and that the state of immunity it induces extends to the anterior chamber of the eye. Finally, it was found that once a transplant had been established in the anterior chamber for several months it showed no ill-effects if the animal received a second transplant from the same donor subcutaneously. In this experiment the subcutaneous transplant was, as usual, rapidly destroyed; we may, therefore, reasonably assume that the recipient was effectively immunized. Why, then, was the transplant in the eye unaffected ? We are forced to conclude that, while a recent transplant to the anterior chamber is unable to survive in an immune animal, one that has become established for more than a certain " critical period" is no longer vulnerable. Does the hypothesis of the critical period hold good only in the special case of transplants to the anterior chamber or is it true for homotrans- plants in general ? At present no definite answer can be given. I claim only that the hypothesis is not incompatible with the known facts and that it is useful because it opens up new lines of attack on our problem. If the hypothesis is accepted it follows that permanent survival of a homo- transplant would be possible if some means could be found of (a) hastening the establishment of the transplant and thereby shortening the critical period, (b) delaying the development of immunity until the critical period has elapsed, or (c) protecting the transplant from immunological attack throughout this period. ATTEMPTS TO OBTAIN LONG-TERM SURVIVAL OF HOMO- TRANSPLANTS Most of the attempts to obtain long-term survival of homotransplants have been purely empirical. It is instructive, however, to consider the methods used in the light of the hypothesis just stated. They may be grouped under four headings (1) The use of special sites. (2) The use of neoplastic, embryonic or pre-treated tissue. (3) Reticulo-endothelial blockade, total body irradiation and adminis- tration of cortisone or A.C.T.H. (4) Administration of anti-histamine drugs. Transplantation to Special Sites We have already noted that homotransplants commonly survive in the anterior chamber of the eye. The reason for this is still uncertain. It might be supposed that transplants in the anterior chamber are not antigenic but in fact they do give rise to immunity since a transplant to one eye prevents a subsequent transplant to the opposite eye from taking. My own view is that the immunity which results from an anterior chamber transplant develops slowly so that the transplant becomes well established before the reaction to it reaches an effective 180 HUNTERIAN LECTURE level. This slow development of immunity may be associated with the fact that the anterior chamber has no lymphatic drainage; products of metabolism from the transplant are therefore absorbed into the venous system either via the aqueous or directly, and so are greatly diluted before coming in contact with cells of the reticulo-endothelial system. Support for this view comes from an experiment in which we found that the anterior chamber loses its favourable properties as a site for homo- transplants if it is provided with reticulo-endothelial tissue in the shape of an autotransplant of spleen. Next to the eye the white matter of the brain appears to be the most favourable site for homotransplants. Generally speaking, however, in this site transplants of thyroid, like transplants of skin, only survive if they remain unvascularized. Many other sites have been studied. In my own experiments free transplants have been made to subcutaneous and subfascial pockets, to muscles, joints, blood vessels, the testis, the ovary, and beneath the capsule of the kidney. In none of these sites, however, was permanent survival obtained except in a very small proportion of animals. Trans- plantation of organs by vascular anastomosis has been tried by a number of workers but, as Dempster (1950) and others have reported, while autotransplants may survive indefinitely, homotransplants are almost invariably rapidly destroyed. Transplantation of Neoplastic, Embryonic and Pre-treated Tissues In experimental animals homotransplants of tumour tissue, and probably also of embryonic tissue, survive more readily than homo- transplants of normal adult tissue. The reason for this is unknown but it may well be that neoplastic and embryonic transplants become established relatively rapidly, i.e., that the critical period is shorter than normal. There is also some evidence that tissue which has been cultured in vitro is more likely to survive than tissue transplanted direct from the donor. More work is required, however, to confirm this. Reticulo-endothelial Blockade, Total Body Irradiation and Administration of Cortisone and A.C.T.H. These procedures are grouped together because they have all been shown to prolong the survival of homotransplants under certain conditions and there is good evidence that they do this by delaying the development of