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Korf H.,Catholic University of Leuven | Wenes M.,Catholic University of Leuven | Stijlemans B.,Vrije Universiteit Brussel | Stijlemans B.,Myeloid Cell Immunology Laboratory | And 6 more authors.
Immunobiology | Year: 2012

The vitamin D receptor (VDR) is a hormone nuclear receptor regulating bone and calcium homeostasis. Studies revealing the expression of VDR on immune cells point toward a role for VDR-dependent signaling pathways in immunity. Here we verified the ability of the natural VDR ligand, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) to interfere in inflammatory and T cell stimulatory capacity of macrophages, in particular within a chronic inflammatory disease features of experimental type 1 diabetes (T1D). We demonstrated that VDR is constitutively expressed in macrophages and both the levels of VDR and its downstream targets, are clearly induced by 1,25(OH)2D3. In control mice, macrophage programming with 1,25(OH)2D3 partially abrogated the activation-provoked expression of IL-12p40, TNFα and iNOS as well as the effector T cell-recruiting chemokines, CXCL9, CXCL10 and CXCL11. Targeting VDR signaling in macrophages counteracted their T-cell stimulatory ability despite essentially unaltered expression of antigen-presenting and costimulatory molecules. Furthermore, even in non-obese diabetic (NOD) mice, where macrophages/monocytes featured a heightened responsiveness toward danger signals and a superior T cell stimulatory capacity, 1,25(OH)2D3 successfully curtailed these basic macrophage-mediated functions. Interestingly, the inhibitory action of the active compound was associated with an IL-10-dependent mechanism since 1,25(OH)2D3-treatment of IL-10-deficient macrophages failed to reproduce the characteristic repression on inflammatory mediators or T cell proliferation. Combined, these results highlight the possible therapeutic applicability of this natural immunomodulator, due to its ability to counteract macrophage inflammatory and T cell-activating pathways. © 2012 Elsevier GmbH. Source


de Veirman K.,Vrije Universiteit Brussel | van Ginderachter J.A.,Vrije Universiteit Brussel | van Ginderachter J.A.,Myeloid Cell Immunology Laboratory | Lub S.,Vrije Universiteit Brussel | And 10 more authors.
Oncotarget | Year: 2015

Myeloid-derived suppressor cells (MDSC) are contributing to an immunosuppressive environment by their ability to inhibit T cell activity and thereby promoting cancer progression. An important feature of the incurable plasma cell malignancy Multiple Myeloma (MM) is immune dysfunction. MDSC were previously identified to be present and active in MM patients, however little is known about the MDSC-inducing and-activating capacity of MM cells. In this study we investigated the effects of the tumor microenvironment on MDSC survival. During MM progression in the 5TMM mouse model, accumulation of MDSC in the bone marrow was observed in early stages of disease development, while circulating myeloid cells were increased at later stages of disease. Interestingly, in vivo MDSC targeting by anti-GR1 antibodies and 5-Fluorouracil resulted in a significant reduced tumor load in 5TMM-diseased mice. In vitro generation of MDSC was demonstrated by increased T cell immunosuppressive capacity and MDSC survival was observed in the presence of MM-conditioned medium. Finally, increased Mcl-1 expression was identified as underlying mechanism for MDSC survival. In conclusion, our data demonstrate that soluble factors from MM cells are able to generate MDSC through Mcl-1 upregulation and this cell population can be considered as a possible target in MM disease. Source


van den Bossche J.,Myeloid Cell Immunology Laboratory | Lamers W.H.,Vrije Universiteit Brussel | Koehler E.S.,Vrije Universiteit Brussel | Geuns J.M.C.,Maastricht University | And 10 more authors.
Journal of Leukocyte Biology | Year: 2012

In macrophages, basal polyamine (putrescine, spermidine, and spermine) levels are relatively low but are increased upon IL-4 stimulation. This Th2 cytokine induces Arg1 activity, which converts arginine into ornithine, and ornithine can be decarboxylated by ODC to produce putrescine, which is further converted into spermidine and spermine. Recently, we proposed polyamines as novel agents in IL-4-dependent E-cadherin regulation in AAMs. Here, we demonstrate for the first time that several, but not all, AAM markers depend on polyamines for their IL-4-induced gene and protein expression and that polyamine dependency of genes relies on the macrophage type. Remarkably, Arg1-deficient macrophages display rather enhanced IL-4-induced polyamine production, suggesting that an Arg1-independent polyamine synthesis pathway may operate in macrophages. On the other side of the macrophage activation spectrum, LPS-induced expression of several proinflammatory genes was increased significantly in polyamine-depleted CAMs. Overall, we propose Arg1 independently produced polyamines as novel regulators of the inflammatory status of the macrophage. Indeed, whereas polyamines are needed for IL-4-induced expression of several AAM mediators, they inhibit the LPS-mediated expression of proinflammatory genes in CAMs. © Society for Leukocyte Biology. Source


Beschin A.,Myeloid Cell Immunology Laboratory | Beschin A.,Vrije Universiteit Brussel | Van Den Abbeele J.,Antwerp Institute of Tropical Medicine | Van Den Abbeele J.,Ghent University | And 3 more authors.
Trends in Parasitology | Year: 2014

The life cycle of African trypanosomes involves adaptations to the defense mechanisms of two completely different hosts, the insect vector Glossina and the mammalian host. This interplay ultimately determines host resistance and/or tolerance to parasite infection. In the tsetse fly, the immune deficiency (IMD)-regulated pathway, the scavenger receptor peptidoglycan-recognition protein LB (PGRP-LB), and the reactive oxygen species (ROS)-mediated response modulate the insect's capacity to transmit the parasite. In experimental mice, control of parasite burden and tissue pathogenicity relies on timely regulated interactions between myeloid cells exhibiting distinct activation states (M1 versus M2 type). Tsetse fly saliva and various trypanosome components including adenylate cyclases, DNA, a kinesin heavy chain, and variant surface glycoprotein (VSG) interfere with resistance and tolerance to infection. © 2014 Elsevier Ltd. Source


Daniel B.,Debrecen University | Nagy G.,Debrecen University | Hah N.,Salk Institute for Biological Studies | Horvath A.,Debrecen University | And 13 more authors.
Genes and Development | Year: 2014

RXR signaling is predicted to have a major impact in macrophages, but neither the biological consequence nor the genomic basis of its ligand activation is known. Comprehensive genome-wide studies were carried out to map liganded RXR-mediated transcriptional changes, active binding sites, and cistromic interactions in the context of the macrophage genome architecture. The macrophage RXR cistrome has 5200 genomic binding sites, which are not impacted by ligand. Active enhancers are characterized by PU.1 binding, an increase of enhancer RNA, and P300 recruitment. Using these features, 387 liganded RXR-bound enhancers were linked to 226 genes, which predominantly reside in CTCF/cohesin-limited functional domains. These findings were molecularly validated using chromosome conformation capture (3C) and 3C combined with sequencing (3C-seq), and we show that selected long-range enhancers communicate with promoters via stable or RXR-induced loops and that some of the enhancers interact with each other, forming an interchromosomal network. A set of angiogenic genes, including Vegfa, has liganded RXR-controlled enhancers and provides the macrophage with a novel inducible program. © 2014 Daniel et al. Source

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