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1.
Proc Natl Acad Sci U S A ; 121(12): e2312404121, 2024 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-38478694

RESUMO

Plasmacytoid dendritic cells (pDCs) produce type I interferons (IFNs) after sensing viral/bacterial RNA or DNA by toll-like receptor (TLR) 7 or TLR9, respectively. However, aberrant pDCs activation can cause adverse effects on the host and contributes to the pathogenesis of type I IFN-related autoimmune diseases. Here, we show that heparin interacts with the human pDCs-specific blood dendritic cell antigen 2 (BDCA-2) but not with related lectins such as DCIR or dectin-2. Importantly, BDCA-2-heparin interaction depends on heparin sulfation and receptor glycosylation and results in inhibition of TLR9-driven type I IFN production in primary human pDCs and the pDC-like cell line CAL-1. This inhibition is mediated by unfractionated and low-molecular-weight heparin, as well as endogenous heparin from plasma, suggesting that the local blood environment controls the production of IFN-α in pDCs. Additionally, we identified an activation-dependent soluble form of BDCA-2 (solBDCA-2) in human plasma that functions as heparin antagonist and thereby increases TLR9-driven IFN-α production in pDCs. Of importance, solBDCA-2 levels in the serum were increased in patients with scrub typhus (an acute infectious disease caused by Orientia tsutsugamushi) compared to healthy control subjects and correlated with anti-dsDNA antibodies titers. In contrast, solBDCA-2 levels in plasma from patients with bullous pemphigoid or psoriasis were reduced. In summary, this work identifies a regulatory network consisting of heparin, membrane-bound and solBDCA-2 modulating TLR9-driven IFN-α production in pDCs. This insight into pDCs function and regulation may have implications for the treatment of pDCs-related autoimmune diseases.


Assuntos
Doenças Autoimunes , Interferon Tipo I , Humanos , Interferon Tipo I/metabolismo , Heparina/metabolismo , Receptor Toll-Like 9/metabolismo , Células Dendríticas , Doenças Autoimunes/metabolismo
2.
Allergy ; 2024 Jun 23.
Artigo em Inglês | MEDLINE | ID: mdl-38932655

RESUMO

BACKGROUND: The pathological mechanism of the gastrointestinal forms of food allergies is less understood in comparison to other clinical phenotypes, such as asthma and anaphylaxis Importantly, high-IgE levels are a poor prognostic factor in gastrointestinal allergies. METHODS: This study investigated how high-IgE levels influence the development of intestinal inflammation and the metabolome in allergic enteritis (AE), using IgE knock-in (IgEki) mice expressing high levels of IgE. In addition, correlation of the altered metabolome with gut microbiome was analysed. RESULTS: Ovalbumin-sensitized and egg-white diet-fed (OVA/EW) BALB/c WT mice developed moderate AE, whereas OVA/EW IgEki mice induced more aggravated intestinal inflammation with enhanced eosinophil accumulation. Untargeted metabolomics detected the increased levels of N-tau-methylhistamine and 2,3-butanediol, and reduced levels of butyric acid in faeces and/or sera of OVA/EW IgEki mice, which was accompanied with reduced Clostridium and increased Lactobacillus at the genus level. Non-sensitized and egg-white diet-fed (NC/EW) WT mice did not exhibit any signs of AE, whereas NC/EW IgEki mice developed marginal degrees of AE. Compared to NC/EW WT mice, enhanced levels of lysophospholipids, sphinganine and sphingosine were detected in serum and faecal samples of NC/EW IgEki mice. In addition, several associations of altered metabolome with gut microbiome-for example Akkermansia with lysophosphatidylserine-were detected. CONCLUSIONS: Our results suggest that high-IgE levels alter intestinal and systemic levels of endogenous and microbiota-associated metabolites in experimental AE. This study contributes to deepening the knowledge of molecular mechanisms for the development of AE and provides clues to advance diagnostic and therapeutic strategies of allergic diseases.

3.
Immunity ; 37(5): 867-79, 2012 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-23142781

RESUMO

The genome of vertebrates contains endogenous retroviruses (ERVs) that are largely nonfunctional relicts of ancestral germline infection by exogenous retroviruses. However, in some mouse strains ERVs are actively involved in disease. Here we report that nucleic acid-recognizing Toll-like receptors 3, 7, and 9 (TLR 3, TLR7, and TLR9) are essential for the control of ERVs. Loss of TLR7 function caused spontaneous retroviral viremia that coincided with the absence of ERV-specific antibodies. Importantly, additional TLR3 and TLR9 deficiency led to acute T cell lymphoblastic leukemia, underscoring a prominent role for TLR3 and TLR9 in surveillance of ERV-induced tumors. Experimental ERV infection induced a TLR3-, TLR7-, and TLR9-dependent group of "acute-phase" genes previously described in HIV and SIV infections. Our study suggests that in addition to their role in innate immunity against exogenous pathogens, nucleic acid-recognizing TLRs contribute to the immune control of activated ERVs and ERV-induced tumors.


