The long lifespan and low turnover of human islet beta cells estimated by mathematical modelling of lipofuscin accumulation.

AIMS/HYPOTHESIS: Defects in pancreatic beta cell turnover are implicated in the pathogenesis of type 2 diabetes by genetic markers for diabetes. Decreased beta cell neogenesis could contribute to diabetes. The longevity and turnover of human beta cells is unknown; in rodents <1 year old, a half-life of 30 days is estimated. Intracellular lipofuscin body (LB) accumulation is a hallmark of ageing in neurons. To estimate the lifespan of human beta cells, we measured beta cell LB accumulation in individuals aged 1-81 years. METHODS: LB content was determined by electron microscopical morphometry in sections of beta cells from human (non-diabetic, n = 45; type 2 diabetic, n = 10) and non-human primates (n = 10; 5-30 years) and from 15 mice aged 10-99 weeks. Total cellular LB content was estimated by three-dimensional (3D) mathematical modelling. RESULTS: LB area proportion was significantly correlated with age in human and non-human primates. The proportion of human LB-positive beta cells was significantly related to age, with no apparent differences in type 2 diabetes or obesity. LB content was low in human insulinomas (n = 5) and alpha cells and in mouse beta cells (LB content in mouse <10% human). Using 3D electron microscopy and 3D mathematical modelling, the LB-positive human beta cells (representing aged cells) increased from >or=90% (<10 years) to >or=97% (>20 years) and remained constant thereafter. CONCLUSIONS/INTERPRETATION: Human beta cells, unlike those of young rodents, are long-lived. LB proportions in type 2 diabetes and obesity suggest that little adaptive change occurs in the adult human beta cell population, which is largely established by age 20 years.

The specificity of rejection and the absence of susceptibility of pancreatic islet beta cells to nonspecific immune destruction in mixed strain islets grafted beneath the renal capsule in the rat.

The specificity of rejection of isolated pancreatic islets was examined in the rat using a quantitative model in which syngeneic (DA) or a mixture of syngeneic and allogeneic (DA and LEW or PVG) islets were implanted beneath the capsule of the kidney of nondiabetic normal rats (DA). 3 wk after transplantation total insulin extraction assays of the kidney with its islet implant together with immunohistological examination of the site of transplantation for evidence of syngeneic or allogeneic tissue demonstrated the total destruction of allogeneic islets without any evidence of damage to syngeneic islets either distant or in immediate proximity to allogeneic islets. Pancreatic islets, and especially beta cells, appear to be particularly vulnerable to the effector arm of both autoimmune and alloimmune responses, a vulnerability that has been attributed to the cytotoxic effects of lymphokines, notably IL-1, released in both autoimmune and alloimmune responses. The experiments reported here demonstrate not only the exquisite specificity of the allograft reaction but are not compatible with a hypothesis that B cells within an intact islet are nonspecifically susceptible to destruction by lymphokines.

Protease activity in pancreatic islet isolation by enzymatic digestion.

Commercial Collagenase* prepared from Clostridium histolyticum is widely used in isolation of pancreatic islets. It is known that the enzyme is very impure and that there are substantial variations in effectiveness between batches. Our studies suggest that one of the impurities of importance in islet isolation is a protease that has not been very well characterized. Comparison of two batches of enzyme, one of which was known to give good yields of islets and the other poor yields, showed that they had very similar activity against collagen (measured by digestion of insoluble collagen followed by assay of soluble products with ninhydrin) but substantially different activities against azocasein as measured by optical density increase (measured by release of dye). Eighteen batches of Collagenase were examined for efficiency in islet isolation, and the yields obtained correlated with manufacturer's data of activity against casein. The data show that low caseinase activity is associated with performance in islet isolation (r = .5 after adjusting for collagenase activity). The effect of supplementing a batch of collagenase, known to be poor in isolating islets, with proteolytic enzymes was investigated. Trypsin and papain had apparently no effect, but dispase significantly increased yield. Dispase alone failed to digest pancreas. Size-exclusion high-performance liquid chromatography identified a peak associated with high protease activity and efficiency in islet isolation, having an Mr of approximately 30,000, compared to 78,000 for collagenase. The protease, like collagenase, is inhibited by EDTA. Increased Ca2+ and Mg2+ (up to 10 mM) did not affect activity. Both the protease and collagenase are stable under normal use but are inactivated by heating at 56 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Separation of pancreatic islets by fluorescence-activated sorting.

