Mikael Sigvardsson

Linköping University, Linköping, Östergötland, Sweden

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Publications (116)835.26 Total impact

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    ABSTRACT: To investigate how transcription factor levels impact B-lymphocyte development, we generated mice carrying transheterozygous mutations in the Pax5 and Ebf1 genes. Whereas combined reduction of Pax5 and Ebf1 had minimal impact on the development of the earliest CD19(+) progenitors, these cells displayed an increased T cell potential in vivo and in vitro. The alteration in lineage fate depended on a Notch1-mediated conversion process, whereas no signs of de-differentiation could be detected. The differences in functional response to Notch signaling in Wt and Pax5(+/-)Ebf1(+/-) pro-B cells were reflected in the transcriptional response. Both genotypes responded by the generation of intracellular Notch1 and activation of a set of target genes, but only the Pax5(+/-)Ebf1(+/-) pro-B cells down-regulated genes central for the preservation of stable B cell identity. This report stresses the importance of the levels of transcription factor expression during lymphocyte development, and suggests that Pax5 and Ebf1 collaborate to modulate the transcriptional response to Notch signaling. This provides an insight on how transcription factors like Ebf1 and Pax5 preserve cellular identity during differentiation. © 2015 Ungerbäck et al.
    Journal of Experimental Medicine 06/2015; 212(7). DOI:10.1084/jem.20132100 · 12.52 Impact Factor
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    ABSTRACT: B-lymphocyte development in the bone marrow is controlled by the coordinated action of transcription factors creating regulatory networks ensuring activation of the B-lymphoid program and silencing of alternative cell fates. This process is tightly connected to malignant transformation because B-lineage acute lymphoblastic leukemia cells display a pronounced block in differentiation resulting in the expansion of immature progenitor cells. Over the last few years, high-resolution analysis of genetic changes in leukemia has revealed that several key regulators of normal B-cell development, including IKZF1, TCF3, EBF1 and PAX5, are genetically altered in a large portion of the human B-lineage acute leukemias. This opens for the possibility to directly link the disrupted development as well as aberrant gene expression patterns in leukemic cells to molecular functions of defined transcription factors in normal cell differentiation. This review article focuses on the roles of transcription factors in early B-cell development and their involvement in the formation of human leukemia. Copyright © 2015 American Society of Hematology.
    Blood 05/2015; 126(2). DOI:10.1182/blood-2014-12-575688 · 10.45 Impact Factor
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    ABSTRACT: Ebf1 is a transcription factor with documented dose dependent functions in normal and malignant B-lymphocyte development. To understand more about the roles of Ebf1 in malignant transformation, we investigated the impact of reduced functional Ebf1 dosage on mouse B-cell progenitors. Gene expression analysis suggested that Ebf1 was involved in the regulation of genes important for DNA repair as well as cell survival. Investigation of the DNA damage in steady state as well as after induction of DNA damage by UV light, confirmed that pro-B cells lacking one functional allele of Ebf1 display signs of increased DNA damage. This correlated to reduced expression of DNA repair genes including Rad51 and chromatin immunoprecipitation data suggested that Rad51 is a direct target for Ebf1. Although reduced dosage of Ebf1 did not significantly increase tumor formation in mice, a dramatic increase in the frequency of pro-B cell leukemia was observed in mice with combined heterozygous mutations in the Ebf1 and Pax5 genes revealing a synergistic effect of combined dose reduction of these proteins. Our data suggest that Ebf1 controls DNA repair in a dose dependent manner providing a possible explanation to the frequent involvement of EBF1 gene loss in human leukemia. Copyright © 2015 American Society of Hematology.
