ISSN:0041-1337    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0041-1337    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.Although an attractive alternative to daily insulin therapy, allogeneic pancreatic islet transplantation has yielded suboptimal results in clinical trials, in contrast to islet allotransplantation in animal models, which have demonstrated consistent success. The successful transplantation of isolated islets to the thymus, with a single concomitant dose of antilymphocyte serum, has been demonstrated in rodents, and more significantly, such intrathymic islet allografts have been shown to induce recipient tolerance toward subsequent extrathymic donor strain islet allografts. Intrathymic islet autotransplantation has been pursued, as a prelude to studies of allogeneic IT islet transplantation and tolerance induction, in canine, porcine, and non-human primate models, to assess the large animal thymus as a site capable of supporting a viable islet graft. However, little functional or histological evidence has established definitive survival of islets transplanted within the thymus of a phylogenetically advanced species, which may be requisite to tolerance induction. This study describes the successful intrathymic autotransplantation of isolated islets using a canine model.Methods.Purpose-bred juvenile dogs, aged 4–6 months, underwent partial (n=4), or total pancreatectomy (n=11), and transplantation of autologous islets. The pancreas (or pancreatic limb) was distended with collagenase solution, and digested using a modification of the semiautomated system of Ricordi. Islets were purified by discontinuous gradient centrifugation, using Euroficoll (ficoll in Euro-Collin’s kidney preservation solution). Partially pancreatectomized canines underwent IT transplantation of purified autologous islets (8000±4000 IEs), and were killed 8 weeks posttransplant. Totally pancreatectomized canines underwent transplantation of autologous islets to the liver (via portal vein embolization, n=5, IPO group) or the thymus (via direct IT injection, n=6, IT group), and were serially evaluated for a period of 8 weeks posttransplant to assess fasting blood glucose (FBG), serum insulin (SI) levels, and i.v. glucose tolerance (IVGTTs). K values (defined as the %-decrease/minute of the logeof blood glucose values) were calculated from IVGTT results.Results.After autotransplantation in this cohort of animals, five of five IPO, and three of six IT islet recipients, remained normoglycemic (mean FBG≤250 mg%) immediately posttransplant, and all recipients exhibited significantly elevated SI levels compared to apancreatic controls (n=10, followed 72 hr postpancreatectomy). Normal k values (=−1.1) were observed in two of five IPO, and in one of six IT recipients, 8 weeks after transplantation, and thymic tissue insulin content was increased compared to non-islet-bearing thymi (93.7±48.6 ng/g tissue vs. 0.7±0.4 ng/g tissue). At 8 weeks posttransplantation thymi from both partially and totally pancreatectomized animals were resected and processed for histological examination. Microscopic analysis of islet-bearing thymi revealed positive staining for islet-specific hormones (insulin and glucagon) within all IT recipients., Identification of islets within thymi of hyperglycemic IT recipients was problematic as islet &bgr; cells were highly degranulated as a result of the recipients glycemic state.Conclusions.These results indicate that autologous islets, transplanted to the canine thymus, engraft, function, and survive for up to 8 weeks after islet autotransplantation to the canine thymus and establish the feasibility of intrathymic islet transplantation in a phylogenetically advanced animal model. The ability of islets to survive within the thymic environment for a period of at least 8 weeks after transplantation suggests that the successful induction of specific unresponsiveness secondary to intrathymic transplantation will not be impaired or limited by the inability of a viable islet mass to survive within the thymus for a sufficient period.

ISSN:0041-1337    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.Both animal models and clinical outcomes studies of transplantation suggest that antigen-independent mechanisms can alter graft survival and function. It has been suggested that antigen-independent processes interact with alloantigen-specific responses to augment the rejection reaction. A major link between antigen-specific adaptive immunity and pro-inflammatory stimuli is innate immunity. During transplantation, innate immunity may be stimulated by multiple factors, including ischemia, reperfusion, sterile injury, systemic stress, and cell death.Methods.We investigated the hypothesis that transplantation induces a potent innate immune response in a murine model of vascularized solid organ transplantation. In our studies, we analyzed three experimental groups: (a) alymphoid group in which both the donor and recipients strains lacked an adaptive immune response due to deletion of the recombinase activating gene, thus blocking production of both T cell and B cell antigen receptors; (b) syngeneic group in which the donors and recipients were genetically identical; and (c) allogeneic group in which the donors and recipients had a complete MHC mismatch. To analyze a large number of parameters we determined the level of expression of a panel of cytokines, chemokines, receptors, and cell surface markers by RNase protection assays. In addition, serum cytokines were determined by ELISA and the infiltration of inflammatory cells was assessed by histology.Results.Our results showed macrophage infiltration and up-regulation of multiple cytokines, chemokines, and chemokine receptors within the first day after transplantation in all groups, including the syngeneic and alymphoid recipients.Conclusions.Our study demonstrated a robust innate immune response that is independent of adaptive immunity and natural killer cell responses.

