Distinct antigen uptake receptors route to the same storage compartments for cross‐presentation in dendritic cells

Macrophages (MΦ) and dendritic cells (DC), major players of the mononuclear phagocyte system (MoPh), are potent antigen presenting cells that steadily sense and respond to signals from the surrounding microenvironment, leading to either immunogenic or tolerogenic outcomes. Next to classical MHC-I/MHC-II antigen-presentation pathways described in the vast majority of cell types, a subset of MoPh (CD8+, XCR1+, CLEC9A+, BDCA3+ conventional DCs in human) is endowed with a high competence to cross-present external (engulfed) antigens on MHC-I molecules to CD8+ T-cells. This exceptional DC function is thought to be a crucial crossroad in cytotoxic antitumor immunity and has been extensively studied in the past decades. Biophysical and biochemical fingerprints of tumor micromilieus show significant spatiotemporal differences in comparison to non-neoplastic tissue. In tumors, low pH (mainly due to extracellular lactate accumulation via the Warburg effect and via glutaminolysis) and high oncotic and osmotic pressure (resulting from tumor debris, increased extracellular matrix components but in part also triggered by nutritive aspects) are—despite fluctuations and difficulties in measurement—likely the most constant general hallmarks of tumor microenvironment. Here, we focus on the influence of acidic and hypertonic micromilieu on the capacity of DCs to cross-present tumor-specific antigens. We discuss complex and in part controversial scientific data on the interference of these factors with to date reported mechanisms of antigen uptake, processing and cross-presentation, and we highlight their potential role in cancer immune escape and poor clinical response to DC vaccines.

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Histamine Improves Antigen Uptake and Cross-Presentation by Dendritic Cells

The Journal of Immunology ◽

10.4049/jimmunol.179.6.3425 ◽

2007 ◽

Vol 179 (6) ◽

pp. 3425-3433 ◽

Cited By ~ 45

Author(s):

Maria Marta Amaral ◽

Carlos Davio ◽

Ana Ceballos ◽

Gabriela Salamone ◽

Cristian Cañones ◽

...

Keyword(s):

Dendritic Cells ◽

Antigen Uptake ◽

Cross Presentation

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The C-type lectin receptor CLEC9A mediates antigen uptake and (cross-)presentation by human blood BDCA3+ myeloid dendritic cells

Blood ◽

10.1182/blood-2011-08-373944 ◽

2012 ◽

Vol 119 (10) ◽

pp. 2284-2292 ◽

Cited By ~ 145

Author(s):

Gerty Schreibelt ◽

Lieke J. J. Klinkenberg ◽

Luis J. Cruz ◽

Paul J. Tacken ◽

Jurjen Tel ◽

...

Keyword(s):

T Cells ◽

Dendritic Cells ◽

Mhc Class Ii ◽

Receptor Internalization ◽

Cell Surface Expression ◽

Antigen Delivery ◽

Myeloid Dendritic Cells ◽

Antigen Uptake ◽

Cross Presentation ◽

Lectin Receptor

Abstract CLEC9A is a recently discovered C-type lectin receptor involved in sensing necrotic cells. In humans, this receptor is selectively expressed by BDCA3+ myeloid dendritic cells (mDCs), which have been proposed to be the main human cross-presenting mDCs and may represent the human homologue of murine CD8+ DCs. In mice, it was demonstrated that antigens delivered with antibodies to CLEC9A are presented by CD8+ DCs to both CD4+ and CD8+ T cells and induce antitumor immunity in a melanoma model. Here we assessed the ability of CLEC9A to mediate antigen presentation by human BDCA3+ mDCs, which represent < 0.05% of peripheral blood leukocytes. We demonstrate that CLEC9A is only expressed on immature BDCA3+ mDCs and that cell surface expression is lost after TLR-mediated maturation. CLEC9A triggering via antibody binding rapidly induces receptor internalization but does not affect TLR-induced cytokine production or expression of costimulatory molecules. More importantly, antigens delivered via CLEC9A antibodies to BDCA3+ mDCs are presented by both MHC class I (cross-presentation) and MHC class II to antigen-specific T cells. We conclude that CLEC9A is a promising target for in vivo antigen delivery in humans to increase the efficiency of vaccines against infectious or malignant diseases.

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An ITAM-signaling pathway controls cross-presentation of particulate but not soluble antigens in dendritic cells

Journal of Experimental Medicine ◽

10.1084/jem.20071283 ◽

2007 ◽

Vol 204 (12) ◽

pp. 2889-2897 ◽

Cited By ~ 45

Author(s):

Daniel B. Graham ◽

Linda M. Stephenson ◽

Siu Kit Lam ◽

Karry Brim ◽

Hyang Mi Lee ◽

...

