Scholarly article on topic 'Immune Recovery in Adult Patients after Myeloablative Dual Umbilical Cord Blood, Matched Sibling, and Matched Unrelated Donor Hematopoietic Cell Transplantation'

Immune Recovery in Adult Patients after Myeloablative Dual Umbilical Cord Blood, Matched Sibling, and Matched Unrelated Donor Hematopoietic Cell Transplantation Academic research paper on "Clinical medicine"

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{Adult / "Dual umbilical cord blood transplantation" / "Matched sibling transplantation" / "Matched unrelated donor transplantation" / "Immune recovery" / "TCR excision DNA circles (TRECs)" / "Post-thymic T cell reconstitution"}

Abstract of research paper on Clinical medicine, author of scientific article — Junya Kanda, Lun-Wei Chiou, Paul Szabolcs, Gregory D. Sempowski, David A. Rizzieri, et al.

Immunologic reconstitution after allogeneic hematopoietic cell transplantation is a critical component of successful outcome. Umbilical cord blood (UCB) transplantation in adult recipients is associated with slow and often inadequate immune recovery. We characterized the kinetics and extent of immune recovery in 95 adult recipients after a dual UCB (n = 29) and matched sibling donor (n = 33) or matched unrelated donor (n = 33) transplantation. All patients were treated with myeloablative conditioning. There were no differences in the immune recovery profile of matched sibling donor and matched unrelated donor recipients. Significantly lower levels of CD3+, CD4+, and CD8+ T cells were observed in UCB recipients until 6 months after transplantation. Lower levels of regulatory T cells persisted until 1 year after transplantation. Thymopoiesis as measured by TCR rearrangement excision circle was comparable among all recipients by 6 months after transplantation. In a subset of patients 1 year after transplantation with similar levels of circulating T cells and TCR rearrangement excision circle, there was no difference in TCR diversity. Compared to HLA-identical matched sibling donor and matched unrelated donor adult hematopoietic cell transplantation recipients, quantitative lymphoid recovery in UCB transplantation recipients is slower in the first 3 months, but these differences disappeared by 6 to 12 months after transplantation.

Academic research paper on topic "Immune Recovery in Adult Patients after Myeloablative Dual Umbilical Cord Blood, Matched Sibling, and Matched Unrelated Donor Hematopoietic Cell Transplantation"

ASBMI

American Society for Blood and Marrow Transplantation

Immune Recovery in Adult Patients after Myeloablative Dual Umbilical Cord Blood, Matched Sibling, and Matched Unrelated Donor Hematopoietic

Cell Transplantation

Junya Kanda,1'6 Lun-Wei Chiou,1 Paul Szabolcs,2 Gregory D. Sempowski,3 David A. Rizzieri,1 Gwynn D. Long,1 Keith M. Sullivan,1 Cristina Gasparetto,1 John P. Chute,1 Ashley Morris,1 Jacalyn McPherson,1 Jeffrey Hale,3 John Andrew Livingston,1 Gloria Broadwater,4 Donna Niedzwiecki,5 Nelson J. Chao,1 Mitchell E. Horwitz1

Immunologic reconstitution after allogeneic hematopoietic cell transplantation is a critical component of successful outcome. Umbilical cord blood (UCB) transplantation in adult recipients is associated with slow and often inadequate immune recovery. We characterized the kinetics and extent of immune recovery in 95 adult recipients after a dual UCB (n = 29) and matched sibling donor (n = 33) or matched unrelated donor (n = 33) transplantation. All patients were treated with myeloablative conditioning. There were no differences in the immune recovery profile of matched sibling donor and matched unrelated donor recipients. Significantly lower levels of CD3 + , CD4+, and CD8+ T cells were observed in UCB recipients until 6 months after transplantation. Lower levels of regulatory T cells persisted until 1 year after transplantation. Thymo-poiesis as measured by TCR rearrangement excision circle was comparable among all recipients by 6 months after transplantation. In a subset of patients 1 year after transplantation with similar levels of circulating T cells and TCR rearrangement excision circle, there was no difference in TCR diversity. Compared to HLA-identical matched sibling donor and matched unrelated donor adult hematopoietic cell transplantation recipients, quantitative lymphoid recovery in UCB transplantation recipients is slower in the first 3 months, but these differences disappeared by 6 to 12 months after transplantation.

Biol Blood Marrow Transplant 18: 1664-1676 (2012) © 2012 American Society for Blood and Marrow Transplantation

KEY WORDS: Adult, Dual umbilical cord blood transplantation, Matched sibling transplantation, Matched unrelated donor transplantation, Immune recovery, TCR excision DNA circles (TRECs), Post-thymic T cell reconstitution

From the 'Division of Cellular Therapy, Department of Medicine, Duke University Medical Center, Durham, North Carolina;

2Department of Pediatrics, Duke University Medical Center,

Durham, North Carolina; Department of Medicine and

Human Vaccine Institute, Duke University Medical Center,

Durham, North Carolina; Cancer Statistical Center, Duke University Medical Center, Durham, North Carolina; Department of Biostatistics and Bioinformatics, Duke University Medical Center, Durham, North Carolina; and 6Division of Hematology, Saitama Medical Center, Jichi Medical University, Saitama, Japan. Financial disclosure: See Acknowledgments on page 1675. Correspondence and reprint requests: Mitchell E. Horwitz, MD, Division of Cellular Therapy, Department of Medicine, Duke University Medical Center, 2400 Pratt Street, DUMC 3961, Durham, NC 27705 (e-mail: mitchell.horwitz@duke.edu). Received February 7, 2012; accepted June 6, 2012 © 2012 American Society for Blood and Marrow Transplantation 1083-8791/$36.00

http://dx.doi.org/10.10167j.bbmt.2012.06.005

INTRODUCTION

Allogeneic hematopoietic cell transplantation (HCT) is an established cellular therapy for patients with hematologic malignancies, bone marrow (BM) failure syndrome, and immune disorders [1]. After myeloablative allogeneic HCT, host immunity is ablated by the conditioning regimen. Immunologic reconstitution arises from maturation of donor stem cell-derived lymphoid progenitors and peripheral expansion of mature immune cells included in the donor graft [2,3]. During the initial neutropenic phase of the HCT, recipients have a high risk of bacterial infection. However, a profoundly immunocompromised state continues after neutrophil engraftment due to deficiencies or impairment of cellular immune reconstitution. Initial cellular immune reconstitution after HCT largely depends on thymic-independent

peripheral expansion of donor-derived memory T cells. This is followed by thymic-dependent maturation of stem cell-derived lymphoid progenitor cells [2,3]. Because the repertoire of peripherally expanded memory T cells is limited, thymic-dependent maturation is important for diversification of the T cell repertoire and strengthening host defense against pathogens and even recurrence of malignancy.

