Biomedical subjects

David H Sachs

Publications and source records attributed to David H Sachs.

At least 19 recordsLinked to original sources

PubMed2007

Gene expression of porcine lymphotrophic herpesvirus-1 in miniature Swine with posttransplant lymphoproliferative disorder.

Porcine lymphotropic herpesvirus-1 (PLHV-1) is a gamma-herpesvirus related to Epstein-Barr virus (EBV) and associated with development of posttransplant lymphoproliferative disorder (PTLD) following allogeneic stem cell or spleen transplantation in miniature swine. Oligonucleotide microarrays were designed based on known open reading frames (ORFs) of PLHV-1. Expression was compared by cohybridization of cDNA from lymph nodes of PLHV-1+ swine after allogeneic spleen transplantation between either: 1) PTLD-affected and PTLD-unaffected swine; or 2) PTLD-affected swine vs. samples from the same animal prior to diagnosis. In PTLD-affected animals, consistent upregulation (nine ORFs) and downregulation (four ORFs) of PLHV-1 mRNA was observed in comparison to those without PTLD. No differences in gene expression were discovered at the time of clinical PTLD diagnosis compared to six to nine days prior to diagnosis in the same animals. This model provides insights into the pathogenesis of PTLD and, by extension, potential diagnostic and therapeutic tools for human EBV-associated PTLD.

Animals↗

PubMed2006

Thymic rejuvenation and the induction of tolerance by adult thymic grafts.

The thymus, the site of origin of T cell immunity, shapes the repertoire of T cell reactivity through positive selection of developing T cells and prevents autoimmunity through negative selection of autoreactive T cells. Previous studies have demonstrated an important role for the thymus not only in central deletional tolerance, but also in the induction of peripheral tolerance by vascularized renal allografts in juvenile miniature swine recipients. The same protocol did not induce tolerance in thymectomized recipients nor in recipients beyond the age of thymic involution. We subsequently reported that vascularized thymic lobe grafts from juvenile donors were capable of inducing tolerance in thymectomized juvenile hosts. However, the important question remained whether aged, involuted thymus could also induce tolerance if transplanted into thymectomized hosts, which, if true, would imply that thymic involution is not an intrinsic property of thymic tissue but is rather determined by host factors extrinsic to the thymus. We report here that aged, involuted thymus transplanted as a vascularized graft into juvenile recipients leads to rejuvenation of both thymic structure and function, suggesting that factors extrinsic to the thymus are capable of restoring juvenile thymic function to aged recipients. We show furthermore that rejuvenated aged thymus has the ability to induce transplant tolerance across class I MHC barriers. These findings indicate that it may be possible to manipulate thymic function in adults to induce transplantation tolerance after the age of thymic involution.

Aging↗

PubMed2006

Monitoring antidonor alloantibodies as a predictive assay for renal allograft tolerance/long-term observations in nonhuman primates.

BACKGROUND: In an effort to define reliable assays that might predict postimmunosuppressant-withdrawal development of chronic rejection (CR), despite conditioning for tolerance induction, we evaluated various immunological responses in nonhuman primate renal allograft recipients. METHODS: Fourteen Cynomolgus monkeys received low dose total body irradiation, thymic irradiation, antithymocyte globulin, and peritransplant CD154 blockade, followed by a one-month course of cyclosporine. Recipients underwent major histocompatibility complex mismatched kidney transplantation with donor bone marrow infusion (Group A, n=8), without donor cell infusion (Group B, n=2), or with donor splenocyte infusion (Group C, n=4). RESULTS: All Group A recipients developed mixed chimerism and four of them survived long-term without rejection. The remaining four rejected their kidney allografts either chronically or acutely. All recipients in Groups B and C failed to develop chimerism and rejected their allografts. Among various in vitro assays, detection of anti-donor alloantibody (ADA) by flow cytometry (FCM) was the most relevant to long-term outcome. All five recipients that developed both anti-T cell and B cell IgG ADA in Groups A, B and C, developed histological evidence of CR within 200 days of the appearance of ADA. One of two recipients that developed only anti-B cell IgG ADA eventually developed CR over two years following discontinuation of immunosuppression and 1.5 years after ADA development. Another recipient with very low anti-B cell ADA has never developed CR. CONCLUSION: ADA monitoring with FCM assay appears to be useful in predicting the failure of tolerance prior to the development of functional or histologic abnormalities of the renal allograft.

