Anthracyclin-treated tumor cells are particularly effective in eliciting an anticancer immune response, whereas other DNA-damaging agents such as etoposide and mitomycin C do not induce immunogenic cell death. Here we show that anthracyclins induce the rapid, preapoptotic translocation of calreticulin (CRT) to the cell surface. Blockade or knockdown of CRT suppressed the phagocytosis of anthracyclin-treated tumor cells by dendritic cells and abolished their immunogenicity in mice. The anthracyclin-induced CRT translocation was mimicked by inhibition of the protein...

Natural killer (NK) cells influence innate and adaptive immune host defenses. Existing data indicate that manipulating the balance between inhibitory and activating NK receptor signals, the sensitivity of target cells to NK cell-mediated apoptosis, and NK cell cross-talk with dendritic cells might hold therapeutic promise. Efforts to modulate NK cell trafficking into inflamed tissues and/or lymph nodes, and to counteract NK cell suppressors, might also prove fruitful in the clinic. However, deeper investigation into the benefits of combination therapy, greater und...

The scurfy mutant mouse strain suffers from a fatal lymphoproliferative disease leading to early death within 3-4 wk of age. A frame-shift mutation of the forkhead box transcription factor Foxp3 has been identified as the molecular cause of this multiorgan autoimmune disease. Foxp3 is a central control element in the development and function of regulatory T cells (T reg cells), which are necessary for the maintenance of self-tolerance. However, it is unclear whether dysfunction or a lack of T reg cells is etiologically involved in scurfy pathogenesis and its human...

Compared to "live" vaccines, the immunogenicity of "subunit" vaccines based on recombinant antigen (Ag) is poor, presumably because exogenous Ag fails to effectively access the endosomal Ag-processing pathways of Ag-presenting cells (APC). To overcome this limitation, we exploited biodegradable poly(lactic-co-glycolic) microspheres (MP) co-entrapping Ag and Toll-like receptor (TLR) 9 or 7 ligands as an endosomal delivery device. In vitro, microspheres were rapidly phagocytosed by APC and translocated into phago-endosomal compartments, followed by degradation of th...

Prion diseases are fatal neurodegenerative diseases that are characterized by the conformational conversion of the normal, mainly alpha-helical cellular prion protein (PrP) into the abnormal beta-sheet-rich infectious isoform (PrP(Sc)). The immune system neither shows reaction against cellular PrP nor PrP(Sc), most likely due to profound self-tolerance. In previous studies, we were able to partly overcome self-tolerance using recombinantly expressed dimeric PrP (tandem PrP (tPrP)), in association with different adjuvants. Proof of principle for antiprion efficacy ...

The maturation state of dendritic cells (DCs) is an important determinant for the initiation and regulation of adaptive immune responses. In this study, we wanted to assess whether functional activation of human monocyte-derived DCs can be achieved by electroporation of an activation signal in the form of double-stranded (ds) RNA and whether simultaneous electroporation of the dsRNA with tumor antigen encoding mRNA can lead to the induction of a cytotoxic T-lymphocyte (CTL) response. Electroporation of immature DCs with poly(I:C(12)U), a dsRNA analogue, resulted i...

Over the years, the unique capacity of dendritic cells (DC) for efficient activation of naive T cells has led to their extensive use in cancer immunotherapy protocols. In order to be able to fulfil their role as antigen-presenting cells, the antigen of interest needs to be efficiently introduced and subsequently correctly processed and presented by the DC. For this purpose, a variety of both viral and non-viral antigen-delivery systems have been evaluated. Amongst those, HIV-1-derived lentiviral vectors have been used successfully to transduce DC.This review consi...

Over the past decade, many efforts have been made to identify MHC class II-restricted epitopes from different tumor-associated Ags. Melan-A/MART-1(26-35) parental or Melan-A/MART-1(26-35(A27L)) analog epitopes have been widely used in melanoma immunotherapy to induce and boost CTL responses, but only one Th epitope is currently known (Melan-A51-73, DRB1*0401 restricted). In this study, we describe two novel Melan-A/MART-1-derived sequences recognized by CD4 T cells from melanoma patients. These epitopes can be mimicked by peptides Melan-A27-40 presented by HLA-DRB...

Ex vivo lentivirally transduced dendritic cells (DC) have been described to induce CD8+ and CD4+ T-cell responses against various tumor-associated antigens (TAAs) in vitro and in vivo. We report here that direct administration of ovalbumin (OVA) encoding lentiviral vectors caused in vivo transduction of cells that were found in draining lymph nodes (LNs) and induced potent anti-OVA cytotoxic T cells similar to those elicited by ex vivo transduced DC. The cytotoxic T-lymphocyte (CTL) response following direct injection of lentiviral vectors was highly effective in ...

