摘要:

Increasingly strong medical and political pressures are stimulating consideration of the transplantation of baboon organs and cells into humans. Critical to the success of these xenotransplants is management of the immune system such that graft rejection and, in the case of bone marrow transplantation, graft-versus-host disease do not result in transplant failure. The polymorphic products of the major histocompatibility complex (MHC) are the primary barrier to successful allotransplantation, and here we describe class I MHC molecules from the baboon (Papio anubis) to gain an understanding of how similarities and differences between baboon and human MHC molecules might affect xenograft survival and function. Comparative analyses of our five novel baboon class I molecules with defined HLA class I molecules demonstrate that the baboon and human molecules are up to 90% identical. Disparity between baboon class I proteins and their human homologues lies predominately at positions in the antigen-binding groove, while C-terminal portions of the class I heavy chain are more conserved between the two species. Such concentration of cross-species differences within the α1 and α2 domains involves a majority of substitutions at positions demonstrating polymorphism in human alleles; the location of substitutions distinguishing baboon and human molecules thus resembles the positioning of human class I allopolymorphisms. Because this preliminary characterization indicates that both baboon and human T cells will be restricted by xenogeneic class I molecules, immune responses triggered during baboon-to-human transplantation should mimic those arising during MHC mismatched human allotransplantation.

ISSN:0041-1337    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Allograft rejection is dependent on T cell activation, which requires both the engagement of the T cell receptor by antigen in the context of the MHC molecule and costimulatory signals delivered by cell surface molecules such as the B7-CD28/CTLA4 pathway. CTLA4-Ig is a fusion protein that blocks this pathway and has previously been shown to prolong both allograft and xenograft survival. The current study demonstrates markedly prolonged murine cardiac allograft survival and specific prolongation of secondary skin grafts using a combination of CTLA4-Ig plus donor bone marrow.A role for hematopoietic chimerism in the establishment of CTLA4-Ig-induced transplantation tolerance was investigated using reverse transcriptase polymerase chain reaction analysis of recipient tissues. Expression of donor-specific MHC class II transcripts in both peripheral and lymphoid tissues was demonstrated at greater than 200 days after transplant. To investigate the functional significance of this observation, heart donors and donor bone marrow were irradiated before transplantation in CTLA4-Ig-treated recipients. A reduction in allograft survival was associated with irradiation of both the donor heart and the bone marrow. These results suggest that there may be a donor-derived radiosensitive element that enhances allograft survival in this model.Reverse transcriptase polymerase chain reaction analysis of allografts of tolerant and control animals at days 5, 8, and 12 after transplantation failed to demonstrate a dramatic difference in the expression of interleukin (IL)-2, IL-4, IL-10, and interferon-γ message. Cytotoxicity effector transcripts were largely intact in CTLA4-Ig + bone marrow-treated recipients as they showed no decrease in intragraft granzyme, perforin, Fas, or Fas ligand transcripts during the first 8 days after transplant. These results imply that complex mechanisms may be important for the induction and maintenance of transplantation tolerance in the CTLA4-Ig plus bone marrow murine cardiac allograft model.

ISSN:0041-1337    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

The effect of the type of venous drainage of the graft on its endocrine function was studied in two groups of pigs after segmental pancreas autotransplantation. Group 1 comprised 10 pigs with portal venous drainage (PVD) and group 2 comprised 10 pigs with systemic venous drainage (SVD). The graft consisted of body and tail of the pancreas. The pigs were totally pancreatectomized. The pancreatic duct was occluded by neoprene injected into the duct. One week before and 1 and 3 months after transplantation, intravenous glucose tolerance tests (IVGTT) and meal stimulation tests (MST) were performed. Plasma glucose (PG), insulin (INS), C-peptide, glucagon (GLU), and pancreatic polypeptide (PP) were measured during the tests. All pigs had normal fasting PG, 1 and 3 months after PanTx, although MST disclosed significantly higher PG (P<0.05) during the test after transplantation. In the PVD group, a decrease in INS level during both tests was recorded after PanTx (P<0.05), while in the SVD group a nonsignificant rise in INS level was recorded compared with before transplant. A significant difference (P<0.05) in INS levels were present both 1 and 3 mon. after PanTx between the two groups. Pigs with PVD showed a higher (P<0.05) C-peptide level than pigs with SVD during IVGTT. The initial significant rise in PP during MST and the initial fall in PP during IVGTT recorded in all pigs before transplantation were totally lost after transplantation in both groups. During the tests, PP remained steady and significantly lower than the pretransplantation levels in both groups. A significantly higher GLU level during both IVGTT and MST was observed in SVD compared with PVD 1 month after PanTx (P<0.05), being more pronounced during MST. This accentuated GLU concentration decreased by 3 months after transplantation, although it was still significantly greater than pretransplantation levels. We conclude that the unnatural mode of delivery of pancreas endocrine secretion to systemic rather than to portal circulation leads to derangements in pancreatic endocrine function in order to maintain glucose homeostasis. This may cause earlier exhaustion of islet cells. Segmental rather than whole organ and duct occlusion rather than exocrine drainage may further contribute to this, shortening the effective life of the graft.