Assuntos
Retrovirus Endógenos/genética , Ácidos Nucleicos/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Receptores Toll-Like/genética , Receptores Toll-Like/metabolismo , Viremia/genética , Animais , Anticorpos Antivirais/genética , Anticorpos Antivirais/imunologia , Linhagem Celular , Retrovirus Endógenos/imunologia , Retrovirus Endógenos/metabolismo , Imunidade Inata/genética , Imunidade Inata/imunologia , Células Matadoras Naturais/imunologia , Células Matadoras Naturais/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Ácidos Nucleicos/imunologia , Ácidos Nucleicos/metabolismo , Oncogenes/genética , Oncogenes/imunologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/imunologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Receptores Toll-Like/imunologia , Viremia/imunologia , Viremia/metabolismo
4.
Immunol Rev ; 269(1): 85-99, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26683147

RESUMO

In the last 20 years research in Immunology underwent fundamental changes. Most importantly, the identification of the key role of innate immune pattern recognition receptors (PRRs) that recognize evolutionarily conserved molecular patterns on infectious pathogens. This results in priming of innate immune cells, which in turn activate and direct the adaptive immune response. Progress in innate immune recognition instigated the current working hypothesis, that recognition of endogenous ligands by PRRs results in innate immune cell activation (autoinflammation) or activation of adaptive cells, with self-reactive antigen receptors (autoimmunity). In particular, nucleic acid-sensing innate immune receptors seem to be prime candidates for a mechanistic understanding of autoreactive activation of the immune system. However, it remains uncertain what the actual source of nucleic acid ligands is and what other signals are needed to drive activation of autoreactive innate immune cells and break self-tolerance of the adaptive immune system. Here, I will review our present understanding about whether the infection with exogenous retroviruses or the reactivation of endogenous retroviruses might play an etiological role in certain autoimmune conditions of humans and murine experimental models.


Assuntos
Doenças Autoimunes/imunologia , Infecções por Retroviridae/imunologia , Retroviridae/imunologia , Animais , Doenças Autoimunes/etiologia , Autoimunidade , Modelos Animais de Doenças , Humanos , Tolerância Imunológica , Camundongos , Ácidos Nucleicos/imunologia , Receptores de Reconhecimento de Padrão/metabolismo , Infecções por Retroviridae/complicações , Ativação Viral
5.
PLoS Biol ; 13(11): e1002290, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26523376

RESUMO

IgE-mediated activation of mast cells and basophils contributes to protective immunity against helminths but also causes allergic responses. The development and persistence of IgE responses are poorly understood, which is in part due to the low number of IgE-producing cells. Here, we used next generation sequencing to uncover a striking overlap between the IgE and IgG1 repertoires in helminth-infected or OVA/alum-immunized wild-type BALB/c mice. The memory IgE response after secondary infection induced a strong increase of IgE+ plasma cells in spleen and lymph nodes. In contrast, germinal center B cells did not increase during secondary infection. Unexpectedly, the memory IgE response was lost in mice where the extracellular part of IgG1 had been replaced with IgE sequences. Adoptive transfer studies revealed that IgG1+ B cells were required and sufficient to constitute the memory IgE response in recipient mice. T cell-derived IL-4/IL-13 was required for the memory IgE response but not for expansion of B cells from memory mice. Together, our results reveal a close relationship between the IgE and IgG1 repertoires in vivo and demonstrate that the memory IgE response is mainly conserved at the level of memory IgG1+ B cells. Therefore, targeting the generation and survival of allergen-specific IgG1+ B cells could lead to development of new therapeutic strategies to treat chronic allergic disorders.


Assuntos
Linfócitos T CD4-Positivos/metabolismo , Imunoglobulina E/metabolismo , Imunoglobulina G/metabolismo , Memória Imunológica , Interleucina-13/metabolismo , Interleucina-4/metabolismo , Plasmócitos/metabolismo , Imunidade Adaptativa , Transferência Adotiva , Animais , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/parasitologia , Linfócitos T CD4-Positivos/transplante , Proliferação de Células , Células Cultivadas , Switching de Imunoglobulina , Imunoglobulina E/química , Imunoglobulina E/genética , Imunoglobulina G/química , Interleucina-13/genética , Interleucina-4/genética , Linfonodos/imunologia , Linfonodos/metabolismo , Linfonodos/parasitologia , Linfonodos/patologia , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Nippostrongylus/imunologia , Plasmócitos/citologia , Plasmócitos/imunologia , Plasmócitos/parasitologia , Domínios e Motivos de Interação entre Proteínas , Baço/imunologia , Baço/metabolismo , Baço/parasitologia , Baço/patologia , Infecções por Strongylida/imunologia , Infecções por Strongylida/metabolismo , Infecções por Strongylida/parasitologia , Infecções por Strongylida/patologia
6.
Proc Natl Acad Sci U S A ; 111(48): E5169-77, 2014 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-25404305