Animals↗

PubMed2006

Allosensitization does not increase the risk of xenoreactivity to alpha1,3-galactosyltransferase gene-knockout miniature swine in patients on transplantation waiting lists.

BACKGROUND: The recent availability of alpha1,3-galactosyltransferase knockout (GalT-KO) miniature swine has eliminated anti-Gal antibodies as the major barrier to xenotransplantation, potentially bringing this modality closer to clinical application. Highly-allosensitized patients, who have poor prospects of receiving a suitable cross-match negative human organ, might be the first patients to benefit from xenotransplantation of porcine organs. However, concerns exist regarding cross-reactivity of alloreactive anti-human leukocyte antigen (HLA) antibodies against xenogeneic swine leukocyte antigen (SLA) antigens. We have investigated this question using sera from such patients on GalT-KO target cells. METHODS: Using flow cytometry and complement-dependent cytotoxicity (CDC) assays, we have tested a panel of 88 human serum samples from patients awaiting cadaveric renal allotransplantation for reactivity against: 1) human; 2) standard miniature swine; and 3) GalT-KO peripheral blood lymphocytes (PBL) and cultured endothelial cells. RESULTS: Anti-swine IgM and IgG antibody binding, as well as CDC, were significantly attenuated on GalT-KO versus standard swine. No correlation was found between the degree of anti-human panel reactive antibodies (PRA) and xenoreactivity against either standard or GalT-KO miniature swine. Treatment of sera with dithiothreitol (DTT) showed that the majority of remaining lymphocytotoxicity against GalT-KO swine was mediated by preformed IgM antibodies. Patients with high alloreactivity but low anti-GalT-KO xenoreactivity were readily identified. CONCLUSIONS: Highly allosensitized patients awaiting renal transplants appear to be at no increased risk of xenosensitization over their non-sensitized cohorts, and could therefore be candidates for xenotransplantation using GalT-KO swine donors.

Animals↗

PubMed2006

Elicited antibodies in baboons exposed to tissues from alpha1,3-galactosyltransferase gene-knockout pigs.

BACKGROUND: This study investigates anti-nonGal antibodies (Abs) in baboons after alpha1,3-galactosyltransferase gene-knockout (GalT-KO) pig heart transplantation (Tx). METHODS: Four baboons underwent pig heart Tx under chronic immunosuppression, which was discontinued after graftectomy. During follow-up, one baboon also received a pig splenocyte infusion. Hearts and splenocytes were from GalT-KO pigs (n = 3) or pigs with low Gal expression (Gal-low, n = 2), all of swine leukocyte antigen (SLA) dd haplotype. Several weeks after graftectomy, sera were tested by flow cytometry and cytotoxicity assay on porcine peripheral blood mononuclear cells (PBMC) for elicited anti-nonGal Abs. Sera were adsorbed on a Gal immunoaffinity matrix, and tested for SLA haplotype specificity using PBMC from SLA aa, cc, and dd haplotypes. RESULTS: Before heart Tx, no baboon had anti-nonGal Abs demonstrable by binding or cytotoxicity to GalT-KO PBMC. All four baboons developed anti-nonGal Abs after Tx, demonstrable by flow cytometry, and three sera from baboons showed cytotoxicity to GalT-KO PBMC of SLA(dd) haplotype. After adsorption of anti-Gal Abs, the elicited anti-nonGal Abs showed similar binding to PBMCs from pigs of all three haplotypes (SLA(dd), SLA(aa), SLA(cc)). CONCLUSIONS: Anti-nonGal Abs developed after GalT-KO pig heart Tx into baboons. The most potent of these antibodies appeared to detect antigens shared by the three pig haplotypes tested. It remains unclear whether these antibodies are directed towards shared SLA determinants or other pig antigens, and whether antibodies with specificity for allelic SLA determinants are also present, but at lower titer.

