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IL-7 mediated protection against minor antigen-mismatched allograft rejection is associated with enhanced recovery of regulatory T cells

From the Department of Hematology, Erasmus University Medical Center Rotterdam, Rotterdam, The Netherlands (AECB, MB, SJPvS, E-JW, BL, EB, JJC); Department of Cell Biology and Histology, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands (HS)

Correspondence: Jan J. Cornelissen, MD, PhD, Department of Hematology, Erasmus University Medical Center Rotterdam/Daniel den Hoed Cancer Center, Groene Hilledijk 301, 3075 EA Rotterdam, The Netherlands. E-mail: j.cornelissen{at}erasmusmc.nl

	ABSTRACT

TOP ABSTRACT Design and Methods Results Discussion References

 
Background and Objectives: Interleukin-7 (IL-7) has been studied for its possible immunorestorative capacities following stem cell transplantation and has been shown to enhance post-transplant immune recovery predominantly by peripheral T-cell expansion. A major concern of IL-7 is its possible aggravating effect on graft-versus-host and host-versus-graft reactivity.

Design and Methods: To study the effect of IL-7 on host-versus-graft reactivity, we applied IL-7 in an experimental transplantation model using RAG-1^–/– mice supplied with B6 CD45.1 congenic T cells as recipients of T-cell depleted allogeneic bone marrow grafts.

Results: Rejection of minor antigen-mismatched bone marrow was significantly reduced in IL-7 treated recipients compared with PBS treated control mice. Rejection was observed in 2 out of 18 IL-7 treated mice compared with 9 out of 17 PBS treated mice (11% vs. 53%; p=0.012). IL-7 administration resulted in enhanced recovery of peripheral blood CD4⁺CD25⁺ regulatory T cells (Treg) with a concomitant increase in peripheral blood Foxp3 mRNA expression. IL-7R (CD127) was expressed by the vast majority of CD4⁺Foxp3⁺ T cells. The incidence of graft rejection following fully MHC mismatched bone marrow transplantation was not reduced nor enhanced by IL-7 administration.

Interpretation and Conclusions: Post-transplant IL-7 administration protects against minor antigen-mismatched bone marrow rejection, which may be due to enhanced Treg recovery.

Key words: interleukin-7, regulatory T cells, graft rejection, bone marrow transplantation.

The histocompatibility barrier between donor and recipient manifested as either graft-versus-host (GVH) or host-versus-graft (HVG) reactions continue to affect outcome after allogeneic hematopoietic stem cell transplantation (allo-SCT).¹ Graft-versus-host disease (GVHD), mediated by immunocompetent donor-derived T cells recognizing genetically disparate host cells, is one of the major causes of death following allo-SCT.² While advances in recipient-donor matching by molecular HLA typing and improvement of pre-transplant conditioning measures have reduced graft rejection, allo-SCT from alternative donors and allo-SCT following reduced intensity conditioning may still be complicated by impaired engraftment and overt graft rejection.^3–6 Apart from immunosuppressive agents administered prior to transplantation, the intensity of postgrafting immunosuppression has been shown to affect HVG reactivity and the incidence of rejection. ^7–9 Data collected from various murine models demonstrate that CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Treg) are important mediators of postgrafting immunosuppression. Pre-transplant depletion of recipient CD25⁺ T cells has been shown to reduce levels of donor engraftment and the adoptive transfer of large numbers of CD4⁺CD25⁺ Treg at the time of allo-SCT may prevent bone marrow graft rejection. ^10–12 The lymphopoietic cytokine interleukin-7 (IL-7) has been studied for its possible immunorestorative capacities following SCT in murine and non-human primate models. Whereas IL-7 administration might affect thymopoiesis, IL-7 is most importantly identified as key regulator of homeostatic peripheral T-cell expansion (HPE).^13–22 A major concern of post-transplant administration of IL-7 is its possible aggravating effect on GVH and HVG reactivity. Reports concerning the effect of IL-7 on the incidence and severity of GVH have given conflicting results.^15,23,24 Until now, there have been no studies reporting the effect of IL-7 on HVG alloreactivity. Therefore, we applied IL-7 in experimental murine stem cell transplantation models with major and minor histocompatibility barriers. We show that IL-7 administration protects against minor antigen-mismatched allograft rejection, which is associated with an increased recovery of Treg.

