The Experts below are selected from a list of 18207 Experts worldwide ranked by ideXlab platform
Angus W. Thomson - One of the best experts on this subject based on the ideXlab platform.
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mammalian target of rapamycin inhibition and alloantigen specific regulatory t cells synergize to promote long term Graft survival in immunocompetent recipients
Journal of Immunology, 2010Co-Authors: Giorgio Raimondi, Zhiliang Wang, Tina L Sumpter, Benjamin M Matta, Mahesh Pillai, Natasha Corbitt, Yoram Vodovotz, Angus W. ThomsonAbstract:Minimization of immunosuppression and donor-specific tolerance to MHC-mismatched organ Grafts are important clinical goals. The therapeutic potential of regulatory T cells (Tregs) has been demonstrated, but conditions for optimizing their in vivo function posttransplant in nonlymphocyte-depleted hosts remain undefined. In this study, we address mechanisms through which inhibition of the mammalian target of rapamycin (Rapa) synergizes with alloantigen-specific Treg (AAsTreg) to permit long-term, donor-specific Heart Graft survival in immunocompetent hosts. Crucially, immature allogeneic dendritic cells allowed AAsTreg selection in vitro, with minimal expansion of unwanted (Th17) cells. The rendered Treg potently inhibited T cell proliferation in an Ag-specific manner. However, these AAsTreg remained unable to control T cells stimulated by allogeneic mature dendritic cells, a phenomenon dependent on the release of proinflammatory cytokines. In vivo, Rapa administration reduced danger-associated IL-6 production, T cell proliferation, and Graft infiltration. Based on these observations, AAsTreg were administered posttransplant (day 7) in combination with a short course of Rapa and rendered >80% long-term (>150 d) Graft survival, a result superior to that achieved with polyclonal Treg. Moreover, Graft protection was alloantigen-specific. Significantly, long-term Graft survival was associated with alloreactive T cell anergy. These findings delineate combination of transient mammalian target of Rapa inhibition with appropriate AAsTreg selection as an effective approach to promote long-term organ Graft survival.
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rapamycin conditioned dendritic cells are poor stimulators of allogeneic cd4 t cells but enrich for antigen specific foxp3 t regulatory cells and promote organ transplant tolerance
Journal of Immunology, 2007Co-Authors: Heth R Turnquist, Angus W. Thomson, Zhiliang Wang, Giorgio Raimondi, Alan F Zahorchak, Ryan T FischerAbstract:The ability of dendritic cells (DC) to regulate Ag-specific immune responses via their influence on T regulatory cells (Treg) may be key to their potential as therapeutic tools or targets for the promotion/restoration of tolerance. In this report, we describe the ability of maturation-resistant, rapamycin (RAPA)-conditioned DC, which are markedly impaired in Foxp3− T cell allostimulatory capacity, to favor the stimulation of murine alloantigen-specific CD4+CD25+Foxp3+ Treg. This was distinct from control DC, especially following CD40 ligation, which potently expanded non-Treg. RAPA-DC-stimulated Treg were superior alloantigen-specific suppressors of T effector responses compared with those stimulated by control DC. Supporting the ability of RAPA to target effector T and B cells, but permit the proliferation and suppressive function of Treg, an infusion of recipient-derived alloantigen-pulsed RAPA-DC followed by a short postoperative course of low-dose RAPA promoted indefinite (>100 day) Heart Graft survival. This was associated with Graft infiltration by CD4+Foxp3+ Treg and the absence of transplant vasculopathy. The adoptive transfer of CD4+ T cells from animals with long-surviving Grafts conferred resistance to rejection. These novel findings demonstrate that, whereas maturation resistance does not impair the capacity of RAPA-DC to modulate Treg, it profoundly impairs their ability to expand T effector cells. A demonstration of this mechanism endorses their potential as tolerance-promoting cellular vaccines.
