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Abrogation of chronic rejection in rat model system involves modulation of the mTORC1 and mTORC2 pathways. Transplantation 2013; 96:782-90. [PMID: 23985719 DOI: 10.1097/tp.0b013e3182a2034f] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Current immunosuppressive regimens fail to avert chronic rejection (CR) of transplanted organs; however, selective targeting of actin-cytoskeletal regulators decreases T-cell motility and abrogates CR in rat model system. Administration of mutated class I major histocompatibility complex molecules or selective targeting of the RhoA pathway, which controls T-cell cytoskeletal activity, using Y27632 (a selective Rock1 inhibitor) resulted in reduced T-cell infiltration and abrogation of CR as judged from the neointimal index (13.9±19.7 vs. 45±37.5; P<0.001) and the number of affected vessels (30% vs. 60%; P<0.01). Here, we examined the role of mammalian target of rapamycin (mTOR) pathway in inhibition of CR. METHODS A mutated class I major histocompatibility complex molecule that eliminates CR was delivered into ACI recipients of Wistar-Furth hearts at the time of transplantation with subtherapeutic cyclosporine (10 mg/kg on days 0-2). Controls included untreated and cyclosporine A-treated (10 mg/kg on days 0-2) heart allograft recipients. RESULTS Western blotting and immunostaining showed that rat heart allografts with abolished CR exhibited down-regulation of the RAPA-sensitive mTORC1 components such as mTOR and Raptor and down-regulation of the RAPA-insensitive mTORC2 elements Rictor and Sin1. The mTOR regulator Deptor and its downstream target Rac1 were also inhibited. CONCLUSIONS Abrogation of CR in rat model system involves modulation of two mTOR pathways: a RAPA-sensitive mTORC1 pathway regulating cellular proliferation and a RAPA-insensitive mTORC2 pathway regulating T-cell motility. Selective targeting of T-cell actin cytoskeletal pathways shows potential for pathway-targeted immunosuppression therapies.
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Zhang L, Kloc M, Tejpal N, You J, Cordero-Reyes AM, Youker KA, Ghobrial RM. Rock1 Inhibitor Abrogates Chronic Rejection in Rat Cardiac Model System. ACTA ACUST UNITED AC 2012. [DOI: 10.4236/ojots.2012.24012] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Skelton TS, Kloc M, Ghobrial RM. Molecular and cellular pathways involved in the therapeutic functions of MHC molecules; a novel approach for mitigation of chronic rejection. ACTA ACUST UNITED AC 2011. [DOI: 10.4236/oji.2011.12003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Skelton TS, Tejpal N, Gong Y, Kloc M, Ghobrial RM. Downregulation of RhoA and changes in T cell cytoskeleton correlate with the abrogation of allograft rejection. Transpl Immunol 2010; 23:185-93. [PMID: 20619345 DOI: 10.1016/j.trim.2010.06.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Revised: 06/15/2010] [Accepted: 06/16/2010] [Indexed: 12/15/2022]
Abstract
Proper actin cytoskeleton architecture and dynamics are indispensable for events in the immunological response such as T cell migration, redistribution of T cell receptors, and interaction with antigen presenting cells. Thus, T cell activation, downstream signaling events and effector functions are all actin-dependent. Actin cytoskeleton architecture and dynamics are regulated by proteins belonging to the superfamily of small GTP-binding proteins, such as RhoA GTPase. We previously showed that the administration of an MHC class I allochimeric molecule [alpha1h1/u]-RT1.Aa, which contains donor-type (Wistar Furth, WF; RT1u) immunogenic epitopes displayed on recipient-type (ACI, RT1a) sequences, to the ACI recipient of heterotopic WF heart resulted in the restriction of the TCR repertoire, inhibition of T cell infiltration into the heterotopic cardiac allografts, abrogation of acute and chronic rejection, and induction of indefinite survival of the allograft. Here we show that the allochimeric molecule treatment caused downregulation of RhoA GTPase in T cells. This resulted in dramatic changes in the distribution of actin and the actin-binding protein, Hip55, in these cells, which in turn, inhibited T cell infiltration into the graft. This indicates that the immunosuppressive activity of the allochimeric molecule is achieved via downregulation of the RhoA pathway and disruption of the proper organization of T cell actin cytoskeleton to inhibit T cell functions such as motility and/or TCR signaling events.