Unrelated umbilical cord blood (UCB) has emerged as a viable alternative source ofhematopoietic stem cells for adult and pediatric allogeneic HCT [4-6]. In contrast to peripheral blood or BM grafts, UCB grafts contain few, if any antigen-specific memory T cells and a higher proportion of naive T cells. This limits the potential for thymic-independent immune recovery [7-10] and is felt to be one of the main reasons why adult UCB HCT recipients are more prone to viral infections compared with patients receiving peripheral blood or BM stem cell grafts. The challenge of posttransplantation immune reconstitution is further complicated in adult patients as a consequence of thymic atrophy, thereby limiting the thymic-dependent pathways of lymphopoiesis [11,12]. Available data suggest exceedingly slower and less robust immune recovery after adult UCB transplantations than pediatric UCB transplantations [9].

Although immune reconstitution after UCB transplantation has been evaluated by several groups [7-9,13], there are limited data on how it compares after HCT from other graft sources [14]. We present here results of a comprehensive comparison of immune recovery in adult patients after T cell-replete myeloablative conditioning and allogeneic dual UCB, matched sibling donor (MSD), or matched unrelated donor (MUD) HCT.

METHODS

Patients

Reconstitution of immune cell populations was prospectively characterized in a consecutive cohort of 146 adult patients ($18 years old) with hematological malignancies undergoing T cell replete myeloablative HCT, using MSD or MUD peripheral blood stem cells (PBSCs), or dual UCB donor grafts, between April 2006 and December 2010. PBSC recipients were conditioned with either a total body irradiation (TBI)-based regimen (TBI $ 12 Gy) or i.v. busulfan (12.8 mg/kg) (Bu)-based regimen, and UCB transplantation recipients were conditioned with a TBI ($13.2 Gy) and fludarabine (160 mg/m2) (Flu)-based regimen. No patient received in vivo (such as antithymocyte globulin [ATG]) or ex vivo T cell depletion. The algorithm for donor selection was MSD first, followed by an MUD, followed by UCB. PBSC grafts were allele-level matched at HLA-A, HLA-B, HLA-C,

and HLA-DRB1, whereas dual UCB grafts were at least 4 of 6 HLA-matched with the recipient, and 3 of 6 HLA-matched between grafts (low-resolution for A and B, and high-resolution for DRB1). A total of 34 patients with primary or secondary graft failure (UCB recipients, n = 7; MSD/MUD recipients, n = 1) or those who died or relapsed within 3 months after HCT (UCB recipients, n = 11; MSD recipients, n = 10; MUD recipients, n = 5) were excluded from the analysis of immune reconstitution to focus on comparing immune recovery 3 to 12 months after transplantation. An additional 17 patients (UCB recipients, n = 3; MSD/MUD recipients, n = 14) were not evaluable due to lack of immune recovery data collection. As a result, 95 patients were included in the analysis of immune reconstitution. In addition to these 95 patients, all consecutive patients (n = 146) were included in the progression-free survival (PFS) outcomes analysis. Standard-risk diseases were defined as acute myelogenous leukemia (AML) in first or second complete remission, acute lymphoblastic leukemia (ALL) in first or second complete remission, myelodysplastic syndromes; refractory anemia or refractory anemia with excess of blasts-1, Hodgkin or non-Hodgkin lymphoma in any chemotherapy sensitive remission, chronic myelogenous leukemia in first or second chronic phase, and myelofibrosis. High-risk diseases were those other than standard-risk disease. All research samples were collected after obtaining written informed consent for participation in accordance with the Declaration of Helsinki on a protocol approved by the Duke University Medical Center Institutional Review Board.

Measurement of Immune Recovery

Quantification of the following subsets was performed by flow cytometry on fresh peripheral blood at approximately 1 month before transplantation and then 1.5, 3, 6, and 12 months after transplantation [15,16]: natural killer (NK) (CD3-, CD16 +/CD561) and natural killer T cells (NKT) (CD31, CD161/ CD561) cells, B cells (CD191, CD3-, CD16-, CD56-), CD31, CD41, CD81, regulatory (CD41, CD251, CD62L1), cytotoxic/late memory (CD81, CD571, CD28-), and activated (CD81, HLA-DR1) T cells, naive CD41 T cells with L-selectin expression, which is suggestive of recent thymic emigrants (RTEs) (CD41, CD45RA1/CD45RO-, CD62L1), plasmacytoid dendritic cells (DCs) (CD1231, CD11c-), and myeloid DCs (CD123 -, CD11c1).

Quantification of recent thymic immigrants as determined by the presence of TCR rearrangement excision circles (TREC) was retrospectively performed by real-time quantitative-PCR of DNA collected from an isolated fraction of CD31 T cells, as previously described [17]. Samples were analyzed in duplicate and expressed as TREC per 10,000 CD31 T cells.

Spectratyping was performed to analyze diversity in the TCR repertoires produced by the rearrangements of the variable region genes [18,19]. Selected cDNA samples underwent survey-level sequencing for TCR-b repertoire analysis (Adaptive TCR Corporation with ImmunoSeq) [20,21]. A standard algorithm was used to identify which V, D, and J segments comprised each TCR-b CDR3. Sequence reads from each donor T cell sample were determined to be productive or nonproductive based on CDR3 sequences. CDR3 sequences that could result in a functional TCR were considered to be productive rearrangements. Entropy (ie, Shannon Entropy), a measure of the uniformity of the frequency distribution of a TCR-b repertoire, was performed for productive clones as follows: Entropy = sum over all clones of —1 * [(frequency of clone) * (log2 frequency of clone)]. Entropy is reported in bits, and it ranges from 0 in a sample with only one clone to log2 (No. of unique clones) for a sample with a uniform distribution of clone frequencies. Monoclonal or oligoclonal samples have low entropy, and polyclonal highly diverse samples have an entropy just under log2 (No. uniques).

