Project description:Although mast cells elicit proinflammatory and type I IFN responses upon VSV infection, in response to L.monocytogenes (L.m) or S. Typhimurium (S.t), such cells elicit a transcriptional program devoid of type I IFN response. Balanced induction of proinflamatory and type I interferon (IFN) responses upon activation of Toll like receptors (TLRs) determines the outcome of microbial infections and the pathogenesis of autoimmune and other inflammatory diseases. Mast cells, key components of the innate immune system, are known for their debilitating role in allergy and autoimmune syndromes. However, their potential role in anti-microbial host defenses is increasingly being acknowledged. How mast cells interact with microbes and the nature of responses triggered thereof is not well characterized. Here we show that in response to TLR activation by Gram-positive and negative bacteria or their components like LPS, unlike macrophages, mast cells elicit pro-inflammatory but not type I IFN responses. We demonstrate that in mast cells, the bound bacteria and TLR ligands remain trapped at the cell surface and do not undergo internalization - a prerequisite for type I IFN induction. Such cells could, however, elicit type I IFNs in response to vesicular stomatitis virus (VSV), which accesses the cytosolic RIG-I receptor. Although important for anti-viral immunity, a strong type I IFN response is known to contribute to pathogenesis during bacterial infection. Thus, while endowed with the capacity to elicit type I IFNs in response to viral infection, the fact that mast cells only elicit pro-inflammatory responses upon bacterial infection illustrates that mast cells, key effector cells of the innate immune system, are well adjusted for optimal anti-bacterial and anti-viral responses.
Project description:Although mast cells elicit proinflammatory and type I IFN responses upon VSV infection, in response to L.monocytogenes (L.m) or S. Typhimurium (S.t), such cells elicit a transcriptional program devoid of type I IFN response. Balanced induction of proinflamatory and type I interferon (IFN) responses upon activation of Toll like receptors (TLRs) determines the outcome of microbial infections and the pathogenesis of autoimmune and other inflammatory diseases. Mast cells, key components of the innate immune system, are known for their debilitating role in allergy and autoimmune syndromes. However, their potential role in anti-microbial host defenses is increasingly being acknowledged. How mast cells interact with microbes and the nature of responses triggered thereof is not well characterized. Here we show that in response to TLR activation by Gram-positive and negative bacteria or their components like LPS, unlike macrophages, mast cells elicit pro-inflammatory but not type I IFN responses. We demonstrate that in mast cells, the bound bacteria and TLR ligands remain trapped at the cell surface and do not undergo internalization - a prerequisite for type I IFN induction. Such cells could, however, elicit type I IFNs in response to vesicular stomatitis virus (VSV), which accesses the cytosolic RIG-I receptor. Although important for anti-viral immunity, a strong type I IFN response is known to contribute to pathogenesis during bacterial infection. Thus, while endowed with the capacity to elicit type I IFNs in response to viral infection, the fact that mast cells only elicit pro-inflammatory responses upon bacterial infection illustrates that mast cells, key effector cells of the innate immune system, are well adjusted for optimal anti-bacterial and anti-viral responses. Wild type control (cntr) or interferon receptor (IFNAR)-deficient mast cells (MC) or macrophages (MAC) were infected with L.m. and S.t. (MOIs 50 and 5 for MC and MAC, respectively). MC and MAC were exposed to VSV-AV2 (MOI: 2). Samples were analyzed after 6 hours. Uninfected/unstimulated cells were used as reference samples for calculating fold change in gene expression. Gene Expression levels were determined by the Affymetrix MOE 430 2.0 GeneChips. Signal Intensities were calculated using the RMA algorithm and for statistical analysis we applied GeneSpring GX 10 software suite (Agilent Technologies, Waldbronn, Germany). MultiExperiment Viewer (MEV) software version 4.4 of the Institute for Genomic Research was used for clustering algorithm data analysis and visualization.
