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Background: Lymphocyte neogenesis from primary lymphoid organs is essential for a successful reconstitution of immunity after allogeneic hematopoietic stem cell transplantation (HSCT). This single-center retrospective study aimed to evaluate T cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC) as surrogate markers for T and B cell recovery, as predictors for transplantation-related outcomes in adult acute myeloid leukemia (AML) patients., Methods: Ninety adult patients diagnosed with AML and treated with HSCT between 2010 and 2015 were included in the study. TREC and KREC levels were measured by quantitative PCR at 1, 3, 6, and 12 months after transplantation., Results: Overall, excision circle levels increased between 3 and 6 months post-HSCT for TREC (p = 0.005) and 1 and 3 months for KREC (p = 0.0007). In a landmark survival analysis at 12 months post-HSCT, TREC levels were associated with superior overall survival (HR: 0.52, 95% CI: 0.34 - 0.81, p = 0.004). The incidence of viral infections within the first 100 days after transplantation was associated with lower TREC levels at 6 months (p = 0.0002). CMV reactivation was likewise associated with lower TREC levels at 6 months (p = 0.02) post-HSCT. KREC levels were not associated with clinical outcomes in statistical analyzes., Conclusions: Results from the present study indicate that TREC measurement could be considered as part of the post-HSCT monitoring to identify AML patients with inferior survival after transplantation. Further prospective studies are warranted to validate these findings., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Söderström, Vonlanthen, Jönsson-Videsäter, Mielke, Lindahl, Törlén and Uhlin.)

Allogeneic Hematopoietic stem cell transplantation (allo-HCT) is a curative platform for several hematological diseases. Despite its therapeutic benefits, the profound immunodeficiency associated with the transplant procedure remains a major challenge that renders patients vulnerable to several complications. Today, It is well established that a rapid and efficient immune reconstitution, particularly of the T cell compartment is pivotal to both a short-term and a long-term favorable outcome. T cells expressing a TCR heterodimer comprised of gamma (γ) and delta (δ) chains have received particular attention in allo-HCT setting, as a large body of evidence has indicated that γδ T cells can exert favorable potent anti-tumor effects without inducing severe graft versus host disease (GVHD). However, despite their potential role in allo-HCT, studies investigating their detailed reconstitution in patients after allo-HCT are scarce. In this review we aim to shed lights on the current literature and understanding of γδ T cell reconstitution kinetics as well as the different transplant-related factors that may influence γδ reconstitution in allo-HCT. Furthermore, we will present data from available reports supporting a role of γδ cells and their subsets in patient outcome. Finally, we discuss the current and future strategies to develop γδ cell-based therapies to exploit the full immunotherapeutic potential of γδ cells in HCT setting., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Gaballa, Arruda and Uhlin.)

Hematopoietic stem cell transplantation (HSCT) is an effective treatment option for several malignant and non-malignant hematological diseases. The clinical outcome of this procedure relies to a large extent on optimal recovery of adaptive immunity. In this regard, the thymus plays a central role as the primary site for de novo generation of functional, diverse, and immunocompetent T-lymphocytes. The thymus is exquisitely sensitive to several insults during HSCT, including conditioning drugs, corticosteroids, infections, and graft-vs.-host disease. Impaired thymic recovery has been clearly associated with increased risk of opportunistic infections and poor clinical outcomes in HSCT recipients. Therefore, better understanding of thymic function can provide valuable information for improving HSCT outcomes. Recent data have shown that, besides gender and age, a specific single-nucleotide polymorphism affects thymopoiesis and may also influence thymic output post-HSCT, suggesting that the time of precision medicine of thymic function has arrived. Here, we review the current knowledge about thymic role in HSCT and the recent work of genetic control of human thymopoiesis. We also discuss different transplant-related factors that have been associated with impaired thymic recovery and the use of T-cell receptor excision circles (TREC) to assess thymic output, including its clinical significance. Finally, we present therapeutic strategies that could boost thymic recovery post-HSCT., (Copyright © 2020 Gaballa, Clave, Uhlin, Toubert and Arruda.)

Allogeneic hematopoietic stem cell transplantation (HSCT) using αβ T-/B-cell-depleted grafts recently emerged as a transplant strategy and highlighted the potential role of γδ T cells on HSCT outcomes. Our aim was to scrutinize available evidence of γδ T-cell impact on relapse, infections, survival, and acute graft-versus-host disease (aGVHD). We performed a systematic review and meta-analysis of studies assessing γδ T cells in HSCT. We searched PubMed, Web of Science, Scopus, and conference abstracts from inception to March 2019 for relevant studies. We included all studies that assessed γδ T cells associated with HSCT. Data were extracted independently by 2 investigators based on strict selection criteria. A random-effects model was used to pool outcomes across studies. Primary outcome was disease relapse. We also assessed infections, survival, and aGVHD incidence. The review was registered with PROSPERO (CRD42019133344). Our search returned 2412 studies, of which 11 (919 patients) were eligible for meta-analysis. Median follow-up was 30 months (interquartile range, 22-32). High γδ T-cell values after HSCT were associated with less disease relapse (risk ratio [RR], 0.58; 95% confidence interval [95% CI], 0.40-0.84; P = .004; I2 = 0%), fewer viral infections (RR, 0.59; 95% CI, 0.43-0.82; P = .002; I2 = 0%) and higher overall (HR, 0.28; 95% CI, 0.18-0.44; P < .00001; I2 = 0%) and disease-free survivals (HR 0.29; 95% CI, 0.18-0.48; P < .00001; I2 = 0%). We found no association between high γδ T-cell values and aGVHD incidence (RR, 0.72; 95% CI, 0.41-1.27; P = .26; I2 = 0%). In conclusion, high γδ T cells after HSCT is associated with a favorable clinical outcome but not with aGVHD development, suggesting that γδ T cells have a significant effect on the success of HSCT. This study was registered with PROSPERO as #CRD42019133344., (© 2019 by The American Society of Hematology.)