Statistical Analysis

The mean ages for the 3 transplantation types were compared using the analysis-of-variance test. The median follow-up periods of survivors were compared using the Kruskal-Wallis test. The Pearson chi-square test of proportions was used to compare associations between clinical factors and transplantation type. The Wilcoxon rank-sum test was used to compare immune recovery parameters at approximately 1 month before transplantation and 1.5, 3, 6, and 12 months after transplantation, adjusting P values for multiple comparison with the Adaptive Holms step-down Bon-ferroni method [22]. The same method was also used to compare the number of TRECs at 1 month before transplantation and 3, 6, and 12 months posttransplantation. Acute graft-versus-host-disease (aGVHD) or chronic graft-versus-host disease (cGVHD) was characterized using standard criteria [23,24]. Cytomegalovirus (CMV) reactivation was defined as positive if more than 200 copies of CMV were amplified in peripheral blood by real-time quantitative PCR. The actual probabilities along with 95% confidence intervals (CIs) of aGVHD and cGVHD, CMV reactivation and disease, and treatment-related mortality (TRM) were estimated on the basis of cumulative incidence curves to accommodate the following competing events [25]: death without GVHD for aGVHD and cGVHD, death without CMV reactivation/disease for CMV reactivation/disease, and relapse for TRM; the groups were compared using the Gray test [26]. Cumulative corticosteroid usage beginning on

the day of transplantation until the 3-month, 6-month, or 1-year time point after transplantation was determined by the area under the curve (AUC) [27]. The central tendency of corticosteroid AUC was compared using the Wilcoxon rank-sum test. TCR diversity, expressed as an Entropy score, was compared using the t test. PFS was defined as the period from 3 months after transplantation until disease progression or death, whichever occurred first and censored at time of last follow-up. The probability of PFS was estimated according to the Kaplan-Meier method, and groups were compared using the log-rank test. Cox proportional hazards multivariate regression modeling was used to predict PFS. The following variables were analyzed in a bivariate model adjusted for donor type (MSD/MUD or UCB) as well as in a univariate model in the MSD/MUD group: recipient age (#41 (median age) or >41), recipient sex, disease (myeloid or lymphoid disease), type of conditioning regimen (TBI-based or Bu-based regimen), GVHD prophylaxis (cy-closporine-based or tacrolimus-based, or other), aGVHD (no and grade I or grade II-IV aGVHD), and each lymphocyte subset at 3 months after transplantation dichotomized at the median value. Due to few events, a parallel analysis was not performed in the UCB group. All tests were 2-sided, and a P value of less than .05 was considered to indicate statistical significance. All statistical analyses were performed using SAS (SAS Institute, Cary, NC) and Stata (Stata Corp., College Station, TX).

RESULTS

Patient Characteristics

Patient characteristics are shown in Table 1. The UCB recipients (mean age, 36; range, 19-55 years) were younger than MSD recipients (mean age, 45; range, 24-65 years) and MUD recipients (mean age, 41; range, 20-56 years; P < .01). All UCB recipients received a myeloablative dose of TBI and Flu as a part of a conditioning regimen, whereas half of MSD/MUD recipients received a non-TBI, Bu-based conditioning regimen. Two-thirds of all patients received transplantations for AML or myelodysplastic syndromes. Most of the UCB and MUD recipients received tacrolimus-based GVHD prophylaxis, whereas 40% of the MSD recipients received cyclosporine-based GVHD prophylaxis.

The median combined total nucleated cell dose for the UCB recipients was 4.6 (range, 3.3-8.6; n = 29) x 107/kg. Each unit of the UCB graft contained a minimum of 1.5 x 107/kg. The median total nucleated cell dose for the MSD and MUD grafts was 13.0 (range, 3.6-31.7; n = 31) x 108/kg and 8.1 (range, 3.2-15.1; n = 32) x 108/kg, respectively, and the median CD34+cell dose for the MSD and MUD

Biol Blood Marrow Transplant 18:1664-1676, 2012 Table 1. Patient Characteristics

Matched Sibling Peripheral Matched Unrelated Peripheral

Characteristics UCB (n 5 29) Blood (n = 33) Blood (n = 33)

Age, years, mean (range) 36 (19-55) 45 (24-65) 41 (20-56)

Recipient sex

Female 12 (41%) 16 (48%) 19 (58%)

Male 17 (59%) 17 (52%) 14(42%)

Disease

Myeloid disease

AML 18 (62%) 16 (48%) 21 (64%)

CML 2 (7%) 3 (9%) 1 (3%)

MDS 2 (7%) 6 (18%) 3 (9%)

MF 0 (0%) 2 (6%) 0 (0%)

Lymphoid disease

ALL 5(17%) 5(15%) 5(15%)

ML 2 (7%) 1 (3%) 3 (9%)

Disease risk

Standard 25 (86%) 25 (76%) 26 (79%)

High 4(14%) 8 (24%) 7(21%)

AML/ALL

CRI 5 (22%) 10 (48%) 14(54%)

CR2 16 (70%) 5 (24%) 10(38%)

CR3+ 2 (9%) 6 (29%) 2 (8%)

History of previous chemotherapy (ML)

#3 courses 2 0 2

>4 courses 0 1 1

Conditioning regimen

TBI-based 29 (100%) 14 (42%) 19 (58%)

TBI + cyclophosphamide 0 10 16

TBI + etoposide 0 3 3

TBI + Flu 20 1 0

TBI + Fu + cyclophosphamide 6 0 0

TBI + Fu + thiotepa 3 0 0

Bu-based 0 (0%) 19 (58%) 14(42%)

Bu + cyclophosphamide 0 9 12

Bu + Flu 0 10 2

GVHD prophylaxis

Cyclosporine-based 5(17%) 13 (39%) 0 (0%)

Cyclosporine + methotrexate 0 12 0

Cyclosporine + MMF 5 0 0

Cyclosporine + sirolimus 0 1 0

Tacrolimus-based 24 (83%) 20 (61%) 33 (100%)

Tacrolimus + methotrexate 0 17 31

Tacrolimus + MMF 24 0 0

Tacrolimus + sirolimus 0 3 2

CMV serostatus

Negative for both recipient and donor 5(17%) 7(21%) 3 (9%)

Positive for either recipient or donor 20 (69%) 19 (58%) 21 (64%)

Indeterminate/unknown 4(14%) 7(21%) 9 (27%)

Median follow-up period of survivors, 25.3 (3.7-57.5) 21.1 (4.2-46.3) 24.5 (3.7-47.9)

P Value

<.01 .44

UCB indicates unrelated cord blood; AML, acute myelogenous leukemia; CML, chronic myelogenous leukemia; MDS, myelodysplastic syndrome; MF, myelofibrosis; ALL, acute lymphoblastic leukemia; ML, malignant lymphoma; TBI, total body irradiation; Flu, fludarabine; Bu, busulfan; GVHD, graft-versus-host disease; MMF, mycophenolate mofetil; cyclosporine-based, cyclosporine with or without other agents; tacrolimus-based, tacrolimus with or without other agents; CMV, cytomegalovirus.