	Design and Methods

TOP ABSTRACT Design and Methods Results Discussion References

 
Mice
C57BL/6-RAG-1^–/– mice, originally obtained from The Jackson Immunoresearch Laboratories (Bar Harbor, ME), and C57BL/6-Ly5.1 mice were bred at the Experimental Animal Centre, Erasmus University Medical Center, Rotterdam, the Netherlands. 129Sv and Balb/C mice were purchased from Charles River Laboratories (Wilmington, MA, USA). Mice were maintained under specific pathogen–free conditions in individual ventilated cages with acidified water and antibiotics. All animal procedures were performed in accordance with protocols approved by the local Committee for Animal Experiments.

Bone marrow transplantation
Bone marrow obtained from crushed femurs and tibias of donor mice was depleted of T cells by incubation with rat antimouse CD4 (YTS191, YTA312) and rat antimouse CD8 (YTS169) monoclonal antibodies (mAbs)²⁵ followed by magnetic separation using the AutoMacs according to the manufacturer’s instructions (Miltenyi Biotec, Bergisch Gladbach, Germany). The efficacy of T-cell depletion was monitored by flow cytometry and was always found to be more than 2 log. Splenic T cells were obtained by negative selection using a cocktail of non–T-cell monoclonal antibodies according to the manufacturer’s instructions (Stem-Sep; Stem cell Technologies, Vancouver, BC, Canada). Purity of the T-cell fraction was always found to exceed 95% as confirmed by flow cytometry. Ten- to 14-weekold RAG-1^–/– mice supplied with graded doses of purified CD45.1⁺ congenic C57BL/6 T cells received either 12.5x10⁶ T-cell depleted 129Sv bone marrow cells (minor antigenmismatched) or 6x10⁶ T-cell depleted Balb/C bone marrow cells (fully MHC mismatched) by tail vein infusion (0.5 mL total volume) preceded by 3 and 6 Gy of total body irradiation respectively (¹³⁷Cs-source, Gammacell, Atomic Energy of Canada, Ottawa, Canada). During the 6–7 weeks following transplantation, mice received a daily subcutaneous injection of either PBS or 1 µg of recombinant human IL-7 (0.25 mL total volume), which was kindly provided by Dr Michel Morre (Cytheris, Vanves, France). Rejection was defined as a sustained peripheral blood CD45.2⁺CD3⁺ T-cell number below 50 cells/µL, which was monitored by flow cytometry at weekly intervals.

Flow cytometric analysis
At serial time points following transplantation, blood was collected from the murine retro-orbital plexus. Absolute numbers of peripheral blood lymphocytes were determined by a single-platform flow cytometric assay as previously described.¹⁸ MAbs used for flow cytometric analysis were fluorescein isothiocyanate (FITC)–conjugated anti-CD3, and anti-CD45.1 (Becton Dickinson, San Jose, CA, USA); phycoerythrin (PE)–conjugated anti-CD19, anti-CD45.1, anti-CD4 (Becton Dickinson), anti-CD127 (e-Bioscience), anti-CD8 (Beckman Coulter), and anti-IgG2a (BD Pharmingen, Alphen a/d Rijn, the Netherlands); Cy-Chrome–conjugated anti-CD45; allophycocyanin (APC)–conjugated anti-CD4, and anti-CD25 (Becton Dickinson); biotin-conjugated anti-CD45.2 (Becton Dickinson). Streptavidin-PE and streptavidin-APC (Becton Dickinson) were used to detect biotinylated monoclonal antibodies. The expression of Foxp3 was analysed by intracellular staining with anti-Foxp3 (e-Bioscience) after fixation and permeabilization of peripheral blood cells according to the manufacturer’s instructions (e-Bioscience, San Diego, CA, USA). Intracellular IL-4 and IFN-staining was performed on single cell suspensions prepared from spleen. Two million spleen cells were stimulated with either 25 ng/mL of phorbol-12-myristate 13-acetate (PMA; Sigma) and 1 µg/mL of ionomycin (Sigma) or with medium for 5 hours at 37°C and 5% CO2. Brefeldin A (Sigma) was added at a final concentration of 10 µg/mL for the final 4 hours of incubation. Cells were then stained with anti-CD45.1 and anti-CD4 monoclonal antibodies and after fixation and permeabilization (BD Pharmingen), cells were stained with anti-IL-4 and anti-IFN- (BD Pharmingen). Activation of the cells was confirmed by analysis of CD69 expression, which was over 95% in all stimulated samples. All analyses were performed in duplicate. All flow cytometric analyses were performed using a FACSCalibur (Becton Dickinson). Flow cytometric data were collected and analyzed using CELLQuest software (Becton Dickinson).

