RESUMO
BACKGROUND: IgE-mediated degranulation of mast cells (MCs) provides rapid protection against environmental hazards, including animal venoms. A fraction of tissue-resident MCs intimately associates with blood vessels. These perivascular MCs were reported to extend projections into the vessel lumen and to be the first MCs to acquire intravenously injected IgE, suggesting that IgE loading of MCs depends on their vascular association. OBJECTIVE: We sought to elucidate the molecular basis of the MC-blood vessel interaction and to determine its relevance for IgE-mediated immune responses. METHODS: We selectively inactivated the Itgb1 gene, encoding the ß1 chain of integrin adhesion molecules (ITGB1), in MCs by conditional gene targeting in mice. We analyzed skin MCs for blood vessel association, surface IgE density, and capability to bind circulating antibody specific for MC surface molecules, as well as in vivo responses to antigen administered via different routes. RESULTS: Lack of ITGB1 expression severely compromised MC-blood vessel association. ITGB1-deficient MCs showed normal densities of surface IgE but reduced binding of intravenously injected antibodies. While their capacity to degranulate in response to IgE ligation in vivo was unimpaired, anaphylactic responses to antigen circulating in the vasculature were largely abolished. CONCLUSIONS: ITGB1-mediated association of MCs with blood vessels is key for MC immune surveillance of blood vessel content, but is dispensable for slow steady-state loading of endogenous IgE onto tissue-resident MCs.
RESUMO
In addition to being the main cause of mortality worldwide, bacterial and viral infections can be the cause of autoimmune and pregnancy disorders as well. The production of autoantibodies during infection can be explained by various mechanisms, including molecular mimicry, bystander cell activation and epitope spreading. Conversely, bacterial and viral infections during pregnancy are especially dangerous for the fetus. It is documented that infection-induced inflammatory processes mediated by Toll-like receptors (TLR) represent the main cause of preterm labour. We used two crucial bacterial components and TLR ligands, namely peptidoglycan and lipopolysaccharide, to stimulate BALB/c mice before immunisation with tetanus toxoid. Tetanus toxoid is an inactive form of the toxin produced by bacterium Clostridium tetani and shares structural similarity with plasma protein ß2-glycoprotein I. Treatment with peptidoglycan and lipopolysaccharide in combination with tetanus toxoid induced the production of pathological autoantibodies, different fluctuations in natural autoantibodies and different types of reproductive pathology in treated animals, with peptidoglycan treatment being more deleterious. We propose that the production of pathological autoantibodies, TLR activation and changes in natural autoantibodies play crucial roles in infection-induced reproductive pathology in our animal model.
Assuntos
Autoanticorpos/sangue , Complicações Infecciosas na Gravidez/imunologia , beta 2-Glicoproteína I/imunologia , Animais , Animais Recém-Nascidos , Peso ao Nascer , Modelos Animais de Doenças , Feminino , Fertilidade , Lipopolissacarídeos/imunologia , Tamanho da Ninhada de Vivíparos , Camundongos Endogâmicos BALB C , Peptidoglicano/imunologia , Gravidez , Complicações Infecciosas na Gravidez/sangue , Complicações Infecciosas na Gravidez/microbiologia , Complicações Infecciosas na Gravidez/patologia , Complicações Infecciosas na Gravidez/fisiopatologia , Baço/imunologia , Baço/metabolismo , Toxina Tetânica/imunologia , Fatores de Tempo , Receptores Toll-Like/metabolismoRESUMO
Defects in nucleic acid metabolizing enzymes can lead to spontaneous but selective activation of either cGAS/STING or RIG-like receptor (RLR) signaling, causing type I interferon-driven inflammatory diseases. In these pathophysiological conditions, activation of the DNA sensor cGAS and IFN production are linked to spontaneous DNA damage. Physiological, or tonic, IFN signaling on the other hand is essential to functionally prime nucleic acid sensing pathways. Here, we show that low-level chronic DNA damage in mice lacking the Aicardi-Goutières syndrome gene SAMHD1 reduced tumor-free survival when crossed to a p53-deficient, but not to a DNA mismatch repair-deficient background. Increased DNA damage did not result in higher levels of type I interferon. Instead, we found that the chronic interferon response in SAMHD1-deficient mice was driven by the MDA5/MAVS pathway but required functional priming through the cGAS/STING pathway. Our work positions cGAS/STING upstream of tonic IFN signaling in Samhd1-deficient mice and highlights an important role of the pathway in physiological and pathophysiological innate immune priming.
Assuntos
Interferon Tipo I , Ácidos Nucleicos , Camundongos , Animais , Proteína 1 com Domínio SAM e Domínio HD/genética , Imunidade Inata/genética , Proteínas de Membrana/metabolismo , Nucleotidiltransferases/metabolismo , Interferon Tipo I/metabolismoRESUMO
Loss of FLG causes ichthyosis vulgaris. Reduced FLG expression compromises epidermal barrier function and is associated with atopic dermatitis, allergy, and asthma. The flaky tail mouse harbors two mutations that affect the skin barrier, Flgft, resulting in hypomorphic FLG expression, and Tmem79ma, inactivating TMEM79. Mice defective only for TMEM79 featured dermatitis and systemic atopy, but also Flgft/ft BALB/c congenic mice developed eczema, high IgE, and spontaneous asthma, suggesting that FLG protects from atopy. In contrast, a targeted Flg-knockout mutation backcrossed to BALB/c did not result in dermatitis or atopy. To resolve this discrepancy, we generated FLG-deficient mice on pure BALB/c background by inactivating Flg in BALB/c embryos. These mice feature an ichthyosis phenotype, barrier defect, and facilitated percutaneous sensitization. However, they do not develop dermatitis or atopy. Whole-genome sequencing of the atopic Flgft BALB/c congenics revealed that they were homozygous for the atopy-causing Tmem79matted mutation. In summary, we show that FLG deficiency does not cause atopy in mice, in line with lack of atopic disease in a fraction of patients with ichthyosis vulgaris carrying two Flg null alleles. However, the absence of FLG likely promotes and modulates dermatitis caused by other genetic barrier defects.
