874 BRIT. J. SURG., 1966, Vol. 53, No. 10, OCTOBER

the remaining 5 it was not possible to establish a reliable history of previous infection, while in 3 of these men there appeared to be convincing evidence of an acute attack of pain during strain, followed by a tender swelling in the scrotum.

One important feature of all these 11 men is that they were not seen in hospital for a varying time after the initial onset of the pain and swelling, so that we have no reliable clinical information. None of them had the typical acute fulminating appearance of the usual Esch. coli epididymitis with marked systemic disturbance, nor according to the general practitioner was this picture ever present. They merely had a moderately swollen tender epididymis which took some weeks to subside. In 5 of the men the condition had clinically subsided before they were seen by me and these are I think most inter- esting : they were all claiming industrial injury benefit and because an amicable agreement could not be reached I was asked to see them as a referee.

One case is particularly interesting. Two men were moving a heavy piece of machinery when one of them (aged 44 years) complained of sudden groin pain and could not continue. After an hour or so he was sent home. The evidence we have in writing several months later is: (I) A signed statement by his workmate describing the sudden onset of pain, the patient’s inability to continue work, and his being sent home; (2) a diagnosis of ‘ epididymo-orchitis’ by his doctor on his certificate; and (3) a few weeks later photostat notes from a hospital casualty depart- ment about the development of chronic epididymitis, the finding of a sterile urine, and treatment with a suspensory bandage and other standard measures. The man was off work for 4 weeks and when I saw him 3 months later no abnormal clinical signs remained, but he was still complaining of severe testicular pain. So far there is no evidence of infec- tion, but an examination of the man’s National Health Service card revealed a reference 7 years previously to ‘cystitis’, with no other comment, and a further reference 4 years previously to ‘prostatitis ’,

again with no further comment. These two incidents did not involve the man in any sick leave. On the evidence available it is extremely difficult to decide whether the acute inflammation was directly ‘ attribut- able to’ the strain at work or whether the previous latent infection was ‘aggravated by’ the incident. The figures from the Ministry of Pensions and National Insurance reveal the magnitude of this problem. During 1963 and 1964 approximately 13,600 claims were made for sickness benefit for ‘ epididymo-orchitis ’. This includes those who, thought to have been incapacitated, did not claim that the condition was due to their work or else had had such claims disallowed. During the same period I 80 men claimed successfully under the Accident Provisions and received industrial injury benefit. In other words, it was agreed that the epididymo- orchitis was due to injury at work; unfortunately the records do not indicate whether the injury was direct trauma or strain, while there are no records of the number of unsuccessful claims.

Most of these claims are dealt with locally by Regional Medical Officers, but in 1964 and 1965 16 cases were referred through to the London Head- quarters owing to a conflict of opinion. In several of these cases where the Industrial Insurance Com- missioner had sought expert medical opinion, the reflux theory has been expounded and accepted.

Any retrospective investigation of this problem is bedevilled by the fact that the description of the clinical findings are valueless in most cases. For example, in one of the patients referred to me the subsequent development of testicular atrophy almost certainly indicated that the original acute lesion was a torsion or even mumps, but certainly not an infec- tive epididymitis. It is therefore obvious that a prospective investigation is essential if surgeons are to be able to decide whether or not a strain or violent exercise can be responsible for an epididymitis in the absence of any previous infection or even whether such a strain can flare up an old infection or not.

SHORT PAPERS FOR THE MOYNIHAN PRIZE [The prize was won by Mr. R. Shields, Department of Surgery, Welsh National School of Medicine.