ISSN:0041-1337    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

In an effort to increase the donor pool for lung transplantation (LTX), we have demonstrated the feasibility of LTX from circulation-arrested cadavers in a canine LTX model. We hypothesized that ventilation of the cadaver lung with alveolar gas (20% O2, 5% CO2, balance N2) (AG) would be superior to ventilation with 100% oxygen (O2) after circulatory arrest of the donor. Twelve mongrel dogs were intubated, heparinized and euthanized by pentothal injection and ventilated with AG (n=6) or O2(n=6). Four hours later, donor animals underwent sternotomy, and the lungs were flushed with cold modified Euro-Collins solution, harvested, and stored inflated in iced slush. Left lung allotransplantation was performed, and recipients were made dependent on the transplanted lung by occlusion of the contralateral bronchus and pulmonary artery. Recipient animals were ventilated with an FiO2of 0.4 and followed for 8 hr. Total ischemic time was 7.9 hr for both groups. Pulmonary edema developed in all recipients of AG lungs; one recipient survived the 8-hr observation period with poor oxygenation. In contrast, three of six recipients of O2-ventilated lungs survived for 8 hr with excellent gas exchange. Specimens of donor lungs before and after transplant were evaluated histologically utilizing trypan blue exclusion as an indicator of cell viability. At the time of organ retrieval 4 hr after death, 6% of cells were nonviable in the O2-ventilated cadaver lungs, compared with 11% in AG-ventilated cadaver lungs. Circulation-arrested cadaver lungs ventilated with 100% O2prior to organ retrieval have superior pulmonary function after transplant compared with lungs ventilated with AG. Ventilation of cadaver lungs with AG induces pulmonary injury in this model. Retrieval of donor lungs from circulation-arrested cadavers has potential for increasing the pulmonary donor pool.

ISSN:0041-1337    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Macromolecules are present in lung preservation solutions to limit liquid filtration out of the pulmonary circulation and minimize pulmonary edema. We tested the effectiveness of these molecules by measuring interstitial edema in rat lungs perfused with macromolecular solutions (University of Wisconsin [UW] solution and Euro-Collins solution supplemented with modified pentastarch [pentafraction, PEN]), or with solutions that lacked macromolecules (UW solution without PEN and Euro-Collins solution.) The lungs were inflated with air and perfused with one of the test solutions, then rapidly frozen and prepared for histological analysis. From tissue sections, we measured cross-sectional areas of pulmonary arteries and veins, and also measured cross-sectional areas of interstitial spaces surrounding arteries and veins. We then calculated the interstitium-to-vessel cross-sectional area ratio. In lungs perfused with macromolecular solutions these ratios were 0.09±0.15 and 0.53±0.56 (mean ± SD) for UW solution and Euro-Collins solution with PEN, respectively (P≤0.05). In lungs perfused with solutions that lacked macromolecules, area ratios were 0.48±0.88 and 1.95±1.82 for UW solution without PEN and Euro-Collins solution, respectively (P≤0.05). Solutions containing PEN caused less interstitial expansion than their counterparts that lacked it, but UW solution without PEN caused interstitial expansion equal to that of Euro-Collins solution with PEN. We conclude that macromolecules limit edema formation, but other constituents of UW solution limit edema formation also.

ISSN:0041-1337    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Prolonged cold ischemia time and the generation of free oxygen radicals during reperfusion are risk factors for allograft arteriosclerosis. Growth factors are the main pro-proliferative mediators of smooth muscle cells in classical and in allograft arteriosclerosis. Superoxide dismutase is an enzyme that catalyzes the dismutation of superoxide anions into hydrogen peroxide. This study was designed to investigate which smooth muscle cell growth factors contribute to the formation of arteriosclerosis in syngeneic vascular grafts with prolonged ischemia time, and whether perioperative intravenous administration of recombinant human superoxide dismutase (rh-SOD) prevents arteriosclerosis in these grafts. DA aortas were transplanted into DA recipients. One group of transplants was made with a short ex vivo ischemia time (15 min), while the other group of transplant grafts was stored for 24 hr in cold saline. In addition to morphometric quantitation of the histological alterations, RNA isolated from grafts with prolonged cold ischemia time was compared with that from grafts with short cold ischemia time in a semiquantitative polymerase chain reaction specific for various known smooth muscle cell growth factors. Syngeneic grafts with prolonged cold ischemia time showed severe intimal thickening and prominent medial necrosis, which were not seen in control groups. Approximately 3-fold levels of insulin-like growth factor-1 were found in ischemic syngeneic grafts compared with non-ischemic syngeneic grafts, whereas epidermal growth factor levels were slightly lower. No changes in other growth factor mRNAs were found. Perioperative treatment with rh-SOD did not have any significant effect on the extent of intimal thickening nor on the intensity of medial necrosis in grafts with prolonged ischemia time, and administration of rh-SOD did not change the expression level of insulin-like growth factor-1 in the grafts, either.