*No statistical test is provided due to small sample size.

grafts was 5.2 (range, 1.9-11; n = 32) x 106/kgand 7.5 (range, 2.4-9.7; n = 32) x 106/kg, respectively.

Immune Recovery

Because there were no significant differences in the kinetics of immune recovery and PFS between MSD and MUD recipients (Supplemental Figure 1), data on immune recovery of MSD and MUD recipients were combined and then compared with those of UCB recipients (Figure 1). The absolute lymphocyte count was lower in the UCB recipients at 1.5 months

after transplantation but reached the same level as MSD/MUD recipients by 3 months after transplantation. The number of CD31, CD41, and CD81 cells was significantly lower in the UCB recipients at 1.5 and 3 months after transplantation. This trend continued at the 6-month time point, but the difference was no longer statistically significant. At 12 months after transplantation, there was no detectable difference in CD31, CD41, and CD81 T cell counts in the UCB recipients and the MSD/MUD recipients. Recovery of B cells was highly variable in the UCB recipients. Overall, B cell recovery was faster in the UCB

Figure 1. Sequential changes of immune cell populations after transplantation. Black line shows matched sibling donor/matched unrelated donor (MSD/ MUD) recipients, and dotted line shows umbilical cord blood (UCB) recipients. The median values are shown as dots, and the ends of the whiskers indicate the 25% and 75% percentile values. Available median and 5%/95% percentiles of healthy adults are shown in dotted and solid horizontal lines [44]. RTE, recent thymic emigrant; T-reg, regulatory T cell; CTL, cytotoxic T lymphocyte; DC, dendritic cells.

recipients than the MSD/MUD recipients at 6 months in the UCB recipients at 3, 6, and 12 months after after transplantation, but this difference was lost by 12 transplantation. Recent thymic emigrant (naïve months. The NK cell counts were significantly higher CD4+ T cells with CD62L expression) and regulatory

MSD/ MUD

Pre 3 6 12

Months after transplantation P=. 04 p=. 09 />=.86 P=.87

Figure 2. Sequential changes in TCR rearrangement excision DNA circles (TRECs) before and after transplantation.

T cell populations (CD4+CD25+CD62L+) were significantly lower in the UCB recipient at 1.5, 3, and 6 months after transplantation. Cytotoxic T cell (CD8+CD57 + CD28-) and activated T cell (CD8 +HLA DR+) counts were lower in the UCB recipients at 1.5 and 3 months after transplantation. There was no significant difference in the plasmacy-toid dendritic cell counts, whereas the myeloid dendritic cell counts were higher in the UCB recipients at 1.5 months after transplantation. The number of NKT cells was significantly lower in UCB recipients throughout the period of observation.

TREC and TCR-b Repertoire

To further evaluate thymic-dependent T cell recovery, we measured TREC levels for 11 UCB and 21 MSD/MUD recipients. TREC levels were lower in the UCB recipients at 3 months after transplantation but comparable by the 6-month time point. TREC levels were uniformly low regardless of donor type, even at 12 months after transplantation (Figure 2). The median TREC level per 105 CD3 + T cells for the UCB and MSD/MUD recipients was 80 (range, 0-40; n = 9) and 415 (range, 0-4460; n = 20; P = .04) pretransplantation, 62 (range,

0-482; n = 10) and 209 (range, 0-4,680; n = 20; P = .09) at 3 months posttransplantation, 414 (range, 0-14,740; n = 11) and 232 (range, 0-4,200; n = 21; P = .86) at 6 months posttransplantation, and 517 (range, 14-2,400; n = 10) and 244 (range, 0-6,900; n = 19; P = .87) at 12 months posttransplantation, respectively. TCR diversity was assessed via survey-level TCR-ß sequencing on a subset of 10 patients (MSD, n = 3; MUD, n = 3; UCB, n = 4) who demonstrated comparable levels of TREC-positive cell recovery at 12 months (Table 2). Representative profiles of TCR Vb gene usage in peripheral blood T cells from recipients of MSD, MUD, UCB, and a healthy control are shown in Figure 3. TCR diversity (Entropy value; healthy control, 11.95) in the UCB recipients was comparable to that of the MSD/MUD recipients (average [SD] of entropy value; UCB, 9.33 6 3.85; MSD/MUD, 7.71 6 2.26; P = .47).

GVHD and Corticosteroid Exposure

To thoroughly assess the potential confounding effect of GVHD on posttransplantation immune recovery, we compared the cumulative incidence of grade II to IV and grade III to IV aGVHD and cGVHD (Figure 4). The incidence of grade II to IV aGVHD was significantly higher among the UCB recipients compared with the MSD/MUD recipients (0.66 [95% CI, 0.45-0.80] vs 0.38 [95% CI, 0.26-0.50, respectively]; Gray test, P = .006). The incidence of grade III to IV aGHVD was also higher in the UCB vs MSD/MUD recipients (0.28 [95% CI, 0.13-0.45] vs 0.09 [95% CI, 0.04-0.18, respectively]; Gray test, P = .018). Conversely, there was no significant difference in the incidence of cGVHD at 1 year between the UCB and MSD/MUD recipients (0.48 [95% CI, 0.29-0.65] vs 0.37 [95% CI, 0.25-0.49, respectively]; Gray test, P = .128). Because the persistence and treatment responsiveness of GVHD may differ depending on graft source, we assessed cumulative corticosteroid exposure (mg/kg) from 0 to 3, 6, or

Table 2. TCR Repertoire

Entropy*

Donor Type TREC (100,000 CD3+ cells) Productive Total Productive Uniques Value Ave. (±SD) P Value

MSD I 2140 7IISI4 10500 II.B4 9.33 (±3.BS) ref.

MSD 2 1046 4BS 15 3.02

MSD 3 1970 66S3 158 6.02

MUD I 4080 633BS0 7532 II.27

MUD 2 1262 493739 11957 II.90

MUD 3 1982 S47B60 13300 II.93

UCB I 2400 42S26 467 7.49 7.7I (±2.26) .47

UCB 2 784 SI9744 9128 I0.6I

UCB 3 436 92930 1981 S.I0

UCB 4 598 I74762 1445 7.62

MSD indicates matched sibling donor; MUD, matched unrelated donor; UCB, umbilical cord blood; Ave., average; ref., reference.

