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Van Goethem E, Silva EA, Xiao H, Franc NC. The Drosophila TRPP cation channel, PKD2 and Dmel/Ced-12 act in genetically distinct pathways during apoptotic cell clearance. PLoS One 2012; 7:e31488. [PMID: 22347485 PMCID: PMC3275576 DOI: 10.1371/journal.pone.0031488] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Accepted: 01/09/2012] [Indexed: 11/18/2022] Open
Abstract
Apoptosis, a genetically programmed cell death, allows for homeostasis and tissue remodelling during development of all multi-cellular organisms. Phagocytes swiftly recognize, engulf and digest apoptotic cells. Yet, to date the molecular mechanisms underlying this phagocytic process are still poorly understood. To delineate the molecular mechanisms of apoptotic cell clearance in Drosophila, we have carried out a deficiency screen and have identified three overlapping phagocytosis-defective mutants, which all delete the fly homologue of the ced-12 gene, known as Dmel\ced12. As anticipated, we have found that Dmel\ced-12 is required for apoptotic cell clearance, as for its C. elegans and mammalian homologues, ced-12 and elmo, respectively. However, the loss of Dmel\ced-12 did not solely account for the phenotypes of all three deficiencies, as zygotic mutations and germ line clones of Dmel\ced-12 exhibited weaker phenotypes. Using a nearby genetically interacting deficiency, we have found that the polycystic kidney disease 2 gene, pkd2, which encodes a member of the TRPP channel family, is also required for phagocytosis of apoptotic cells, thereby demonstrating a novel role for PKD2 in this process. We have also observed genetic interactions between pkd2, simu, drpr, rya-r44F, and retinophilin (rtp), also known as undertaker (uta), a gene encoding a MORN-repeat containing molecule, which we have recently found to be implicated in calcium homeostasis during phagocytosis. However, we have not found any genetic interaction between Dmel\ced-12 and simu. Based on these genetic interactions and recent reports demonstrating a role for the mammalian pkd-2 gene product in ER calcium release during store-operated calcium entry, we propose that PKD2 functions in the DRPR/RTP pathway to regulate calcium homeostasis during this process. Similarly to its C. elegans homologue, Dmel\Ced-12 appears to function in a genetically distinct pathway.
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Affiliation(s)
- Emeline Van Goethem
- Medical Research Council Cell Biology Unit, MRC Laboratory for Molecular Cell Biology and Anatomy and Developmental Biology Department, University College London, London, United Kingdom
| | - Elizabeth A. Silva
- Medical Research Council Cell Biology Unit, MRC Laboratory for Molecular Cell Biology and Anatomy and Developmental Biology Department, University College London, London, United Kingdom
| | - Hui Xiao
- The Department of Genetics, Affiliated to the Department of Immunology and Microbial Sciences, The Scripps Research Institute, La Jolla, California, United States of America
| | - Nathalie C. Franc
- The Department of Genetics, Affiliated to the Department of Immunology and Microbial Sciences, The Scripps Research Institute, La Jolla, California, United States of America
- * E-mail:
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252
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Ucker DS, Jain MR, Pattabiraman G, Palasiewicz K, Birge RB, Li H. Externalized glycolytic enzymes are novel, conserved, and early biomarkers of apoptosis. J Biol Chem 2012; 287:10325-10343. [PMID: 22262862 DOI: 10.1074/jbc.m111.314971] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The intriguing cell biology of apoptotic cell death results in the externalization of numerous autoantigens on the apoptotic cell surface, including protein determinants for specific recognition, linked to immune responses. Apoptotic cells are recognized by phagocytes and trigger an active immunosuppressive response ("innate apoptotic immunity" (IAI)) even in the absence of engulfment. IAI is responsible for the lack of inflammation associated normally with the clearance of apoptotic cells; its failure also has been linked to inflammatory and autoimmune pathology, including systemic lupus erythematosus and rheumatic diseases. Apoptotic recognition determinants underlying IAI have yet to be identified definitively; we argue that these molecules are surface-exposed (during apoptotic cell death), ubiquitously expressed, protease-sensitive, evolutionarily conserved, and resident normally in viable cells (SUPER). Using independent and unbiased quantitative proteomic approaches to characterize apoptotic cell surface proteins and identify candidate SUPER determinants, we made the surprising discovery that components of the glycolytic pathway are enriched on the apoptotic cell surface. Our data demonstrate that glycolytic enzyme externalization is a common and early aspect of cell death in different cell types triggered to die with distinct suicidal stimuli. Exposed glycolytic enzyme molecules meet the criteria for IAI-associated SUPER determinants. In addition, our characterization of the apoptosis-specific externalization of glycolytic enzyme molecules may provide insight into the significance of previously reported cases of plasminogen binding to α-enolase on mammalian cells, as well as mechanisms by which commensal bacteria and pathogens maintain immune privilege.
