Protection from graft-versus-host disease by HIV-1 envelope protein gp120-mediated activation of human CD4+CD25+ regulatory T cells

AbstractNaturally occurring CD4+CD25+ regulatory T cells (Tregs) represent a unique T-cell lineage that is endowed with the ability to actively suppress immune responses. Therefore, approaches to modulate Treg function in vivo could provide ways to enhance or reduce immune responses and lead to novel therapies. Here we show that the CD4 binding human immunodeficiency virus-1 envelope glycoprotein gp120 is a useful and potent tool for functional activation of human Tregs in vitro and in vivo. Gp120 activates human Tregs by binding and signaling through CD4. Upon stimulation with gp120, human Tregs accumulate cyclic adenosine monophosphate (cAMP) in their cytosol. Inhibition of endogeneous cAMP synthesis prevents gp120-mediated Treg activation. Employing a xenogeneic graft versus host disease model that has been shown to be applicable for the functional analysis of human Tregs in vivo, we further show that a single dose of gp120 is sufficient to prevent lethal graft versus host disease and that the tolerizing effect of gp120 is strictly dependent on the presence of human Tregs and their up-regulation of cAMP upon gp120-mediated activation. Our findings demonstrate that stimulation via the CD4 receptor represents a T-cell receptor–independent Treg activating pathway with potential to induce immunologic tolerance in vivo.

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Characterization of in vitro antimurine thymocyte globulin–induced regulatory T cells that inhibit graft-versus-host disease in vivo

Blood ◽

10.1182/blood-2007-08-106526 ◽

2008 ◽

Vol 111 (3) ◽

pp. 1726-1734 ◽

Cited By ~ 36

Author(s):

Melanie C. Ruzek ◽

James S. Waire ◽

Deborah Hopkins ◽

Gina LaCorcia ◽

Jennifer Sullivan ◽

...

Keyword(s):

T Cells ◽

Regulatory T Cells ◽

Graft Versus Host Disease ◽

Antithymocyte Globulin ◽

Mrna Level ◽

Regulatory Cells ◽

Host Disease ◽

Graft Versus Host

Abstract Antithymocyte/antilymphocyte globulins are polyclonal antihuman T-cell antibodies used clinically to treat acute transplant rejection. These reagents deplete T cells, but a rabbit antihuman thymocyte globulin has also been shown to induce regulatory T cells in vitro. To examine whether antithymocyte globulin–induced regulatory cells might be functional in vivo, we generated a corresponding rabbit antimurine thymocyte globulin (mATG) and tested its ability to induce regulatory cells in vitro and whether those cells can inhibit acute graft-versus-host disease (GVHD) in vivo upon adoptive transfer. In vitro, mATG induces a population of CD4+CD25+ T cells that express several cell surface molecules representative of regulatory T cells. These cells do not express Foxp3 at either the protein or mRNA level, but do show suppressive function both in vitro and in vivo when adoptively transferred into a model of GVHD. These results demonstrate that in a murine system, antithymocyte globulin induces cells with suppressive activity that also function in vivo to protect against acute GVHD. Thus, in both murine and human systems, antithymocyte globulins not only deplete T cells, but also appear to generate regulatory cells. The in vitro generation of regulatory cells by anti-thymocyte globulins could provide ad-ditional therapeutic modalities for immune-mediated disease.

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Host γd T cells Exacerbate Experimental Acute Graft-Versus-Host Disease through Activation of Host Antigen Presenting Cells.

Blood ◽

10.1182/blood.v104.11.3045.3045 ◽

2004 ◽

Vol 104 (11) ◽

pp. 3045-3045

Author(s):

Yoshinobu Maeda ◽

Pavan Reddy ◽

Chen Liu ◽

D. Keith Bishop ◽

James L.M. Ferrara

Keyword(s):