Assuntos
Alérgenos/imunologia , Dermatite Atópica/etiologia , Proteínas Filagrinas/fisiologia , Hipersensibilidade/etiologia , Ictiose Vulgar/etiologia , Pele/imunologia , Animais , Feminino , Proteínas Filagrinas/deficiência , Proteínas Filagrinas/genética , Ictiose Vulgar/genética , Camundongos , Camundongos Endogâmicos BALB C , Microbiota , Pele/microbiologia , Sequenciamento Completo do GenomaRESUMO
High numbers of mast cells populate the stroma of many types of neoplasms, including human papilloma virus-induced benign and malignant tumors in man and mouse. Equipped with numerous pattern recognition receptors and capable of executing important pro-inflammatory responses, mast cells are considered innate sentinels that significantly impact tumor biology. Mast cells were reported to promote human papilloma virus (HPV)-induced epithelial hyperproliferation and neo-angiogenesis in an HPV-driven mouse model of skin cancer. We analyzed HPV-induced epithelial hyperplasia and squamous cell carcinoma formation, as well as growth of tumors inoculated into the dermis, in mice lacking skin mast cells. Unexpectedly, the absence of mast cells had no effect on HPV-induced epithelial growth or angiogenesis, on growth kinetics of inoculated tumors, or on the immunological tumor micro-milieu. Thus, the conspicuous recruitment of mast cells into tumor tissues cannot necessarily be equated with important mast cell functions in tumor growth.
Assuntos
Proliferação de Células , Transformação Celular Viral/imunologia , Mastócitos , Neoplasias Experimentais , Neovascularização Patológica , Papillomaviridae/imunologia , Animais , Linhagem Celular , Células Epiteliais/imunologia , Células Epiteliais/patologia , Células Epiteliais/virologia , Mastócitos/imunologia , Mastócitos/patologia , Camundongos , Camundongos Transgênicos , Transplante de Neoplasias , Neoplasias Experimentais/irrigação sanguínea , Neoplasias Experimentais/imunologia , Neoplasias Experimentais/patologia , Neoplasias Experimentais/virologia , Neovascularização Patológica/imunologia , Neovascularização Patológica/patologia , Neovascularização Patológica/virologiaRESUMO
Innate inflammatory responses are crucial for induction and regulation of T cell and antibody responses. Mast cell (MC)-deficient Kit mutant mice showed impaired adaptive immunity, suggesting that MCs provide essential adjuvant activities, and pharmacological MC activation was proposed as a new adjuvant principle. However, the Kit mutations result in complex alterations of the immune system in addition to MC deficiency. We revisited the role of MCs in vaccination responses using Mcpt5-Cre R26DTA/DTA and Cpa3Cre/+ mice that lack connective tissue MCs or all MCs, respectively, but feature an otherwise normal immune system. These animals showed no impairment of T and B cell responses to intradermal vaccination with protein antigen plus complete Freund's adjuvant. Moreover, we demonstrate that the adjuvant effects of the MC secretagogue c48/80 in intradermal or mucosal immunization are independent of the presence of MCs. We hence find no evidence for a regulation by MCs of adaptive immune responses to protein antigens. The finding that immunological MC functions differ from those suggested by experiments in Kit mutants, emphasizes the importance of rigorous tests in Kit-independent MC-deficiency models.
Assuntos
Adjuvantes Imunológicos , Antígenos/imunologia , Imunidade , Mastócitos/imunologia , Mastócitos/metabolismo , Proteínas Proto-Oncogênicas c-kit/metabolismo , Imunidade Adaptativa , Animais , Modelos Animais de Doenças , Escherichia coli/imunologia , Imunidade nas Mucosas/imunologia , Imunização , Linfonodos/imunologia , Linfonodos/metabolismo , Camundongos , Camundongos Knockout , Peptídeos/imunologia , Proteínas Proto-Oncogênicas c-kit/genética , Linfócitos T/imunologia , Linfócitos T/metabolismoRESUMO
Recent data concerning antiphospholipid syndrome (APS) induction have shown that ß2-glycoprotein I (ß2GPI) binds lipopolysaccharide (LPS), which results in conformational changes, exposition of a cryptic epitope and possible pathological anti-ß2GPI antibody production. In order to investigate the effects of LPS on the induction of APS-related pathology, we performed hyperimmunization of BALB/c and C57BL/6 mice with LPS, alone or in combination with tetanus toxoid (TTd), a protein structurally similar to ß2GPI. We report that, although high affinity pathological anti-ß2GPI antibodies were produced in all groups of animals, the reproductive pathology was recorded only in mice that received both LPS and TTd, implying on the important roles of both infections and molecular mimicry in APS pathogenesis. Moreover, APS-related reproductive pathology was more pronounced in BALB/c (lowered fertility and fecundity) than C57BL/6 mice (lowered fecundity), which correlated well with the disruption in natural antibody network observed in BALB/c mouse strain.