The impact of intra-graft T cells on the clinical outcome after allogeneic hematopoietic cell transplantation has been investigated. Most previous studies have focused on the role of αβ cells while γδ cells have received less attention. It has been an open question whether γδ cells are beneficial or not for patient outcome, especially with regards to graft versus host disease. In this study, graft composition of γδ cell subsets was analyzed and correlated to clinical outcome in 105 recipients who underwent allogeneic hematopoietic cell transplantation between 2013 and 2016. We demonstrate for the first time that grafts containing higher T-cell proportions of CD8 + γδ cells were associated with increased cumulative incidence of acute graft versus host disease grade II-III (50% vs 22.6%; P = 0.008). Additionally, graft T-cell frequency of CD27 + γδ cells was inversely correlated with relapse (P = 0.006) and CMV reactivation (P = 0.05). We conclude that clinical outcome after allogeneic hematopoietic cell transplantation is influenced by the proportions of distinct γδ cell subsets in the stem cell graft. We also provide evidence that CD8 + γδ cells are potentially alloreactive and may play a role in acute graft versus host disease. This study illustrates the importance of better understanding of the role of distinct subsets of γδ cells in allogeneic hematopoietic cell transplantation.

Background and Objectives: Mucositis is a common complication after allogeneic hematopoietic stem cell transplantation (HSCT), and is caused by a combination of conditioning-induced mucosal damage and severe neutropenia. The symptoms include oral and abdominal pain, inability to swallow food and fluids, and severe diarrhoea. Severe mucositis is associated with increased risk of Graft-versus-Host disease and infection. Granulocyte transfusions (GCX) could be a treatment option, and our objective was to study its feasibility and potential benefits., Material and Methods: This retrospective, single-centre study included 30 patients receiving GCX because of severe oral mucositis after HSCT during 2005-2017. Clinical outcome, response to GCX, change in opiate administration and adverse events were studied., Results: Twenty-seven patients received GCX from donors pre-treated with steroids and G-CSF, and three from donors pre-treated with steroids only. Overall response was 83% (24/29 evaluable patients). Fifteen patients reached a complete response. In 14 of 24 responders, a reduction of the administration of opiate pain relief was seen. In eight patients this reduction was ≥50% of the dose. Adverse events (AEs) were reported in 14 cases, and were mild to moderate, and well manageable with symptomatic treatment. No life-threatening or fatal AEs were recorded., Conclusions: These results indicate that GCX could be a safe and effective treatment for oral mucositis after HSCT with the potential to reduce the necessity of opiate analgesic treatment in this disorder. No severe AEs were seen in this study, but the risk for severe pulmonary AEs after GCX needs to be considered., (© 2019 International Society of Blood Transfusion.)

Background: Graft-versus-host disease (GVHD) and relapse remain majobstacles ftreatment success in allogeneic hematopoietic stem cell transplantation (HSCT). In the present study, we evaluated the immune cell profile of the graft to outcome after HSCT., Study Design and Method: Flow cytometry data of graft cell subsets [CD34 + , CD3 + , CD19 + , CD4 + , CD8 + , CD3-CD56 + CD16 + , CD4 + CD127 low CD25 high ] from G-CSF primed peripheral blood stem cell (PBSC) donors was collected retrospectively from 299 patients with hematological malignancies undergoing HSCT between 2006 and 2013. The association to overall survival, transplant-related mortality (TRM), GVHD and probability of relapse was analyzed. Patients outcome from HLA-identical sibling (Sib) (n = 97) and unrelated donors (URD) (n = 202) were analyzed separately as all URD patients received anti-thymocyte globulin (ATG)., Results: Five-year overall survival was similar in the two cohorts (68% (Sib) vs 65% (URD)). The relapse incidence was significantly lower in the Sib cohort (24% vs 35%, P = 0.04). Multivariate analysis in the URD group revealed an association between a higher CD8 + dose and less relapse (HR, 0.94; 95%CI, 0.90-0.98; P = 0.006) as well as an association between higher CD34 + dose and both higher TRM (HR, 1.09; 95%CI, 1.02-1.20; P = 0.02) and relapse (HR, 1.09; 95%CI, 1.01-1.17; P = 0.025). The Sib analysis showed an association between a higher graft CD19 + dose and more severe acute GVHD (HR, 1,09; 95%CI, 1.03-1.15; P = 0.003) and TRM (HR, 1.09; 95%CI, 1.01-1.17; P = 0.036). In addition, a higher CD4 + graft content was associated to an increased risk for chronic GVHD (HR, 1.02; 95%CI 1.00-1.04; P = 0.06)., Conclusion: These data indicate an importance of PBSC dongraft composition in patients with a hematological malignancy., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Lymphocyte reconstitution is pivotal for successful long-term outcome after allogeneic hematopoietic stem cell transplantation (HSCT), and conditioning regimen and post-transplantation immunosuppression are risk factors for prolonged immunodeficiency. Nevertheless, the effects of different immunosuppressive protocols on lymphocyte output and replicative capacity have not been investigated. Here we assessed T cell receptor excision circles (TREC), kappa-deleting recombination excision circles (KREC), and T cell telomere length (TL) as proxy markers for immune reconstitution in patients in a prospective randomized trial comparing graft-versus-host disease (GVHD) prophylaxis after transplantation (cyclosporine/methotrexate versus tacrolimus/sirolimus; n = 200). Results showed that medians of TREC, KREC, and TL were not significantly different between the prophylaxis groups at any assessment time point during follow-up (24 months), but the kinetics of TREC, KREC, and TL were significantly influenced by other transplantation-related factors. Older recipient age, the use of antithymocyte globulin before graft infusion, and use of peripheral blood stem cell grafts were associated with lower TREC levels, whereas acute GVHD transiently affected KREC levels. Patients with lymphocyte excision circle levels above the median at ≤6 months post-transplantation had reduced transplantation-related mortality and superior 5-year overall survival (P < .05). We noticed significant T cell telomere shortening in the patient population as a whole during follow-up. Our results suggest that lymphocyte reconstitution after transplantation is not altered by different immunosuppressive protocols. This study has been registered at ClinicalTrials.gov (identifier: NCT00993343)., (Copyright © 2019 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