immunity. Time will not permit a detailed discussion of all these procedures so we shall confine our attention to investigations with cortisone and A.C.T.H. About a year ago there were dramatic reports from the United States of the effect of these substances in prolonging the survival of homo- transplants of skin in man and permanent survival was claimed-in some cases (Whitelaw, 1951). Further work has failed to confirm these findings, and clinical opinion of the value of these substances as a means 181 M. F. A. WOODRUFF of obtaining long-term survival of homotransplants has swung from unreasoning optimism to profound pessimism (Ellison et al., 1951). How far this pessimism is justified remains to be seen. Animal experiments have not given rise to the same controversy, but they do show that the effects vary in different species. In the rabbit, for instance, Medawar and his associates (Billingham, Krohn and Medawar, 1951 (a) and (b)) found that cortisone, whether given systemic- ally or applied locally, significantly prolonged the survival of homo- transplants of skin. In guinea pigs, on the other hand, most workers have failed to demonstrate any effect, though Medawar has recently claimed that homotransplants can be made to survive longer if large doses of cortisone are given and the animals receive an adequate amount of ascorbic acid. My own experiments have been concerned mainly with the effect of cortisone on homotransplants of endocrine tissues. Transplants of thyroid have been studied in the guinea pig and transplants of adrenal in the rat. A special problem arises with endocrine tissues because administration of cortisone may inhibit the production of hormones (such as thyrotrophin and A.C.T.H.) which are necessary for the survival of both autotransplants and homotransplants in accordance with Halsted's principle. We have tried to overcome this by giving thyro- trophin or A.C.T.H. in addition to cortisone. Successful autotransplants can be obtained in this way but the survival of homotransplants has not been significantly prolonged. Clinical studies of the effect of cortisone on homotransplants in man will be described later. Administration of Anti-histamine Drugs It was suggested by Foster and Hanrahan in 1948 that histamine liberation might play a part in the destruction of homotransplants. On this assumption it should be possible to protect a transplant by adminis- tering one of the anti-histamine drugs. Foster and Hanrahan tried the effect of pyribenzamine after transplanting skin from a white man to a coloured woman and reported that the transplant still appeared healthy 90 days after the operation. The significance of this single case is uncertain; moreover the assump- tion behind the use of the drug lacks experimental proof and is hard to justify on theoretical grounds. Despite this it has seemed worth while to investigate the matter further. We have therefore studied the effect of one of the most potent anti-histamine drugs-phenergan-on trans- plants of skin and thyroid in guinea pigs. So far there has been no increase in the survival time of skin transplants but the experiments with thyroid are a little more promising. They will be reported in full at a later date. The foregoing discussion has been long and complicated. Let me sum up by saying that we are beginning to learn a little about the nature of the reaction to homologous tissue and to develop lines of attack on the 182 HUNTERIAN LECTURE problem of how to obtain homotransplants capable of surviving indefinitely. By using the anterior chamber of the eye the survival of small free transplants in experimental animals can often be assured. This may seem to be of academic interest only, but I think that the facts presented justify the belief that a more general solution of the problem will one day be found. SURGICAL APPLICATIONS SURVIVAL AND UTILITY So far we have been concerned mainly with the survival of homo- transplants. In discussing clinical applications, however, the primary consideration is utility If we are dealing with some permanent endocrine deficiency, or extensive and irreparable renal damage, only transplants capable of long- term survival are of value. In such cases the ideal to aim at is to provide at one operation a transplant (or a number of transplants) capable of surviving and functioning for the normal life span of a healthy individual of the same age as the patient. The qualification " at one operation" is important because if an individual has received one homotransplant another made subsequently, even from a different donor, is less likely to survive. As we have seen, this ideal is, as yet, far from being realised in practice. In other cases, however, a transplant may be of therapeutic value even though it is short-lived. In the first place it may tide a patient over a critical period; this, as we shall see later, applies particularly to homo- transplants of skin. Secondly the transplant may provide a temporary