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Affiliation(s)
- T Spencer Skelton
- Department of Surgery, The Methodist Hospital and The Methodist Hospital Research Institute, Houston TX, USA
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Lisik W, Gong Y, Tejpal N, Skelton TS, Bremer EG, Kloc M, Ghobrial RM. Intragraft gene expression profile associated with the induction of tolerance by allochimeric MHC I in the rat heart transplantation model. Genesis 2010; 48:8-19. [PMID: 19882666 DOI: 10.1002/dvg.20574] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The MHC class I allochimeric protein containing donor-type epitopes on recipient-type heavy chains induces indefinite survival of heterotopic cardiac allografts in rats. We analyzed gene expression profile of heart allograft tissue. Mutated peptide [alpha1h1/u]-RT1.Aa that contains donor-type (Wistar Furth, WF; RT1u) immunogenic epitopes displayed on recipient-type (ACI, RT1a) was delivered into ACI recipients of WF hearts at the time of transplantation in addition to a 3 days course of oral cyclosporine. Microarray analysis was performed using Affymetrix Rat 230 2.0 Microarray. Allochimeric molecule treatment caused upregulation of genes involved in structural integrity of heart muscle, downregulation of IL-1beta a key modulator of the immune response, and downregulation of partitioning defective six homolog gamma PAR6, which is involved in T cell polarity, motility, and ability to scan dendritic cells (DC). These indicate that the immunosuppressive function of allochimeric molecule and/or the establishment of allograft tolerance depend on the induction of genes responsible for the heart tissue integrity, the suppression of cytokine pathway(s), and possibly the impairment of T cells mobility and their DC scanning ability. These novel findings may have important clinical implications for inhibition of chronic rejection in transplant recipients.
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Affiliation(s)
- Wojciech Lisik
- Department of General and Transplantation Surgery, Warsaw Medical University, Warsaw, Poland
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Liu D, Shen XD, Zhai Y, Lam W, Liao J, Busuttil RW, Ghobrial RM. Intragraft selection of the T cell receptor repertoire by class I MHC sequences in tolerant recipients. PLoS One 2009; 4:e6076. [PMID: 19562081 PMCID: PMC2700265 DOI: 10.1371/journal.pone.0006076] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2009] [Accepted: 06/04/2009] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Allograft tolerance of ACI (RT1(a)) recipients to WF (RT1(u)) hearts can be induced by allochimeric class I MHC molecules containing donor-type (RT1A(u)) immunogenic epitopes displayed on recipient-type (RT1A(a)) sequences. Here, we sought the mechanisms by which allochimeric sequences may affect responding T cells through T cell receptor (TCA) repertoire restriction. METHODOLOGY/PRINCIPAL FINDINGS The soluble [alpha(1h) (u)]-RT1.A(a) allochimeric molecule was delivered into ACI recipients of WF hearts in the presence of sub-therapeutic dose of cyclosporine (CsA). The TCR Vbeta spectrotyping of the splenocytes and cardiac allografts showed that the Vbeta gene families were differentially expressed within the TCR repertoire in allochimeric- or high-dose CsA-treated tolerant recipients at day +5 and +7 of post-transplantation. However, at day 30 of post-transplantation the allochimeric molecule-treated rats showed the restriction of TCR repertoire with altered dominant size peaks representing preferential clonal expansion of Vbeta7, Vbeta11, Vbeta13, Vbeta 14, and Vbeta15 genes. Moreover, we found a positive correlation between the alteration of Vbeta profile, restriction of TCR repertoire, and the establishment of allograft tolerance. CONCLUSIONS Our findings indicate that presentation of allochimeric MHC class I sequences that partially mimic donor and recipient epitopes may induce unique tolerant state by selecting alloresponsive Vbeta genes.