In vitro Treg activity assay
CD4⁺CD25^high Treg were isolated from spleen cells of IL-7 treated mice using a FACSAria cell sorter (Becton-Dickinson). The purity of the sorted cell population was always found to exceed 95% as confirmed by flow cytometry. Sorted CD4⁺CD25^high Treg cells from IL-7-treated mice (5x10⁴) were evaluated for their ability to suppress Tcell proliferation by co-culture with sorted CD4⁺CD25^– C57BL/6 responder T cells (5x10⁴) that were stimulated with 0.5 µg/mL anti-CD3 antibody and RAG-1^–/– spleen cells (2x10⁵) as antigen presenting cells. Cultures were performed in 96-well U-bottom plates. Responder cells with or without Treg were cultured in RPMI 1640 medium at 37°C and 5% CO2 for 3 days. Tritium thymidine (³H-TdR) was added at 1 µCi/well for the last 18 hours of culture. All assays were performed in quadruplicate.

Real-time quantitative PCR of Foxp3
RNA was purified from blood using the Qiagen Blood Mini kit (Qiagen, Hilden, Germany) according to manufacturer’s instructions after which cDNA was synthesized. The PCR was performed in a 25-µL reaction containing 20 µL of PCR mix Sybergreen (Applied Biosystems, Nieuwerkerk a/d IJssel, The Netherlands), 20 pmol/mL forward- and 20 pmol/mL reverse primer (Invitrogen, Merelbeke, Belgium), 6 µL sterile water) and 5 µL of cDNA. All reactions were performed in duplicate. PCR conditions were 95°C for 10 minutes, followed by 45 cycles of 95°C for 15 seconds, and 60°C for 1 minute. Sequences of the Foxp3 primers were: forward primer 5'-GCAATAGTTCCTTCCCAGAGTTCT-3' and reverse primer 5'-GGATGGCCCATCGGATAAG-3'. To compensate for variations in input cDNA the constant gene segment of the ribonuclease inhibitor (RI) gene was used as endogenous reference gene. Sequences of the RI primers were: forward primer 5'-TCCAGTGTGAGCAGCTGAG-3' and reverse primer 5'-TGCAGGCACTGAAGCACCA-3'. Foxp3 mRNA was detected with real-time quantitative RT-PCR using the ABI PRISM 7700 sequence detector (Applied Biosystems, Foster City, CA, USA) and computer software package SDS2.2. The mean threshold cycles (Ct) of the duplicates were used to calculate the expression of Foxp3 mRNA relative to the RI-control. Relative Foxp3 transcripts were calculated by the Ct method: Ct =Ct_Foxp3–Ct_RI. Relative Foxp3 transcript = 1/2^Ct.

Statistical analysis
The Mann-Whitney-U test was used to compare numbers of peripheral blood CD3⁺ T-cell subsets and peripheral blood Foxp3 expression between PBS- and IL-7 treated recipient mice and to compare Foxp3 expression in mice with and without graft rejection. Fisher’s exact test was used to compare the incidence of graft rejections between PBS- and IL-7 treated transplant recipients. All reported Pvalues are 2-sided, and a significance level of 0.05 was used.

	Results

TOP ABSTRACT Design and Methods Results Discussion References

 
IL-7 and allograft rejection
Peripheral homeostatic expansion of T cells has been shown to be the pre-dominant effect of exogenous IL-7 after T-cell replete BMT.¹⁸ Given this, we decided to evaluate the effect of IL-7 administration on host-versus-graft alloreactivity. Three Gy irradiated C57BL/6-RAG-1^–/– mice, supplied with escalating numbers of B6 CD45.1 congenic T cells, received an allogeneic MHC-matched minor antigen- mismatched T-cell depleted 129Sv bone marrow graft followed by IL-7 or PBS administration from day 1 until day 42. Engraftment was monitored at weekly intervals. The incidence of minor antigen-mismatched graft rejection depended on the numbers of B6 CD45.1 T cells supplied prior to transplantation (Figure 1). Post-transplant administration of IL-7 reduced the incidence of graft rejections in mice supplied with 10⁵ B6 T cells. Rejection was observed in 2 out of 18 IL-7 treated mice compared with 9 out of 17 PBS treated mice (11% vs. 53%; p=0.012). No rejections were observed in recipients of 1x10⁴ B6 T cells and recipients of 1x10⁶ B6 T cells all rejected their minor antigen-mismatched bone marrow graft irrespective of IL-7 treatment. Results are shown in Table 1. As shown before,¹⁸ IL-7 administration resulted in a sustained increase in numbers of B6 CD45.1⁺ T cells compared with PBS. At day 42 after BMT, PBS treated mice supplied with 1x10⁵ B6 T cells showed a mean number of 217 cells/µL (range: 41–707) compared with 578 cells/µL (range: 54–1,344) in IL-7 treated mice (p=0.02; Figure 2A). Thus, posttransplant IL-7 administration reduced the incidence of graft rejection despite an increase in the numbers of peripheral blood congenic B6 T cells.