The critical importance of plasmacytoid dendritic cells (pDCs) in viral infection, autoimmunity, and tolerance has focused major attention on these cells that are rare in blood and immune organs of humans and mice. The recent development of an Flt-3 ligand (FL) culture system of bone marrow cells has led to the simple generation of large numbers of pDCs that resemble their in vivo steady-state counterparts. The FL system has allowed unforeseen insight into the biology of pDCs, and it is assumed that FL is the crucial growth factor for these cells. Surprisingly we ...

We previously described mRNA electroporation as an efficient gene delivery method to introduce tumor-antigens (Ag) into murine immature dendritic cells (DC). Here, we further optimize the protocol and evaluate the capacity of mRNA-electroporated DC as a vaccine for immunotherapy. First, the early DC maturation kinetics and the effect of different lipopolysaccharide incubation periods on the phenotypic maturation profile of DC are determined. Next, we show that either immature or mature DC are equally well electroporated and express and present the transgene at a c...

With the recent advances in human-hemato-lymphoid-system mice, this commentary discusses the utility of these mice and further improvements required to generate an accessible system that allows predictive in vivo human hematology and immunology research.

Flt3-ligand is a nonredundant cytokine in type I interferon-producing cell (IPC) and dendritic cell (DC) development. We demonstrated that IPC and DC differentiation potential is confined to Flt3(+)-hematopoietic progenitor cells, that Flt3-ligand drives development along both lymphoid and myeloid developmental pathways from Flt3(+)-progenitors to Flt3(+)-IPCs and -DCs, and that in vivo pharmacologic inhibition of Flt3-signaling leads to disruption of IPC and DC development in spite of consecutive Flt3-ligand upregulation in treated animals. We here summarize our ...

Inhibition of phagocyte activity depends on the ligation of SIRP- by CD47. New findings show that Sirpa polymorphisms influence the engraftment and tolerance of xenogeneic transplants in NOD-SCID mice.

Lymphoid tissue plasmacytoid and conventional dendritic cells (DCs) are continuously regenerated from hematopoietic stem cells. The cytokine dependence and biology of plasmacytoid and conventional DCs suggest that regeneration might proceed through common DC-restricted developmental intermediates. By selecting for cytokine receptor expression relevant to DC development, we identify here highly cycling Lin(-)c-Kit(int)Flt3(+)M-CSFR(+) cells with a distinct gene-expression profile in mouse bone marrow that, on a clonal level in vitro and as a population both in vitr...

The activation of resting dendritic cells (DCs) is a crucial step in the initiation of adaptive immunity because it links peripheral events initiated by the encounter with pathogens to the activation and expansion of antigen-specific T lymphocytes in secondary lymphoid organs. It is well recognized that a wide variety of microbial products and endogenous signals can trigger DC activation, and that different DC subsets are specialized in inducing different classes of immune responses. In this review, we will focus on how different aspects of DC maturation are regul...

Zymosan is a particulate yeast preparation that elicits high levels of IL-2 and IL-10 from dendritic cells (DC) and engages multiple innate receptors, including the Syk-coupled receptor dectin-1 and the MyD88-coupled receptor TLR2. Here, we show that induction of IL-2 and IL-10 by zymosan requires activation of ERK MAP kinase in murine DC. Surprisingly, ERK activation in response to zymosan is completely blocked in Syk-deficient DC and unaffected by MyD88 deficiency. Conversely, ERK activation in response to the TLR2 agonist Pam3Cys is completely MyD88 dependent a...

Understanding the distribution, function, and lineage relationship of CD8+ T-cell subpopulations is of fundamental value for the monitoring of the immune system in several experimental and clinical situations. However, the available data concerning the description of effector and memory CD8+ subsets in humans remain rather fragmentary because different studies favored the usage of distinct and restricted sets of cell surface markers and functional parameters. We associated multiple markers to subdivide CD8+ T cells into 14 different cell types, several of which we...

The C-type lectin dectin-1 binds to yeast and signals through the kinase Syk and the adaptor CARD9 to induce production of interleukin 10 (IL-10) and IL-2 in dendritic cells (DCs). However, whether this pathway promotes full DC activation remains unclear. Here we show that dectin-1-Syk-CARD9 signaling induced DC maturation and the secretion of proinflammatory cytokines, including IL-6, tumor necrosis factor and IL-23, but little IL-12. Dectin-1-activated DCs 'instructed' the differentiation of CD4+ IL-17-producing effector T cells (T(H)-17 cells) in vitro, and a d...