ISSN:0041-1337    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Limited recovery of contractile function and loss of coronary reactivity have been observed following prolonged hypothermic storage and transplantation of the heart. Since lipid peroxidation has a significant role in these deficits, we investigated the cardioprotective effects of a 21-aminosteroid. U74389G, 3 mg/kg i.v., was given daily for 2 consecutive days to donor Lewis rats before the hearts were harvested and to recipient Lewis rats for 3 consecutive days after heart transplantation. Donor hearts were preserved for 4 hr in cold saline (4°C) before transplantation. Left ventricular developed pressure (LVP), basal coronary perfusion, and coronary reactivity to endothelium-dependent dilation (bradykinin, 0.1 μM) or endothelium-independent dilation (sodium nitroprusside, 0.5 μM) were studied in isolated, buffer-perfused heart, using a modified Langendorff model. Cold preservation alone significantly reduced LVP and coronary perfusion. Coronary reactivity to bradykinin and sodium nitroprusside was also significantly impaired. In U74389G-treated donor hearts, 4 hr of cold ischemia did not alter contractile function, coronary perfusion or endothelial reactivity, although the response to sodium nitroprusside did not fully recover. In untreated recipients, in vivo reperfusion (transplantation) resulted in reduced LVP and perfusion deficits. Treating donors and recipients with U74389G improved left ventricular contractility and coronary perfusion, although endothelium-dependent and -independent coronary reactivity remained affected. These results indicate that the lazaroid U74389G exerts significant cardioprotection during both preservation and transplantation of the heart. Donor and recipient pretreatment is mandatory for maximal efficacy with U74389G.

ISSN:0041-1337    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Mycophenolate mofetil (MMF) is a powerful immunosuppressant that inhibits the proliferation of T and B lymphocytes by blocking the enzyme inosine monophosphate dehydrogenase. MMF has been shown to prevent acute graft rejection in animal experiments and may have an important role in clinical renal transplantation.We conducted a prospective, double-blind, multicenter trial to compare the efficacy and safety of MMF and azathioprine within a standard immunosuppressive regimen for patients receiving a first or second cadaveric renal graft. A total of 503 patients were randomized to groups receiving MMF 3 g (n=164), MMF 2 g (n=173), or azathioprine (AZA) 100-150 mg (n=166) daily. All were treated simultaneously with equivalent doses of cyclosporine and oral corticosteroids and followed for 12 months. The primary endpoint was treatment failure, defined as the occurrence of biopsyproven graft rejection, graft loss, patient death, or discontinuation of the study drug during the first 6 months after transplantation.Treatment failure occurred in 50.0% of patients in the AZA group by 6 months after transplantation, compared with 34.8% in the MMF 3 g group (P=0.0045) and 38.2% in the MMF 2 g group (P=0.0287). Biopsy-proven rejection occurred in 15.9% of patients in the MMF 3 g group and 19.7% in the MMF 2 g group, compared with 35.5% in the AZA group. Rejection of histologic severity grade II or more developed in 6.1%, 10.4%, and 19.9% of patients in the MMF 3 g, MMF 2 g, and AZA groups, respectively. Patients receiving MMF required less frequent and less intensive treatment for acute rejection: 24.4% of patients on MMF 3 g and 31.0% on MMF 2 g were treated for acute rejection, compared with 47.5% on AZA. Only 4.9% on MMF 3 g and 8.8% on MMF 2 g required antilymphocyte antibodies for treatment of severe or steroid-resistant rejection, compared with 15.4% of the patients on AZA. At 1 year afte transplantation, graft survival in the MMF groups was marginally superior to that in the AZA group, although this difference was not statistically significant. Gastrointestinal toxicity and tissue-invasive cytomegalovirus infection were more common in the MMF 3 g group. Noncutaneous malignancies occurred in six patients on MMF 3 g, three patients on MMF 2 g, and four patients on AZA. Lymphoproliferative disorders occurred in two patients per MMF group, compared with one patient receiving AZA.MMF appears to be an important advance in prophylaxis following renal transplantation. It is associated with a significantly lower rate of treatment failure compared with AZA during the first 6 months after renal transplantation and produces a clinically important reduction in the incidence, severity, and treatment of acute graft rejection. These differences persist throughout the first year of follow-up. Clinical benefit was greatest with a dose of MMF 3 g/day, but gastrointestinal effects, invasive cytomegalovirus infection, and malignancies were slightly more common at that dose. The appropriate dose may lie between 2 g and 3 g per day and may require individualization depending on clinical course or other factors.