THE RESPONSE OF THE RETICULO-ENDOTHELIAL SYSTEM TO A CANCER BY ALAN EDWARDS

SURGICAL PROFESSORIAL UNIT, ST. BARTHOLOMEW’S HOSPITAL, LONDON

IN 1943 Gross first demonstrated active immunization of inbred mice to transplants of carcinogen-induced sarcomata in an isologous strain. It is generally con- sidered, however, that the first clear demonstration of tumour specific antigens in experimentally induced tumours in animals was made by Foley in 1953. Since

then there has been an increasing tide of evidence that indicates specific antigenicity in various classes of animal tumours (Old and Boyes, 1964). In 1955 Graham and Graham found complement-fixing anti- bodies in the serum of 12 patients of a group of 48 with gynaecological cancers, and once again there has

EDWARDS : RESPONSE OF RETICULO-ENDOTHELIAL SYSTEM T O CANCER 875

followed a mounting volume of evidence that human tumours also exhibit specific antigens. Indeed Gorodilova, Silina, and Saraeva (1965) maintain that it is ‘easy’ to detect complement-fixing antibodies in advanced cancer of the breast. Thus there poses an ‘ immunological paradox’ (Haddow, 1965), for how can a tumour flourish on its host when other foreign tissue, such as a skin homograft, are rejected ? It is

SP- t 4 LG.-+ FIG. I.-Plan of the gravimetric experiments. T h e axillary

lymph-glands (L.G.), thymus (T.), . and spleen (SP.) were removed from a DBAlzI mouse bearinn a Ca.D.2 tumour ( too &hr)b; means oFa dissecting microscope ( t o p left) via wet box& (middle le j t ) , and.weighed in a saturated atmosphere (bqzzom left). Significant thymic atrophy and splenomegaly were achieved, but the lymph-glands remained unchanged (arrows bottom right).

1 . 9 0 NORMAL SPLEENS

z 20 ’ O l

1 198.2290.4 MG. t 115 CANCEROUS SPLEENS

FIG. 3.-Histogram comparing normal spleen weights at death in 20-mg. groups with cancerou3 spleen weight, showing signifi- cant splenomegaly. Means are shown with standard deviation.

clearly related to the function of the reticulo- endothelial system (R.E.S.), by which is intended Metchnikoff’s (1905) defensive system rather than the more classic phagocytosis-based concept of Aschoff (1924).

EXPERIMENTAL PLAN Following Foley’s (1953) pioneer example, a simple

model was set up to study this problem on the laboratory bench, using the DBA/2J strain of inbred mice and an implanted, but originally spontaneous, adenocarcinoma of the breast, the Ca.D.2. This

tumour was used because it evoked a good blood- supply and was of uniform cellular structure. The isogenicity of the whole system was constantly monitored by full-thickness skin-graft exchange.

Three organs were arbitrarily selected to represent the R.E.S., viz., lymph-glands, thymus, and spleen, and three parameters were studied, the weight, the histology, and the function as assessed by stimulation

30 NORMAL THYMI I 4

2. - z t I I c 10 20 30 40 50 6 0 70

WE‘ICHT IN I ~ C .

P .CO.OOl ( t g8= 21.5)

10

FIG. 2.-Histogram (abscissa, weight of thymi at death in I-mg. integers; ordinate, number of thymi) comparing 30 normal with 70 cancerous thymi, showing significant thymic atrophy. Means are shown with standard deviation.

y 11.5: 4.2 4- MG. 80 SETS OF

WEIGHT

IN MG.

z 4 .

FIG. 4.-Histogram comparing normal axillary lymph-giand weights at death with cancerous glands and showing no difference. Means are shown with standard deviation.

by vaccination procedures. Axillary lymph-glands were studied in the belief that they probably mirrored the response of all the lymph-glands and in the certainty that they represented the regional lymph- glands of a tumour growing subcutaneously on the side of the thorax. During routine post-mortem examinations an impression was obtained of lymph- gland and thymic atrophy with splenomegaly in mice dying from tumour. These are, of course, the features of Billingham and Brent’s (1957) ‘runt’ disease, a condition brought about by the destruction of an animal’s R.E.S. by homografted lymphocytes.

876 BRIT. J. SURG., 1966, Vol. 53, No. 10, OCTOBER

WEIGHT CHANGES OF R.E.S. WITH TUMOUR

This impression was then tested by removing, with the aid of a dissecting microscope, the axillary lymph-glands, thymus, and spleen from a group of animals that had died of cancer, and comparing them with a control series of normal mice (Fig. I). Prior experience with intravital staining had shown that

- LYMPH-GLANDS

.4 !i -.-.MYWS

......... SPLEEN + 10

-, T. x.