but effective framework for the growth of host tissue. This applies to transplants of bone, blood vessels and probably also of cornea. SOURCES OF MATERIAL FOR HOMOTRANSPLANTS IN CLINICAL PRACTICE It is often very difficult to obtain suitable material for homotransplants in clinical practice. The possible sources are voluntary donors, material removed in the ordinary course of surgical operations, and material obtained at autopsy. Voluntary Donors Hunter, you will remember, transplanted teeth and apparently had no difficulty in obtaining donors for a suitable consideration. Judging by Rawlinson's picture* they certainly earned their pay. Times have changed and one can hardly look for professional donors in the welfare state. It is, however, reasonable to call for volunteers from among a patient's relatives, and perhaps also from the general public, to supply limited quantities of skin for homotransplantation. In special circumstances other tissues might possibly be obtained. * In the possession of the College. A reproduction will be found in the Annals of February, 1949. 183 M. F. A. WOODRUFF Recently, for instance, I saw a girl with total loss of ovarian function and her mother was anxious to donate an ovary for transplantation. In our present state of knowledge it would have been wrong to accept this offer but the fact that it was made in good faith encouraged the view that public support will be obtained once the technical problems have been solved. Material from a voluntary donor, if available, has two great advantages: it consists of normal healthy tissue and the risk of bacterial contamination can be reduced to a minimum. Material Obtained at Operation Material removed in the ordinary course of surgical operations is usually pathological and is then useful for transplantation only in rare cases. The best example is Broster's use of hyperplastic adrenal cortical tissue from patients with virilism for the treatment of Addison's disease. When, however, normal tissue is removed at operation, as for example when ribs are removed in the operation of thoracoplasty, it may be of great value. Like material from voluntary donors it can readily be obtained fresh, and free from bacterial contamination. Occasionally foetal tissue can be obtained at operation, for example, when pregnancy has to be terminated by hysterotomy. The use of foetal adrenal tissue in the treatment of Addison's disease will be described later. Material Obtained at Autopsy Autopsy material offers a wide range of tissues and organs but is useful only if removed aseptically and shortly after death. The safe interval depends on the cause of death and the nature of the tissue; it probably never exceeds five hours and for some tissues may be very much less, possibly under an hour. The availability of autopsy material can be increased only by legislation. All interested in homotransplantation must be deeply grateful to the ophthalmic surgeons for bringing this matter before the notice of the public and the government, and also to the President of the College for his active and powerful support in this campaign. May I venture to express the hope that if amending legislation is introduced it will make provision for donation of any type of tissue and not only of cornea ? Selection of Donors There are two important considerations which govern the choice of a donor. In the first place stringent precautions must be taken to avoid the transmission of communicable disease. The donor must therefore be healthy and show no sign of infection. When foetal tissues are used the umbilical cord should be pulsating when the foetus is delivered. A Wassermann test should be done in all cases, either on the donor or, when foetal tissue is to be used, on the mother. In tropical countries enquiry should be made about recent fevers and the blood should be examined 184 HUNTERIAN LECTURE for malaria parasites. Certain additional precautions may be necessary before accepting bone for transplantation. Secondly the donor selected should be the one most suitable for the prospective recipient. The ideal, of course, is to use an identical twin. Apart from this we have at present no certain way of choosing the best donor though it seems reasonable, when possible, to use a near relative. The age of the donor appears to be important and whenever possible one under the age of 30 should be chosen. Is blood grouping of any assistance ? If the question refers only to the ABO system the answer is " no." If, however, it embraces in addition all the refinements of Rh grouping the answer is " no-one knows." The matter would seem, therefore, to merit careful investigation. The idea of making a small test transplant, for example of skin, is attractive but is contra-indicated because of the risk of immunising the recipient and so increasing his resistance to the transplant proper. From a practical point of view it is worth noting that should a satis- factory scheme of " matching" be devised it may be easier to choose a recipient to suit a particular donor rather than vice versa. This is likely if we are using homotransplants for the treatment of some chronic and relatively common condition such as Addison's disease. STORAGE OF TRANSPLANTS Even if all the problems discussed so far could be solved the surgical applications of homologous tissue transplantation would be severely restricted if only fresh material could be used. The pioneer work on methods of preserving living tissues was under- taken by Alexis Carrel (1912) and the methods in use today are only modifications of those which he described. These methods are:- 1. Storage in a plasma-electrolyte medium. 