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Hubertus Hochrein

Publications and source records attributed to Hubertus Hochrein.

At least 19 recordsLinked to original sources
PubMed2006

Production of interferons by dendritic cells, plasmacytoid cells, natural killer cells, and interferon-producing killer dendritic cells.

The capacity of mouse spleen conventional dendritic cells (cDCs) and plasmacytoid dendritic cells (pDCs) to produce interferon-gamma (IFN-gamma) or IFN-alpha was assessed, and compared with that of natural killer (NK) cells and the recently identified interferon-producing killer dendritic cells (IKDCs), both of which are frequent contaminants in DC preparations. Fully developed cDCs or pDCs, if free of NK cells or IKDCs, showed little capacity for IFN-gamma production. However, an early developmental form of the CD4-8+ cDC subtype, and the Ly6C- Ly49Q- pDC subtype, both were able to produce moderate amounts of IFN-gamma, although less than IKDCs. In response to toll-like receptor 9 stimuli, both the Ly6C+ Ly49Q+ and the Ly6C- Ly49Q- pDC subtypes were effective producers of IFN-alpha. However, IKDCs, which efficiently produced IFN-gamma and showed immediate cytotoxicity on NK target cells, did not produce IFN-alpha under these conditions.

Animals↗
PubMed2006

CD8alpha+ dendritic cells are required for efficient entry of Listeria monocytogenes into the spleen.

In addition to their bridging function between innate and adaptive immunity, dendritic cells (DCs) may also contribute to primary resistance against infection. Here we analyzed the role of DCs during infection with Listeria monocytogenes by performing systemic in vivo depletion of these cells. We showed that CD8alpha(+) DCs were crucial for L. monocytogenes spreading and proliferation in the spleen. Efficient and rapid uptake of L. monocytogenes by CD8alpha(+) DCs required the small GTPase Rac1 and is a general characteristic of this DC subpopulation in filtering particles out of the blood. Thus, CD8alpha(+) DCs appear to play an important role for efficient bacterial entry into the spleen, which is of relevance for subsequent immune responses.

Animals↗
PubMed2006

The long-term but not the short-term antiviral effect of IFN-alpha depends on Flt3 ligand and pDC.

The cooperation between IFN-alpha/beta and FL, the ligand of Fms-like tyrosine kinase 3 (Flt3), plays an important role in the defense against herpes simplex virus type 1 (HSV-1) in neonates. Treatment of neonatal mice with recombinant IFN-alpha has a short-term, FL-independent and a long-term, FL-dependent protective effect against HSV-1. In mice lacking FL, neonatal resistance against HSV-1 is very low and DC numbers in the spleen are reduced. The treatment of these mice with rIFN-alpha at day 6 resulted in an increased resistance against infection with HSV-1 at day 7. In C57BL/6 mice, treatment with rIFN-alpha at birth induced both FL and plasmacytoid DC (pDC), resulting in enhanced resistance against HSV-1 at day 7. In contrast, in mice lacking FL, IFN-alpha treatment at birth did not influence the splenic cell composition and had no effect on viral protection. The transfer of pDC to mice lacking FL enhanced viral resistance. Therefore, the induction and function of pDC, normally controlled by IFN-alpha/beta and FL, are decisive for viral resistance in neonatal mice.

Animals↗
PubMed2006

Adenovirus efficiently transduces plasmacytoid dendritic cells resulting in TLR9-dependent maturation and IFN-alpha production.

BACKGROUND: Recombinant replication-deficient adenoviral vectors (recAd) are attractive candidates for DNA vaccination approaches because they are able to activate the innate and adaptive immune systems. Here we explore the ability of recAd to transduce and activate subsets of dendritic cells, namely plasmacytoid dendritic cells (pDC) and conventional dendritic cells (cDC). METHODS: DC were derived from bone marrow precursors in vitro with the help of FLT3-ligand. Sorted populations of pDC and cDC were infected with recAd at various multiplicities of infection. Transduction efficiency, phenotypic maturation and production of IFN-alpha as well as IL-6 were assessed. Additionally, activation of DC and induction of cytotoxic T lymphocytes (CTL) were determined in vivo. The role of Toll-like receptor (TLR) 9 in recAd recognition was investigated as it has previously been shown that DNA viruses are recognized via this receptor. RESULTS: RecAd can efficiently transduce pDC as well as cDC in vitro. Both DC subsets mature and produce IFN-alpha upon interaction with recAd. In the absence of TLR9, activation and cytokine production was only detected in cDC but not in pDC. Importantly, induction of CD8+ CTL following in vivo injection of recAd was similar in TRL9-deficient mice when compared with wildtype controls. CONCLUSIONS: RecAd can efficiently transduce and activate both pDC and cDC. pDC required TLR9 to detect the presence of recAd whereas cDC also recognized recAd independently of TLR9. These unique immunostimulatory properties support the future development of recombinant Ad as a vector for DNA vaccine approaches.