To allow clinical pancreatic islet transplantation, the yield and purity of islets must be improved. Intravital staining of islets with neutral red is a specific, nontoxic technique for labeling islets of various species. Using neutral red-stained rat islets, we investigated the known fluorescence absorbance and emission spectra in comparison with unstained exocrine tissue and have shown that stimulation with light of wavelength between 500 and 560 nm produces detectable emission greater than 610 nm, which is absent from unstained exocrine tissue. The PARTEC cell sorter is an inexpensive alternative to currently available fluorescence-activated cell sorters and has a sorting mechanism based on a piezoelectric valve. We made extensive modifications to this machine to allow passage of particles up to 300 micron diam. Using rat pancreas stained intravitally with neutral red and dispersed by intraductal collagenase technique, we have shown that islets can be accurately identified in a high-speed flow system and sorted to a purity of greater than 90% islet tissue. The islets remain intact and viable as determined by supravital staining and isogeneic transplantation to the kidney capsule site. These studies prove the feasibility of separating intact islets by fluorescence-activated sorting.

Normalization of hyperglycemia in diabetic rats by intraportal transplantation of cryopreserved islets from four donors.

Techniques for freezing rat islets have been examined by the intensive use of the supravital stains fluorescein diacetate and ethidium bromide. By the use of a simple scoring system, the effect of the cooling rate, treatment with dimethyl sulfoxide (DMSO), rate of thawing, and postthaw culture were examined. These studies showed the most effective method to be a 24-h culture of islets, followed by partial incubation with 20% DMSO at 0 degrees C, followed by seeding at -8 degrees C in an alcohol bath. The islets were then cooled at a rate of -0.25 degrees C/min to -40 degrees C followed by quenching in liquid nitrogen at -196 degrees C. Rapid thawing at 37 degrees C was then followed by a 24-h culture. Islets from four Lewis rat donors were cryopreserved, counted, and transplanted intraportally into streptozocin-induced diabetic Lewis rats. Corresponding control transplants were performed with islets from four donors only cultured for 48 h. The results showed that reversal of hyperglycemia in severely diabetic rats was obtained at 5, 5, 6, 6, 6, or 8 days with cryopreserved islets from four donors, compared to reversal of diabetes at 1, 4, 5, 6, 7, and 12 days with islets from four donors subjected to culture alone. The new cryopreservation technique has several small modifications over previously described methods and results in a significant improvement in islet survival.

A method for isolation of islets of Langerhans from the human pancreas.

A method has been developed for the isolation of islets of Langerhans from the human pancreas. The average number of islets isolated was 1011 islets per gram of pancreas (SD 475, range 752-2111), and the purity of the preparation as defined by histologic examination and specific staining for insulin varied from 10% to 40%. Islet structure was well preserved and the islets were shown to be viable by supravital staining, demonstration of insulin response to glucose, and by transplantation of isolated islets beneath the renal capsule of nude mice. The essential features of this technique for isolation of human islets include injection of a high concentration of collagenase (6 mg/ml) into the pancreatic duct under pressure, followed by a short incubation (23 min) at 39 degrees C. The gland is then dispersed by a process of teasing and shaking, and the islets are separated by a two-stage process of filtration on a nylon mesh to remove the larger islets and centrifugation on a preformed Ficoll density gradient to separate the small islets.

A new method for quantification of islets by measurement of zinc content.

