title: Characterization of the interferon-producing cell in mice infected with Listeria monocytogenes.
abstract: Production of type I interferons (IFN-I, mainly IFNalpha and IFNbeta) is a hallmark of innate immune responses to all classes of pathogens. When viral infection spreads to lymphoid organs, the majority of systemic IFN-I is produced by a specialized "interferon-producing cell" (IPC) that has been shown to belong to the lineage of plasmacytoid dendritic cells (pDC). It is unclear whether production of systemic IFN-I is generally attributable to pDC irrespective of the nature of the infecting pathogen. We have addressed this question by studying infections of mice with the intracellular bacterium Listeria monocytogenes. Protective innate immunity against this pathogen is weakened by IFN-I activity. In mice infected with L. monocytogenes, systemic IFN-I was amplified via IFN-beta, the IFN-I receptor (IFNAR), and transcription factor interferon regulatory factor 7 (IRF7), a molecular circuitry usually characteristic of non-pDC producers. Synthesis of serum IFN-I did not require TLR9. In contrast, in vitro-differentiated pDC infected with L. monocytogenes needed TLR9 to transcribe IFN-I mRNA. Consistent with the assumption that pDC are not the producers of systemic IFN-I, conditional ablation of the IFN-I receptor in mice showed that most systemic IFN-I is produced by myeloid cells. Furthermore, results obtained with FACS-purified splenic cell populations from infected mice confirmed the assumption that a cell type with surface antigens characteristic of macrophages and not of pDC is responsible for bulk IFN-I synthesis. The amount of IFN-I produced in the investigated mouse lines was inversely correlated to the resistance to lethal infection. Based on these data, we propose that the engagement of pDC, the mode of IFN-I mobilization, as well as the shaping of the antimicrobial innate immune response by IFN-I differ between intracellular pathogens.
authors.affiliation: Max F. Perutz Laboratories, Department of Microbiology and Immunobiology, University of Vienna, Vienna, Austria.
authors.forename: Silvia
authors.initials: S
authors.lastname: Stockinger
authors.forename: Renate
authors.initials: R
authors.lastname: Kastner
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kernbauer
authors.forename: Andreas
authors.initials: A
authors.lastname: Pilz
authors.forename: Sandra
authors.initials: S
authors.lastname: Westermayer
authors.forename: Benjamin
authors.initials: B
authors.lastname: Reutterer
authors.forename: Didier
authors.initials: D
authors.lastname: Soulat
authors.forename: Gabriele
authors.initials: G
authors.lastname: Stengl
authors.forename: Claus
authors.initials: C
authors.lastname: Vogl
authors.forename: Theresa
authors.initials: T
authors.lastname: Frenz
authors.forename: Zoe
authors.initials: Z
authors.lastname: Waibler
authors.forename: Tadatsugu
authors.initials: T
authors.lastname: Taniguchi
authors.forename: Thomas
authors.initials: T
authors.lastname: Rülicke
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kalinke
authors.forename: Mathias
authors.initials: M
authors.lastname: Müller
authors.forename: Thomas
authors.initials: T
authors.lastname: Decker