    Blood 04/2015; 125(26). DOI:10.1182/blood-2014-12-617282 · 10.45 Impact Factor
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    ABSTRACT: Invariant NKT (iNKT) cells display characteristics of both adaptive and innate lymphoid cells (ILCs). Like other ILCs, iNKT cells constitutively express ID proteins, which antagonize the E protein transcription factors that are essential for adaptive lymphocyte development. However, unlike ILCs, ID2 is not essential for thymic iNKT cell development. In this study, we demonstrated that ID2 and ID3 redundantly promoted iNKT cell lineage specification involving the induction of the signature transcription factor PLZF and that ID3 was critical for development of TBET-dependent NKT1 cells. In contrast, both ID2 and ID3 limited iNKT cell numbers by enforcing the postselection checkpoint in conventional thymocytes. Therefore, iNKT cells show both adaptive and innate-like requirements for ID proteins at distinct checkpoints during iNKT cell development.
    The Journal of Immunology 11/2013; 191(12). DOI:10.4049/jimmunol.1301521 · 4.92 Impact Factor
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    ABSTRACT: Transcription factor doses are of importance for normal and malignant B-lymphocyte development; however, the understanding of underlying mechanisms and functional consequences of reduced transcription factor levels is limited. We have analyzed progenitor and B-lineage compartments in mice carrying heterozygote mutations in the E2a, Ebf1, or Pax5 gene. Although lymphoid progenitors from Ebf1 or Pax5 heterozygote mice were specified and lineage-restricted in a manner comparable with Wt progenitors, this process was severely impaired in E2a heterozygote mutant mice. This defect was not significantly enhanced upon combined deletion of E2a with Ebf1 or Pax5. Analysis of the pre-B-cell compartment in Ebf1 heterozygote mice revealed a reduction in cell numbers. These cells expressed Pax5 and other B-lineage-associated genes, and global gene expression analysis suggested that the reduction of the pre-B-cell compartment was a result of impaired pre-B-cell expansion. This idea was supported by a reduction in IL2Rα-expressing late pre-B-cells as well as by cell cycle analysis and by the finding that the complexity of the VDJ rearrangement patterns was comparable in Wt and Ebf1+/− pre-B-cells, although the number of progenitors was reduced. Heterozygote deletion of Ebf1 resulted in impaired response to IL7 in vitro and reduced expression levels of pre-BCR on the cell surface, providing possible explanations for the observed stage-specific reduction in cellular expansion. Thus, transcription factor doses are critical for specification as well as expansion of B-lymphoid progenitors, providing increased insight into the molecular regulation of B-cell development.
    Journal of Biological Chemistry 09/2013; 288(46). DOI:10.1074/jbc.M113.506261 · 4.57 Impact Factor
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    ABSTRACT: Aging of hematopoietic stem cells (HSCs) leads to several functional changes, including alterations affecting self-renewal and differentiation. Although it is well established that many of the age-induced changes are intrinsic to HSCs, less is known regarding the stability of this state. Here, we entertained the hypothesis that HSC aging is driven by the acquisition of permanent genetic mutations. To examine this issue at a functional level in vivo, we applied induced pluripotent stem (iPS) cell reprogramming of aged hematopoietic progenitors and allowed the resulting aged-derived iPS cells to reform hematopoiesis via blastocyst complementation. Next, we functionally characterized iPS-derived HSCs in primary chimeras and after the transplantation of re-differentiated HSCs into new hosts, the gold standard to assess HSC function. Our data demonstrate remarkably similar functional properties of iPS-derived and endogenous blastocyst-derived HSCs, despite the extensive chronological and proliferative age of the former. Our results, therefore, favor a model in which an underlying, but reversible, epigenetic component is a hallmark of HSC aging.