*Entropy is a measure of the uniformity of the frequency distribution of a TCR-b repertoire. Monoclonal or oligoclonal samples have low entropy, and

polyclonal highly diverse samples have an entropy just under log2 (No. uniques). The value of Entropy in a healthy control was 11.95.

Figure 3. Representative profiles of TCRVb gene usage in peripheral blood T cells from recipients of matched sibling donor (MSD) (A), matched unrelated donor (MUD) (B), umbilical cord blood (UCB) transplantation (C), and healthy control (D).

12 months after transplantation (Table 3). Consistent with the observed differences in clinical GVHD, the cumulative corticosteroid exposure at 3 months and 6 months after transplantation was significantly higher in the UCB recipients than in the MSD/MUD recipients. However, at 12 months after transplantation, there was no difference in cumulative corticosteroid exposure between the 2 groups. We also evaluated the cumulative corticosteroid exposure only for those who received corticosteroid treatment for GVHD. The cumulative corticosteroid exposure at 3, 6, or 12 months was not statistically different between the 3 groups, suggesting treatment response to GVHD was similar regardless of the donor type (Table 3).

We then evaluated the impact of grade II to IV and III to IV aGVHD on immune recovery at 3, 6, and 12 months after transplantation. We found that grade III to IV aGVHD (but not grade II to IV) significantly delayed the recovery of several immune cell populations at 3 months after transplantation (data not shown). Grade II to IV or III to IV aGVHD did not have any impact on immune recovery at 6 and 12 months after transplantation. Therefore, we performed an additional analysis in which we compared the immune recovery of the UCB group with that of the MSD/ MUD group in patients with grade 0 to I vs grade II to IV aGVHD or patients with grade 0 to II vs grade III to IV aGVHD (Table 4). Regardless of the presence of grade II to IV aGVHD, immune cell recovery other than B or NK cells was slower in the UCB group as compared with the MSD/MUD group. Among patients with grade III to IV aGVHD, median values of immune cell populations were lower in the UCB group than in the MSD/MUD group, although it was not significant partly due to the small sample size and partly due to the impact of grade III to IV aGVHD on immune cell recovery.

We additionally attempted to identify differences in the number of specific lymphocyte populations in those who did and did not develop cGVHD. We did not find any significant difference in these 2 groups for each immune cell population (data not shown).

CMV Reactivation and Disease

The cumulative incidence of CMV reactivation among patients at risk of CMV reactivation (serostatus; positive for either recipient or donor) was 0.84 (95% CI, 0.55-0.95) and 0.53 (95% CI, 0.36-0.67) in the UCB and MSD/MUD recipients, respectively (Gray test, P = .046; Figure 5), which corresponded with delayed recovery of T cells in the UCB recipients. The cumulative incidence of CMV diseases was 0.21 (0.07-0.41) and 0.03 (0.002-0.11) in the UCB and MSD/MUD recipients, respectively (Gray test, P = .019). All cases of CMV disease involved the intestinal tract, and none of the patients died from CMV disease. To exclude the effect of aGVHD on CMV reactivation and disease, we further evaluated the cumulative incidence of CMV in the UCB and MSD/MUD recipients according to the presence of grade II to IV aGVHD. The incidence of CMV reactivation and disease was consistently higher in the UCB group compared to the MSD/MUD group (CMV reactivation; grade 0-I aGVHD, 57% vs 36%, P = .574; grade II to IV aGVHD, 100% vs 72%, P = .169; CMV disease, grade 0 to I aGVHD, 14% vs 0%, P = .076; grade II to IVaGVHD, 25% vs 6%, P = .137), although these differences were not statistically significant due to the small sample size in each stratified category.

Because the kinetics of posttransplantation immune recovery is expected to significantly affect

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Figure 4. Cumulative incidence of grade II to IV (A) and grade III to IV (B) acute graft-versus-host disease (aGVHD) and chronic graft-versus-host disease (cGVHD) (C) after transplantation. Black line shows umbilical cord blood (UCB) recipients, and dotted line shows matched sibling donor/matched unrelated donor (MSD/MUD) recipients.

TRM and relapse, we compared PFS and TRM by graft type for all consecutive patients (n = 146) who underwent HCT at our center, and met the predefined eligibility criteria for this study. PFS at 1 year for UCB, MSD, and MUD recipients was 0.59 (95% CI, 0.440.72), 0.49 (95% CI, 0.34-0.62), and 0.56 (95% CI, 0.40-0.69), respectively, without significant difference between the 3 groups (log-rank test; P = .581; Figure 6A). Cumulative incidence of TRM at 1 year for UCB, MSD, and MUD recipients was 0.28 (95% CI, 0.16-0.41), 0.10 (95% CI, 0.04-0.20), and 0.16 (95% CI, 0.07-0.28), respectively (Gray test, P = .030). Causes of treatment-related death within 1 year after transplantation are shown in Table 5. We then compared PFS among the patients in whom immune reconstitution was assessed. This select group of patients survived at least 3 months after transplantation in order to be evaluable for immune recovery. There continued to be no statistical difference in PFS in UCB, MSD, and MUD recipients when the analysis included both standard-risk and high-risk patients (PFS at 1 year; 0.85; 95% CI, 0.64-0.94; 0.65 95% CI, 0.46-0.79; and 0.68; 95% CI, 0.49-0.82 respectively; log-rank test, P = .095; n = 95 Figure 6B) or when the analysis was limited to patients with standard-risk hematological malignancies (PFS at 1 year; 0.81; 95% CI, 0.57-0.92; 0.67; 95% CI, 0.44-0.82; and 0.76; 95% CI, 0.55-0.89, respectively; log-rank test, P = .357; n = 76; Figure 6C).