View larger version (8K): [in this window] [in a new window] [Download PPT slide]   Figure 1. Allograft rejection following minor antigen-mismatched BMT. 3 Gy irradiated C57BL/6-RAG-1–/– supplied with escalating numbers of congenic B6 T cells received 12.5x106 MHC matched minor antigen-mismatched T-cell depleted 129Sv bone marrow cells. Bone marrow derived 129Sv T cells and supplied B6 T cells were distinguished by CD45.2 and CD45.1 expression respectively. Rejection was defined as a sustained peripheral blood CD45.2+CD3+ T-cell number below 50 cells/µL. Bone marrow derived CD45.2+CD3+ T cell numbers at day 42 are shown for all individual recipients of no T cells (n=5), 104 T cells (n=5), 105 T cells (n=11) and 106 T cells (n=5).

View larger version (9K): [in this window] [in a new window] [Download PPT slide]   Figure 2. IL-7 mediated peripheral T-cell expansion. C57BL/6- RAG-1–/– supplied with escalating numbers of congenic B6 CD45.1+ T cells received either 3 Gy irradiation followed by a T-cell depleted minor antigen-mismatched BMT or 6 Gy irradiation followed by a fully MHC mismatched BMT. PBS or IL-7 were administered subcutaneously (1 µg daily) from day 1 to day 42. Peripheral expansion of B6 T cells was studied by single-platform flow cytometry of peripheral blood samples taken at weekly intervals. Mean absolute numbers (± SEM) of CD45.1+CD3+ T-cells/µL blood are shown for (A) PBS (l, n=14) and IL-7 (L, n=16) treated recipients of 105 B6 T cells and a minor antigen-mismatched BM graft (129Sv) and (B) PBS (l, n=8) and IL-7 (L, n=9) treated recipients of 103 B6 T cells and a MHC mismatched BMT (Balb/C). *p<0.05 and **p<0.01.

IL-7 enhances BM- and congenic T-cell derived Treg recovery following MHC-matched minor antigen-mismatched BMT
IL-7 administration following minor antigen-mismatched allo-SCT resulted in fewer rejections despite peripheral expansion of mature congenic T cells. As Treg are known to be important mediators of postgrafting immunosuppression, we evaluated the effect of IL-7 treatment on endogenous Treg recovery by flow cytometric analysis of cell surface co-expression of CD4 and CD25. Absolute numbers of BM- and congenic T-cell derived CD4⁺CD25^high T cells were determined in peripheral blood samples taken at weekly intervals after BMT. Mice treated with IL-7 showed an increased recovery of both BM derived CD4⁺ and CD4⁺CD25^high T cells compared to PBS treated mice (Figure 3). The frequency of CD4⁺CD25^high Treg within the CD45.2⁺CD4⁺ T-cell pool was similar in IL-7 treated and PBS treated mice. Next we studied the effect of IL-7 administration on the CD4⁺CD25^high Treg present in the supplemented congenic CD45.1 T-cell pool. IL-7 treatment not only resulted in increased numbers of CD45.1⁺CD4⁺ T cells, but also in a moderate increase in numbers of CD45.1⁺CD4⁺CD25^high Treg (Figure 3). Then we analysed the suppressive ability of CD4⁺CD25^high T cells from IL-7 treated mice. Sorted CD4⁺CD25^high T cells, selected from spleens of IL-7 treated mice 35 days after transplantation, inhibited the anti-CD3-induced proliferation of CD4⁺CD25^– T cells in vitro, demonstrating their regulatory capacity (Figure 4).