ISSN:0041-1337    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

Cyclosporine (CsA) and prednisone (Pred) are the most widely used drugs for immunosuppression after renal transplantation, but both drugs have marked side effects. Either replacement of CsA by azathioprine (Aza) or withdrawal of prednisone (Pred) resulting in CsA monotherapy can be employed to circumvent the adverse effects in the long run. Both treatment regimens were compared in this prospective randomized trial in patients who were treated with CsA and Pred during the first 3 months after renal transplantation (CsA: n=64, Aza-Pred: n=63, median duration of follow-up: 3.9 years). Estimated graft survival rates at 5 years after transplantation (in patients with a functioning graft at 3 months) were 78% in the CsA group and 87% in the Aza-Pred group. The incidence of a rejection within 3 months after start of steroid withdrawal or conversion from CsA to Aza was 30% and 25%, respectively (NS). At 2 years after transplantation, serum creatinine levels were lower in the Aza-Pred group (126±35 μmol/L) than in the CsA group (180±78 μmol/L;P<0.001). There were no differences in blood pressure or incidence of infections between the treatment groups. Treatment-related costs were measured during the first year after transplantation and were lower in the Aza-Pred group (DFL 40,882±18,895 vs. DFL 53,484±44,828; 1 DFL [Dutch guilder] is about US $0.60;P<0.05). In conclusion, CsA monotherapy and Aza-Pred treatment from 3 months after renal transplantation are comparably effective immunosuppressive treatment regimens, although Aza-Pred therapy results in better graft function. Withdrawal of steroids and replacement of CsA by Aza both carry a substantial risk of rejection. The previously demonstrated cost effectiveness of CsA-containing therapies seems to be limited to the first phase after transplantation. Conversion to Aza-Pred at 3 months after transplantation reduces costs.

ISSN:0041-1337    

出版商:OVID    

年代:1996

数据来源: OVID

摘要:

In an attempt to reduce the variability in the yields of human islet isolations and to identify donor factors that were potentially deleterious, we retrospectively reviewed 153 human islet isolations in our center over a 3-year period. Isolations were performed using controlled collagenase perfusion via the duct, automated dissociation, and Ficoll purification. Factors leading to successful isolations (recovery of >100,000 islet equivalents at a purity >50%) were analyzed retrospectively using univariate and multivariate analysis. Critical factors in the multiorgan cadaveric donors that were identified using univariate analysis included donor age (P<0.01), body mass index (BMI) (P<0.01), cause of death (P<0.01), and prolonged hypotensive episodes (systolic blood pressure <90 mmHg or mean arterial pressure <60 mmHg for >15 min) requiring high vasopressors (>15 μg/kg/min dopamine or >5 μg/kg/min Levophed) (P<0.01). Independent analysis of 19 donor variables using multivariate logistic stepwise regression showed that six factors were statistically significant. Odds ratio (OR) showed that donor age (OR 1.1,P<0.01), local procurement team (OR 10.9,P<0.01), and high BMI (OR 1.4,P<0.01) had a positive correlation with islet recovery. In contrast, hyperglycemia (all blood glucose >10 mmol/L) (OR 0.63,P<0.01), frequency and duration of cardiac arrest (OR 0.7,P<0.01), and increased duration of cold storage before islet isolation (OR 0.83,P<0.01) had negative correlations. Using these combinations of factors, the prediction of success was 85% accurate.By donor age, success was 13% for 2.5- to 18-year-old donors (n=23), 37% for 19- to 28-year-old donors (n=30), 65% for 29- to 50-year-old donors (n=70), and 83% for 51- to 65-year-old (n=29) donors. However, when in vitro function was assessed by perifusion, the insulin secretory capabilities of islets isolated from the >50-year-old donor group was significantly reduced as compared with the 2.5- to 18-year-old group (P<0.02).Multiple regression analysis using postdigestion and postpurification islet recovery as outcome variables identified BMI, procurement team, pancreas weight, and collagenase digestion time as factors that can affect the recovery of human islets. Locally procured pancreases and donors with elevated minimum blood glucose levels were identified as factors that affect the insulin secretory capabilities of the isolated islets. This review of parameters suggests an improved approach to the prediction of successful islet isolation from human pancreas. Selection of suitable pancreases for processing may improve consistency in human islet isolation and thereby decrease costs.

ISSN:0041-1337    

出版商:OVID    

年代:1996

数据来源: OVID