To assess the impact of recovery of specific lymphocyte subsets on PFS, we tested the various immune cell populations at 3 months after transplantation and other clinical factors on their ability to predict PFS using a 3-month landmark analysis among evaluable 69 patients (regardless of donor type) with standard-risk hematological malignancies. Patient characteristics were not associated with PFS in the univariate analysis. In the bivariate analysis controlling for donor type, higher numbers of T cells (P = .016), regulatory T cell (Treg) (P = .014), cytotoxic T lymphocyte (CTL) (P = .041), and myeloid DC (P = .028) were significantly associated with improved PFS (Table 6). In the MSD/MUD group, the myeloid DC subset

Table 3. Comparison of Cumulative Corticosteroid Dose

Corticosteroid Exposure No. UCB Median AUC (Range) No. MSD/MUD Median AUC (Range) P Value

For all patients

0-3 months 29 41.8 (0-247) 66 0 (0-285) .03

0-6 months 26 59 (0-285) 49 0 (0-286) <.01

0-12 months 21 96 (0-301) 36 74 (0-382) .13

For patients who received

corticosteroids

0-3 months 18 60 (24-247) 25 64(10-285) .65

0-6 months 23 78 (24-285) 31 78(10-286) .43

0-12 months 23 109 (24-301) 40 106 (19-382) .96

UCB indicates umbilical cord blood; MSD, matched sibling donor; MUD, matched unrelated donor; AUC, area under the curve.

Table 4. Recovery of Immune Cell Populations According to the Grade of aGVHD

MSD/MUD Median (Range) at 3 Months UCB Median (Range) at 3 Months P Value

Grade 0-I aGVHD n 5 41 n 5 10

Absolute lymphocyte counts 832 (35-3,359) 1297 (481-5,275) .02

CD3+ T cells 473 (13-2,714) 306 (25-2,986) .30

CD4+ T cells 233 (82-712) 134 (21-743) .l3

CD8+ T cells 189 (37-1,734) 33 (2-2,240) .05

B cells (CDI9+) 54 (0-496) 663 (0-1,287) <.0l

NK cells (CDI6+/CD56+) 153 (21-1,203) 373 (223-1,049) <.0l

CD4+CD45RA+CD62L+ cells (RTE) 16 (4-333) l (0-20) <.0l

CD4+CD25+CD62L+ cells (Treg) 49 (18-197) 30 (7-89) <.0l

CD8+CD57+CD28— cells (CTL) 24(1-902) 3 (0-291) .22

CD8+HLA-DR+ cells (activated T cells) 53 (5-919) 11 (0-1,702) .28

CDI23 —CDIIc+ cells (myeloid DC) 4(0-31) 8(2-18) <.0l

CDI23+CDIIc— cells (plasmacytoid DC) 7 (0-39) l2 (5-24) .05

CD3+CDI6+CD56+ cells (NKT cells) 35 (3-424) 5 (0-62) <.0l

Grade 0-II aGVHD n 5 60 n 5 2l

Absolute lymphocyte counts 837 (35-3,359) 911 (310-5,275) .48

CD3+ T cells 529 (l3-2,74l) 249 (3-2,986) <.0l

CD4+ T cells 242 (78-812) l3l (2-743) <.0l

CD8+ T cells 2l9 (37-2,262) 32(1-2,240) <.0l

B cells (CDI9+) 35 (0-496) 104(0-1,287) .0l

NK cells (CDI6+/CD56+) 160 (21-1,203) 360 (179-1,049) <.0l

CD4+CD45RA+CD62L+ cells (RTE) l5 (2-333) 5 (0-25) <.0l

CD4+CD25+CD62L+ cells (Treg) 53 (11-197) 28(0-149) <.0l

CD8+CD57+CD28— cells (CTL) 28(1-902) 3 (0-29l) .0l

CD8+HLA-DR+ cells (activated T cells) 64 (5-1,923) 13 (0-1,702) .02

CDI23 —CDIIc+ cells (myeloid DC) 3(0-31) 6 (0-21) <.0l

CDI23+CDIIc— cells (plasmacytoid DC) 7 (0-39) l0 (3-25) .06

CD3+CDI6+CD56+ cells (NKT cells) 37 (3-424) 5 (0-62) <.0l

Grade II-IVaGVHD n 5 25 n 5 l9

Absolute lymphocyte counts 817(108-2,879) 478 (130-6,434) .l3

CD3+ T cells 608 (82-2,741) l3l (3-2,539) <.0l

CD4+ T cells 253 (78-59l) 59 (2-1,194) <.0l

CD8+ T cells 329 (50-2,262) 32 (l-l,29l) <.0l

B cells (CDI9+) l0 (0-240) 20(0-781) .77

NK cells (CDI6+/CD56+) 160(15-422) 3l7 (57-2,686) .0l

CD4+CD45RA+CD62L+ cells (RTE) 13 (0-170) 6 (0-25) .09

CD4+CD25+CD62L+ cells (Treg) 54(11-207) 25 (0-l49) .02

CD8+CD57+CD28— cells (CTL) 33 (4-362) l (0-l03) <.0l

CD8+HLA-DR+ cells (activated T cells) 104(9-1,922) 9 (0-l,226) .0l

CDI23 —CDIIc+ cells (myeloid DC) 1 (0-16) 3 (0-46) .65

CDI23+CDIIc— cells (plasmacytoid DC) 5 (0-36) 9 (0-80) .77

CD3+CDI6+CD56+ cells (NKT cells) 43 (5-157) 5 (0-l24) <.0l

Grade III-IV aGVHD n56 n 5 8

Absolute lymphocyte counts 550(108-2,024) 348 (l30-6,434) l.00

CD3+ T cells 305 (82-1,518) 65 (48-2,539) .37

CD4+ T cells 239 (85-591) 5l (9-l,l94) .4l

CD8+ T cells l79 (50-852) 30 (l-l,29l) .85

B cells (CDI9+) 9 (0-240) 0 (0-78l) l.00

NK cells (CDI6+/CD56+) 121 (l5-357) l94 (57-2,686) l.00

CD4+CD45RA+CD62L+ cells (RTE) l5 (0-59) 6 (0-24) l.00

CD4+CD25+CD62L+ cells (Treg) 47 (27-207) 2l (0-72) .28

CD8+CD57+CD28— cells (CTL) 7 (4-40) l (0-77) .84

CD8+HLA-DR+ cells (activated T cells) 43 (13-417) 2 (0-l,226) l.00

CDI23 —CDIIc+ cells (myeloid DC) 1 (0-16) 0 (0-46) l.00

CDI23+CDIIc— cells (plasmacytoid DC) 5 (3-36) 6 (0-80) l.00

CD3+CDI6+CD56+ cells (NKT cells) 41 (5-101) 7(2-l24) .99

aGVHD indicates acute graft-versus-host disease; MSD, matched sibling donor; MUD, matched unrelated donor; UCB, umbilical cord blood; NK, natural killer; RTE, recent thymic emigrant; Treg, regulatory T cell; CTL, cytotoxic T lymphocyte; DC, dendritic cell; NKT, natural killer T cells.

was the only significant variable (hazard ratio 4.05; 95% CI, 1.13-14.60; P = .032; Table 6).