View larger version (12K): [in this window] [in a new window] [Download PPT slide]   Figure 3. IL-7 enhances BM- and congenic T-cell derived CD4+ and CD4+CD25high T-cell recovery. 3 Gy irradiated C57BL/6-RAG-1–/– supplied with 105 congenic B6 CD45.1+ T cells received 12.5x106 Tcell depleted 129Sv bone marrow cells. PBS or IL-7 were administered subcutaneously (1 µg daily) from day 1 until day 49. Peripheral blood CD4+ and CD4+CD25high T-cell recovery were studied by single platform flow cytometry. Mean absolute numbers (± SEM) of BM derived CD4+ and CD4+CD25high T cells/µL blood and congenic T-cell derived CD4+ and CD4+CD25high T cells/µL blood in PBS treated mice (l, n=6) and IL-7-treated mice (L, n=6) are shown. *p<0.05 and **p<0.01.

View larger version (7K): [in this window] [in a new window] [Download PPT slide]   Figure 4. CD4+CD25high Treg from IL-7-treated mice have suppressive ability in vitro. Sorted CD4+CD25– T cells from C57BL/6 mice (5x104) stimulated with anti-CD3 mAb (0.5 µg/mL) and RAG-1–/– spleen cells (2x105) as antigen presenting cells (APC) were cultured in the presence or absence of sorted CD4+CD25high Treg from IL-7-treated mice (5x104). T-cell proliferation was measured by 3HTdR incorporation as shown by mean counts per minute (cpm ± SD) of quadruplicate samples.

View larger version (7K): [in this window] [in a new window] [Download PPT slide]   Figure 5. IL-7 enhances Foxp3 expression in peripheral blood cells. 3 Gy irradiated C57BL/6-RAG-1–/– supplied with 105 congenic B6 CD45.1+ T cells received 12.5x106 T-cell depleted 129Sv bone marrow cells. PBS or IL-7 were administered subcutaneously (1 µg daily) from day 1 until day 49. Foxp3 mRNA and RI mRNA were determined by real-time quantitative RT-PCR of peripheral blood samples taken at day 21 and day 49 after BMT. Relative Foxp3 expression is shown for PBS (l) and IL-7 (L) treated mice at day 21, PBS (l) and IL-7 (L) treated mice at day 49 and mice with (r) and without (R) graft rejection irrespective of cytokine treatment (n=5–6 mice per group).

View larger version (15K): [in this window] [in a new window] [Download PPT slide]   Figure 6. CD4+Foxp3+ regulatory T cells express CD127. Peripheral blood cells from normal B6 mice were stained with CD3, CD4, Foxp3 and IgG2a or CD127 mAb and analyzed by four-color flow cytometry. Cells were gated on CD3+CD4+ lymphocytes and analysed for CD127 and Foxp3 expression. Dotplots of isotypeand CD127-stained CD3+CD4+ T cells as representative examples of 7 individual mice are shown.

View larger version (7K): [in this window] [in a new window] [Download PPT slide]   Figure 7. IL-7 treatment does not alter the Th1/Th2 balance in RAG-1–/– recipients of MHC matched minor-antigen mismatched BMT 3. Gy irradiated C57BL/6-RAG-1–/– supplied with 105 congenic B6 CD45.1+ T cells received 12.5x106 T-cell depleted 129Sv bone marrow cells. Flow cytometric analysis of splenic IFN-producing congenic T-cell derived CD45.1+CD4+ T cells was performed at day 35 posttransplant both in PBS (m ) and IL-7 (L) treated recipient mice either with or without graft rejection. The percentage of CD45.1+CD4+IFN-+ T cells in PBS and IL-7 treated mice without stimulation and after stimulation with PMA and ionomycin is shown.

