| 1. |
- Alvarado-Kristensson, Maria, et al.
(författare)
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p38-MAPK signals survival by phosphorylation of caspase-8 and caspase-3 in human neutrophils
- 2004
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Ingår i: Journal of Experimental Medicine. - : Rockefeller University Press. - 0022-1007 .- 1540-9538. ; 199:4, s. 449-458
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Tidskriftsartikel (refereegranskat)abstract
- Neutrophil apoptosis occurs both in the bloodstream and in the tissue and is considered essential for the resolution of an inflammatory process. Here, we show that p38-mitogen-activated protein kinase (MAPK) associates to caspase-8 and caspase-3 during neutrophil apoptosis and that p38-MAPK activity, previously shown to be a survival signal in these primary cells, correlates with the levels of caspase-8 and caspase-3 phosphorylation. In in vitro experiments, immunoprecipitated active p38-MAPK phosphorylated and inhibited the activity of the active p20 subunits of caspase-8 and caspase-3. Phosphopeptide mapping revealed that these phosphorylations occurred on serine-364 and serine-150, respectively. Introduction of mutated (S150A), but not wild-type, TAT-tagged caspase-3 into primary neutrophils made the Fas-induced apoptotic response insensitive to p38-MAPK inhibition. Consequently, p38-MAPK can directly phosphorylate and inhibit the activities of caspase-8 and caspase-3 and thereby hinder neutrophil apoptosis, and, in so doing, regulate the inflammatory response.
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| 2. |
- Leandersson, Karin, et al.
(författare)
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A pTalpha-negative subpopulation of CD25+ TN thymocytes revealed by a transgenic marker.
- 2002
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Ingår i: Scandinavian Journal of Immunology. - : Wiley. - 1365-3083 .- 0300-9475. ; 55:2, s. 119-128
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Tidskriftsartikel (refereegranskat)abstract
- We have recently generated 5'lambda5-huTAC mice, which express the human CD25 (huTAC) gene under the control of the 5'-flanking region of the mouse lambda5-gene. The huTAC-transgene was expressed in pre-B cells but neither in mature B cells nor in T cells of these mice. In this report we demonstrate that the transgene is also transiently expressed by adult CD25+ CD3-CD4-CD8- (triple negative, TN) thymocytes and in fetal thymocytes. The huTAC+, in contrast to the huTAC- subpopulation of the CD44+CD25+ TN cells, was unexpectedly found not to express the pTalpha-gene. Still the huTAC+CD44+CD25+ TN cells reconstituted the development of both alphabeta and gammadelta lineage cells equally efficiently as the pTalpha-expressing huTAC- fraction, demonstrating that this pTalpha-negative subpopulation contained precursors for both T-cell lineages. Single cell reverse transcription-polymerase chain reaction (RT-PCR) experiments demonstrated that also in normal mice only a fraction of CD44+CD25+ and CD44-CD25+ TN cells expressed this gene. Taken together, these data indicate that huTAC transgene expression revealed a truly pTalpha-negative fraction of the CD44+CD25+ TN cells. The observation that not all precursors in the CD25+ TN population express the pTalpha-gene has important implications for the understanding of early T-cell development and T-cell lineage commitment.
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| 3. |
- Leandersson, Karin
(författare)
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Early events in T cell development
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- T cells constitute a heterogenous population of lymphocytes. Their unifying property is that they express surface bound antigen-receptors, called T cell receptors (TCRs). The TCR is a heterodimer composed of either TCRalpha and beta chain proteins (alphabeta TCR) or gamma and delta chain proteins (gammadelta TCR). Depending on which TCR isotype that is expressed, the T cells are divided into alphabeta T cells or gammadelta T cells. In contrast to other hematopoietic cells, T cells develop in an organ called the thymus. To become a mature T cell the thymocytes proceed through a differentiation program that is partially induced by the surrounding thymic epithelial cells. T cell development can be divided into an early and a late stage of differentiation. The purpose of the early stage is to provide the developing thymocytes with functional TCRs. This is mediated by rearrangements at the DNA level of the TCRbeta, gamma and delta genes. If the TCRbeta gene is functionally rearranged, it will pair with a protein called pTalpha to form the preTCR complex that assures rearrangements of the TCRalpha genes and differentiation into the alphabeta T cell lineage. On the other hand, if the TCRgamma and delta chain genes are rearranged functionally the thymocyte will deviate from the mainstream alphabeta T cell pathway to become a mature gammadelta T cell. Whereas conventional alphabeta T cell development is quite well understood today, that of unconventional alphabeta T cells and gammadelta T cells is not. This thesis concerns the early stages of T cell development. With the articles herein, we provide information about the role of the TCR and preTCR in alphabeta versus gammadelta T cell development. We have furthermore examined the expression and transcriptional regulation of the pTalpha gene. Together, these findings lead to a better understanding of the early events in T cell development.
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| 4. |
- Leandersson, Karin, et al.