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The Role of Foxp3 Regulatory T Cells in Liver Transplant Tolerance
Transplantation proceedings, 2006Co-Authors: W. Li, K Carper, X.x. Zheng, Christian S. Kuhr, D.l. Perkins, Angus W. Thomson, Jorge Reyes, Y. Liang, James D PerkinsAbstract:Abstract The liver has long been considered a tolerogenic organ that favors the induction of peripheral tolerance. The mechanisms underlying liver tolerogenicity remain largely undefined. In this study, we characterized Foxp3-expressing CD4 + CD25 + regulatory T cells (Treg) in liver alloGraft recipients and examined the role of Treg in inherent liver tolerogenicity by employing the mouse spontaneous liver transplant tolerance model. Orthotopic liver transplantation was performed from C57BL/10 (H2 b ) to C3H/HeJ (H2 k ) mice. The percentage of CD4 + CD25 + Treg was expanded in the liver Grafts and recipient spleens from day 5 up to day 100 posttransplantation, associated with high intracellular Foxp3 and CTLA4 expression. Immunohistochemistry further demonstrated significant numbers of Foxp3 + cells in the liver Grafts and recipient spleens and increased transforming growth factor β expression in the recipient spleens throughout the time courses. Adoptive transfer of spleen cells from the long-term liver alloGraft survivors significantly prolonged donor Heart Graft survival. Depletion of recipient CD4 + CD25 + Treg using anti-CD25 monoclonal antibody (250 μg/d) induced acute liver alloGraft rejection, associated with elevated anti-donor T-cell proliferative responses, CTL and natural killer activities, enhanced interleukin (IL)-2, interferon-γ, IL-10, and decreased IL-4 production, and decreased T-cell apoptotic activity in anti-CD25-treated recipients. Moreover, CTLA4 blockade by anti-CTLA4 monoclonal antibody administration exacerbated liver Graft rejection when combined with anti-CD25 monoclonal antibody. Thus, Foxp3 + CD4 + CD25 + Treg appear to underpin spontaneous acceptance of major histocompatability complex– mismatched liver alloGrafts in mice. CTLA4, IL-4, and apoptosis of alloreactive T cells appear to contribute to the function of Treg and regulation of Graft outcome.
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rapamycin treated alloantigen pulsed host dendritic cells induce ag specific t cell regulation and prolong Graft survival
American Journal of Transplantation, 2005Co-Authors: Timucin Taner, Holger Hackstein, Zhiliang Wang, Adrian E Morelli, Angus W. ThomsonAbstract:Tolerogenic properties of dendritic cells (DC), particularly those in the immature state, and their therapeutic potential are increasingly being recognized. Among several distinct approaches to generate stably immature DC, pharmacologic manipulation stands out as a promising and clinically applicable option. We have shown recently that the immunophilin ligand rapamycin (Rapa) can inhibit DC maturation and their effector functions. Here, we examined the impact of Rapa exposure on subsequent alloantigen (Ag) presentation by myeloid DC via the indirect pathway. Rapa-treated, allogeneic lysate-pulsed host DC (Rapa-DC) were inferior stimulators of syngeneic T cells, compared to lysate-pulsed control DC. Rapa exposure did not block alloAg uptake by DC nor impair their in vivo homing to splenic T cell areas after adoptive transfer. T cells primed by Rapa-treated, alloAg-pulsed DC showed decreased capacity to produce IL-2 and IFNγ, and were hyporesponsive to subsequent challenge via both the direct and indirect pathways, in an Ag-specific manner. When infused 1 week before transplantation, these Rapa-DC significantly prolonged alloAg-specific Heart Graft survival. This effect was reversed by systemic IL-2 administration but enhanced by either repeated infusion of the cells or a short post-transplant course of FK506. These therapeutic effects, achieved by targeting both major pathways of allorecognition, provide the basis for a clinically applicable strategy to suppress Graft rejection.
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Plasmacytoid dendritic cell precursors induce allogeneic T-cell hyporesponsiveness and prolong Heart Graft survival.
