Steroid-free immunosuppression with low-dose tacrolimus is safe and significantly reduces the incidence of new-onset diabetes mellitus following liver transplantation

OBJECTIVES

Corticosteroids (CS) are traditionally used as part of the basal immunosuppression (IS) following liver transplantation (LT) but are known to be associated with an increased risk of new-onset diabetes mellitus (NODM), cardiovascular morbidity and mortality. The aim of this study was to retrospectively compare the incidence of transient as well as persistent NODM, rejection rate and patient- and graft survival between patients receiving steroid-based and steroid-free maintenance IS.

MATERIALS AND METHODS

A total of 238 patients liver transplanted (2008-2011) with deceased donor livers were divided into two groups, one group that received steroid-based IS (tacrolimus (TAC), corticosteroids (CS), ± mycophenolate mofetil (MMF); n = 155) (2008-2011) and another group of non-autoimmune recipients that received steroid-free IS (TAC, MMF; n = 83) according to our new maintenance IS-protocol starting January 2010. The primary and secondary end-points were patient- and graft survival, rejection rates and the incidence of NODM. The median follow-up times were 1248 days and 681 days, respectively.

RESULTS

The one-year patient- and graft survival in the steroid-based and steroid-free group was 92.7% and 93.3% (ns) and 87.6% and 84.9% (ns), respectively. The incidence of biopsy proven acute rejection (BPAR) was 27.7% in both groups (ns) during follow-up. The overall incidence of persistent NODM in the two groups were 16.8% and 2.9%, respectively (p < .01).

CONCLUSIONS

The results show that steroid-free low-dose tacrolimus-based IS following LT is safe and decreases the incidence of NODM significantly.

Decreasing incidence of cancer after liver transplantation-A Nordic population-based study over 3 decades

Cancer remains one of the most serious long-term complications after liver transplantation (LT). Data for all adult LT patients between 1982 and 2013 were extracted from the Nordic Liver Transplant Registry. Through linkage with respective national cancer-registry data, we calculated standardized incidence ratios (SIRs) based on country, sex, calendar time, and age-specific incidence rates. Altogether 461 cancers were observed in 424 individuals of the 4246 LT patients during a mean 6.6-year follow-up. The overall SIR was 2.22 (95% confidence interval [CI], 2.02-2.43). SIRs were especially increased for colorectal cancer in recipients with primary sclerosing cholangitis (4.04) and for lung cancer in recipients with alcoholic liver disease (4.96). A decrease in the SIR for cancers occurring within 10 years post-LT was observed from the 1980s: 4.53 (95%CI, 2.47-7.60), the 1990s: 3.17 (95%CI, 2.70-3.71), to the 2000s: 1.76 (95%CI, 1.51-2.05). This was observed across age- and indication-groups. The sequential decrease for the SIR of non-Hodgkin lymphoma was 25.0-12.9-7.53, and for nonmelanoma skin cancer 80.0-29.7-10.4. Cancer risk after LT was found to be decreasing over time, especially for those cancers that are strongly associated with immunosuppression. Whether immunosuppression minimization contributed to this decrease merits further study.

Tacrolimus inhibits discordant islet xenograft rejection: a study in the pig-to-rat model

The aim of the present study was to evaluate the immunosuppressive effect of tacrolimus (TAC) in discordant islet xenotransplantation. Fetal porcine islet-like cell clusters (ICCs) were transplanted under the kidney capsule in normoglycemic rats treated with TAC monotherapy, TAC plus other immunosuppressive drugs or cyclosporin A (CsA) monotherapy. Twelve or 24 days after transplantation, the extent of a cellular infiltration in the xenografts was evaluated using immunohistochemistry. In some animals, the grafts were examined for antibody and complement deposition and the levels of xenoreactive antibodies in serum were determined. In untreated rats, the xenografts were completely rejected after 12 days and no intact ICCs remained. TAC monotherapy (at 0.5 and 1.0 mg/kg b.w.) almost completely inhibited rejection for up to 12 days. In animals treated with TAC monotherapy (at 0.5 mg/kg b.w.), rejection was markedly inhibited for up to 24 days. However, the effect after 24 days was not consistent and in some grafts there were signs of rejection. The protective effect of TAC observed in this study is in contrast to the findings in rats given CsA monotherapy in which no or only a marginal effect on islet xenograft rejection was observed. Only when CsA was given at 20 mg/kg b.w., an inhibitory effect could be observed. Immunosuppression with TAC at a suboptimal dose (0.3 mg/kg b.w.) plus 15-deoxyspergualin or brequinar also had an inhibitory effect on the rejection. In animals given TAC plus mycophenolate mofetil, a protective effect was observed as well; however, this effect was not consistent.

