Mehmet Uzunel

Karolinska University Hospital, Tukholma, Stockholm, Sweden

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Publications (69)358.51 Total impact

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    ABSTRACT: 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 (CML), chronic lymphatic leukemia (CLL), 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=0,038). In patients with chronic leukemia high TREC levels were correlated with improved RFS (p=0.048). For patients with MDS, high TREC levels at 9 months post-transplantation were associated with higher RFS at 5 years (p=0.01) and lower relapse incidence (p=0.01). This study shows the potential use of TREC measurement in blood to predict relapse in patients with AML and MDS after ASCT.
    Stem cells and development 03/2014; · 4.15 Impact Factor
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    ABSTRACT: The placenta protects the fetus from the mother's immune system. We have previously found that fetal membrane cells (FMCs) isolated from term placenta prevent alloreactivity in vitro. FMCs share many features with bone marrow-derived mesenchymal stromal cells (MSCs), which we previously introduced to treat severe acute graft-versus-host disease (GVHD). Here, we tested FMCs for treatment of steroid-refractory acute GVHD. After two passages in culture, approximately 10(9) FMCs were obtained from one single placenta, although not all cells from passage 0 and passage 1 were used for expansion. The FMCs were positive for CD29, CD44, CD73, CD90, CD105, and CD49d but were negative for hematopoietic, endothelial, and epithelial markers. Microsatellite polymorphism analysis showed that FMCs were of maternal origin. All FMCs used showed normal karyotype. Nine patients who had undergone hematopoietic stem cell transplantation and who had developed steroid-refractory grade III--IV acute GVHD were given 0.9--2.8 x 10(6) FMCs/kg at 15 infusions. Median age was 57 years. There was no toxicity from infusion of FMCs in eight patients. One patient had seizures after infusion. Two of eight evaluable patients had a complete response and four had a partial response, giving an overall response rate of 75%. Two patients showed no response at all. Three patients are alive from 6 to 21 months after HSCT. One patient is well and two have chronic GVHD. Thus, FMCs may be successfully used for immune modulation and tissue repair.
    Stem Cells 01/2013; · 7.70 Impact Factor
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    ABSTRACT: Naturally acquired microchimerism may arise in the mother and her child during pregnancy when bidirectional trafficking of cells occurs through the placental barrier. The occurrence of maternal microchimerism (maternal cells in the offspring) has been associated with several autoimmune diseases, especially in children. Systemic Lupus erythematosus (SLE) is an autoimmune disorder with a resemblance to graft-versus-host disease. The aim of this study was to investigate the association between maternal microchimerism in the blood and SLE. Thirty-two patients with SLE, 17 healthy brothers of the patients, and an additional 12 unrelated healthy men were the subjects in this study. A single-nucleotide polymorphism unique to each mother was identified, and maternal microchimerism in the study group and in the control group was detected using a quantitative real-time polymerase chain reaction technique. No differences in the frequency or the concentration of maternal cells were apparent in the blood of patients with SLE or in that of the controls. Two patients and one control tested positive for maternal microchimerism, but the positive subjects were all negative at a follow-up 16 years later. The sensitivity of the method was estimated to 1/10.000. These results show no association between SLE and maternal microchimerism. The frequency of maternal microchimerism in the blood of adults overall may be lower than earlier reported.