T Cells ◽

T Cell ◽

Mhc Class Ii ◽

Graft Versus Host Disease ◽

Serum Levels ◽

Host Disease ◽

Graft Versus Host ◽

Full Intensity

Abstract Large numbers of T cells bearing γd T cell receptors are present in graft-versus-host disease (GVHD) target tissues. We investigated the potential role of host γd T cells during acute GVHD in a well-characterized GVHD model following full intensity conditioning (11 Gy TBI). BM and spleen T cells from BALB/c (H2d) donors were transplanted into wild type (wt) B6, aß T cell deficient B6 (aß −/−) or γd T cell deficient B6 (γd −/−) hosts. γd −/− hosts demonstrated significantly better day 35 survival (85%) than wt (40%) or aß−/− hosts (18%) (P<0.05). Reconstitution of γd −/− B6 hosts with B6 type γd T cells 24 hr prior to BMT restored lethal GVHD (50 % day 35 survival). In vivo, γd −/− B6 hosts demonstrated at least a five fold reduction in donor T cell expansion and cytokine production. In vitro, T cells proliferated less when co-cultured with allogeneic γd −/− dendritic cells (DCs) than with wt DCs (40,127 ± 1634 vs. 72,503 ± 1296, P<0.05). BM-derived DCs cultured with γd T cells caused greater proliferation of allogeneic T cells than DCs cultured with aß T cells (15.1 ± 21 x 104 vs. 5.1 ± 1.2 x 104, P<0.05). We next tested the effect of γd T cells on host DCs in vivo using a model system in which only the DCs injected prior to BMT expressed the alloantigen that stimulated the GVHD reaction. MHC Class II −/− B6 mice that had been depleted of γd T cells were given 11 Gy TBI and injected one day prior to BMT with B6 DCs that had been co-cultured either with γd T cells or with medium. On day 0 both groups of recipient mice were injected with BM plus splenic T cells from allogeneic bm12 donors. On day +5, CD4+ donor T cells expanded four times more in recipients of DCs co-cultured with γd T cells than in recipients of control DCs and serum levels of TNF-a were significantly higher (36.7 + 6.8 vs. 21.3 + 3.7 pg/ml, P<0.05). Together these data demonstrate that γd T cells amplify the stimulatory function of host DCs and increase the severity of GVHD, suggesting that a new therapeutic target for the prevention of the major BMT toxicity.

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Donor Dual TCR T Cells Preferentially Expand and Mediate Pathologic Alloreactivity in Acute Graft Versus Host Disease

Blood ◽

10.1182/blood.v118.21.1972.1972 ◽

2011 ◽

Vol 118 (21) ◽

pp. 1972-1972

Author(s):

Gerald P. Morris ◽

Geoffrey L Uy ◽

David L Donermeyer ◽

Paul M Allen ◽

John F. DiPersio

Keyword(s):

T Cells ◽

T Cell ◽

Graft Versus Host Disease ◽

Peripheral Blood ◽

Thymic Selection ◽

Cell Repertoire ◽

Host Disease ◽

Graft Versus Host

Abstract Abstract 1972 The nature of the T cell repertoire mediating pathologic in vivo alloreactivity is an important question for understanding the development of acute graft-versus-host disease (aGvHD) following clinical allogeneic transplantation. We have previously demonstrated that the small proportion of T cells that naturally express 2 T cell receptors (TCR) as a consequence of incomplete TCRa allelic exclusion during thymic development contribute disproportionately to the alloreactive T cell repertoire, both in vitro and in vivo in a mouse model of graft versus host disease (GvHD) (J. Immunol., 182:6639, 2009). Here, we extend these findings to human biology, examining dual TCR T cells from healthy volunteer donors (n = 12) and patients who have undergone allogeneic hematopoietic stem cell transplantation (HSCT) (n = 19). Peripheral blood was collected at day 30 post-HSCT or at the time of presentation with symptomatic acute GvHD. Dual TCR T cells were measured in peripheral blood by pair-wise staining with 3 commercially-available and 2 novel TCRa mAbs. Dual TCR T cells were consistently and significantly expanded in patients with symptomatic aGvHD, representing 5.3±3.8 % of peripheral T cells, compared to 1.7±0.8 % of T cells in healthy controls (p < 0.005) (Figure 1). There was no correlation between dual TCR T cell frequency and GvHD severity. Furthermore, sequential analysis of peripheral blood in 2 patients demonstrated expansion of dual TCR T cells concurrent with the development of aGvHD (Figure 2). Dual TCR T cells from patients with symptomatic aGvHD demonstrated increased expression of CD69 as compared to T cells expressing a single TCR, indicative of preferential activation of dual TCR T cells during aGvHD. Similarly, dual TCR T cells isolated from patients with symptomatic aGvHD demonstrate increased production of IFN-g ex vivo, indicative of the ability to mediate pathogenic alloreactive responses. Dual TCR T cell clones isolated from healthy donors and patients post-HSCT by single cell FACS sorting demonstrate alloreactive responses against a range of allogeneic cell lines in vitro. We propose that the increased alloreactivity of dual TCR T cells results from the less stringent thymic selection for secondary TCR, and thus provides a link between thymic selection, the TCR repertoire, and alloreactivity. These findings may lead to simple ways of phenotypically identifying specific T cells predisposed to inducing aGvHD for subsequent examination of T cell repertoires and functional studies. Furthermore, these data suggest that dual TCR T cells represent a potential predictive biomarker for aGvHD and a potential target for selective T cell depletion in HSCT. Disclosures: No relevant conflicts of interest to declare.

