Biomedical subjects

Hubertus Hochrein

Publications and source records attributed to Hubertus Hochrein.

27 records · Page 2Linked to original sources

PubMed2002

Dendritic cell precursor populations of mouse blood: identification of the murine homologues of human blood plasmacytoid pre-DC2 and CD11c+ DC1 precursors.

Immature and predendritic cells (pre-DCs) of human blood are the most readily accessible human DC sources available for study ex vivo. Murine homologues of human blood DCs have not been described. We report the isolation and characterization of 2 populations of precursor DCs in mouse blood. Mouse blood cells with the surface phenotype CD11c(lo)CD11b(-)CD45RA(hi) closely resemble human plasmacytoid cells (or pre-DC2) by morphology and function. On stimulation with oligonucleotides containing CpG motifs (CpG), these cells make large amounts of type 1 interferons and rapidly develop into DCs that bear CD8, though they may be distinct from the CD8(+) DCs in the unstimulated mouse. A second population of cells with the surface phenotype CD11c(+)CD11b(+)CD45RA(-) closely resembles the immediate precursors of pre-DC1, rapidly transforming into CD8(-) DCs after tumor necrosis factor-alpha (TNF-alpha) stimulation. These findings indicate the close relationship between human and mouse DCs, provided cells are obtained directly from equivalent source materials.

Animals↗

PubMed2002

Functionally distinct dendritic cell (DC) populations induced by physiologic stimuli: prostaglandin E(2) regulates the migratory capacity of specific DC subsets.

Migration of antigen (Ag)-loaded dendritic cells (DCs) from sites of infection into draining lymphoid tissues is fundamental to the priming of T-cell immune responses. We evaluated monocyte-derived DCs (MoDCs) and peripheral blood DCs (PBDCs) to respond to proinflammatory mediators, CD40L, and intact bacteria. All classes of stimuli induced DC phenotypic maturation. However, for MoDCs, only prostaglandin E(2) (PGE(2))-containing stimuli induced migratory-type DCs. Thus, immature MoDCs that encountered proinflammatory cytokines or CD40L or intact bacteria in the presence of PGE(2) acquired migratory capacity but secreted low levels of cytokines. Conversely, MoDCs that encountered pathogens or CD40L alone become nonmigratory cytokine-secreting cells (proinflammatory type). Interestingly, both migratory- and proinflammatory-type DCs expressed equivalent levels of chemokine receptors, suggesting that the role of PGE(2) was to switch on migratory function. We demonstrate that PGE(2) induces migration via the E-prostanoid 2/E-prostanoid 4 (EP(2)/EP(4)) receptors and the cAMP pathway. Finally, migratory-type MoDCs stimulated T-cell proliferation and predominantly IL-2 secretion, whereas proinflammatory-type MoDCs induced IFN-gamma production. In contrast, CD1b/c(+) PBDC rapidly acquired migratory capacity irrespective of the class of stimulus encountered and secreted low levels of cytokines. This suggests that not all mature stages of DCs are destined to migrate to lymphoid organs and that the sequence in which stimuli are encountered significantly affects which functions are expressed. Thus, certain immature DC subsets recruited from the resting precursor pool may have multiple functional fates that play distinct roles during the induction and effector phases of the immune response. These findings have important implications for the clinical utility of DCs in immunotherapy.

CD40 Ligand↗

PubMed2002

Effects of administration of progenipoietin 1, Flt-3 ligand, granulocyte colony-stimulating factor, and pegylated granulocyte-macrophage colony-stimulating factor on dendritic cell subsets in mice.

We studied the effects of administration of several cytokines, including progenipoietin-1 (ProGP-1), Flt-3 ligand (FL), granulocyte colony-stimulating factor (G-CSF), and granulocyte-macrophage colony-stimulating factor in a pegylated form (pGM-CSF), on dendritic cell (DC) populations in mouse spleen. ProGP-1 produced the most striking increase in overall DC numbers, apparently more than its constituent FL and G-CSF components. However, the expansion in DC numbers was strongly subpopulation selective, with ProGP-1 and FL producing selective expansion of CD8+ DCs, whereas pGM-CSF produced selective expansion of CD8- DCs. Surprising differences were observed between the effects of murine and human recombinant FL preparations on murine DCs. Many of the biologic functions of the DC subpopulations expanded by cytokines remained intact, including the capacity of the ProGP-1- and FL-expanded CD8+ DCs to produce the T-helper-1-biasing cytokine interleukin 12 (IL-12). However, the expanded DCs from all but G-CSF-treated mice were deficient in the ability to make interferon gamma, and the CD8+ DCs produced with pGM-CSF treatment had an abrogated capacity to form bioactive IL-12. Such selective expansion of DC populations and alterations in their cytokine-secretion capacity have implications for clinical use of the studied cytokines in immune modulation.