Importance of the Gal alpha1-3 Gal antigen in discordant islet xenotransplantation: immunosuppression, which inhibits porcine islet xenograft rejection in ordinary mice, is equally effective in Gal-knockout mice

BACKGROUND

Islet xenotransplantation will most likely be performed in diabetic patients treated with immunosuppressive drugs. The importance of the galactosyl alpha(1-3) galactose (Galalpha1-3Gal) antigen in immunosuppressed islet xenograft recipients has not been studied.

METHODS

Fetal porcine islet-like cell clusters (ICCs) were transplanted into the renal subcapsular space of both Gal-knockout mice and ordinary mice. Transplantations were performed in untreated mice and mice immunosuppressed with cyclosporine A (CsA) plus 15-deoxyspergualin (DSG). Studies were also performed in immunosuppressed Gal-knockout mice that had been actively immunized against Galalpha1-3Gal. Evaluation was performed 12 days after transplantation using morphologic techniques. The levels of serum immunoglobulin (Ig)G and IgM to the Galalpha1-3Gal antigen or to the ICCs were determined.

RESULTS

No difference in the morphologic appearance could be seen between ordinary mice and Gal-knockout mice. No deposits of IgG, IgM, or C3 could be detected. Almost no difference could be seen between immunosuppressed Gal-knockout mice and immunosuppressed ordinary mice. In immunosuppressed, immunized Gal-knockout mice, the results were similar. In ordinary mice treated with CsA+DSG, the levels of anti-Gal IgM were lower than they were in untreated mice, whereas the levels of anti-Gal IgG were similar. In Gal-knockout mice (including immunized animals) treated with CsA+DSG, the levels of anti-Gal IgG and IgM were lower than they were in untreated Gal-knockout mice.

CONCLUSIONS

After renal subcapsular transplantation, antibodies against Galalpha1-3Gal have no major influence on islet xenograft rejection in the pig-to-mouse model. Immunosuppression, which inhibits rejection in the pig-to-mouse model, is equally effective when transplantation is performed across the Galalpha1-3Gal barrier.

Immunosuppression with FTY720 and cyclosporine A inhibits rejection of adult porcine islet xenografts in rats

BACKGROUND

Our aim was to evaluate the effect of FTY720 in discordant islet xenotransplantation.

METHODS

Fetal porcine islet-like cell clusters (ICCs) were transplanted into normoglycemic rats that were either left untreated or treated with FTY720 only, with FTY720 plus cyclosporine A (CsA) or with CsA only. Twelve or 24 days after transplantation, graft morphology was evaluated immunohistochemically. Furthermore, adult porcine islets (APIs) were transplanted into diabetic rats immunosuppressed with FTY720 plus CsA. Blood glucose and porcine C-peptide levels were monitored.

RESULTS

In untreated rats, the ICC xenografts were completely rejected after 12 days. Treatment with CsA had only a marginal effect on the rejection. In animals given FTY720, only the number of infiltrating cells was somewhat reduced. However, at 12 days, no intact ICCs remained. Immunosuppression with FTY720 plus CsA had a marked inhibitory effect on islet xenograft rejection and plentiful morphologically intact ICCs remained. Twelve days after transplantation, only occasional macrophages and T cells could be detected. At 24 days after transplantation, the findings were similar. Furthermore, diabetic rats transplanted with APIs and immunosuppressed with FTY720 plus CsA remained normoglycemic for 53.0+/-15.8 days. In fact, one animal remained normoglycemic for more than 100 days. Serum levels of porcine C-peptide remained at levels similar to those for human C-peptide in healthy individuals.

CONCLUSIONS

Immunosuppression with FTY720 plus CsA inhibited almost all morphological signs of pig-to-rat islet xenograft rejection for up to 24 days after transplantation. Diabetic rats transplanted with APIs and immunosuppressed with FTY720 plus CsA remained normoglycemic for 53.0+/-15.8 days.