Adenoviridae↗
PubMed2005

Distinct roles for the NF-kappaB1 and c-Rel transcription factors in the differentiation and survival of plasmacytoid and conventional dendritic cells activated by TLR-9 signals.

Reticuloendotheliosis viral oncogene homolog/nuclear factor of kappa light polypeptide gene enhancer in B cells 1 (Rel/NF-kappaB) activation is a ubiquitous outcome of engaging Toll-like receptors (TLRs), yet the cell-type-specific functions of this pathway in response to particular microbial signals remain poorly defined. Here we show that NF-kappaB1 and C-Rel, Rel/NF-kappaB proteins induced in conventional dendritic cells (cDCs) and plasmacytoid dendritic cells (pDCs) by cytosine-phosphate-guanosine (CpG) DNA, a TLR-9 ligand, serve markedly different functions in these DC subsets. With the exception of impaired interleukin-12 (IL-12) production, cultured Nfkb1(-/-)C-Rel(-/-) cDCs responded relatively normally to CpG DNA. In contrast, CpG-treated Nfkb1(-/-)C-Rel(-/-) pDCs, which were still able to produce type I interferon and regulated on activation normal T-cell expressed and secreted (RANTES), but not IL-6 or IL-12, failed to acquire an activated dendritic phenotype and underwent apoptosis. Although the TLR-9-mediated death of Nfkb1(-/-)C-Rel(-/-) pDCs, which coincided with a failure to up-regulate the prosurvival proteins B-cell lymphoma apoptosis regulator xL (Bcl-x(L)) and A1, was blocked by Bcl-2 transgene expression, this inhibition of apoptosis still failed to rescue the differentiation defects. This indicated that these NF-kappaB transcription factors independently regulate TLR-9-mediated pDC morphogenesis and survival. Collectively, these findings establish that NF-kappaB1 and c-Rel, while largely dispensable for TLR-9-induced cDC activation, are critical for regulating differentiation and survival programs during pDC activation.

Animals↗
PubMed2005

Endosomal translocation of vertebrate DNA activates dendritic cells via TLR9-dependent and -independent pathways.

TLRs discriminate foreign from self via their specificity for pathogen-derived invariant ligands, an example being TLR9 recognizing bacterial unmethylated CpG motifs. In this study we report that endosomal translocation of CpG DNA via the natural endocytotic pathway is inefficient and highly saturable, whereas endosomal translocation of DNA complexed to the cationic lipid N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium methylsulfate (DOTAP) is not. Interestingly, DOTAP-mediated enhanced endosomal translocation of otherwise nonstimulatory vertebrate DNA or of certain noncanonical CpG motifs triggers robust dendritic cell activation in terms of both up-regulation of CD40/CD69 and cytokine production, such as type I IFN and IL-6. We report that the stimulatory activity of phosphorothioated noncanonical CpG oligodeoxynucleotides is TLR9 dependent, whereas phosphodiester DNA, such as vertebrate DNA, in addition trigger TLR9-independent pathways. We propose that the inefficiency of the natural route for DNA internalization hinders low affinity TLR9 ligands in endosomes to reach threshold concentrations required for TLR9 activation. Endosomal compartmentalization of TLR9 may thus reflect an evolutionary strategy to avoid TLR9 activation by self-DNA.

Adjuvants, Immunologic↗
PubMed2005

Pollen-associated phytoprostanes inhibit dendritic cell interleukin-12 production and augment T helper type 2 cell polarization.