Adjuvants, Immunologic↗

PubMed2002

IL-1 beta enhances CD40 ligand-mediated cytokine secretion by human dendritic cells (DC): a mechanism for T cell-independent DC activation.

CD40 ligand (CD40L) is a membrane-bound molecule expressed by activated T cells. CD40L potently induces dendritic cell (DC) maturation and IL-12p70 secretion and plays a critical role during T cell priming in the lymph nodes. IFN-gamma and IL-4 are required for CD40L-mediated cytokine secretion, suggesting that T cells are required for optimal CD40L activity. Because CD40L is rapidly up-regulated by non-T cells during inflammation, CD40 stimulation may also be important at the primary infection site. However, a role for T cells at the earliest stages of infection is unclear. The present study demonstrates that the innate immune cell-derived cytokine, IL-1beta, can increase CD40L-induced cytokine secretion by monocyte-derived DC, CD34(+)-derived DC, and peripheral blood DC independently of T cell-derived cytokines. Furthermore, IL-1beta is constitutively produced by monocyte-derived DC and monocytes, and is increased in response to intact Escherichia coli or CD40L, whereas neither CD34(+)-derived DC nor peripheral blood DC produce IL-1beta. Finally, DC activated with CD40L and IL-1beta induce higher levels of IFN-gamma secretion by T cells compared with DC activated with CD40L alone. Therefore, IL-1beta is the first non-T cell-derived cytokine identified that enhances CD40L-mediated activation of DC. The synergy between CD40L and IL-1beta highlights a potent, T cell-independent mechanism for DC activation during the earliest stages of inflammatory responses.

Adjuvants, Immunologic↗

PubMed2002

CpG-DNA aided cross-presentation of soluble antigens by dendritic cells.

For cross-presentation immature dendritic cells (DC) require enhanced antigen (Ag) uptake and a maturation signal to prime for MHC class I-restricted CTL responses in vivo. While immunostimulatory CpG-DNA provides, via TLR9, the maturation signal, CpG-DNA linked to Ag augments cellular Ag uptake. In this study we show that CpG-DNA ovalbumin (OVA) conjugates trigger in vivo peptide-specific CTL responses at tenfold lower Ag doses compared to a mixture of CpG-DNA plus OVA. We provide evidence that CpG-DNA-OVA conjugates shift OVA uptake by immature DC from the presumably inefficient fluid phase pinocytosis to efficient DNA receptor-mediated endocytosis. Since the DNA-binding receptor mediating endocytosis lacks any sequence specificity, cellular uptake of OVA conjugated with either stimulatory or non-stimulatory oligonucleotides (ODN) is equally enhanced. As a consequence cross-linking of OVA with either stimulatory or non-stimulatory DNA yields, via enhanced OVA uptake, efficient generation and presentation of the dominant OVA-CTL epitope SIINFEKL. However, only stimulatory CpG-ODN cross-linked to OVA provide the DC maturation signal required to trigger robust primary CTL responses towards the cross-presented MHC class I complexed T cell epitope SIINFEKL. Our studies show that stimulatory CpG-ODN linked to Ag fulfill a dual role: enhancement of Ag uptake yielding efficient Ag cross-presentation by DC and in addition, their activation into professional DC.

Adjuvants, Immunologic↗

PubMed2002

Human and mouse plasmacytoid dendritic cells.

By virtue of their enormous potential to produce type I interferons it is clear that plasmacytoid dendritic cells are major players in the host defense against viruses and various pathogens. Plasmacytoid dendritic cells were first identified in humans and very recently the mouse equivalents have been isolated. This review focuses, where possible, on a comparison between the cells in these two species. The mouse and human plasmacytoid DC are remarkably similar in surface phenotype and they display similar responses to pathogenic stimuli. The discovery of the mouse plasmacytoid dendritic cells has allowed for further biological properties of these cells to be investigated and it is now clear that they represent a long-lived family of cells that differentiate into novel dendritic cells upon microbiologic stimulation.