    Blood 03/2013; 121(21). DOI:10.1182/blood-2012-11-469080 · 10.45 Impact Factor
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    ABSTRACT: Human hematopoietic stem cells reside in the CD34+CD38-CD90+ population in cord blood and bone marrow. However, this cell fraction is heterogeneous, and the phenotype of the rare primitive stem cells remains poorly defined. We here report that primitive cord blood CD34+CD38-CD90+ stem cells, with the ability to reconstitute NOD/SCID-IL2Rγ(c) null mice long term, at 24 weeks after transplantation, can be prospectively isolated at an increased purity by using integrin α2 receptor as an additional stem cell marker. Using a limiting dilution transplantation assay, we found a highly significant enrichment of multilineage reconstituting stem cells in the CD34+CD38-CD90+ cell fraction expressing the integrin α2 receptor, with a frequency of 1/29 cells, as compared to a frequency of 1/157 in the corresponding integrin α2- cells. In line with this, long-term reconstituting stem cells within the cord blood CD34+CD38- cell population were significantly enriched in the integrin α2+ fraction, while stem cells and progenitors reconstituting short-term, at 8-12 weeks, were heterogeneous in integrin α2 expression. Global gene expression profiling revealed that the lineage-marker negative (Lin-) CD34+CD38-CD90+CD45RA- integrin α2+ cell population was molecularly distinct from the integrin α2- cell population and the more mature Lin-CD34+CD38-CD90-CD45RA- cell population. Our findings identify integrin α2 as a novel stem cell marker, which improves prospective isolation of the primitive human hematopoietic stem cells within the CD34+CD38-CD90+ cell population for experimental and therapeutic stem cell applications.
    Stem Cells 02/2013; 31(2). DOI:10.1002/stem.1282 · 6.52 Impact Factor
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    ABSTRACT: The E2A transcription factors promote the development of thymus-seeding cells but it remains unknown whether these proteins play a role in T lymphocyte lineage specification or commitment. Here we showed that E2A proteins were required to promote T lymphocyte commitment from DN2 thymocytes and to extinguish their potential for alternative fates. E2A proteins functioned in DN2 cells to limit expression of Gata3, which encodes an essential T lymphocyte transcription factor whose ectopic expression can arrest T cell differentiation. Genetic, or siRNA-mediated, reduction of Gata3 rescued T cell differentiation in the absence of E2A and restricted the development of alternative lineages by limiting the expanded self-renewal potential in E2A(-/-) DN2 cells. Our data support a novel paradigm in lymphocyte lineage commitment in which the E2A proteins are necessary to limit the expression of an essential lineage specification and commitment factor in order to restrain self-renewal and prevent an arrest in differentiation.
    Blood 01/2013; 121(9). DOI:10.1182/blood-2012-08-449447 · 10.45 Impact Factor
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    ABSTRACT: Recent studies have identified a number of transcriptional regulators, including E2A, early B-cell factor 1 (EBF1), FOXO1, and paired box gene 5 (PAX5), that promote early B-cell development. However, how this ensemble of regulators mechanistically promotes B-cell fate remains poorly understood. Here we demonstrate that B-cell development in FOXO1-deficient mice is arrested in the common lymphoid progenitor (CLP) LY6D(+) cell stage. We demonstrate that this phenotype closely resembles the arrest in B-cell development observed in EBF1-deficient mice. Consistent with these observations, we find that the transcription signatures of FOXO1- and EBF1-deficient LY6D(+) progenitors are strikingly similar, indicating a common set of target genes. Furthermore, we found that depletion of EBF1 expression in LY6D(+) CLPs severely affects FOXO1 mRNA abundance, whereas depletion of FOXO1 activity in LY6D(+) CLPs ablates EBF1 transcript levels. We generated a global regulatory network from EBF1 and FOXO1 genome-wide transcription factor occupancy and transcription signatures derived from EBF1- and FOXO1-deficient CLPs. This analysis reveals that EBF1 and FOXO1 act in a positive feedback circuitry to promote and stabilize specification to the B-cell lineage.
    Proceedings of the National Academy of Sciences 12/2012; 109(51). DOI:10.1073/pnas.1211427109 · 9.67 Impact Factor
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    ABSTRACT: Despite great progress in identification of mesenchymal stem cells (MSCs) from bone marrow (BM), our knowledge on their in vivo cellular identity remains limited. We here report that cells expressing the transcription factor Ebf2 in the adult BM display characteristics of MSCs. The Ebf2(+) cells are highly clonal and physiologically quiescent. In vivo lineage-tracing experiments, single cell clone transplantations and in vitro differentiation assay revealed their self-renewal and multilineage differentiation capacity. Gene expression analysis of the freshly sorted Ebf2(+) cells demonstrated expression of genes previously reported to be associated with MSCs and co-expression of multiple lineage-associated genes in a single cell level. Thus, Ebf2 expression is not restricted to committed osteoblast progenitor cells but rather marks a multipotent mesenchymal progenitor cell population in adult mouse BM. These cells do not appear to be completely overlapping with the previous reported MSC populations. The findings provide new insights into the in vivo cellular identity and molecular properties of BM mesenchymal stem and progenitor cells.