American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons, 2005Co-Authors: Masanori Abe, Zhiliang Wang, An De Creus, Angus W. ThomsonAbstract:Dendritic cell (DC) precursors were propagated from C57BL/10 (B10; H2b) mouse bone marrow in fms-like tyrosine kinase 3 ligand. Cosignaling molecule (B7-1/B7-2 and B7-H1) expression and stimulatory capacity of precursor (pre)-plasmacytoid (p)DC (CD11c+B220+CD11b−CD19−) and classic myeloid DC (MDC) for allogeneic (C3H; H2k) T cells were compared. Unstimulated pre-pDC exhibited very low levels of surface MHC class II and classic costimulatory molecules (B7-1/B7-2), whereas a minor population expressed B7-H1 at levels higher than on MDC. The pre-pDC were ineffective T-cell stimulators and induced nonspecific hyporesponsiveness to rechallenge with donor alloantigens in vitro and in vivo. Following stimulation with CpG-oligonucleotide (CpG-ODN), B7 molecule expression was upregulated on pre-pDC, however the ratio between coinhibitory (B7-H1) and costimulatory (B7-1/B7-2) signals was much higher (five- to six-fold) on pre-pDC than MDC. Blockade of B7-H1 expression on pDC increased their T-cell allostimulatory capacity significantly. A single preoperative infusion of C3H hosts with pre-pDC prolonged B10 Heart Graft survival significantly but nonspecifically compared with untreated mice (median survival times 22 vs. 9 days, respectively). Thus, pre-pDC of donor origin have potential to regulate T-cell responses to alloantigens and can prolong organ Graft survival.
Kathryn J. Wood - One of the best experts on this subject based on the ideXlab platform.
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Spleen plays an important role in maintaining tolerance after removal of the vascularized Heart Graft.
Transplantation, 2007Co-Authors: Eiichi Chosa, Kimikazu Hamano, Kathryn J. Wood, Masaki Hara, Akira Watanabe, Yasunori Matsuzaki, Kunihide Nakamura, Toshio OnitsukaAbstract:Background. This study addresses the question of the mechanism for maintaining tolerance to donor alloantigen in the absence of antigen and the role of secondary lymphoid tissues. Methods. Depleting anti-CD4 antibody administration in conjunction with allogeneic Heart transplantation generates donor-specific operational tolerance. Primary C57BL/6 Heart Grafts were transplanted into the neck cavity of the anti-CD4 antibody pretreated C3H/He mice. At day 50, functioning Heart Grafts were removed from tolerant mice. At day 100, a secondary C57BL/6 or a third-party Heart was transplanted into the abdomen. Results. Anti-CD4 antibody therapy induced CD4 + CD25 + regulatory T cells by 50 days after transplantation, as depleting anti-CD25 treatment in tolerant mice abrogated Graft prolongation when spleen leukocytes were adoptively transferred to syngeneic mice. Tolerance was maintained by CD4 + CD25 + regulatory T cells via a CTLA-4 signal at 100 days, even after removal of the primary Graft at day 50. Administration of anti-CD25 antibody immediately after removal of the primary Graft did not break tolerance, as five out of six second alloGrafts transplanted at day 100 were accepted. Anti-CD25 antibody therapy in conjunction with splenectomy, but not thymectomy, immediately after removal of primary Heart Grafts at day 50 broke tolerance at day 100; all alloGrafts were rejected. Conclusion. The spleen is important in maintaining CD4 + CD25 + regulatory T cells after primary alloGraft removal.
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Evidence that the continued presence of the organ Graft and not peripheral donor microchimerism is essential for maintenance of tolerance to alloantigen in vivo in anti-CD4 treated recipients.