A new in vitro model for the study of pig-to-human vascular hyperacute rejection

Studies on vascular hyperacute xenograft rejection (HAR) are usually conducted in vitro on cultured endothelial cells (EC) exposed to human serum, in complex whole organ perfusion models using heparinized blood or in vivo models. Here we describe a new model allowing perfusion of pig vessels with human whole blood without anticoagulants. Segments of the porcine iliac artery were connected to circular polyvinyl chloride (PVC) tubing, whose inner surface was conjugated with immobilized heparin. The vessels were perfused with 7 to 8 ml of fresh, non-anticoagulated human blood by rocking of the tubing device for 5, 15 or 60 min in an incubator at 37 degrees C. Human iliac arteries (n = 4) were perfused with fresh human ABO-compatible blood as controls. Perfusion of human vessels resulted in changes in the blood and plasma parameters similar to those in the PVC control loop. Overall, perfusion of the porcine vessels generated high levels of C3a, sC5b-9 and thrombin-anti-thrombin (TAT). Platelet consumption was near total (97.2 +/- 1.2%; "high" responders) in six of 13 vessels perfused and only moderate (55.8 +/- 9.9%; "low" responders) in the remaining seven vessels. The "high" responder vessel group showed a significantly higher platelet reduction, neutrophil loss and monocyte consumption and higher C3a and TAT factor at 60 min compared with the human vessels. The "low" responder porcine vessel group also generated significantly higher TAT levels at 60 min compared with the human vessels, but lower levels compared with the "high" responder porcine vessel group. Immunohistochemical examination of perfused porcine vessels revealed binding of human IgM, IgG, IgA, C1q, C3, fibrin and platelets at 5 min. The binding of these proteins was even stronger at 15 and 60 min, and at 60 min C9 could also be detected. Addition of soluble complement receptor 1 (sCR1) to the blood resulted in a significant reduction in C3a and sC5b-9 (P = 0.046 and P = 0.046, respectively). However, sCR1 did not reduce C1q, C3c or C5 staining, but did abolish C9 binding to the endothelium. In conclusion, in vitro perfusion of porcine vessel segments with non-heparinized, fresh human blood triggered events characterizing HAR. The small quantity of blood and xenogenic tissue that is needed makes this model ideal for investigations of the mechanisms and treatments of rejections associated with xenogeneic pig-to-human xenotransplantation.

Expression of complement regulatory proteins on islets of Langerhans: a comparison between human islets and islets isolated from normal and hDAF transgenic pigs

BACKGROUND

The expression of regulators of complement activity (RCAs) on islet cells may be of great importance for protecting them against complement-mediated lysis in the immediate posttransplant period after intraportal islet transplantation. We examined porcine and human islet cells for expression of RCA. We also examined to what extent human decay accelerating factor (hDAF) is expressed on adult and fetal islet cells isolated from hDAF transgenic (TG) pigs having a high transgene expression on endothelial cells. Moreover, the susceptibility of the various types of cells to lysis in human serum and blood was investigated.

METHODS

Adult human islets (n=5), normal adult and fetal porcine islets (n=9 and n=8, respectively), and islets from adult and fetal hDAF TG pigs (n=5 and n=6, respectively) were examined. With islet single-cell suspensions and flow cytometry, adult human islet cells were examined for expression of hDAF (CD55), hCD59, and human membrane cofactor protein (hMCP; CD46), while porcine islet cells were examined for expression of pCD59 and pMCP. Islet cells from hDAF TG pigs were also examined for hDAF expression. Porcine peripheral blood lymphocytes, normal and hDAF TG porcine endothelial cell lines, a human endothelial cell line, and the human cell line U937 served as controls. Islet cytotoxicity was assayed after incubation of the islet cells with fresh human serum. Furthermore, adult islets from normal control pigs and hDAF TG pigs were exposed to fresh human blood in vitro for 60 min, and the inflammatory reaction elicited was compared between the different types of islets.

