http://hdl.handle.net/10033/6893 Sat, 18 May 2013 23:54:46 GMT 2013-05-18T23:54:46Z http://hdl.handle.net/10033/288484 Title: Immunoglobulins drive terminal maturation of splenic dendritic cells. Authors: Zietara, Natalia; Łyszkiewicz, Marcin; Puchałka, Jacek; Pei, Gang; Gutierrez, Maximiliano Gabriel; Lienenklaus, Stefan; Hobeika, Elias; Reth, Michael; Martins dos Santos, Vitor A P; Krueger, Andreas; Weiss, Siegfried Abstract: Nature and physiological status of antigen-presenting cells, such as dendritic cells DCs, are decisive for the immune reactions elicited. Multiple factors and cell interactions have been described that affect maturation of DCs. Here, we show that DCs arising in the absence of immunoglobulins (Ig) in vivo are impaired in cross-presentation of soluble antigen. This deficiency was due to aberrant cellular targeting of antigen to lysosomes and its rapid degradation. Function of DCs could be restored by transfer of Ig irrespective of antigen specificity and isotype. Modulation of cross-presentation by Ig was inhibited by coapplication of mannan and, thus, likely to be mediated by C-type lectin receptors. This unexpected dependency of splenic DCs on Ig to cross-present antigen provides insights into the interplay between cellular and humoral immunity and the immunomodulatory capacity of Ig. Tue, 05 Feb 2013 00:00:00 GMT http://hdl.handle.net/10033/288484 2013-02-05T00:00:00Z http://hdl.handle.net/10033/269695 Title: Visualizing production of beta interferon by astrocytes and microglia in brain of La Crosse virus-infected mice. Authors: Kallfass, Carsten; Ackerman, Andreas; Lienenklaus, Stefan; Weiss, Siegfried; Heimrich, Bernd; Staeheli, Peter Abstract: Beta interferon (IFN-β) is a major component of innate immunity in mammals, but information on the in vivo source of this cytokine after pathogen infection is still scarce. To identify the cell types responsible for IFN-β production during viral encephalitis, we used reporter mice that express firefly luciferase under the control of the IFN-β promoter and stained organ sections with luciferase-specific antibodies. Numerous luciferase-positive cells were detected in regions of La Crosse virus (LACV)-infected mouse brains that contained many infected cells. Double-staining experiments with cell-type-specific markers revealed that similar numbers of astrocytes and microglia of infected brains were luciferase positive, whereas virus-infected neurons rarely contained detectable levels of luciferase. Interestingly, if a mutant LACV unable of synthesizing the IFN-antagonistic factor NSs was used for challenge, the vast majority of the IFN-β-producing cells in infected brains were astrocytes rather than microglia. Similar conclusions were reached in a second series of experiments in which conditional reporter mice expressing the luciferase reporter gene solely in defined cell types were infected with wild-type or mutant LACV. Collectively, our data suggest that glial cells rather than infected neurons represent the major source of IFN-β in LACV-infected mouse brains. They further indicate that IFN-β synthesis in astrocytes and microglia is differentially affected by the viral IFN antagonist, presumably due to differences in LACV susceptibility of these two cell types. Mon, 01 Oct 2012 00:00:00 GMT http://hdl.handle.net/10033/269695 2012-10-01T00:00:00Z http://hdl.handle.net/10033/244298 Title: Priming of natural killer cells by nonmucosal mononuclear phagocytes requires instructive signals from commensal microbiota. Authors: Ganal, Stephanie C; Sanos, Stephanie L; Kallfass, Carsten; Oberle, Karin; Johner, Caroline; Kirschning, Carsten; Lienenklaus, Stefan; Weiss, Siegfried; Staeheli, Peter; Aichele, Peter; Diefenbach, Andreas Abstract: Mononuclear phagocytes are an important component of an innate immune system perceived as a system ready to react upon encounter of pathogens. Here, we show that in response to microbial stimulation, mononuclear phagocytes residing in nonmucosal lymphoid organs of germ-free mice failed to induce expression of a set of inflammatory response genes, including those encoding the various type I interferons (IFN-I). Consequently, NK cell priming and antiviral immunity were severely compromised. Whereas pattern recognition receptor signaling and nuclear translocation of the transcription factors NF-κB and IRF3 were normal in mononuclear phagocytes of germ-free mice, binding to their respective cytokine promoters was impaired, which correlated with the absence of activating histone marks. Our data reveal a previously unrecognized role for postnatally colonizing microbiota in the introduction of chromatin level changes in the mononuclear phagocyte system, thereby poising expression of central inflammatory genes to initiate a powerful systemic immune response during viral infection. Fri, 27 Jul 2012 00:00:00 GMT http://hdl.handle.net/10033/244298 2012-07-27T00:00:00Z http://hdl.handle.net/10033/229672 Title: Identification of tumor-specific Salmonella Typhimurium promoters and their regulatory logic. Authors: Leschner, Sara; Deyneko, Igor V; Lienenklaus, Stefan; Wolf, Kathrin; Bloecker, Helmut; Bumann, Dirk; Loessner, Holger; Weiss, Siegfried Abstract: Conventional cancer therapies are often limited in effectiveness and exhibit strong side effects. Therefore, alternative therapeutic strategies are demanded. The employment of tumor-colonizing bacteria that exert anticancer effects is such a novel approach that attracts increasing attention. For instance, Salmonella enterica serovar Typhimurium has been used in many animal tumor models as well as in first clinical studies. These bacteria exhibit inherent tumoricidal effects. In addition, they can be used to deliver therapeutic agents. However, bacterial expression has to be restricted to the tumor to prevent toxic substances from harming healthy tissue. Therefore, we screened an S. Typhimurium promoter-trap library to identify promoters that exclusively drive gene expression in the cancerous tissue. Twelve elements could be detected that show reporter gene expression in tumors but not in spleen and liver. In addition, a DNA motif was identified that appears to be necessary for tumor specificity. Now, such tumor-specific promoters can be used to safely express therapeutic proteins by tumor-colonizing S. Typhimurium directly in the neoplasia. Sun, 01 Apr 2012 00:00:00 GMT http://hdl.handle.net/10033/229672 2012-04-01T00:00:00Z