The ability to quantify the yield of pancreatic islet tissue after isolation is important for interlaboratory comparisons and for the assessment of islet yield prior to clinical transplantation. Because pancreatic islets contain a much higher concentration of zinc than other tissues, we investigated the analysis of zinc as a measure of islet tissue yield. Rat islets of standard diameter 250 microns were handpicked into samples containing 10-80 islets. The zinc content was measured by EAAS and showed a linear correlation with islet number. A zinc binding fluorescent dye, TSQ, was investigated as a way of simplifying the zinc measurement for routine use. Samples of 10-80 islets of 250 microns were sonicated in 3 ml zinc-free water, 0.18 mumol TSQ was added, and the TSQ-zinc fluorescence was measured at 480 nm. A linear correlation was observed. Exocrine contamination up to 50% barely affected the results. Islet zinc content also was shown to be correlated linearly with islet number for freshly isolated human islets. Measurement of zinc by TSQ fluorescence is a rapid, cheap, and objective measure of islet tissue content.

Metabolic function of intraportal and intrasplenic islet autografts in cynomolgus monkeys.

Intraportal islet autografting can restore near-normal glucose homeostasis in large diabetic animals, but the long-term failure rate of such grafts remains high. To assess the effect of the site of transplantation, we compared the hormonal responses to glucose (500 mg/kg i.v.) of intraportal (IP) and intrasplenic (IS) islet autografts in the cynomolgus monkey previously rendered diabetic by total pancreatectomy. Intravenous glucose tolerance tests (IVGTTs) 6 wk after IP grafting (n = 10) demonstrated nearly normal plasma glucose changes, with qualitatively normal but quantitatively reduced insulin and glucagon responses; only two animals have maintained these responses for greater than 2 yr. IVGTTs 6 wk after IS grafting (n = 4) demonstrated more abnormal plasma glucose changes, with qualitatively normal but weak insulin responses and glucagon levels that did not fall in response to hyperglycemia; only one animal has maintained fasting normoglycemia for greater than 9 mo. These results suggest that IS transplantation confers no benefit over IP transplantation in this model.

Comparison of the collagen VI content within the islet-exocrine interface of the head, body, and tail regions of the human pancreas.

Efficient islet isolation depends on the use of collagenase to digest the extracellular matrix within the islet-exocrine interface, the molecular structure of which is poorly understood. Recently it has been reported that transplantable yields of islets can be isolated from the tail segment of the pancreas alone. This study aimed to quantify and compare the amount of collagenase-resistant collagen VI within the islet-exocrine interface of the head, body, and tail of the human pancreas. Human adult pancreata (n = 5) were retrieved from heart-beating donors (age range, 40-62 years; cold ischemia times <10 hours). Tissue blocks from the head, body, and tail region of each pancreas were fixed in formalin and processed for immuno-labelling of collagen VI, which was quantified in the islet-exocrine interface using a Zeiss KS-400 image analysis system. Data were expressed as area of collagen at the interface relative to the islet area. Statistical analysis was done using paired t test. The mean islet areas in the head, body, and tail regions were not significantly different. Collagen VI was uniformly present within the islet-exocrine interface of all regions of the pancreas and was 0.326 +/- 0.064, 0.324 +/- 0.060, and 0.334 +/- 0.052 microm(2)/islet area (P = .441) in the head, body, and tail, respectively. The content of collagen VI within the islet-exocrine interface was uniform throughout all parts of the adult pancreas. Targeting this collagen subtype with novel collagenase blends may result in consistently improved islet yields and enable a wider number of available donor pancreata to be used.

Regulation and specificity of glucose-stimulated insulin gene expression in human islets of Langerhans.

The insulin response of cultured human islets of Langerhans was measured at both mRNA and polypeptide levels in response to natural and pharmacological stimuli. We report a dosage dependent stimulation of both mRNA levels and insulin secretion by extracellular glucose, and present evidence that islet responsiveness can be divided into two temporal phases: an early response, apparently under post-transcriptional control, and a late phase in which insulin messenger accumulates. Although glucose effects in man are similar to rodents, there are important differences, especially with respect to modulation of glucose stimulation by activators of beta-cell protein kinases.