RESULTS

All human islet cell preparations expressed hCD59, two of five expressed hMCP, but none expressed hDAF. Porcine islet cells expressed both pCD59 and pMCP. Normal adult porcine islet cells exposed to fresh human serum resulted in 74+/-5.4% cell lysis (mean+/-SEM, n=16). In comparison, only 1.3+/-2.8% (n=20, P<0.001) of human islet cells were lysed in the human serum. One islet cell preparation from an hDAF TG pig expressed small amounts of hDAF. This preparation from hDAF TG pigs bound significantly less C3c than did normal control islets (mean fluorescence ratio 16+/-2.2 and 58+/-4.3, respectively; P=0.046) and were partially protected from cell lysis in fresh human serum (47+/-10% and 78+/-18% cell lysis, respectively; P=0.046). The other four preparations from hDAF TG pigs were negative for hDAF and were equally susceptible to lysis as normal control islets. All fetal pancreatic islet cells from hDAF TG pigs analyzed were negative for hDAF expression. When exposed to fresh human blood in vitro, adult and fetal islets from hDAF TG pigs elicited equally strong inflammatory changes as did the normal control islets. The inflammatory changes were characterized by activation of the complement and coagulation systems, resulting in islet damage with "dumping" of insulin into the blood.

CONCLUSIONS

Porcine and human islet cells express species-restricted complement regulatory proteins, with the human islet cells expressing mainly hCD59. A low expression of hDAF was detected on islet cells from one of five hDAF TG pigs. These islet cells displayed reduced islet cell cytotoxicity in fresh human serum. We conclude that protection from complement-mediated lysis will be important in the context of intraportal pig-to-human islet transplantation, and expression of a human RCA on islet cells should be beneficial in this context.

Effects of immunosuppressive treatment on host responses against intracerebral porcine neural tissue xenografts in rats

BACKGROUND

Embryonic xenogeneic neural tissue is an alternative for transplantation in Parkinson's disease, but immune responses limit the application. The aims of this study were to enhance the in vitro viability rates by donor tissue pretreatment; to compare the efficacy of cyclosporine A (CsA) and tacrolimus (FK) in inhibiting xenograft rejection in rats; to evaluate additional inductive therapy with prednisolone (PRE) or mycophenolate mofetil (MMF).

METHODS

Tirilazad (a lipid peroxidase inhibitor) or FK and acYVAD-cmk (a caspase inhibitor), were added to embryonic porcine ventral mesencephalic tissue and viability was assessed in vitro. Tirilazad-treated tissue was grafted to the striatum of rats that were either left untreated or immunosuppressed with FK (1 mg/kg) or CsA (15 mg/kg) alone or in combination with a 2-week PRE (20 mg/kg) or MMF (40 mg/kg) induction course. Xenograft survival and host responses were determined using immunohistochemistry.

RESULTS

Pretreatment with tirilazad enhanced tissue survival in vitro. After transplantation into untreated controls, there was no graft survival at twelve weeks. Neural cell counts were significantly improved in immunosuppressed recipients, but there were no differences between the treatment groups. Additional inductive treatment reduced the infiltration with CD4+ and CD8+ cells, and macrophage infiltration was reduced compared with animals given CsA or FK alone.

CONCLUSION

Pretreatment of the donor tissue with free-radical scavengers reduces cell loss caused by tissue trauma. Porcine neural tissue xenografts survive significantly better in animals immunosuppressed with either FK or CsA. Additional inductive treatment with PRE or MMF reduced the infiltration of host cells into the xenografts.

Diabetic rats transplanted with adult porcine islets and immunosuppressed with cyclosporine A, mycophenolate mofetil, and leflunomide remain normoglycemic for up to 100 days

BACKGROUND

Transplantation of adult porcine islets (APIs) offers a possible means of treating diabetes. However, isolating APIs has been notoriously difficult. Furthermore, islet xenograft rejection must be prevented.

MATERIALS AND METHODS

APIs were isolated by a modified automated method. API quality was assessed by static glucose stimulation (SGS), by transplantation to diabetic nude mice and by intraperitoneal glucose tolerance tests (IPGTTs). The morphologic characteristics of API xenograft rejection in rats were studied immunohistochemically. Furthermore, APIs were transplanted to diabetic rats that were either left untreated or immunosuppressed with cyclosporine A (CsA), mycophenolate mofetil (MMF) and leflunomide (LEF). B-glucose and porcine C-peptide levels were monitored and grafts were studied morphologically.

