Peripheral Blood T Cells Generated After Allogeneic Bone Marrow Transplantation: Lower Levels of Bcl-2 Protein and Enhanced Sensitivity to Spontaneous and CD95-Mediated Apoptosis In Vitro. Abrogation of the Apoptotic Phenotype Coincides With the Recovery of Normal Naive/Primed T-Cell Profiles

Blood ◽  
1999 ◽  
Vol 94 (5) ◽  
pp. 1803-1813 ◽  
Author(s):  
Nadia Chafika Hebib ◽  
Olivier Déas ◽  
Matthieu Rouleau ◽  
Antoine Durrbach ◽  
Bernard Charpentier ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Cell Death ◽  
T Cell ◽  
Peripheral Blood ◽  
Ex Vivo ◽  
Allogeneic Bone Marrow Transplantation ◽  
Allogeneic Bone ◽  
Bax Protein

Abstract T-cell reconstitution after bone marrow transplant (BMT) is characterized, for at least 1 year, by the expansion of populations of T cells with a primed/memory phenotype and by reverse CD4/CD8 proportions. T lymphocytes from 26 BMT patients (mostly adults) were obtained at various times after transplantation (from 45 to ≥730 days) and were tested for susceptibility to spontaneous apoptosis and anti-Fas triggered apoptosis in vitro. Substantial proportions of CD4+ and CD8+ cells generated during the first year after transplantation, but not by day 730, exhibited in these assays decreased mitochondrial membrane potential (▵Ψm) and apoptotic DNA fragmentation. The apoptotic phenotype tended to disappear late in the follow-up period, when substantial absolute numbers of naive (CD45RA+/CD62-L+) T cells had repopulated the peripheral blood compartment of the BMT patients. The rate of spontaneous cell death in vitro was significantly correlated with lower levels of ex vivo Bcl-2 protein, as assessed by cytofluorometry and Western blot analysis. In contrast, the levels of Bax protein remained unchanged, resulting in dysregulated Bcl-2/Bax ratios. Cell death primarily concerned the expanded CD8+/CD45R0+ subpopulation, although CD45R0− subpopulations were also involved, albeit to a lesser extent. These results show that the T-cell regeneration/expansion occurring after BMT is accompanied by decreased levels of Bcl-2 and susceptibility to apoptosis.

Peripheral Blood T Cells Generated After Allogeneic Bone Marrow Transplantation: Lower Levels of Bcl-2 Protein and Enhanced Sensitivity to Spontaneous and CD95-Mediated Apoptosis In Vitro. Abrogation of the Apoptotic Phenotype Coincides With the Recovery of Normal Naive/Primed T-Cell Profiles

Blood ◽  
1999 ◽  
Vol 94 (5) ◽  
pp. 1803-1813 ◽  
Author(s):  
Nadia Chafika Hebib ◽  
Olivier Déas ◽  
Matthieu Rouleau ◽  
Antoine Durrbach ◽  
Bernard Charpentier ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Cell Death ◽  
T Cell ◽  
Peripheral Blood ◽  
Ex Vivo ◽  
Allogeneic Bone Marrow Transplantation ◽  
Allogeneic Bone ◽  
Bax Protein

T-cell reconstitution after bone marrow transplant (BMT) is characterized, for at least 1 year, by the expansion of populations of T cells with a primed/memory phenotype and by reverse CD4/CD8 proportions. T lymphocytes from 26 BMT patients (mostly adults) were obtained at various times after transplantation (from 45 to ≥730 days) and were tested for susceptibility to spontaneous apoptosis and anti-Fas triggered apoptosis in vitro. Substantial proportions of CD4+ and CD8+ cells generated during the first year after transplantation, but not by day 730, exhibited in these assays decreased mitochondrial membrane potential (▵Ψm) and apoptotic DNA fragmentation. The apoptotic phenotype tended to disappear late in the follow-up period, when substantial absolute numbers of naive (CD45RA+/CD62-L+) T cells had repopulated the peripheral blood compartment of the BMT patients. The rate of spontaneous cell death in vitro was significantly correlated with lower levels of ex vivo Bcl-2 protein, as assessed by cytofluorometry and Western blot analysis. In contrast, the levels of Bax protein remained unchanged, resulting in dysregulated Bcl-2/Bax ratios. Cell death primarily concerned the expanded CD8+/CD45R0+ subpopulation, although CD45R0− subpopulations were also involved, albeit to a lesser extent. These results show that the T-cell regeneration/expansion occurring after BMT is accompanied by decreased levels of Bcl-2 and susceptibility to apoptosis.

