The colony-stimulating factor 1 receptor is expressed on dendritic cells during differentiation and regulates their expansion

The lineage of dendritic cells (DC), and in particular their relationship to monocytes and macrophages, remains obscure. Furthermore, the requirement for the macrophage growth factor CSF-1 during DC homeostasis is unclear. Using a transgenic mouse in which the promoter for the CSF-1R (c-fms) directs the expression of enhanced GFP in cells of the myeloid lineage, we determined that although the c-fms promoter is inactive in DC precursors, it is up-regulated in all DC subsets during differentiation. Furthermore, plasmacytoid DC and all CD11c(high) DC subsets are reduced by 50-70% in CSF-1-deficient osteopetrotic mice, confirming that CSF-1 signaling is required for the optimal differentiation of DC in vivo. These data provide additional evidence that the majority of tissue DC is of myeloid origin during steady state and supports a close relationship between DC and macrophage biology in vivo.

Generation and maturation of dendritic cells for clinical application under serum-free conditions

Monocyte-derived dendritic cells (MoDCs) in clinical use for cancer immunotherapy are ideally generated in serum-free medium (SFM) with inclusion of a suitable maturation factor toward the end of the incubation period. Three good manfacturing practice (GMP) grade SFMs (AIM-V, X-VIVO 15, and X-VIVO 20) were compared with RPMI-1640, supplemented with 10% fetal bovine serum or 10% human serum. DCs generated for 7 days in SFM were less mature and secreted less interleukin (IL) 12p70 and IL-10 than DCs generated in 10% serum. DC yield was comparable in SFMs, and a greater proportion of cells was viable after maturation. Toll-like receptor (TLR) ligands were compared for their ability to induce cytokine secretion under serum-free conditions in the presence of interferon (IFN) gamma. With the exception of Poly I:C, TLR ligands stimulated high levels of IL-10 secretion. High levels of IL-12p70 were induced by two TLR4-mediated stimuli, lipopolysaccharide and Ribomunyl, a clinical-grade bacterial extract. When T-cell responses were compared in allogeneic mixed leukocyte reaction, DCs stimulated with Ribomunyl induced higher levels of IFN gamma than DCs stimulated with the cytokine cocktail: tumor necrosis factor-alpha, IL-1 beta, IL-6, and prostaglandin E-2. In the presence of IL-10 neutralizing antibodies, DC IL-12p70 production and T-cell IFN gamma were increased in vitro. Similarly, DCs stimulated with Ribomunyl, IFN gamma, and anti-IL-10 induced high levels of tetanus toxoid-specific T-cell proliferation and IFN gamma secretion. Thus, MoDCs generated ill SFM efficiently stimulate T-cell IFN gamma production after maturation in the presence of a clinical-grade TLR4 agonist and IL-10 neutralization.

Follicular dendritic cell sarcoma associated with Castelmans disease presenting in the oral cavity

Follicular dendritic cell sarcoma (FDCS) is a rare intermediate grade malignant neoplasm of reticular dendritic origin. Castleman’s disease (CD) represents a non-neoplastic lymphoproliferative disorder with various clinical and morphological features. FDCS has been reported to be associated with CD. In this article, we describe the first case of follicular dendritic cell sarcoma associated with Castleman’s disease presenting in the oral cavity. Copyright © 2005 Elsevier Ltd All rights reserved.

Systemic activation of dendritic cells by Toll-like receptor ligands or malaria infection impairs cross-presentation and anti-viral immunity

The mechanisms responsible for the immunosuppression associated with sepsis or some chronic blood infections remain poorly understood. Here we show that infection with a malaria parasite (Plasmodium berghei) or simple systemic exposure to bacterial or viral Toll-like receptor ligands inhibited cross-priming. Reduced cross-priming was a consequence of downregulation of cross-presentation by activated dendritic cells due to systemic activation that did not otherwise globally inhibit T cell proliferation. Although activated dendritic cells retained their capacity to present viral antigens via the endogenous major histocompatibility complex class I processing pathway, antiviral responses were greatly impaired in mice exposed to Toll-like receptor ligands. This is consistent with a key function for cross-presentation in antiviral immunity and helps explain the immunosuppressive effects of systemic infection. Moreover, inhibition of cross-presentation was overcome by injection of dendritic cells bearing antigen, which provides a new strategy for generating immunity during immunosuppressive blood infections.