Pollen grains induce allergies in susceptible individuals by release of allergens upon contact with mucosal membranes of the upper respiratory tract. We recently demonstrated that pollen not only function as allergen carriers but also as rich sources of bioactive lipids that attract cells involved in allergic inflammation such as neutrophils and eosinophils. Here we demonstrate that soluble factors from birch (Betula alba L.) pollen activate human dendritic cells (DCs) as documented by phenotypical and functional maturation and altered cytokine production. Betula alba L. aqueous pollen extracts (Bet.-APE) selectively inhibited interleukin (IL)-12 p70 production of lipopolysaccharide (LPS)- or CD40L-activated DC, whereas IL-6, IL-10, and TNFalpha remained unchanged. Presence of Bet.-APE during DC activation resulted in DC with increased T helper type 2 (Th2) cell and reduced Th1 cell polarizing capacity. Chemical analysis of Bet.-APE revealed the presence of phytoprostanes (dinor isoprostanes) with prostaglandin E(1)-, F(1)-, A(1)-, or B(1)-ring systems of which only E(1)-phytoprostanes dose dependently inhibited the LPS-induced IL-12 p70 release and augmented the Th2 cell polarizing capacity of DC. These results suggest that pollen-derived E(1)-phytoprostanes not only resemble endogenous prostaglandin E(2) structurally but also functionally in that they act as regulators that modulate human DC function in a fashion that favors Th2 cell polarization.

Betula↗
PubMed2005

Phagocytosis-induced apoptosis in macrophages is mediated by up-regulation and activation of the Bcl-2 homology domain 3-only protein Bim.

Cell death by apoptosis is important in immune cell homeostasis and in the defense against infectious microorganisms. The physiological event of uptake and intracellular destruction of bacteria is a powerful apoptotic stimulus to macrophages and neutrophil granulocytes. In this study, we provide a molecular analysis of phagocytosis-induced apoptosis. Apoptosis was blocked by Bcl-2 in a mouse macrophage cell line and in primary mouse macrophages. Analysis of the upstream mechanisms revealed that apoptosis was triggered by the Bcl-2 homology domain 3-only protein Bim/Bod. Contact with bacteria or bacterial components induced a strong increase in Bim-expression through TLR and MyD88. Inhibition of the MAPK p38 and JNK reduced both up-regulation of Bim and apoptosis. Phosphorylation of Bim was further observed in mouse macrophages, which appeared to be the result of TLR-dependent phosphatase inhibition. Although TLR-induced Bim was, unlike Bim in resting cells, not bound to the microtubuli cytoskeleton, the up-regulation of Bim was not sufficient to cause apoptosis. A second signal was required that was generated in the process of phagocytosis. Phagocytosis-induced apoptosis was strongly reduced in Bim(-/-) macrophages. These data provide the molecular context of a form of apoptosis that may serve to dispose of terminally differentiated phagocytes.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Activation of plasmacytoid dendritic cells.

Four years after the discovery of mouse plasmacytoid dendritic cells (pDC), pDC are still very much an 'enigmatic' cell type. It is clear that pDC are potent producers of type I IFN in response to viral, bacterial and even mammalian nucleotides. The role that they play in vivo before and after activation is still under scrutiny. This review concentrates on the pathways to activation of pDC, examining the activating ligands, receptors and signalling molecules that are known to be involved, and the relevance of these activation pathways to human disease.

Animals↗
PubMed2004

Herpes simplex virus type-1 induces IFN-alpha production via Toll-like receptor 9-dependent and -independent pathways.

Type I IFN production in response to the DNA virus herpes simplex virus type-1 (HSV-1) is essential in controlling viral replication. We investigated whether plasmacytoid dendritic cells (pDC) were the major tissue source of IFN-alpha, and whether the production of IFN-alpha in response to HSV-1 depended on Toll-like receptor 9 (TLR9). Total spleen cells or bone marrow (BM) cells, or fractions thereof, including highly purified pDC, from WT, TLR9, and MyD88 knockout mice were stimulated with known ligands for TLR9 or active HSV-1. pDC freshly isolated from both spleen and BM were the major source of IFN-alpha in response to oligodeoxynucleotides containing CpG motifs, but in response to HSV-1 the majority of IFN-alpha was produced by other cell types. Moreover, IFN-alpha production by non-pDC was independent of TLR9. The tissue source determined whether pDC responded to HSV-1 in a strictly TLR9-dependent fashion. Freshly isolated BM pDC or pDC derived from culture of BM precursors with FMS-like tyrosine kinase-3 ligand, produced IFN-alpha in the absence of functional TLR9, whereas spleen pDC did not. Heat treatment of HSV-1 abolished maturation and IFN-alpha production from all TLR9-deficient DC but not WT DC. Thus pDC and non-pDC produce IFN-alpha in response to HSV-1 via both TLR9-independent and -dependent pathways.