    PLoS ONE 01/2013; 8(9):e74534. · 3.53 Impact Factor
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    ABSTRACT: METHODS: We performed a retrospective single-center analysis of 50 umbilical cord blood transplantations performed from 2001 to 2010, including 37 single and 13 double umbilical cord blood transplantations. Thirty children and 20 adults were included. Eighteen patients had nonmalignant diseases and 32 had hematologic malignancies. RESULTS: The rate of engraftment of neutrophils was 88% at a median time of 29 days (range, 3-79). Complete donor chimerism (DC) within the CD19, CD3, and CD33 cell lineages was seen in 74%, 72%, and 76% of the patients, respectively. DC was associated with acute graft-versus-host disease (GVHD) grades II to IV for the CD3 cell lineage (P=0.01) and, in multivariate analysis, with total body irradiation for all lineages (P<0.01). Overall survival (OS) at 1 and 5 years was 55% and 43%. Nonmalignant diseases were associated with better 5-year OS (72%) than malignancies (28%; P=0.026). In multivariate analysis, a negative correlation was seen between OS and age (hazard ratio [HR], 1.04; 95% confidence interval [95% CI], 1.02-1.06; P<0.001), acute GVHD grades III and IV (HR, 3.43; 95% CI, 1.95-6.02; P<0.001), and mesenchymal stem cell treatment (HR, 2.66; 95% CI, 1.11-6.35; P=0.027). Transplant-related mortality at 100 days and 1 year was 16% and 30%. The incidence of acute GVHD grades II to IV was 34%. Acute GVHD grades III and IV was associated with ABO incompatibility (HR, 2.61; P=0.05) and myeloablative conditioning (HR, 4.17; P=0.047). CONCLUSION: The outcome in patients with nonmalignant diseases was acceptable, but transplant-related mortality in the whole group remains high. A significantly higher rate of DC was associated with total body irradiation-based conditioning and with acute GVHD grades II and IV.
    Transplantation 10/2012; · 3.78 Impact Factor
  • Clinical Infectious Diseases 08/2012; · 9.37 Impact Factor
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    ABSTRACT: Background. Viral infections are major complications after allogeneic hematopoietic stem cell transplantation (HSCT). During posttransplant immunosuppression the regular T-cell control is compromised. Even if treatment strategies against infections caused by herpes viruses such as cytomegalovirus, Epstein-Barr virus, and adenovirus have improved, the mortality rate is still considerable. If primary antiviral therapy fails or cannot be tolerated, adoptive therapy with virus-specific cytotoxic T cells (CTL) can be utilized. Methods. In this study, we used virus-specific CTLs to treat 8 patients suffering from severe viral infections after allogeneic HSCT. Using positive selection with HLA multimers and magnetic beads, we isolated CTLs from both frozen donor material as well as third-party donors within hours. Results. At 90 days after CTL infusions 7 out of 8 patients were still living. CTLs infused from third-party donors were detected in 5 of 6 patients up to 76 days after infusion. No graft-versus-host disease associated with CTL infusions was observed. Conclusions. Our separation approach offers a rapid alternative for adoptive CTL therapy if primary antiviral treatment strategies fail. Because no prolonged expansion steps are needed, this method may be used for early treatment of patients suffering from life-threatening infectious complications.
    Clinical Infectious Diseases 07/2012; 55(8):1064-73. · 9.37 Impact Factor
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    ABSTRACT: Mesenchymal stromal cells (MSCs) are explored as a novel treatment for a variety of medical conditions. Their fate after infusion is unclear, and long-term safety regarding malignant transformation and ectopic tissue formation has not been addressed in patients. We examined autopsy material from 18 patients who had received human leukocyte antigen (HLA)-mismatched MSCs, and 108 tissue samples from 15 patients were examined by PCR. No signs of ectopic tissue formation or malignant tumors of MSC-donor origin were found on macroscopic or histological examination. MSC donor DNA was detected in one or several tissues including lungs, lymph nodes, and intestine in eight patients at levels from 1/100 to <1/1,000. Detection of MSC donor DNA was negatively correlated with time from infusion to sample collection, as DNA was detected from nine of 13 MSC infusions given within 50 days before sampling but from only two of eight infusions given earlier. There was no correlation between MSC engraftment and treatment response. We conclude that MSCs appear to mediate their function through a "hit and run" mechanism. The lack of sustained engraftment limits the long-term risks of MSC therapy.