0 0 2 I 6 8 10 12 14 16 18 20 22 21 26 18 30 32 34

DAYS AFTER 'NMOUR IMPLAN7

FIG. S.-Weight of organs of tumour-bearing mice with time after tumour implantation. Daily measurement. Each point the mean of 5 animals.

I \-- s

P I 0 2 4 6 I I" 12 I. 16 $8 20 21 2 1 26 I 8 30 ,I z4

LI, b I X ,<*TION Ih "*IS

FIG. 7.-Weight of axillary lymph-glands with various stimu- lation with time. Each point is the mean of 3 animals except tumour (N.G.) which is the mean of 5 .

the DBA/zJ axilla was anatomically constant and contained only two lymph-glands. Desiccation of the small quantities of wet tissue involved was avoided by the use of 'wet boxes' and by weighing in a saturated atmosphere. Figs. 2-4 represent the results and show that, while there was significant thymic atrophy and splenomegaly, the lymph-glands

at death were not significantly different from the control series.

I t was then suspected that the measurement of these organs terminally at death might merely be showing the end-result of a dynamic process. Accordingly a group of ZOO mice was implanted with tumour and aliquot groups of 5 sacrificed each day throughout the evolution of the tumour, and their

* / * THYMUS ._._._._.-. --- ............ .......

'-.SPLEEN +10

LYMPH- **.

LIVER + 100

3\ i ii i 3 is i7 is ii i 3 i5 DAYS AFTER TulvlouR IMPLANT

FIG. 6.-Weight of organs after the excision of tumour. Each point the mean of 3 animals.

" I 0 2 4 6 8 10 I? Ik 16 18 20 22 ZI 26 28 30 32 31

LIFE DUR*IION IN DAYS

FIG. 8.-Weight of spleen with various stimulation with time. Each point is the mean of 3 anunals except the tumour group (N.G.) which is the mean of 5 .

organs removed and weighed (as in all these experi- ments organs were submitted to histology as a check of dissection) and the means plotted graphically. Fig. 5 shows the results. The thymus atrophied pro- gressively with a point of inflexion at 7-13 days. Spleen hypertrophied until the seventeenth day and lymph-glands until the twelfth day before terminal

EDWAKDS : RESPONSE OF RETICULO-ENDOTHELIAL SYSTEM T O CANCER 877

involution. The liver changed very little. I t was then apparent that measurement at death, or for that matter at any single time, was in no way indicative of what goes on during the disease process.

Because of considerable change in fluid balance of tumour-bearing mice (their plasma volumes increased nearly fivefold as measured by Evans’s blue), the protein content of the lymph-glands, thymus, and spleen of tumour-bearing mice was measured throughout the tumour efflorescence by the method

with free access to water in an attempt to mimic deficiencies precipitated by the metabolic competition of the neoplasm. Standard allogenic skin homografts were applied to the back of the thorax within the lymphatic field of the axillae in order to provide the antigenic stimulus of living organized tissue. In order to simulate immunological tolerance, injec- tion of a large dose of xenogenic protein (homo- genated rabbit kidney) was made on alternate days, giving an aggregated dose of 250 mg. of protein per kg.

FIG. 9. FIG. 10. FIG. 11.

FIG. 9.--Photomicrograph of lymph-gland from mouse that had died of tumour. H. and E. ( x 360.) FIG. 10.-Photomicrograph of lymph-gland taken from a mouse that had been implanted with a tumour 12 days prior to sacrifice.

Pappenheim. ( Y 360.) FIG. I I.-Photomicrograph of lymph-gland taken from a mouse that had been implanted with tumour 18 days prior to sacrifice.