2. Freezing * (including nowadays " deep freezing " at very low temperatures). 3. Continuous perfusion. Interest today centres largely on methods for storing bone, skin and segments of blood vessels, though some work has been done on the preservation of cornea, endocrine tissues and whole kidneys. Time will not permit of a detailed description of the methods used. When all that is needed is a framework for the growth of host tissue, satisfactory results can sometimes be obtained by using dead tissue. Homologous bone which has been stored in merthiolate appears to be almost if not quite as useful as living homologous bone and there is evidence that arterial " transplants " need not be alive to be effective. The word transplants is placed in inverted commas because it is open to question whether this term should be extended to include dead material. * Since this lecture was delivered my attention has been drawn to the fact that Hunter himself suggested freezing as a method of storage (Palmer's edition of Hunter's works, vol. 1, page 284). 185 M. F. A. WOODRUFF THE PRESENT STATUS OF HOMOLOGOUS TISSUE TRANS- PLANTATION IN SURGERY Cornea Transplantation of cornea is an established clinical procedure. Up to March, 1950, the New York eye bank, for example, had supplied over 1,200 corneas for use as transplants. The operation gives a good functional result in many cases. The indications for corneal transplantation and the technical details of the various types of operation may legitimately be left to the ophthalmic surgeon, but we cannot ignore the question " Why are corneal transplants successful ? " Various answers have been suggested. It has been said that cornea survives because it is an avascular tissue, because it is non-antigenic, because it is protected by the muco-polysaccharide which it contains, or because of the relationship of the transplant to the anterior chamber. Personally, however, I accept the view of Herbert Katzin (1950), director of the laboratories of the New York eye bank, who claims that most of the transplant, including the epithelium, the stromal cells and probably the endothelium, is gradually replaced by host tissue. On this view the success of the operation does not depend on survival of the transplant but on whether or not replacement by host tissue occurs in an orderly manner and without accompanying vascularisation. Skin Despite claims to the contrary homotransplants of skin rarely if ever survive permanently in man. They often take and survive for periods varying from 10 days to six or eight weeks and this temporary survival, combined with ingrowth of host epithelium from the edges of the defect, has often been mistaken for permanent survival of the transplant. Nevertheless homotransplants of skin are sometimes of great clinical value in dealing with extensive areas of skin loss. By using alternate strips of autologous and homologous skin, as advocated by Mowlem, large defects may be covered at one operation, and if the homotransplants survive for, say, four to six weeks they can be replaced by fresh auto- transplants cropped from the original donor areas. In the meantime the patient's general condition has had time to improve, infection has been kept under control and the formation of scar tissue reduced to a minimum. We may therefore say that, while permanent survival is still the ideal to be aimed at, it is worth striving to attain a more limited objective, namely the discovery of some method by which survival for at least four weeks could be assured in every case. This problem is being tackled in three ways: 1. By trying to find a relationship between the period of survival of a transplant and the blood groups (ABO and Rh systems) of donor and recipient. 186 HUNTERIAN LECTURE 2. By using multiple donors. 