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Affiliation(s)
- David S Ucker
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, Illinois 60612 and.
| | - Mohit Raja Jain
- Center for Advanced Proteomics Research, UMDNJ-New Jersey Medical School Cancer Center, Newark, New Jersey 07214; Department of Biochemistry and Molecular Biology, UMDNJ-New Jersey Medical School Cancer Center, Newark, New Jersey 07214
| | - Goutham Pattabiraman
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, Illinois 60612 and
| | - Karol Palasiewicz
- Department of Microbiology and Immunology, University of Illinois College of Medicine, Chicago, Illinois 60612 and
| | - Raymond B Birge
- Department of Biochemistry and Molecular Biology, UMDNJ-New Jersey Medical School Cancer Center, Newark, New Jersey 07214
| | - Hong Li
- Center for Advanced Proteomics Research, UMDNJ-New Jersey Medical School Cancer Center, Newark, New Jersey 07214; Department of Biochemistry and Molecular Biology, UMDNJ-New Jersey Medical School Cancer Center, Newark, New Jersey 07214.
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253
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Sang A, Yin Y, Zheng YY, Morel L. Animal Models of Molecular Pathology. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 105:321-70. [DOI: 10.1016/b978-0-12-394596-9.00010-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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254
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Theofilopoulos AN, Kono DH, Beutler B, Baccala R. Intracellular nucleic acid sensors and autoimmunity. J Interferon Cytokine Res 2011; 31:867-86. [PMID: 22029446 DOI: 10.1089/jir.2011.0092] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
A collection of molecular sensors has been defined by studies in the last decade that can recognize a diverse array of pathogens and initiate protective immune and inflammatory responses. However, if the molecular signatures recognized are shared by both foreign and self-molecules, as is the case of nucleic acids, then the responses initiated by these sensors may have deleterious consequences. Notably, this adverse occurrence may be of primary importance in autoimmune disease pathogenesis. In this case, microbe-induced damage or mishandled physiologic processes could lead to the generation of microparticles containing self-nucleic acids. These particles may inappropriately gain access to the cytosol or endolysosomes and, hence, engage resident RNA and DNA sensors. Evidence, as reviewed here, strongly indicates that these sensors are primary contributors to autoimmune disease pathogenesis, spearheading efforts toward development of novel therapeutics for these disorders.
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Affiliation(s)
- Argyrios N Theofilopoulos
- Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, California 92137, USA.
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255
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Pathak S, Mohan C. Cellular and molecular pathogenesis of systemic lupus erythematosus: lessons from animal models. Arthritis Res Ther 2011; 13:241. [PMID: 21989039 PMCID: PMC3308079 DOI: 10.1186/ar3465] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Systemic lupus erythematosus (SLE) is a complex disease characterized by the appearance of autoantibodies against nuclear antigens and the involvement of multiple organ systems, including the kidneys. The precise immunological events that trigger the onset of clinical manifestations of SLE are not yet well understood. However, research using various mouse strains of spontaneous and inducible lupus in the last two decades has provided insights into the role of the immune system in the pathogenesis of this disease. According to our present understanding, the immunological defects resulting in the development of SLE can be categorized into two phases: (a) systemic autoimmunity resulting in increased serum antinuclear and antiglomerular autoantibodies and (b) immunological events that occur within the target organ and result in end organ damage. Aberrations in the innate as well as adaptive arms of the immune system both play an important role in the genesis and progression of lupus. Here, we will review the present understanding - as garnered from studying mouse models - about the roles of various immune cells in lupus pathogenesis.
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Affiliation(s)
- Simanta Pathak
- Department of Internal Medicine (Rheumatology), University of Texas, Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75235, USA
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256
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Gu BJ, Saunders BM, Petrou S, Wiley JS. P2X(7) is a scavenger receptor for apoptotic cells in the absence of its ligand, extracellular ATP. THE JOURNAL OF IMMUNOLOGY 2011; 187:2365-75. [PMID: 21821797 DOI: 10.4049/jimmunol.1101178] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Phagocytosis of apoptotic cells is essential during development and tissue remodeling. Our previous study has shown that the P2X(7) receptor regulates phagocytosis of nonopsonized particles and bacteria. In this study, we demonstrate that P2X(7) also mediates phagocytosis of apoptotic lymphocytes and neuronal cells by human monocyte-derived macrophages under serum-free conditions. ATP inhibited this process to a similar extent as observed with cytochalasin D. P2X(7)-transfected HEK-293 cells acquired the ability to phagocytose apoptotic lymphocytes. Injection of apoptotic thymocytes into the peritoneal cavity of wild-type mice resulted in their phagocytosis by macrophages, but injection of ATP prior to thymocytes markedly decreased this uptake. In contrast, ATP failed to inhibit phagocytosis of apoptotic thymocytes in vivo by P2X(7)-deficient peritoneal macrophages. The surface expression of P2X(7) on phagocytes increased significantly during phagocytosis of either beads or apoptotic cells. A peptide screen library containing 24 biotin-conjugated peptides mimicking the extracellular domain of P2X(7) was used to evaluate the binding profile to beads, bacteria, and apoptotic cells. One peptide showed binding to all particles and cell membrane lipids. Three other cysteine-containing peptides uniquely bound the surface of apoptotic cells but not viable cells, whereas substitution of alanine for cysteine abolished peptide binding. Several thiol-reactive compounds including N-acetyl-L-cysteine abolished phagocytosis of apoptotic SH-SY5Y cells by macrophages. These data suggest that the P2X(7) receptor in its unactivated state acts like a scavenger receptor, and its extracellular disulphide bonds play an important role in direct recognition and engulfment of apoptotic cells.