DISCUSSION

The past 10 years have brought great strides toward improvement in the outcome of UCB transplantation

in adult patients [28-31]. Progression-free and overall survival rates now approach that of HCT from matched adult donors [32,33]. We, therefore, found it to be an opportune time to perform a comprehensive comparison of immune reconstitution in adult recipients after matched sibling, matched unrelated, and UCB transplantations. We found that (1) recovery of critical T cell subsets in the UCB

P = .046 (Gray's test)

at о с

at ■g

'о с

0 1.5 3 4.5 6

Months after transplantation

- UCB (n = 18)

--■ MSD/MUD (n = 40)

Figure 5. Cumulative incidence of cytomegalovirus (CMV) reactivation after transplantation. Black line shows umbilical cord blood (UCB) recipients, and dotted line shows matched sibling donor/matched unrelated donor (MSD/MUD) recipients.

recipients was delayed but reached levels comparable to recipients of MSD/MUD transplantation by 12 months after transplantation, (2) NK and B cell recovery was more rapid in UCB recipients, (3) there was no significant difference in frequency of recent thymic emigrant as measured by CD3+ T cells containing TRECs, and (4) the T cell repertoire was comparably diversified in the UCB and MSD/MUD recipients at 12 months after transplantation. Finally, we confirm the finding of others that the PFS between recipients of UCB and MSD/MUD HCT is comparable.

The recovery of nearly all the critical T cell subsets was substantially delayed in the UCB group until 3 to 6 months after transplantation, exposing the patients to an increased risk of viral infection. In fact, the incidence of CMV reactivation reached a plateau at 2 months after MSD/MUD transplantation, whereas the incidence continuously increased until 6 months after UCB transplantation. This translated into a significant difference in the incidence of CMV reactivation between the 2 groups. This prolonged period of vulnerability in UCB recipients has been described by others [13,14,34]. However, quantitative differences in T cell subsets were largely erased by 1 year after transplantation. The kinetics and degree of immune reconstitution observed in our cohort of UCB transplantation recipients compares favorably to an earlier report by Komanduri et al. [8] who found that the number of CD4+ and CD8 + T cells was very low at 6 months after transplantation and remains so even at the 1-year time-point. The likely explanation for this difference is that our UCB recipients did not receive ATG as part of the preparative regimen. Our findings are similar to those reported recently by Jacobson et al. [14] who compared kinetics of T cell, B cell, and NK cell recovery in recipients of dual UCB and MUD transplantation after nonmyeloabla-tive conditioning. Our study focuses on HCT recipi-

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jä о 0.75

0.50 ■

S s 0.25 e s 0.00 i

P = .5S1 (log-rank test)

З 6 12 1S 24 Months after transplantation

Number at risk

- UCB 51

MSD 50 MUD 45

38 З1 25

38 27 19

40 2S 20

17 15 1З

14 11 12

о 0.75

P = .095 (log-rank test)

З 6 12 1S 24 Months after transplantation

Number at risk

— UCB 29 --- MSD ЗЗ MUD ЗЗ

££ 1.00

29 26 ЗЗ 24 ЗЗ 25

22 17 19

15 14 12

12 10 12

o 0.75

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3 8 0.25

S 2 0.00 i

Number at risk

— UCB 25 MSD 25 MUD 26

P = .З57 (log-rank test)

З 6 12 1S 24 Months after transplantation

1S 12 1S

1З 11 11

10 S 10

Figure 6. Progression-free survival (PFS) after transplantation for all consecutive patients undergoing hematopoietic cell transplantation (HCT) during the study period (A) and patients who survived at least 3 months without death or relapse after transplantation (B) all patients, and (C) standard-risk patients. Black line shows umbilical cord blood (UCB) recipients, dotted line shows matched sibling donor (MSD) recipients, and gray line shows matched unrelated donor (MUD) recipients.

ents after myeloablative conditioning and extends the comparison to include posttransplantation thymic function as well as TCR diversity.

Quantification of TRECs, which are derived from RTE, has been used as a surrogate marker for thymic-dependent T cell maturation. Early recovery of thymopoietic function after UCB transplantation is a critical determinant of TRM and morbidity [13]. Previous studies have described highly variable but generally slow recovery of thymic function as determined by the presence of peripheral blood TREC after UCB transplantation [7-9,13]. In order to assess the

Table 5. Causes of Treatment-Related Death within 1 Year after Transplantation

UCB MSD MUD

Graft failure 1 (7%) 0 0

GVHD 1 (7%) 0 0

Infection 8 (57°%) 1 (20%) 4 (57%)

Organ failure 3(21°%) 2 (40%) 3 (43%)

Other 1 (7°%) 2 (40%) 0

Total 14 5 7

UCB indicates umbilical cord blood; MSD, matched sibling donor; MUD, matched unrelated donor; GVHD, graft-versus-host disease.

impact of graft source on the thymic-dependent pathway of cellular immune reconstitution, we compared TREC recovery in our 2 cohorts. In contrast to other studies, we assayed TREC frequency from DNA isolated from a purified population of CD3 + T cells. Although the number of TRECs tended to be lower in the UCB group both before and 3 months after transplantation, it was not significantly different at 6 and 12 months after transplantation, mimicking the trend seen in quantitative T cell subset analysis. One explanation for lower TREC values in the UCB group may be differences in prior cytotoxic therapy resulting in thymic damage. Indeed, the UCB group was more heavily pretreated with only 22% of acute leukemia patients receiving transplantation in first remission compared to 51% in the MSD/MUD group. It should be noted that the number of TRECs at 1 year after transplantation remained well below normal regardless of donor source indicating ongoing impairment of thymus-dependent T cell recovery, which is consistent with a previous study analyzing mostly pediatric patients [35]. Komanduri et al. [8] and Escalon et al. [36] demonstrate a complete block of thymopoiesis during the first year after UCB transplantation, which is in stark contrast to what was observed after HCT from autologous or adult matched donor transplantation. However, the observed differences may be related to low total numbers of TREC-containing lymphoid progenitors passively transferred with the stem cell graft or use of ATG in the transplantation preparative regimen. We also analyzed TCR diversity in a subset

of 10 patients 1 year after HCT with comparable T cell recovery, as determined by quantitative T cell subset analysis and TREC output. We were interested to know whether the low but detectable output of RTE in UCB transplantation recipients was capable of equalizing TCR diversity of the adult donor recipients who benefit from homeostatic expansion of passively transferred polyclonal memory T cells. Despite this advantage, we found that the TCR diversity in UCB recipients was comparable to that of the matched adult donor recipients.