Pappenheim. ( )i 960.)

of Lowry, Rosebrough, Farr, and Randall (Ig-jI), and found to parallel closely their weight change which could not, therefore, be due to variation in fluid content. In the same way, the possibility that the change of weight of these organs with tumour development was occasioned by some passenger or associated infective agent, such as Stansly, Ramsay, and Neilson’s (1962) spleen weight factor or Gledhill, Dick, and Niven’s (1955) mouse hepatitis virus, was eliminated by demonstrating the reversibility of these effects. The tumours were removed surgically from a group of animals after they had grown for 9 days (i.e., before suppression had occurred). The results are shown in Fig. 6 . Sham operation had no appre- ciable effects on these organs. I t can be seen that the spleen involuted quite rapidly and the lymph- glands more slowly, while the thymus increased in size after a delay and the liver was little affected. Clearly, if a passenger infective agent had been associated with the tumour then it would have been disseminated and its manifestations unaffected by the removal of the tumour.

WEIGHT CHANGES OF R.E.S. WITH OTHER STIMULI

The response of the R.E.S. to three other specific stimuli was then studied in the hope of recognizing behaviour patterns. Mice were starved to death 56

body-weight. The size of this dose and the lack of any hypersensitivity reaction manifestations suggest that this was in fact immunoparetic. The response of the lymph-glands is shown in Fig. 7. Starvation produced a steady decline in lymph-gland weight. The skin allograft evoked a double-humped curve, the peaks corresponding presumably with graft rejec- tion and healing of the resultant ulcer. The kidney xenograft caused the lymph-glands to increase pro- gressively in size to the tenth day and then to decline more gradually. The rate of increase of the lymph- glands from all three antigenic stimuli is of similar order, but the rates of involution are grossly different.

For the rejected skin allogenic homograft at 0.62 mg. per day and starvation at 0.56 mg. per day the gradients are close, for the xenogenic protein at 0.32 mg. per day it is much less, while for the tumour it is much greater at 1.76 mg. per day. This suggests not simple deficiency as in starvation, withdrawal of stimulation (from loss of tumour specific antigens for example) as in the rejected skin-graft, or immuno- logical tolerance or paresis as in the kidney xenograft, but active suppression.

Here then are represented three different immuno- logical situations :-

I . Persistent R.E.S. and continuing antigenic stimulus as in the kidney injection.

878 BRIT. J. SURG., 1966, Vol. 53, No. 10, OCTOBER

2. Persistent R.E.S. and rejected antigenic stimulus as in the skin-graft. 3. Persistent antigenic stimulus and a suppressed

R.E.S. as in the tumour. Fig. 8 shows the change of weight of the spleen

with the three standard stimuli. This organ does not seem to take much part in the animal’s response to skin allogenic homograft or kidney xenogenic injec- tion so that its response to tumour cannot easily be attributed to simple antigenic stimulus although this

- 38 .o

LIFE DURATION IN DAYS

FIG. IZ.-‘ Vaccination’ experiments showing a significant prolongation of life (represented by dotted area) of a group (Group 11) of treated animals (V, vaccination) with a mean mouse day survival of 26.5 days compared with control Group I with mean mouse day survival of 20.1 days.

view is held by some workers. Its response might well find explanation in either haematopoiesis or a runting effect.

HISTOLOGY OF ORGANS IN RESPONSE TO TUMOUR

In the same way that their weights altered, the histology of organs at death was grossly different from that during tumour efflorescence. The histo- logical picture in the spleen is complicated by both red- and white-cell precursors. Fig. 9 shows a lymph- gland from a mouse that had died of tumour. No malignant cells have metastasized to it, but its archi- tecture has been lost and no lymphocytes are to be seen, and instead a larger more spindle-shaped, paler, open nucleus abounds. Fig. 10 shows a lymph-gland at the same magnification from a mouse implanted with tumour IZ days prior to sacrifice. The sinusoids are dilated and pyroninophilia of giant cells, plasma cells, and reticular cells is present. Fig. 11 shows a higher magnification of a lymph-gland that had drained a tumour for 18 days and shows a typical red-staining giant cell or ‘ immunoblast ’. Pyronino- philia is associated with greatly increased amounts of messenger RNA and indicates immunological activity, and its exhibition in these lymph-glands suggests that an immune mechanism has been provoked by the presence of the tumour. However, all this has become extinguished at death, as shown in Fig. 9.