    Molecular and Cellular Biology 11/2012; 33(4). DOI:10.1128/MCB.01287-12 · 4.78 Impact Factor
  • Mikael Sigvardsson
    Blood 11/2012; 120(18):3630-1. DOI:10.1182/blood-2012-09-455113 · 10.45 Impact Factor
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    ABSTRACT: To better understand the process of B-lymphocyte lineage restriction, we have investigated molecular and functional properties in early B-lineage cells from Pax-5-deficient animals crossed to a B-lineage-restricted reporter mouse, allowing us to identify B-lineage-specified progenitors independently of conventional surface markers. Pax-5 deficiency resulted in a dramatic increase in the frequency of specified progenitor B-cells marked by expression of a λ5 (Igll1) promoter-controlled reporter gene. Gene expression analysis of ex vivo isolated progenitor cells revealed that Pax-5 deficiency has a minor impact on B-cell specification. However, single-cell in vitro differentiation analysis of ex vivo isolated cells revealed that specified B-lineage progenitors still displayed a high degree of plasticity for development into NK or T lineage cells. In contrast, we were unable to detect any major changes in myeloid lineage potential in specified Pax-5-deficient cells. By comparison of gene expression patterns in ex vivo isolated Pax-5- and Ebf-1-deficient progenitors, it was possible to identify a set of B-cell-restricted genes dependent on Ebf-1 but not Pax-5, supporting the idea that B-cell specification and commitment is controlled by distinct regulatory networks.
    Proceedings of the National Academy of Sciences 09/2012; 109(39):15871-6. DOI:10.1073/pnas.1210144109 · 9.67 Impact Factor
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    ABSTRACT: Immune-induced prostaglandin E2 (PGE2) synthesis is critical for fever and other centrally elicited disease symptoms. The production of PGE2 depends on cyclooxygenase-2 and microsomal prostaglandin E synthase-1 (mPGES-1), but the identity of the cells involved has been a matter of controversy. We generated mice expressing mPGES-1 either in cells of hematopoietic or nonhematopoietic origin. Mice lacking mPGES-1 in hematopoietic cells displayed an intact febrile response to lipopolysaccharide, associated with elevated levels of PGE2 in the cerebrospinal fluid. In contrast, mice that expressed mPGES-1 only in hematopoietic cells, although displaying elevated PGE2 levels in plasma but not in the cerebrospinal fluid, showed no febrile response to lipopolysaccharide, thus pointing to the critical role of brain-derived PGE2 for fever. Immunohistochemical stainings showed that induced cyclooxygenase-2 expression in the brain exclusively occurred in endothelial cells, and quantitative PCR analysis on brain cells isolated by flow cytometry demonstrated that mPGES-1 is induced in endothelial cells and not in vascular wall macrophages. Similar analysis on liver cells showed induced expression in macrophages and not in endothelial cells, pointing at the distinct role for brain endothelial cells in PGE2 synthesis. These results identify the brain endothelial cells as the PGE2-producing cells critical for immune-induced fever.
    Endocrinology 08/2012; 153(10):4849-61. DOI:10.1210/en.2012-1375 · 4.50 Impact Factor
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    ABSTRACT: Aging causes profound effects on the hematopoietic stem cell (HSC) pool, including an altered output of mature progeny and enhanced self-propagation of repopulating-defective HSCs. An important outstanding question is whether HSCs can be protected from aging. The signal adaptor protein LNK negatively regulates hematopoiesis at several cellular stages. It has remained unclear how the enhanced sensitivity to cytokine signaling caused by LNK deficiency affects hematopoiesis upon aging. Our findings demonstrate that aged LNK(-/-) HSCs displayed a robust overall reconstitution potential and gave rise to a hematopoietic system with a balanced lineage distribution. Although aged LNK(-/-) HSCs displayed a distinct molecular profile in which reduced proliferation was central, little or no difference in the proliferation of aged LNK(-/-) HSCs was observed after transplantation when compared to aged WT HSCs. This coincided with equal telomere maintenance in WT and LNK(-/-) HSCs. Collectively, our studies suggest that enhanced cytokine signaling can counteract functional age-related HSC decline.