RESUMO

Basophils orchestrate protection against reinfections with gastrointestinal helminths and ticks, but the underlying mechanisms remain elusive. We investigated the role of Fc receptors on basophils, the antibody isotypes IgG1 and IgE, and basophil-derived IL-4/IL-13 during challenge infections with Heligmosomoides polygyrus and Nippostrongylus brasiliensis. Using mixed bone marrow chimeras, we found that activating Fc receptors on basophils were required for protective immunity but not for regulation of basophil homeostasis. Furthermore, rapid worm expulsion was impaired in IgE-deficient but not in IgG1-deficient mice. Basophils promoted the recruitment of other effector cells into the small intestine and induced expression of the antihelminthic proteins resistin-like molecule ß and mucin 5ac. Selective deletion of IL-4/IL-13 in basophils resulted in impaired worm expulsion. Collectively, our results indicate that IgE-mediated activation of basophils and the release of basophil-derived IL-4/IL-13 are critical steps in protective immunity against helminths. Therefore, development of effective vaccines against helminths should consider boosting the IL-4/IgE/basophil axis of the immune system.


Assuntos
Basófilos/imunologia , Citocinas/imunologia , Trato Gastrointestinal/imunologia , Heligmosomatoidea/imunologia , Imunoglobulina E/imunologia , Infecções por Strongylida/imunologia , Animais , Basófilos/metabolismo , Basófilos/parasitologia , Western Blotting , Citocinas/metabolismo , Citometria de Fluxo , Trato Gastrointestinal/metabolismo , Trato Gastrointestinal/parasitologia , Heligmosomatoidea/fisiologia , Interações Hospedeiro-Parasita/imunologia , Imunoglobulina E/genética , Imunoglobulina E/metabolismo , Interleucina-13/genética , Interleucina-13/imunologia , Interleucina-13/metabolismo , Interleucina-4/genética , Interleucina-4/imunologia , Interleucina-4/metabolismo , Intestino Delgado/imunologia , Intestino Delgado/metabolismo , Intestino Delgado/parasitologia , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Nematospiroides dubius/imunologia , Nematospiroides dubius/fisiologia , Nippostrongylus/imunologia , Nippostrongylus/fisiologia , Receptores Fc/genética , Receptores Fc/imunologia , Receptores Fc/metabolismo , Infecções por Strongylida/metabolismo , Infecções por Strongylida/parasitologia , Células Th2/imunologia , Células Th2/metabolismo
7.
Proc Natl Acad Sci U S A ; 111(11): 4239-44, 2014 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-24591640

RESUMO

Phospholipase Cε (PLCε) has been characterized as a direct effector of Ras in vitro and in cellular systems; however, the role of PLCε in tumorigenesis and its link to Ras in this context remain unclear. To assess the role of PLCε in Ras-driven cancers, we generated two new mouse strains: one carrying a targeted deletion of Plce (Plce(-/-)) and the other carrying mutant alleles of Plce unable to bind to Ras (Plce(RAm/RAm)). The Plce(-/-) and, to a lesser degree, Plce(RAm/RAm) transgenic mice exhibited increased susceptibility to tumor formation in the two-stage skin carcinogenesis protocol, revealing a tumor suppressor function for this PLC. This result also suggests that in this context Ras binding in part regulates functions of PLCε. Although significant differences were not seen in the LSL-Kras(G12D) nonsmall cell lung carcinoma model, down-regulation of PLCε was found in animal tumors and in cellular systems following expression of the oncogenic Ras. An inhibitory impact of PLCε on cell growth requires intact lipase activity and is likely mediated by protein kinase C enzymes. Further cellular studies suggest involvement of histone deacetylase in the mechanism of PLCε down-regulation. Taken together, our results show a previously unidentified tumor suppressor role for this PLC in animal models and, together with observations of marked down-regulation in colorectal, lung, and skin tumors, suggest its use as a biological marker in cancer.


