摘要:

Introduction.In 1997, Ross et al. proposed to increase the supply of living kidney donations by using kidneys from living ABO-incompatible donors through an exchange arrangement between two living kidney donor-recipient pairs. Although many transplant centers are exploring this option, only a small fraction of potential donor-recipient pairs are eligible for an exchange on the basis of ABO incompatibility. In this article, we explore three variations that have potentially great clinical relevance.Methods.The three potential variations discussed are: (1) altruistically unbalanced living donor-recipient exchanges; (2) an indirect exchange (an exchange between a living donor-recipient pair with a cadaveric donor-recipient pair) on the basis of a positive crossmatch; and (3) an indirect exchange on the basis of ABO incompatibility.Discussion.The goal of kidney paired exchange programs is to increase the supply of kidneys available for transplantation ethically. We acknowledge that all exchanges increase the potential for coercion, and we currently reject the proposal of altruistically unbalanced exchanges because of the potential for coercion. However, we believe that voluntary consent can be achieved for indirect exchanges. The indirect ABO-compatible exchange creates no new ethical concerns to our original living paired exchange program and we support its implementation. The indirect ABO-incompatible exchange does create a new ethical concern because it may increase the vulnerability of O blood group recipients. If mechanisms can be developed to avoid increasing the waiting time for blood group O recipients, we would support the implementation of the indirect ABO-incompatible exchange.

ISSN:0041-1337    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0041-1337    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0041-1337    

出版商:OVID    

年代:2000

数据来源: OVID

ISSN:0041-1337    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background.Previous studies showed the feasibility of inducing transplantation tolerance to cadaveric renal allografts in patients given pretransplant total lymphoid irradiation (TLI).Microchimerism has been theorized to be an important or necessary factor in long-term graft acceptance and tolerance in humans.Methods.A cadaveric renal transplant recipient given pretransplant total lymphoid irradiation and withdrawn from immunosuppressive drugs more than 12 years ago was tested for microchimerism using a sensitive nested polymerase chain reaction technique, and for anti-donor reactivity using the mixed leukocyte reaction and an ELISA screen for anti-HLA antibodies. Donor and recipient were mismatched for all HLA-A, B, and DR antigens.Results.The “tolerant” recipient had good graft function, no detectable donor-type cells in the blood by polymerase chain reaction analysis, vigorous reactivity to donor stimulator cells in the mixed leukocyte reaction, and no detectable serum anti-HLA antibodies.Conclusions.Operational tolerance to HLA-A, B, and DR mismatched organ allografts can be induced prospectively in humans for at least 12 years after withdrawal of immunosuppressive drugs. The allograft can be maintained in the absence of detectable donor microchimerism and in the presence of anti-donor reactivity in the mixed leukocyte reaction, suggesting that neither chimerism nor clonal deletion or anergy of recipient T cells to alloantigens presented by donor Class II HLA molecules is required for persistence of the tolerant state using this total lymphoid irradiation protocol.

ISSN:0041-1337    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background.In nonprimates, organ allografts are often not rejected after withdrawal of immunosuppression.In this study, we examined whether such a phenomenon also occurs in primates.Methods.Vervet monkeys were transplanted with renal allografts and treated for 60 days with tacrolimus, or tacrolimus plus sirolimus. The drugs were totally withdrawn on day 61. The survival of the monkeys was monitored, and their response to donor- or third party-derived alloantigens was examined in vivo and in vitro.Results.The majority (80–100%) of the grafts survived for at least additional 30 days with no signs of acute rejection. The compromised rejection is donor-specific, because recipient monkeys failed to reject a donor-derived skin graft, but a third-party skin graft was rejected. In vitro mixed lymphocyte reaction and interleukin-2 production in the mixed lymphocyte reaction between the recipients and their donors or between the recipients and a third party had no discernable patterns, and thus did not reflect the in vivo status of the immune system. Although the recipients could not reject the graft acutely after drug withdrawal, the kidney grafts and the donor-derived skin grafts had pathological findings of chronic rejection.Conclusions.The rejection response of the monkeys to an established graft after withdrawal of immunosuppression is compromised. The compromised rejection is specific and is not due to a permanent alteration of the immune system by the initial drug treatment. The allografts are not inert but have low levels of interaction with the recipient immune system.