Density and morphology of dendritic spines in mouse neocortex

Dendritic spines of pyramidal cells are the main postsynaptic targets of cortical excitatory synapses and as such, they are fundamental both in neuronal plasticity and for the integration of excitatory inputs to pyramidal neurons. There is significant variation in the number and density of dendritic spines among pyramidal cells located in different cortical areas and species, especially in primates. This variation is believed to contribute to functional differences reported among cortical areas. In this study, we analyzed the density of dendritic spines in the motor, somatosensory and visuo-temporal regions of the mouse cerebral cortex. Over 17,000 individual spines on the basal dendrites of layer III pyramidal neurons were drawn and their morphologies compared among these cortical regions. In contrast to previous observations in primates, there was no significant difference in the density of spines along the dendrites of neurons in the mouse. However, systematic differences in spine dimensions (spine head size and spine neck length) were detected, whereby the largest spines were found in the motor region, followed by those in the somatosensory region and those in visuo-temporal region. (c) 2005 IBRO. Published by Elsevier Ltd. All rights reserved.

IL10 and IL12B polymorphisms each influence IL-12p70 secretion by dendritic cells in response to LPS

Dendritic cells (DC) are the main producers of the cytokine IL-12p70, through which they play a direct role in the development of IFN-gamma-secreting Th1 cells, costimulation of CTL differentiation and NK-cell activation. In contrast, IL-10, which is also produced by DC, negatively regulates IL-12 production. IL-12p70 production varies widely between individuals, and several polymorphisms in the gene encoding IL-12p40 (IL12B) have been identified that influence susceptibility and severity of infectious, autoimmune and neoplastic disease. Here we show that polymorphisms not only of IL12B, but also in the IL10 promoter, influence IL-12p70 secretion by monocyte-derived DC in response to LPS. Although IL12B promoter homozygotes were prone to making more IL-12p70, presence of the IL10 high genotype restricted IL-12p70 production in these individuals. These observations provide a further genetic control of IL-12p70 regulation and emphasize the complexity of production of this cytokine. They also suggest genotypes that might influence the outcome of DC immunotherapy.

RNA Loading of Leukemic Antigens into Cord Blood–Derived Dendritic Cells for Immunotherapy

The manipulation of dendritic cells (DCs) ex vivo to present tumor-associated antigens for the activation and expansion of tumor-specific cytotoxic T lymphocytes (CTLs) attempts to exploit these cells’ pivotal role in immunity. However, significant improvements are needed if this approach is to have wider clinical application. We optimized a gene delivery protocol via electroporation for cord blood (CB) CD34+ DCs using in vitro–transcribed (IVT) mRNA. We achieved > 90% transfection of DCs with IVT-enhanced green fluorescent protein mRNA with > 90% viability. Electroporation of IVT-mRNA up-regulated DC costimulatory molecules. DC processing and presentation of mRNA-encoded proteins, as major histocompatibility complex/peptide complexes, was established by CTL assays using transfected DCs as targets. Along with this, we also generated specific antileukemic CTLs using DCs electroporated with total RNA from the Nalm-6 leukemic cell line and an acute lymphocytic leukemia xenograft. This significant improvement in DC transfection represents an important step forward in the development of immunotherapy protocols for the treatment of malignancy.

