Project description:To understand the mechanisms by which mast cells affect the features of breast cancer cells, we collected spontaneous mammary tumors from MMTV-PyMT mice, C57BL/6 wild type or back-crossed with Wsh mice which lack mast cells. Gene expression profiling was performed to select the genes which are differentially expressed in the presence or absence of mast cells.
Project description:Mast cells, activated by antigen via the high affinity receptor for IgE (FcεRI), release an array of pro-inflammatory mediators that contribute to allergic disorders such as asthma and anaphylaxis. The KIT ligand, stem cell factor (SCF), is critical for mast cell expansion, differentiation and survival, and, under acute conditions, enhances mast cell activation. However, extended SCF exposure in vivo conversely protects against fatal antigen-mediated anaphylaxis. In investigating this dichotomy, we identified a novel mode of regulation of the mast cell activation phenotype through SCF-mediated programming. We found that mouse bone marrow-derived mast cells chronically exposed to SCF displayed a marked attenuation of FcεRI-mediated degranulation and cytokine production. The hypo-responsive phenotype was not a consequence of altered signals regulating calcium flux or protein kinase C, but of ineffective cytoskeletal reorganization, with evidence implicating a down-regulation of expression of the Src kinase Hck. Collectively, these findings demonstrate a major role for SCF in the homeostatic control of mast cell activation with potential relevance to mast cell-driven disease and the development of novel approaches for the treatment of allergic disorders. Mouse bone marrow-derived mast cells were treated with IL3, IL3+IL33, or IL3+SCF. Six replicates each.
Project description:Mast cells, activated by antigen via the high affinity receptor for IgE (FcεRI), release an array of pro-inflammatory mediators that contribute to allergic disorders such as asthma and anaphylaxis. The KIT ligand, stem cell factor (SCF), is critical for mast cell expansion, differentiation and survival, and, under acute conditions, enhances mast cell activation. However, extended SCF exposure in vivo conversely protects against fatal antigen-mediated anaphylaxis. In investigating this dichotomy, we identified a novel mode of regulation of the mast cell activation phenotype through SCF-mediated programming. We found that mouse bone marrow-derived mast cells chronically exposed to SCF displayed a marked attenuation of FcεRI-mediated degranulation and cytokine production. The hypo-responsive phenotype was not a consequence of altered signals regulating calcium flux or protein kinase C, but of ineffective cytoskeletal reorganization, with evidence implicating a down-regulation of expression of the Src kinase Hck. Collectively, these findings demonstrate a major role for SCF in the homeostatic control of mast cell activation with potential relevance to mast cell-driven disease and the development of novel approaches for the treatment of allergic disorders.
Project description:Interleukin-33 (IL-33) is elevated in afflicted tissues of patients with mast cell-dependent chronic allergic diseases. Based on its acute effects on mouse mast cells (MCs), IL-33 is thought to play a role in the pathogenesis of allergic disease through MC activation. However, the manifestations of chronic IL-33 exposure on human MC function, which best reflect the conditions associated with chronic allergic disease, are unknown. We now find that long-term exposure of human and mouse MCs to IL-33 results in a substantial reduction of MC activation in response to antigen. This reduction required >72 h exposure to IL-33 for onset and 1-2 wk for reversion following IL-33 removal. This hypo-responsive phenotype was determined to be a consequence of MyD88-dependent attenuation of signaling processes necessary for MC activation including antigen-mediated calcium mobilization and cytoskeletal reorganization; potentially as a consequence of down-regulation of the expression of PLCg1 and Hck. These findings suggest that IL-33 may play a protective, rather than a causative role in MC activation under chronic conditions and, furthermore, reveal regulated plasticity in the MC activation phenotype. The ability to down-regulate MC activation in this manner may provide alternative approaches for treatment of MC-driven disease. Mouse bone marrow-derived mast cells treated with IL3 or IL3+IL33. 6 replicates each.
Project description:Microenvironment-based alterations in mast cell phenotypes influence the susceptibility to anaphylaxis, yet the mechanisms underlying proper maturation of mast cells toward an anaphylaxis-sensitive phenotype are incompletely understood. Here we report that PLA2G3, a mammalian homolog of anaphylactic bee venom phospholipase A2, regulates this process. PLA2G3 secreted from mast cells is coupled with fibroblastic lipocalin-type PGD2 synthase (L-PGDS) to provide PGD2, which facilitates mast cell maturation via PGD2 receptor (DP1). Mice lacking PLA2G3, L-PGDS or DP1, mast cell-deficient mice reconstituted with PLA2G3- or DP1-null mast cells, or mast cells cocultured with L-PGDS-ablated fibroblasts exhibited impaired mast cell maturation and anaphylaxis. Thus, we describe a lipid-driven PLA2G3-L-PGDS-DP1 loop that drives mast cell maturation.
Project description:Mast cells produce a large amount of several chemokines after cross-linking of FceRI and participate in the pathogenesis of allergic diseases. The objective of this study was to comprehensively investigate FceRI-mediated chemokine induction in human mast cells and the effect of a corticosteroid (dexamethasone) and a calcineurin inhibitor (FK506). Human peripheral blood-derived mast cells were stimulated with anti-IgE antibody in the presence of dexamethasone or FK506. Expression of eight chemokines was significantly induced in mast cells by anti-IgE stimulation. Induction of CCL2, CCL7, CXCL3 and CXCL8 by anti-IgE was significantly inhibited by dexamethasone. In contrast, induction of CCL1, CCL3, CCL4 and CCL18 was significantly inhibited by FK506. Combination of dexamethasone and FK506 suppressed production of all chemokines by anti-IgE stimulation. These results suggest that corticosteroids and calcineurin inhibitors inhibit expression of distinct subsets of chemokines and a combination of these drugs almost completely suppresses the induction of all chemokine genes in human mast cells in response to FceRI-dependent stimulation. Human peripheral blood-derived mast cells were stimulated with anti-IgE antibody in the presence of dexamethasone or FK506. Gene expression profiles were evaluated using GeneChip Human Genome U133 plus 2.0 probe arrays (Affymetrix).
Project description:Type 2 immune responses are crucial for protection against helminth infections and for the maintenance of tissue homeostasis, yet the underlying mechanisms of immune activation remain incompletely understood. Here, we study the role of mast cells in type 2 immunity. While the number of lamina propria residing mast cells (termed LPMCs hereinafter) remained stable, intraepithelial mast cells (termed IEMCs hereinafter) markedly expanded during the course of type 2 responses. We uncovered a new type 2 response mechanism depending on the crosstalk between mast cells and epithelial cells, and defined the function of intraepithelial mast cells.