    Stem Cells 05/2012; 30(7):1575-8. · 7.70 Impact Factor
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    ABSTRACT: T-cell deficiency after allogeneic stem cell transplantation (ASCT) is common and has major impact on clinical outcome. In this retrospective study 210 patients were analyzed with regards to levels of T-cell receptor excision circles (TRECs) during the first 24 months after transplantation. We could for the first time show a significant correlation between the use of bone marrow grafts and higher TREC levels >6 months post-ASCT (p<0.001). Treatment with anti-thymocyte globulin was correlated with lower TREC levels ≤6 months post-ASCT (p<0.001). Patients with TREC levels above median at 3 months had a superior overall survival, 80% vs. 56% (p=0.002), and lower transplantation-related mortality, 7% vs. 21% (p=0.01). We conclude that graft source and conditioning regimen may have a significant effect on T-cell reconstitution after ASCT and can thus affect outcome. These results strongly support the use of TREC measurement as part of the standard repertoire of immunological monitoring after ASCT.
    Clinical Immunology 03/2012; 142(3):343-50. · 3.77 Impact Factor
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    ABSTRACT: 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.
    European Journal Of Haematology 10/2011; 87(6):503 - 509. · 2.55 Impact Factor
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    ABSTRACT: Cord blood (CB) as a source of stem cells has been a successful addition to the field of allogeneic stem cell transplantation (ASCT). The increased human leukocyte antigen (HLA) permissiveness of CB grafts has made it possible for more patients to undergo treatment. The drawback is that patients suffer from a longer period of compromised immunity. We analyzed T-cell receptor excision circles (TRECs), immunoglobulin G (IgG), and immunoglobulin M (IgM) levels after cord blood transplantation (CBT) in 50 patients transplanted at our center. These immunological parameters were compared retrospectively with clinical factors and complications. We found that TREC levels after CBT were lower in adults, patients with myeloablative conditioning, and in patients with a lower nucleated cell dose in the graft. In addition mesenchymal stem cells (MSC) as co-infusion at the time of CBT had a negative effect on TREC reconstitution. This was found to be associated with decreased overall survival for this patient category. Reduced IgM and IgG levels post-CBT were associated with a major AB0 mismatch, and infusion of MSCs. Our results highlight the importance of close monitoring of the immune reconstitution after CBT. In addition it shows a potentially new suppressive effect of MSCs on the immune system.
    Stem cells and development 08/2011; 21(9):1409-17. · 4.15 Impact Factor
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    ABSTRACT: 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.
    Biology of blood and marrow transplantation: journal of the American Society for Blood and Marrow Transplantation 05/2011; 17(11):1688-97. · 3.15 Impact Factor
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    ABSTRACT: Double cord blood transplantation (DCBT) with two matched or partially matched cord blood units has been implemented successfully to circumvent the limitations of graft cell dose associated with single CBT. After DCBT, sustained haematopoiesis is derived almost exclusively from only one of the donated units. None the less, we previously observed two of six evaluable DCBT patients still having mixed donor-donor chimerism at 28 and 45 months post-transplantation, respectively. In the present study we utilize flow cytometry techniques to perform the first thorough analysis of phenotype and functionality of cord blood units in patients with mixed donor-donor chimerism. Our results suggest that the two stable cord blood units are different phenotypically and functionally: one unit shows more naive T cells, lower T cell cytokine production and higher frequencies of natural killer cells, the other shows higher frequencies of well-differentiated and functional lymphocytes. Additionally, in comparison with control patients having a single prevailing cord blood unit, the patients with donor-donor chimerism exhibit less overall T cell cytokine production and a smaller fraction of memory T cells. Furthermore, our results indicate that human leucocyte antigen-C match of donor units may partly explain the development of a donor-donor mixed chimerism.
    Clinical & Experimental Immunology 10/2010; 162(1):146-55. · 3.41 Impact Factor
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    ABSTRACT: During pregnancy small amounts of cells pass between the mother and the fetus, and this transfer may give rise to a chimeric state that persist for years in both individuals. Both fetal and maternal microchimerism (MMc) have been associated with different autoimmune disorders. Information about MMc in tissues of healthy individuals is sparse but is important when looking for maternal cells within affected tissues of certain diseases. The aim of this study was to investigate the occurrence of maternal cells in tonsils and adenoids of 20 healthy children between the ages of 2 and 15 years. All the children underwent surgery because of recurrent tonsillitis or respiratory obstruction. MMc was detected using an RT-PCR assay based on differences in gene polymorphisms between mother and child. We found maternal cells in the tonsils and/or adenoids in four of 20 children. This frequency is less than the frequency of maternal cells found in the peripheral blood of healthy adults but in agreement with the previously reported frequency of maternal chimerism in control tissues
    Pediatric Research 09/2010; 68(3):199-204. · 2.67 Impact Factor
  • Biology of Blood and Marrow Transplantation - BIOL BLOOD MARROW TRANSPLANT. 01/2010; 16(2).