The key role of CD40 ligand in overcoming tumor-induced dendritic cell dysfunction

Overcoming dendritic cell (DC) dysfunction is a prerequisite for successful active immunotherapy against breast cancer. CD40 ligand (CD40L), a key molecule in the interface between T-lymphocytes and DCs, seems to be instrumental in achieving that goal. Commenting on our data that CD40L protects circulating DCs from apoptosis induced by breast tumor products, Lenahan and Avigan highlighted the potential of CD40L for immunotherapy. We expand on that argument by pointing to additional findings that CD40L not only rescues genuine DCs but also functionally improves populations of immature antigen-presenting cells that fill the DC compartment in patients with breast cancer.

The dendritic architecture of the cholinergic plexus in the rabbit retina: Selective labeling by glycine accumulation in the presence of sarcosine

The cholinergic amacrine cells in the rabbit retina slowly accumulate glycine to very high levels when the tissue is incubated with excess sarcosine (methylglycine), even though these cells do not normally contain elevated levels of glycine and do not express high-affinity glycine transporters. Because the sarcosine also depletes the endogenous glycine in the glycine-containing amacrine cells and bipolar cells, the cholinergic amacrine cells can be selectively labeled by glycine immunocytochemistry under these conditions. Incubation experiments indicated that the effect of sarcosine on the cholinergic amacrine cells is indirect: sarcosine raises the extracellular concentration of glycine by blocking its re-uptake by the glycinergic amacrine cells, and the excess glycine is probably taken-up by an unidentified low-affinity transporter on the cholinergic amacrine cells. Neurobiotin injection of the On-Off direction-selective (DS) ganglion cells in sarcosine-incubated rabbit retina was combined with glycine immunocytochemistry to examine the dendritic relationships between the DS ganglion cells and the cholinergic amacrine cells. These double-labeled preparations showed that the dendrites of the DS ganglion cells closely follow the fasciculated dendrites of the cholinergic amacrine cells. Each ganglion cell dendrite located within the cholinergic strata is associated with a cholinergic fascicle and, conversely, there are few cholinergic fascicles that do not contain at least one dendrite from an On-Off DS cell. It is not known how the dendritic co-fasciculation develops, but the cholinergic dendritic plexus may provide the initial scaffold, because the dendrites of the On-Off DS cells commonly run along the outside of the cholinergic fascicles. J. Comp. Neurol. 421:1-13, 2000. (C) 2000 Wiley-Liss, Inc.

Expression of multilectin receptors and comparative FITC-dextran uptake by human dendritic cells

Dendritic cells (DC) are potent antigen-presenting cells and understanding their mechanisms of antigen uptake is important for loading DC with antigen for immunotherapy. The multilectin receptors, DEC-205 and macrophage mannose receptor (MMR), are potential antigen-uptake receptors; therefore, we examined their expression and FITC-dextran uptake by various human DC preparations. The RT-PCR analysis detected low levels of DEC-205 mRNA in immature blood DC, Langerhans cells (LC) and immature monocyte-derived DC (Mo-DC), Its mRNA expression increased markedly upon activation, indicating that DEC-205 is an activation-associated molecule. In Mo-DC, the expression of cell-surface DEC-205 increased markedly during maturation. In blood DC, however, the cell-surface expression of DEC-205 did not change during activation, suggesting the presence of a large intracellular pool of DEC-205 or post-transcriptional regulation. Immature Mo-DC expressed abundant MMR, but its expression diminished upon maturation. Blood DC and LC did not express detectable levels of the MMR, FITC-dextran uptake by both immature and activated blood DC was 30- to 70-fold less than that of LC, immature Mo-DC and macrophages. In contrast to immature Mo-DC, the FITC-dextran uptake by LC was not inhibited effectively by mannose, an inhibitor for MMR-mediated FITC-dextran uptake. Thus, unlike Mo-DC, blood DC and LC do not use the MMR for carbohydrate-conjugated antigen uptake and alternative receptors may yet be defined on these DC. Therefore, DEC-205 may have a different specificity as an antigen uptake receptor or contribute to an alternative DC function.