Assuntos
Regulação Neoplásica da Expressão Gênica/fisiologia , Genes Supressores de Tumor/fisiologia , Genes ras/genética , Neoplasias/genética , Fosfoinositídeo Fosfolipase C/fisiologia , Animais , Proliferação de Células , Regulação Neoplásica da Expressão Gênica/genética , Humanos , Imuno-Histoquímica , Hibridização In Situ , Camundongos , Camundongos Transgênicos , Fosfoinositídeo Fosfolipase C/genética , Proteína Quinase C/metabolismo , Reação em Cadeia da Polimerase em Tempo Real
8.
Eur J Immunol ; 45(3): 695-704, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-25501566

RESUMO

In general, a long-lasting immune response to viruses is achieved when they are infectious and replication competent. In the mouse, the neutralizing antibody response to Friend murine leukemia virus is contributed by an allelic form of the enzyme Apobec3 (abbreviated A3). This is counterintuitive because A3 directly controls viremia before the onset of adaptive antiviral immune responses. It suggests that A3 also affects the antibody response directly. Here, we studied the relative size of cell populations of the adaptive immune system as a function of A3 activity. We created a transgenic mouse that expresses all seven human A3 enzymes and compared it to WT and mouse A3-deficient mice. A3 enzymes decreased the number of marginal zone B cells, but not the number of follicular B or T cells. When mouse A3 was knocked out, the retroelement hitchhiker-1 and sialyl transferases encoded by genes close to it were overexpressed three and two orders of magnitude, respectively. We suggest that A3 shifts the balance, from the fast antibody response mediated by marginal zone B cells with little affinity maturation, to a more sustained germinal center B-cell response, which drives affinity maturation and, thereby, a better neutralizing response.


Assuntos
Formação de Anticorpos , Linfócitos B/imunologia , Citidina Desaminase/imunologia , Citosina Desaminase/imunologia , Centro Germinativo/imunologia , Desaminases APOBEC , Animais , Citidina Desaminase/genética , Citosina Desaminase/genética , Humanos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Viroses/genética , Viroses/imunologia , Viroses/patologia
9.
EMBO J ; 30(13): 2705-18, 2011 May 27.
Artigo em Inglês | MEDLINE | ID: mdl-21623346

RESUMO

The quality and quantity of BCR signals impact on cell fate decisions of B lymphocytes. Here, we describe novel gene-targeted mice, which in the context of normal VDJ recombination show hypomorphic expression of immunoglobulin µ heavy chain (µHC) mRNA levels and hence lower pre-BCR and BCR levels. Hypomorphic expression of µHC leads to augmented selection processes at all stages of B-cell development, noticeably at the expansion of pre-B cells, the positive selection of immature B lymphocytes in the bone marrow and the selection of the follicular (FO), marginal zone (MZ) and B1 B-lymphocyte compartment in peripheral lymphoid organs. Immature as well as mature FO and MZ B lymphocytes in the peripheral lymphoid organs express lower levels of the receptor for B-cell activating factor (BAFF). In addition, hypomorphic expression of the BCR favours receptor editing. Together, our results highlight the critical importance of pre-BCR and BCR receptor levels for the normal development of B-lymphocyte subpopulations in the context of intact VDJ recombination and a diverse antibody repertoire.


Assuntos
Subpopulações de Linfócitos B/fisiologia , Diferenciação Celular/imunologia , Genes de Cadeia Pesada de Imunoglobulina/fisiologia , Receptores de Antígenos de Linfócitos B/imunologia , Receptores de Antígenos de Linfócitos B/metabolismo , Alelos , Animais , Formação de Anticorpos/genética , Formação de Anticorpos/fisiologia , Receptor do Fator Ativador de Células B/metabolismo , Subpopulações de Linfócitos B/metabolismo , Células da Medula Óssea/imunologia , Células da Medula Óssea/metabolismo , Células da Medula Óssea/fisiologia , Diferenciação Celular/genética , Células Cultivadas , Genes de Cadeia Pesada de Imunoglobulina/genética , Cadeias mu de Imunoglobulina/genética , Cadeias mu de Imunoglobulina/metabolismo , Lectinas/genética , Lectinas/imunologia , Lectinas/metabolismo , Camundongos , Camundongos Transgênicos , Células Precursoras de Linfócitos B/imunologia , Células Precursoras de Linfócitos B/metabolismo , Células Precursoras de Linfócitos B/fisiologia , Receptores de Antígenos de Linfócitos B/genética , Lectinas Semelhantes a Imunoglobulina de Ligação ao Ácido Siálico
10.
Eur J Immunol ; 43(5): 1231-42, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23423996