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    ABSTRACT: Epstein-Barr virus (EBV)-related malignancies such as post-transplant lymphoproliferative disease (PTLD) are severe complications after allogeneic stem cell transplantation and solid-organ transplantation. In immunosuppressed transplant recipients, the activity of EBV-specific CTLs are often decreased or absent which leads to an increased risk of developing PTLD. If primary treatment modalities of PTLD fail, the most efficient way of treating the malignancy is adopting EBV-specific CTLs from the donor or, more recently, third-party donors. However, both are time consuming and expensive and often it is too late to administer cells to the patient. We have for the first time, using a rapid isolation protocol of EBV-specific T cells, treated and cured a patient suffering from PTLD with multiple-associated tissue lesions, using her haplo-identical mother as a donor. This treatment approach paves way for a new possibility to within-days treat patients with life-threatening EBV-associated malignancies.
    Cancer Immunology and Immunotherapy 11/2009; 59(3):473-7. · 3.64 Impact Factor
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    ABSTRACT: Allogeneic stem cell transplantation (SCT) from cord blood (CB) as a stem cell source is a promising alternative when no human leukocyte antigen-matched donor is found. Donor lymphocyte infusion (DLI) is a possible treatment modality for threatening graft failure or relapse of an underlying malignancy after transplantation. Ethical and logistical reasons limit the possibility of DLI in the setting of CB SCT. To remedy this restriction, we performed expansion of donor T cells in vitro from CB grafts in a clinical setting for use as future DLI and characterized the expanded cells in comparison to T cells from CB acquired ex vivo and adult peripheral blood. T cells were expanded from grafts used for transplantation, upon CD3/CD28 crosslinking and culture in interleukin-2. Phenotype and function of T cells were assessed by flow cytometry and mixed lymphocyte culture assays. T-cell receptor repertoire distribution was evaluated with polymerase chain reaction-based spectratyping. We were able to amplify T cells to sufficient amounts for DLI in 13 out of 13 initiated expansions. Expanded T cells presented with an activated phenotype and could be induced to produce cytokines by a nonspecific stimulus. When exposed to allogeneic targets, expanded CB T cells proliferated at comparable levels to their ex vivo and adult blood counterparts. In summary, clinical expansion of CB T cells for DLI is feasible and may be a future modality for treatment of graft failure or relapse after SCT.
    Journal of immunotherapy (Hagerstown, Md.: 1997) 11/2009; 33(1):96-105. · 3.20 Impact Factor
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    ABSTRACT: Multipotent mesenchymal stromal cells (MSC) are increasingly used to treat refractory graft-versus-host-disease and other complications after hematopoietic stem cell transplantation (HSCT). We evaluated immunogenicity of HLA-mismatched MSC infused posttransplant to HSCT recipients. Recipient lymphocyte response to MSC and peripheral blood lymphocytes (PBL) from the MSC or third party donors was measured before and after infusion. In vitro primary and rechallenge lymphocyte responses of healthy individuals to MSC and to PBL from the MSC donor were similarly studied. HSCT recipients given MSC responded to third party allostimuli, but showed no response to infused MSC before and upto 6 months after infusion, whereas maintaining an alloresponse to the MSC donor. This indicates immune unresponsiveness restricted to MSC, as the HSCT recipient was not tolerized to the MSC donor. In vitro, we confirmed that MSC failed to prime responder lymphocytes to rechallenge with PBL from the MSC donor, and lymphocytes primed with MSC donor and rechallenged with MSC only showed weak responses at high stimulator-responder ratios. Although MSC up-regulated lymphocyte gene expression of CD25, IFN-gamma, FoxP3, CTLA-4, and IL-10, they failed in both unprimed and primed responders to induce CD25+ (activated) or CD57+ (effector) CD4+ or CD8+ T-lymphocyte subsets and only inconsistently induced FoxP3+ regulatory T-lymphocytes. These results show for the first time that infused MSC are only weakly immunogenic in humans and validate the clinical use of MSC from HLA-mismatched donors.
