摘要:

Background.Factors that contribute to xenograft (Xg) rejection were investigated in complement C6-deficient (C-) PVG rats.Methods.First and second hamster hearts were transplanted in C6-deficient and C6-sufficient PVG rats. Xenoantibody (XAb) formation, hemolytic C (CH50) activity and immunohistochemistry were studied.Results.PVG C6-deficient rats rejected Xgs 3 days later than PVG C6-sufficient rats. Surprisingly, C activation participated in the rejection in PVG C- rats, as shown by partially recovered serum CH50 levels and deposition of C factors in the Xgs. As we found that cultured endothelial cells produced C6 in vitro, we hypothesized that Xg endothelial cells corrected the C6 defect in PVG C- rats. This was probably induced by IgM XAbs as: (1) it did not occur in immunosuppressed PVG C- rats in which XAb formation was prevented, and (2) transfer of IgM XAbs to naive, xenotransplanted PVG C- rats accelerated the recovery of CH50 and concomitantly Xg rejection. Thirty days after rejection of a first Xg, when no IgM XAbs or CH50 activity but high levels of IgG XAbs were detected in PVG C- rats, second Xgs underwent a hyperacute rejection. This time, complement was not involved, as no serum CH50 nor C deposition was found in the Xg. Instead, IgG antibody-dependent cellular cytotoxicity was involved as: (1) IgG XAbs were deposited in the Xg and (2) hyperacute rejection was induced in naive PVG C- rats by transfer of IgG XAbs, and (3) this rejection was delayed to 5±3 days if the adoptive hosts were first irradiated.Conclusions.In the face of a defect of host C factors, IgM XAb may induce cells of the Xg to secrete C factors which may correct the C defect of the host. Even if activation of lytic C can be prevented, IgG XAb may still provoke an acute Xg rejection by antibody-dependent cellular cytotoxicity.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background.The possibility of transplanting microencapsulated pancreatic islets into patients with insulin-dependent diabetes mellitus, either as allografts or xenografts, has attracted great interest. A critical evaluation of the results obtained reveals that the success has been very limited. The aim of the present study was to compare the in vitro function of microencapsulated islets obtained from adult humans, adult mice, adult rats, and fetal pigs.Methods.Human pancreatic islets were isolated at β-Cell Transplant in Brussels, Belgium, and sent to the Department of Medical Cell Biology, Uppsala University in Uppsala, Sweden. Rat and mouse pancreatic islets and fetal porcine islet-like cell clusters (ICC) were prepared in Uppsala. All groups of islets were subsequently sent to the Department of Biotechnology, Norwegian Institute of Biotechnology, University of Trondheim, Trondheim, Norway. After 1 day in tissue culture, the islets were microencapsulated in alginate then cultured and sent back to Uppsala the next day. After either overnight culture (day 1) or 6 days of culture (day 6), the microencapsulated islets were examined for their insulin content and insulin release. Nonencapsulated islets from the same isolations were used as controls.Results.The insulin content of rodent and human islets was not affected by microencapsulation, whereas porcine ICC showed a diminished insulin content. Microencapsulated porcine ICC also had a marked reduction in their insulin secretion in response to stimulation with glucose or glucose + theophylline both on days 1 and 6 in tissue culture. Mouse islets showed a reduced insulin response at both time points. Rat islets exhibited an inhibition of insulin secretion on day 1, but this had been restored by day 6. Human islets had well-preserved insulin secretion after both days 1 and 6. Microencapsulated human islets showed a normal morphology 3-4 weeks after intraperitoneal transplantation to nude mice.Conclusions.Pancreatic islets isolated from human, rat, and mouse donors show a glucose-stimulated insulin release in vitro after microencapsulation and repeated transports between laboratories. The insulin secretory capacity of microencapsulated human and rat islets was preserved best, whereas mouse islets and particularly fetal porcine ICC were impaired by microencapsulation.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background.Hepatocyte transplantation could be an alternative to whole organ transplantation to correct enzymatic disorders. To this end, it would be of major importance to use xenogeneic cells without immunosuppression. The aim of this study was to investigate the survival and metabolic activity of encapsulated xenogeneic hepatocytes in the absence of immunosuppression. For this purpose, we used Gunn rats genetically incapable of bilirubin conjugation.Methods.Xenogeneic (from guinea pigs) and allogeneic (from Lewis rats) hepatocytes (2×107) were isolated, macroencapsulated in hydrogel hollow fibers made with an acrylonitrile-sodium methallyl-sulfonate copolymer, and transplanted into the peritoneum of Gunn rats without any immunosuppression. Plasma bilirubin levels were evaluated weekly. Bilirubin conjugates in bile and cell morphology were studied after 5 and 12 weeks, respectively.Results.In Gunn rats transplanted with xenogeneic hepatocytes, a significant decrease in the serum bilirubin level was observed between 3 and 9 weeks after transplantation when compared with controls transplanted with empty hollow fibers: it fell to 62% of the initial level at weeks 5-7 (P<0.01). A comparable result was observed in Gunn rats transplanted with encapsulated allogeneic cells. Bilirubin conjugates were observed in bile samples of rats transplanted with encapsulated hepatocytes. After explantation, hollow fibers appeared intact with minimal fibrosis. Cell viability and hepatocyte morphology were preserved.Conclusions.These results indicate that macroencapsulated xenogeneic hepatocytes can survive and remain functional for more than 2 months when transplanted in vivo in the absence of any immunosuppression.