Islet cell transplantation for insulin-dependant diabetes mellitus: perspectives from the present and prospects for the future.

The long-term complications of insulin-dependant diabetes mellitus have become a major health care problem, and it is now clear that they arise from inadequate homeostatic control of blood glucose by injected replacement insulin. Transplantation of pancreatic islets is arguably the most logical approach to restoring metabolic homeostasis in people with diabetes. This review looks at the current status of human islet transplantation and the problems that remain. These include: (1) the limited supply of human islet tissue available for transplantation; (2) the adverse effects of current immunosuppressive protocols on diabetic patients; (3) the problems of primary nonfunction of the transplanted islets; (4) the rejection of islets; and (5) the recurrence of autoimmune diabetic disease. Some of the approaches that might solve these problems are then examined: (1) immune modulation to reduce or prevent immune attack by the recipient's immune system; (2) immunoisolation to prevent recognition of the islet graft; (3) induction of tolerance; (4) xenotransplantation using islets derived from animals; and (5) gene therapy.

Modulation of muscarinic cholinoceptor-stimulated inositol 1,4,5-trisphosphate accumulation by N-methyl-D-aspartate in neonatal rat cerebral cortex.

The mechanisms by which N-methyl-D-aspartate (NMDA) receptor activation can modulate muscarinic receptor-stimulated phosphoinositide turnover have been studied in neonatal rat cerebral cortex slices. A maximally effective concentration of carbachol (1 mM) caused a large stimulation of both total [3H]inositol phosphate ([3H]InsPx) accumulation (30-40-fold over basal levels after 15 min in the presence of 5 mM LiCl) and inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] mass accumulation (consisting of a rapid peak increase of about 8-10-fold within 15 sec followed by a sustained plateau rise of 4-5-fold which persisted for > 10 min). Low concentrations of NMDA enhanced carbachol-stimulated [3H]InsPx and Ins(1,4,5)P3 accumulations with a maximal effect being observed at 10 microM NMDA. However, at higher concentrations of NMDA (30-300 microM) a dramatic inhibition of these indices of phosphoinositide turnover was observed. Time-course studies demonstrated that NMDA (100 microM) caused a significant enhancement of the initial increases in [3H]InsPx and Ins(1,4,5)P3 accumulations stimulated by carbachol, with the profound inhibitory effects becoming evident at longer incubation times. The modulatory effects of NMDA were antagonized by D-2-amino-5-phosphonopentanoate and MK-801. Reducing extracellular calcium concentration ([Ca2+]e) to the low micromolar range decreased basal Ins(1,4,5)P3 accumulation and attenuated the response to carbachol. Under these conditions NMDA (10-100 microM) caused only a potentiation of agonist-stimulated Ins(1,4,5)P3 accumulation. Under control conditions ([Ca2+]e = 1.3 mM), addition of MK-801 (1 microM) 10 min after carbachol + 100 microM NMDA challenge failed to reverse the inhibitory effect of NMDA on carbachol-stimulated [3H]InsPx accumulation. Furthermore, pre-incubation of cerebral cortex slices with 100 microM NMDA for 15 min (followed by extensive washing of slices to remove NMDA) dramatically decreased [3H]inositol incorporation into the cellular inositol phospholipid fraction and decreased basal and carbachol-stimulated Ins(1,4,5)P3 mass accumulations. We conclude that the enhancement of agonist-stimulated phosphoinositide turnover seen at concentrations of NMDA up to 10 microM may be due to Ca2+ entry and Ca2+ facilitation of phosphoinositide-specific phospholipase C activity. In contrast, the inhibitory effect of high concentrations of NMDA on agonist-stimulated phosphoinositide turnover may be due to progressive, irreversible and, at least in part, Ca(2+)-dependent damage to the cell populations in the slice preparation responding to muscarinic-receptor stimulation.