RESUMO

Immunoglobulin E (IgE) production is tightly regulated at the cellular and genetic levels and is believed to be central to allergy development. At least two cellular pathways exist that lead to systemic anaphylaxis reactions in vivo: IgE-sensitized mast cells and IgG1-sensitized basophils. Passive anaphylaxis, by application of allergen and allergen-specific antibodies in mice, indicates a differential contribution of immunoglobulin isotypes to anaphylaxis. However, analysis of a dynamic immunization-mediated antibody response in anaphylaxis is difficult. Here, we generated IgE knock-in mice (IgE(ki) ), which express the IgE heavy chain instead of IgG1, in order to analyze the contribution of IgG1 and IgE to active anaphylaxis in vivo. IgE(ki) mice display increased IgE production both in vitro and in vivo. The sensitization of IgE(ki) mice by immunization followed by antigen challenge leads to increased anaphylaxis. Homozygous IgE(ki) mice, which lack IgG1 due to the knock-in strategy, are most susceptible to active systemic anaphylaxis. The depletion of basophils demonstrates their importance in IgE-mediated anaphylaxis. Therefore, we propose that an enhanced, antigen-specific, polyclonal IgE response, as is the case in allergic patients, is probably the most efficient way to sensitize basophils to contribute to systemic anaphylaxis in vivo.


Assuntos
Anafilaxia/imunologia , Anafilaxia/patologia , Basófilos/imunologia , Basófilos/patologia , Imunoglobulina E/imunologia , Imunoglobulina G/imunologia , Alérgenos/administração & dosagem , Alérgenos/imunologia , Anafilaxia/genética , Animais , Anticorpos Monoclonais/biossíntese , Anticorpos Monoclonais/imunologia , Técnicas de Introdução de Genes , Homozigoto , Humanos , Imunização , Imunoglobulina E/genética , Imunoglobulina G/genética , Mastócitos/imunologia , Mastócitos/patologia , Camundongos , Ovalbumina/administração & dosagem , Ovalbumina/imunologia , Índice de Gravidade de Doença
11.
Arch Med Res ; 55(3): 102985, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38520880

RESUMO

BACKGROUND: Toll-like receptors (TLRs) play a critical role in initiating the innate immune response to infection or injury. Recent studies have uncovered their intriguing functions as moonlighting proteins involved in various biological processes, including development, learning, and memory. However, the specific functions of individual TLRs are still largely unknown. AIMS: We investigated the effects of TLR3 and TLR9 receptor deficiency on motor, cognitive, and behavioral functions during development using genetically modified male mice of different ages. METHODS: We evaluated the motor coordination, anxiety-like behavior, spatial learning, and working memory of male mice lacking the TLR3 and TLR9 genes at different ages (two, four, six, and eight months) using the rotarod, open field, water maze, and T-maze tests. RESULTS: We observed that the deletion of either TLR3 or TLR9 resulted in impaired motor performance. Furthermore, young TLR3-deficient mice exhibited reduced anxiety-like behavior and spatial learning deficits; however, their working memory was unaffected. In contrast, young TLR9-knockout mice showed hyperactivity and a tendency toward decreased working memory. CONCLUSIONS: These findings provide valuable insights into the broader roles of the TLR system beyond the innate immune response, revealing its involvement in pathways associated with the central nervous system. Importantly, our results establish a strong association between the endosomal receptors TLR3 and TLR9 and the performance of motor, cognitive, and behavioral tasks that change over time. This study contributes to the growing body of research on the multifaceted functions of TLRs and enhances our understanding of their participation in non-immune-related processes.


Assuntos
Receptor 3 Toll-Like , Receptor Toll-Like 9 , Animais , Masculino , Camundongos , Cognição , Camundongos Knockout , Receptor 3 Toll-Like/genética , Receptor 3 Toll-Like/metabolismo , Receptor Toll-Like 9/genética , Receptores Toll-Like/genética , Receptores Toll-Like/metabolismo
12.
Nat Commun ; 15(1): 1229, 2024 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-38336876

RESUMO

Endogenous retroviruses (ERVs) are an integral part of the mammalian genome. The role of immune control of ERVs in general is poorly defined as is their function as anti-cancer immune targets or drivers of autoimmune disease. Here, we generate mouse-strains where Moloney-Murine Leukemia Virus tagged with GFP (ERV-GFP) infected the mouse germline. This enables us to analyze the role of genetic, epigenetic and cell intrinsic restriction factors in ERV activation and control. We identify an autoreactive B cell response against the neo-self/ERV antigen GFP as a key mechanism of ERV control. Hallmarks of this response are spontaneous ERV-GFP+ germinal center formation, elevated serum IFN-γ levels and a dependency on Age-associated B cells (ABCs) a subclass of T-bet+ memory B cells. Impairment of IgM B cell receptor-signal in nucleic-acid sensing TLR-deficient mice contributes to defective ERV control. Although ERVs are a part of the genome they break immune tolerance, induce immune surveillance against ERV-derived self-antigens and shape the host immune response.