ISSN:0041-1337    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.In rodents it has been demonstrated that blockade of the CD40-CD154 (CD40L) pathway at the time of donor-specific blood transfusion (DST) can result in indefinite graft survival. Because it has been reported in the past that DST in monkeys can have a favorable effect on graft outcome and that blockade of the CD40-CD154 pathway can lead to prolonged kidney graft survival in monkeys, we have combined anti-CD154 treatment with DST in a monkey kidney graft model. The aim of this study was to investigate the immunosuppressive potential of blocking the CD40-CD154 interaction at the time of a DST in rhesus monkeys.Methods.One donor-derived blood transfusion was given on day −15 after the first anti-CD154 injection. The anti-CD154 antibody was given on days −15, −13, −11, −9, and −7. The kidney was transplanted on day 0. Cyclosporine was given after kidney trans-plantation.Results.No major difference in graft survival was observed between the groups. The animals died due to grade II acute rejection. At the time of transplantation, no antibody response could be detected directed against donor antigens. After transplantation, all animals surviving for more than 3 weeks had antidonor antibodies. There were no differences in the intragraft events analyzed by real time reverse transcriptase-polymerase chain reaction.Conclusions.DST under the cover of relatively high levels of anti-CD154 failed to result in prolonged graft survival or prevent the formation of antidonor antibodies, when cyclosporine was given after transplantation.

ISSN:0041-1337    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.Pregnancy after allotransplantations is becoming a more common occurrence, and the immunosuppressant of choice is cyclosporine (CsA) for these patients. Consequently, the effect of CsA on prenatal and postnatal immune development and function in the infant is an increasingly important clinical issue. The purpose of this study was to evaluate the potential problems of maternal CsA exposure on neonatal T-cell maturation and proliferation after lactational transfer of CsA in an animal model.Methods.CsA was administered daily (subcutaneous) for 20 days during lactation, beginning the day of parturition using two dose levels (15 and 25 mg/kg body weight/day) in conjunction with saline controls.Results.Considerable amounts of CsA were passed to the newborn rats with neonatal blood levels equal to that of the mothers for the 25-mg/kg/day dose and 55% for the 15 mg/kg dose. There was a significant reduction in thymus/body-weight ratio and thymus cellularity for the pups born to mothers dosed at 15 or 25 mg/kg/day of CsA. The thymus from the CsA-exposed pups showed an almost complete loss of the medullary region with no apparent change in the thymic cortex. The CsA-treated mothers and their pups (15 and 25 mg/kg/day dose) had a significant increase in the percentage of CD4+CD8+thymocytes and a significant decrease in the percentages of CD4+, CD3hi, and T-cell receptor (TCR)hi thymocyte phenotype subsets and CD4/CD8 ratios. Thymocyte proliferative responses to concanavalin A + interleukin-2 were also significantly decreased in the mother and pup after both doses of CsA. In contrast to the mothers that showed no change in splenocyte proliferative responses, their pups showed decreased responses at both the 15- and 25-mg/kg doses. All immune alterations due to CsA lactational exposure in the pups were back to control levels after 30 days of postweaning CsA cessation.Conclusions.This study clearly demonstrates that neonatal exposure to CsA via lactational transfer can cause significant alterations in T-cell maturation and inhibition of lymphoproliferative responsiveness to mitogen activation. Although the CsA blood level in human transplant patients is normally much lower, this data indicate a potential for increased risk to opportunistic infections due to altered immune components in babies exposed to long-term CsA.

ISSN:0041-1337    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.Tolerance to organ allografts in primates including man has been elusive, although in rodents and pigs tolerance can be achieved to organ allografts with relatively short courses of immunosuppressive treatment. In all varieties of graft acceptance that do not require full-dose maintenance immunosuppression, immunological engagement of donor and recipient and an early unstable period have been observed. On the basis of the hypothesis that elimination of aggressive T cell function should tip the balance in favor of an operationally tolerant state, experiments have been performed in monkeys allowing recipient–donor interaction before T-cell ablation and a short course of immunosuppression.Methods.Rhesus monkeys received an allogeneic kidney graft from a MHC-mismatched donor. The animals either received anti-CD3 immunotoxin (FN18-CRM9) alone, started 2 days after transplantation, or in combination with a short course of cyclosporine (CsA) and/or rapamycin (RAPA), started at 5 days after transplantation. Kidney function was followed by monitoring serum creatinine levels and regular biopsies. Humoral and cellular antidonor immunity was tested in vitro before and at several time points after transplantation.Results.Graft survival of monkeys that received CsA alone (mean survival time (MST)=29.3) was significantly prolonged compared with the controls (MST=6). FN18-CRM9 treatment alone also resulted in prolonged graft survival (MST=29.4). The combined treatment of FN18-CRM9 and CsA and/or RAPA resulted in prolonged graft survival after all immunosuppression was stopped (MST=207.8).Conclusions.It seems feasible to postpone immunosuppression posttransplantation and yet prevent allograft rejection without the need of permanent immunosuppression.