The effect of hyperglycemia on isolated rodent islets transplanted to the kidney capsule site.

The effect of hyperglycemia on transplanted rat pancreatic islets was studied using a new technique for transplanting a defined number of islets in a blood clot. Normal or streptozotocin-diabetic DA rats were given 400 DA islets under the left kidney capsule (a number shown to be insufficient to reverse diabetes). After 2 weeks the diabetic rats were given a further 1000 islets under the right kidney capsule to reverse diabetes. Kidneys from both groups were examined at 2 weeks after the initial islet implant and at 3 months for both gross and histological appearance and for insulin content. After 2 weeks left kidneys from nondiabetic rats showed abundant islet tissue, with an insulin content of 116 (+/- 14 SEM) milliunits, compared to 1 +/- 0.5 milliunits in the right kidney. Kidneys from diabetic rats showed no islets recognizable grossly. Histological examination showed vacuolated tissue scarcely recognizable as islet tissue, and the insulin content of the left kidney was reduced to 18 +/- 5 milliunits. However, 3 months after reversal of diabetes by transplantation of 1000 islets to the right kidney, histologically "normal" islet tissue was again visible on the left kidney, and the insulin content was 160 +/- 36 milliunits. Islets left in normal animals for 3 months contained 195 +/- 50 milliunits. These experiments show that islets implanted beneath the kidney capsule in diabetic rats are not destroyed by two weeks hyperglycemia. This suggests that protection of islets after implantation by insulin treatment is unnecessary, even in the presence of a persistently raised blood sugar.

In vitro staining of islets of Langerhans for fluorescence-activated cell sorting.

A previously described technique from the author's laboratories for purification of pancreatic islets by fluorescence-activated cell sorting used the dye neutral red (NR) to obtain specific fluorescence of islets sufficient to give a sorting signal. A major drawback with this technique was the need to inject the dye intravascularly before excision of the pancreas. Preliminary investigations showed that NR would produce selective staining of islets by topical application in vitro but only at low concentrations that were insufficient to give fluorescence strong enough for sorting. The chelating agent dithizone (DTZ) produces bright red staining of islets by topical application in vitro. Further studies showed that dithizone-stained islets exhibited moderately strong fluorescence that faded too quickly for reliable sorting. By combining both NR and DTZ staining in vitro, selective fluorescence of islets was obtained that was sufficient to allow efficient sorting. Using the combined DTZ/NR stain the yield of islets obtained by sorting from a single rat pancreas was 569 +/- 72 (n = 16), corresponding to 83% of the islets present in the digest. The mean purity of the preparation, confirmed by histologic examination, was 80%. The viability of the islets was shown to be good both by supravital staining and by the successful correction of streptozotocin diabetes in syngeneic rats following transplantation of sorted islets.

Variation in expression of endothelial adhesion molecules in pretransplant and transplanted kidneys--correlation with intragraft events.

Endothelial adhesion molecules are directly involved in the localization and migration of leukocytes from the circulation into tissues at sites of inflammation. We have compared the expression of PECAM-1 (CD31), ELAM-1, ICAM-1 (CD54), and VCAM-1 in pretransplant (n = 20) and needle-core biopsies from renal transplants obtained during different clinical circumstances (n = 42). PECAM-1 was consistently expressed on all endothelium in both pretransplant and transplant biopsies. In contrast, there was variation in endothelial expression of ELAM-1 and in proximal tubular expression of ICAM-1 and VCAM-1 between pretransplant biopsies. After transplantation induced expression of endothelial ELAM-1 and VCAM-1 and tubular induction of ICAM-1 and VCAM-1 was detected. Induced adhesion molecule expression was frequently associated with focal leukocyte infiltration, and there was a significantly higher level of CD45 and CD25 positive cell infiltration in biopsies with induced adhesion molecule expression. The induction of adhesion molecule expression is evidence of endothelial activation in these transplant biopsies. Comparison of adhesion molecule expression and HLA-class II antigen expression revealed that induced tubular class II antigens may be detected in the absence of induced adhesion molecule expression.