Assuntos
Linfócitos B , Retrovirus Endógenos , Animais , Camundongos , Doenças Autoimunes/genética , Linfócitos B/imunologia , Retrovirus Endógenos/genética , Mamíferos/genética
13.
Antibodies (Basel) ; 12(1)2023 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-36648888

RESUMO

The B cell antigen receptor (BCR)-repertoire is capable of recognizing a nearly unlimited number of antigens. Inevitably, the random nature of antibody gene segment rearrangement, needed in order to provide mature B cells, will generate autoreactive specificities. Once tolerance mechanisms fail to block the activation and differentiation of autoreactive B cells, harmful autoantibodies may get secreted establishing autoimmune diseases. Besides the hallmark of autoimmunity, namely IgG autoantibodies, IgM autoantibodies are also found in many autoimmune diseases. In addition to pathogenic functions of secreted IgM the IgM-BCR expressing B cell might be the initial check-point where, in conjunction with innate receptor signals, B cell mediated autoimmunity starts it fateful course. Recently, pentameric IgM autoantibodies have been shown to contribute significantly to the pathogenesis of various autoimmune diseases, such as rheumatoid arthritis (RA), autoimmune hemolytic anemia (AIHA), pemphigus or autoimmune neuropathy. Further, recent studies suggest differences in the recognition of autoantigen by IgG and IgM autoantibodies, or propose a central role of anti-ACE2-IgM autoantibodies in severe COVID-19. However, exact mechanisms still remain to be uncovered in detail. This article focuses on summarizing recent findings regarding the importance of autoreactive IgM in establishing autoimmune diseases.

14.
Arthritis Rheum ; 63(5): 1301-11, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21305534

RESUMO

OBJECTIVE: It is difficult to identify a single causative factor for inflammatory arthritis because of the multifactorial nature of the disease. This study was undertaken to dissect the molecular complexity of systemic inflammatory disease, utilizing a combined approach of mutagenesis and systematic phenotype screening in a murine model. METHODS: In a large-scale N-ethyl-N-nitrosourea mutagenesis project, the Ali14 mutant mouse strain was established because of dominant inheritance of spontaneous swelling and inflammation of the hind paws. Genetic mapping and subsequent candidate gene sequencing were conducted to find the causative gene, and systematic phenotyping of Ali14/+ mice was performed in the German Mouse Clinic. RESULTS: A novel missense mutation in the phospholipase Cγ2 gene (Plcg2) was identified in Ali14/+ mice. Because of the hyperreactive external entry of calcium observed in cultured B cells and other in vitro experiments, the Ali14 mutation is thought to be a novel gain-of-function allele of Plcg2. Findings from systematic screening of Ali14/+ mice demonstrated various phenotypic changes: an abnormally high T cell:B cell ratio, up-regulation of Ig, alterations in body composition, and a reduction in cholesterol and triglyceride levels in peripheral blood. In addition, spermatozoa from Ali14/+ mice failed to fertilize eggs in vitro, despite the normal fertility of the Ali14/+ male mice in vivo. CONCLUSION: These results suggest that the Plcg2-mediated pathways play a crucial role in various metabolic and sperm functions, in addition to initiating and maintaining the immune system. These findings may indicate the importance of the Ali14/+ mouse strain as a model for systemic inflammatory diseases and inflammation-related metabolic changes in humans.


Assuntos
Artrite Experimental/genética , Composição Corporal/genética , Infertilidade Masculina/genética , Fosfolipase C gama/genética , Animais , Etilnitrosoureia/farmacologia , Citometria de Fluxo , Masculino , Camundongos , Camundongos Mutantes , Mutagênese/efeitos dos fármacos , Mutação/efeitos dos fármacos , Polimorfismo de Nucleotídeo Único , Motilidade dos Espermatozoides/genética
15.
J Biol Chem ; 284(34): 23083-93, 2009 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-19531496

RESUMO

Phospholipase C gamma isozymes (PLC gamma 1 and PLC gamma 2) have a crucial role in the regulation of a variety of cellular functions. Both enzymes have also been implicated in signaling events underlying aberrant cellular responses. Using N-ethyl-N-nitrosourea (ENU) mutagenesis, we have recently identified single point mutations in murine PLC gamma 2 that lead to spontaneous inflammation and autoimmunity. Here we describe further, mechanistic characterization of two gain-of-function mutations, D993G and Y495C, designated as ALI5 and ALI14. The residue Asp-993, mutated in ALI5, is a conserved residue in the catalytic domain of PLC enzymes. Analysis of PLC gamma 1 and PLC gamma 2 with point mutations of this residue showed that removal of the negative charge enhanced PLC activity in response to EGF stimulation or activation by Rac. Measurements of PLC activity in vitro and analysis of membrane binding have suggested that ALI5-type mutations facilitate membrane interactions without compromising substrate binding and hydrolysis. The residue mutated in ALI14 (Tyr-495) is within the spPH domain. Replacement of this residue had no effect on folding of the domain and enhanced Rac activation of PLC gamma 2 without increasing Rac binding. Importantly, the activation of the ALI14-PLC gamma 2 and corresponding PLC gamma 1 variants was enhanced in response to EGF stimulation and bypassed the requirement for phosphorylation of critical tyrosine residues. ALI5- and ALI14-type mutations affected basal activity only slightly; however, their combination resulted in a constitutively active PLC. Based on these data, we suggest that each mutation could compromise auto-inhibition in the inactive PLC, facilitating the activation process; in addition, ALI5-type mutations could enhance membrane interaction in the activated state.