Transplantation, 1996Co-Authors: Kimikazu Hamano, Mary-anne Rawsthorne, Andrew Bushell, Peter J. Morris, Kathryn J. WoodAbstract:The source of donor alloantigen required to maintain tolerance in vivo was evaluated in anti-Cd4 monoclonal antibody (mAb) treated mice. Treatment with a depleting anti-Cd4 mAb at the time of transplantation (day -1, 0) induces tolerance to C57BL/10 (H2 b ) vascularized cardiac alloGrafts in C3H.He (H2 k ) mice (1). The presence of the vascularized alloGraft was found to be essential for the induction of tolerance in this experimental model ; it is the only source of donor alloantigen during the induction phase of unresponsiveness (0-50 days). In the maintenance phase (>50 days) donor alloantigen is potentially available from two sources, the organ Graft itself or donor cells that have migrated out of the Graft and are resident in the periphery (donor microchimerism). We show that the vascularized cardiac alloGraft is essential for the maintenance of tolerance to donor alloantigen in vivo. When the primary Heart Graft remained in situ, tolerance to donor alloantigens, as assessed by the survival of a second Heart Graft, was maintained indefinitely (>250 days) (MST of second C57 Heart Grafts >100 days). However, when the primary Heart Graft was removed 50 days after transplantation, a time point when tolerance to donor alloantigens was demonstrable in vivo, tolerance was lost 200 days later (MST of second C57 Heart Grafts 31 days). No evidence of donor microchimerism in the recipient was obtained using allele specific polymerase chain reaction (pcr) analysis for donor class I antigen. Persistence of donor alloantigen in the form of the vascularized organ Graft is therefore required for both the induction and maintenance of tolerance to alloantigen in vivo in this experimental model.
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kinetics of induction of transplantation tolerance with a nondepleting anti cd4 monoclonal antibody and donor specific transfusion before transplantation a critical period of time is required for development of immunological unresponsiveness
Transplantation, 1996Co-Authors: D Saitovitch, Andrew Bushell, Peter J. Morris, Duncan W Mabbs, Kathryn J. WoodAbstract:The combination of a depleting anti-Cd4 3 monoclonal antibody (mAb) and a single donor-specific transfusion before transplantation has been shown to induce operational transplantation tolerance in the majority of cardiac alloGraft recipients in a mouse model. To examine a protocol which might be more clinically relevant, we have modified this tolerance-inducing protocol by substituting the depleting with a nondepleting anti-Cd4 mAb. We show that this form of pretreatment can also induce immunologic unresponsiveness in most recipients (C3H/He, H2 k ), provided a critical period of time, in this case 28 days, is allowed between pretreatment and transplantation of a fully mismatched Heart Graft (H2 b ). When only 1 or 2 weeks were allowed between pretreatment and transplantation, only slight Graft prolongation was obtained when compared with recipients receiving anti-Cd4 mAb alone, at these time points. Maintenance of tolerance in this model was due, at least in part, to active mechanisms as immunologic unresponsiveness to donor antigens could be transferred to naive syngeneic mice by splenocytes from recipients bearing long-term functioning Grafts. These findings suggest that a population of regulatory cells develop after pretreatment with nondepleting anti-Cd4 mAb and donor-specific transfusion, and that it takes at least 1 month for these cells to expand and effectively drive the recipient's immune system toward immunologic unresponsiveness.
Zhiliang Wang - One of the best experts on this subject based on the ideXlab platform.
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mammalian target of rapamycin inhibition and alloantigen specific regulatory t cells synergize to promote long term Graft survival in immunocompetent recipients
Journal of Immunology, 2010Co-Authors: Giorgio Raimondi, Zhiliang Wang, Tina L Sumpter, Benjamin M Matta, Mahesh Pillai, Natasha Corbitt, Yoram Vodovotz, Angus W. ThomsonAbstract:Minimization of immunosuppression and donor-specific tolerance to MHC-mismatched organ Grafts are important clinical goals. The therapeutic potential of regulatory T cells (Tregs) has been demonstrated, but conditions for optimizing their in vivo function posttransplant in nonlymphocyte-depleted hosts remain undefined. In this study, we address mechanisms through which inhibition of the mammalian target of rapamycin (Rapa) synergizes with alloantigen-specific Treg (AAsTreg) to permit long-term, donor-specific Heart Graft survival in immunocompetent hosts. Crucially, immature allogeneic dendritic cells allowed AAsTreg selection in vitro, with minimal expansion of unwanted (Th17) cells. The rendered Treg potently inhibited T cell proliferation in an Ag-specific manner. However, these AAsTreg remained unable to control T cells stimulated by allogeneic mature dendritic cells, a phenomenon dependent on the release of proinflammatory cytokines. In vivo, Rapa administration reduced danger-associated IL-6 production, T cell proliferation, and Graft infiltration. Based on these observations, AAsTreg were administered posttransplant (day 7) in combination with a short course of Rapa and rendered >80% long-term (>150 d) Graft survival, a result superior to that achieved with polyclonal Treg. Moreover, Graft protection was alloantigen-specific. Significantly, long-term Graft survival was associated with alloreactive T cell anergy. These findings delineate combination of transient mammalian target of Rapa inhibition with appropriate AAsTreg selection as an effective approach to promote long-term organ Graft survival.
