ISSN:0041-1337    

出版商:OVID    

年代:1999

数据来源: OVID

ISSN:0041-1337    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Background.There are limited experimental data on the nature of the humoral response elicited in humans against pig antigens. In this study, we have examined the xenoantibody (XAb) response in eight patients with acute liver failure exposed to pig hepatocytes after treatment with the bioartificial liver (BAL).Methods.Patient's plasma samples obtained before and after BAL treatment were tested for IgM and IgG XAbs, IgG subclasses, and XAb cytotoxicity, using enzyme-linked immunosorbent assay and flow-cytometric assays. The characterization of pig aortic endothelial cell (PAEC) surface xenoantigens was analyzed by immunoprecipitation.Results.We observed by day 10, a strong anti-pig IgG and IgM XAb response in patients undergoing two or more BAL treatments, with a significant increase in all the IgG subclasses; in contrast, XAb titers did not change if the patients received only one BAL treatment. The majority of the XAbs produced to porcine antigens were primarily specific for the αGal epitope. Both IgG and IgM XAbs were cytotoxic to PAECs, and the cytotoxic activity of IgG was associated with high levels of IgG1 and IgG3 subclasses, known to be efficient on complement activation. The characterization of porcine surface antigens demonstrated that IgM human XAbs, before and after BAL exposure, recognized xenoantigens on PAECs with similar molecular weights, suggesting that the same population of XAbs were present in the patients before and after exposure to pig antigens.Conclusions.Repetitive exposure of humans to porcine antigens after BAL treatment, results in a strong IgG and IgM XAb responses that are primarily directed against the αGal epitope. These XAbs are cytotoxic to PAECs and the IgG toxicity correlates with high IgG1 and IgG3 levels. Our data also suggest that no new XAb specificity emerges after porcine exposure.

ISSN:0041-1337    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Background.Xenotransplantation would provide a solution to the current shortage of organs for transplantation. Our group has been successful in inducing tolerance in mice and monkey models of allogeneic transplantation. The present study attempts to extend the same tolerance-inducing regimen to a pig-to-baboon organ transplantation model.Methods.Nine baboons underwent a conditioning regimen (consisting of nonmyeloablative or myeloablative whole body and thymic irradiation, splenectomy, anti-thymocyte globulin, pharmacologic immunosuppression and porcine bone marrow transplantation [BMTx]), which has previously been demonstrated to induce donor-specific allograft tolerance in monkeys. In addition, immunoadsorption of anti-αGal antibody (Ab) was performed. Four of the nine baboons received pig kidney transplants (KTx), and one also underwent repeat transplantation with an SLA-matched kidney. Two received heterotopic pig heart transplants (HTx). Three baboons underwent conditioning without organ transplantation for long-term studies of natural Ab kinetics.Results.In the three baboons that received the conditioning regimen without an organ transplant, immunoadsorption reduced Ab by approximately 90%, but recovery of Ab to pretreatment level or higher occurred within 7 days. In contrast, the level of Ab remained low after organ transplant. No Ab to pig antigens other than αGal was detected in any baboon before or after BMTx, KTx, or HTx. No graft succumbed to hyperacute rejection. KTx function began to deteriorate within 3-6 days, with oliguria and hematuria progressing to anuria, and the kidneys were excised after 3, 6, 9, 11, and 14 days, respectively. One HTx ceased functioning at 8 days; the second baboon died with a contracting HTx at 15 days. Features of coagulopathy and thrombocytopenia developed in all six transplanted baboons (high D-dimer, prolonged prothrombin time and partial thromboplastin time, and falling fibrinogen) resulting in serious bleeding complications in two baboons, one of which died on day 9. Donor organs showed progressive acute humoral rejection with deposits of IgM, IgG, and complement; a focal mononuclear cellular infiltrate was also observed. The ureter was the earliest structure of the KTx affected by rejection, with progression to necrosis.Conclusions.This conditioning regimen prevented hyperacute rejection but was ineffective in preventing the return of Ab, which was associated with the development of acute humoral rejection with features of coagulopathy. No baboon developed anti-pig Ab other than αGal Ab. Further modifications of the protocol directed toward suppression of production of Ab are required to successfully induce tolerance to pig organs in baboons.