	Discussion

TOP ABSTRACT Design and Methods Results Discussion References

Several possible explanations for the observed protective effect were considered. As postgrafting immunosuppression is important for prevention of graft rejection^7,8 and CD4⁺CD25⁺Foxp3⁺ Treg are important mediators of postgrafting immunosuppression,²⁸ we first hypothesized that IL-7 might reduce allograft rejection by increasing the number of Treg after BMT. In our longitudinal analysis of T-cell recovery in recipients of MHC matched minor antigen- mismatched bone marrow cells, we did indeed find an enhanced recovery of CD4⁺CD25^high T cells and increased levels of Foxp3 mRNA in IL-7 treated mice compared with PBS treated-control mice. Furthermore, significantly higher levels of Foxp3 mRNA were measured in all mice that did not reject the marrow graft compared with mice that did reject the graft. Early after transplantation, all Treg are derived from the supplied CD45.1 congenic mature T cells. From day 21 onwards, Treg originating from the bone marrow appear and gradually become the major population of peripheral blood Treg. Both populations of Treg are increased by IL-7 treatment and may have contributed to the observed reduction in HVG reactivity. Our findings compare well to several other reports showing that adoptive transfer of Treg may prevent bone marrow graft rejection.^10,12,29 Rejection of MHC-matched minor antigen-mismatched bone marrow is a lengthy process that may be modulated both early and later after transplantation. Early after bone marrow transplantation, adoptively transferred CD62L^hi Treg suppress bone marrow rejection by suppression of the priming of alloreactive T cells in secondary lymphoid organs.¹⁰ At later stages, effector/memory like CD62E/P⁺CCR5⁺ Treg may migrate into peripheral sites to suppress the expansion, cytokine secretion and/or cytolytic function of alloreactive effector T cells.^30–32

An alternative explanation for the observed protective effect of IL-7 could have been a direct immunosuppressive effect of IL-7 on T cells by affecting the Th1/Th2 balance. In our model of MHC matched minor-antigen mismatched BMT the Th1/Th2 balance was unaffected by IL-7 administration. Our observations are in line with reports by Alpdogan et al. showing that there is no significant difference in IFN-and IL-4 production between IL-7 and PBS treated transplant recipient mice.^15,20

In contrast to minor antigen-mismatched bone marrow graft rejection, the incidence of fully MHC mismatched graft rejection was not affected by IL-7. Since the frequency of allo-MHC reactive T lymphocytes is much higher compared with the frequency of minor antigen reactive T lymphocytes, rejection following fully MHC mismatched BMT may be more difficult to suppress by Treg. Furthermore, natural killer (NK) cells, next to T lymphocytes, might have contributed to MHC mismatched graft rejection. NK cells have proven to be a barrier to engraftment of fully MHC mismatched bone marrow and although Treg are capable of inhibiting NK-cell function in vitro, the inhibitory effect might be overcome in conditions resulting in significant cytokine production such as acute infection or allo-SCT.^33,34

IL-7 and its role in alloreactivity have been the subject of study in several reports which have so far all concerned GVH reactivity. Sinha and co-workers applied IL-7 in a MHC mismatched parent F1 model and showed significantly increased GVH reactivity in IL-7 treated recipients of escalating subthreshold numbers of T cells.²³ By contrast, Alpdogan and co-workers showed significantly reduced GVH reactivity following MHC mismatched BMT (parent F1) and no difference in GVH reactivity between PBS and IL-7 treated recipients of minor antigen-mismatched BMT.¹⁵ Differences in the dose of IL-7 used and the duration of therapy might have contributed to the observed differences between the two studies. Recently, Gendelman et al. reported a higher incidence of GVH reactivity in IL-7 treated recipients of MHC mismatched bone marrow. However, this study was restricted to unirradiated mice. In irradiated transplant recipients, GVH reactivity was not aggravated by IL-7 treatment.²⁴ Collectively, these studies do suggest that IL-7 might significantly worsen GVH reactivity. By contrast, in this first study concerning the effect of IL-7 on HVG reactivity, alloreactivity was definitely not increased by IL-7. More importantly, we even observed diminished HVG reactivity following minor antigen-mismatched BMT, which was associated with enhanced recovery of Treg. So apart from its immunorestorative capacities, IL-7 might also be useful in inducing transplantation tolerance especially in the setting of T-cell depleted allogeneic stem cell grafts.

	Footnotes

 
The first two authors contributed equally to the manuscript

Authors’ Contributions

AECB: designed and performed research, collected and analyzed data and wrote the paper; MB: designed and performed research, collected and analyzed data and wrote the paper; SJP: performed research, collected and analyzed data; E-JW: performed research; HS: designed research and critically revised the manuscript; BL: designed research and critically revised the manuscript; EB: designed research and wrote the paper; JJC: designed research and wrote the paper.

Conflict of Interest

The authors reported no potential conflicts of interest.

Received for publication August 7, 2006. Accepted for publication May 16, 2007.