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rapamycin conditioned dendritic cells are poor stimulators of allogeneic cd4 t cells but enrich for antigen specific foxp3 t regulatory cells and promote organ transplant tolerance
Journal of Immunology, 2007Co-Authors: Heth R Turnquist, Angus W. Thomson, Zhiliang Wang, Giorgio Raimondi, Alan F Zahorchak, Ryan T FischerAbstract:The ability of dendritic cells (DC) to regulate Ag-specific immune responses via their influence on T regulatory cells (Treg) may be key to their potential as therapeutic tools or targets for the promotion/restoration of tolerance. In this report, we describe the ability of maturation-resistant, rapamycin (RAPA)-conditioned DC, which are markedly impaired in Foxp3− T cell allostimulatory capacity, to favor the stimulation of murine alloantigen-specific CD4+CD25+Foxp3+ Treg. This was distinct from control DC, especially following CD40 ligation, which potently expanded non-Treg. RAPA-DC-stimulated Treg were superior alloantigen-specific suppressors of T effector responses compared with those stimulated by control DC. Supporting the ability of RAPA to target effector T and B cells, but permit the proliferation and suppressive function of Treg, an infusion of recipient-derived alloantigen-pulsed RAPA-DC followed by a short postoperative course of low-dose RAPA promoted indefinite (>100 day) Heart Graft survival. This was associated with Graft infiltration by CD4+Foxp3+ Treg and the absence of transplant vasculopathy. The adoptive transfer of CD4+ T cells from animals with long-surviving Grafts conferred resistance to rejection. These novel findings demonstrate that, whereas maturation resistance does not impair the capacity of RAPA-DC to modulate Treg, it profoundly impairs their ability to expand T effector cells. A demonstration of this mechanism endorses their potential as tolerance-promoting cellular vaccines.
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rapamycin treated alloantigen pulsed host dendritic cells induce ag specific t cell regulation and prolong Graft survival
American Journal of Transplantation, 2005Co-Authors: Timucin Taner, Holger Hackstein, Zhiliang Wang, Adrian E Morelli, Angus W. ThomsonAbstract:Tolerogenic properties of dendritic cells (DC), particularly those in the immature state, and their therapeutic potential are increasingly being recognized. Among several distinct approaches to generate stably immature DC, pharmacologic manipulation stands out as a promising and clinically applicable option. We have shown recently that the immunophilin ligand rapamycin (Rapa) can inhibit DC maturation and their effector functions. Here, we examined the impact of Rapa exposure on subsequent alloantigen (Ag) presentation by myeloid DC via the indirect pathway. Rapa-treated, allogeneic lysate-pulsed host DC (Rapa-DC) were inferior stimulators of syngeneic T cells, compared to lysate-pulsed control DC. Rapa exposure did not block alloAg uptake by DC nor impair their in vivo homing to splenic T cell areas after adoptive transfer. T cells primed by Rapa-treated, alloAg-pulsed DC showed decreased capacity to produce IL-2 and IFNγ, and were hyporesponsive to subsequent challenge via both the direct and indirect pathways, in an Ag-specific manner. When infused 1 week before transplantation, these Rapa-DC significantly prolonged alloAg-specific Heart Graft survival. This effect was reversed by systemic IL-2 administration but enhanced by either repeated infusion of the cells or a short post-transplant course of FK506. These therapeutic effects, achieved by targeting both major pathways of allorecognition, provide the basis for a clinically applicable strategy to suppress Graft rejection.
