Mehmet Uzunel

Karolinska University Hospital, Tukholma, Stockholm, Sweden

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Publications (80)434.39 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Because human white adipocytes display a high turnover throughout adulthood, a continuous supply of precursor cells is required to maintain adipogenesis. Bone marrow (BM)-derived progenitor cells may contribute to mammalian adipogenesis; however, results in animal models are conflicting. Here we demonstrate in 65 subjects who underwent allogeneic BM or peripheral blood stem cell (PBSC) transplantation that, over the entire lifespan, BM/PBSC-derived progenitor cells contribute ∼10% to the subcutaneous adipocyte population. While this is independent of gender, age, and different transplantation-related parameters, body fat mass exerts a strong influence, with up to 2.5-fold increased donor cell contribution in obese individuals. Exome and whole-genome sequencing of single adipocytes suggests that BM/PBSC-derived progenitors contribute to adipose tissue via both differentiation and cell fusion. Thus, at least in the setting of transplantation, BM serves as a reservoir for adipocyte progenitors, particularly in obese subjects. Copyright © 2015 Elsevier Inc. All rights reserved.
    Cell metabolism 07/2015; DOI:10.1016/j.cmet.2015.06.011 · 16.75 Impact Factor
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    Biology of Blood and Marrow Transplantation 02/2015; 21(2):S149-S150. DOI:10.1016/j.bbmt.2014.11.211 · 3.35 Impact Factor
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    ABSTRACT: Background Hypogammaglobulinemia (hypo-IgG) is common early post-HSCT in children, occasionally necessitating long-term immunoglobulin (Ig) G replacement therapy. IgG replacement may not reduce mortality, although infectious complications are decreasedProcedureClinical data and samples from 86 children were analyzed retrospectively with the aim to identify risk factors for developing long-term hypo-IgG (i.e., requiring ≥3 months IgG replacement) post-HSCT and studying the underlying biology. Laboratory studies covered serum cytokines, IGHG2 genotyping and routine laboratory investigations. Results were analyzed statistically.ResultsForty-eight percent of the children developed long-term hypo-IgG. These children were younger (<5 years) and had higher acute GvHD incidence, but had better overall survival (88% vs. 69%, P = 0.036). Significantly lower Ig levels post-HSCT but equal immune cell recovery were seen in patients with long-term hypo-IgG compared with those of transient or no hypo-IgG. Pre-HSCT IL-6 and -7 and post-HSCT BAFF and APRIL levels were significantly higher in the long-term hypo-IgG group.Conclusions Findings suggests an unfavorable cytokine milieu for graft-derived immune recovery, possibly inducing Ig isotype class switch arrest. Younger age, acute GvHD, and higher pre-HSCT IL-6 levels were identified as significant risk factors for long-term hypo-IgG. Long-term hypo-IgG post-HSCT does not need to be unfavorable and could be an effect of deteriorated cytokine signaling. Pediatr Blood Cancer © 2015 Wiley Periodicals, Inc.
    Pediatric Blood & Cancer 01/2015; 62(5). DOI:10.1002/pbc.25409 · 2.56 Impact Factor
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    ABSTRACT: Antigen recognition reduces T cell motility, induces prolonged contact with antigen-presenting cells and activation through mechanisms that remain unclear. Here we show that the T cell receptor (TCR) and CD28 regulate T cell motility, contact with antigen-presenting cells and activation through endogenous thrombospondin-1 (TSP-1) and its receptors low density lipoprotein receptor-related protein 1 (LRP1), calreticulin and CD47. Antigen stimulation induced a prominent up-regulation of TSP-1 expression, transiently increased and subsequently decreased LRP1 expression whereas calreticulin was unaffected. This antigen-induced TSP-1/LRP1 response downregulated a motogenic mechanism directed by LRP1-mediated processing of TSP-1 in cis within the same plasma membrane while promoting contact with antigen-presenting cells and activation through cis interaction of the C-terminal domain of TSP-1 with CD47 in response to NH-2-terminal TSP-1 triggering by calreticulin. The antigen-induced TSP-1/LRP1 response maintained a reduced but significant motility level in activated cells. Blocking CD28 costimulation abrogated LRP1 and TSP-1 expression and motility. TCR/CD3 ligation alone enhanced TSP-1 expression whereas CD28 ligation alone enhanced LRP1 expression. Silencing of TSP-1 inhibited T cell conjugation to antigen-presenting cells and Th1 and Th2 cytokine responses. The Th1 response enhanced motility and increased TSP-1 expression through IL-2, whereas the Th2 response weakened motility and reduced LRP1 expression through IL-4. Ligation of the TCR and CD28 thus elicits a TSP-1/LRP1 response that stimulates prolonged contact with antigen-presenting cells and although down-regulating motility maintains a significant motility level to allow serial contacts and activation. Th1 and Th2 cytokine responses differentially regulate T cell expression of TSP-1 and LRP1 and motility. This article is protected by copyright. All rights reserved.
    Immunology 11/2014; 144(4). DOI:10.1111/imm.12424 · 3.74 Impact Factor
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    ABSTRACT: 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.
    Research Journal of Immunology 10/2014; 2014:578741. DOI:10.1155/2014/578741
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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; DOI:10.1089/scd.2013.0588 · 4.20 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 09/2013; 8(9):e74534. DOI:10.1371/journal.pone.0074534 · 3.23 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 03/2013; 31(3). DOI:10.1002/stem.1314 · 7.70 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; 94(10). DOI:10.1097/TP.0b013e31826c39b2 · 3.78 Impact Factor
  • Clinical Infectious Diseases 08/2012; · 9.42 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. DOI:10.1093/cid/cis625 · 9.42 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 07/2012; 30(7):1575-8. DOI:10.1002/stem.1118 · 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. DOI:10.1016/j.clim.2011.12.001 · 3.99 Impact Factor
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    Biology of Blood and Marrow Transplantation 02/2012; 18(2):S220-S221. DOI:10.1016/j.bbmt.2011.12.051 · 3.35 Impact Factor
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    Biology of Blood and Marrow Transplantation 02/2012; 18(2):S339. DOI:10.1016/j.bbmt.2011.12.355 · 3.35 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. DOI:10.1111/j.1600-0609.2011.01685.x · 2.41 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. DOI:10.1089/scd.2011.0310 · 4.20 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. DOI:10.1016/j.bbmt.2011.05.001 · 3.35 Impact Factor
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    J Gertow · S Berglund · M Okas · M Uzunel · L Berg · K Kärre · J Mattsson · M Uhlin
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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. DOI:10.1111/j.1365-2249.2010.04212.x · 3.28 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. DOI:10.1203/PDR.0b013e3181eb2eb4 · 2.84 Impact Factor

Publication Stats

4k Citations
434.39 Total Impact Points

Institutions

  • 2001–2014
    • Karolinska University Hospital
      • • Department of Clinical Immunology and Transfusion Medicine
      • • Department of Obstetrics and Gynecology
      • • Department of Hematology
      Tukholma, Stockholm, Sweden
    • University of Leipzig
      Leipzig, Saxony, Germany
  • 2000–2012
    • Karolinska Institutet
      • • Institutionen för laboratoriemedicin
      • • Department of Microbiology, Tumor and Cell Biology (MTC)
      • • Department of Clinical Immunology
      Solna, Stockholm, Sweden
  • 2008
    • Akademiska Sjukhuset
      Uppsala, Uppsala, Sweden
  • 2003
    • University of Gothenburg
      Goeteborg, Västra Götaland, Sweden