	References

TOP ABSTRACT Design and Methods Results Discussion References

 

1. Gale RP, Reisner Y. Graft rejection and graft-versus-host disease: mirror images. Lancet 1986;28:1468-70.
2. Anasetti C. Advances in the prevention of graft-versus-host disease after hematopoietic cell transplantation. Transplantation 2004;77:S79-S83.[CrossRef][ISI][Medline]
3. Petersdorf EW, Gooly TA, Anasetti C, Martin PJ, Smith AG, Mickelson EM, et al. Optimizing outcome after unrelated marrow transplantation by comprehensive matching of HLA class I and II alleles in the donor and recipient. Blood 1998;92:3515-20.[Abstract/Free Full Text]
4. Davies SM, Kollman C, Anasetti C, Antin JH, Gajewski J, Casper JT, et al. Engraftment and survival after unrelated donor BMT: a report from the national marrow donor program. Blood 2000;96:4096-102.[Abstract/Free Full Text]
5. Mickelson EM, Petersdorf EW, Hansen JA. HLA matching and hematopoietic cell transplant outcome. Clin Transpl 2002;15:263-71.[CrossRef][ISI]
6. Socié G, Clift RA, Blaise D, Devergie A, Ringden O, Martin PJ, et al. Busulfan plus cyclophosphamide compared with total-body irradiation plus cyclophosphamide before marrow transplantation for myeloid leukemia: long-term follow-up of the 4 randomized studies. Blood 2001;98:3569-74.[Abstract/Free Full Text]
7. Storb R, Yu C, Wagner JL, Deeg HJ, Nash RA, Kiem HP, et al. Stable mixed hematopoietic chimerism in DLA-identical littermate dogs given sublethal total body irradiation before and pharmacological immunosuppression after marrow transplantation. Blood 1997;89:3048-54.[Abstract/Free Full Text]
8. Hogan WJ, Little MT, Zellmer E, Friedetzky A, Diaconescu R, Gisburne S, et al. Postgrafting immunosuppression with sirolimus and cyclosporine facilitates stable mixed hematopoietic chimerism in dogs given sublethal total body irradiation before marrow transplantation from DLA-identical littermates. Biol Blood Marrow Transplant 2003;9:489-95.[CrossRef][ISI][Medline]
9. McSweeney PA, Niederwieser D, Shizuru JA, Sandmaier BM, Molina AJ, Maloney DG, et al. Hematopoietic cell transplantation in older patients with hematologic malignancies: replacing high-dose cytotoxic therapy with graft-versus-tumor effects. Blood 2001;97:3390-400.[Abstract/Free Full Text]
10. Taylor PA, Panoskaltsis-Mortari A, Swedin JM, Lucas PJ, Gress RE, Levine BL, et al. Lselectinhi but not Lselectinlo CD4⁺CD25⁺ regulatory T cells are potent inhibitors of GVHD and BM graft rejection. Blood 2004;104:3804-12.[Abstract/Free Full Text]
11. Johnson BD, Konkol MC, Truitt RL. CD25⁺ immunoregulatory T-cells of donor origin suppress alloreactivity after BMT. Biol Blood Marrow Transplant 2002;8:525-35.[CrossRef][ISI][Medline]
12. Joffre O, Gorsse N, Romagnoli P, Hudrisier D, Van Meerwijk JPM. Induction of antigen-specific tolerance to bone marrow allografts with CD4⁺CD25⁺ T lymphocytes. Blood 2004;103:4216-21.[Abstract/Free Full Text]
13. Bolotin E, Smogorzewska M, Smith S, Widmer M, Weinberg K. Enhancement of thymopoiesis after bone marrow transplant by in vivo interleukin-7. Blood 1996;88:1887-94.[Abstract/Free Full Text]
14. Mackall CL, Fry TJ, Bare C, Morgan P, Galbraith A, Gress RE. IL-7 increases both thymic-dependent and thymic-independent T-cell regeneration after bone marrow transplantation. Blood 2001;97:1491-7.[Abstract/Free Full Text]
15. Alpdogan O, Schmaltz C, Muriglan SJ, Kappel BJ, Perales MA, Rotolo JA, et al. Administration of interleukin-7 after allogeneic bone marrow transplantation improves immune reconstitution without aggravating graftversus-host disease. Blood 2001;98:2256-65.[Abstract/Free Full Text]
16. Schluns KS, Kieper WC, Jameson SC, Lefrancois L. Interleukin 7 mediates the homeostasis of naive and memory CD8 T cells in vivo. Nat Immunol 2000;1:426-32.[CrossRef][ISI][Medline]