scholarly journals Imbalances within the peripheral blood T-helper (CD4+) and T-suppressor (CD8+) cell populations in the reconstitution phase after human bone marrow transplantation

Blood ◽  
1988 ◽  
Vol 71 (5) ◽  
pp. 1196-1200 ◽  
Author(s):  
A Velardi ◽  
A Terenzi ◽  
S Cucciaioni ◽  
R Millo ◽  
CE Grossi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Bone Marrow Transplantation ◽  
T Cell ◽  
Peripheral Blood ◽  
Marrow Transplantation ◽  
Allogeneic Bone Marrow Transplantation ◽  
T Cell Subsets ◽  
Allogeneic Bone ◽  
T Helper

Abstract Peripheral blood T cell subsets were evaluated in 11 patients during the reconstitution phase after allogeneic bone marrow transplantation and compared with 11 age-matched controls. The proportion of cells coexpressing Leu7 and CD11b (C3bi receptor) markers was determined within the CD4+ (T-helper) and the CD8+ (T-suppressor) subsets by two- color immunofluorescence analysis. CD4+ and CD8+ T cells reached normal or near-normal values within the first year posttransplant. In contrast to normal controls, however, most of the cells in both subsets coexpressed the Leu7 and CD11b markers. T cells with such phenotype display the morphological features of granular lymphocytes (GLs) and a functional inability to produce interleukin 2 (IL 2). These T cell imbalances were not related to graft v host disease (GvHD) or to clinically detectable virus infections and may account for some defects of cellular and humoral immunity that occur after bone marrow transplantation./

scholarly journals Imbalances within the peripheral blood T-helper (CD4+) and T-suppressor (CD8+) cell populations in the reconstitution phase after human bone marrow transplantation

Blood ◽  
1988 ◽  
Vol 71 (5) ◽  
pp. 1196-1200 ◽  
Author(s):  
A Velardi ◽  
A Terenzi ◽  
S Cucciaioni ◽  
R Millo ◽  
CE Grossi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Bone Marrow Transplantation ◽  
T Cell ◽  
Peripheral Blood ◽  
Marrow Transplantation ◽  
Allogeneic Bone Marrow Transplantation ◽  
T Cell Subsets ◽  
Allogeneic Bone ◽  
T Helper

Peripheral blood T cell subsets were evaluated in 11 patients during the reconstitution phase after allogeneic bone marrow transplantation and compared with 11 age-matched controls. The proportion of cells coexpressing Leu7 and CD11b (C3bi receptor) markers was determined within the CD4+ (T-helper) and the CD8+ (T-suppressor) subsets by two- color immunofluorescence analysis. CD4+ and CD8+ T cells reached normal or near-normal values within the first year posttransplant. In contrast to normal controls, however, most of the cells in both subsets coexpressed the Leu7 and CD11b markers. T cells with such phenotype display the morphological features of granular lymphocytes (GLs) and a functional inability to produce interleukin 2 (IL 2). These T cell imbalances were not related to graft v host disease (GvHD) or to clinically detectable virus infections and may account for some defects of cellular and humoral immunity that occur after bone marrow transplantation./

scholarly journals In vitro evidence for disappearance of erythroid progenitor T suppressor cells following allogeneic bone marrow transplantation for severe aplastic anemia

Blood ◽  
1988 ◽  
Vol 71 (1) ◽  
pp. 144-150 ◽  
Author(s):  
KF Mangan ◽  
MT Mullaney ◽  
CS Rosenfeld ◽  
RK Shadduck
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Bone Marrow Transplantation ◽  
T Cell ◽  
T Lymphocytes ◽  
Marrow Transplantation ◽  
Allogeneic Bone Marrow Transplantation ◽  
Allogeneic Bone ◽  
Before And After