Alleles↗

PubMed2006

Role of the thymus in transplantation tolerance in miniature swine: V. Deficiency of the graft-to-thymus pathway of tolerance induction in recipients of cardiac transplants.

BACKGROUND: We have previously shown that both thymic immigrants (graft to thymus pathway) and thymic emigrants (thymus to graft pathway) are involved in tolerance to renal allografts in miniature swine treated with a short course of calcineurin inhibitors. This study investigates the role of these pathways in cardiac transplant survival in recipients treated with a short course of tacrolimus. METHODS: Eleven animals received two-haplotype fully MHC-mismatched cardiac grafts with a 12-day course of tacrolimus. Recipients were thymectomized on day -21 (n=5) or day 0 (n=3), or were left euthymic (n=3). Two of the day -21 thymectomized animals received a day 0 host-MHC matched thymocyte infusion. RESULTS: Euthymic recipients of cardiac grafts treated with an immunosuppressive regimen identical to that previously shown to induce tolerance in euthymic recipients of renal allografts all rejected their grafts. Although no animal became tolerant, animals that were euthymic or thymectomized on day 0, as well as recipients of day 0 host-type thymocyte infusions following thymectomy on day -21, developed donor-specific hyporesponsiveness and maintained their cardiac grafts for markedly prolonged periods. In contrast, all animals thymectomized on day -21 that did not receive thymocyte infusions developed strong antidonor CTL responses and rejected their grafts by day 35. CONCLUSIONS: The graft-to-thymus pathway that plays an important role in tolerance induction to renal allografts appears to be relatively deficient in recipients of cardiac grafts. Strategies to increase donor antigen migration to the host thymus might therefore assist in tolerance induction to cardiac allografts.

Animals↗

PubMed2006

Long-term acceptance of fully allogeneic cardiac grafts by cotransplantation of vascularized thymus in miniature swine.

BACKGROUND: We have previously reported the ability of both thymokidney and vascularized thymic lobe (VTL) allografts to induce transplantation tolerance to renal allografts across a full major histocompatibility complex (MHC) mismatch in thymectomized miniature swine. However, whether vascularized thymus is capable of inducing tolerance to less tolerogeneic organs when it is transplanted simultaneously is not yet known. The present study investigates cardiac allograft survival and the mechanism of long-term acceptance in recipient swine following cotransplantation of VTL and cardiac grafts from fully MHC-mismatched donors. METHODS: Animals received a heart graft, a heart graft and a VTL, or a heart graft and a donor thymocyte infusion. Immunosuppressive regimens consisted of 12 or 28 days of tacrolimus. RESULTS: All animals that received a VTL maintained their grafts significantly longer than their counterparts that received only a heart graft, and those receiving 28 days of tacrolimus maintained their heart grafts long-term. Recipients of a donor thymocyte infusion demonstrated slightly prolonged cardiac graft survival but all rejected their grafts, highlighting the importance of thymic stroma. Cytotoxic T-lymphocyte responses against third-party antigens by cells from tolerant animals showed restriction by both self and donor MHC, whereas responses of controls were restricted to self MHC only. The presence of donor dendritic cells in the VTL grafts and results of co-culture assays suggest that both central and regulatory mechanisms were involved in achieving long-term acceptance. CONCLUSION: This is the first demonstration of the long-term acceptance of fully MHC-mismatched cardiac allografts in large animals.

Animals↗

PubMed2005

Vascularized thymic lobe transplantation in a pig-to-baboon model: a novel strategy for xenogeneic tolerance induction and T-cell reconstitution.