Histological examination of the small intestine showed in the normal mouse considerable aggrega- tion of small round cells in the submucosa, like Peyer’s patches of man, but in those mice dying from neoplasm these have largely disappeared. Anatomi- cally, therefore, it would appear as if the tumour process has caused the disappearance of the lympho- cyte-the generally accepted mediator of homograft

rejection-from its normal sites, viz., the lymph- glands and small intestine, although this terminal elimination appears to be preceded by histological evidence of immunological stimulation. This was tested functionally by vaccination experiments.

FUNCTIONAL ASSESSMENT OF R.E.S. BY ‘VACCINATION’

Using a tumour-cell-suspension technique a highly reproducible system was established. One hundred mice, distributed in 10 separate groups injected with tumour, had a mean survival of 21.6 days and a standard error of I day, in spite of an eightfold varia- tion in dosage and in variation of site and time of inoculation. Fig. 12 represents two groups and shows that significant (P<o.ooI) prolongation of life could be achieved by the ‘vaccination’ of animals with a homogenate of tumour and Freund’s adjuvant on three occasions at weekly intervals commencing on the third post-implant day. Similar results could be obtained if tumour size were used as a parameter of study instead of life duration.

Tumours were measured daily with vernier callipers in three diameters at right-angles to each other and the figures so obtained multiplied together to give an

RAPID GRolppA

FIG. 13.-Progress of tumour ‘index’ with time. G I1 repre- sents two control groups; G V I I group was vaccinated on the seventh and fourteenth days (vertical arrows). G I vaccination was started on the third day. Gradient reduced from 1.85 x 103 to 0.68 x 10~.

‘index’, the progress with time of which is shown in Fig. 13. Two control groups are shown and com- pared with two experimental groups. The first group’s weekly vaccination protocol started on the seventh post-tumour implantation day and had very little effect. The second experimental group’s protocol started on the third post-implantation day and resulted in a delay of the rapid growth phase from the tenth to the sixteenth day and a decrease in the rate of increase of the tumour index to about one-third of the controls. Subsequent experiments confirmed these findings that host resistance could be enhanced by vaccination with homogenated

EDWARDS : RESPONSE OF RETICULO-ENDOTHELIAL SYSTEM T O CANCER 879

. .

turnour and Freund's adjuvant, but that this was strictly time-dependent and could not be achieved after the third post-implant day.

Vaccination with tumour antigens has only been previously reported to be effective if performed prior to tumour establishment and most of the work has been on carcinogen-induced tumours. The signifi- cant effect of vaccination on this isologous tumour is thought to arise because cognizance had been taken of the all-important time factor.

REGIONAL LYMPHATIC BARRIER So far only generalized factors have been con-

sidered, but the importance of the regional lymphatic barrier was investigated in the following manner. The axillary lymph-glands were excised and 2 weeks later, after complete healing of the operation sites, turnours were implanted either on the side of the thorax within the regional drainage of the axilla or in the R.I.F. outside the area. Sham operations were also performed as controls and found to have no significant effect. Fig. 14 shows that the group in which the excised glands were not regional had a significantly longer life than those in which the regional glands were extirpated. Since the bulk of

- i l l

9 ill

- - - . . ..... ..... ..... ..... I < / <:,oh,!

......... 1 I I, " I0 , I I 4 I* I8 PO zi 21 26 ZR 3" i z 14 36 .,x 4" 42

LIFE DURATION IN DAYS

FIG. rq.-Life duration of tumour-bearing animals with extirpation of regional and non-regional lymph-glands. Signifi- cantly longer life in non-regional group (represented by dotted area).

lymphatic tissue which was removed, the stress of operation, and length of convalescence were similar in the two groups, the effects have been local in nature and suggest that the regional glands had a defensive effect.

