Julia Ludwig

Universität Heidelberg, Heidelburg, Baden-Württemberg, Germany

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Publications (4)21.81 Total impact

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    ABSTRACT: Keratinocytes play a pivotal role in the regulation of immune responses but the impact of antigen-presentation by these cells is still poorly understood, particularly in a situation where the antigen will be presented only in adult life. Here, we generated a transgenic mouse model in which keratinocytes exclusively present a myelin basic protein (MBP) peptide covalently linked to the MHC class II β-chain, solely under inflammatory conditions. In these mice, inflammation caused by epicutaneous contact sensitizer treatment resulted in keratinocyte-mediated expansion of MBP-specific CD4(+) T cells in the skin. Moreover, repeated contact sensitizer application preceding a systemic MBP immunization reduced the reactivity of the respective CD4(+) T cells and lowered the symptoms of the resulting experimental autoimmune encephalomyelitis. This down-regulation was CD4(+) T cell mediated and dependent on the presence of the immune modulator Dickkopf-3. Thus, presentation of a neo self-antigen by keratinocytes in the inflamed, adult skin can modulate CD4(+) T cell auto-aggression at a distal organ.In parallel to the DPCP skin treatments, 0.5 mg of the anti-Dkk3 4.22 mAb (Papatriantafyllou et al., 2012) in 200 μl PBS was applied i.p., 3 times, each one week apart.Journal of Investigative Dermatology accepted article preview online, 02 April 2015. doi:10.1038/jid.2015.130.
    Journal of Investigative Dermatology 04/2015; 135(8). DOI:10.1038/jid.2015.130 · 7.22 Impact Factor
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    ABSTRACT: The adaptive immune system protects organisms from harmful environmental insults. In parallel, regulatory mechanisms control immune responses in order to assure preservation of organ integrity. Yet, molecules involved in the control of T-cell responses in peripheral tissues are poorly characterized. Here, we investigated the function of Dickkopf-3 in the modulation of local T-cell reactivity. Dkk3 is a secreted, mainly tissue-derived protein with highest expression in organs considered as immune-privileged such as the eye, embryo, placenta, and brain. While T-cell development and activation status in naïve Dkk3-deficient mice was comparable to littermate controls, we found that Dkk3 contributes to the immunosuppressive microenvironment that protects transplanted, class-I mismatched embryoid bodies from T-cell-mediated rejection. Moreover, genetic deletion or antibody-mediated neutralization of Dkk3 led to an exacerbated experimental autoimmune encephalomyelitis (EAE). This phenotype was accompanied by a change of T-cell polarization displayed by an increase of IFNγ-producing T cells within the central nervous system. In the wild-type situation, Dkk3 expression in the brain was up-regulated during the course of EAE in an IFNγ-dependent manner. In turn, Dkk3 decreased IFNγ activity and served as part of a negative feedback mechanism. Thus, our findings suggest that Dkk3 functions as a tissue-derived modulator of local CD4(+) and CD8(+) T-cell responses.
    Frontiers in Immunology 02/2015; 6:78. DOI:10.3389/fimmu.2015.00078
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    ABSTRACT: The mechanisms responsible for the generation of a mature B1 and B2 cell compartment are still poorly understood. In this study, we demonstrated that absence of Dickkopf-3 (DKK3) led to changes in the composition of the B cell compartment, which were due to an altered development and maintenance program of B cells. Development of B2 cells was impaired at the pre- and immature B cell stage, resulting in decreased numbers of follicular B cells in adult DKK3-deficient mice. Furthermore, DKK3 limited B1 cell self-maintenance in the periphery, by decreasing the survival and proliferation behavior of B1 cells. DKK3 may act via the BCR signaling pathway, as Ca(2+) influx upon BCR stimulation was increased and SiglecG, a molecule shown to inhibit Calcium signaling, was downregulated in the absence of DKK3. DKK3-deficient mice exhibited altered Ab responses and an increased secretion of the cytokine IL-10. Additionally, DKK3 limited autoimmunity in a model of systemic lupus erythematosus. In summary, we identified DKK3 as a novel modulator interfering with B cell fate as well as the maintenance program of B cells, leading to changes in B cell immune responses. Copyright © 2015 by The American Association of Immunologists, Inc.
    The Journal of Immunology 02/2015; 194(6). DOI:10.4049/jimmunol.1402160 · 4.92 Impact Factor
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    ABSTRACT: In healthy individuals, T cells react against incoming pathogens, but remain tolerant to self-antigens, thereby preventing autoimmune reactions. CD4 regulatory T cells are major contributors in induction and maintenance of peripheral tolerance, but a regulatory role has been also reported for several subsets of CD8 T cells. To determine the molecular basis of peripheral CD8 T-cell tolerance, we exploited a double transgenic mouse model in which CD8 T cells are neonatally tolerized following interaction with a parenchymal self-antigen. These tolerant CD8 T cells have regulatory capacity and can suppress T cells in an antigen-specific manner during adulthood. Dickkopf-3 (DKK3) was found to be expressed in the tolerant CD8 T cells and to be essential for the observed CD8 T-cell tolerance. In vitro, genetic deletion of DKK3 or blocking with antibodies restored CD8 T-cell proliferation and IL-2 production in response to the tolerizing self-antigen. Moreover, exogenous DKK3 reduced CD8 T-cell reactivity. In vivo, abrogation of DKK3 function reversed tolerance, leading to eradication of tumors expressing the target antigen and to rejection of autologous skin grafts. Thus, our findings define DKK3 as a immune modulator with a crucial role for CD8 T-cell tolerance.
    Proceedings of the National Academy of Sciences 01/2012; 109(5):1631-6. DOI:10.1073/pnas.1115980109 · 9.67 Impact Factor