BACKGROUND: This laboratory has previously demonstrated the induction of allogeneic tolerance by vascularized thymic lobe (VTL) transplantation in miniature swine. We report here our initial attempt to induce tolerance by VTL transplantation in the clinically relevant, discordant, pig-to-baboon model of xenotransplantation. METHODS: Six baboons received xenografts of hDAF VTLs. Four of these baboons also received omental thymic tissue implants. All recipients were treated with an immunosuppressive conditioning regimen that included thymectomy, splenectomy, extracorporeal immunoadsorption of anti-alpha Gal antibodies, and T-cell depletion. Two control baboons received sham operations, of which one also received 5x10 hDAF porcine thymocytes/kg intravenously. RESULTS: Transplanted VTL grafts supported early thymopoiesis of recipient-type immature thymocytes, and facilitated engraftment of nonvascularized thymic omental implants. Recipients of the VTL grafts demonstrated donor-specific unresponsiveness in MLR assays, development of peripheral CD45RAhigh/CD4 double positive (DP) cells, and positive cytokeratin staining of thymic stroma in the grafts for 2 months following xenotransplantation. The control baboons did not show these markers of thymic reconstitution. The eventual return of Gal natural antibodies led to the destruction of graft epithelial cells and the rejection of all VTL grafts by 3 months posttransplantation. CONCLUSIONS: VTL transplantation from hDAF swine to baboons induced early thymopoiesis in the recipients and donor-specific cellular unresponsiveness in vitro. When coupled with additional strategies aimed at silencing humoral rejection, VTL transplantation may significantly prolong xenograft survival and result in long-term tolerance.

Animals↗

PubMed2005

alpha1,3-Galactosyltransferase gene-knockout pig heart transplantation in baboons with survival approaching 6 months.

BACKGROUND: The recent generation of alpha1,3-galactosyltransferase gene-knockout (GalT-KO) pigs has allowed investigation of the survival of GalT-KO pig organs in nonhuman primates. METHODS: Heterotopic heart transplantation from GalT-KO pigs was carried out in baboons (n=8) using a human antihuman CD154 monoclonal antibody-based immunosuppressive regimen. RESULTS: In six of the eight cases, graft survival extended to between approximately 2 and 6 months. All grafts developed thrombotic microangiopathy (TM). In particular, the clinical course of one baboon in which the graft functioned for 179 days is summarized. This baboon received aspirin (40 mg on alternate days) from day 4 in addition to heparin, which may have been a factor in the delay of onset and progression of TM and in prolonged graft survival. Maintenance therapy with anti-CD154 mAb, mycophenolate mofetil, and methylprednisolone was associated with persistently low numbers of CD3CD4 and CD3CD8 cells. Despite persisting depletion of these cells, no infectious complications occurred. CONCLUSIONS: It remains to be established whether TM is related to a very low level of natural preformed or T-cell-induced antibody deposition on the graft, inducing endothelial activation and injury, or to molecular incompatibilities in the coagulation mechanisms between pig and baboon, or to both. However, function of a pig organ in a baboon for a period approaching six months, which has not been reported previously, lends encouragement that the barriers to xenotransplantation will eventually be overcome.

Animals↗

PubMed2005

Combination treatment with donor-specific transfusions and cyclosporine a induces long-term survival of cardiac allografts in miniature Swine.

BACKGROUND: To evaluate whether pretransplant donor-specific transfusions (DST) can induce tolerance to cardiac allografts in large animals, heterotopic cardiac transplants were performed across a class I MHC barrier in inbred miniature swine. METHODS: Experimental animals received two DSTs, each containing 1.4x10 viable peripheral blood mononuclear cells, 14 and 7 days prior to transplantation together with a 12-day course of cyclosporine (CyA) (13 mg/kg IV) starting on postoperative day (POD) 0. RESULTS: Untreated (n=2) and DST-only (n=2) treated control animals rejected between POD 6 and 8. Animals treated with CyA alone (n=3) exhibited graft survival to 53, 52 and 59 days. In contrast, the combination of DST and CyA (n=3) led to stable graft function for >200 days. Long-term survivors maintained peripheral CML response against donor antigen. Following DSTs, the donor-specific proliferative response of CD8+ recipient T cells was significantly increased (P=0.011), and a significant number of CD8+ T cells underwent apoptosis (10.1% on POD 0; 5.2% on POD -14; P=0.04). None of the DST-treated animals developed donor-specific antibodies. CONCLUSIONS: These results are the first to demonstrate the ability of DST to induce operational tolerance to cardiac allografts in large animals, and they suggest that peripheral mechanisms of tolerance mediate this effect.