RESULTS

Large numbers of APIs were isolated. At SGS, insulin release increased significantly. All nude mice transplanted with APIs were normoglycemic within 24 hr and remained so for up to 1 year. During IPGTTs, B-glucose levels were rapidly regulated to porcine levels. In untreated rats, API xenografts were destroyed within 6 days by a cellular infiltrate consisting mainly of macrophages. In untreated diabetic rats normoglycemia was sustained for 5.5+/-0.3 days. Rats immunosuppressed with CsA+MMF+LEF remained normoglycemic for 59.6+/-11.3 days. In 3 of 11 rats, normoglycemia was sustained for up to 101 days. Porcine C-peptide was detected in serum. At recurrence of hyperglycemia, many mononuclear cells were found close to the xenografts. However, only occasional cells infiltrated the grafts and many APIs were intact.

CONCLUSIONS

Well-functioning APIs can be isolated in large numbers. API xenografts can be protected from rejection and can maintain an adequate function for up to 100 days, in rats immunosuppressed with CsA+MMF+LEF.

Clinical aspects and perspectives in islet xenotransplantation

In 1990-1993, eight diabetic renal transplant patients had porcine fetal islets injected intraportally at Huddinge Hospital in Stockholm. Four of the patients had evidence of xenograft function reflected in the excretion of small amounts of porcine C-peptide. Two patients had the porcine fetal islets placed under the capsule of a simultaneously transplanted kidney. In one of these patients, a graft biopsy specimen taken 3 weeks after transplantation revealed morphologically intact epithelial cells staining positively for insulin and glucagon. The insulin production was in all instances insufficient to affect the patient's insulin requirements. All patients formed specific xenoantibodies (mostly anti-Gal); presumably, most of the xenoislets were destroyed by rejection. On follow-up studies carried out 6-8 years after xenotransplantation, most patients still had higher-than-pretransplant levels of xenoantibodies. There was no evidence of transmission of porcine endogeneous retroviruses to the patients. All patients expressed a positive attitude toward the use of animal tissue for treatment of disease, and none of the patients regretted participating in the trial. Cell transplantation is leading the way at present for clinical xenotransplantation. The finding that complement inhibition protects intraportally injected porcine islets from an injurious incompatibility reaction holds promise for future clinical application. A similar protective effect might be achievable with the use of islets from transgenic pigs expressing human complement receptors.

Distribution of the Galalpha1-3Gal antigen in cultured adult and fetal porcine pancreatic islet cells: an immunoelectron microscopic study

The distribution of the Galalpha1-3Gal antigen (Galalpha) in cultured adult porcine islets (API) and fetal porcine pancreatic islet-like cell clusters (ICC) was studied using immunoelectron microscopy. API and ICC were cultured for 1 and 5 days, respectively, and immunogold labeled using human affinity isolated anti-Galalpha1-3Gal antibody, GS-IB4 lectin and antibodies against islet pancreatic hormones, vimentin, and von Willebrand factor. Differentiated endocrine cells were Gala-negative, but, in ICC, some immature endocrine cells were slightly Gala-positive. The Gala-expression in API was much weaker compared to ICC. In both API and ICC, the Gala antigen was expressed on duct epithelial cells, acinar cells, and endothelial cells. In ICC, strong Gala expression was observed on flattened cells covering their surfaces. These cells were identified as centroacinar cells originating from intra-islet ducts. In conclusion, although mature endocrine cells of cultured API and ICC lack the Gala-xenoantigen, several other cellular compounds are strongly Gala positive, which may contribute to xenorejection of these grafts.

A comparison of fetal and adult porcine islets with regard to Gal alpha (1,3)Gal expression and the role of human immunoglobulins and complement in islet cell cytotoxicity

BACKGROUND

It is still debated whether fetal or adult porcine islets should be the preferred choice for future clinical islet xenotransplantation. Each type of islet preparation has advantages and disadvantages compared with the other. Here we present a direct comparison between fetal and adult porcine islets with regard to Gal alpha(1,3)Gal expression, immunoglobulin and complement binding, and cytotoxicity after exposure to fresh human serum.