Although the impact of donor graft composition on clinical outcomes after hematopoietic stem cell transplantation (HSCT) has been studied, little is known about the role of intragraft γδ TCR repertoire on clinical outcomes following HSCT. Using a high-throughput sequencing platform, we sought to analyze the TCR γ-chain (TRG) repertoire of γδ T cells within donor stem cell grafts and address its potential impact on clinical response in the corresponding patients. A total of 20 peripheral blood stem cell grafts were analyzed, and donors were classified as CMV +/- The respective acute myeloid leukemia recipients were followed for disease relapse and acute graft-versus-host disease (aGvHD) development post-HSCT. In all samples, TRG repertoire showed a reduced diversity and displayed overrepresented clones. This was more prominent in grafts from CMV + donors, which presented a more private repertoire, lower diversity, skewed distribution, and reduced usage of the V9-JP pairing. Grafts given to nonrelapse patients presented a more public repertoire and increased presence of long sequence clonotypes. Variable-joining gene segment usage was not associated with aGvHD development, but a higher usage of V2-JP1 pairing and lower usage of V4-J2/V5-J2/V8-JP2 were observed in grafts given to nonrelapse patients. Our work identified five private overrepresented and one public CDR3 sequence (CATWDGPYYKKLF) associated with CMV infection, in addition to 12 highly frequent public sequences present exclusively in grafts given to nonrelapse patients. Our findings show that, despite CMV infection reshaping the TRG repertoire, TRG composition is not associated with aGvHD development, and several public sequences are associated with clinical remission., (Copyright © 2019 by The American Association of Immunologists, Inc.)

Allogeneic hematopoietic stem cell transplantation (HSCT) is associated with several potentially lethal complications. Higher levels of CD3+ T-cells in the graft have been associated with increased risk of graft-versus-host disease (GVHD), but also beneficial graft-versus-leukemia effect and reduced infections. To tackle post-transplant complications, donor lymphocyte infusions have been used but with an increased risk of GVHD. To reduce this risk, we performed depletion of αβ T-cells and treated 12 patients post-HSCT suffering from infections and/or poor immune reconstitution. The αβ T-cell depleted cell products were characterized by flow cytometry. The median log depletion of αβ T-cells was -4.3 and the median yield of γδ T-cells was 73.5%. The median CD34+ cell dose was 4.4 × 10 6 /kg. All 12 patients were alive 3 months after infusion and after 1 year, two patients had died. No infusion-related side effects were reported and no severe acute GVHD (grade III-IV) developed in any patient post-infusion. Overall, 3 months after infusion 11 out of 12 patients had increased levels of platelets and/or granulocytes. In conclusion, we describe the use of αβ T-cell depleted products as stem cell boosters with encouraging results.

Acute graft-versus-host disease (aGVHD) is 1 of the main major complications of post-hematopoietic stem cell transplantation (HSCT). Identifying patients at risk of severe aGVHD may lead to earlier intervention and treatment, resulting in increased survival and a better quality of life. We aimed to identify biomarkers in donor grafts and patient plasma around the time of transplantation that might be predictive of aGVHD development. We build on our previously published methods by using multiplex assays and multicolor flow cytometry. We identified 5 easily assessable cellular markers in donor grafts that combined could potentially be used to calculate risk for severe aGVHD development. Most noteworthy are the T cell subsets expressing IL-7 receptor-α (CD127) and PD-1. Additionally, we identified a potential role for elevated tumor necrosis factor-α levels in both graft and patient before HSCT in development of aGVHD., (Copyright © 2017 The American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

Reconstitution of the adaptive immune system following allogeneic hematopoietic stem cell transplantation is crucial for beneficial outcome and is affected by several factors, such as GvHD and graft source. The impact of these factors on immune reconstitution has been thoroughly investigated during the early phase after transplantation. However, little is known about their long-term effect. Similarly, leukocyte telomere length (TL) shortening has been reported shortly after transplantation. Nevertheless, whether TL shortening continues in long-term aspect is still unsettled. Here, we assessed T-cell receptor excision circle (TREC), kappa deleting recombination excision circle (KREC) and leukocyte TL in recipients and donors several years post transplantation (median 17 years). Our analysis showed that, recipients who received bone marrow (BM) as the graft source have higher levels of both TREC and KREC. Also, chronic GvHD affected TREC levels and TL but not KREC levels. Finally, we show that recipient's TL was longer than respective donors in a group of young age recipients with high KREC levels. Our results suggest that BM can be beneficial for long-term adaptive immune recovery. We also present supporting evidence for recipient telomere homeostasis, especially in young age recipients, rather than telomere shortening.