Abstract In vitro coculture studies were performed in five patients with severe aplastic anemia (SAA) and their normal HLA-matched donors before and after allogeneic bone marrow transplantation (BMT) to determine whether the erythropoietic function of T cells is abnormal in this disorder. These coculture studies used fresh or cryopreserved marrow T lymphocytes with fresh or cryopreserved marrow T cell-depleted target cells. Four of five aplastic patients had little or no transfusion exposure before studies. The composite results showed that, in comparison to the erythropoietic effects of normal HLA-identical marrow T lymphocytes or engrafted T lymphocytes, T lymphocytes collected from the aplastic patients before BMT consistently suppressed or failed to support CFUE and BFUE growth optimally from autologous marrow, HLA- identical marrow, or engrafted aplastic T cell-depleted marrows. This T cell abnormality was not observed in four multiply transfused leukemics and three patients with myelodysplastic syndrome. Marker analyses of SAA marrow T lymphocytes performed before and after BMT suggested that the erythropoietic functional abnormality was due to abnormal marrow T cell composition reflecting an excess of activated Tac+, T3+, T11+ lymphocytes. Collectively, these in vitro studies provide firmer in vitro evidence implicating T cells in the pathogenesis of SAA. The erythropoietic T cells abnormalities in SAA are fully corrected by allogeneic BMT.

scholarly journals In vitro evidence for disappearance of erythroid progenitor T suppressor cells following allogeneic bone marrow transplantation for severe aplastic anemia

Blood ◽  
1988 ◽  
Vol 71 (1) ◽  
pp. 144-150
Author(s):  
KF Mangan ◽  
MT Mullaney ◽  
CS Rosenfeld ◽  
RK Shadduck
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Bone Marrow Transplantation ◽  
T Cell ◽  
T Lymphocytes ◽  
Marrow Transplantation ◽  
Allogeneic Bone Marrow Transplantation ◽  
Allogeneic Bone ◽  
Before And After

In vitro coculture studies were performed in five patients with severe aplastic anemia (SAA) and their normal HLA-matched donors before and after allogeneic bone marrow transplantation (BMT) to determine whether the erythropoietic function of T cells is abnormal in this disorder. These coculture studies used fresh or cryopreserved marrow T lymphocytes with fresh or cryopreserved marrow T cell-depleted target cells. Four of five aplastic patients had little or no transfusion exposure before studies. The composite results showed that, in comparison to the erythropoietic effects of normal HLA-identical marrow T lymphocytes or engrafted T lymphocytes, T lymphocytes collected from the aplastic patients before BMT consistently suppressed or failed to support CFUE and BFUE growth optimally from autologous marrow, HLA- identical marrow, or engrafted aplastic T cell-depleted marrows. This T cell abnormality was not observed in four multiply transfused leukemics and three patients with myelodysplastic syndrome. Marker analyses of SAA marrow T lymphocytes performed before and after BMT suggested that the erythropoietic functional abnormality was due to abnormal marrow T cell composition reflecting an excess of activated Tac+, T3+, T11+ lymphocytes. Collectively, these in vitro studies provide firmer in vitro evidence implicating T cells in the pathogenesis of SAA. The erythropoietic T cells abnormalities in SAA are fully corrected by allogeneic BMT.

scholarly journals Keratinocyte growth factor enhances DNA plasmid tumor vaccine responses after murine allogeneic bone marrow transplantation

Blood ◽  
2009 ◽  
Vol 113 (7) ◽  
pp. 1574-1580 ◽  
Author(s):  
Robert R. Jenq ◽  
Christopher G. King ◽  
Christine Volk ◽  
David Suh ◽  
Odette M. Smith ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Keratinocyte Growth Factor ◽  
Allogeneic Bone Marrow Transplantation ◽  
Allogeneic Bone ◽  
Effector Cells ◽  
Cd8 Cells ◽  
T Cell Reconstitution ◽  
Dna Plasmid