ISSN:0041-1337    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Background.Natural killer (NK) cells are major component of the cellular response in xenotransplantation. NK cell activation and NK cell-mediated cytotoxicity can be a direct barrier to the potential use of xenogeneic organs in human transplantation.Methods.To determine if HLA-G would protect porcine xenogeneic cells from human NK cell lysis, human full-length HLA-G genomic DNA was transfected into porcine aortic endothelial cell (PAECs) by the lipofection method. Surface expression of HLA-G in transfected PAECs was confirmed by immunofluorescence staining with anti-HLA class I framework antibody, PA2.6. Fresh human peripheral blood lymphocytes were used as NK effector cells with HLA-G-transfected PAECs as targets in a51Cr release assay. The inhibition of human polyclonal NK cells by HLA-G expression on PAECs was confirmed by antibody blocking using purified F(ab′)2 portion of anti-human HLA class I antibody PA2.6.Results.Expression of HLA-G on PAECs conferred a significant protection against NK-mediated lysis (range: 52-100% inhibition) when peripheral blood lymphocytes from seven healthy donors, bearing either homozygous HLA-Cw3 or -Cw4 used as NK effector cells. Such protection was inhibited by purified F(ab′)2 portion of anti-HLA class I antibody, indicating that the protection of PAECs was directly mediated by HLA-G expression.Conclusions.Expression of HLA-G on PAECs protected xenogeneic PAECs against human polyclonal NK cell-mediated lysis. These results indicate that the expression of HLA-G alone in the absence of other nonclassical HLA class I molecules is sufficient to inhibit human NK cell lysis. These findings suggest methods utilizing HLA-G to overcome NK cell-mediated cytotoxicity against porcine endothelial cells, considered the first cell type effected during xenograft cellular rejection.

ISSN:0041-1337    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Background.The coagulation process in hyperacute and delayed xenograft rejection is essential and depends upon platelet adhesion and aggregation. The initial binding of platelets to the damaged endothelium is due to the interaction of the platelet receptor glycoprotein Ib with von Willebrand factor (vWF), which is present on activated endothelial cells and bound to the subendothelial matrix. We hypothesized that the use of organs from animals with homozygous von Willebrand disease (vWD), severely deficient in vWF, might prevent the thrombosis encountered in delayed xenograft rejection.Methods.Ten baboons were treated by extracorporeal immunoadsorption of xenoreactive natural antibodies (XNA) through the donor pig liver to inhibit hyperacute rejection and received heterotopic vWD or control pig kidney xenografts. XNA levels, coagulation, and platelet activation markers were studied, and specimens of rejected kidneys were analyzed histologically.Results.Although XNA depletion was comparable in both groups, neither kidney function nor survival times of control (n=5) or vWD (n=5) porcine kidneys showed any difference. Platelet and coagulation activation was evidenced in both groups after surgery and at rejection time. Immunohistochemical analysis revealed a weak endothelial vWF immunostaining in the rejected vWD kidneys, whereas it was undetectable in the nongrafted vWD kidneys, suggesting the deposition of baboon plasma vWF on the porcine vessels.Conclusions.The use of vWD organs did not improve the survival time of grafted kidneys in this xenotransplantation model. Further studies on the use of vWD organs, in association with other therapeutic approaches, such as complement inhibition, are nevertheless necessary to evaluate the usefulness of vWF deficiency as an adjunctive therapy to decrease the coagulation process during xenograft rejection.

ISSN:0041-1337    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Background.Tissue factor (TF) is an initiation factor for blood coagulation, and its expression is induced on macrophages and endothelial cells during the inflammatory or immune responses. In a previous study, we reported the significance of TF expression in hepatic ischemic reperfusion injury using a rat model. Recently, tissue factor pathway inhibitor (TFPI) has been discovered, and the effect of TFPI has been assessed in vivo. In this study, therefore, we studied the effect of TFPI on hepatic ischemic reperfusion injury of the rat.Methods.After laparotomy of Lewis rats, the branches of the hepatic artery and portal vein leading to the median, left, and caudate lobes of the liver were clamped. The liver was reperfused after 120 or 180 min of ischemia. Simultaneously, recombinant human TFPI (4 mg/kg) was injected via a superiomesenteric vein. Rats were sacrificed at 5, 12, and 24 hr after reperfusion, and liver tissues were harvested. TF expression was studied by immunohistochemical staining with the monoclonal antibody (HTF-K108).Results.Survival rates over a 5-day period were examined after the ischemic time of 120 and 180 min. Seven of 10 rats in the 120-min ischemia group (n=10), and only 1 (10%) rat of 10 in the 180-min ischemia group (n=10) survived. However, by the treatment with TFPI, all of the rats in the 120-min ischemia group (n=10), and six rats in the 180-min ischemia group (n=10) survived (P<0.05). The serum concentrations of alanine aminotransferase (ALT) and thrombin-altithrombin complex (TAT) before ischemia were 30.0±2.3 IU/L and 4.7±1.4 ng/ml, respectively (n=5). These levels showed a peak at 3-5 hr after reperfusion (ALT: 13909±1900 IU/L, TAT: 30.4±7.0 ng/ml) (P<0.01). However, both peak levels were decreased by the treatment with TFPI (ALT: 6017±1290 IU/L, TAT: 5.4±2.1 ng/ml) (P<0.01). Although TF was strongly stained on endothelial cells and Kupffer cells accumulating to the site of the necrosis in the control group, the area of the necrosis and the grade of TF staining were significantly reduced in the TFPI-treated group.Conclusions.These results indicated that TFPI strongly inhibited the injury of the ischemic reperfusion, and confirmed that TF played a pivotal role in the development of ischemic reperfusion injury.