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Affiliation(s)
- Ben J Gu
- Sydney Medical School Nepean, University of Sydney, Nepean Hospital, Penrith, New South Wales 2750, Australia
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257
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Kenyon KD, Cole C, Crawford F, Kappler JW, Thurman JM, Bratton DL, Boackle SA, Henson PM. IgG autoantibodies against deposited C3 inhibit macrophage-mediated apoptotic cell engulfment in systemic autoimmunity. THE JOURNAL OF IMMUNOLOGY 2011; 187:2101-11. [PMID: 21813769 DOI: 10.4049/jimmunol.1003468] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Defective clearance of apoptotic cells has been shown in systemic lupus erythematosus (SLE) and is postulated to enhance autoimmune responses by increasing access to intracellular autoantigens. Until now, research has emphasized inherited rather than acquired impairment of apoptotic cell engulfment in the pathogenesis of SLE. In this study, we confirm previous results that efficient removal of apoptotic cells (efferocytosis) is bolstered in the presence of wild-type mouse serum, through the C3 deposition on the apoptotic cell surface. In contrast, sera from three mouse models of SLE, Mer(KD), MRL(lpr), and New Zealand Black/WF1 did not support and in fact actively inhibited apoptotic cell uptake. IgG autoantibodies were responsible for the inhibition, through the blockade of C3 recognition by macrophages. Consistent with this, IgG removal reversed the inhibitory activity within autoimmune serum, and purified autoimmune IgG blocked both the detection of C3 on apoptotic cells and C3-dependent efferocytosis. Sera from SLE patients demonstrated elevated anti-C3b IgG that blocked detection of C3 on apoptotic cells, activity that was not found in healthy controls or patients with rheumatoid arthritis, nor in mice prior to the onset of autoimmunity. We propose that the suppression of apoptotic cell disposal by Abs against deposited C3 may contribute to increasing severity and/or exacerbations in SLE.
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Affiliation(s)
- Karla D Kenyon
- Department of Pediatrics, National Jewish Health, Denver, CO 80206, USA
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258
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Thorp E, Vaisar T, Subramanian M, Mautner L, Blobel C, Tabas I. Shedding of the Mer tyrosine kinase receptor is mediated by ADAM17 protein through a pathway involving reactive oxygen species, protein kinase Cδ, and p38 mitogen-activated protein kinase (MAPK). J Biol Chem 2011; 286:33335-44. [PMID: 21828049 DOI: 10.1074/jbc.m111.263020] [Citation(s) in RCA: 225] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mer tyrosine kinase (MerTK) is an integral membrane protein that is preferentially expressed by phagocytic cells, where it promotes efferocytosis and inhibits inflammatory signaling. Proteolytic cleavage of MerTK at an unidentified site leads to shedding of its soluble ectodomain (soluble MER; sMER), which can inhibit thrombosis in mice and efferocytosis in vitro. Herein, we show that MerTK is cleaved at proline 485 in murine macrophages. Site-directed deletion of 6 amino acids spanning proline 485 rendered MerTK resistant to proteolysis and suppression of efferocytosis by cleavage-inducing stimuli. LPS is a known inducer of MerTK cleavage, and the intracellular signaling pathways required for this action are unknown. LPS/TLR4-mediated generation of sMER required disintegrin and metalloproteinase ADAM17 and was independent of Myd88, instead requiring TRIF adaptor signaling. LPS-induced cleavage was suppressed by deficiency of NADPH oxidase 2 (Nox2) and PKCδ. The addition of the antioxidant N-acetyl cysteine inhibited PKCδ, and silencing of PKCδ inhibited MAPK p38, which was also required. In a mouse model of endotoxemia, we discovered that LPS induced plasma sMER, and this was suppressed by Adam17 deficiency. Thus, a TRIF-mediated pattern recognition receptor signaling cascade requires NADPH oxidase to activate PKCδ and then p38, culminating in ADAM17-mediated proteolysis of MerTK. These findings link innate pattern recognition receptor signaling to proteolytic inactivation of MerTK and generation of sMER and uncover targets to test how MerTK cleavage affects efferocytosis efficiency and inflammation resolution in vivo.
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Affiliation(s)
- Edward Thorp
- Departments of Medicine, Pathology and Cell Biology, and Physiology, and Cellular Biophysics, Columbia University, New York, New York 10032, USA.
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259
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Zhang W, Xu W, Xiong S. Macrophage differentiation and polarization via phosphatidylinositol 3-kinase/Akt-ERK signaling pathway conferred by serum amyloid P component. THE JOURNAL OF IMMUNOLOGY 2011; 187:1764-77. [PMID: 21753147 DOI: 10.4049/jimmunol.1002315] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Macrophage differentiation and polarization is influenced by, and act on, many processes associated with autoimmunity. However, the molecular mechanisms underlying macrophage polarization in systemic lupus erythematosus (SLE) remain largely debated. We previously demonstrated that macrophage M2b polarization conferred by activated lymphocyte-derived (ALD)-DNA immunization could initiate and propagate murine lupus nephritis. Serum amyloid P component (SAP), a conserved acute-phase protein in mice, has been reported to bind to DNA and modulate immune responses. In this study, murine SAP was shown to promote macrophage-mediated ALD-DNA uptake through binding to ALD-DNA (SAP/ALD-DNA). Moreover, macrophage phenotypic switch from a proinflammatory M2b phenotype induced by ALD-DNA alone to an anti-inflammatory M2a phenotype stimulated with SAP/ALD-DNA were found because of PI3K/Akt-ERK signaling activation. Both in vivo SAP supplements and adoptive transfer of ex vivo programmed M2a macrophages induced by SAP/ALD-DNA into SLE mice could efficiently alleviate lupus nephritis. Importantly, increased IL-10 secretion, accompanied by anti-inflammatory effect exerted by M2a macrophages, was found to predominantly impede macrophage M2b polarization. Furthermore, neutralization of IL-10 notably reduced the suppressive effect of M2a macrophages. Our results demonstrate that binding of SAP to ALD-DNA could switch macrophage phenotypic polarization from proinflammatory M2b to anti-inflammatory M2a via PI3K/Akt-ERK signaling activation, thus exerting protective and therapeutic interventions on murine lupus nephritis. These data provide a possible molecular mechanism responsible for modulation of macrophage polarization in the context of lupus nephritis and open a new potential therapeutic avenue for SLE.