ISSN:0041-1337    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background.A new model of cellular adrenocortical transplantation after bilateral adrenalectomy in the mouse was established. This model was used to study the effects of the expression of the transgenic MHC class I molecule H-2Kb(Kb) on graft survival and morphologic features, corticosterone secretion, and the possibility of tolerance induction in the recipient.Method.A single cell suspension of purified adrenocortical cells was grafted under the kidney capsule of B10.Br (H-2k) mice having adrenalectomies. Syngeneic, fully MHC-mismatched, and MHC class I-incompatible Kb-transgenic mice served as donor strains. To analyze graft function, urinary excretion and serum levels of corticosterone were monitored over 100 days. Tolerance induction in the graft recipients of Kb-transgenic and third party skin grafts was tested on day 50 after adrenocortical transplantation. Histological sections of the adrenocortical grafts were obtained on day 100.Results.Recipients of syngeneic and Kb-transgenic grafts displayed pretransplant corticosterone levels on days 20, 50, and 100 and ACTH-stimulated serum corticosterone levels similar to those of controls on day 100 after adrenocortical transplantation. In contrast, in recipients of fully MHC-mismatched grafts, corticosterone excretion was significantly reduced. In this group, 4 of 7 mice did not survive. Syngeneic skin grafts survived indefinitely in recipients of syngeneic and Kb-transgenic adrenocortical grafts, whereas Kb-transgenic and fully MHC-mismatched skin grafts were acutely rejected. Tissue sections of the adrenocortical grafts revealed vascularized cell conglomerates in syngeneic and Kb-transgenic grafts without infiltrations of mononuclear cells. Furthermore, a differentiation similar to adrenocortical organization was partly found.Conclusion.In conclusion, a model of cellular adrenocortical transplantation was established. The results show that syngeneic transplantation resulted in physiological corticosterone levels early after transplantation, whereas fully MHC-incompatible grafts were rejected. Recipients of Kb-transgenic grafts showed unimpaired adrenocortical function, but did not tolerize toward Kb-transgenic skin grafts. Possible mechanisms include a local immunomodulatory effect of glucocorticoids secreted by the graft and a low immunogenicity of the relatively small numbers of transplanted cells.

ISSN:0041-1337    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background.Induction of unresponsiveness to graft is one of major interest in xenotransplantation. Two different modalities [direct graft treatment by mitomycin C (MMC) and blockage of the lymphocyte function-associated antigen-1/intracellular adhesion molecule-1 (LFA-1/ICAM-1) pathway in recipients by species-specific mAbs] were tested for their ability to produce unresponsiveness to secondary islet xenografts.Methods.Collagenase-digested WS (RT1k) rat islets, purified by Ficoll density gradient, were incubated for 30 min with MMC 10 &mgr;g/ml, cultured for 20 hr, and transplanted into the renal subcapsular space of streptozotocin-induced diabetic C57BL/6 (H-2b) mice. Recipient mice were divided into experimental groups according to anti-rat ICAM-1 and/or anti-mouse LFA-1 mAb treatment and transplantation of MMC-treated or nontreated islets.Results.MMC pretreatment alone prolonged graft survival, with a mean survival time (MST) of 23.0±7.4 days, compared with that of cultured islets (12.4±2.7 days;P<0.01). MMC treatment of islets significantly augmented graft survival, compared with that of crude islet grafts under treatment with anti-donor ICAM-1 mAb (MST: >41.3±30 vs. 16.6±5.4 days,P<0.01), anti-recipient LFA-mAb (MST: >70.3±28.9 vs. 30.4±10.4 days,P<0.001), or both mAbs (MST: >88.1±24.1 vs. 23±7.4 days,P<0.0001). One of six, four of nine, and six of eight animals accepted MMC-treated islet xenografts over 100 days after treatment with anti-rat ICAM-1, anti-mouse LFA-1, or both mAbs treatments, respectively, whereas none of the animals accepted nontreated islets under the same treatment. When the mice bearing long-term functioning xenografts were challenged with the secondary graft from the original donor strain, the animals previously treated with anti-recipient LFA-1 and anti-donor ICAM-1 mAbs were more prone to accept it than animals given anti-recipient LFA-1 mAb alone (MST: 55.8±25.7 vs. 15±2.4 respectively;P<0.001), although they rejected the third-party xenograft and allograft acutely.Conclusions.In the xenogeneic islet transplantation model, MMC graft pretreatment and blockage of the ICAM-1/LFA-1 pathway constitute a potent protocol for inducing unresponsiveness to islet xenografts.