(författare)
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Early TCR alpha beta expression promotes maturation of T cells expressing Fc epsilon RI gamma containing TCR/CD3 complexes
- 2001
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Ingår i: Journal of Immunology. - 1550-6606. ; 166:11, s. 6616-6624
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Tidskriftsartikel (refereegranskat)abstract
- In a previous study we presented data indicating that the expanded population of CD4(-)CD8(-) (DN) alphabeta T cells in TCRalpha-chain-transgenic mice was partially if not entirely derived from gammadelta T cell lineage cells. The development of both gammadelta T cells and DN alphabeta T cells is poorly understood; therefore, we thought it would be important to identify the immediate precursors of the transgene-induced DN alphabeta T cells. We have in this report studied the early T cell development in these mice and we show that the transgenic TCRalpha-chain is expressed by precursor thymocytes already at the CD3(-)CD4(-)CD8(-) (triple negative, TN) CD44(+)CD25(-) stage of development. Both by using purified precursor populations in reconstitution experiments and by analyzing fetal thymocyte development, we demonstrated that early TN precursors expressing endogenous TCRbeta-chains matured into DN alphabeta T cells at several stages of development. The genes encoding the gamma-chain of the high affinity receptor for IgE (FcepsilonRIgamma) and the CD3zeta protein were found to be reciprocally expressed in TN thymocytes such that during development the FcepsilonRIgamma expression decreased whereas CD3zeta expression increased. Furthermore, in a fraction of the transgene-induced DN alphabeta T cells the FcepsilonRIgamma protein colocalized with the TCR/CD3 complex. These data suggest that similarly to gammadelta T cells and NKT cells, precursors expressing the TCR early in the common alphabetagammadelta developmental pathway may use the FcepsilonRIgamma protein as a signaling component of the TCR/CD3 complex.
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| 5. |
- Leandersson, Karin, et al.
(författare)
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The pTalpha promoter and enhancer are direct targets for transactivation by E box-binding proteins.
- 2002
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Ingår i: European Journal of Immunology. - 1521-4141. ; 32:3, s. 911-920
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Tidskriftsartikel (refereegranskat)abstract
- The pre-Talpha (pTalpha[?]) gene encodes a protein that forms the pre-TCR together with the newly expressed TCR beta chain during a defined stage of early T cell development. The restricted expression of this gene has been suggested to depend on a promoter and an enhancer element containing E boxes, which are potential binding sites for basic helix-loop-helix (bHLH) proteins. We here report that increased expression of E47 and E12 mRNA in CD4(--)CD8(--)TCR(--) thymocytes correlates with the initiation of pTalpha[?] transcription. Furthermore, electrophoretic mobility shift assays suggested that E47 binds directly to both the pTalpha[?] promoter and enhancer in vitro. Ectopic expression of E47 in non-lymphoid HeLa cells resultedin a dose- and template-dependent activation of these control elements. In addition to this, ectopic expression of E47 in combination with the ets-protein Pu.1 and[?]/[?]or the Pu.1-interacting protein(Pip-1), resulted in a synergistic effect on the activity of the pTalpha[?] control elements. Thus, we suggest that E47, Pu.1 and Pip-1 are directly involved in the regulation of pTalpha expression inearly T cell development.
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| 6. |
- Rosendahl, A, et al.
(författare)
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Transforming growth factor-beta- and Activin-Smad signaling pathways are activated at distinct maturation stages of the thymopoeisis
- 2003
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Ingår i: International Immunology. - : Oxford University Press (OUP). - 1460-2377. ; 15:12, s. 1401-1414
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Tidskriftsartikel (refereegranskat)abstract
- Members of the transforming growth factor (TGF)-beta family play pivotal roles in the control of differentiation, proliferation and tolerance in peripheral T cells. Recently, they have been implicated in thymic selection, but their role is so far not well characterized. In the present study, we demonstrate that specific thymocyte populations are under the influence of either the TGF-beta and/or Activin pathway, and transduce signals into the nucleus via phosphorylated Smad2 (pSmad2). Thymocytes in the medulla and in the subcapsular zone expressed nuclear translocated pSmad2, a hallmark of active TGF-beta/Activin receptor signaling. When analyzed at the cellular level, the pSmad2(+) cells were confined to the double-negative (DN) and single-positive (SP) subpopulations. Moreover, the most immature DN thymocytes (CD44(+)CD25(-) and CD44(+)CD25(+)) expressed higher levels of pSmad2 compared to the more mature DN. In vitro stimulation demonstrated that pure CD44(+)CD25(-), CD44(+)CD25(+) and CD44(+)CD25(+) thymocytes respond to ActivinA, while the mature CD4(+) and CD8(+) SP thymocytes respond to TGF-beta stimulation measured as enhanced phosphorylation of Smad2. Double staining of pSmad2(+) cells with either the Activin type I receptor, ALK4, or the TGF-beta type I receptor, ALK5, demonstrated that pSmad2(+) DN cells exhibited high levels of immunoreactivity to ALK4 and moderate levels of immunoreactivity to the TGF-beta-responsive ALK5 receptor. In sharp contrast, the SP pSmad2(+) cells were predominately ALK5(+). Collectively, our results demonstrate that early and late thymocytes express pSmad2 in the nuclei in vivo. The functional experiments in vitro suggest that members of the TGF-beta family (TGF-beta or Activin) may play important non-redundant roles during different stages of thymopoiesis.
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