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Inhibition of Graft-Versus-Host Disease (GVHD) by Histone Deacetylase Inhibitor (HDAC) SAHA Leads to Downregulation of STAT1 Activation.

Blood ◽

10.1182/blood.v106.11.1311.1311 ◽

2005 ◽

Vol 106 (11) ◽

pp. 1311-1311

Author(s):

Corinna Leng ◽

Cuiling Li ◽

Judy Ziegler ◽

Anna Lokshin ◽

Suzanne Lentzsch ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Histone Deacetylase ◽

Graft Versus Host Disease ◽

Host Disease ◽

Graft Versus Host ◽

Tnf Α ◽

Ifn Γ

Abstract Histone deacetylase (HDAC) inhibitors have been shown to reduce development of graft versus host disease [GVHD] following allogeneic bone marrow transplantation [BMT]. Administration of the HDAC inhibitor suberonylanilide hydroxamic acid [SAHA] resulted in a significantly reduced GVHD-dependent mortality following fully MHC-mismatched allogeneic BMT. Median Survival Time (MST) for vehicle and SAHA-treated mice were 7.5 days and 38 days respectively. However, SAHA treatment did not affect T cell activation nor T cell expansion in vitro and in vivo as determined by MLR assays, phenotypic analysis of donor T cells with regard to expression of the CD25 activation antigen and calculation of donor CD4+ and CD8+ T cell numbers on days +3 and +6 post-BMT. Thus, SAHA treatment was not able to inhibit the strong upregulation of CD25 antigen on CD8+ T cells observed during induction of GVHD on days +3 and +6 post-BMT. We therefore focused on the effects of SAHA treatment on efferent immune effects including cytokine secretion and intracellular signaling events in vitro and in vivo following GVHD induction. SAHA treatment broadly inhibited lipopolysaccharide [LPS] and allo-antigen-induced cytokine/chemokine secretion in vitro like MIP-1-α, IP-10, IFN-γ, TNF-α and IL-6 and led also to a significant decrease in IFN-γ and TNF-α levels in vivo following induction of GVHD. Concomitantly, SAHA treatment inhibited phosphorylation of STAT1 and STAT3 in response to LPS and allo-activation in vitro. Furthermore, analysis of liver tissue and spleens from SAHA-treated animals with GVHD showed a significant decrease in phosphorylated STAT1. In contrast SAHA treatment had only moderate effects on p38 or ERK1,2 Mitogen-activated Protein Kinase (MAPK) pathway underscoring the relevance of the inhibition of the STAT1 pathway. In conclusion, GVHD is associated with a strong induction of phosphorylation of STAT1 in the liver and spleen and SAHA-dependent reduction of GVHD is associated with systemic and local inhibition of pSTAT1 and modulation of the inflammatory cytokine milieu during the efferent immune response.