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Affiliation(s)
- Weijuan Zhang
- Department of Immunology, Institute for Immunobiology, Shanghai Medical College, Fudan University, Shanghai 200032, People's Republic of China
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260
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Agrawal A, Gupta S. Impact of aging on dendritic cell functions in humans. Ageing Res Rev 2011; 10:336-45. [PMID: 20619360 DOI: 10.1016/j.arr.2010.06.004] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 06/18/2010] [Accepted: 06/21/2010] [Indexed: 12/12/2022]
Abstract
Aging is a paradox of reduced immunity and chronic inflammation. Dendritic cells are central orchestrators of the immune response with a key role in the generation of immunity and maintenance of tolerance. The functions of DCs are compromised with age. There is no major effect on the numbers and phenotype of DC subsets in aged subjects; nevertheless, their capacity to phagocytose antigens and migrate is impaired with age. There is aberrant cytokine secretion by various DC subsets with CDCs secreting increased basal level of pro-inflammatory cytokines but the response on stimulation to foreign antigens is decreased. In contrast, the response to self-antigens is increased suggesting erosion of peripheral self tolerance. PDC subset also secretes reduced IFN-α in response to viruses. The capacity of DCs to prime T cell responses is also affected. Aging thus has a profound affect on DC functions. Present review summarizes the effect of advancing age on DC functions in humans in the context of both immunity and tolerance.
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Affiliation(s)
- Anshu Agrawal
- Division of Basic and Clinical Immunology, Med. Sci. I C-240A, University of California, Irvine 92697, CA, USA.
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261
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Toll-like receptor 7 (TLR7)-driven accumulation of a novel CD11c⁺ B-cell population is important for the development of autoimmunity. Blood 2011; 118:1305-15. [PMID: 21543762 DOI: 10.1182/blood-2011-01-331462] [Citation(s) in RCA: 534] [Impact Index Per Article: 41.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Females are more susceptible than males to many autoimmune diseases. The processes causing this phenomenon are incompletely understood. Here, we demonstrate that aged female mice acquire a previously uncharacterized population of B cells that we call age-associated B cells (ABCs) and that these cells express integrin α(X) chain (CD11c). This unexpected population also appears in young lupus-prone mice. On stimulation, CD11c(+) B cells, both from autoimmune-prone and healthy strains of mice, secrete autoantibodies, and depletion of these cells in vivo leads to reduction of autoreactive antibodies, suggesting that the cells might have a direct role in the development of autoimmunity. We have explored factors that contribute to appearance of ABCs and demonstrated that signaling through Toll-like receptor 7 is crucial for development of this B cell population. We were able to detect a similar population of B cells in the peripheral blood of some elderly women with autoimmune disease, suggesting that there may be parallels between the creation of ABC-like cells between mice and humans.
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262
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Antoni A, Patel VA, Fan H, Lee DJ, Graham LH, Rosch CL, Spiegel DS, Rauch J, Levine JS. Macrophages from lupus-prone MRL mice have a conditional signaling abnormality that leads to dysregulated expression of numerous genes. Immunogenetics 2011; 63:291-308. [PMID: 21229240 PMCID: PMC3439499 DOI: 10.1007/s00251-010-0507-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Accepted: 12/17/2010] [Indexed: 01/06/2023]
Abstract
Macrophages (mϕ) from pre-diseased mice of the major murine inbred models of spontaneous autoimmunity (AI), including multiple lupus-prone strains and the type I diabetes-prone NOD (non-obese diabetic) strain, have identical apoptotic target-dependent abnormalities. This characteristic feature of mϕ from AI-prone mice suggests that abnormal signaling events induced within mϕ following their interaction with apoptotic targets may predispose to AI. Such signaling abnormalities would affect predominantly the processing and presentation of self-antigen (i.e., derived from apoptotic targets), while sparing the processing and presentation of foreign antigen (i.e., derived from non-apoptotic sources). Here, we used DNA microarrays to test the hypothesis that mϕ from AI-prone mice (MRL/MpJ [MRL/+] or MRL/MpJ-Tnfrsf6 ( lpr ) [MRL/lpr]) differentially express multiple genes in comparison to non-AI mϕ (BALB/c), but do so in a largely apoptotic cell-dependent manner. Mϕ were stimulated with lipopolysaccharide, a potent innate stimulus, in the presence or absence of serum (an experimental surrogate for apoptotic targets). In accord with our hypothesis, the number of genes differentially expressed by MRL mϕ was significantly increased in the presence vs. the absence of serum, the apoptotic target surrogate (n = 401 vs. n = 201). Notably, for genes differentially expressed by MRL mϕ in the presence of serum, serum-free culture normalized their expression to a level statistically indistinguishable from that by non-AI mϕ. Comparisons of mϕ from AI-prone NOD and non-AI C57BL/6 mice corroborated these findings. Together, these data support the hypothesis that mϕ from MRL and other AI-prone mice are characterized by a conditional abnormality elicited by serum lipids or apoptotic targets.