HLA-C mismatch in unrelated donor's hematopoietic stem cell transplantation (HSCT) has been associated with poor patient outcome. However, the impact of HLA-C mismatch in the context of HSCT combined with in vivo T-cell depletion remains unclear. We therefore performed a single-center, retrospective analysis of the clinical outcome on patients with hematological malignancies treated with allo-HSCT, who underwent T-cell depletion. The majority of the patients (n=276) received a HLA-A, HLA-B, HLA-DRB1-matched graft that were either also HLA-C matched (n=260), or patients with the permissive HLA-C*03:03/03:04 mismatch (n=16), while the remaining patients (n=95) received a HLA-C-mismatched graft (excluding HLA-C*03:03/03:04 mismatches). We did not observe any significant differences between the HLA-C-matched patients (including the permissive HLA-C*03:03/03:04 mismatch) and the HLA-C-mismatched patients regarding cumulative proportion surviving, graft failure, relapse-free survival, relapse, or acute graft-versus-host disease. Our data suggest that in the context of high dose T lymphocyte-depleting agents, HLA-C matching is not essential for patients with hematological malignancies., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background and Objectives: Allogeneic hematopoietic stem cell transplantation (HSCT) is a routine clinical procedure performed to treat patients with haematological malignancies, primary immune deficiencies or metabolic disorders. Infections during lymphopenia after allogeneic HSCT are associated with high mortality and morbidity. Typical infectious agents are Epstein-Barr virus, cytomegalovirus, herpes simplex virus, varicella-zoster virus and fungi. The study aim was to evaluate whether measurement of the responses of antigen-specific T-cells, recognizing infectious pathogens would correlate to protective functions in the stem cell recipient post-transplant., Materials and Methods: Twenty-one grafts were analysed by flow cytometry and cells were stimulated in vitro with relevant infectious antigens, followed by evaluation of T-cell proliferation and cytokine production. Results were compared to the recipients' clinical records 1-year post-transplantation., Results: We show that an extensive repertoire of transferred antigen-specific T-cells from allogeneic donor grafts against infectious agents, involved in post-transplant infections, are linked to an absence of infectious complications for the recipient up-to 1-year post-transplant. The protective effect was associated with antigen-specific T-cell proliferation and IL-1β secretion., Conclusion: Our results suggest that assaying T-cell function before HSCT could determine individual risks for infectious complications and thus aid in clinical decision-making regarding prophylactic and pre-emptive anti-infective therapy., (© 2017 International Society of Blood Transfusion.)

Long-term stable mixed chimerism is a rare and poorly understood phenomenon post hematopoietic stem cell transplantation. This study aims to shed light on whether the two hematopoietic systems in patients with mixed chimerism remain functional. Additionally, we investigate possible immunologic differences in these individuals compared to patients with only donor derived immune cells. Patients with donor and mixed chimerism, at median 10 (5-16) years post-HSCT for non-malignant diseases, were assessed regarding clinical situation and immune system (phenotypical and functional). No difference in long-term outcome was seen in terms of general wellbeing, central phenotypic immune system features (e.g., differentiation status, CD4/CD8 ratio, B and NK-cell frequency) and antibody responses to immunizations. At a median of 10 years post transplantation, patients with mixed chimerism had significantly higher IgG3 and platelet levels. Additionally, these patients had higher NKT-cell levels (CD94+CD8+ and CD56+CD8+) than patients with donor chimerism. In depth phenotypic analysis of patients with mixed chimerism demonstrated recipient-derived fractions in most immune cell lineages (e.g., T-cell, B-cell and NK-cell subsets). Recipient cells were also capable of responding to mitogenic stimulation with production of several cytokines. In conclusion, long-term mixed chimerism did not negatively affect patient wellbeing and long-term outcome. Moreover, recipient-derived immunity may still be functional in these patients, suggesting an active state of tolerance and immunologic dependence on both hematopoietic systems.

Background . Graft-versus-host disease (GVHD) is a serious complication after allogeneic hematopoietic stem cell transplantation (HSCT). We designed a functional assay for assessment of individual risk for acute GVHD. Study Design and Methods . Blood samples were collected from patients and donors before HSCT. Two groups of seven patients each were selected, one in which individuals developed acute GVHD grades II-IV and one in which none showed any clinical signs of GVHD. Peripheral blood mononuclear cells (PBMCs) isolated from donors were incubated in mixed lymphocyte cultures (MLCs) with recipient PBMCs. The cells were characterized by flow cytometry before and after MLC. Results . Samples from donors in the GVHD group contained significantly lower frequencies of naïve γδ T-cells and T-cells expressing NK-cell markers CD56 and CD94. Donor samples in this group also exhibited lower frequencies of naïve CD95 + T-cells compared to controls. After MLC, there were dissimilarities in the CD4/CD8 T-cell ratio and frequency of CD69 + T-cells between the two patient groups, with the non-GVHD group showing higher frequencies of CD8 + and CD69 + T-cells. Conclusion . We conclude that a thorough flow cytometric analysis of donor cells for phenotype and allogeneic reactivity may be of value when assessing pretransplant risk for severe acute GVHD., Competing Interests: None of the authors has any potential financial conflict of interests related to this manuscript.