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background.The reconstruction of massive osteochondral defects extending to weight-bearing joints remains a surgical challenge. Total knee joint transplantation has been performed experimentally, but these studies lacked prospective evaluation of functional outcome, graft vascularization, and graft viability.Methods.Replantation and transplantation of vascularized knee joints was performed in dogs (n=4 per group), comparing functional and morphological results during a 6-month follow-up.Results.All replant recipients and three transplant recipients survived the 6-month follow-up period. At this time, duplex sonography and angiography revealed patent anastomoses in all animals. Increases in volumetric flow rates and vascular collateralization were observed in allografts, as compared with replanted joints (100±16 ml/min vs. 31±15 ml/min at 6 months after transplantation). Bone fusion at the graft-host interface was verified by fluorography in all animals at 3 months after transplantation. Six months after transplantation, microradiographies and computerized tomographies revealed spongialization of the cortical bone and filling of the medullary space by trabecular bone in transplanted joints. Such alterations were not detectable in replanted joints. Chondrocyte viability exceeded 80% in all but one transplanted joint. Lymphocyte infiltration of synovia and arterial walls was detected in all transplanted joints, suggesting the presence of chronic rejection. Weight-bearing capacity recovered in all replanted animals (weight-bearing index before transplantation: 0.499±0.080; 6 months after transplantation: 0.38±0.16) but only in two of four transplanted animals (weight-bearing index 6 months after transplantation: 0.37, 0.28, and 0.00).Conclusions.These data demonstrate the potential of joint grafting and the critical dependence of allotransplantation on the control of rejection.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background.We have previously demonstrated in vitro that the methylxanthine derivative A802715 suppresses the cyclosporine (CsA)-resistant “signal two”-dependent pathway of T cell activation and hence acts synergistically with CsA. Here, this synergism was further investigated in vivo in rats.Methods.Primary cardiac allografts were placed in the neck, and secondary grafts were transplanted intra-abdominally. A802715 was given orally for 30 days or by continuous intravenous infusion via a mini-osmotic pump for 2 weeks. CsA was given orally for up to 30 days. T cell responses were examined in vitro using mixed lymphocyte reaction, concanavalin A whole blood, and cell-mediated lympholysis assays.Results.In a major histocompatibility complex incompatible WKAH→PVG combination, neither oral CsA (7.5 mg/kg/day) nor oral A802715 (100 mg/kg/day) was able to prolong graft survival. However, a combination of both drugs, given at the same dose, sustained graft survival during treatment. A similar synergism was not obtained with pentoxifylline, another methylxanthine derivative. The synergism between A802715 and CsA could be further increased by using a continuous intravenous infusion of A802715, since (1) lower doses of A802715 (20 mg/kg/day) and CsA (5 mg/kg/day) could be used, and (2) six of seven grafts survived permanently. In a major histocompatibility complex compatible Wag/Rij→R/A combination, similar synergistic effects and permanent graft survival could also be obtained by oral A802715 (100 mg/kg/day) in combination with a low dose of CsA (2.5 mg/kg/day). In both strain combinations, long-term survivors accepted donor-type but rejected third-party second grafts in the absence of immunosuppression. This specific tolerance was not related to clonal deletion nor anergy, as recipient lymphocytes proliferated normally in the anti-donor mixed lymphocyte reaction. Instead, a defect in generating specific cytotoxic T lymphocytes was involved.Conclusions.A802715 synergizes with CsA in vivo to induce specific transplantation tolerance and hence should be considered as a promising new immunosuppressant.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background.Rejection episodes (RE) exert a detrimental influence on long-term kidney graft outcome. However, the impact of the severity of those RE on graft survival and the factors that could predict this impact are ill defined. The present retrospective study was undertaken on adult patients who received 582 cadaver kidney transplants at our center during the last 12 years, to assess the impact on graft survival of RE occurring during the first year after transplantation and to uncover the factors associated with the severity of those RE.Methods.Three grades of rejection were defined: (1) rejection without loss of graft function (benign rejection); (2) rejection followed by partial loss of graft function (severe rejection); and (3) rejection with return to dialysis (irreversible rejection). The grafts were distributed among four groups: (1) grafts free of rejection; (2) grafts with benign RE (only grade 1 RE); (3) grafts with severe RE (one or more grade 2 RE); and (4) grafts with irreversible (grade 3) RE.Results.Multivariate analyses revealed that (1) the occurrence of RE during the first posttransplant year (group 1 versus groups 2, 3, and 4) was significantly associated with primary immunosuppression with CsA rather than with OKT3 monoclonal antibody, the number of HLA-B + DR mismatches, and the younger recipient's age; (2) in patients with rejection, OKT3 monoclonal antibody prophylaxis was less often used in patients with irreversible RE (group 4) than in those with reversible RE (group 2, benign, and group 3, severe); and (3) no single factor was able to differentiate patients with benign RE (group 2) from those with severe RE (group 3). For grafts still functioning 1 year after transplantation, long-term graft survival was similar in grafts with either no RE or benign RE, but it was significantly lower (P<0.0001) in grafts with severe RE: 8-year survival rates were 89% and 60%, respectively. The decline in graft survival after 1 year was significantly correlated with the serum creatinine value but not with the dose of cyclosporine at 1 year.Conclusion.Benign RE occurring during the first year after transplantation and resulting in no loss of graft function do not exert a detrimental influence on long-term kidney graft outcome. In contrast, the prognosis of grafts with severe RE during the same period of time is much poorer.