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Affiliation(s)
- Angelika Antoni
- Department of Biology, Kutztown University of Pennsylvania, Kutztown, PA 19530, USA
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263
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Wu J, Ekman C, Jönsen A, Sturfelt G, Bengtsson AA, Gottsäter A, Lindblad B, Lindqvist E, Saxne T, Dahlbäck B. Increased plasma levels of the soluble Mer tyrosine kinase receptor in systemic lupus erythematosus relate to disease activity and nephritis. Arthritis Res Ther 2011; 13:R62. [PMID: 21496228 PMCID: PMC3132057 DOI: 10.1186/ar3316] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2010] [Revised: 03/15/2011] [Accepted: 04/15/2011] [Indexed: 12/19/2022] Open
Abstract
Introduction Mer and Tyro3 are receptor tyrosine kinases important for the phagocytosis of apoptotic cells. Together with Axl, they constitute the TAM receptor family. These receptors can be shed from the cell membrane and their soluble extracellular regions can be found in plasma. The objective of this study was to elucidate whether the plasma levels of soluble Mer (sMer) and Tyro3 (sTyro3) were increased in systemic lupus erythematosis (SLE), rheumatoid arthritis (RA), or critical limb ischemia (CLI). Methods ELISA kits were used to test plasma concentrations in controls and in patients with SLE, RA or CLI. Results Increased levels of, in particular, sMer and, to some extent, sTyro3, were found in patients with SLE or RA, but not in patients with CLI. Patients with SLE demonstrated the highest sMer levels and there was a strong correlation to higher SLE disease activity score (SLEDAI). In contrast, in patients with RA, the sMer levels did not correlate with the disease activity score (DAS). In SLE, sMer levels were particularly high in those with lupus nephritis, patients who also had decreased C1q levels and increased titers of anti-DNA antibodies. After therapy, the plasma concentrations of sMer decreased in parallel to the decrease in SLEDAI score. Conclusions The plasma concentrations of sMer and sTyro3 were significantly increased in patients with active SLE and RA, suggesting the TAM receptor shedding was affected by these autoimmune diseases. In particular, sMer was increased in SLE, the plasma levels of sMer reflecting disease activity.
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Affiliation(s)
- Jun Wu
- Department of Laboratory Medicine, Section of Clinical Chemistry, Lund University, Wallenberg Laboratory, Skåne University Hospital, Södra Förstadsgatan 101, Malmö, SE 205 02, Sweden
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264
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Marginal zone macrophages suppress innate and adaptive immunity to apoptotic cells in the spleen. Blood 2011; 117:5403-12. [PMID: 21444914 DOI: 10.1182/blood-2010-11-320028] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Marginal zone macrophages (MZMs) are a small subset of specialized splenic macrophages known to interact with apoptotic material entering the spleen from circulation. To evaluate whether MZMs regulate immunity to apoptotic material we depleted MZMs and assessed innate and adaptive immune responses to apoptotic cells administered systemically. MZM depletion altered the spatial localization of apoptotic cells, which accumulated in T-cell areas of the lymphoid follicles. MZM depletion also enhanced phagocytosis of apoptotic cells by red pulp (CD68(+)F4/80(+)) macrophages, which expressed increased CD86, MHCII, and CCR7. MZM depletion led to increased production of proinflammatory cytokines and enhanced lymphocyte responsiveness to apoptotic cell antigens. Furthermore, we found that MZM depletion accelerated autoimmune disease progression in mice genetically prone to systemic lupus erythematosus and caused significant mortality in wild-type mice repeatedly exposed to exogenous apoptotic thymocytes. These findings support the hypothesis that MZMs are central in the clearance of apoptotic cells to minimize the immunogenicity of autoantigens.
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265
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Venkatesh J, Yoshifuji H, Kawabata D, Chinnasamy P, Stanevsky A, Grimaldi CM, Cohen-Solal J, Diamond B. Antigen is required for maturation and activation of pathogenic anti-DNA antibodies and systemic inflammation. THE JOURNAL OF IMMUNOLOGY 2011; 186:5304-12. [PMID: 21444762 DOI: 10.4049/jimmunol.1000224] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Systemic lupus erythematosus is an autoimmune disease characterized by autoantibodies and systemic inflammation that results in part from dendritic cell activation by nucleic acid containing immune complexes. There are many mouse models of lupus, some spontaneous and some induced. We have been interested in an induced model in which estrogen is the trigger for development of a lupus-like serology. The R4A transgenic mouse expresses a transgene-encoded H chain of an anti-DNA Ab. This mouse maintains normal B cell tolerance with deletion of high-affinity DNA-reactive B cells and maturation to immunocompetence of B cells making nonglomerulotropic, low-affinity DNA-reactive Abs. When this mouse is given estradiol, normal tolerance mechanisms are altered; high-affinity DNA-reactive B cells mature to a marginal zone phenotype, and the mice are induced to make high titers of anti-DNA Abs. We now show that estradiol administration also leads to systemic inflammation with increased B cell-activating factor and IFN levels and induction of an IFN signature. DNA must be accessible to B cells for both the production of high-affinity anti-DNA Abs and the generation of the proinflammatory milieu. When DNase is delivered to the mice at the same time as estradiol, there is no evidence for an abrogation of tolerance, no increased B cell-activating factor and IFN, and no IFN signature. Thus, the presence of autoantigen is required for positive selection of autoreactive B cells and for the subsequent positive feedback loop that occurs secondary to dendritic cell activation by DNA-containing immune complexes.