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Plasmacytoid dendritic cell precursors induce allogeneic T-cell hyporesponsiveness and prolong Heart Graft survival.
American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons, 2005Co-Authors: Masanori Abe, Zhiliang Wang, An De Creus, Angus W. ThomsonAbstract:Dendritic cell (DC) precursors were propagated from C57BL/10 (B10; H2b) mouse bone marrow in fms-like tyrosine kinase 3 ligand. Cosignaling molecule (B7-1/B7-2 and B7-H1) expression and stimulatory capacity of precursor (pre)-plasmacytoid (p)DC (CD11c+B220+CD11b−CD19−) and classic myeloid DC (MDC) for allogeneic (C3H; H2k) T cells were compared. Unstimulated pre-pDC exhibited very low levels of surface MHC class II and classic costimulatory molecules (B7-1/B7-2), whereas a minor population expressed B7-H1 at levels higher than on MDC. The pre-pDC were ineffective T-cell stimulators and induced nonspecific hyporesponsiveness to rechallenge with donor alloantigens in vitro and in vivo. Following stimulation with CpG-oligonucleotide (CpG-ODN), B7 molecule expression was upregulated on pre-pDC, however the ratio between coinhibitory (B7-H1) and costimulatory (B7-1/B7-2) signals was much higher (five- to six-fold) on pre-pDC than MDC. Blockade of B7-H1 expression on pDC increased their T-cell allostimulatory capacity significantly. A single preoperative infusion of C3H hosts with pre-pDC prolonged B10 Heart Graft survival significantly but nonspecifically compared with untreated mice (median survival times 22 vs. 9 days, respectively). Thus, pre-pDC of donor origin have potential to regulate T-cell responses to alloantigens and can prolong organ Graft survival.
Kimikazu Hamano - One of the best experts on this subject based on the ideXlab platform.
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Spleen plays an important role in maintaining tolerance after removal of the vascularized Heart Graft.
Transplantation, 2007Co-Authors: Eiichi Chosa, Kimikazu Hamano, Kathryn J. Wood, Masaki Hara, Akira Watanabe, Yasunori Matsuzaki, Kunihide Nakamura, Toshio OnitsukaAbstract:Background. This study addresses the question of the mechanism for maintaining tolerance to donor alloantigen in the absence of antigen and the role of secondary lymphoid tissues. Methods. Depleting anti-CD4 antibody administration in conjunction with allogeneic Heart transplantation generates donor-specific operational tolerance. Primary C57BL/6 Heart Grafts were transplanted into the neck cavity of the anti-CD4 antibody pretreated C3H/He mice. At day 50, functioning Heart Grafts were removed from tolerant mice. At day 100, a secondary C57BL/6 or a third-party Heart was transplanted into the abdomen. Results. Anti-CD4 antibody therapy induced CD4 + CD25 + regulatory T cells by 50 days after transplantation, as depleting anti-CD25 treatment in tolerant mice abrogated Graft prolongation when spleen leukocytes were adoptively transferred to syngeneic mice. Tolerance was maintained by CD4 + CD25 + regulatory T cells via a CTLA-4 signal at 100 days, even after removal of the primary Graft at day 50. Administration of anti-CD25 antibody immediately after removal of the primary Graft did not break tolerance, as five out of six second alloGrafts transplanted at day 100 were accepted. Anti-CD25 antibody therapy in conjunction with splenectomy, but not thymectomy, immediately after removal of primary Heart Grafts at day 50 broke tolerance at day 100; all alloGrafts were rejected. Conclusion. The spleen is important in maintaining CD4 + CD25 + regulatory T cells after primary alloGraft removal.