METHOD

Islet single cell suspensions were prepared from adult and fetal islets by trypsin digestion. Fluorescein isothiocyanate-conjugated Bandeiraea simplicifolia isolectin B4 (BS-IB4) and affinity-purified chicken anti-Gal alpha(1,3)Gal antibody was used to detect Gal alpha(1,3)Gal expression. Immunoglobulin and complement binding to the islet cells and cytotoxicity for islet cells was compared after incubation with fresh and heat-inactivated human sera and with an immune serum from a diabetic patient who received a fetal porcine islet transplant. Furthermore, two pools of human AB sera were depleted of porcine endothelial cell cytotoxic human anti-Gal alpha(1,3)Gal antibodies by absorption and were used to analyze the effect of Gal alpha(1,3)Gal antibody removal on islet cell cytotoxicity.

RESULTS

Fetal islet cells readily bound both BS-IB4 and the chicken anti-Gal alpha(1,3)Gal antibody. None of 10 adult porcine islet preparations were stained by BS-IB4. In comparison, IgY anti-Gal Ab binding was detected in two of eight adult islet isolations, whereas the other six preparations showed marginal/no binding. After incubation of fetal islet cells with fresh human serum, C3c binding was strongly positive and IgM binding variable, with occasional binding of IgG and no detectable binding of IgA. Adult islet cells were also strongly positive for C3c but did not bind detectable amounts of IgM, IgG, or IgA. Immune sera from a patient who had received fetal porcine islets showed the presence of induced antibodies that bound to fetal islet cells and to porcine peripheral blood lymphocytes, whereas binding to adult islet cells was barely detectable. Fresh human sera showed a high and similar level of complement-mediated lytic activity for both adult islet cells (78+/-22%) and fetal islet cells (75+/-16%). Cytotoxicity for fetal islet cells and peripheral blood lymphocytes was significantly reduced when the corresponding sera were depleted of anti-Gal antibodies before use (P=0.002 and P=0.003, respectively). In contrast, no difference in cytotoxicity for adult islet cells was detected when anti-Gal-depleted human sera were used.

CONCLUSION

Gal alpha(1,3)Gal expression is occasionally detectable on adult porcine islet cells, but not as readily and at a lower level, compared with fetal islet cells. Thus, as porcine fetal islets mature to adult islets, the expression of the Gal alpha(1,3)Gal epitope gradually diminishes. Consequently, cytotoxic anti-Gal alpha(1,3)Gal antibodies in human serum play an important role in the lysis of fetal but not adult porcine islet cells.

Damage to porcine islets of Langerhans after exposure to human blood in vitro, or after intraportal transplantation to cynomologus monkeys: protective effects of sCR1 and heparin

BACKGROUND

Porcine islets offer an attractive alternative to human islets in clinical islet transplantation. The preferred method of islet transplantation is intra-portal injection into the liver. We have recently shown, both in vitro with human islets and in vivo with porcine islets, that islets exposed to allogeneic blood trigger an injurious inflammatory reaction characterized by activation of both coagulation and the complement systems. We have now tested whether a similar reaction is triggered when xenogeneic porcine islets are exposed to human blood in vitro and after intraportal transplantation into primates. Furthermore, we investigated the effect of inhibiting the complement and coagulation systems.

METHOD

Islets isolated from adult and fetal porcine pancreas were perfused with fresh human blood in surface heparinized PVC tubings for 5-60 min. Blood cell counts and parameters related to coagulation and the complement system were analyzed, and islets were retrieved after the perifusion was examined by immunohistochemical method. Heparin and soluble complement receptor 1 (sCR1; TP10, 100 microg/ml) were added to the system in some experiments. Furthermore, adult porcine islets were transplanted intraportally into untreated and sCR1- (40 mg/kg BW i.v.) treated cynomolgus monkeys, and plasma insulin concentration was monitored during 60 min after transplantation.

RESULTS

Porcine islets perifused with human blood triggered an immediate inflammatory reaction, characterized by a rapid consumption and activation of platelets, consumption of neutrophils and monocytes, activation of the coagulation and complement systems, and release of large amounts of insulin. Islet morphologic analysis revealed damaged islets embedded in clots and infiltrated with CD11+ leukocytes. C3a and C5b-9 was deposited on the islet surface, but human immunoglobulin was not. Complement inhibition with sCR1 reduced insulin release significantly. Intraportal islet transplantation into untreated cynomolgus monkeys resulted in a marked and rapid increase in plasma insulin concentration indicative of islet damage. Pretreatment of the monkeys with sCR1 resulted in significantly less insulin release than in untreated control monkeys.