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Affiliation(s)
- Jeganathan Venkatesh
- Center for Autoimmune and Musculoskeletal Disease, Feinstein Institute for Medical Research, Manhasset, NY 11030, USA
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266
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Sule S, Rosen A, Petri M, Akhter E, Andrade F. Abnormal production of pro- and anti-inflammatory cytokines by lupus monocytes in response to apoptotic cells. PLoS One 2011; 6:e17495. [PMID: 21423726 PMCID: PMC3056659 DOI: 10.1371/journal.pone.0017495] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Accepted: 02/07/2011] [Indexed: 11/27/2022] Open
Abstract
Monocytes are a key component of the innate immune system involved in the regulation of the adaptive immune response. Previous studies have focused on apoptotic cell clearance abnormalities in systemic lupus erythematosus (SLE) monocytes. However, whether SLE monocytes might express unique patterns of cytokine secretion in response to apoptotic cells is still unknown. Here, we used monocytes from healthy controls and SLE patients to evaluate the production of TNF-α and TGF-β in response to apoptotic cells. Upon recognition of apoptotic material, monocytes from healthy controls showed prominent TGF-β secretion (mean ± SD: 824.6±144.3 pg/ml) and minimal TNF-α production (mean ± SD: 32.6±2.1 pg/ml). In contrast, monocytes from SLE patients had prominent TNF-α production (mean ± SD: 302.2±337.5 pg/ml) and diminished TGF-β secretion (mean ± SD: 685.9±615.9 pg/ml), a difference that was statistically significant compared to normal monocytes (p≤10(-6) for TNF-α secretion, and p = 0.0031 for TGF-β, respectively). Interestingly, the unique cytokine response by SLE monocytes was independent of their phagocytic clearance efficiency, opsonizing autoantibodies and disease activity. We further showed that nucleic acids from apoptotic cells play important role in the induction of TNF-α by lupus monocytes. Together, these observations suggest that, in addition to potential clearance defects, monocytes from SLE patients have an abnormal balance in the secretion of anti- and pro-inflammatory cytokines in response to apoptotic cells. Since the abnormal cytokine response to apoptotic material in SLE is not related to disease activity and opsonizing autoantibodies, it is possible that this response might be an intrinsic property of lupus monocytes. The studies focus attention on toll-like receptors (TLRs) and their downstream pathways as mediators of this response.
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Affiliation(s)
- Sangeeta Sule
- Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Antony Rosen
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Michelle Petri
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Ehtisham Akhter
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Felipe Andrade
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
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267
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Receptor for advanced glycation end products binds to phosphatidylserine and assists in the clearance of apoptotic cells. EMBO Rep 2011; 12:358-64. [PMID: 21399623 DOI: 10.1038/embor.2011.28] [Citation(s) in RCA: 175] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 01/24/2011] [Accepted: 01/27/2011] [Indexed: 01/13/2023] Open
Abstract
Clearance of apoptotic cells is necessary for tissue development, homeostasis and resolution of inflammation. The uptake of apoptotic cells is initiated by an 'eat-me' signal, such as phosphatidylserine, on the cell surface and phagocytes recognize the signal by using specific receptors. In this study, we show that the soluble form of the receptor for advanced glycation end products (RAGE) binds to phosphatidylserine as well as to the apoptotic thymocytes. RAGE-deficient (Rage(-/-)) alveolar macrophages showed impaired phagocytosis of apoptotic thymocytes and defective clearance of apoptotic neutrophils in Rage(-/-) mice. Our results indicate that RAGE functions as a phosphatidylserine receptor and assists in the clearance of apoptotic cells.
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268
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Absence of scavenger receptor A promotes dendritic cell-mediated cross-presentation of cell-associated antigen and antitumor immune response. Immunol Cell Biol 2011; 90:101-8. [PMID: 21383767 PMCID: PMC3134534 DOI: 10.1038/icb.2011.10] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Given the primary expression of scavenger receptor A (SRA) or CD204 on antigen-presenting cells, we investigate the immunoregulatory activities of SRA/CD204 in the context of cross-presentation of cell-associated antigen and the immunogenicity of dying tumor cells. Immunization with dying prostate cancer cells results in profoundly increased control of subsequently inoculated tumors in SRA/CD204 knockout mice. Using OVA-expressing RM1 prostate tumor line (RM1-OVA), we show for the first time that SRA absence greatly enhances dendritic cells (DCs)-mediated cross-presentation of OVA antigen derived from dying RM1 cells. While the phagocytic ability of DCs is not significantly impacted by the lack of SRA/CD204, DCs deficient in SRA/CD204 display increased expression of inflammatory cytokines and chemokines, as well as co-stimulatory molecules upon interaction with dying RM1 cells, implicating a suppressive regulation of the functional activation of DCs by SRA/CD204. Further, SRA/CD204-deficient DCs pulsed with dying RM1-OVA cells are more effective than wild-type counterparts in priming antigen-specific T-cell responses, resulting in improved control of RM1 tumor growth in both prophylactic and therapeutic settings. Our findings suggest that the increased immunogenicity of dying tumor cells in SRA/CD204 knockout mice is attributed to the altered functions of DCs in the absence of SRA/CD204, which underscores the important role of SRA/CD204 in host immune homeostasis. Selective downregulation or blockade of this immunoregulatory molecule may lead to enhanced potency of DC-based vaccines capable of breaking immune tolerance against cancer.