Abstract Keratinocyte growth factor (KGF), which is given exogenously to allogeneic bone marrow transplantation (allo-BMT) recipients, supports thymic epithelial cells and increases thymic output of naive T cells. Here, we demonstrate that this improved T-cell reconstitution leads to enhanced responses to DNA plasmid tumor vaccination. Tumor-bearing mice treated with KGF and DNA vaccination have improved long-term survival and decreased tumor burden after allo-BMT. When assayed before vaccination, KGF-treated allo-BMT recipients have increased numbers of peripheral T cells, including CD8+ T cells with vaccine-recognition potential. In response to vaccination, KGF-treated allo-BMT recipients, compared with control subjects, generate increased numbers of tumor-specific CD8+ cells, as well as increased numbers of CD8+ cells producing interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α). We also found unanticipated benefits to antitumor immunity with the administration of KGF. KGF-treated allo-BMT recipients have an improved ratio of T effector cells to regulatory T cells, a larger fraction of effector cells that display a central memory phenotype, and effector cells that are derived from a broader T-cell–receptor repertoire. In conclusion, our data suggest that KGF can function as a potent vaccine adjuvant after allo-BMT through its effects on posttransplantation T-cell reconstitution.

scholarly journals Different T-cell receptor repertoires between lesions and peripheral blood in acute graft-versus-host disease after allogeneic bone marrow transplantation

Blood ◽  
1996 ◽  
Vol 87 (7) ◽  
pp. 3019-3026 ◽  
Author(s):  
K Kubo ◽  
K Yamanaka ◽  
H Kiyoi ◽  
H Fukutani ◽  
M Ito ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Bone Marrow Transplantation ◽  
T Cell ◽  
T Cell Receptor ◽  
Allogeneic Bone Marrow Transplantation ◽  
Cell Receptor ◽  
Allogeneic Bone ◽  
Graft Versus Host ◽  
Acute Graft

From the viewpoint of T-cell receptor (TCR) repertoire, we studied the role of T cells in acute graft-versus-host disease (GVHD) after allogeneic bone marrow transplantation (allo-BMT) from an HLA-identical sibling. By means of inverse polymerase chain reaction method and DNA sequencing, we analyzed TCR-alpha and -beta transcripts from GVHD lesions and peripheral blood (PB) in a patient with typical GVHD together with PB from donor. At the initial onset of GVHD, V alpha-7 and -19 subfamilies were oligoclonally expanded in the PB compared with those in the oral mucosal lesions. At the second onset, V alpha-2, and V beta-6 subfamilies were more frequently detected in the cutaneous lesion than in the PB. Some TCR transcripts were recurrently found either in the mucosal or cutaneous lesions (or in both) and not in the PB. Furthermore, some of recurrent TCR transcripts in the lesions shared V gene segments and common motifs of complementarity determining region-3. These findings suggested that T cells infiltrating the GVHD lesions recognized a limited kind of antigens presented by patient's tissues with GVHD, and that T-cell repertoire in the GVHD lesions was different from that in the PB.

Donor CD4+CD25+ T Cells Require Syngeneic MHC Class II for Initial Support of MHC-Mismatched Hematopoietic Engraftment.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 251-251 ◽  
Author(s):  
Alan Hanash ◽  
Robert B. Levy
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Mhc Class Ii ◽  
Allogeneic Bone Marrow Transplantation ◽  
Class Ii ◽  
Allogeneic Bone ◽  
Inherited Disorders ◽  
Donor Chimerism