Assuntos
Mutação/genética , Fosfolipase C gama/química , Fosfolipase C gama/metabolismo , Alquilantes/farmacologia , Sequência de Aminoácidos , Animais , Células COS , Calorimetria , Domínio Catalítico , Linhagem Celular , Chlorocebus aethiops , Drosophila , Etilnitrosoureia/farmacologia , Isoenzimas , Espectroscopia de Ressonância Magnética , Camundongos , Dados de Sequência Molecular , Mutação/efeitos dos fármacos , Fosfolipase C gama/genética , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína/genética , Estrutura Terciária de Proteína/fisiologia , Homologia de Sequência de Aminoácidos , Relação Estrutura-Atividade , Ressonância de Plasmônio de Superfície
16.
J Clin Invest ; 117(11): 3540-50, 2007 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17965774

RESUMO

Changes in cytoplasmic Ca2+ levels regulate a variety of fundamental cellular functions in virtually all cells. In nonexcitable cells, a major pathway of Ca2+ entry involves receptor-mediated depletion of intracellular Ca2+ stores followed by the activation of store-operated calcium channels in the plasma membrane. We have established a mouse line expressing an activating EF hand motif mutant of stromal interaction molecule 1 (Stim1), an ER receptor recently identified as the Ca2+ sensor responsible for activation of Ca2+ release-activated (CRAC) channels in T cells, whose function in mammalian physiology is not well understood. Mice expressing mutant Stim1 had macrothrombocytopenia and an associated bleeding disorder. Basal intracellular Ca2+ levels were increased in platelets, which resulted in a preactivation state, a selective unresponsiveness to immunoreceptor tyrosine activation motif-coupled agonists, and increased platelet consumption. In contrast, basal Ca2+ levels, but not receptor-mediated responses, were affected in mutant T cells. These findings identify Stim1 as a central regulator of platelet function and suggest a cell type-specific activation or composition of the CRAC complex.


Assuntos
Cálcio/metabolismo , Motivos EF Hand/genética , Hemorragia , Glicoproteínas de Membrana/metabolismo , Mutação , Ativação Plaquetária , Trombocitopenia , Animais , Medula Óssea/patologia , Canais de Cálcio/metabolismo , Fibrose/patologia , Hemorragia/genética , Hemorragia/metabolismo , Megacariócitos/citologia , Megacariócitos/metabolismo , Glicoproteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos , Ativação Plaquetária/genética , Glicoproteínas da Membrana de Plaquetas/metabolismo , Transdução de Sinais/fisiologia , Esplenomegalia/metabolismo , Molécula 1 de Interação Estromal , Linfócitos T/citologia , Linfócitos T/metabolismo , Trombocitopenia/genética , Trombocitopenia/metabolismo
17.
Immunobiology ; 224(6): 843-851, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31521407

RESUMO

The innate immune system senses viral and bacterial RNA or DNA via different cytoplasmic or endosomal localized pattern recognition receptors. In general, the preference of these receptors for single-stranded (ss), double-stranded (ds) RNA or DNA has been thoroughly characterized. Recently, RNA-DNA hybrids have also been identified as ligands for pattern recognition receptors such as Toll-like receptor 9 (TLR9). However, a comparison of RNA-DNA hybrids and ssDNA in terms of TLR9 stimulation potential and intracellular stability has not been addressed. RNA-DNA hybrids are formed transiently during normal cellular processes (e.g. replication), consist as part of some viral genomes (e.g. cytomegalovirus (CMV) or hepatitis B virus (HBV)) and exist during retroviral infection. Here we report that virus-derived synthetic RNA-DNA hybrids stimulate human peripheral blood mononuclear cells (PBMCs) as well as murine FMS-like tyrosine kinase 3 ligand (FLT3L) induced dendritic cells to secrete interferon alpha (IFN-α) in a TLR9-dependent manner. Furthermore, we could show that RNA-DNA hybrids exhibit increased intracellular stability, which correlates with enhanced activation of TLR9 in comparison to corresponding ssDNA. Overall, these data suggest a prominent role for TLR9 in the immune recognition of RNA-DNA hybrids in retroviral and CMV infection.