ISSN:0041-1337    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.Hyperacute rejection of solid organ pig xenografts in nonhuman primates has been overcome by using donors transgenic for human complement regulatory proteins, but grafts are still susceptible to humoral (antibody-mediated) rejection. We investigated whether circulating xenoreactive antibodies are a useful indicator of this xenograft rejection.Methods.Five assays were employed in a retrospective analysis on 20 selected cynomolgus monkey recipients of renal xenografts transgenic for human decay-accelerating factor, with survival between 4 and 60 days. The assays included hemolytic and hemagglutination assays and the measurement of immunoglobulin (Ig)G and IgM binding to porcine endothelial cells and leukocytes, and to the Gal&agr;1-3Gal trisaccharide (Gal) antigen. To assess non-Gal-directed antibodies, sera were absorbed with a Gal-coated resin. A predictive value was defined as an increase in antibody levels before a decline in graft failure (>20% increase in creatinine levels) and humoral rejection in graft pathology.Results.Data on hemolytic anti-pig antibody correlated with those on IgM antibody to endothelial cells, leukocytes, and Gal. In absorbed sera IgM and IgG antibody to endothelial cells and leukocytes correlated with each other, indicative for an elicited antibody response to non-Gal antigens. Sixteen animals showed humoral rejection, and in all but two animals one or more assays was considered of predictive value. On the other hand, increased antibody levels were noted in two animals without signs of rejection in graft pathology and in two cases with cellular xenograft rejection.Conclusions.It is recommended to use multiple assays (preferably hemolytic, anti-Gal, and anti-endothelial cell) to be able to fully monitor the peripheral antibody responses in pig-to-primate xenograft recipients.

ISSN:0041-1337    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.Hepatocyte transplantation is an attractive treatment for various liver diseases. The intraportal route of transplantation is favored, but little information is available on the possible adverse effects in this technique. We investigated the influence of intraportal loads of hepatocytes on portal, pulmonary, and systemic hemodynamics in 13 pigs.Methods.Under general anesthesia, pigs were provided with an arterial line, a Swan-Ganz catheter, and two intraportal catheters, one for cell infusion and one for heparin infusion and portal pressure measurement. Pig hepatocytes were infused at a rate of 25 million cells/min.Results.The first six animals were used to develop the infusion technique. In the last seven animals, portal pressure increased linearly with cell load upon infusion of 400–2400×106hepatocytes (r2=0.704;P<0.05). Portal flow measured by Doppler sonography decreased by 23–66% below basal values. An inverse linear relationship was found between portal pressure and portal flow (r2=0.679;P<0.05), portal flow approaching zero for portal pressure >40 mmHg. Pulmonary arterial pressure increased by 11–62%. AST increased up to 10-fold, and platelets decreased by 22–58%. Hepatocytes-containing thrombi were present in segmental and in smaller portal branches. Hepatocytes were always identified in lung sinusoids 48 hr after infusion, and a small basal pulmonary infarction was found in one animal.Conclusions.These data suggest that up to 2.4% of total hepatocyte mass can be infused in this large animal model. However, the risk of significant thrombotic complications should be considered for clinical applications.

ISSN:0041-1337    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Background.The ability to effectively utilize kidneys damaged by severe (2 hr) warm ischemia (WI) could provide increased numbers of kidneys for transplantation. The present study was designed to examine the effect of restoring renal metabolism after severe WI insult during ex vivo warm perfusion using an acellular technology. After warm perfusion for 18 hr, kidneys were reimplanted and evaluated for graft function.Methods.Using a canine autotransplant model, kidneys were exposed to 120 min of WI. They were then either reimplanted immediately, hypothermically machine perfused (4°C) for 18 hr with Belzer’s solution, or transitioned to 18 hr of warm perfusion (32°C) with an acellular perfusate before implantation.Results.Warm perfused kidneys with 120 min of WI provided life-sustaining function after transplantation, whereas the control kidneys immediately reimplanted or with hypothermic machine perfusion did not. The mean peak serum creatinine in the warm perfused kidneys was 3.7 mg/dl, with the mean peak occurring on day 2 and normalizing on day 9 posttransplant.Conclusions.These results indicate that 18 hr of ex vivo warm perfusion of kidneys is feasible. Furthermore, recovery of renal function during warm perfusion is demonstrated, resulting in immediate function after transplantation. The use of ex vivo warm perfusion to recover function in severe ischemically damaged kidneys could provide the basis for increasing the number of transplantable kidneys.

ISSN:0041-1337    

出版商:OVID    

年代:2002

数据来源: OVID