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Affiliation(s)
- Dahai Liu
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Xiu-Da Shen
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Yuan Zhai
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Wengsi Lam
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Jingying Liao
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Ronald W. Busuttil
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine, Los Angeles, California, United States of America
| | - Rafik M. Ghobrial
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine, Los Angeles, California, United States of America
- Department of Surgery, The Methodist Hospital, Houston, Texas, United States of America
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Easterfield AJ, Delriviere L, Wallduck MS, Sivaganesh S, Bradley JA, Bolton EM. Alloantibody-associated chronic rejection of MHC class I-disparate heart grafts is modulated by intravenous soluble donor alloantigen. Transpl Immunol 2007; 18:138-41. [DOI: 10.1016/j.trim.2007.05.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Accepted: 05/21/2007] [Indexed: 11/25/2022]
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Semiletova NV, Shen XD, Feldman DM, Gao F, Mhoyan A, Liu D, Busuttil RW, Kupiec-Weglinski JW, Ghobrial RM. Class I MHC allochimeric presentation of composite immunogenic and self epitopes induces tolerance to genetically diverse rat strains. Cell Immunol 2007; 248:48-58. [PMID: 17936255 PMCID: PMC3699404 DOI: 10.1016/j.cellimm.2007.04.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2006] [Accepted: 04/16/2007] [Indexed: 10/22/2022]
Abstract
Functional topography of rat class I major histocompatibility complex (MHC) molecule was studied. The alpha1-helical sequences that are shared by class I RT1.A(l) and RT1.A(u) were substituted in the RT1.A(a) molecule to produce the composite [alpha(1h)(l/u)]-RT1.A(a) MHC class I allochimeric molecule. Dominant immunogenic epitopes that induce accelerated rejection were identified within the hypervariable regions of the alpha1 domain of RT1.A(a), RT1.A(l), and RT1.A(u). Peri-transplant portal venous delivery of MHC class I allochimeric proteins, that included composite alpha1 helical immunodominant epitopes of RT1.A(u) and RT1.A(l), induced donor-specific tolerance to RT1(u) (Wistar Furth, WF) and RT1(l) Lewis, LEW) disparate cardiac allografts in ACI (RT1(a)) hosts. Allochimeric generated tolerance was characterized by absence of T cell deletion or anergy. Donor specific IgM allo-Abs was not detected, while IgG alloresponse was markedly attenuated in sera of tolerant hosts. Further, long-term allografts in allochimeric-conditioned hosts exhibited moderate B cell infiltration when compared to rejecting controls. Analysis of intragraft cytokines revealed selective upregulation of IL-10 and marked inhibition of IL-2, IFN-gamma, and IL-4. Our findings indicate the emergence of a peripherally induced tolerant state, afforded by the novel approach of soluble class I allochimeric conditioning that presents donor immunogenic epitopes in the context of recipient class I determinants.
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Affiliation(s)
- Natalya V. Semiletova
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Xiu-Da Shen
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Daniel M. Feldman
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Feng Gao
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Ana Mhoyan
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Dhai Liu
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Ronald W. Busuttil
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Jerzy W. Kupiec-Weglinski
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA
| | - Rafik M. Ghobrial
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, CA
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Segovia J, Gómez-Bueno M, Alonso-Pulpón L. Treatment of allograft vasculopathy in heart transplantation. Expert Opin Pharmacother 2006; 7:2369-83. [PMID: 17109612 DOI: 10.1517/14656566.7.17.2369] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Cardiac allograft vasculopathy remains one of the main causes of morbidity and mortality after heart transplantation, although its impact is becoming somewhat smaller as prophylactic measures are implemented. Advances in the understanding of the molecular and cellular mechanisms involved in the genesis and development of cardiac allograft vasculopathy are opening ways for new diagnostic and therapeutic strategies. Successful prophylaxis of the early stages of the disease has been demonstrated with the use of newer immunosuppressive agents, such as sirolimus and everolimus, that will probably be included in future protocols. For most patients with established cardiac allograft vasculopathy, currently available revascularisation methods and retransplantation are not appropriate options. Antiproliferative agents could provide significant improvement in terms of symptom relief and prognosis, but their definite value must be proven in well-designed trials.