    Journal of immunotherapy (Hagerstown, Md.: 1997) 07/2009; 32(7):755-64. · 3.20 Impact Factor
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    ABSTRACT: In this retrospective study, we evaluated the chimerism status and outcome in 58 patients (64 transplants) with non-malignant diseases. Reduced intensity conditioning (RIC) was given in half of the transplants. Mixed chimerism (MC) was defined as >1% recipient cells. Two consecutive samples showing >30% recipient cells were defined as high chimerism (high MC). Patients with high MC and the management of these patients were analyzed in greater detail. The overall survival rate was 87%. In total, 23 transplants were donor chimerism (DC) and 41 transplants showed some degree of MC. The incidence of MC was 78 and 50% after RIC and myeloablative conditioning, respectively (P=0.04). Acute GVHD of grades II-III was more common in patients with DC (39%) than in patients with MC (8%) (P=0.002). Owing to high MC, donor lymphocyte infusions were given in 17 cases. The level of MC was reduced in seven cases, unchanged in four cases, increased in one case and there was graft rejection in five cases. A second transplant was carried out in six cases with rejections, five are alive and in remission. We conclude that patients with non-malignant diseases, who develop MC after transplant have less acute GVHD. Despite the high incidence of MC, overall survival is promising.
    Bone marrow transplantation 05/2009; 44(11):757-63. · 3.00 Impact Factor
  • Biology of Blood and Marrow Transplantation - BIOL BLOOD MARROW TRANSPLANT. 01/2009; 15(2):47-47.
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    ABSTRACT: The polymorphic major histocompatibility complex class I-related chain A (MICA) antigen is being increasingly recognized as a potential target molecule for immune cells during allograft rejection. Here we studied whether MICA is a target antigen for antibodies in liver transplant patients. Eighty-four patients were investigated for the presence of MICA antibodies before and after liver transplantation with MICA-transfected cells and flow cytometry. MICA typing was performed by polymerase chain reaction. Expression of MICA in liver cells was determined by reverse-transcription polymerase chain reaction, Western blotting, and flow cytometry. Liver biopsy specimens from liver transplant patients were examined for MICA expression. A total of 22 of 84 (26%) patients had MICA antibodies either pre-transplant (8/84, 9.5%) or post-transplant (14/84, 17%). No correlation between rejection frequencies (14/22, 63%) or other clinical parameters was observed in patients with MICA antibody versus those without MICA antibody (29/62, 47% P = not significant). We found weak messenger RNA expression for MICA in liver cells but no protein or cell surface expression. In addition, no MICA expression in liver biopsy sections from liver transplant patients was observed at any time point, including rejections. Thus, our preliminary results demonstrate no causal relationship between the presence of MICA antibodies and liver allograft rejections. Therefore, it is likely that MICA may not be an important target antigen during liver allograft rejections.
    Liver Transplantation 12/2008; 14(12):1793-802. · 3.94 Impact Factor

Publication Stats

3k Citations
358.51 Total Impact Points

Institutions

  • 2005–2013
    • Karolinska University Hospital
      • Department of Obstetrics and Gynecology
      Tukholma, Stockholm, Sweden
  • 2001–2012
    • Karolinska Institutet
      • • Klinisk immunologi & transfusionsmedicin
      • • Institutionen för laboratoriemedicin
      • • Department of Clinical Immunology
      • • Institutionen för medicin, Huddinge
      • • Department of Transplantation Surgery
      Stockholm, Stockholm, Sweden
  • 2008
    • Akademiska Sjukhuset
      Uppsala, Uppsala, Sweden