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  • 1
    Keywords: RECEPTOR ; EXPRESSION ; IN-VIVO ; MODELS ; DISEASE ; MICE ; C-KIT ; DEFICIENCY ; MURINE MODEL ; CARBOXYPEPTIDASE-A ; W-SH
    Abstract: Immunological functions of mast cells remain poorly understood. Studies in Kit mutant mice suggest key roles for mast cells in certain antibody- and T cell-mediated autoimmune diseases. However, Kit mutations affect multiple cell types of both immune and nonimmune origin. Here, we show that targeted insertion of Cre-recombinase into the mast cell carboxypeptidase A3 locus deleted mast cells in connective and mucosal tissues by a genotoxic Trp53-dependent mechanism. Cre-mediated mast cell eradication (Cre-Master) mice had, with the exception of a lack of mast cells and reduced basophils, a normal immune system. Cre-Master mice were refractory to IgE-mediated anaphylaxis, and this defect was rescued by mast cell reconstitution. This mast cell-deficient strain was fully susceptible to antibody-induced autoimmune arthritis and to experimental autoimmune encephalomyelitis. Differences comparing Kit mutant mast cell deficiency models to selectively mast cell-deficient mice call for a systematic re-evaluation of immunological functions of mast cells beyond allergy.
    Type of Publication: Journal article published
    PubMed ID: 22101159
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  • 2
    Keywords: GENE-EXPRESSION ; DENDRITIC CELLS ; PROGENITOR CELLS ; COLONY-STIMULATING FACTOR ; HEMATOPOIETIC STEM ; LINEAGE COMMITMENT ; C/EBP-ALPHA BINDS ; MYELOID LINEAGES ; PU.1 GENE ; BTK
    Abstract: Bruton tyrosine kinase (Btk) is essential for B cell development and function and also appears to be important for myeloid cells. The bone marrow of Btk-deficient mice shows enhanced granulopoiesis compared with that of wild-type mice. In purified granulocyte-monocyte-progenitors (GMP) from Btk-deficient mice, the development of granulocytes is favored at the expense of monocytes. However, Btk-deficient neutrophils are impaired in maturation and function. Using bone marrow chimeras, we show that this defect is cell-intrinsic to neutrophils. In GMP and neutrophils, Btk plays a role in GM-CSF- and Toll-like receptor-induced differentiation. Molecular analyses revealed that expression of the lineage-determining transcription factors C/EBPalpha, C/EBPbeta, and PU.1, depends on Btk. In addition, expression of several granule proteins, including myeloperoxidase, neutrophilic granule protein, gelatinase and neutrophil elastase, is Btk-dependent. In the Arthus reaction, an acute inflammatory response, neutrophil migration into tissues, edema formation, and hemorrhage are significantly reduced in Btk-deficient animals. Together, our findings implicate Btk as an important regulator of neutrophilic granulocyte maturation and function in vivo.
    Type of Publication: Journal article published
    PubMed ID: 21063022
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  • 3
    Keywords: APOPTOSIS ; protease ; CYSTEINE PROTEASE ; chymase ; proteolytic enzymes ; Mast cell ; Tryptase ; Proteoglycan Structure ; Secretory Granule ; Serglycin
    Abstract: Mast cell secretory granules (secretory lysosomes) contain large amounts of fully active proteases bound to serglycin proteoglycan. Damage to the granule membrane will thus lead to the release of serglycin and serglycin-bound proteases into the cytosol, which potentially could lead to proteolytic activation of cytosolic pro-apoptotic compounds. We therefore hypothesized that mast cells are susceptible to apoptosis induced by permeabilization of the granule membrane and that this process is serglycin-dependent. Indeed, we show that wild-type mast cells are highly sensitive to apoptosis induced by granule permeabilization, whereas serglycin-deficient cells are largely resistant. The reduced sensitivity of serglycin-/- cells to apoptosis was accompanied by reduced granule damage, reduced release of proteases into the cytosol, and defective caspase-3 activation. Mechanistically, the apoptosis-promoting effect of serglycin involved serglycin-dependent proteases, as indicated by reduced sensitivity to apoptosis and reduced caspase-3 activation in cells lacking individual mast cell-specific proteases. Together, these findings implicate serglycin proteoglycan as a novel player in mast cell apoptosis.
    Type of Publication: Journal article published
    PubMed ID: 21123167
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  • 4
    Keywords: GROWTH-FACTOR ; IN-VIVO ; C-KIT ; DEFICIENT MICE ; EXPERIMENTAL AUTOIMMUNE ENCEPHALOMYELITIS ; TRICHINELLA-SPIRALIS ; HYPERSENSITIVITY REACTIONS ; W-SH ; W/W-V MICE ; BACTERIAL-INFECTIONS
    Abstract: Immunological functions of mast cells are currently considered to be much broader than the original role of mast cells in IgE-driven allergic disease. The spectrum of proposed mast cell functions includes areas as diverse as the regulation of innate and adaptive immune responses, protective immunity against viral, microbial, and parasitic pathogens, autoimmunity, tolerance to graft rejection, promotion of or protection from cancer, wound healing, angiogenesis, cardiovascular diseases, diabetes, obesity, and others. The vast majority of in vivo mast cell data have been based on mast cell-deficient Kit mutant mice. However, work in new mouse mutants with unperturbed Kit function, which have a surprisingly normal immune system, has failed to corroborate some key immunological aspects, formerly attributed to mast cells. Here, we consider the implications of these recent developments for the state of the field as well as for future work, aiming at deciphering the physiological functions of mast cells.