3. By local application of cortisone to the transplant. Blood grouping in relation to transplantation has already been discussed, but the other procedures must now be considered. The rationale of using multiple donors rests on the following two assumptions which Medawar has shown to be true in the rabbit and which probably hold good also in man: (1) The speed with which immunity develops depends on the quantity of skin homotransplanted so that, other things being equal, a small transplant survives longer than a large one. (2) While a homotransplant usually renders the recipient to some extent resistant to homplogous skin in general, the resistance to skin from other donors is less marked than that to skin from the original donor. It follows that survival is likely to be improved if the quantity of skin needed is made up from several donors instead of being taken from a single individual. Dempster and Lennox (1951) have reported encouraging results with multiple donors in rabbit, and Saunders and Moore (1950) have used the method clinically. Local application of cortisone was shown by Medawar (1951) (b) to prolong the survival of skin homotransplants in rabbits, and I have recently used this method in four clinical cases. I should like to describe one of these cases in detail because it illustrates the value of homo- transplantation when one is confronted with a large skin defect. The patient, a boy aged 9, was run over and dragged behind a bus. He sustained a penetrating wound of the left knee joint and loss of skin and subcutaneous tissue extending from the left groin to 3 inches below the knee, complete except for a strip down the back of the thigh. The total defect was estimated at about 100 sq. ins. After resuscitation, including blood transfusion (900 ccs.), debridement was performed and treatment with penicillin and chloromycetin was begun. Seven days after the accident the surface was clean and ready for grafting, except for a small area at the knee where a sinus was present. Split-skin grafts were cut with a dermatome, applied in strips about 11 ins. wide, and sutured at the edges. Two strips, each 6 ins. x j12 ins., were homologous skin from the patient's uncle, and the remainder were autologous. The homotransplants and one of the autotransplants were treated with a saline suspension of cortisone acetate (25 mg. per cc.); 2 ccs. was used to cover the raw surface of the transplants; it was applied with a syringe and needle and spread evenly with a small brush. A further 2 ccs. was applied to the outer surface of the transplants after they were in place (Fig. 4). Subsequently every three days the dressings were carefully removed and a further 2 ccs. of cortisone suspension was applied. Thus, for every square inch of " treated transplant " approximately 4 mgms. of cortisone acetate was used at the initial operation and 2 mgms. every three days thereafter. The transplants took well (95 per cent.) and after 187 M. F. A. WOODRUFF six days all showed evidence of vascularization. The homotransplants and autotransplants were indistinguishable except for the fact that the former had inadvertently been cut a little thinner. After 21 days a biopsy was performed; the tissue removed included pieces of auto- transplant and homotransplant with the boundary between them. The transplants were still indistinguishable on inspection but the biopsy showed some differences. The epidermis of the homotransplant was as well preserved as that of the autotransplant but sweat glands and hair follicles were present only in the latter. The corium of the homo- transplant was replaced by granulation tissue showing a moderately abundant cellular infiltration, mainly mononuclear but including some eosinophils; the corium of the autotransplant, on the other hand, was well preserved and cellular infiltration was slight. The junctional zone was closed by newly-formed epidermis some eight cells thick. After 30 days the homotransplants appeared rather redder than the autotrans- plants but were still intact. The patient had developed chicken pox three days previously and it was observed that two pocks were present on the autotransplants but none on the homotransplants. Biopsy at this stage showed a gap between the epidermis ofhomotransplant and autotransplant with a well-defined line ofcleavage, marked by abundant mononuclear infil- tration, extending down into the subcutaneous tissues. There was also some mononuclear infiltration in both epidermis and corium of the homo- transplant and the nuclei of some of the epidermal cells were pyknotic. At the next dressing the homotransplants were moist and desquamating; 42 days after operation they had completely broken down leaving raw granulating areas. Epithelialisation of these areas from the adjacent autotransplants had begun. A furacin dressing was applied; three days later the raw areas were distinctly smaller and what remained of them was covered with fresh autotransplants cut from one of the original donor areas. These took promptly and but for his associated suppurative arthritis and osteitis the patient would soon have been back at school. In the other patients the defects were smaller and could easily have been completely covered with autotransplants. Sufficient skin for this purpose was cut with a dermatome but instead of applying all of it a small piece (1, 2 or 4 sq. ins.) was stored in the refrigerator for future use and the corresponding raw area was covered with a split-skin homotransplant. In each case cortisone was applied, in the manner already described, to the homotransplant and to an autotransplant of the same size. The results were disappointing. Despite a good take of the untreated auto- transplants, the autotransplants treated with cortisone and the homo- transplants failed to take in two patients; in the third patient the treated autotransplant took and survived but the homotransplant broke down after 24 days. It would be unwise to draw any conclusion about the value of local application of cortisone from these four cases. It is conceivable that the successful result in the first patient might have been obtained without 188 HUNTERIAN LECTURE