ISSN:0041-1337    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background.A better understanding of altered expression of myocardial &bgr;-adrenoceptors can facilitate the diagnosis of early and late acute rejection of heart transplants.Methods.We submitted rats to heterotopic heart transplantation (iso- and allografts) of which one of each were treated with or without cyclosporin A for 4, 7, and 14 days (n=5, respectively). The cardiac sections were incubated in vitro with [3H]CGP 12177, or the hearts were labeled in vivo by intravenous injection of [3H]CGP 12177. Autoradiographic images of both were analyzed digitally and compared with histologic findings.Results.&bgr;-Adrenoceptor distribution in native hearts and isografts was homogeneous, but highly differential distribution and density in allografts were observed in the left and right ventricular walls and in the interventricular septum despite treatment with cyclosporin A. High-density areas in the progressive course of acute rejection are commonly associated with up-regulation of &bgr;-adrenoceptors in apparently viable myocytes, although histologic findings confirmed many infiltrating mononuclear cells. Low-density areas, which were identified in the right and left ventricular walls as early as 4 days after transplantation, correlated with derangement of myocytes, which was suggestive of early acute rejection. The images obtained by in vivo technique were comparable to in vitro images.Conclusions.The alteration of &bgr;-adrenoceptor expression in allografts showed a close relationship with the severity of acute rejection, and the techniques employed in this model were useful in our study of the rejection process and in detecting early and late acute rejection in the rat.

ISSN:0041-1337    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Background.The factor V R506Q mutation (FV R506Q, FV:Q506, or FV Leiden) resulting in activated protein C (APC) resistance is the most common inherited risk factor for venous thrombosis, including in renal transplant recipients. We investigated a possible association between the FV mutation and early renal graft loss, and the prevalence of macro- and microvascular thrombosis, endothelialitis, and fibrinoid vascular necrosis by FV genotype.Method.One hundred and nine renal allograft recipients were genotyped for FV mutation. A vascular rejection subgroup of patients (n=29) had experienced at least one episode of vascular rejection, or graft thrombosis. A second group of patients (n=80) had experienced no acute rejection and retained a well-functioning graft.Results.The prevalence of APC resistance was numerically but not statistically significantly higher in the vascular rejection group (17.2%) compared with the group without rejection episodes (7.5%) (P=0.16). There was a significant association between the presence or absence of FV mutation and graft survival, with a 55.6% 1-year graft survival rate versus a 76.4% rate, respectively (P=0.02). The prevalence of vascular rejection, as evidenced by endothelialitis or fibrinoid vascular necrosis, was significantly associated with APC resistance but macro- or microvascular thrombosis were not.Conclusion.Renal transplant recipients who are carriers of the FV:Q506allele have an increased risk of early graft loss. Vascular rejection changes including endothelialitis and fibrinoid vascular necrosis were more common in this group, and therefore an association between the hypercoagulable state, which entails an up-regulation of the mitogenic and proinflammatory enzyme thrombin, and the immunological challenge to the endothelium may be the cause of inferior prognosis in these patients.

ISSN:0041-1337    

出版商:OVID    

年代:2000

数据来源: OVID