    Aging cell 07/2012; 11(6). DOI:10.1111/j.1474-9726.2012.00863.x · 6.34 Impact Factor
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    ABSTRACT: HIV-1 infection enhances the expression of inhibitory molecules on T-cells leading to T-cell impairment. The signaling pathways underlying the regulation of inhibitory molecules and subsequent onset of T-cell impairment remains elusive. Herein, we showed that both autologous and allogeneic T-cells exposed to HIV-pulsed dendritic cells (DCs) upregulated cytotoxic T-lymphocyte antigen (CTLA-4), TNF-related apoptosis-inducing ligand (TRAIL), lymphocyte-activation gene-3 (LAG3), T-cell immunoglobulin mucin-3 (TIM-3), CD160, and certain suppression-associated transcription factors, such as B-lymphocyte induced maturation protein-1 (BLIMP-1), deltex homolog 1 (DTX1), and forkhead box P3 (FOXP3), leading to T-cell suppression. This induction was regulated by p38 mitogen-activated protein kinase/signal transducer and activator of transcription-3 (P38MAPK/STAT3) pathways as their blockade significantly abrogated expression of all the inhibitory molecules studied and a subsequent recovery in T-cell proliferation. Neither IL-6, or IL-10 nor growth factors known to activate STAT3 signaling events were responsible for STAT3 activation. Involvement of the P38MAPK/STAT3 pathways was evident as these proteins had a higher level of phosphorylation in the HIV-1 primed cells. Furthermore, blockade of viral CD4 binding and fusion significantly reduced the negative effects DCs imposed on primed T-cells. In conclusion, HIV-1 interaction with DCs modulated their functionality, causing them to trigger the activation of P38MAPK/STAT3 pathway in T-cells, which was responsible for the upregulation of inhibitory molecules.
    Molecular Medicine 07/2012; DOI:10.2119/molmed.2012.00103 · 4.51 Impact Factor
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    Hong Qian · Katarina Le Blanc · Mikael Sigvardsson
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    ABSTRACT: Despite significant progress in our understanding of mesenchymal stem cell (MSC) biology during recent years, much of the information is based on experiments using in vitro culture-selected stromal progenitor cells. Therefore, the natural cellular identity of MSCs remains poorly defined. Numerous studies have reported that CD44 expression is one of the characteristics of MSCs in both humans and mice; however, we here have prospectively isolated bone marrow stromal cell subsets from both human and mouse bone marrow by flow cytometry and characterized them by gene expression analysis and function assays. Our data provide functional and molecular evidence suggesting that primary mesenchymal stem and progenitor cells of bone marrow reside in the CD44− cell fraction in both mice and humans. The finding that these CD44− cells acquire CD44 expression after in vitro culture provides an explanation for the previous misconceptions concerning CD44 expression on MSCs. In addition, the other previous reported MSC markers, including CD73, CD146, CD271, and CD106/VCAM1, are also differentially expressed on those two cell types. Our microarray data revealed a distinct gene expression profile of the freshly isolated CD44− cells and the cultured MSCs generated from these cells. Thus, we conclude that bone marrow MSCs physiologically lack expression of CD44, highlighting the natural phenotype of MSCs and opening new possibilities to prospectively isolate MSCs from the bone marrow.