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Microrna-191 Regulates T-Cell Clonal Expansion during Graft-Versus-Host Disease

Blood ◽

10.1182/blood-2019-130179 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 4433-4433

Author(s):

Chuanfeng Xiong ◽

Wei Huang ◽

Xiaoli Nie ◽

Ying Huang ◽

Yiqun Jiao ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Graft Versus Host Disease ◽

Clonal Expansion ◽

Host Disease ◽

Graft Versus Host ◽

Alloreactive T Cells

Allogeneic hematopoietic cell transplantation is a potentially curative treatment choice for a wide variety of hematological malignancies. However, graft-versus-host disease (GVHD), which is mediated by donor alloreactive T cells, limits the success of this procedure. Previous studies have demonstrated that several microRNAs (miRs) modulate graft-versus-host disease. miR-191 was previously reported to be able to support T cell survival after TCR stimulation. We hypothesize that miR191 regulates T cell response during GVHD. To test this hypothesis, we first studied miR-191 expression in alloreactive T cells. The result demonstrated that miR-191 was up-regulated in donor T cells isolated from murine GVHD recipients, suggesting that miR-191 may play a role in GVHD induction. We further studied the role of miR-191in GVHD using miR-191 deficient T cells (KO). Lethally irradiated (8.5 Gy) BALB/c mice were injected intravenously with 1×107 T cell-depleted bone marrow (TCDBM) cells along with 1×106 purified T cells from wild-type (WT) or KO mice, which are in C57BL/6 background. Interestingly, all recipients in the WT group died within 35 days after transplantation, while only one out of ten animals died in the KO group during an observation period of 56 days. Body weights and clinical scores were also improved in KO T cell recipients when compared with the WT controls. Similar results were also observed in a second GVHD model (C57BL/6→C3H/HeJ). To understand the mechanism by which miR-191 KO T cells have decreased ability to mediate GVHD, we first measured the ability of KO T cells to respond to alloantigens in vitro in a mixed lymphocytes reaction assay. Dramatically decreased alloresponse was observed with KO T cells as compared with WT T cells. Similarly, decreased clonal expansion was observed in KO T cells in vivo upon challenge with alloantigens as measured by bioluminescent imaging (Figure 1A). These results were further supported by data from a co-transfer experiment, in which equal numbers of WT and KO T cells were transplanted into the same GVHD recipient. At day7 after transplantation, KO T cells showed significantly reduced expansion in the spleen and liver compared with WT T cells. Reduced alloresponses mediated by KO T cells may not due to decreased proliferative capability directly as an in vivo carboxyfluorescein succinimidyl ester (CFSE) assay showed a comparable cell division between WT and KO T cells upon challenge with alloantigens. Rather, increased cell death is responsible for decreased alloresponse observed in KO T cells because dramatically increased number of dead cells was observed in KO group compared with WT group upon response to alloantigens in vitro and vivo. To determine the genes that are regulated by miR-191, we did a screening based on the prediction. Humans and mice share more than 100 predicted targets for miR-191. We chose top 20 of these targets for RT-qPCR screening. The result demonstrated that Taf5 was a target gene of miR-191. Expression of TAF5 protein was down-regulated in activated KO T cells when compared with the WT T cells. Finally, we investigated whether miR-191 KO T cells preserve graft-versus-leukemia effects. 1×106 T cells from WT or KO mice were transplanted into lethally irradiated BALB/c mice along with 1×107 TCDBM cells and 1×105 host-type BCL-1 cells. While all recipients that received only TCDBM and tumor cells developed lethal leukemia/lymphoma, none of WT and KO T cells recipients developed tumor. In conclusion, our findings reveal a critical role of miR-191 during GVHD process and demonstrate that miR-191 is a novel therapeutic target for GVHD. Figure 1 Disclosures No relevant conflicts of interest to declare.

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Early CD30 signaling is critical for adoptively transferred CD4+CD25+ regulatory T cells in prevention of acute graft-versus-host disease

Blood ◽

10.1182/blood-2006-07-038455 ◽

2006 ◽

Vol 109 (5) ◽

pp. 2225-2233 ◽

Cited By ~ 57

Author(s):

Robert Zeiser ◽

Vu H. Nguyen ◽

Jing-Zhou Hou ◽

Andreas Beilhack ◽

Elizabeth Zambricki ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Regulatory T Cells ◽