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269
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Shao WH, Cohen PL. Disturbances of apoptotic cell clearance in systemic lupus erythematosus. Arthritis Res Ther 2011; 13:202. [PMID: 21371352 PMCID: PMC3157636 DOI: 10.1186/ar3206] [Citation(s) in RCA: 139] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Systemic lupus erythematosus is a multifactorial autoimmune disease with an as yet unknown etiopathogenesis. It is widely thought that self-immunization in systemic lupus is driven by defective clearance of dead and dying cells. In lupus patients, large numbers of apoptotic cells accumulate in various tissues including germinal centers. In the present review, we discuss the danger signals released by apoptotic cells, their triggering of inflammatory responses, and the breakdown of B-cell tolerance. We also review the pathogenic role of apoptotic cell clearance in systemic lupus erythematosus.
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Affiliation(s)
- Wen-Hai Shao
- Department of Medicine, Temple University, Philadelphia, PA 19140, USA
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270
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Ma GZM, Stankovich J, Kilpatrick TJ, Binder MD, Field J. Polymorphisms in the receptor tyrosine kinase MERTK gene are associated with multiple sclerosis susceptibility. PLoS One 2011; 6:e16964. [PMID: 21347448 PMCID: PMC3035668 DOI: 10.1371/journal.pone.0016964] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Accepted: 01/10/2011] [Indexed: 11/18/2022] Open
Abstract
Multiple sclerosis (MS) is a debilitating, chronic demyelinating disease of the central nervous system affecting over 2 million people worldwide. The TAM family of receptor tyrosine kinases (TYRO3, AXL and MERTK) have been implicated as important players during demyelination in both animal models of MS and in the human disease. We therefore conducted an association study to identify single nucleotide polymorphisms (SNPs) within genes encoding the TAM receptors and their ligands associated with MS. Analysis of genotype data from a genome-wide association study which consisted of 1618 MS cases and 3413 healthy controls conducted by the Australia and New Zealand Multiple Sclerosis Genetics Consortium (ANZgene) revealed several SNPs within the MERTK gene (Chromosome 2q14.1, Accession Number NG_011607.1) that showed suggestive association with MS. We therefore interrogated 28 SNPs in MERTK in an independent replication cohort of 1140 MS cases and 1140 healthy controls. We found 12 SNPs that replicated, with 7 SNPs showing p-values of less than 10−5 when the discovery and replication cohorts were combined. All 12 replicated SNPs were in strong linkage disequilibrium with each other. In combination, these data suggest the MERTK gene is a novel risk gene for MS susceptibility.
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Affiliation(s)
- Gerry Z. M. Ma
- Multiple Sclerosis Division, Florey Neuroscience Institutes, University of Melbourne, Melbourne, Victoria, Australia
- Centre for Neuroscience, University of Melbourne, Melbourne, Victoria, Australia
| | - Jim Stankovich
- Menzies Research Institute, University of Tasmania, Hobart, Tasmania, Australia
| | | | - Trevor J. Kilpatrick
- Multiple Sclerosis Division, Florey Neuroscience Institutes, University of Melbourne, Melbourne, Victoria, Australia
- Centre for Neuroscience, University of Melbourne, Melbourne, Victoria, Australia
| | - Michele D. Binder
- Multiple Sclerosis Division, Florey Neuroscience Institutes, University of Melbourne, Melbourne, Victoria, Australia
- Centre for Neuroscience, University of Melbourne, Melbourne, Victoria, Australia
| | - Judith Field
- Multiple Sclerosis Division, Florey Neuroscience Institutes, University of Melbourne, Melbourne, Victoria, Australia
- Centre for Neuroscience, University of Melbourne, Melbourne, Victoria, Australia
- * E-mail:
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271
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Sandahl M, Hunter DM, Strunk KE, Earp HS, Cook RS. Epithelial cell-directed efferocytosis in the post-partum mammary gland is necessary for tissue homeostasis and future lactation. BMC DEVELOPMENTAL BIOLOGY 2010; 10:122. [PMID: 21192804 PMCID: PMC3022573 DOI: 10.1186/1471-213x-10-122] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 12/30/2010] [Indexed: 11/17/2022]
Abstract
Background Mammary glands harbor a profound burden of apoptotic cells (ACs) during post-lactational involution, but little is known regarding mechanisms by which ACs are cleared from the mammary gland, or consequences if this process is interrupted. We investigated AC clearance, also termed efferocytosis, during post-lactational remodeling, using mice deficient for MerTK, Axl, and Tyro3, three related receptor tyrosine kinases (RTKs) regulating macrophage-mediated efferocytosis in monocytes. MerTK expression, apoptosis and the accumulation of apoptotic debris were examined in histological sections of MerTK-deficient, Axl/Tyro3-deficient, and wild-type mammary glands harvested at specific time points during lactation and synchronized involution. The ability of primary mammary epithelial cells (MECs) to engulf ACs was assessed in culture. Transplant of MerTK-deficient mammary epithelium into cleared WT mammary fat pads was used to assess the contribution of WT mammary macrophages to post-lactational efferocytosis. Results ACs induced MerTK expression in MECs, resulting in elevated MerTK levels at the earliest stages of involution. Loss of MerTK resulted in AC accumulation in post-lactational MerTK-deficient mammary glands, but not in Axl and Tyro3-deficient mammary glands. Increased vascularization, fibrosis, and epithelial hyperproliferation were observed in MerTK-deficient mammary glands through at least 60 days post-weaning, due to failed efferocytosis after lactation, but did not manifest in nulliparous mice. WT host-derived macrophages failed to rescue efferocytosis in transplanted MerTK-deficient mammary epithelium. Conclusion Efferocytosis by MECs through MerTK is crucial for mammary gland homeostasis and function during the post-lactational period. Efferocytosis by MECs thus limits pathologic consequences associated with the apoptotic load following lactation.