ISSN:0041-1337    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Background.To determine the impact of cyclosporine plasma protein binding on organ rejection after cardiac transplantation, the incidence of cardiac rejection episodes was compared among patients who had differing levels of cyclosporine plasma fraction unbound (fU).Methods.Forty-six consecutive cardiac transplant recipients were sampled at 1, 3, 6, and 12 months after transplantation, and cyclosporine plasma fUwas determined, using a specially developed equilibrium dialysis method. At the completion of the study, incidences of cardiac rejection episodes were compared among patients having mean cyclosporine fU(Csfu) that were low (ICsfu; mean ± SD, 1.33±0.10%, n=15), intermediate (ICsfu; 1.60±0.07%, n=16), and high (Csfu; 1.99±0.30%, n=15).Results.Percentage of endomyocardial biopsies (grade 3a, 3b, and 4) with respect to the total number of biopsies performed in the first 3 months after transplant was significantly higher in the LCsfugroup than the other groups (40.9% in LCsfuvs. 28.5 for ICsfuand 32.1% for HCsfugroups,P=0.02). The linearized rate of rejection (episodes of rejection/100 patient-days) in the first month after transplant was 6.5±1.7 for LCsfu, 3.5±0.8 for ICsfuand 4.3±0.9 for the HCsfugroup (P<0.05, low vs. intermediate-high). The mean (95% confidence interval) of time interval between the first and second episodes of rejections was 10.7 (5.6-16.0) days for LCsfu, 18.0 (8.6-29.0) days for the ICsfu, and 26.0 (15.1-36.9) days for the HCsfugroup (P<0.01). The total number of rejections requiring treatment per patient in the first 3 months after transplant was higher in the LCsfugroup compared with the others (4.0±1.7 episodes for LCsfuvs. 2.9±1.1 for ICsfuand 3.2±1.2 episodes for HCsfu;P<0.05). Four patients in the low group, one patient in the intermediate group, and no patients in the high group required treatment with total lymphoid irradiation (P<0.02).Conclusions.This finding suggests that patients with lower levels of cyclosporine fUare more prone to cardiac rejection and that the level of cyclosporine fraction unbound may be clinically important for determination of response to cyclosporine therapy.

ISSN:0041-1337    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Objective.Profound immunosuppression and extensive fibrotic changes in the skin are characteristic for graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation (BMT). Transforming growth factor (TGF)-β is a potent immunosuppressive cytokine that plays an important regulatory role in the immune response. In addition, TGF-β promotes wound repair but has also been implicated in tissue fibrosis. These characteristics prompted us to question whether serum TGF-β levels would be associated with GVHD after BMT.Methods.In this study, total TGF-β1levels in serum from HLA-identical BMT recipients before and at several time intervals after transplantation were quantified and correlated with platelet and white blood cell (WBC) counts and with the presence of acute and chronic GVHD in a multivariate analysis.Results.TGF-β1levels were readily detectable in healthy controls and in BMT recipients before BMT. In all patients, a rapid drop in TGF-β1levels was seen during the BMT conditioning regimen. After 20-50 days postBMT, TGF-β1levels started to increase to normal levels. Platelet and WBC counts were strongly correlated with TGF-β1levels (r=0.810,P<0.001, andr=0.733,P<0.001, respectively). Multivariate analysis also revealed that TGF-β1levels were significantly increased during chronic GVHD and that the increase during acute GVHD reached levels of significance (P=0.009 andP=0.053, respectively).Conclusions.These results show that total TGF-β1levels correlate significantly with platelet and WBC counts and that chronic GVHD is associated with an increase in serum TGF-β1, independent of platelet or WBC counts.

ISSN:0041-1337    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

Orthotopic liver transplantation can be performed successfully in thalassemia. In this article, we describe a case of liver transplantation in a patient with sickle cell/β-thalassemia complicated by liver sickling. Intrahepatic sickling must be considered in case of allograft dysfunction. This condition can easily be diagnosed by biochemical investigation and liver ultrasonography.

ISSN:0041-1337    

出版商:OVID    

年代:1999

数据来源: OVID