Fig. 4. Local application of cortisone to a homotransplant of skin. using cortisone. On the other hand two of the subsequent failures might be ascribed to technical errors since the cortisone-treated auto- transplants fared as badly as the homotransplants. It cannot but be hazardous to remove the dressings three days after skin-grafting, and the danger is increased when cortisone is used because this drug interferes with the process by which a transplant becomes fixed to the underlying granulation tissue. Further investigation is therefore necessary and some means must be found of applying the drug without risk of detaching the transplants. In these experiments no attempt was made to match donor and host but the blood groups (ABO and Rh) were determined. In addition a record was kept of blood transfusions given to the recipients of homo- transplants. As we have seen a rabbit may be immunised against homologous skin by injections of leucocytes from the prospective donor, and probably to a lesser extent by leucocytes from other donors. If this applies also in man the survival of a skin homotransplant might conceivably be prejudiced by previous blood transfusion. Cartilage Homotransplants of cartilage, in both man and animals, behave in much the same way as autotransplants. A slightly greater reaction occurs with homotransplants but despite this they usually persist for many years. Like autotransplants, however, they are likely to be destroyed if infection occurs. As an alternative to fresh material dead 189 M. F. A. WOODRUFF cartilage preserved in alcohol (Peer, 1939) or merthiolate (Straith and Slaughter, 1941) may be used. Mowlem (1941) has stressed the value of cartilage homotransplants for reconstruction of the pinna in cases of congenital deformity; they may be used with equal success in many other plastic operations. When we reflect that removal of autologous costal cartilage is by no means a trivial procedure and carries an appreciable morbidity it is surprising that homologous cartilage is not used more extensively. Bone Healthy bone is removed and wasted in many orthopaedic operations. On the other hand the use of autotransplants in the treatment of ununited fractures and so on means a longer operation and may itself cause com- plications' It is not surprising, therefore, that interest in the use of homotransplants has steadily increased. Macewan (1879) appears to have been the first to use homologous bone in man. Others followed his lead but homotransplants were not widely used until bone banks began to be established in the United States about the end of the second world war. The fate of bone transplants, both autologous and homolo- gous, has aroused much controversy. I think it may now be taken as established, however, that, while small autotransplants may survive, homotransplants and massive autotransplants act essentially as scaffolding and local deposits of calcium, and are gradually replaced by host tissue. Discussion to-day is mainly concerned with methods of storage. Refrigeration after immersion of the bone in citrated blood (Inclan, 1942), deep freezing (Wilson, 1947; Bush and Garber, 1948; Converse and Campbell, 1950) and preservation in merthiolate (Reynolds and Oliver, 1949) all have their advocates. Some of the claims have been exaggerated but it is probably true to say that homologous bone stored in a deep freeze or preserved in merthiolate, if used in the form of small chip grafts, is nearly as good as fresh autologous bone for the treatment of ununited fractures, for arthrodesis of joints including spinal fusion, and for filling cavities after removal of bone cysts. Massive homotransplants, however, appear to be decidedly inferior to autotransplants (Weaver, 1949). Blood Vessels The pioneer work of Carrel (1905, 1907, 1908) and Guthrie (1912) demonstrated the practicability of replacing excised segments of vessels by homologous arterial and venous transplants. Carrel also did some work on the storage of such transplants but insufficient progress in this direction, combined with the difficulty of obtaining fresh homologous material, delayed the clinical application of this knowledge. During the last seven or eight years interest in this field has revived. New experiments in dogs have