Biomedical subjects

Ken Shortman

Publications and source records attributed to Ken Shortman.

46 records · Page 3Linked 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

Developmental kinetics and lifespan of dendritic cells in mouse lymphoid organs.

The labeling kinetics of 5 dendritic cell (DC) subtypes within the lymphoid organs of healthy laboratory mice during continuous administration of bromodeoxyuridine (BrdU) was determined to investigate developmental relationships and determine turnover rates. Individual DC subtypes behaved as products of separate developmental streams, at least as far back as their dividing precursors. The rate of labeling varied with the lymphoid organ and the DC subtype. Labeling was faster overall in spleen and mesenteric lymph nodes (LNs) and slower in thymus and skin-draining LNs. The CD8(+) DC subtype displayed the most rapid turnover, with a uniformly short (3-day) lifespan in spleen but with distinct short-lived and longer-lived subgroups in thymus. All the skin-derived DCs in LNs showed delayed and slow BrdU labeling, indicating a long overall lifespan; however, this was shown to reflect a long residence time in skin rather than a long-duration presenting antigen in the draining LN. Epidermal-derived Langerhans DCs displayed longer BrdU labeling lag and slower overall turnover than the dermal-derived DCs, and the movement of fluorescent Langerhans DC from skin to LN was slower than that of dermal DCs following skin painting with a fluorescent dye. However, once they arrived in lymphoid organs, all DCs present in healthy, uninfected mice displayed a rapid turnover, and this turnover was even faster after antigenic or microbial product stimulation.

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

CD36 is differentially expressed by CD8+ splenic dendritic cells but is not required for cross-presentation in vivo.

Cross-presentation allows the processing of Ags from donor cells into the MHC class I presentation pathway of dendritic cells (DCs). This is important for the generation of cytotoxic T cell immunity and for induction of self tolerance. Apoptotic cells are reported to be efficient targets for cross-presentation, and in vitro studies using human DCs have implicated CD36 in their capture. In support of a role for CD36 in cross-presentation, we show that this molecule is differentially expressed by CD8(+) splenic DCs, which previously have been identified as responsible for cross-presentation in the mouse. Three different cross-presentation models were examined for their dependence on CD36. These included cross-priming to OVA-coated spleen cells and cross-tolerance to OVA transgenically expressed in the pancreatic islet beta cells under constitutive conditions or during beta cell destruction. In these models, CD36 knockout DCs were equivalent to wild-type DCs in their capacity to cross-present either foreign or self Ags, indicating that CD36 is not essential for cross-presentation of cellular Ags in vivo.

Animals↗

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

Constitutive, but not inflammatory, cross-presentation is disabled in the pancreas of young mice.

Peripheral antigens can be captured by APC and cross-presented to naive CD8(+) T cells. Notably, cross-presentation of pancreatic antigen is not seen in neonatal mice, although presentation of antigen expressed by the kidney is still intact. In this report, we examined why pancreatic antigens are not cross-presented in neonatal mice. First, we established that antigen expression was not limiting, as neonatal islets expressed as much antigen per cell as adult islets, and vastly more than neonatal renal cells. Next, we analyzed the APC subsets present in the lymph node draining the neonatal pancreas. No obvious population was absent. Finally, we examined whether cross-presentation occurred during inflammation. This showed that inflammation caused by CTL attack of islet tissue facilitated cross-presentation of antigens in neonatal mice. These data indicate that constitutive cross-presentation of islet antigens is inactive during neonatal life, but that under inflammatory conditions this antigen presentation pathway becomes available.

Adoptive Transfer↗

PubMed2002

Mouse and human dendritic cell subtypes.

Dendritic cells (DCs) collect and process antigens for presentation to T cells, but there are many variations on this basic theme. DCs differ in the regulatory signals they transmit, directing T cells to different types of immune response or to tolerance. Although many DC subtypes arise from separate developmental pathways, their development and function are modulated by exogenous factors. Therefore, we must study the dynamics of the DC network in response to microbial invasion. Despite the difficulty of comparing the DC systems of humans and mice, recent work has revealed much common ground.

Animals↗

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↗