    Type of Publication: Journal article published
    PubMed ID: 22840840
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  • 5
    Keywords: ACCUMULATION ; STORAGE ; DEGRADATION ; asthma ; CYTOKINE PRODUCTION ; chymase ; Secretory Granule ; CARBOXYPEPTIDASE-A ; EXTENDED SUBSTRATE-SPECIFICITY ; MICE LACKING HEPARIN
    Abstract: Abstract Mast cell (MC) granules contain large amounts of proteases of chymase, tryptase and carboxypeptidase A (MC-CPA) type, stored in complex with serglycin, a proteoglycan with heparin side chains. Hence, serglycin-protease complexes are released upon MC degranulation and may influence local inflammation. Here we explored the possibility that a serglycin-protease axis may regulate levels of IL-13, a cytokine involved in allergic asthma. Indeed, we found that WT MCs efficiently degraded exogenous or endogenously produced IL-13 upon degranulation, whereas serglycin-/- MCs totally lacked this ability. Moreover, MCmediated IL-13 degradation was blocked both by a serine protease inhibitor and by a heparin antagonist, suggesting that IL-13 degradation was catalyzed by serglycin-dependent serine proteases and that optimal IL-13 degradation was dependent on both the serglycin- and the protease component of the serglycin-protease complex. Moreover, IL-13 degradation was abrogated in MC-CPA-/- MC cultures, but was normal in cultures of MCs with an inactivating mutation of MC-CPA, suggesting that the IL-13-degrading serine proteases rely on MC-CPA protein. Together, our data implicate a serglycin-serine protease axis in the regulation of extracellular levels of IL-13. Possibly, reduction of IL-13 levels through this mechanism can provide a protective function in the context of allergic inflammation.
    Type of Publication: Journal article published
    PubMed ID: 23096569
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  • 6
    Keywords: GENE-EXPRESSION ; MOUSE ; MUTATIONS ; C-KIT ; ROLES ; proto-oncogene ; TUMOR-BEARING MICE ; HEMATOPOIETIC STEM ; TYROSINE KINASE RECEPTOR ; W-LOCUS
    Abstract: Mast cell-deficient Kit(W-sh) "sash" mice are widely used to investigate mast cell functions. However, mutations of c-Kit also affect additional cells of hematopoietic and nonimmune origin. In this study, we demonstrate that Kit(W-sh) causes aberrant extramedullary myelopoiesis characterized by the expansion of immature lineage-negative cells, common myeloid progenitors, and granulocyte/macrophage progenitors in the spleen. A consistent feature shared by these cell types is the reduced expression of c-Kit. Populations expressing intermediate and high levels of Ly6G, a component of the myeloid differentiation Ag Gr-1, are also highly expanded in the spleen of sash mice. These cells are able to suppress T cell responses in vitro and phenotypically and functionally resemble myeloid-derived suppressor cells (MDSC). MDSC typically accumulate in tumor-bearing hosts and are able to dampen immune responses. Consequently, transfer of MDSC from naive sash mice into line 1 alveolar cell carcinoma tumor-bearing wild-type littermates leads to enhanced tumor progression. However, although it can also be observed in sash mice, accelerated growth of transplanted line 1 alveolar cell carcinoma tumors is a mast cell-independent phenomenon. Thus, the Kit(W-sh) mutation broadly affects key steps in myelopoiesis that may have an impact on mast cell research.
    Type of Publication: Journal article published
    PubMed ID: 23636054
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  • 7
    Keywords: DENDRITIC CELLS ; LYMPH-NODES ; T-CELL ; MOUSE ; IMMUNE-RESPONSE ; EFFECTOR ; C-KIT ; AUTOIMMUNITY ; W-SH ; BIOBREEDING RAT
    Abstract: Mast cells have been invoked as important players in immune responses associated with autoimmune diseases. Based on in vitro studies, or in vivo through the use of Kit mutant mice, mast cells have been suggested to play immunological roles in direct antigen presentation to both CD4(+) and CD8(+) T cells, in the regulation of T-cell and dendritic cell migration to lymph nodes, and in Th1 versus Th2 polarization, all of which could significantly impact the immune response against self-antigens in autoimmune disease, including type 1 diabetes (T1D). Until now, the role of mast cells in the onset and incidence of T1D has only been indirectly tested through the use of low-specificity mast cell inhibitors and activators, and published studies reported contrasting results. Our three laboratories have generated independently two strains of mast cell-deficient nonobese diabetic (NOD) mice, NOD.Cpa3(Cre/+) (Heidelberg) and NOD.Kit(W-sh/W-sh) (Leuven and Boston), to address the effects of mast cell deficiency on the development of T1D in the NOD strain. Our collective data demonstrate that both incidence and progression of T1D in NOD mice are independent of mast cells. Moreover, analysis of pancreatic lymph node cells indicated that lack of mast cells has no discernible effect on the autoimmune response, which involves both innate and adaptive immune components. Our results demonstrate that mast cells are not involved in T1D in the NOD strain, making their role in this process nonessential and excluding them as potential therapeutic targets.