Survival of cryopreserved isolated adult human pancreatic islets of Langerhans.

Human islets of Langerhans were isolated from the pancreata of 13 adult organ donors, cultured for 24 h, cryopreserved, stored in liquid nitrogen at -196 degrees C for 6-88 days, thawed, and then cultured again. The number of islets recovered after this procedure was 80% of that present at the beginning. The viability of cultured/cryopreserved islets was then compared with that of islets from the same donor cultured for 24 hr, and was assessed by supravital staining, insulin response to glucose, and survival after implantation under the kidney capsule of nude rats. Supravital staining showed more nonviable cells in cryopreserved islets than in their cultured counterparts. Significant response to glucose was seen before and after cryopreservation in 2 of 4 sets of islets. Xenografts of 200 cultured islets (from 13 donors) were implanted in 15 nude rats under the kidney capsule, and a further 15 rats had cryopreserved islets (from the same 13 donors) similarly implanted beneath the kidney capsule. Two weeks later tissue was visible at the site of implantation in all 30 rats. Histological examination of both groups showed the tissue to have the morphology of islets, confirmed by immunohistochemical chemical localization of insulin. The insulin content of kidneys bearing 200 cultured islets was 7.88 +/- 1.6 mU (n = 13) versus 6.84 +/- 1.43 mU (n = 13) for kidneys bearing cryopreserved islets. Thus this technique for cryopreservation of isolated adult human islets enables a high recovery of endocrine tissue that survives after transplantation to nude rats, but some evidence of damage was apparent from insulin secretion studies and electron-microscopic studies.

The factor V Leiden (R506Q) mutation and risk of thrombosis in renal transplant recipients.

BACKGROUND: Renal transplantation and chronic renal failure are associated with an increased risk of venous thrombosis and myocardial infarction (MI). We investigated whether resistance to activated protein C due to a mutation in the factor V gene (FV Leiden/FV506Q) may predispose patients to thrombosis. METHODS: Three hundred patients who had undergone renal transplantation were genotyped for the FV mutation. Seventy-seven patients who had suffered thrombotic complications (42 venous, 28 arterial, and 7 both) were compared with 223 patients free of thrombosis. RESULTS: Thirty-two patients had suffered early renal allograft thrombosis (30 venous), and 33 patients had suffered MI. A higher proportion of the patients with thrombosis, compared to those without, had a family history of arterial cardiovascular disease (42% vs. 26%, P=0.04). Eighteen (6%) patients were heterozygous for FV506Q and seven (39%) of these had suffered venous thrombosis (including four primary allograft thromboses), compared with 15% of the patients without the mutation (P<0.05). The odds ratio for risk of venous thrombosis for FV506Q carriers was 3.6 (95% confidence interval: 1.3-9.9) or 4.0 (1.2-13.8) for primary allograft thrombosis. Only one of the FV506Q carriers had suffered an MI. CONCLUSIONS: Carriers of the factor V 506Q mutation with chronic renal failure who have undergone transplantation are at an increased risk of venous but not arterial thrombosis. This mutation explained 14% of all venous and 20% of primary allograft thrombosis, suggesting that other unidentified genetic and environmental factors contribute to the risk of thrombosis in renal transplant recipients.

Preemptive cadaveric renal transplantation--clinical outcome.

