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  • The American Association of Immunologists  (3)
  • 1
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 184, No. 3 ( 2010-02-01), p. 1536-1542
    Abstract: Calcium (Ca2+) signaling in T lymphocytes is essential for a variety of functions, including the regulation of differentiation, gene transcription, and effector functions. A major Ca2+ entry pathway in nonexcitable cells, including T cells, is store-operated Ca2+ entry (SOCE), wherein depletion of intracellular Ca2+ stores upon receptor stimulation causes subsequent influx of extracellular Ca2+ across the plasma membrane. Stromal interaction molecule (STIM) 1 is the Ca2+ sensor in the endoplasmic reticulum, which controls this process, whereas the other STIM isoform, STIM2, coregulates SOCE. Although the contribution of STIM molecules and SOCE to T lymphocyte function is well studied in vitro, their significance for immune processes in vivo has remained largely elusive. In this study, we studied T cell function in mice lacking STIM1 or STIM2 in a model of myelin-oligodendrocyte glycoprotein (MOG35–55)-induced experimental autoimmune encephalomyelitis (EAE). We found that STIM1 deficiency significantly impaired the generation of neuroantigen-specific T cell responses in vivo with reduced Th1/Th17 responses, resulting in complete protection from EAE. Mice lacking STIM2 developed EAE, but the disease course was ameliorated. This was associated with a reduced clinical peak of disease. Deficiency of STIM2 was associated with an overall reduced proliferative capacity of lymphocytes and a reduction of IFN-γ/IL-17 production by neuroantigen-specific T cells. Neither STIM1 nor STIM2 deficiency altered the phenotype or function of APCs. These findings reveal a crucial role of STIM-dependent pathways for T cell function and activation under autoimmune inflammatory conditions, establishing them as attractive new molecular therapeutic targets for the treatment of inflammatory and autoimmune disorders.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
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    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2010
    detail.hit.zdb_id: 1475085-5
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  • 2
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 208, No. 7 ( 2022-04-01), p. 1729-1741
    Abstract: Recent evidence suggests interaction of platelets with dendritic cells (DCs), while the molecular mechanisms mediating this heterotypic cell cross-talk are largely unknown. We evaluated the role of integrin Mac-1 (αMβ2, CD11b/CD18) on DCs as a counterreceptor for platelet glycoprotein (GP) Ibα. In a dynamic coincubation model, we observed interaction of human platelets with monocyte-derived DCs, but also that platelet activation induced a sharp increase in heterotypic cell binding. Inhibition of CD11b or GPIbα led to significant reduction of DC adhesion to platelets in vitro independent of GPIIbIIIa, which we confirmed using platelets from Glanzmann thrombasthenia patients and transgenic mouse lines on C57BL/6 background (GPIbα−/−, IL4R-GPIbα-tg, and muMac1 mice). In vivo, inhibition or genetic deletion of CD11b and GPIbα induced a significant reduction of platelet-mediated DC adhesion to the injured arterial wall. Interestingly, only intravascular antiCD11b inhibited DC recruitment, suggesting a dynamic DC–platelet interaction. Indeed, we could show that activated platelets induced CD11b upregulation on Mg2+-preactivated DCs, which was related to protein kinase B (Akt) and dependent on P-selectin and P-selectin glycoprotein ligand 1. Importantly, specific pharmacological targeting of the GPIbα–Mac-1 interaction site blocked DC–platelet interaction in vitro and in vivo. These results demonstrate that cross-talk of platelets with DCs is mediated by GPIbα and Mac-1, which is upregulated on DCs by activated platelets in a P-selectin glycoprotein ligand 1–dependent manner.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    RVK:
    RVK:
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2022
    detail.hit.zdb_id: 1475085-5
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  • 3
    In: The Journal of Immunology, The American Association of Immunologists, Vol. 202, No. 1_Supplement ( 2019-05-01), p. 126.25-126.25
    Abstract: Beyond the superficial function of blood coagulation, platelets play an important role in the genesis of vascular inflammatory processes. Interestingly, platelets express the complement receptor C3aR. Here, we examine the role of the complement receptor C3aR on platelets for platelet function and in diseases. Methods We detected the expression of C3aR on murine and human platelets using western blot and flow cytometry. We examined proteins, that are in close connection to the C3aR receptor on platelets by mass spectrometry to elucidate the intracellular signaling. We examined the role of the platelet C3aR for platelet function using different platelet function tests. To investigate the relevance of our findings in vivo, we made use of mice that are deficient for C3aR. After performing bleeding time and intravital microscopy experiments, we induced myocardial infarction and stroke in knockout animals. Results We found that C3aR on platelets plays an important role in platelet function and thrombus formation. We discovered that the complement activation fragment C3a regulates bleeding time after tail injury and thrombosis using C3aR−/− mice or C3−/− mice with re-injection of C3a. After induction of a myocardial infarction or stroke in mice, C3aR−/− mice showed a better outcome in comparison to WT mice. When analyzing the intracellular signaling, we discovered that those effects were PI3 kinase and Rap-1 dependent. Conclusions Taken together, we identified the C3a receptor on platelets as an important player in platelet function and thrombus formation. Linking the systems of innate immunology and hemostasis, the C3a receptor on platelets could be a possible therapeutic target in diseases featuring thromboinflammation.
    Type of Medium: Online Resource
    ISSN: 0022-1767 , 1550-6606
    RVK:
    RVK:
    Language: English
    Publisher: The American Association of Immunologists
    Publication Date: 2019
    detail.hit.zdb_id: 1475085-5
    Location Call Number Limitation Availability
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