Acute Disease↗

PubMed2005

Long-term acceptance of renal allografts following prenatal inoculation with adult bone marrow.

BACKGROUND: The aim was to investigate if intravascular in utero injection of adult bone marrow into swine fetuses could lead to macrochimerism and tolerance to the donor. METHODS: Outbred Yorkshire sows and boars screening negative for MHC allele SLA of MGH miniature swine were bred. A laparotomy was performed on the sows at 50 days gestation to expose the uterus. Bone marrow harvested from SLA miniature swine was T-cell depleted and injected intravascularly into seventeen fetuses. Flow cytometry was performed to detect donor cells (chimerism) in the peripheral blood after birth. Mixed lymphocyte reactions (MLR) and cell-mediated lympholysis (CML) assays were used to assess the response to donor MHC. Previously frozen skin grafts from the bone marrow donor were placed on the offspring from the first litter. Donor-matched renal transplant from SLA donors were performed on chimeric swine, with and without a short 12-day course of cyclosporine, and one nonchimeric littermate. RESULTS: Nine inoculated offspring demonstrated donor cell chimerism in the peripheral blood and lymphohematopoietic tissues. All animals with detectable chimerism within the first three weeks were consistently nonreactive to donor MHC in vitro. Animals challenged with donor skin grafts displayed prolonged graft survival without producing antidonor antibodies. All chimeric animals accepted donor-matched kidney allografts, even one without cyclosporine. The kidney in the nonchimeric littermate rejected by day 21. CONCLUSIONS: Transplantation of allogeneic adult bone marrow into immunocompetent fetal recipients resulted in chimerism. In utero inoculation led to operational tolerance to the donor's major histocompatibility antigens and long-term acceptance to organ allografts.

Animals↗

PubMed2005

Thrombotic microangiopathic glomerulopathy in human decay accelerating factor-transgenic swine-to-baboon kidney xenografts.

Models of pig-to-baboon xenografting were examined to identify the mechanisms and pathologic characteristics of acute humoral xenograft rejection (AHXR). Thymus and kidney (composite thymokidney) from human decay accelerating factor-transgenic swine were transplanted into baboons (n = 16) that were treated with an immunosuppressive regimen that included extracorporeal immunoadsorption of anti-alphaGal antibody and inhibition of complement activation. Morphologic and immunohistochemical studies were performed on protocol biopsies and graftectomy samples. All renal xenografts avoided hyperacute rejection. However, graft rejection coincided with the increase of anti-alphaGal antibody in the recipient's circulation. The 16 xenografts studied were divided into two groups dependent on the rapid return (group 1) or gradual return (group 2) of anti-alphaGal antibody after immunoadsorption. In group 1 (n = 6), grafts were rejected to day 27 with development of typical AHXR, characterized by marked interstitial hemorrhage and thrombotic microangiopathy in the renal vasculature. In group 2 (n = 10), grafts also developed thrombotic microangiopathy affecting mainly the glomeruli by day 30 but also showed minimal evidence of interstitial injury and hemorrhage. In the injured glomeruli, IgM and C4d deposition, subsequent endothelial cell death and activation with upregulation of von Willebrand factor and tissue factor, and a decrease of CD39 expression developed with the formation of fibrin-platelet multiple microthrombi. In this model, the kidney xenografts, from human decay accelerating factor-transgenic swine, in baboons undergo AHXR. In slowly evolving AHXR, graft loss is associated with the development of thrombotic microangiopathic glomerulopathy. Also, anti-alphaGal IgM deposition and subsequent complement activation play an important role in the mechanism of glomerular endothelial injury and activation and the formation of multiple microthrombi.

Acute Disease↗

PubMed2005

Role of the thymus and kidney graft in the maintenance of tolerance to heart grafts in miniature swine.