Adaptor Proteins, Signal Transducing↗
PubMed2004

The major surface protein of Wolbachia endosymbionts in filarial nematodes elicits immune responses through TLR2 and TLR4.

More than 150 million humans in tropical countries are infected by filarial nematodes which harbor intracellular bacterial endosymbionts of the genus Wolbachia (Rickettsiales). These bacteria have been implicated in adverse effects of drug treatment in filariasis. The present study provides evidence that purified major Wolbachia surface protein (rWSP) acts as an inducer of the innate immune system through TLR2 and TLR4: 1) recombinant, stringently purified rWSP elicited the release of TNF-alpha, IL-12, and IL-8 from cultured blood cells of both Onchocerca volvulus-infected and uninfected people; 2) the inflammatory response to rWSP challenge was TLR2- and TLR4-dependent as demonstrated with TLR-transfected fibroblastoid cells, as well as macrophages and dendritic cells from functional TLR-deficient mice; 3) blood cells of onchocerciasis patients exposed to rWSP also generated down-regulating mediators IL-10 and PGE(2) after 6 days of culture; 4) furthermore, rWSP-reactive IgG1 Abs were present in sera of O. volvulus-infected people but not in those of uninfected Europeans. The lack of rWSP-reactive IgE and IgG4 in serum indicated a bias toward a Th1-type adaptive immune response. Abs against rWSP stained endobacteria in living and degenerating adult O. volvulus filariae, tissue microfilariae and host tissue macrophages that apparently had engulfed microfilariae. Thus, filarial helminths, through products of their endobacteria such as WSP, acquire characteristics of a typical microbial pathogen inducing immune responses via TLR2 and TLR4.

Adolescent↗
PubMed2004

A regulatory role for CD37 in T cell proliferation.

CD37 is a leukocyte-specific protein belonging to the tetraspanin superfamily. Previously thought to be predominantly a B cell molecule, CD37 is shown in this study to regulate T cell proliferation. CD37-deficient (CD37(-/-)) T cells were notably hyperproliferative in MLR, in response to Con A, or CD3-TCR engagement particularly in the absence of CD28 costimulation. Hyperproliferation was not due to differences in memory to naive T cell ratios in CD37(-/-) mice, apoptosis, or TCR down-modulation. Division cycle analyses revealed CD37(-/-) T cells to enter first division earlier than wild-type T cells. Importantly, proliferation of CD37(-/-) T cells was preceded by enhanced early IL-2 production. We hypothesized CD37 to be involved in TCR signaling and this was supported by the observation that CD4/CD8-associated p56(Lck) kinase activity was increased in CD37(-/-) T cells. Remarkably, CD37 cross-linking on human T cells transduced signals that led to complete inhibition of CD3-induced proliferation. In the presence of CD28 costimulation, CD37 engagement still significantly reduced proliferation. Taken together, these results demonstrate a regulatory role for CD37 in T cell proliferation by influencing early events of TCR signaling.

Animals↗
PubMed2004

Species-specific recognition of single-stranded RNA via toll-like receptor 7 and 8.

Double-stranded ribonucleic acid (dsRNA) serves as a danger signal associated with viral infection and leads to stimulation of innate immune cells. In contrast, the immunostimulatory potential of single-stranded RNA (ssRNA) is poorly understood and innate immune receptors for ssRNA are unknown. We report that guanosine (G)- and uridine (U)-rich ssRNA oligonucleotides derived from human immunodeficiency virus-1 (HIV-1) stimulate dendritic cells (DC) and macrophages to secrete interferon-alpha and proinflammatory, as well as regulatory, cytokines. By using Toll-like receptor (TLR)-deficient mice and genetic complementation, we show that murine TLR7 and human TLR8 mediate species-specific recognition of GU-rich ssRNA. These data suggest that ssRNA represents a physiological ligand for TLR7 and TLR8.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Vaccination with plasmid DNA activates dendritic cells via Toll-like receptor 9 (TLR9) but functions in TLR9-deficient mice.