Abstract Despite the potential to cure both acquired and inherited disorders involving the hematopoietic compartment, application of allogeneic bone marrow transplantation (BMT) is limited by the frequent and severe outcome of Graft vs. Host Disease (GVHD). Unfortunately, efforts to reduce GVHD by purging the donor graft of T cells have resulted in poor engraftment and elevated disease recurrence. Alternative cell populations capable of supporting allogeneic engraftment without inducing GVHD could increase the potential for donor-recipient matching and decrease treatment associated risks. We have observed that GVHD-suppressive donor CD4+CD25+ T cells are capable of supporting allogeneic hematopoietic engraftment, as demonstrated by initial donor progenitor activity and long-term chimerism and tolerance. Using a murine MHC mismatched model transplanting 0.5–2x106 GFP+ C57BL/6 (B6) T cell-depleted bone marrow cells into 7.0 Gy sublethally irradiated BALB/c recipients, splenic CFU assessment demonstrated that co-transplantation of 1x106 B6 CD4+CD25+ T cells lead to increased donor lineage-committed GM (p<.01) and multi-potential HPP (p<.05) progenitors seven days post-BMT compared to transplantation of BM alone. Furthermore, co-transplantation of CD4+CD25+ T cells lead to lymphoid and myeloid chimerism in peripheral blood (lineage specific mean donor chimerism ± SE: B220, 67.7±15.2 vs. 0.3±0.3; CD4, 38.3±10.5 vs.0.9±0.9; CD8, 48.3±11.0 vs. 1.0±1.0; Mac-1, 58.8±16.5 vs. 0.3±0.3) and the presence of donor GM and HPP progenitors in recipient marrow two months post-BMT (mean CFU chimerism ± SE: CFU-GM, 54.5±12.8 vs. 0.0; CFU-HPP, 63.0±17.8 vs.0.0). Donor chimerism persisted six months post-BMT and was associated with tolerance to donor and host antigens by acceptance of donor and host skin grafts >50 days post-homotopic grafting. Characterization of the initial invents of engraftment support demonstrated that augmentation of donor progenitors did not require CD4+CD25+ T cell IL-10, as co-transplantation of B6-wt and B6-IL-10−/− CD4+CD25+ T cells both significantly increased total CFU-GM (mean CFU±SE: BM alone, 657.5±248.2; BM + wt, 1972±331.5; BM + IL-10−/−, 1965±401.7; both p<.05 vs. BM alone). Assessment of the antigenic requirements for activation of progenitor support demonstrated that donor CD4+CD25+ T cells did not require alloreactivity to support progenitors, as BALB/c x B6 F1 CD4+CD25+ T cells significantly increased B6 CFU-GM in BALB/c recipients (p<.001 vs. BM alone). However, B6 CD4+CD25+ T cells failed to augment C3H/HeJ CFU-GM in BALB/c recipients (p>.05 vs. BM alone), suggesting that donor CD4+CD25+ T cells might require recognition of syngeneic MHC for progenitor support. Indeed, augmentation of donor CFU-GM was abrogated when B6 CD4+CD25+ T cells were co-transplanted with B6-MHC class II−/− marrow into BALB/c recipients (p>.05 vs. BM alone). In conclusion, donor CD4+CD25+ T cells capable of promoting long-term engraftment and tolerance do not require IL-10 for support of initial donor progenitor activity, however progenitor support does require co-transplantation with syngeneic MHC class II expressing marrow. Donor CD4+CD25+ T cells may thus represent a useful alternative to unfractionated T cells for promotion of engraftment following allogeneic hematopoietic transplantation.

Deletion Of Fanca Or Fancd2 Dysregulates Treg Activity and Exacerbates Gvhd In Mice

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3239-3239
Author(s):  
Wei Du ◽  
Ozlem Erden ◽  
Andrew Wilson ◽  
Jared Sipple ◽  
Jonathan Schick ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
Transcriptional Activity ◽  
Conflicts Of Interest ◽  
Bone Marrow Failure ◽  
Genetic Disorder ◽  
Allogeneic Bone Marrow Transplantation ◽  
Allogeneic Bone ◽  
In Vitro Proliferation

Abstract Fanconi anemia (FA) is a genetic disorder associated with bone marrow failure and leukemia. Recent studies demonstrate fundamental immune defects in FA. However, the mechanisms that are critical for FA immunodeficiency are not known. Here we report that deletion of Fanca or Fancd2 dysregulates the suppressive activity of regulatory T cells (Tregs) and exacerbates graft-versus-host disease (GVHD) in mice. Recipient mice of Fanca-/- or Fancd2-/- bone marrow chimeras exhibited severe acute GVHD after allogeneic bone marrow transplantation (BMT). Further study showed that T cells from Fanca-/- or Fancd2-/- mice induced higher GVHD lethality than those from WT littermates. Mechanistically, FA Tregs possessed lower proliferative suppression potential compared to WT Tregs, as demonstrated by in vitro proliferation assay and BMT. Analysis of CD25+Foxp3+ Tregs indicated that loss of Fanca or Fancd2 dysregulated Foxp3 transcriptional activity. Additionally, CD25+Foxp3+ Tregs of Fanca-/- or Fancd2-/- mice were less efficient in suppressing the production of GVHD-associated inflammatory cytokines. Consistently, incremental NF-kB transcriptional activity was observed in infiltrated T cells from FA GVHD mice. Conditional deletion of p65 in FA Tregs desreased GVHD mortality. Our study uncovers an essential role for the FA proteins in maintaining Treg homeostasis and suggests that targeted blocking NF-kB signaling within T cells represents an attractive therapeutic strategy to ameliorate GVHD in FA. Disclosures: No relevant conflicts of interest to declare.