During more recent years only few studies have analyzed the effect of total nucleated cell (TNC) and CD34(+) cell dose in allogeneic hematopoietic stem cell transplantation (HSCT). A single-center analysis included 544 patients, 227 with a sibling donor and 317 with an unrelated donor. Most patients (n = 292) were treated with myeloablative conditioning, whereas the remaining patients (n = 252) received reduced-intensity conditioning. Bone marrow (BM) (n = 121) and peripheral blood stem cell (PBSC) grafts (n = 423) were analyzed separately. Median TNC and CD34(+) cell dose was 3.2 × 10(8)/kg versus 11.6 × 10(8)/kg in BM and 3.9 × 10(6)/kg versus 8.1 × 10(6)/kg in PBSC. In the BM group we found a higher TNC and CD34(+) cell dose was associated with a faster neutrophil engraftment (P < .001 and P = .02). In the PBSC group we found patients given a very high (≥11 × 10(6)/kg) CD34(+) cell dose had decreased rates of survival (P = .001) and increased relapse (P = .02). A high CD34(+) cell dose correlated with faster platelet engraftment (P < .01). In HSCT using PBSCs, the CD34(+) cell doses should be kept below 11 × 10(6)/kg but over 2.5 × 10(6)/kg., (Copyright © 2015 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

Background: Umbilical cord blood (UCB) is an alternative graft source for hematopoietic stem cell transplantation and has been shown to give results comparable to transplantation with other stem cell sources. Donor lymphocyte infusion (DLI) is an effective treatment for relapsed malignancies after hematopoietic stem cell transplantation. However, DLI is not available after UCB transplantation., Methods: In this study, in vitro-cultured T cells from the UCB graft were explored as an alternative to conventional DLI. The main aim was to study the safety of the cultured UCB T cells used as DLI because such cell preparations have not been used in this context previously. We also assessed potential benefits of the treatment., Results: The cultured UCB T cells (UCB DLI) were given to 4 patients with mixed chimerism (n = 2), minimal residual disease (n = 1) and graft failure (n = 1). No adverse reactions were seen at transfusion. Three of the patients did not show any signs of graft-versus-host disease (GVHD) after UCB DLI, but GVHD could not be excluded in the last patient. In the patient with minimal residual disease treated with UCB DLI, the malignant cell clone was detectable shortly before infusion but undetectable at treatment and for 3 months after infusion. In 1 patient with mixed chimerism, the percentage of recipient cells decreased in temporal association with UCB DLI treatment., Conclusions: We saw no certain adverse effects of treatment with UCB DLI. Events that could indicate possible benefits were seen but with no certain causal association with the treatment., (Copyright © 2014 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.)

In this retrospective study, 209 patients with malignant disease were analyzed for levels of T-cell receptor excision circles (TRECs) for the first 24 months after allogeneic stem cell transplantation. CD3(+) cells were separated by direct antibody-coupled magnetic beads, followed by DNA extraction according to a standard protocol. The δRec-ψJα signal joint TREC was measured with real-time quantitative PCR. Patients were grouped based on malignant disease: chronic myeloid leukemia, chronic lymphatic leukemia, acute myeloid leukemia (AML), acute lymphocytic leukemia (ALL), and myelodysplastic syndrome (MDS). Patients were further subdivided based on TREC levels below (low-TREC) or above (high-TREC) median at each time point. TREC levels were then correlated to relapse incidence and relapse-free survival (RFS). For patients with AML, low TREC levels 2 months post-transplantation were correlated to high relapse incidence at 5 years (P<0.05). In patients with chronic leukemia, high TREC levels were correlated with improved RFS (P<0.05). For patients with MDS, high TREC levels at 9 months post-transplantation were associated with higher RFS at 5 years (P<0.02) and lower relapse incidence (P<0.02). This study shows the potential use of TREC measurement in blood to predict relapse in patients with AML and MDS after allogeneic hematopoietic stem cell transplantation.