shown that satisfactory results may be obtained with transplants preserved in a plasma-electrolyte medium (Gross, et al., 1949) or frozen at low temperatures (Deterling, Coleman 190 HUNTERIAN LECTURE and Parshley, 1950; Hufnagel and Eastcott, 1951). In man homo- transplants preserved in one or other of these ways have been used in the Blalock-Taussig type of operation when straightforward anastomosis was impossible without undue tension (Gross, et al., 1949) and in the treatment of coarctation of the aorta (Fig. 5) when the length of segment involved was too great for repair by end-to-end anastomosis. Gross (1950, 1951) has reported patients alive and well several years after this operation. Homotransplants have also been used in the treatment of peripheral arterial disease; Eastcott (1952) for instance replaced a throm- bosed segment of the popliteal artery with a transplant 8 cms. in length. Kidney Dempster (1950) has reviewed the experimental work on transplantation of the kidney by vascular anastomosis and has carried out important researches himself. Broadly speaking in dogs a kidney may survive indefinitely after autotransplantation to the neck with anastomosis of the renal artery to the carotid and the renal vein to the jugular. The kidney, however, does not concentrate urine properly in its new situation. After homotransplantation the kidney is destroyed within a few days and the recipient animal may become acutely ill even though its own kidneys have not been removed. At present, therefore, homotransplantation of a kidney in man would seem likely to prove futile and possibly disastrous, yet a successful case was recently reported by Lawler and his associates (1950). The patient, a woman of 44, had polycystic kidneys and the left kidney was removed and replaced by a homologous kidney removed immediately after -leath. The patient survived and as far as I know is still alive and well. An indigo-carmine test 52 days after the operation indicated good function in the transplanted kidney. Donor and recipient belonged to the same blood group and both were Rh negative but that alone would not seem sufficient to explain this astounding result. Suprarenal Gland In 1946 Broster removed one suprarenal gland from a girl suffering from the adrenogenital syndrome and transplanted it to a patient with Addison's disease. The recipient's inferior epigastric artery and vein were exposed deep to the rectus muscle, divided and threaded into the suprarenal vein of the transplant. Great clinical improvement resulted and the procedure has been repeated equally successfully with other patients. These results are hard to explain. For reasons which will become more apparent in a moment, however, I venture to hope that Mr. Broster will one day perform biopsies on these patients. Recently, in collaboration with medical and obstetrical colleagues, I have made transplants of foetal suprarenal to four cases of Addison's disease. The material was obtained when pregnancy was terminated by hysterotomy about the 20th week. It was cut into small fragments 191 M. F. A. WOODRUFF

Fig. 5. Coarctation of the aorta treated by an arterial homotransplant. (Dr. Robert E. Gross's case.) A.A., aortic arch. L.S.A., Left subclavian artery. G., Graft. The graft was 5 cm. in length. and inserted into the rectus sheath of the recipient under local anaesthesia. Cortisone was given for four weeks in doses ranging from 20 to 100 mgms. daily in the hope of delaying the development of immunity; in addition A.C.T.H. (20 mgms. twice or thrice daily) was given for five weeks for reasons explained earlier when we were discussing experimental endo- crine transplants. Thorn tests (Thorn, et al., 1948) were performed before, and at intervals after, transplantation. The transplants were made 13, 12, 11 and 5 months ago respectively. All the patients have shown striking clinical improvement and this has been maintained. All were due for re-implantation of D.O.C.A. at the time of operation but none received an implant then or subsequently. The Thorn tests, however, showed only temporary improvement and biopsy, which has so far been performed in three cases 6 to 9 months after operation, has revealed no trace of the transplants. In face of the negative biopsy findings the clinical improvement remains a mystery. One suggestion is that the patient's own suprarenals, or what remained of them, have been reactivated either by the A.C.T.H. admin- istered or by substances absorbed from the transplants; this, however, is no more than speculation. FUTURE PROSPECTS Homotransplants of cornea, cartilage, bone and blood vessels are of proved value and are likely to be used more and more as time goes on. The same is true to a more limited extent of homotransplants of skin. 192 HUNTERIAN LECTURE What shall we say of the prospects of obtaining permanent survival of homotransplants of skin, of kidney and of endocrine tissues ? The problem to be solved is complex and difficult, but