SUMMARY OF RESULTS Fig. 15 is a summary of the results. While the

tumour progressively increased in size, the thymus atrophied. Both spleen and lymph-glands hyper- trophied initially in a manner similar to an antigenic response exhibiting histological evidence of immuno- logical activity against the tumour (represented by the shading), but after a critical point all this was extinguished and the organs withered away to leave an end-result (indicated by vertical arrows) in no way representative of the dynamic struggle that has occurred. Therefore to study these organs at only one time is to observe but a single frame of the cine film of the complete process and in so doing lose the perspective of the changes involved. I t is for this reason, it is believed, that the literature is contradictory concerning organ size and neoplasm. 5 6*

DISCUSSION OF POSSIBLE CLINICAL SIGNIFICANCE

If the principles demonstrated in this model may be applied to the human clinical problem, and the reported anergy of cancer patients (Solowey and Rapaport, 1965) would favour this assumption, then some interesting speculations can be made. To postulate that human malignant tumours actively

D B A l 2 J - Ca.D.2 TUMOUR

FIG. 15.-Summary of results. The graphs on the right repre- sent the weight of the organs with time. Hatched areas represent histological evidence of immunological activity.

suppress the R.E.S. is to suggest four attractive concepts :-

I. I t would provide a definition of cancer. Haddow (1965) has said: 'precursor somatic mutants early in the carcinogenic chain are constantly being sup- pressed by immunological mechanisms. Yet even with a strongly antigenic tumour, regression is a rarity.' The successful mutant is then that cell capable of suppressing the rejecting mechanism itself and that mutant is called 'cancer '.

2. It would explain cachexia of patients with small tumours in the 'runt' hypothesis.

3. It would explain the lack of correlation between the demonstration of circulating malignant cells and secondaries, since the fate of such cells would depend on the state of host resistance. It is interesting that Solowey and Rapaport (1965) report an association between anergy and metastases.

4. I t would explain the rarity of cancers of the small intestine in spite of the rapidity of its mucosal regeneration (and for that matter the rarity of splenic secondaries in disseminated cancer) on the grounds of the juxtaposition of the guardian lymphocytic germinal centres.

Such a postulate would affect the concepts of therapy in that host resistance should be courted and supported as an ally in the early phase of the disease and disregarded as a liability in the late. This would have repercussions on the concept and timing of radical surgery and on the use of umbrella cyto- toxic drugs at operation, for most of these are immuno- suppressants (Berenbaum, 1965). It might suggest a surgical duty to reduce the bulk of a tumour in the hope of reducing its anti-R.E.S. effect and the occa- sional effects of removing the primary hyper- nephroma on its secondaries is well known. It would call attention to the immunosupportive maneuvres like those of Ishibashi and others (1961) in Tokyo,

880 BRIT. J. SURG., 1966, Vol. 53, No. 10, OCTOBER

who implanted autografts of abdominal turnours beneath the skin of the thigh in the hope of stimulat- ing resistance, or the procedures of Gorodilova and others (1965) who have recently reported their 10-year figures for breast carcinoma in Muscovite women treated by vaccination. Assay of the patient’s R.E. functional state would allow assessment of, indication for, and rationalization of such procedures.

Ross (1966), in a retrospective study of 200 cases of carcinoma of the breast, has shown a close correla- tion between 10-year survival and the axillary node content of silver-staining reticular cells, which he divided into four grades. I t may well be that he was determining a measure of biological time, by which is meant a compounding of host resistance and tumour aggressiveness, and that an untreated patient would progress from one grade to another. If this is so, and if there is a critical point, as with the mouse model, then it would be of the utmost impor- tance, for it would modify therapy and indicate outcome.

The experimental work described in this paper was started in the laboratories of the Surgical Clinic of Montreal General Hospital and continued in the Dunn Laboratories at St. Bartholomew’s Hospital. I would like to acknowledge my indebtedness to the heads of these departments, Dr. F. Gurd and

Professor G. W. Taylor respectively, for their support, interest, and encouragement.