Assuntos
Citomegalovirus/genética , DNA Viral , HIV-1/genética , RNA Viral , Receptor Toll-Like 9/imunologia , Animais , Linhagem Celular , DNA de Cadeia Simples , Células Dendríticas/imunologia , Células Dendríticas/virologia , Humanos , Interferon-alfa/imunologia , Leucócitos Mononucleares/imunologia , Leucócitos Mononucleares/virologia , Proteínas de Membrana/imunologia , Camundongos
18.
Immunobiology ; 213(2): 151-7, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18241699

RESUMO

The immune response induced by the pathogen-associated-pattern recognition receptor toll-like receptor 9 (TLR9) upon binding of CpG motif-containing DNA has been widely accepted as an important pathway in the immune defense against microbial pathogens. In contrast, the role of TLR9 in anti-DNA antibody generation and the pathogenesis of systemic lupus erythematosus (SLE) remains controversial. Indeed, the in vivo situation might consist of a delicate balance between B-cell receptor and DNA receptor signaling. Most surprisingly, TLR9 deletion does not ameliorate but rather exacerbates pathology in murine models. Such observations warrant caution with therapeutic efforts to treat autoimmune diseases, especially SLE, via TLR modulation.


Assuntos
Deleção de Genes , Lúpus Eritematoso Sistêmico/imunologia , Polimorfismo Genético , Receptor Toll-Like 9/metabolismo , Animais , Modelos Animais de Doenças , Humanos , Lúpus Eritematoso Sistêmico/genética , Camundongos , Receptor Toll-Like 9/genética
19.
J Exp Med ; 215(8): 2035-2053, 2018 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-29959173

RESUMO

To what extent immune responses against the gut flora are compartmentalized within mucosal tissues in homeostatic conditions remains a much-debated issue. We describe here, based on an inducible AID fate-mapping mouse model, that systemic memory B cell subsets, including mainly IgM+ B cells in spleen, together with IgA+ plasma cells in spleen and bone marrow, are generated in mice in the absence of deliberate immunization. While the IgA component appears dependent on the gut flora, IgM memory B cells are still generated in germ-free mice, albeit to a reduced extent. Clonal relationships and renewal kinetics after anti-CD20 treatment reveal that this long-lasting splenic population is mainly sustained by output of B cell clones persisting in mucosal germinal centers. IgM-secreting hybridomas established from splenic IgM memory B cells showed reactivity against various bacterial isolates and endogenous retroviruses. Ongoing activation of B cells in gut-associated lymphoid tissues thus generates a diversified systemic compartment showing long-lasting clonal persistence and protective capacity against systemic bacterial infections.


Assuntos
Antibacterianos/imunologia , Imunidade nas Mucosas , Imunoglobulina M/metabolismo , Memória Imunológica , Baço/imunologia , Envelhecimento/imunologia , Animais , Antígenos CD/metabolismo , Linfócitos B/imunologia , Proteínas de Bactérias/metabolismo , Medula Óssea/metabolismo , Citidina Desaminase/metabolismo , Microbioma Gastrointestinal , Vida Livre de Germes , Centro Germinativo/citologia , Imunização , Imunoglobulina A/metabolismo , Cinética , Proteínas Luminescentes/metabolismo , Camundongos , Mutação/genética , Plasmócitos/citologia , Transdução de Sinais , Linfócitos T/metabolismo , Receptores Toll-Like/metabolismo
20.
Immunobiology ; 212(6): 521-33, 2007.
Artigo em Inglês | MEDLINE | ID: mdl-17544836

RESUMO

Allergic diseases prevalence rates have increased dramatically over the last 50 years in developed countries and one explanation might be that modern practices in public health lead to a decreased exposure towards pathogens resulting in a misguided immune response. Recently, it has become evident that immune responses against pathogens are initiated by Toll-like receptors (TLRs) that recognize a variety of structures derived from viruses, bacteria, fungi or protozoa. In this review we will discuss TLR ligands, TLR signaling in regard to Th1 and Th2 immune responses, their involvement in the development and their therapeutic potential in treatment of allergic disease.


Assuntos
Hipersensibilidade/imunologia , Transdução de Sinais/imunologia , Células Th1/imunologia , Células Th2/imunologia , Receptores Toll-Like/imunologia , Animais , Bactérias/imunologia , Eucariotos/imunologia , Fungos/imunologia , Humanos , Hipersensibilidade/terapia , Vírus/imunologia
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