Preemptive cadaveric renal transplantation (PCRT) maximizes the chance of maintaining high quality of life and may avoid the morbidity of dialysis and the associated financial costs. These benefits are offset by disadvantages, which include the possibility of transplantation many months before the need for dialysis, resulting in wasted organ function; an immediate risk of graft failure with conversion to a dialysis-dependent state; and uncertainty of the safety of PCRT. Patients who underwent PCRT between June 1976 and December 1994 at the Oxford Transplant Centre were compared with a matched cohort of first cadaveric transplant recipients who were dialysis-dependent when transplanted. The 116 patients in the PCRT cohort were well matched to the control group with respect to sex, age, blood group, HLA match, degree of sensitization, donor age, immunosuppression, and year of transplantation. Patient and graft survival were significantly better in the PCRT group. The difference in graft survival did not appear to be completely explained by better patient survival, as suggested by a trend toward better graft survival after excluding death with a functioning graft as a cause of failure. Among surviving grafts there were no significant differences in graft function as assessed by 1, 2, and 3 year plasma creatinine levels. In conclusion, PCRT appears to be safe and may even be associated with superior graft survival when compared with conventional transplantation. Early inclusion on a transplant waiting list with a view to PCRT can be justified with respect to the clinical outcome but the financial costs and implications for the utilization of cadaveric donor kidneys must also be considered.

Cytokine gene expression in pancreatic islet grafts in the rat.

We examined the production of cytokine message in allogeneic and syngeneic rat pancreatic islet grafts using specific primers and polymerase chain reaction. Freshly isolated islet preparations contained transcripts for interleukin (IL)-1alpha, IL-6, IL-10, and interferon-gamma (IFN-gamma) but not for IL-2. IL-1alpha in allogeneic grafts showed increased and consistently high expression from 1 to 7 days after transplantation, but the level in syngeneic grafts fell quickly to pretransplant levels. IL-2 and IFN-gamma transcripts were found in allogeneic grafts at 1, 3, 5, and 7 days after transplantation with a peak at day 5, but these cytokines were almost absent from syngeneic grafts. The peak of IL-6 expression was 1 day after transplantation in both syngeneic and allogeneic grafts, and then the level fell quickly. IL-10 was produced at approximately the same high level at all time points in both syngeneic and allogeneic grafts. The results show that freshly isolated islet preparations contain IL-1alpha, IL-6, IL-10, and IFN-gamma transcripts at the time of transplantation. The initial production of cytokines in islet grafts, especially IL-1, may explain phenomena such as graft nonfunction, rapid rejection, and lack of response to immunosuppression.

Isolated pancreatic islet allografts in rats rendered immunologically unresponsive to renal allografts. The effect of the site of transplantation.

Long-surviving Lewis (RT-1(1)) renal allografts (LS-LEW) were induced in 20 DA (RT-1a) rats by 14-day treatment with cyclosporine . All were made diabetic 100 days after transplantation using streptozotocin; 7 LS-LEW were untreated and all remained diabetic; 5 LS-LEW were given Lewis islets beneath the kidney capsule without further immunosuppression. Prolonged graft survival (greater than 100 days) was seen in 4 rats. Lewis islets were given into the portal vein in 5 LS-LEW. Prolonged graft survival was seen in 4 rats. Third-party BN islets were given beneath the kidney capsule in 3 LS-LEW; these islets were rejected in less than 9 days. In contrast Lewis islets transplanted into untreated diabetic DA rats beneath the renal capsule or into the portal vein survived for a mean of 8.3 days and 4 days, respectively. In a separate experiment long-surviving Lewis renal allografts were induced in 7 PVG rats (LS-PVG) by cyclosporine treatment. These animals were made diabetic 100 days after transplantation and then were given Lewis islets under the renal capsule of the transplant kidney. Prolonged islet graft survival was seen in 6 rats, and 5 diabetic PVG rats given Lewis islets beneath the renal capsule rejected the islets within 8 days. Thus, once a recipient rat has accepted a renal allograft under the influence of cyclosporine treatment, it will accept permanently an islet allograft of the same strain as the kidney. This effect applies to both strain combinations tested, is not influenced by the site of islet implantation, and is specific for islets of the same strain as the renal allograft.