Introduction: Despite routine use of umbilical cord blood (CB) grafts as stem cell source for allogeneic stem cell transplantations, much remains unknown regarding their cell composition and correlation with clinical outcome., Methods: We analyzed material from 30 CB units used for allogeneic hematopoietic stem cell transplantation by multicolor flow cytometry. Phenotypic data were correlated with various clinical outcomes such as survival, graft-versus-host disease (GVHD), relapse, rejection, viral reactivation, and bacteremia., Results: We found that above-median frequencies of CD69+ T cells, naïve CD8+ T cells, and CD127+ B cells in the CB graft were each associated with significantly improved patient survival. Moreover, a statistically significant correlation was seen between higher levels of CD94+ T cells and herpes simplex virus and varicella zoster virus reactivation post transplantation. A similar correlation was seen for the frequency of CD95+ cells in total CD3+, as well as CD4+ and CD8+ T-cell subsets, and viral reactivation. Finally, a higher frequency of naïve CD8+ T cells was associated with the incidence of acute GVHD., Conclusion: Our study highlights the importance of further exploration of graft composition before CB transplantation as a tool for risk prediction., (© 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Allogeneic hematopoietic stem cell transplantation (HSCT) can be performed across the ABO blood group barrier. The impact of ABO incompatibility on clinical outcome is controversial. A retrospective analysis of 310 patients who underwent HSCT with reduced-intensity conditioning between 1998 and 2011 was performed to investigate the frequency and clinical implications of anti-RBC antibodies in passenger lymphocyte syndrome (PLS) after minor ABO mismatch (mm), persistent or recurring recipient type ABO antibodies (PRABO) after major ABO mm HSCT, and autoimmune hemolytic anemia (AIHA). Transplantation characteristics and clinical outcome were analyzed by univariate and multivariate analysis for groups with or without anti-RBC antibodies. ABO blood group incompatibility did not affect clinical outcome despite an increased requirement of blood transfusion. Twelve patients with AIHA, 6 patients with PLS, and 12 patients with PRABO post-HSCT were identified. AIHA did not affect overall survival (OS) or transplant-related mortality (TRM), but patients with AIHA had a lower incidence of grades II to IV acute graft-versus-host disease (P = .05). OS in the PLS group was 0% compared with 61% in the whole group receiving minor ABO mm transplants (P < .001). Comparing PRABO patients with those receiving a major ABO mm HSCT, the OS was 17% versus 73% (P = .002) and TRM was 50% versus 21% (P = .03). At our center, PLS after minor ABO mm and PRABO antibodies after major ABO mm HSCT are significant risk factors for decreased OS and TRM. Our results suggest that occurrence of unexpected ABO antibodies after HSCT warrant a wider investigation individual to find the underlying cause., (Copyright © 2014. Published by Elsevier Inc.)

Allogeneic hematopoietic stem cell transplantation is a successful treatment for hematologic malignancies and a variety of genetic and metabolic disorders. In the period following stem cell transplantation, the immune-compromised milieu allows opportunistic pathogens to thrive. Epstein-Barr virus-associated post-transplant lymphoproliferative disease can be a life-threatening complication for transplanted patients because of suppressed T-cell-mediated immunity. We analyzed possible risk factors associated with post-transplant lymphoproliferative disease in a cohort of over 1,000 patients. The incidence of post-transplant lymphoproliferative disease was 4%. Significant risk factors identified by multivariate analysis were: human leukocyte antigen-mismatch (P<0.001), serological Epstein-Barr virus mismatch recipient-/donor+ (P<0.001), use of reduced intensity conditioning (P=0.002), acute graft-versus-host disease grade II to IV (P=0.006), pre-transplant splenectomy (P=0.008) and infusion of mesenchymal stromal cells (P=0.015). The risk of post-transplant lymphoproliferative disease has increased in more recent years, from less than 2% before 1998 to more than 6% after 2011. Additionally, we show that long-term survival of patients with post-transplant lymphoproliferative disease is poor despite initial successful treatment. The 3-year survival rate among the 40 patients with post-transplant lymphoproliferative disease was 20% as opposed to 62% among patients without post-transplant lymphoproliferative disease (P<0.001). The study identifies patients at risk of post-transplant lymphoproliferative disease after transplantation in need of pre-emptive measures.

Allogeneic hematopoietic stem cell transplantation is associated with several complications and risk factors, for example, graft versus host disease (GVHD), viral infections, relapse, and graft rejection. While high levels of CD3+ cells in grafts can contribute to GVHD, they also promote the graft versus leukemia (GVL) effect. Infusions of extra lymphocytes from the original stem cell donor can be used as a treatment after transplantation for relapse or poor immune reconstitution but also they increase the risk for GVHD. In peripheral blood, 95% of T-cells express the αβ T-cell receptor and the remaining T-cells express the γδ T-cell receptor. As αβ T-cells are the primary mediators of GVHD, depleting them from the graft should reduce this risk. In this pilot study, five patients transplanted with HLA-matched related and unrelated donors were treated with αβ T-cell depleted stem cell boosts. The majority of γδ T-cells in the grafts expressed Vδ2 and/or Vγ9. Most patients receiving αβ-depleted stem cell boosts increased their levels of white blood cells, platelets, and/or granulocytes 30 days after infusion. No signs of GVHD or other side effects were detected. A larger pool of patients with longer follow-up time is needed to confirm the data in this study.

The study included 110 consecutive patients with hematological malignancies receiving fludarabine-based reduced intensity conditioning (RIC) and hematopoietic stem cell transplantation (HSCT) from matched unrelated donors. The median age was 55 yr (range 11-68) and all but 15 patients received peripheral blood stem cell grafts. Antithymocyte globulin (ATG) (Thymoglobulin, Genzyme) at a total dose of 6 mg/kg (n = 66) or 8 mg/kg (n = 44) was given to all patients according to protocol. The ATG dose did not affect time-to-neutrophil or platelet engraftment. The incidences of acute GVHD grades II-IV were 34% and 18% (p = 0.11) and of chronic GVHD were 40% and 26% (p = 0.46) in patients receiving 6 and 8 mg/kg of ATG, respectively. The five-yr relapse-free survival (RFS) was 61% and 36% (p = 0.14) in patients, given low and high ATG dose, respectively. In patients given low-dose ATG, the incidence of relapse was lower compared to those given high-dose ATG, 19% vs. 41% (p = 0.04). In multivariate analysis, age >50 yr (p < 0.001), absence of acute (p < 0.001) and chronic GVHD (p = 0.001) were correlated to relapse, and low-dose ATG was associated with improved RFS (p < 0.05). A high dose (8 mg/kg) of ATG in RIC HSCT with unrelated donors increased the risk for relapse and reduced the RFS., (© 2013 John Wiley & Sons A/S.)