BACKGROUND: The authors have examined the mechanism whereby co-transplantation of a kidney and heart from the same donor induces and maintains tolerance to both organs in miniature swine. METHODS: Transplants were performed across a major histocompatibility complex class I mismatch, and recipients received cyclosporine for 12 days. Group 1 animals received heart transplants alone (n=5), and all other groups received both heart and kidney allografts. Group 2 animals received no further intervention (n=2). Group 3 animals underwent transplant nephrectomy 8 days after heart and kidney co-transplantation (n=2). Group 4 animals underwent transplant nephrectomy 100 days after co-transplantation (n=2). Skin grafts were placed on group 4 animals, on one group 3 animal, and on two animals from group 2. Group 5 animals underwent thymectomy 100 days after co-transplantation (n=4). RESULTS: Group 1 animals developed cardiac allograft vasculopathy (CAV) and rejection. Group 2 animals never developed CAV and demonstrated in vitro donor-specific unresponsiveness. Group 3 animals suffered CAV and rejection. Group 4 animals developed CAV without concomitant donor-specific cell-mediated lympholysis reactivity, interstitial rejection, or cessation of graft function. Skin grafts on group 3 and group 4 animals led to fulminant rejection of heart and skin grafts, in contrast to grafts on group 2 animals that had no in vivo effect. Group 5 animals developed CAV but no significant increase in interstitial infiltrates. CONCLUSIONS: Both the kidney and thymus were necessary for maintenance of tolerance to heart allografts.

Animals↗

PubMed2005

In utero bone marrow transplantation induces kidney allograft tolerance across a full major histocompatibility complex barrier in Swine.

BACKGROUND: In utero hematopoietic stem-cell transplantation has been shown to induce donor-specific tolerance in small-animal models. However, tolerance has been difficult to achieve in large-animal studies. METHODS: Outbred swine underwent in utero transplantation of fully major histocompatibility complex (MHC)-mismatched CD3-depleted bone marrow mixed with fresh bone marrow to achieve a final CD3 content of 1.5%. Transplantation was performed at 50 to 55 days' gestation and two animals survived long term and demonstrated multilineage peripheral blood hematopoietic chimerism. These two long-term survivors were analyzed for in vitro evidence of donor-specific tolerance by mixed leukocyte reaction (MLR), cell-mediated lysis (CML), and antibody testing and in vivo by kidney transplantation. RESULTS: Both animals demonstrated in vitro donor-specific unresponsiveness by MLR and CML and did not demonstrate anti-donor antibody production. Donor matched kidney transplants were performed without immunosuppression and functioned for more than 100 days, with no evidence for rejection. CONCLUSIONS: The authors demonstrate conclusively that in utero transplantation of fully MHC-mismatched bone marrow in swine can lead to engraftment and stable multilineage hematopoietic chimerism and tolerance to postnatal donor MHC-matched kidney transplantation without the need for immunosuppression.

Animals↗

PubMed2005

Porcine hematopoietic progenitor cell transplantation in nonhuman primates: a review of progress.

The critical shortage of human donor organs for transplantation would be overcome if a suitable animal, e.g., the pig, could be used as an organ source. There are, however, several immune barriers that have to date resulted in limited function of pig organs transplanted into nonhuman primates. It would be beneficial, and indeed may be essential, to induce a state of tolerance in the primate recipient to the pig organ. In allotransplantation, the successful transplantation of hematopoietic progenitor cells with the development of mixed chimerism is associated with the induction of tolerance toward a donor-specific organ. For some years, this approach has been explored in the pig-to-nonhuman primate model. This experience is briefly reviewed. The problems of natural and elicited anti-pig antibodies, recipient platelet adhesion to pig hematopietic progenitor cells, and the rapid removal of these cells by the host macrophage-phagocytic system are highlighted. Recent experience with the use of hematopoietic cells from pigs homozygous for alpha1,3-galactosyltransferase gene-knockout is reported.

Animals↗

PubMed2005

Stable multilineage chimerism across full MHC barriers without graft-versus-host disease following in utero bone marrow transplantation in pigs.