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The Detection of Chronic Heart Graft Rejection by 31 P NMR Spectroscopy
Surgery today, 1999Co-Authors: K Suzuki, Kimikazu Hamano, Hiroshi Ito, Yoshihiko Fujimura, Kensuke EsatoAbstract:The usefulness of phosphorus-31 nuclear magnetic resonance spectroscopy (31P NMRS) from detecting Heart Graft rejection after transplantation has been investigated by several researchers, and it has thus been demonstrated to be a valid technique for detecting acute myocardial rejection. In this study, we investigated the value of31P NMRS to assess chronic cardiac alloGraft rejection. Lewis rat Hearts were transplanted into the femoral region of F-344 rat recipients which were treated with cyclosporine, 5 mg/kg body weight, by a daily intramuscular injection for 30 days beginning on the day of transplantation. The control isoGrafts employed Lewis donors and recipients not given cyclosporine. The ratios of phosphocreatine (PCr) to inorganic phosphate (Pi), β-adenosine trisphosphate (β-ATP) to Pi, and PCr to β-ATP were monitored using surface coil31P NMRS.31P NMRS was performed 3, 30, and 60 days after transplantation, and the degree of the rejection and arteriosclerosis of the coronary arteries were then assessed histologically. The PCr:Pi and β-ATP:Pi ratios for the alloGrafts demonstrated a significant decrease on postoperative day (POD) 60 from that on POD 30 (PCr:Pi,P
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Evidence that the continued presence of the organ Graft and not peripheral donor microchimerism is essential for maintenance of tolerance to alloantigen in vivo in anti-CD4 treated recipients.
Transplantation, 1996Co-Authors: Kimikazu Hamano, Mary-anne Rawsthorne, Andrew Bushell, Peter J. Morris, Kathryn J. WoodAbstract:The source of donor alloantigen required to maintain tolerance in vivo was evaluated in anti-Cd4 monoclonal antibody (mAb) treated mice. Treatment with a depleting anti-Cd4 mAb at the time of transplantation (day -1, 0) induces tolerance to C57BL/10 (H2 b ) vascularized cardiac alloGrafts in C3H.He (H2 k ) mice (1). The presence of the vascularized alloGraft was found to be essential for the induction of tolerance in this experimental model ; it is the only source of donor alloantigen during the induction phase of unresponsiveness (0-50 days). In the maintenance phase (>50 days) donor alloantigen is potentially available from two sources, the organ Graft itself or donor cells that have migrated out of the Graft and are resident in the periphery (donor microchimerism). We show that the vascularized cardiac alloGraft is essential for the maintenance of tolerance to donor alloantigen in vivo. When the primary Heart Graft remained in situ, tolerance to donor alloantigens, as assessed by the survival of a second Heart Graft, was maintained indefinitely (>250 days) (MST of second C57 Heart Grafts >100 days). However, when the primary Heart Graft was removed 50 days after transplantation, a time point when tolerance to donor alloantigens was demonstrable in vivo, tolerance was lost 200 days later (MST of second C57 Heart Grafts 31 days). No evidence of donor microchimerism in the recipient was obtained using allele specific polymerase chain reaction (pcr) analysis for donor class I antigen. Persistence of donor alloantigen in the form of the vascularized organ Graft is therefore required for both the induction and maintenance of tolerance to alloantigen in vivo in this experimental model.
Lori J. West - One of the best experts on this subject based on the ideXlab platform.
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Tolerance Induction in Neonatal Mice: Exhaustion of CD8 T Cells in Allogeneic Bone Marrow Tolerizing Inoculum Fails to Induce GVHD and Leads to Prolonged Donor Heart Graft Survival.