17. Storek J, Gillespy T, Lu H, Joseph A, Dawson MA, Gough M, et al. Interleukin-7 improves CD4 T-cell reconstitution after autologous CD34 cell transplantation in monkeys. Blood 2003;101:4209-18.[Abstract/Free Full Text]
18. Broers AE, Posthumus-van Sluijs SJ, Spits H, Van der Holt B, Lowenberg B, Braakman E, et al. Interleukin-7 improves T-cell recovery after experimental T-cell-depleted bone marrow transplantation in T-cell deficient mice by strong expansion of recent thymic emigrants. Blood 2003;102:1534-40.[Abstract/Free Full Text]
19. Fry TJ, Connik E, Falloon J, Lederman MM, Liewehr DJ, Spritzler J, et al. A potential role for interleukin-7 in T-cell homeostasis. Blood 2001;97:2983-90.[Abstract/Free Full Text]
20. Alpdogan O, Muriglan SJ, Eng JM, Willis LM, Greenberg AS, Kappel BJ, et al. IL-7 enhances peripheral T cell reconstitution after allogeneic hematopoietic stem cell transplantation. J Clin Invest 2003;112:1095-107.[CrossRef][ISI][Medline]
21. Fry TJ, Mackall CL. The many faces of IL-7: from lymphopoiesis to peripheral T cell maintenance. J Immunol 2005;174:6571-6.[Abstract/Free Full Text]
22. Alpdogan O, Van den Brink MR. IL-7 and IL-15: therapeutic cytokines for immunodeficiency. Trends Immunol 2005;26:56-64.[CrossRef][ISI][Medline]
23. Sinha ML, Fry TJ, Fowler DH, Miller G, Mackall CL. Interleukin 7 worsens graft-versus-host disease. Blood 2002;100:2642-9.[Abstract/Free Full Text]
24. Gendelman M, Hecht T, Logan B, Vodanovic-Jankovic S, Komorowski R, Drobyski WR. Host conditioning is a primary determinant in modulating the effect of IL-7 on murine graft-versus-host disease. J Immunol 2004;172:3328-36.[Abstract/Free Full Text]
25. Cobbold S, Martin G, Waldmann H. Monoclonal antibodies for the prevention of graft-versus-host disease and marrow graft rejection. The depletion of T-cell subsets in vitro and in vivo. Transplantation 1986;42:239-47.[ISI][Medline]
26. Liu W, Putnam AL, Xu-yu Z, Szot GL, Lee MR, Zhu S, et al. CD127 expression inversely correlates with FoxP3 and suppressive function of human CD4⁺ Treg cells. J Exp Med 2006;203:1701-7.[Abstract/Free Full Text]
27. Fowler DH, Gress RE. Th2 and Tc2 cells in the regulation of GVHD, GVL, and graft rejection: considerations for the allogeneic transplantation therapy of leukemia and lymphoma. Leuk Lymphoma 2000;38:221-34.[ISI][Medline]
28. Walsh PT, Taylor DK, Turka LA. Tregs and transplantation tolerance. J Clin Invest 2004;114:1398-403.[CrossRef][ISI][Medline]
29. Karim M, Feng G, Wood KJ, Bushell AR. CD25⁺CD4⁺ regulatory T cells generated by exposure to a model antigen prevent allograft rejection: antigen-specific reactivation in vivo is critical for bystander regulation. Blood 2005;105:4871-7.[Abstract/Free Full Text]
30. Huehn J, Hamann A. Homing to suppress: address codes for Treg migration. Trends Immunol 2005;26:632-6.[CrossRef][ISI][Medline]
31. Wysocki CA, Jiang Q, Panoskaltsis-Mortari A, Taylor PA, McKinnon KP, Su L, et al. Critical role for CCR5 in the function of donor CD4⁺CD25⁺ regulatory T cells during graft-versus-host disease. Blood 2005;106:3300-7.[Abstract/Free Full Text]
32. Siegmund K, Feuerer M, Siewert C, Ghani S, Haubold U, Dankof A, et al. Migration matters: regulatory Tcell compartimentalization determines suppressive activity in vivo. Blood 2005;106:3097-04.[Abstract/Free Full Text]
33. Barao I, Murphy WJ. The immunobiology of natural killer cells and bone marrow allograft rejection. Biol Blood Marrow Transplant 2003;9:727-41.[CrossRef][ISI][Medline]
34. Ghiringhelli F, Menard C, Terme M, Flament C, Taieb J, Chaput N, et al. CD4⁺CD25⁺ regulatory T cells inhibit natural killer cell functions in a transforming growth factor-ß-dependent manner. J Exp Med 2005;202:1075-85.[Abstract/Free Full Text]

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