Stable engraftment of hematopoietic progenitors and multilineage chimerism following in utero bone marrow transplantation could be a promising modality for treatment of prenatally diagnosed blood dyscrasias. For treatment of these diseases, stable chimerism in the myeloid and erythroid lineages is important because it is anticipated that donor-derived cells will compensate for defects in these host lineages. In the present study, a preparation of bone marrow that includes fresh, unmanipulated marrow mixed with T-cell-depleted marrow to achieve 1.5% T-cell content, was injected into the intrahepatic portion of the umbilical vein of porcine fetuses at mid-gestation. Donor hematopoietic progenitor cell engraftment was assessed in fetal liver and recipient bone marrow postnatally by donor-specific polymerase chain reaction of colony-forming units. Chimerism was assessed in lymphoid tissues and peripheral blood by flow cytometry. Graft-versus-host disease (GVHD) was assessed by histological analysis of biopsies of skin, bone marrow, liver, and intestine. In this report, we demonstrate that stable multilineage chimerism across a full major histocompatibility complex disparity can be achieved without GVHD through in utero bone marrow transplantation.

Animals↗

PubMed2005

Heart and en-bloc thymus transplantation in miniature swine.

BACKGROUND: Donor-specific tolerance to organ allografts might be induced by cotransplantation of a sufficient amount of vascularized donor thymus. To facilitate donor thymus-induced cardiac allograft tolerance, we have developed a novel technique for heart and en-bloc thymus transplantation in swine. METHODS: Donor heart and en-bloc thymus grafts were prepared by a technique that preserves the entire arterial supply and venous drainage of the right thymic lobe. En-bloc grafts (n = 4) were transplanted heterotopically into the abdomens of major histocompatibility complex-matched miniature swine. Recipients received 12 days of cyclosporine intravenously. Grafts were monitored by palpation, electrocardiographic monitoring, and periodic open biopsy. Engraftment of the donor thymus was demonstrated by measuring the proportion of recipient-type thymocytes in the donor thymus with flow cytometry. RESULTS: All of the heart and en-bloc thymus grafts had normal cardiac contractility and immediate perfusion of the thymus. All en-bloc grafts were accepted for more than 200 days without significant acute cellular rejection or cardiac allograft vasculopathy. Thymic tissue of en-bloc grafts displayed normal architecture and supported thymopoiesis of recipient-type cells. CONCLUSION: We have validated a new technique of donor thymus transplantation that could have utility in human heart transplantation.

Animals↗

PubMed2005

Host thymectomy and cyclosporine lead to unstable skin graft tolerance after class I mismatched allogeneic neonatal thymic transplantation in mice.

BACKGROUND: Our laboratory has demonstrated that xenogeneic porcine thymus tissue grafted in thymectomized (ATX) and T cell-depleted mice induces donor-specific tolerance. Recipient thymectomy is essential for the success of tolerance induction. In contrast, studies in pigs grafted with non-vascularized allogeneic class I mismatched thymus tissue under the cover of CyA have shown that removal of host thymus is detrimental to thymic graft survival. To determine the requirements for nonvascularized allogeneic class I-mismatched thymic engraftment in mice, we performed thymic allotransplantation under the cover of CyA. MATERIALS AND METHODS: Euthymic and ATX B10.MBR mice received class I mismatched B10.AKM neonatal mouse thymus (NMTHY) tissue under the kidney capsule with or without a short course of CyA. The grafts were allowed to engraft for two and a half months before exploratory laparotomy was performed to evaluate them. Three months after the thymic transplant, mice were challenged with donor-specific skin grafts to assess tolerance. One month after donor-specific skin grafting, they received third party B10.BR skin grafts. Cellular anti-donor immune responses were studied at the time of euthanasia. RESULTS: CyA-treated ATX and euthymic control mice showed good engraftment of the allogeneic thymic tissue at the time of exploratory laparotomy, whereas non-CyA-treated ATX and euthymic controls had rejected the grafts. The CyA-treated ATX B10.MBR mice accepted donor-specific skin grafts, but rejected them following a challenge with third party B10.BR skin grafts. Untreated ATX and euthymic mice and 6 of 7 CyA-treated euthymic mice rejected donor skin within 15 days. Mixed lymphocyte reactions did not show an increased anti-donor response, but CML clearly showed sensitization and increased killing activity against donor-type targets in these mice. CONCLUSION: Allogeneic thymic transplantation across a class I MHC barrier under the cover of CyA induces a metastable state of tolerance in mice. To achieve this state, ATX of the recipient is required.

Animals↗