We analyzed whether the immunobiology of vaccinating plasmid DNA containing a transcription unit for OVA is influenced by immunostimulatory CpG motifs in the plasmid backbone. Indeed, plasmid DNA differentially activated in vitro myeloid and plasmacytoid dendritic cells (DCs) provided they expressed the CpG-DNA receptor, Toll-like receptor 9 (TLR9). Dependent on the DC subset, activation resulted in type 1 IFN production, while both DC subsets produced IL-6 and up-regulated expression of costimulatory molecules CD40 and CD86. In vivo, however, even upon repeated vaccination with plasmid DNA, priming of OVA-specific CTL and clonal expansion of SIINFEKL-specific CD8 T cells were equal in TLR9-positive and TLR9- or MyD88-negative mice. Overall, these results negate a dominant role of CpG-DNA/TLR9 interactions in long-term vaccination protocols.

Adjuvants, Immunologic↗
PubMed2003

Cutting edge: Toll-like receptor 9 expression is not required for CpG DNA-aided cross-presentation of DNA-conjugated antigens but essential for cross-priming of CD8 T cells.

Covalent linkage of immunostimulatory CpG DNA to OVA results in CpG DNA-aided cross-presentation of OVA by dendritic cells (DCs). In vivo, cross-presentation is conditional for cross-priming of OVA-specific CD8 T cells. In this study, we investigated the involvement of the CpG DNA receptor Toll-like receptor (TLR)9 in CpG DNA-aided cross-presentation and cross-priming. Although CpG DNA-aided cross-presentation is not altered in TLR9-deficient cells, TLR9 is required for maturation of APC allowing cross-priming, as resulting in CTL function. These findings imply that TLR9 does not trigger endocytosis of CpG-OVA conjugates, but activates DCs downstream of endocytosis.

Adjuvants, Immunologic↗
PubMed2003

The Toll-like receptor 7 (TLR7)-specific stimulus loxoribine uncovers a strong relationship within the TLR7, 8 and 9 subfamily.

Loxoribine (7-allyl-7,8-dihydro-8-oxo-guanosine) acts as synthetic adjuvant in anti-tumor responses. Here we first demonstrate that loxoribine activates cells of the innate immune system selectively via the Toll-like receptor (TLR) 7/MyD88-dependent signaling pathway. TLR7- and MyD88-deficient immune cells fail to proliferate or produce cytokines in response to loxoribine, and genetic complementation of TLR7-deficient cells with murine or human TLR7 confers responsiveness. Subsequently we show that cellular activation by loxoribine and resiquimod (R-848), a stimulus for TLR7 and TLR8, depends on acidification and maturation of endosomes and targets MyD88 to vesicular structures with lysosomal characteristics. This mode of TLR7 and TLR8 action resembles CpG-DNA-driven TLR9 activation. We thus conclude that TLR7, 8 and 9 form a functional subgroup within the TLR family that recognizes pathogen-associated molecular patterns in endosomal/lysosomal compartments.

Adaptor Proteins, Signal Transducing↗
PubMed2002

Mouse plasmacytoid cells: long-lived cells, heterogeneous in surface phenotype and function, that differentiate into CD8(+) dendritic cells only after microbial stimulus.

The CD45RA(hi)CD11c(int) plasmacytoid predendritic cells (p-preDCs) of mouse lymphoid organs, when stimulated in culture with CpG or influenza virus, produce large amounts of type I interferons and transform without division into CD8(+)CD205(-) DCs. P-preDCs express CIRE, the murine equivalent of DC-specific intercellular adhesion molecule 3 grabbing nonintegrin (DC-SIGN). P-preDCs are divisible by CD4 expression into two subgroups differing in turnover rate and in response to Staphylococcus aureus. The kinetics of bromodeoxyuridine labeling and the results of transfer to normal recipient mice indicate that CD4(-) p-preDCs are the immediate precursors of CD4(+) p-preDCs. Similar experiments indicate that p-preDCs are normally long lived and are not the precursors of the short-lived steady-state conventional DCs. However, in line with the culture studies on transfer to influenza virus-stimulated mice the p-preDCs transform into CD8(+)CD205(-) DCs, distinct from conventional CD8(+)CD205(+) DCs. Hence as well as activating preexistant DCs, microbial infection induces a wave of production of a new DC subtype. The functional implications of this shift in the DC network remain to be determined.

Animals↗