Graft Versus Host Disease ◽

Cell Function ◽

Treg Cells ◽

Host Disease ◽

Graft Versus Host ◽

Acute Graft

Abstract Murine CD4+CD25+ regulatory T cells (Treg cells) reduce acute graft-versus-host disease (aGvHD). However, surface molecules critical for suppression are unclear. Deficiency of CD30 (CD30−/−) leads to impaired thymic negative selection and augmented T-cell autoreactivity. Therefore, we investigated the role of CD30 signaling in Treg-cell function during aGvHD. Treg cells derived from CD30−/− animals were significantly less effective in preventing aGvHD lethality. Early blockade of the CD30/CD153 pathway with a neutralizing anti-CD153 mAb reduced Treg-mediated protection from proinflammatory cytokine accumulation and donor-type T-cell apoptosis. In vivo bioluminescence imaging demonstrated intact homing but reduced expansion of luciferase-expressing Treg cells when CD153 was blocked during the early phase after adoptive transfer. CD30 surface expression on Treg cells increased with alloantigen exposure, and CD153 expression on recipient-type dendritic cells increased in the presence of a proinflammatory environment. These data demonstrate that early CD30 signaling is critical for Treg-mediated aGvHD protection after major MHC-mismatch bone marrow transplantation.

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Antigen-Dependent Suppression of Graft Versus Host Disease by Foxp3-Induced Regulatory T Cells in Transplantation.

Blood ◽

10.1182/blood.v106.11.1302.1302 ◽

2005 ◽

Vol 106 (11) ◽

pp. 1302-1302

Author(s):

Michael H. Albert ◽

Yan Liu ◽

Claudio Anasetti ◽

Xue-Zhong Yu

Keyword(s):

T Cells ◽

T Cell ◽

Regulatory T Cells ◽

Graft Versus Host Disease ◽

Antigen Specificity ◽

Peptide Antigen ◽

Graft Versus Host ◽

Specific Peptide

Abstract Adoptive transfer of polyclonal CD4+CD25+ regulatory T cells (Tregs) can tolerize transplantation alloresponses and prevent lethal acute graft-versus-host disease (GVHD). For optimal suppressive function, Tregs need to be activated via their T-cell receptors (TCR), but the antigen specificity of wild type Tregs remains elusive, and therefore controlling potency and duration of Treg activity in the transplantation setting remains not feasible. In this study, we used a murine lethal acute GVHD model system to test the hypothesis that specifically activated, antigen-specific Tregs induced by foxp3 transduction could suppress the response of T effector cells to alloantigens in vitro and prevent GVHD in vivo more effectively than polyclonal Tregs. We found that the suppressive potential of TCR transgenic (Tg), antigen-specific CD4+CD25+ Tregs was much greater than that of polyclonal Tregs in vitro and in vivo. When activated by their specific peptide antigen, Tg Tregs protected 95% of recipients from lethal GVHD even at ten times lower doses than polyclonal Tregs. To facilitate the acquisition of larger numbers of antigen-specific Tregs, we transduced naive CD4+CD25- cells with foxp3, and observed that these foxp3-induced Tregs also suppressed alloresponses in vitro and prevented GVHD in vivo as effectively as naturally derived CD4+CD25+ Tregs. To enhance translational feasibility, we then used an antigen-specific CD4 Th1 T-cell clone as a source of Tregs after transduction with foxp3, and found those Tregs to effectively prevent GVHD in 90% of recipients. We further found that prevention of GVHD via foxp3-induced Tregs was also dependent on their activation by either a specific alloantigen expressed on recipient cells or by immunization with a specific peptide antigen. The findings of this study provide a basis for the concept that the onset and potency of alloresponse suppression in GVHD can be regulated by using Tregs with known antigen specificity. The novel evidence that antigen-specific T cell clones can be used as the cell source for foxp3-induced Tregs further improves the feasibility of using Tregs for modulating immune responses in vivo. These data suggest a novel approach to control induction of tolerance using Tregs as an adoptive immunotherapy in allogeneic transplantation.

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A combination of anti-CD3 and anti-CD7 ricin A-immunotoxins for the in vivo treatment of acute graft versus host disease

Blood ◽

10.1182/blood.v95.12.3693 ◽

2000 ◽

Vol 95 (12) ◽

pp. 3693-3701 ◽

Cited By ~ 26

Author(s):

Ypke V. J. M. van Oosterhout ◽

Liesbeth van Emst ◽

Anton V. M. B. Schattenberg ◽

Wil J. M. Tax ◽

Dirk J. Ruiter ◽

...