CONCLUSION

Exposure of isolated xenogeneic islets of Langerhans to blood, both in vitro and in vivo, resulted in acute islet damage. Complement and platelets seem to have a central role in the reactions described. Strategies to efficiently inhibit these reactions will be crucial for clinical intraportal islet xenotransplantation to be successful.

Isolated human islets trigger an instant blood mediated inflammatory reaction: implications for intraportal islet transplantation as a treatment for patients with type 1 diabetes

Islet transplantation offers a logical means to treat insulin-dependent diabetes. However, for reasons poorly understood, the clinical results with islet transplantation have been vastly inferior to those obtained with whole organ pancreas transplantation. The conventional technique for transplanting isolated islets is by intraportal injection, with the islets being trapped in the liver. Human islets exposed to human blood trigged an "instant blood mediated inflammatory reaction", IBMIR, characterised by platelet consumption, and activation of the coagulation and complement systems. The islets became surrounded by clots and infiltrated with leukocytes, and there was evidence of islet damage as reflected in insulin dumping. When heparin and a complement inhibitor (SCRI), was added to the system, IBMIR was suppressed and islet damage reduced. After intraportal pig-to-pig islet intraportal allotransplantation similar morphological changes was found, corroborating the in vitro findings. Thus, IBMIR inflicts a significant damage to human islets exposed to human blood and IBMIR will also, most likely, enhance the subsequent specific, cell mediated, rejection. Platelet and complement activation seem to be the most important factors in the pathogenesis of IBMIR. The results presented strongly suggest that IBMIR observed both in vitro and in vivo when isolated islets come in contact with blood could provide an explanation for the unsatisfactory results seen in clinical islet allotransplantation.

Incompatibility between human blood and isolated islets of Langerhans: a finding with implications for clinical intraportal islet transplantation?

The remarkable difference in success rates between clinical pancreas transplantation and islet transplantation is poorly understood. Despite the same histocompatibility barrier and similar immunosuppressive treatments in both transplantation procedures, human intraportal islet transplantation has a much inferior success rate than does vascularized pancreas transplantation. Thus far, little attention has been directed to the possibility that islets transplanted into the blood stream may elicit an injurious incompatibility reaction. We have tested this hypothesis in vitro with human islets and in vivo with porcine islets. Human islets were exposed to nonanticoagulated human ABO-compatible blood in surface-heparinized polyvinyl chloride tubing loops. Heparin and/or the soluble complement receptor 1 (sCR1) TP10 were tested as additives. Adult porcine islets were transplanted intraportally into pigs, and the liver was recovered after 60 min for immunohistochemical staining. Human islets induced a rapid consumption and activation of platelets. Neutrophils and monocytes were also consumed, and the coagulation and complement systems were activated. Upon histological examination, islets were found to be embedded in clots and infiltrated with CD11+ leukocytes. Furthermore, the cellular morphology was disrupted. When heparin and sCR1 were added to the blood, these events were avoided. Porcine islets retrieved in liver biopsies after intraportal islet allotransplantation showed a morphology similar to that of human islets perifused in vitro. Thus, exposure of isolated islets of Langerhans to allogenic blood resulted in significant damage to the islets, a finding that could explain the unsatisfactory clinical results obtained with intraportal islet transplantation. Because administration of heparin in combination with a soluble complement receptor abrogated these events, such treatment would presumably improve the outcome of clinical islet transplantation by reducing both initial islet loss and subsequent specific immune responses.

Diagnosis of type 1a and type 1c glycogen storage diseases in adults

The hepatic glucose-6-phosphatase system was studied with a novel microanalytical technique in adult patients undergoing liver biopsy. 4 patients were diagnosed as having type 1 glycogen storage disease (GSD). 3 of these patients, who had hypoglycaemic symptoms, had variations of type 1a GSD, which is caused by a defect in the hepatic microsomal glucose-6-phosphatase enzyme. The fourth, with hepatomegaly and no hypoglycaemic symptoms, had a normal glucose-6-phosphatase enzyme but a defect in the hepatic microsomal phosphate/pyrophosphate translocase T2; this is the first report of an adult with type 1c GSD. Adult type 1 GSD should be considered in patients with unresolved hypoglycaemic symptoms and/or unresolved hepatomegaly.