REFERENCES ASCHOFF, L. (I924), Lectures in Pathology. New York:

BERENBAUM, M. C. (1965), Br. med. Bull., 21, 140. BILLINGHAM, R. E., and BRENT, L. (1g57), Transplantn

Hoeber.

Bull., 4, 67.

(I955),J. Path. Bact., 69, 299.

FOLEY, E. J. (I953), Cancer Res., 13, 835. GLEDHILL, A. W., DICK, G. W., and NIVEN, J. S. F.

GORODILOVA. V. V.. SILINA, I . G., and SARAEVA, Z. M. (1965), Vop. Onkol., 2, 22.

GRAHAM, J. B., and GRAHAM, R. M. (I955), Cancer, N.Y.,

GROSS, L. (1943), Cancer Res., 3, 326. HADDOW, A. (1965), Br. med. Bull., 21, 133. ISHIBASHI, Y., HATTORI, T., FUJII, G., OKADA, K.,

SEKIGUCHI, M., ASHIKAWA, K., and MOTOYA, K. (1961),Jap.J. exp. Med., 31, 319.

LOWRY, 0. H., ROSEBROUGH, N. J., FARR, A. L., and RANDALL, R. J. ( I ~ s I ) , 3. biol. Chem., 193, 265.

METCHNIKOFF, E. (1905), Immunity in Znfective Disease (trans. BINNIE, F. G.). Cambridge : University Press.

OLD, L. J., and BOYES, E. A. (1964), A . Rev. Med., 15,167. Ross, H. B. (1966), personal communication. SOLOWEY, A. C., and RAPAPORT, F. T. (1965), Surgery

STANSLY, P. G., RAMSAY, D. S., and NEILSON, C. F.

8, 409.

Gynec. Obstet., I 2 I, 756.

(1962), Proc. SOC. exp. Biol. Med., 109, 264.

PLATELET ADHESIVENESS RELATED TO LONG-TERM GRAFT PATENCY

BY GEOFFREY EVANS ST. MARY’S HOSPITAL, LONDON

[This is an abstract of the paper read at the meeting.*]

THERE is considerable evidence to show that the adherence of platelets to the vessel wall and to each other is a fundamental step in the formation of the thrombi from flowing blood. Indeed thrombi will not form in flowing blood of animals rendered thrombo- cytopenic by immunological methods or in extra- corporeal shunts of pigs rendered thrombocytopenic.

These platelet emboli on the vessel wall can be incorporated into the intima by being overgrown with endothelium. They can then give rise to thicken- ing of the intima, a condition so often seen in early stages of atheroma.

Experimental evidence shows that the rapid adherence of platelets to the endothelium and sub- endothelial tissues at points of damage is due to the release of adenosine diphosphate. ADP is highly specific for causing platelet aggregation.

Considering then that platelet aggregation may be an early stage in thrombosis, we undertook a retro- spective study on a group of patients who had had a femoro-popliteal graft inserted for superficial femoral

* The full contents of the paper was published in The Lancet,(1g66), 2, 353.

artery thrombisis. Platelet adhesiveness was measured using the Hellem technique. Owren and his associates have studied this for some years and found that the platelet adhesiveness is constant in a given patient over a period of years.

The results of this study show a significant difference between the group under study and a control group of patients (0.005 <P<o.ooI). There is also a significant difference (0.005 > P > 0.001) between the patent grafts and the thrombosed grafts.

We also consider that one can use this test to predict the duration of long-term patency. We have undertaken a forward-progressing study on a group of patients who have had femoro-popliteal grafts inserted and the results are very similar to those attained in the retrospective study.

As platelet adhesiveness seemed to bear a direct relationship to late failure of a graft it was thought pertinent to study the effect of the reduction of platelet adhesiveness on the longevity of graft patency. Owren and his associates published in 1965 the use of linseed oil containing linolenic acid for this purpose. In a controlled blind trial, however, linseed oil was not found to have any significant effect on platelet adhesiveness.