The Journal of Heart and Lung Transplantation, 2020Co-Authors: R.a. Bascom, K. Tao, Lori J. WestAbstract:Purpose Adult allogeneic (allo) spleen cells (SC) induce lethal aGVHD in newborn mice whereas bone marrow cells (BMC) induce non-robust transplant tolerance. To understand these differences we examined CD8 T cells from both inocula before and after injection into neonatal mice, analyzing their molecular phenotypes and trafficking/fates. Methods Neonatal C3H (H-2k) mice were injected iv with either total adult B6 (H-2b) GFP+ SC or BMC, or purified CD8 T cells. Cell trafficking and fates were monitored by whole body/organ imaging. GVHD was defined by reduced growth/viability and tolerance by donor-type Heart transplant survival. Cell phenotypes were examined by flow cytometry. Results Neonates injected with allo-SC developed lethal aGVHD whereas those injected with allo-BMC acquired a non-robust Heart transplant tolerance. Both allo-SC and -BMC trafficked to secondary lymphoid organs, proliferated and then spread throughout the body by day 6, suggesting systemic inflammation. CD8 T cells purified from both inocula also proliferated and spread throughout the mice, indicating direct activation. Despite similar proliferation/ trafficking, purified SC CD8 T cells induced lethal aGVHD in 100% mice (n=4/4) whereas the same number of purified BMC CD8 T cells did so infrequently (n=1/4). To understand these differences flow cytometry was performed on SC and BMC CD8 T cells before and after injection (isolated from liver on day 6). CD8 T cells from BMC inocula expressed high levels of CD28, KLRG1, CTLA-4, PD-1 and CD44 unlike those from SC, indicating SC CD8 T cells to be naive and BMC CD8 T cells to have a memory-like phenotype. At 6 days post-injection, CD8 T cells from both SC and BMC showed higher CTLA-4 and PD-1 expression than pre-injection, implying dampening of their immune responses. KLRG1 expression in BMC CD8 T cells was lower on day 6 than in the starting inoculum, which together with higher CTLA-4 and PD-1 expression suggests they were undergoing exhaustion. At day10, injected BMC CD8 T cells were observed in liver interacting with host CD8 T cells and undergoing fragmentation. Conclusion In tolerizing inocula, BMC CD8 T cells start to undergo exhaustion and are attacked by the neonatal host immune system, mitigating the risk of lethal aGVHD and ultimately prolonging donor-type Heart Graft survival.
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Regulatory T Cells (Tregs) in Neonatal Tolerance: Allogeneic Tregs Regulate the Neonatal Immune System and Prolong Heart Graft Survival
The Journal of Heart and Lung Transplantation, 2013Co-Authors: R.a. Bascom, K. Tao, S.l. Tollenaar, Lori J. WestAbstract:Purpose Semi-allogeneic (F1; H-2k/b) splenocytes (SC) injected into newborn mice (H-2k) induce immunological tolerance whereas allogeneic SC (H-2b) lead to Graft- vs -host disease (GVHD). This study tested injection of purified allogeneic Tregs in our model of neonatal tolerance to cardiac alloGrafts. Methods and Materials CD4 + CD25 + Tregs were isolated using StemCell Technologies EasySep® purification kits. Injected labeled syngeneic, F1 or allogeneic SC, or purified allogeneic Tregs, were tracked in newborn mice for 6 days by OV100 small animal imaging system. Treg interactions and fates were studied by confocal microscopy, and their ability to prolong Heart alloGraft survival in adults. Results By whole body and organ imaging syngeneic and F1 SC tracked to lymphoid organs while allogeneic SC initially tracked there but then proliferated and distributed throughout the mice consistent with GVHD. Injected Tregs also trafficked to lymphoid organs but unlike allogeneic SC did not proliferate. Allogeneic Tregs survived post-injection in spleen suggesting they were not being attacked by the host immune system. In neonatal spleen, allogeneic Tregs interacted with host Tregs either directly or via host dendritic cells indicating a possible role in iTreg formation. Injected allogeneic Tregs prolonged survival of both donor-type and third-party Heart Grafts to 100 days in 50% of transplanted mice (n=6). A >100 day functioning donor-type Heart Graft showed mild-moderate cellular infiltrate of macrophages and T cells including CD8+ T cells, with focal regions of myocyte damage. Conclusions Injection of neonates with purified allogeneic Tregs prolongs survival of donor-type and third party Heart Grafts transplanted as adults. Prolonged third-party Graft survival suggests suppression of the host immune system in a localized “non-specific” manner; alternatively given the presumed clonal diversity of allogeneic Tregs, some form of specific/cross-reactive suppression may be occurring.