Keyword(s):

Dendritic Cells ◽

Signaling Pathway ◽

Critical Role ◽

Nucleotide Exchange ◽

Independent Manner ◽

Antigen Uptake ◽

Cross Presentation ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factors ◽

Activation Motif

Dendritic cells (DC) possess a unique capacity for presenting exogenous antigen on major histocompatibility class I, a process that is referred to as cross-presentation, which serves a critical role in microbial and tumor immunity. During cross-presentation, antigens derived from pathogen-infected or tumor cells are internalized and processed by DCs for presentation to cytotoxic T lymphocytes (CTLs). We demonstrate that a signaling pathway initiated by the immunoreceptor tyrosine–based activation motif (ITAM)–containing adaptors DAP12 and FcRγ utilizes the Vav family of Rho guanine nucleotide exchange factors (GEFs) for processing and cross-presentation of particulate, but not soluble, antigens by DCs. Notably, this novel pathway is crucial for processing and presentation of particulate antigens, such as those associated with Listeria monocytogenes bacteria, yet it is not required for antigen uptake. Mechanistically, we provide evidence that in DCs, Vav GEFs are essential to link ITAM-dependent receptors with the activation of the NOX2 complex and production of reactive oxygen species (ROS), which regulate phagosomal pH and processing of particulate antigens for cross-presentation. Importantly, we show that genetic disruption of the DAP12/FcRγ–Vav pathway leads to antigen presentation defects that are more profound than in DCs lacking NOX2, suggesting that ITAM signaling also controls cross-presentation in a ROS-independent manner.

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Scavenger Receptor Class B Is Required for Hepatitis C Virus Uptake and Cross-Presentation by Human Dendritic Cells

Journal of Virology ◽

10.1128/jvi.02478-07 ◽

2008 ◽

Vol 82 (7) ◽

pp. 3466-3479 ◽

Cited By ~ 65

Author(s):

Heidi Barth ◽

Eva K. Schnober ◽

Christoph Neumann-Haefelin ◽

Christine Thumann ◽

Mirjam B. Zeisel ◽

...

Keyword(s):

Dendritic Cells ◽

Hepatitis C Virus ◽

Hepatitis C ◽

Bacterial Invasion ◽

Type I ◽

Antigen Uptake ◽

Cross Presentation ◽

Class B ◽

Particle Binding ◽

Human Dendritic Cells

ABSTRACT Class B scavenger receptors (SR-Bs) bind lipoproteins and play an important role in lipid metabolism. Most recently, SR-B type I (SR-BI) and its splicing variant SR-BII have been found to mediate bacterial adhesion and cytosolic bacterial invasion in mammalian cells. In this study, we demonstrate that SR-BI is a key host factor required for hepatitis C virus (HCV) uptake and cross-presentation by human dendritic cells (DCs). Whereas monocytes and T and B cells were characterized by very low or undetectable SR-BI expression levels, human DCs demonstrated a high level of cell surface expression of SR-BI similar to that of primary human hepatocytes. Antibodies targeting the extracellular loop of SR-BI efficiently inhibited HCV-like particle binding, uptake, and cross-presentation by human DCs. Moreover, human high-density lipoprotein specifically modulated HCV-like particle binding to DCs, indicating an interplay of HCV with the lipid transfer function of SR-BI in DCs. Finally, we demonstrate that anti-SR-BI antibodies inhibit the uptake of cell culture-derived HCV (HCVcc) in DCs. In conclusion, these findings identify a novel function of SR-BI for viral antigen uptake and recognition and may have an important impact on the design of HCV vaccines and immunotherapeutic approaches aiming at the induction of efficient antiviral immune responses.

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Glycan modification of antigen alters its intracellular routing in dendritic cells, promoting priming of T cells

eLife ◽

10.7554/elife.11765 ◽

2016 ◽

Vol 5 ◽

Cited By ~ 13

Author(s):

Ingeborg Streng-Ouwehand ◽

Nataschja I Ho ◽

Manja Litjens ◽

Hakan Kalay ◽

Martine Annemarie Boks ◽

...

Keyword(s):

T Cells ◽

Dendritic Cells ◽

T Cell ◽

Glycan Structure ◽

Antigen Uptake ◽

Lectin Receptors ◽

Cross Presentation ◽

Lectin Receptor ◽

Intracellular Storage ◽

Glycan Modification

Antigen uptake by dendritic cells and intracellular routing of antigens to specific compartments is regulated by C-type lectin receptors that recognize glycan structures. We show that the modification of Ovalbumin (OVA) with the glycan-structure LewisX (LeX) re-directs OVA to the C-type lectin receptor MGL1. LeX-modification of OVA favored Th1 skewing of CD4+ T cells and enhanced cross-priming of CD8+ T cells. While cross-presentation of native OVA requires high antigen dose and TLR stimuli, LeX modification reduces the required amount 100-fold and obviates its dependence on TLR signaling. The OVA-LeX-induced enhancement of T cell cross-priming is MGL1-dependent as shown by reduced CD8+ effector T cell frequencies in MGL1-deficient mice. Moreover, MGL1-mediated cross-presentation of OVA-LeX neither required TAP-transporters nor Cathepsin-S and was still observed after prolonged intracellular storage of antigen in Rab11+LAMP1+ compartments. We conclude that controlled neo-glycosylation of antigens can crucially influence intracellular routing of antigens, the nature and strength of immune responses and should be considered for optimizing current vaccination strategies.

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