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Affiliation(s)
- Javier Segovia
- Unidad de Trasplante Cardiaco, Hospital Universitario Puerta de Hierro, C/S. Martín de Porres, 4, 28035 Madrid, Spain.
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Semiletova NV, Shen XD, Baibakov B, Feldman DM, Mukherjee K, Frank JM, Stepkowski SM, Busuttil RW, Kupiec-Weglinski JW, Ghobrial RM. Inhibition of Chronic Rejection by Antibody Induced Vascular Accommodation in Fully Allogeneic Heart Allografts. Transplantation 2005; 80:1535-40. [PMID: 16371921 DOI: 10.1097/01.tp.0000188952.10692.18] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
BACKGROUND The potential role of altered antibody responses as an effector protective mechanism to induce graft accommodation has been widely investigated in xenogeneic responses. Here we investigate the protective effects of antibody binding to vascular endothelium in a fully mismatched allogeneic model of heart transplantation. METHODS ACI recipients of WF cardiac grafts were treated either with allochimeric [alpha1h ]-RT1.A class I major histocompatibility complex (MHC) extracts (1 mg/rat, p.v. day 0) or high dose of CsA (10 mg/kg/day, p.o., day 0-6). Cardiac allografts were evaluated at 100 days posttransplant by immunohistology for evidence of chronic rejection and/or vascular accommodation. Activation of apoptotic or antiapoptotic mechanisms was verified by DNA fragmentation (TUNEL) analysis. RESULTS Allochimeric therapy resulted in inhibition of chronic rejection, absence of neointimal formation and induction of vascular accommodation of fully allogeneic WF hearts in ACI hosts. Such accommodation was evident by IgG and IgM vascular endothelial binding and marked reduction of DNA fragmentation. In contrast, CsA therapy resulted in marked neointimal proliferation, without evidence of vascular accommodation. Immunohistochemical analysis failed to demonstrate vascular endothelial antibody binding. Further, severe chronic rejection following CsA treatment was accompanied by marked DNA fragmentation. CONCLUSION Alteration of humoral immunity induces vascular accommodation in allogeneic transplantation. Vascular accommodation is the underlying mechanism for inhibition allograft vasculopathy following allochimeric MHC class I therapy.
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Affiliation(s)
- Natalya V Semiletova
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Los Angeles, CA 90095-7054, USA
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Liu D, Shen XD, Fang Z, Gao F, Semiletova N, Cao MJ, Busuttil RW, Kupiec-Weglinski JW, Ghobrial RM. Identification of Early Tolerance Regulator Genes Induced by Allochimeric Therapy Using Microarray-Based Genomewide Scan. Transplant Proc 2005; 37:1942-3. [PMID: 15919512 DOI: 10.1016/j.transproceed.2005.03.147] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have demonstrated that peri- or postoperative delivery of allochimeric [a1h(u)]-RT1.A(a) class I major histocompatibility complex molecules with donor-type (RT1A(u)) immunogenic epitopes presented in recipient-type (RT1A(a)) sequences induced donor-specific tolerance in ACI (RT1a) recipients of WF (RT1u) heart allografts. A genomic scan during the early posttransplant period was performed to elucidate the underlying operative mechanisms. A rat genome study after transplantation was carefully designed using Affymetrix Rat Genome 230 2.0 Array. The allochimeric treatment group is 3-day cyclosporine (CsA)-treated ACI recipients that accepted Wistar Furth RT1u cardiac allografts with postoperative dosage of allochimeric molecules, while the control is 3-day CsA-treated ACI recipients of WF cardiac allografts. All the samples were harvested 5 days after heart transplant as the early stage of tolerance detection. Following array data normalization and modeling, we compared the above two treatment groups and identified a total of 250 tolerance regulator genes induced by allochimeric molecules only.