Long-term stable mixed chimerism (MC) is a rare phenomenon after hematopoietic stem cell transplantation (HSCT) characterized by 5% to 95% residual recipient hematopoietic cells. The underlying mechanisms of MC are largely unknown. In this study we compared full donor chimerism with long-lasting stable MC for a median of 9.5 years (range, 5 to 16.5) post-HSCT in patients with nonmalignant diseases. Several factors significantly associated with the likelihood of stable MC development were identified by univariate analysis, eg, younger donor age, sibling donor, and conditioning regimen. Despite a limited patient cohort, our multivariate analysis could confirm that a sibling donor was associated with stable MC development. Furthermore, development of acute-graft-versus-host disease and blood stream infection was significantly more prevalent in the full donor chimerism patient group. Additionally, significant fluctuations in the recipient-to-donor chimerism ratio decreased over time after HSCT in MC patients., (Copyright © 2013 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

We determined total rabbit-IgG (r-ATG) levels in serum samples before (day 0) and after (day 11 and day 25) unrelated donor umbilical cord blood transplantation (UCBT). Most patients (27/41) suffered from a haematological malignancy. There were 25 children and 16 adults. All patients received rabbit anti-thymocyte globulin (ATG) at a total dose of 6 or 8mg/kg as part of the conditioning. No correlation between the dose of ATG and serum r-ATG levels post UCBT was found. The cumulative incidence of acute GVHD grades III-IV in patients given the 6 and 8mg/kg ATG dose was 15% and 13% (ns), respectively. Patients with r-ATG≤40μg/mL 11days after UCBT (n=19) had a higher incidence of grades III-IV acute GVHD (32% vs. 0%, p<0.01), higher TRM (69% vs. 7%, p=0.005), less relapse (17% vs. 82%, p<0.01) but similar relapse-free survival (RFS) (10% vs. 18%, p=0.4) compared to those with r-ATG>40μg/mL (n=17). Low serum-levels of r-ATG early after transplantation seem to be a strong predictor for acute GVHD grades III-IV, TRM and a low incidence of relapse in patients treated with thymoglobulin before unrelated donor UCBT., (Copyright © 2012 Elsevier B.V. All rights reserved.)

For prevention of graft-versus-host disease (GVHD), treatment of 24 haematopoietic stem cell transplantation (HSCT) patients with sirolimus and tacrolimus was compared to treatment of matched controls with cyclosporine-based regimens. The patients mainly had non-malignant disorders. Two-thirds of the donors were unrelated, and bone marrow was the most common source of stem cells. Rejection occurred in four patients in the sirolimus group and three in the control group. Donor chimerism for CD3, CD19 and CD33 was similar in the two groups. The cumulative incidence of grade II acute GVHD was 22% in the sirolimus patients and 17% in the controls (P=0.78). No patients developed acute GVHD of grades III-IV. The cumulative incidence of chronic GVHD was 25% and 37% in the two groups, respectively (P=0.40). Two patients in the sirolimus group developed Epstein-Barr virus lymphoma, and none in the controls. Side effects and toxicity were similar in the two groups. There was no transplant-related mortality at 5 yr in the sirolimus group, as opposed to 8% in the controls (P=0.47). Survival at 5 yr was 95% and 92%. Thus, sirolimus combined with tacrolimus is a promising immunosuppressive regimen in HSCT, also for non-malignancies, and its efficacy should be confirmed in prospective clinical trials., (© 2011 John Wiley & Sons A/S.)

We analyzed the outcome of allogeneic hematopoietic stem cell transplantation (HSCT) over the past 2 decades. Between 1992 and 2009, 953 patients were treated with HSCT, mainly for a hematologic malignancy. They were divided according to 4 different time periods of treatment: 1992 to 1995, 1996 to 2000, 2001 to 2005, and 2006 to 2009. Over the years, many factors have changed considerably regarding patient age, diagnosis, disease stage, type of donor, stem cell source, genomic HLA typing, cell dose, type of conditioning, treatment of infections, use of granulocyte-colony stimulating factor (G-CSF), use of mesenchymal stem cells, use of cytotoxic T cells, and home care. When we compared the last period (2006-2009) with earlier periods, we found slower neutrophil engraftment, a higher incidence of acute graft-versus-host disease (aGVHD) of grades II-IV, and less chronic GVHD (cGHVD). The incidence of relapse was unchanged over the 4 periods (22%-25%). Overall survival (OS) and transplant-related mortality (TRM) improved significantly in the more recent periods, with the best results during the last period (2006-2009) and a 100-day TRM of 5.5%. This improvement was also apparent in a multivariate analysis. When correcting for differences between the 4 groups, the hazard ratio for mortality in the last period was 0.59 (95% confidence interval [CI]: 0.44-0.79; P < .001) and for TRM it was 0.63 (CI: 0.43-0.92; P = .02). This study shows that the combined efforts to improve outcome after HSCT have been very effective. Even though we now treat older patients with more advanced disease and use more alternative HLA nonidentical donors, OS and TRM have improved. The problem of relapse still has to be remedied. Thus, several different developments together have resulted in significantly lower TRM and improved survival after HSCT over the last few years., (Copyright © 2011 American Society for Blood and Marrow Transplantation. Published by Elsevier Inc. All rights reserved.)