Keyword(s):

T Cells ◽

T Cell ◽

Nk Cells ◽

Graft Versus Host Disease ◽

T Cell Response ◽

Cytotoxic T Cell ◽

Host Disease ◽

Graft Versus Host ◽

Ricin A

Abstract This study evaluated the anti-graft versus host disease (GVHD) potential of a combination of immunotoxins (IT), consisting of a murine CD3 (SPV-T3a) and CD7 (WT1) monoclonal antibody both conjugated to deglycosylated ricin A. In vitro efficacy data demonstrated that these IT act synergistically, resulting in an approximately 99% elimination of activated T cells at 10−8 mol/L (about 1.8 μg/mL). Because most natural killer (NK) cells are CD7+, NK activity was inhibited as well. Apart from the killing mediated by ricin A, binding of SPV-T3a by itself impaired in vitro cytotoxic T-cell cytotoxicity. Flow cytometric analysis revealed that this was due to both modulation of the CD3/T-cell receptor complex and activation-induced cell death. These results warranted evaluation of the IT combination in patients with refractory acute GVHD in an ongoing pilot study. So far, 4 patients have been treated with 3 to 4 infusions of 2 or 4 mg/m2 IT combination, administered intravenously at 48-hour intervals. The T1/2 was 6.7 hours, and peak serum levels ranged from 258 to 3210 ng/mL. Drug-associated side effects were restricted to limited edema, fever, and a modest rise of creatine kinase levels. One patient developed low-titer antibodies against ricin A. Infusions were associated with an immediate drop of circulating T cells, followed by a more gradual but continuing elimination of T/NK cells. One patient mounted an extensive CD8 T-cell response directly after treatment, not accompanied with aggravating GVHD. Two patients showed nearly complete remission of GVHD, despite unresponsiveness to the extensive pretreatment. These findings justify further investigation of the IT combination for treatment of diseases mediated by T cells.

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Prevention of Transfusion-Associated Graft-Versus-Host Disease by Photochemical Treatment

Blood ◽

10.1182/blood.v93.9.3140 ◽

1999 ◽

Vol 93 (9) ◽

pp. 3140-3147 ◽

Cited By ~ 100

Author(s):

Joshua A. Grass ◽

Tamim Wafa ◽

Aaron Reames ◽

David Wages ◽

Laurence Corash ◽

...

Keyword(s):

T Cells ◽

Gamma Radiation ◽

Graft Versus Host Disease ◽

Clinical Signs ◽

Peripheral Blood Cell ◽

Control Group ◽

Host Disease ◽

Graft Versus Host

Abstract Photochemical treatment (PCT) with the psoralen S-59 and long wavelength ultraviolet light (UVA) inactivates high titers of contaminating viruses, bacteria, and leukocytes in human platelet concentrates. The present study evaluated the efficacy of PCT to prevent transfusion-associated graft-versus-host disease (TA-GVHD) in vivo using a well-characterized parent to F1 murine transfusion model. Recipient mice in four treatment groups were transfused with 108 splenic leukocytes. (1) Control group mice received syngeneic splenic leukocyte transfusions; (2) GVHD group mice received untreated allogeneic splenic leukocytes; (3) gamma radiation group mice received gamma irradiated (2,500 cGy) allogeneic splenic leukocytes; and (4) PCT group mice received allogeneic splenic leukocytes treated with 150 μmol/L S-59 and 2.1 J/cm2UVA. Multiple biological and clinical parameters were used to monitor the development of TA-GVHD in recipient mice over a 10-week posttransfusion observation period: peripheral blood cell levels, spleen size, engraftment by donor T cells, thymic cellularity, clinical signs of TA-GVHD (weight loss, activity, posture, fur texture, skin integrity), and histologic lesions of liver, spleen, bone marrow, and skin. Mice in the control group remained healthy and free of detectable disease. Mice in the GVHD group developed clinical and histological lesions of TA-GVHD, including pancytopenia, marked splenomegaly, wasting, engraftment with donor derived T cells, and thymic hypoplasia. In contrast, mice transfused with splenic leukocytes treated with (2,500 cGy) gamma radiation or 150 μmol/L S-59 and 2.1 J/cm2 UVA remained healthy and did not develop detectable TA-GVHD. Using an in vitro T-cell proliferation assay, greater than 105.1 murine T cells were inactivated by PCT. Therefore, in addition to inactivating high levels of pathogenic viruses and bacteria in PC, these data indicate that PCT is an effective alternative to gamma irradiation for prevention of TA-GVHD.

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