    Type of Publication: Journal article published
    PubMed ID: 24917576
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  • 8
    Keywords: CANCER ; MICE ; BONE-MARROW ; TUMOR PROGRESSION ; STEM-CELLS ; FACTOR-KAPPA-B ; MOUSE MODEL ; inflammation ; LUNG ADENOCARCINOMA ; C-KIT GENE
    Abstract: Mast cells (MCs) have been identified in various tumors; however, the role of these cells in tumorigenesis remains controversial. Here, we quantified MCs in human and murine malignant pleural effusions (MPEs) and evaluated the fate and function of these cells in MPE development. Evaluation of murine MPE-competent lung and colon adenocarcinomas revealed that these tumors actively attract and subsequently degranulate MCs in the pleural space by elaborating CCL2 and osteopontin. MCs were required for effusion development, as MPEs did not form in mice lacking MCs, and pleural infusion of MCs with MPE-incompetent cells promoted MPE formation. Once homed to the pleural space, MCs released tryptase AB1 and IL-1beta, which in turn induced pleural vasculature leakiness and triggered NF-kappaB activation in pleural tumor cells, thereby fostering pleural fluid accumulation and tumor growth. Evaluation of human effusions revealed that MCs are elevated in MPEs compared with benign effusions. Moreover, MC abundance correlated with MPE formation in a human cancer cell-induced effusion model. Treatment of mice with the c-KIT inhibitor imatinib mesylate limited effusion precipitation by mouse and human adenocarcinoma cells. Together, the results of this study indicate that MCs are required for MPE formation and suggest that MC-dependent effusion formation is therapeutically addressable.
    Type of Publication: Journal article published
    PubMed ID: 25915587
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  • 9
    Abstract: Mast cells and basophils are innate immune cells with overlapping functions that contribute to anti-helminth immunity. Mast cell function during helminth infection was previously studied using mast cell-deficient Kit-mutant mice that display additional mast cell-unrelated immune deficiencies. Here, we use mice that lack basophils or mucosal and connective tissue mast cells in a Kit-independent manner to re-evaluate the impact of each cell type during helminth infection. Neither mast cells nor basophils participated in the immune response to tissue-migrating Strongyloides ratti third-stage larvae, but both cell types contributed to the early expulsion of parasitic adults from the intestine. The termination of S. ratti infection required the presence of mucosal mast cells: Cpa3Cre mice, which lack mucosal and connective tissue mast cells, remained infected for more than 150 days. Mcpt5Cre R-DTA mice, which lack connective tissue mast cells only, and basophil-deficient Mcpt8Cre mice terminated the infection after 1 month with wild-type kinetics despite their initial increase in intestinal parasite burden. Because Cpa3Cre mice showed intact Th2 polarization and efficiently developed protective immunity after vaccination, we hypothesize that mucosal mast cells are non-redundant terminal effector cells in the intestinal epithelium that execute anti-helminth immunity but do not orchestrate it.Mucosal Immunology advance online publication, 6 July 2016; doi:10.1038/mi.2016.56.
    Type of Publication: Journal article published
    PubMed ID: 27381924
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  • 10
    Keywords: CANCER ; EXPRESSION ; GROWTH ; TRANSGENIC MICE ; MORPHOGENESIS ; inflammation ; DEFICIENT MICE ; ROLES ; KIT ; TISSUE-REPAIR
    Abstract: The growth and differentiation factor activin A is a key regulator of tissue repair, inflammation, fibrosis, and tumorigenesis. However, the cellular targets, which mediate the different activin functions, are still largely unknown. In this study, we show that activin increases the number of mature mast cells in mouse skin in vivo. To determine the relevance of this finding for wound healing and skin carcinogenesis, we mated activin transgenic mice with CreMaster mice, which are characterized by Cre recombinase-mediated mast cell eradication. Using single-and double-mutant mice, we show that loss of mast cells neither affected the stimulatory effect of overexpressed activin on granulation tissue formation and reepithelialization of skin wounds nor its protumorigenic activity in a model of chemically induced skin carcinogenesis. Furthermore, mast cell deficiency did not alter wounding-induced inflammation and new tissue formation or chemically induced angiogenesis and tumorigenesis in mice with normal activin levels. These findings reveal that mast cells are not major targets of activin during wound healing and skin cancer development and also argue against nonredundant functions of mast cells in wound healing and skin carcinogenesis in general.
    Type of Publication: Journal article published
    PubMed ID: 24227781
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