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Affiliation(s)
- D Liu
- Dumont-UCLA Transplant Center, Department of Surgery, David Geffen School of Medicine, Los Angeles, California, USA
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Semiltova N, Shen XD, Fishbein MC, Gao F, Slomowitz SJ, Jiao Q, Mukherjee K, Busuttil RW, Kupiec-Weglinski JW, Ghobrial RM. Posttransplant administration of allochimeric major histocompatibility complex class-I-molecules induces true transplantation tolerance. Transplantation 2003; 75:550-3. [PMID: 12605125 DOI: 10.1097/01.tp.0000046942.02001.26] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Allochimeric class-I major histocompatibility complex (MHC) molecules that contain donor-type immunogenic epitopes displayed on recipient-type sequences were shown to induce transplantation tolerance when administered at the time of transplantation. Here, we investigated the ability of posttransplant allochimeric administration to induce tolerance and concomitantly inhibit chronic rejection. METHODS Allochimeric (alpha1h(1/u))-RT1.Aa class-I MHC antigenic extracts were administered by way of the portal vein into ACI recipients of Wistar-Firth (WF) hearts at days +3, +7, and +10 posttransplantation in conjunction with subtherapeutic oral cyclosporine. RESULTS Delayed posttransplant allochimeric administration induced donor-specific transplantation tolerance to rat cardiac allografts. In contrast, delayed delivery of unaltered donor- or recipient-type MHC extracts failed to prolong allograft survival. In addition, histopathologic examination or estimation of transplant vascular sclerosis by neointimal index assessment, following delayed allochimeric therapy, revealed intact global architecture and minimal intimal thickening, respectively. CONCLUSION Allochimeric MHC class-I therapy is a unique and novel clinically applicable approach for induction of "true" transplantation tolerance where chronic rejection is concomitantly abrogated.
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Affiliation(s)
- Natalya Semiltova
- The Dumont-UCLA Transplant Center, Division of Liver and Pancreas Transplantation, Department of Surgery, David Geffen School of Medicine at UCLA, Los Angeles, California 90095-7054, USA
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Semiletova N, Shen XD, Gao F, Slomowitz SJ, Jiao Q, Busuttil RW, Kupiec-Weglinski JW, Ghobrial RM. Regulatory T cells induced by allochimeric major histocompatability class I therapy inhibit allograft apoptosis. Transplant Proc 2002; 34:1402. [PMID: 12176415 DOI: 10.1016/s0041-1345(02)02904-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- N Semiletova
- The Dumont-UCLA Transplant Center, University of California-Los Angeles, 10833 LeConte Avenue, Los Angeles, CA 90095-7054, USA
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Abstract
Chronic allograft rejection is a slowly progressive, insidious process in which the host immune system continues to mount an immunological attack on a transplanted organ, ultimately resulting in the failure of the graft. To varying degrees, all solid organ grafts are at risk for chronic rejection and undergo a stereotypic process of injury and inflammation, eventually leading to parenchymal fibrosis. The clinical consequences of chronic rejection are particularly apparent in thoracic transplantation, where both patient and graft survival decline steadily over time and the opportunities for re-transplantation or long-term extracorporeal support are limited. A variety of antigen-dependent and antigen-independent factors are known to modulate the propensity for an organ to undergo chronic rejection. Recent clinical and laboratory research has suggested that distinct immunologic mechanisms may underlie the process of chronic rejection. Ultimately, strategies to induce long-term tolerance to alloantigens will be necessary to prevent chronic rejection and to abrogate the deleterious sequelae of chronic immunosuppression.
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Affiliation(s)
- James S Allan
- Division of Thoracic Surgery, Department of Surgery, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA
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