Recipient CD8+ DC Delete Alloreactive Donor CTL and Promote Leukemic Relapse after Allogeneic BMT

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 4279-4279
Author(s):  
Kate A Markey ◽  
Rachel D Kuns ◽  
Renee J Robb ◽  
Motoko Koyama ◽  
Kate Helen Gartlan ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Antigen Presentation ◽  
Median Survival ◽  
Conflicts Of Interest ◽  
Critical Role ◽  
Allogeneic Bone Marrow Transplantation ◽  
Allogeneic Bone ◽  
Leukemic Relapse

Abstract Allogeneic bone marrow transplantation (BMT) remains the therapy of choice for many haematological malignancies, but despite the curative benefit of the immunological graft-versus-leukemia (GVL) effect, relapse remains a key cause of death. We have investigated the role of recipient dendritic cells (DC) in antigen presentation to donor CD8 cytotoxic T cells (CTL) in a model of BMT where GVHD and GVL are directed to multiple minor histocompatibility antigens (mHA) and survival reflects GVL activity. C3H.Sw bone marrow and purified CD8 T cell grafts were transplanted with B6-derived MLL-AF9 induced primary acute myeloid leukemia (AML) into lethally irradiated B6.CD11c.DOG recipients (diphtheria toxin receptor (DTR), ovalbumin and GFP expression driven off the CD11c promoter) such that recipient DC can be deleted by DT administration. Surprisingly, depletion of recipient DC resulted in improved leukemic control (median survival 43 vs 31 days, P <0.001). The use of IRF8-/- BMT recipients (in which the CD8+ DC subset is absent) confirmed that recipient CD8+ DC were critical for regulating these GVL effects (median survival 43 vs 34 days, P = 0.0005). Conversely, when recipient CD8+ DC were expanded in a B6 to B6D2F1 model with bcr-abl/Nup98-HoxA9 induced primary AML, by using Flt3-L treatment for 10 days prior to BMT, GVL effects were completely eliminated, rendering relapse rate equivalent to that seen in the recipients of T cell depleted (TCD) grafts (median survival 11 days in BM+T and TCD groups where recipients were pre-treated with Flt3-L, vs. >45 days in the saline treated BM+T group). The use of B6.CD11c-Rac1 transgenic BMT recipients (who cannot process and present exogenously acquired antigen) confirmed that this effect was the result of endogenous alloantigen presentation by recipient DC and independent of cross-presentation.Using the same depletion strategies in an antigen-specific model (with donor OT-I T cells and B6.CD11c.DOG x DBA/2 F1 recipients) we confirmed that recipient DC invoked effector donor CTL activation, differentiation (CD25+ CD69+ CD62L-) and subsequent apoptosis (as measured by Annexin V; 52.4% vs. 23.9% in DC replete vs. depleted recipients, P = 0.01). There was a consequent profound contraction of the donor CTL compartment by day 10 in DC replete recipients. This contraction of the CTL compartment was associated with reduced expression of the cytolytic molecule granzyme B (MFI 1922 vs 1097, P = 0.02). Antigen presentation has a critical role in the initiation of donor T cell alloreactivity and GVL after BMT. Here we demonstrate that endogenous alloantigen presentation by recipient CD8+ DC to donor T cells leads to activation induced death of donor CTL early after BMT, which in turn facilitates leukemic relapse. This concept has critical implications for the design of therapies that target DC in the peri-transplant period and confirms that recipient DC regulate GVL effects. Disclosures No relevant conflicts of interest to declare.

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