personally I believe that it will one day be solved. Lest this optimism seems fatuous let me end by quoting the words of a distinguished American surgeon, Dr. Harvey B. Stone. Discussing this problem and the search for a solution in his presidential address to the American Surgical Association he said: "Perhaps such a purpose to-day may seem visionary, but let us not forget that often in the story of mankind the visionary of to-day has proved in some distant tomorrow to be the man of vision." ACKNOWLEDGMENTS My thanks are due to Dr. Alexander Lyall, Dr..James Walker, Dr. Joan Burrell, Professor J. S. Young and Mr. F. L. F. Innes, who have collaborated with me in some of the clinical investigations, and to my wife and Miss T. M. Boswell, who have assisted with the experimental work. I am also indebted to Messrs. Merck & Co. for a generous gift of cortisone and to the Medical Research Council for supplies of A.C.T.H. and for financial assistance. Fig. 1 was made available by Professor Hadfield and is reproduced by permission of the Council of the College; Figs. 2 and 3 are from the article in the Philosophical Transactions referred to below and are reproduced by permission of the Royal Society. Fig. 5 is reproduced from Circulation by kind permission of Dr. Robert E. Gross and Grune & Stratton, Inc. The quotation from Dr. Harvey B. Stone's address is from Annals of Surgery and is included by permission of Dr. Stone and J. B. Lippincott Co. REFERENCES BILLINGHAM, R. E., KROHN, P. L. and MEDAWAR, P. B. (1951) (a) Brit. Med. J. 1, 1157. (1951) (b) Ibid. 2, 1049. BROSTER, L. R. and GARDINER HILL, H. (1946) Brit. Med. J. 2, 570. BUSH, L. F. and GARBER, C. Z. (1948) J. Amer. Med. Ass. 137, 588. CARREL, A. (1905) Am. Med. 10, 284. (1907) Bull. Johns. Hopk. Hosp. 18, 18. (1908) Proc. Phil. Soc. 47, 677. (1912) J. Amer. Med. Ass. 59, 523. CONVERSE, J. M. and CAMPBELL, R. M. (1950) Plast. & Reconstr. Surg. 5, 258. DEMPSTER, W. J. (1950) Ann. Roy. Coll. Surg. Engl. 7, 275. and LENNOX, B. (1951) Brit. J. Plastic Surg. 4, 81. DETERLING, R. A., COLEMAN, C. C. and PARSHLEY, M. (1950) New York Med. 5th July, 1950. EASTcOTT, H. H. G. (1952) Proc. Roy. Soc. Med. 45, 152. ELLISON, E. H., MARTIN, B. C., WILLIAMS, R. D., CLATWORTHY, H. W., HAMWI, G. and.ZoLLINGER, R. M. (1951) Ann. Surg. 134, 495. FOSTER, D. G. and HANRAHAN, E. M. (1948) Bull. Johns. Hopk. Hosp. 82, 501. GILLIES, H. D. (1935) Northwestern Univ. Bull. 35, 1. GROSS, R. E., BILL, A. H. and PEIRCE, E. C. (1949) Surg. Gynaec. Obstet. 88, 689. (1950) Circulation 1, 41. (1951) Ann. Surg. 134, 753. GuTHlUE, C. C. (1912) Blood Vessel Surgery. Longman & Co., New York. HUFNAGEL, C. A. and EASTCOTT, H. G. (1951) Bull. Georgetown Univ. Medical Center, 4, 119. HUNTER, JOHN (1835) Collected Works, edited by J. F. Palmer. Longman & Co., London. INCLAN, A. (1942) J. Bone Jt. Surg. 24, 81. KATZIN, H. M. (1950) Amer. J. Ophthal. 33, No. 3, pt. 2, 35. LAWLER, R. H., WEST, J. W., MCNULTY, P. H., CLANCY, E. J. and MURPHY, R. P. (1950) J. Amer. Med. Ass. 144, 844. MACEWAN, W. (1879) See The Growth ofBone, Maclehose, Glasgow, 1912, p. 176-187. MEDAWAR, P. B. (1944) J. Anat. Lond. 78, 176. (1945) Ibid. 79, 157. (1946) Nature 157, 161. (1948) Brit. J. Exper. Path. 29, 58. MOWLEM, R. (1941) Brit. J. Surg. 29, 182 193 15 M. F. A. WOODRUFF PEER, L. A. (1939) Surg. Gynaec. Obstet. 68, 603. REYNOLDS, F. C. and OLIVER, D. R. (1949) J. Bone Jt. Surg. 31A, 792. SANDERS, G. B. and MOORE, R. H. (1950) Amer. J. Surg. 80, 637. STONE, H. B. (1942) Ann. Surg. 115, 883. STRAITH, C. L. aind SLAUGHTER, W. B. (1941) J. Amer. Med. Ass. 116, 2008. THORN, G. W., FORSHAM, P. H., PRUNTY, F. T. G. and HILLS, A. G. (1948) J. Amer. Med. Ass. 137, 1005. WEAVER, J. B. (1949) J. Bone Jt. Surg. 31A, 778. WHITELAW, M. J. (1951) J. Amer. Med. Ass. 145, 85. WILSON, P. D. (1947) Ann. Surg. 126, 932. WOODRUFF, M. F. A. and WOODRUFF, H. G. (1950) Phil. Trans. B. 234, 559

RESTORATION AND REBUILDING OF THE COLLEGE THE PHOTOGRAPH THIS month is a view across the centre of the site looking southwards. On the right, behind the tops of the two ladders, can be seen the wall of No. 38, Lincoln's Inn Fields. This house is now being used by the College for offices and lecture rooms, but in the next phase of the proposed building programme it will be demolished to allow the Nuffield College of Surgical Sciences to adjoin the existing main College building. At the top centre is a temporary timber gantry to give access from Portugal Street for building materials. The platform which can just be seen is at road level.

On the left of the gantry can be seen the reinforced concrete retaining wall with the mild steel rods protruding along its top edge. These form the reinforcement and in due course will be buried in concrete as the work proceeds and the height of the wall is increased. On the right of the gantry is the asphalte face of the outer wall, as was shown in one of last month's photographs. The reinforced concrete 194