Project description:The proliferative potential of mast cells after activation for 3-4h was found to be decreased, which suggests that mast cell degranulation and cell proliferation are differentially regulated. ELK4, a member of the ternary complex factor (TCF) subfamily of Ets transcription factors, is one of the downstream effectors of MAPK signaling that is critical for cell proliferation. And Elk4 has been identified to be vital for macrophage activation in response to zymosan and the transcriptional response to 12-O-tetrade canoyl phorbol-13-acetate (TPA) stimulation in fibroblast. However, the effect of ELK4 on the mast cell transcriptional response to FcϵRI and GPCR mediated activation and its potential functional significance in mast cells remain unclear. Here, We characterised the transcriptional program downstream of FcϵRI signalling using IgE-DNP/HSA stimulation by RNA-seq. The investigation of the transcriptional response was performed using murine bone marrow derived mast cells(BMMCs) from different animals: (i) wild type mice, (ii) Elk4 heterozygous mice, (iii) Elk4 knockout mice. Overall, our study identifies a new physiological role of the transcription factor ELK4 in mast cell proliferation and activation.
Project description:Next to their role in IgE-mediated allergic diseases and in promoting inflammation, mast cells also have antiinflammatory functions. They release pro- as well as antiinflammatory mediators, depending on the biological setting. Here we aimed to better understand the role of mast cells during the resolution phase of a local inflammation induced with the Tolllike receptor (TLR)-2 agonist zymosan. Multiple sequential immunohistology combined with a statistical neighborhood analysis showed that mast cells are located in a predominantly antiinflammatory microenvironment during resolution of inflammation and that mast cell-deficiency causes decreased efferocytosis in the resolution phase. Accordingly, FACS analysis showed decreased phagocytosis of zymosan and neutrophils by macrophages in mast cell-deficient mice. mRNA sequencing using zymosan-induced bone marrow-derived mast cells (BMMC) revealed a strong type I interferon (IFN) response, which is known to enhance phagocytosis by macrophages. Both, zymosan and lipopolysaccharides (LPS) induced IFN-b synthesis in BMMCs in similar amounts as in bone marrow derived macrophages. IFN-b was expressed by mast cells in paws from naïve mice and during zymosan-induced inflammation. As described for macrophages the release of type I IFNs from mast cells depended on TLR internalization and endosome acidification. In conclusion, mast cells are able to produce several mediators including IFN-b, which are alone or in combination with each other able to regulate the phagocytotic activity of macrophages during resolution of inflammation.
Project description:Mast cells and basophils are developmentally related cells whose activation is a hallmark of allergy. Functionally, mast cells and basophils overlap in their ability to produce several mediators, including histamine and granule proteases, but studies have increasingly demonstrated non-redundant roles. To characterize the transcriptional heterogeneity of mast cells and basophils upon their activation, we performed large-scale comparative microarrays of murine bone marrow–derived mast cells (BMMCs) and basophils (BMBs) at rest, upon an adaptive-type activation (IgE crosslinking), or upon an innate-type activation (IL-33 stimulation). Hierarchical clustering demonstrated that BMMCs and BMBs shared specific activation-associated transcriptional signatures but differed in others, both between cell type and between activation mode. In BMMCs, IgE crosslinking upregulated 785 genes including Egr2, Ccl1, and Fxyd6, while IL-33 stimulation induced 823 genes including Ccl1, Egr2, and Il1b. Focused bioinformatics pathway analysis demonstrated that IgE activation aligned with processes such as oxidative phosphorylation, angiogenesis, and the p53 pathway. The IL-33–activated transcriptome was enriched in genes commonly altered by NF-B in response to TNF, by IL-6 via STAT3, and in response to IFN. Furthermore, BMBs activated via IgE crosslinking selectively induced immune response genes Ccl1, Il3, and Il2 compared to IL-33–stimulated BMBs. Principal-component analysis revealed key cell- and activation-specific clustering. Overall, our data demonstrate that mast cells and basophils have cell- and activation-specific transcriptional responses and suggest that context-specific gene networks and pathways may shape how the immune system responds to allergens and innate cytokines.