It has been shown that antibodies to donor CD34+/VEGFR-2+ stem cells or antibodies against mismatched HLA are associated with graft rejection after hematopoietic stem cell transplantation (HSCT). CD34/VEGFR-2 positive stem cells have been implicated to play a major role in engraftment after HSCT. In this study we treated four patients with an imminent risk of antibody-mediated rejection with immune modulation, i.e. plasma exchange, intravenous immunoglobulin (IVIG), and rituximab before HSCT. Three of the patients had been previously transplanted and rejected their initial grafts after 12 months, 1 month, and less than 1 month, respectively. The fourth patient was not transplanted previously but had HLA directed antibodies present against the graft. During the immune modulatory treatment we followed the pattern of antibodies in sera using FACS and microcytotoxicity assay. We could show that two patients had antibodies against donor CD34+/VEGFR-2+ cells while the other two had antibodies directed against HLA. All four patients tolerated the immune modulatory regimen without any side effects. In this preliminary study we show that immune modulatory treatment may be used to reduce antibody levels and to prevent rejection after HSCT. In two of the three patients which experienced previous rejections and had detectable anti-HLA or anti-CD34+/VEGFR-2+ antibodies, immune modulation resulted in engraftment. In the fourth patient with known anti-HLA-class I antibodies, the treatment also resulted in engraftment. Our results encourage further studies regarding this treatment regimen., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Allogeneic haematological stem cell transplantation (HSCT) has developed into immunotherapy. Donor CD4+, CD8+ and natural killer (NK) cells have been reported to mediate graft-versus-leukaemia (GVL) effects, using Fas-dependent killing and perforin degranulation to eradicate malignant cells. Cytokines, such as interleukin-2, interferon-gamma and tumour necrosis factor-alpha potentiate the GVL effect. Post-transplant adoptive therapy of cytotoxic T-cells (CTL) against leukaemia-specific antigens, minor histocompatibility antigens, or T-cell receptor genes may constitute successful approaches to induce anti-tumour effects. Clinically, a significant GVL effect is induced by chronic rather than acute graft-versus-host disease (GVHD). An anti-tumour effect has also been reported for myeloma, lymphoma and solid tumours. Reduced intensity conditioning enables HSCT in older and disabled patients and relies on the graft-versus-tumour effect. Donor lymphocyte infusions promote the GVL effect and can be given as escalating doses with response monitored by minimal residual disease. A high CD34+ cell dose of peripheral blood stem cells increases GVL. There is a balance between effective immunosuppression, low incidence of GVHD and relapse. For instance, T-cell depletion of the graft increases the risk of relapse. This paper reviews the current knowledge in graft-versus-cancer effects. Future directions, such as immunotherapy using leukaemia-specific CTLs, allo-depleted T-cells and suicide gene manipulated T-cells, are presented.

Background: Therapies for localized prostate cancer include curative surgery and radiotherapy while treatment of metastatic disease is often inefficient. Graft-versus-tumor effects of allogeneic stem-cell transplantation (ASCT) have been described for several types of solid tumors but have not been reported for prostate cancer. We, therefore, investigated the potential of ASCT as treatment for noncurable prostate cancer., Methods: A patient underwent ASCT from his human leukocyte antigen (HLA)-identical sister as treatment for his metastatic prostate adenocarcinoma. Frequencies of prostate-specific T cells in the peripheral blood of the patient, ASCT donor and a group of control individuals were determined by flow cytometry using pentameric HLA-A2 complexes containing peptides derived from the prostate-specific antigen (PSA). Cytotoxic activity of PSA-peptide-specific T cells against peptide-pulsed target cells was analyzed ex vivo by Cr-release assays., Results: Stable clinical and laboratory remission lasting more than 4 years was observed after ASCT. Using HLA-containing pentamers with PSA-derived peptides we could detect prostate-specific CD8+ T cells in this patient at high frequencies over several months. Furthermore, higher frequencies of PSA-specific T cells were revealed in the blood of the patient and female controls when compared with healthy males., Conclusions: Lymphocytes from the peripheral blood of the recipient, but not from donor or other tested control individuals, exhibited ex vivo cytotoxic activity against target cells pulsed with the relevant synthetic peptides and efficiently expanded in vitro following specific restimulations. Thus, the results of this study indicate that female to male ASCT can increase the frequency and enhance specific-responsiveness of PSA-specific T cells in transplant recipients.

The aim was to evaluate two transplant strategies for patients who lack HLA-identical donors, namely HLA-A, HLA-B or -DR beta 1 mismatched unrelated donor (MM URD) transplants (n=14) and umbilical cord blood transplants (UCB, n=27). Diagnosis, disease stage and age were similar in the two groups. Cell dose was lower in the UCB group (P<0.001). Median time to ANC of >0.5 x 10(9)/l was 30 days in the UCB group and 17 days in the MM URD group (P=0.002). Engraftment of plt was delayed in the UCB group (P=0.03). The UCB patients required fewer erythrocyte transfusions (P=0.001). At 100 days, complete donor chimerism for CD3 was 63 and 44% in the UCB and MM URD groups, respectively. Acute GVHD of grades II-IV were 30% in the UCB group and 21% in the MM URD group. The corresponding figures for chronic GVHD were 9 and 20%, respectively. TRM was 30% in the UCB patients and 50% in the MM URD patients. Three-year survival was 66% in the UCB group and 14% in the MM URD group (P=0.006). Although the material is small and heterogeneous, engraftment was delayed, leukocyte chimerism was not significantly different and survival was superior using UCB rather than MM URD transplants.