Animals↗

PubMed2002

LIF receptor signaling limits immune-mediated demyelination by enhancing oligodendrocyte survival.

Multiple sclerosis (MS) is a disabling inflammatory demyelinating disease of the central nervous system (CNS) that primarily affects young adults. Available therapies can inhibit the inflammatory component of MS but do not suppress progressive clinical disability. An alternative approach would be to inhibit mechanisms that drive the neuropathology of MS, which often includes the death of oligodendrocytes, the cells responsible for myelinating the CNS. Identification of molecular mechanisms that mediate the stress response of oligodendrocytes to optimize their survival would serve this need. This study shows that the neurotrophic cytokine leukemia inhibitory factor (LIF) directly prevents oligodendrocyte death in animal models of MS. We also demonstrate that this therapeutic effect complements endogenous LIF receptor signaling, which already serves to limit oligodendrocyte loss during immune attack. Our results provide a novel approach for the treatment of MS.

Amino Acid Sequence↗

PubMed2002

IFN-alpha enhances CD40 ligand-mediated activation of immature monocyte-derived dendritic cells.

Type I IFN are immune modulatory cytokines that are secreted during early stages of infection. Type I IFN bridge the innate and the adaptive immune system in humans and mice. We compared the capacity of type I and II IFN to induce the functional maturation of monocyte-derived dendritic cells (MoDC). Extending our earlier observation that type I IFN promote DC maturation, we report that these cytokines also enhance DC differentiation by augmenting CD40 ligand (CD40L)-induced cytokine secretion by MoDC. Type I IFN alone were poor inducers of MoDC maturation as compared with other stimuli. They up-regulated the expression of HLA-DR, CD80, CD86, partially CCR7 but not CD83, partially reduced antigen-uptake function, increased the levels of IL-12p35 mRNA, and prolonged surface expression of peptide-MHC class I complexes for presentation to cytotoxic T lymphocytes, but did not induce migration towards CCL21 chemokine. However, type I IFN were potent co-factors for CD40L-mediated function. Here, they enhanced CD40L-mediated IL-6, IL-10 and IL-12p70 secretion. Furthermore, when combined with IL-1beta and/or IL-4, IFN-alpha2a type I IFN increased CD40L-mediated IL-12p70 production by 2- to 3-fold, and biased the IL-12 p40/p70 ratio towards the IFN-gamma inducing p70 heterodimer, this correlating with higher levels of IFN-gamma secretion by allogeneic T cell subsets and NK cells. Our results suggest that the rapid expression of CD40L, IFN and IL-1beta at sites of infection and inflammation can act in concert on immature DC, thereby linking innate and adaptive immune responses. In this way, type I IFN play a dual role as DC maturation factors and enhancers of CD40L-mediated DC activation.

Adjuvants, Immunologic↗

PubMed2002

Hierarchy of susceptibility of dendritic cell subsets to infection by Leishmania major: inverse relationship to interleukin-12 production.

Dendritic cells (DCs) are professional antigen-presenting cells which initiate and regulate T-cell immune responses. Here we show that murine splenic DCs can be ranked on the basis of their ability to phagocytose and harbor the obligately intracellular parasite Leishmania major. CD4(+) CD8(-) DCs are the most permissive host cells for L. major amastigotes, followed by CD4(-) CD8(-) DCs; CD4(-) CD8(+) cells are the least permissive. However, the least susceptible CD4(-) CD8(+) DC subset was the best interleukin-12 producer in response to infection. Infection did not induce in any DC subset production of the proinflammatory cytokine gamma interferon and nitric oxide associated with the induction of Th1 responses. The number of parasites phagocytosed by DCs was low, no more than 3 organisms per cell, compared to more than 10 organisms per macrophage. In infected DCs, the parasites are located in a parasitophorous vacuole containing both major histocompatibility complex (MHC) class II and lysosome-associated membrane protein 1 molecules, similar to their location in the infected macrophage. The parasite-driven redistribution of MHC class II to this compartment indicates that infected DCs should be able to present parasite antigen.

Animals↗