Project description:Interferonopathies drive autoimmunity but can also impair host responses to pathogens including viral infection. To better understand viral susceptibility of patients with STAT1 gain-of-function (GOF) mutations, we generated conditional-knockin mouse models to elucidate disease mechanisms and relevance of different immune subsets. Virally infected Stat1-GOF mice exhibited impaired early IFN-γ production from innate lymphocytes, and lethality due to excess prolonged multi-cytokine production. The presence of the Stat1-GOF allele resulted in premature usage of interferon-stimulated gene factor 3 (ISGF3) over the normal Stat4/AP-1 dependent transcriptomic program in activated innate lymphocytes. Administration of anti-IFN-γantibodies in wild-type (WT) mice after infection phenocopied Stat1-GOF mice presenting exaggerated inflammation despite viral control. Conversely, early administration of exogenous IFN-γ to infected Stat1-GOF mice prevented lethality and exaggerated cytokine response.Although Stat1-GOF mutations facilitate IFN-γ-mediated autoimmunity, early IFN-γ response to viral infection via a normal Stat4 program was impaired, leading to overcompensated inflammatory responses in Stat1-GOF mice.
Project description:Interferonopathies drive autoimmunity but can also impair host responses to pathogens including viral infection. To better understand viral susceptibility of patients with STAT1 gain-of-function (GOF) mutations, we generated conditional-knockin mouse models to elucidate disease mechanisms and relevance of different immune subsets. Virally infected Stat1-GOF mice exhibited impaired early IFN-γ production from innate lymphocytes, and lethality due to excess prolonged multi-cytokine production. The presence of the Stat1-GOF allele resulted in premature usage of interferon-stimulated gene factor 3 (ISGF3) over the normal Stat4/AP-1 dependent transcriptomic program in activated innate lymphocytes. Administration of anti-IFN-γantibodies in wild-type (WT) mice after infection phenocopied Stat1-GOF mice presenting exaggerated inflammation despite viral control. Conversely, early administration of exogenous IFN-γ to infected Stat1-GOF mice prevented lethality and exaggerated cytokine response.Although Stat1-GOF mutations facilitate IFN-γ-mediated autoimmunity, early IFN-γ response to viral infection via a normal Stat4 program was impaired, leading to overcompensated inflammatory responses in Stat1-GOF mice.
Project description:Interferonopathies drive autoimmunity but can also impair host responses to pathogens including viral infection. To better understand viral susceptibility of patients with STAT1 gain-of-function (GOF) mutations, we generated conditional-knockin mouse models to elucidate disease mechanisms and relevance of different immune subsets. Virally infected Stat1-GOF mice exhibited impaired early IFN-γ production from innate lymphocytes, and lethality due to excess prolonged multi-cytokine production. The presence of the Stat1-GOF allele resulted in premature usage of interferon-stimulated gene factor 3 (ISGF3) over the normal Stat4/AP-1 dependent transcriptomic program in activated innate lymphocytes. Administration of anti-IFN-γantibodies in wild-type (WT) mice after infection phenocopied Stat1-GOF mice presenting exaggerated inflammation despite viral control. Conversely, early administration of exogenous IFN-γ to infected Stat1-GOF mice prevented lethality and exaggerated cytokine response.Although Stat1-GOF mutations facilitate IFN-γ-mediated autoimmunity, early IFN-γ response to viral infection via a normal Stat4 program was impaired, leading to overcompensated inflammatory responses in Stat1-GOF mice.
Project description:HIV-1 infection of monocyte-derived macrophages does not elicit a detectable type I IFN response in vitro, however, previously published data has shown that blocking STAT1 and STAT3 inhibits HIV-1 replication. Here we test to see if low levels of IFN inducible genes are detectable in human monocyte-derived macrophages that have been infected with HIV-1 in vitro.