It is of interest to note that despite the observed delay in quantitative T cell recovery in recipients of UCB transplantation, we did not observe differences in PFS compared with the recipients of matched adult donor transplantation. This can be explained, in part, by the improvement in supportive care. However, it is also possible that more prompt recovery of NK cells and B cells in UCB recipients may compensate for early T cell deficits, although rapid recovery of both of these cell types may partly be due to a compensatory response to the profound T lymphopenia [37,38]. Tanaka et al. [39] observed a more rapid expansion of NK cells after UCB compared to PBSC transplantation. The investigators found that UCB-derived mature (CD16+, CD56dim) and immature (CD16-, CD56+) populations of NK cells exert potent cytotoxic activity against tumor cell lines and exhibit decreased expression of inhibitory NKG2A and increased expression of stimulatory NKG2C as compared to NK cells that emerge after matched-related donor transplantation.

Patient age [11,12], incidence and severity of GVHD [40], intensity of the conditioning regimen [7,41], and T cell depletion of the donor graft [42] are all significant parameters that affect the pace and quality of immune recovery after HCT. Of all these parameters, patient age and the incidence of aGVHD differed among the 3 cohorts analyzed in this study. The younger mean age of UCB recipients is unlikely to be a significant influence on immune recovery because all recipients were over age 19, which is reported to be an age that marks significant decline of thymic function [12]. The higher observed incidence of acute grade II to IV and grade III to IV GVHD in the

Table 6. Improved PFS with Recovery of Specific Lymphocyte Subsets among Standard-Risk Patients

Total (n = 69) MSD/MUD Group (n = 47)

Variables Comparison HR (95% CI) P Value HR (95% CI) P Value

T cells (CD3+) High vs low 3.33 (1.26-8.84) .016 1.68 (0.61-4.64) .319

Regulatory T cells (CD4+CD25+CD62L+) High vs low 3.84 (1.31-11.30) .014 2.72 (0.85-8.7l) .093

Cytotoxic T cells (CD8+CD57+CD28-) High vs low 3.01 (l.05-8.64) .041 2.99 (0.94-9.58) .065

Myeloid dendritic cells (CDl23-CDllc+) High vs low 3.66 (l.l5-ll.67) .028 4.05 (l.l3-l4.60) .032

PFS indicates progression-free survival; MSD, matched sibling donor; MUD, matched unrelated donor; HR, hazard ratio; CI, confidence interval. Standard-risk patients are divided into the high vs lowgroup according to the median value of each lymphocyte subset. Median value (cells/mL) for T cells, regulatory T cells, cytotoxic T cells, and myeloid dendritic cells are 439,43.9, l9.0, and 8.8 for all patients, respectively, and 505,57.8,23.5, and 7.2 for the MSD/MUD group, respectively.

Only significant variables analyzed among the standard-risk patients were shown.

dual-UCB group compared to the MSD/MUD group deserves further discussion. Grade III to IV aGVHD contributed to delayed immune reconstitution at 3 months after transplantation in this cohort. Therefore, it is possible that the delay in immune reconstitution at 3 months after UCB transplantation was the result of a high incidence of aGVHD in the UCB group, although a similar pattern of delayed immune recovery in the UCB recipients was observed regardless of how aGVHD patients were grouped (0-I, 0-II, II-IV, or III-IV). The high incidence of aGVHD in our cohort compared with previous UCB reports may, in part, be due to use of a conditioning regimen that does not contain ATG.

Any study comparing immune reconstitution after HCT is subject to a "survivor bias'' such that the patients with the most profound impairment in immune recovery die from treatment-related complications and are thus not evaluable for comparison. Although a survivor bias cannot be completely excluded from this study, there are 2 factors that suggest it does not exert a major influence on the findings of this study. First, we did not observe any significant difference in PFS in the 3 cohorts of patients assessed in this study (Figure 6). Second, the incidence of infection-related deaths was low in both treatment cohorts and, therefore, unlikely to be a contributing factor to the reported observations (data not shown). An additional limitation of this study arises from the fact that due to technical constraints, we report TREC analysis on a subset of evaluable patients. We cannot rule out the possibility that elimination of these subjects resulted in a biased analysis of this portion of the study.

In conclusion, when compared to recipients of matched sibling and MUD HCT recipients, UCB transplantation recipients have slower quantitative recovery of T lineage immune cell populations in the first 6 months, but these differences are erased by 1 year after transplantation. NK and B cell reconstitution is more rapid in UCB recipients.

ACKNOWLEDGMENTS

Financial disclosure: This work was supported in part by the National Cancer Institute (NIH) 5P01-CA047741-18 (Mitchell E. Horwitz, Nelson J. Chao) and a Grant-in-Aid for JSPS Fellows (Junya Kanda). Authors have no relevant financial relationship to disclose.

Junya Kanda is a Research Fellow of the JSPS. The sjTREC analysis were performed by Jeffrey Hale in the Duke Human Vaccine Institute Immune Reconstitution and Biomarker Shared Resource Facility.

Author statement: Junya Kanda and Lun-Wei Chiou equally contributed to this work. Contributions: Mitchell E. Horwitz designed the research and

organized the project; Junya Kanda, Lun-Wei Chiou, John Andrew Livingston, and Mitchell E. Horwitz reviewed data, analyzed data, interpreted data, and wrote the article; Paul Szabolcs reviewed data and interpreted data; Gregory D. Sempowski and Jeffrey Hale analyzed data and interpreted data; Junya Kanda, Gloria Broadwater, and Donna Niedzwiecki performed statistical analysis; Nelson J. Chao interpreted data. All authors reviewed and approved the final manuscript.

A part of this work was presented as an abstract at the 51th Annual Meeting of the American Society of Hematology, Orlando, FL, December 5-8, 2010 [43].

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Supplementary Figure1. Sequential changes of immune cell populations after transplantation Black line shows matched sibling donor (MSD) recipients, and dotted line shows matched unrelated donor (MUD) recipients. Abbreviations: RTE, recent thymic emigrant; T-reg, regulatory T cell; CTL, cytotoxic T cell. The median values are shown as dots, and the ends of the whiskers indicate the 25% and 75% percentile values. Median and 5%/ 95% percentiles of healthy adults are shown in dotted and solid horizontal lines [44].