    Journal of Biological Chemistry 05/2012; 287(31):25795-807. DOI:10.1074/jbc.M112.339622 · 4.57 Impact Factor
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    ABSTRACT: Multiple transcription factors guide the development of mature functional natural killer (NK) cells, yet little is known about their function. We used global gene expression and genome-wide binding analyses combined with developmental and functional studies to unveil three roles for the ETS1 transcription factor in NK cells. ETS1 functions at the earliest stages of NK cell development to promote expression of critical transcriptional regulators including T-BET and ID2, NK cell receptors (NKRs) including NKp46, Ly49H, and Ly49D, and signaling molecules essential for NKR function. As a consequence, Ets1(-/-) NK cells fail to degranulate after stimulation through activating NKRs. Nonetheless, these cells are hyperresponsive to cytokines and have characteristics of chronic stimulation including increased expression of inhibitory NKRs and multiple activation-associated genes. Therefore, ETS1 regulates a broad gene expression program in NK cells that promotes target cell recognition while limiting cytokine-driven activation.
    Immunity 05/2012; 36(6):921-32. DOI:10.1016/j.immuni.2012.04.006 · 21.56 Impact Factor
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    ABSTRACT: Recent studies have identified a number of transcriptional regulators, including E proteins, EBF1, FOXO1, and PAX5, that act together to orchestrate the B-cell fate. However, it still remains unclear as to how they are linked at the earliest stages of B-cell development. Here, we show that lymphocyte development in HEB-ablated mice exhibits a partial developmental arrest, whereas B-cell development in E2A(+/-)HEB(-/-) mice is completely blocked at the LY6D(-) common lymphoid progenitor stage. We show that the transcription signatures of E2A- and HEB-ablated common lymphoid progenitors significantly overlap. Notably, we found that Foxo1 expression was substantially reduced in the LY6D(-) HEB- and E2A-deficient cells. Finally, we show that E2A binds to enhancer elements across the FOXO1 locus to activate Foxo1 expression, linking E2A and FOXO1 directly in a common pathway. In summary, the data indicate that the earliest event in B-cell specification involves the induction of FOXO1 expression and requires the combined activities of E2A and HEB.
    Proceedings of the National Academy of Sciences 10/2011; 108(42):17402-7. DOI:10.1073/pnas.1111766108 · 9.67 Impact Factor
  • Eva Welinder · Josefine Ahsberg · Mikael Sigvardsson
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    ABSTRACT: Even though B-lymphocyte development is one of the best understood models for cell differentiation in the hematopoetic system, recent advances in cell sorting and functional genomics has increased this understanding further. This has suggested that already early lymphoid primed multipotent progenitor cells (LMPPs) express low levels of lymphoid restricted transcripts. The expression of these genes becomes more pronounced when cells enter the FLT-3/IL-7 receptor positive common lymphoid progenitor (CLP) stage. However, the expression of B-lineage specific genes is limited to a B-cell restricted Ly6D surface positive subpopulation of the CLP compartment. The gene expression patterns also reflect differences in lineage potential and while Ly6D negative FLT-3/IL-7 receptor positive cells represents true CLPs with an ability to generate B/T and NK cells, the Ly6D positive cells lack NK cell potential and display a reduced T-cell potential in vivo. These recent findings suggest that the CLP compartment is highly heterogenous and that the point of no return in B-cell development may occur already in B220(-)CD19(-) cells. These findings have allowed for a better understanding of the interplay between transcription factors like EBF-1, PAX-5 and E47, all known as crucial for normal B-cell development. In this review, we aim to provide a comprehensive overview of B-cell fate specification and commitment based on the recent advances in the understanding of molecular networks as well as functional properties of early progenitor populations.
    Seminars in Immunology 09/2011; 23(5):335-40. DOI:10.1016/j.smim.2011.08.005 · 5.17 Impact Factor

Publication Stats

5k Citations
835.26 Total Impact Points


  • 2007–2015
    • Linköping University
      • Department of Clinical and Experimental Medicine (IKE)
      Linköping, Östergötland, Sweden
  • 2009–2013
    • Mid Sweden University
      Härnösand, Västernorrland, Sweden
  • 2010
    • University of Toronto
      • Department of Immunology
      Toronto, Ontario, Canada
  • 1993–2008
    • Lund University
      • • Department of Experimental Medical Science
      • • Stem Cell Center
      • • Department of Immunotechnology
      Lund, Skåne, Sweden
  • 1997
    • Howard Hughes Medical Institute
      Ашбърн, Virginia, United States