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background.During the 12th International Histocompatibility Workshop, a collaborative study between 35 laboratories was conducted on a group of highly allosensitized patients who had received a kidney transplant from 1981 to 1995. The major goal of the study was to assess how serum screening against a large cell panel could determine donor HLA mismatch acceptability in relation to graft outcome.Methods.Twenty laboratories participated in an extensive screening of 92 high panel-reactive antibody (PRA) sera from patients at 29 transplant centers worldwide; each patient had received a kidney allograft from an HLA-A,B mismatched unrelated donor. Screening was done by complement-dependent lymphocytotoxicity and antihuman globulin augmentation techniques using a common protocol and shared standardized reagents. After an extensive quality-control assessment, we selected data from 14 participants who had screened the sera against a combined panel of 535 HLA-typed cells.Results.With the 2×2 table-based Multiscreen computer program, we could readily determine for virtually every patient the significant correlations between serum reactivity and the presence of panel cell markers, including private and public HLA-A,B epitopes and amino acid residues assigned from published sequencing data. Donor mismatch acceptability was assessed at the amino acid residue level. In the complement-dependent lymphocytotoxicity (n=49; PRA=84.1±12.1%) and antihuman globulin (n=60; PRA=92.5±5.8%) groups, the 3-month graft survivals were 28% and 30% lower for unacceptable residue mismatches.Conclusions.These studies underscore the importance of a comprehensive serum screening analysis in the selection of appropriately mismatched donors for highly sensitized transplant patients.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background.Monocytes-macrophages are found within kidney allografts during the first days after surgery, where they perform “housekeeping” tasks, participate in postreperfusion injury, and act as antigen-presenting cells, as well as become involved in the effector phase of acute rejection. They also seem to play a prominent role in chronic rejection. We quantified their presence in fine-needle aspiration biopsies and studied the growth factors that, we hypothesized, would mark the different implications of the presence of monocytes-macrophages.Methods.Fine-needle aspiration biopsies were obtained from 56 adult renal transplants and analyzed for CD14+using the alkaline phosphatase-anti-alkaline phosphatase procedure. Thirty-three patients were studied on the production of interleukin (IL)-1 receptor antagonist (IL-1ra), IL-6, IL-8, macrophage colony-stimulating factor, monocyte chemotactic protein 1, and macrophage inflammatory protein 1α by aspiration biopsies cultures using enzyme-linked immunosorbent assay techniques.Results.CD14+cells were present at significantly higher numbers in steroid-resistant acute rejections but also during the first days after surgery, especially if acute tubular necrosis was present. We found a significantly higher production of IL-1ra by rejection-free patients compared with acutely rejecting patients, and this difference was already established on day 7 after surgery (10±10.5 days before rejection).Conclusions.Monocytes-macrophages are present at higher numbers in aspiration biopsies of kidney transplant patients suffering either acute tubular necrosis or steroid-resistant rejections, but they are present during the first days after transplant in stable patients, too. The production of IL-1ra is significantly up-regulated in stable patients, which suggests that monocytes-macrophages may constitute an early key factor in the down-regulation of the anti-allograft immune response.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background.Recipient antidonor cytotoxic T-cell activity has been associated with graft loss and acute rejection in renal allograft recipients. The role of immunologic mechanisms in the development of chronic graft rejection is controversial. We analyzed all living related renal transplants performed at Children's Hospital (Boston, MA) from 1983 to 1995 to assess whether cell-mediated cytotoxicity, determined in vitro and measured before transplantation, was predictive of chronic rejection.Methods.Eighty-three patients were studied retrospectively. Fifty-seven patients with one haplotypematched renal transplants from living related donors were studied to determine the association between cell-mediated lympholysis (CML) level, acute rejection, chronic rejection, and graft failure. Acute rejection was defined by the decision to treat. Chronic rejection was defined by histology and/or the absolute serum creatinine value using an increasing serum creatinine level >1.0 mg/dl for children less than 3, a creatinine level >1.5 mg/dl for children between 3 and 10 years of age, and a creatinine level >2.0 mg/dl for children above 10 years of age. Return to dialysis or retransplantation was considered graft failure.Results.Of the 57 haploidentical patients, there were 33 males and 24 females. The mean age at transplant was 11.1 years (SD=6.7). Twelve patients developed chronic rejection, 24 patients developed acute rejection, and 7 patients had graft failure. Pretransplant cytotoxic T lymphocyte activity was associated with chronic rejection (P=0.001) and graft failure (P=0.013) but only marginally with acute rejection (P=0.058). Controlling for age and sex, Cox's proportional hazards model revealed that CML level was predictive of time to chronic rejection (P<0.01) but not acute rejection (P=0.11). It was estimated that every 1-unit increase in CML level raises the monthly risk of chronic rejection by 7%. Ten children received HLA-identical kidneys from their siblings. There were no episodes of chronic rejection after 5 years. Two patients with high CML levels had episodes of acute rejection; both patients responded to treatment.Conclusion.Our data demonstrate an association between pretransplant cell-mediated cytotoxicity and the occurrence of chronic rejection in living related one-haploidentical renal transplants in pediatric patients.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID

摘要:

Background.A comparison of the oral bioavailability of cyclosporine from the original formulation (CsA) and from the new formulation, cyclosporine for microemulsion (CsA-ME), was made in pediatric maintenance liver transplant patients within two age groups (group 1, ages 1-5 years; group 2, ages 6-17 years) in an open-label, multicenter, randomized crossover trial. All patients were at least 6 months past transplantation and were receiving CsA maintenance therapy.Methods.In study period 1 (days 1 through 14), patients were administered either CsA or CsA-ME at the same b.i.d. dosage as their maintenance therapy. Upon entry into period 2 (days 15 through 28), patients were converted to the alternate formulation at a 1:1 mg dose ratio. On day 29, all patients returned to the CsA treatment administered at study entry, with follow-up on day 35. Dosage adjustments were not allowed with either CsA or CsA-ME. Twelve-hour pharmacokinetic profiling was performed at the end of periods 1 and 2.Results.Both the mean area under the concentration-versus-time curve and the mean maximum blood concentration of cyclosporine-both normalized for dose-were significantly increased: by 66% and 109%, respectively, in patients receiving CsA-ME compared with those receiving CsA in group 1 and by 39% and 75%, respectively, in group 2. During this study, liver function remained stable, and serum creatinine and blood pressure did not differ significantly between treatment groups.Conclusions.This study shows increased bioavailability in all patients converted to CsA-ME, with the greatest increase seen in patients with the lowest initial cyclosporine bioavailability. The tolerability was similar between the two formulations during this study.

ISSN:0041-1337    

出版商:OVID    

年代:1997

数据来源: OVID