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Affiliation(s)
- Melissa Sandahl
- UNC-Lineberger Comprehensive Cancer Center, 450 West Ave, Chapel Hill, North Carolina 27599, USA
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272
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A-González N, Castrillo A. Liver X receptors as regulators of macrophage inflammatory and metabolic pathways. Biochim Biophys Acta Mol Basis Dis 2010; 1812:982-94. [PMID: 21193033 DOI: 10.1016/j.bbadis.2010.12.015] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Revised: 12/14/2010] [Accepted: 12/17/2010] [Indexed: 12/30/2022]
Abstract
The liver X receptors (LXRα and LXRβ) are members of the nuclear receptor family of transcription factors that play essential roles in the transcriptional control of lipid metabolism. LXRs are endogenously activated by modified forms of cholesterol known as oxysterols and control the expression of genes important for cholesterol uptake, efflux, transport, and excretion in multiple tissues. In addition to their role as cholesterol sensors, a number of studies have implicated LXRs in the modulation of innate and adaptive immune responses. Both through activation and repression mechanisms, LXRs regulate diverse aspects of inflammatory gene expression in macrophages. The ability of LXRs to coordinate metabolic and immune responses constitutes an attractive therapeutic target for the treatment of chronic inflammatory disorders. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.
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Affiliation(s)
- Noelia A-González
- Department of Biochemistry and Molecular Biology, Universidad de Las Palmas de Gran Canaria, ULPGC, Las Palmas, Spain
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273
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Abstract
One of the ultimate goals in transplantation is to develop novel therapeutic methods for induction of donor-specific tolerance to reduce the side effects caused by the generalized immunosuppression associated to the currently used pharmacologic regimens. Interaction or phagocytosis of cells in early apoptosis exerts potent anti-inflammatory and immunosuppressive effects on antigen (Ag)-presenting cells (APC) like dendritic cells (DC) and macrophages. This observation led to the idea that apoptotic cell-based therapies could be employed to deliver donor-Ag in combination with regulatory signals to recipient’s APC as therapeutic approach to restrain the anti-donor response. This review describes the multiple mechanisms by which apoptotic cells down-modulate the immuno-stimulatory and pro-inflammatory functions of DC and macrophages, and the role of the interaction between apoptotic cells and APC in self-tolerance and in apoptotic cell-based therapies to prevent/treat allograft rejection and graft-versus-host disease in murine experimental systems and in humans. It also explores the role that in vivo-generated apoptotic cells could have in the beneficial effects of extracorporeal photopheresis, donor-specific transfusion, and tolerogenic DC-based therapies in transplantation.
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274
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Kinchen JM. A model to die for: signaling to apoptotic cell removal in worm, fly and mouse. Apoptosis 2010; 15:998-1006. [PMID: 20461556 DOI: 10.1007/s10495-010-0509-5] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Programmed cell death is used during developmental morphogenesis to eliminate superfluous cells or cells with inappropriate developmental potential (e.g., self-reactive immune cells, tumorigenic cells). Recent work in genetic models has led to a number of key observations, revealing signal transduction pathways and identifying new roles for genes previously studied in corpse removal (e.g., removal of broken synapses in the nervous system). Further, studies using mouse models have suggested a role for removal of apoptotic cells in the establishment or maintenance of immune tolerance. In this review, we survey current knowledge of phagocytic pathways derived from studies in the nematode (Caenorhabditis elegans), the fly (Drosophila melanogaster), and mouse (Mus musculus) model systems.
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Affiliation(s)
- Jason M Kinchen
- Department of Microbiology, Center for Cell Clearance, University of Virginia, Charlottesville, 22908, USA.
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275
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Ewald SE, Barton GM. Nucleic acid sensing Toll-like receptors in autoimmunity. Curr Opin Immunol 2010; 23:3-9. [PMID: 21146971 DOI: 10.1016/j.coi.2010.11.006] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2010] [Revised: 11/15/2010] [Accepted: 11/17/2010] [Indexed: 01/19/2023]
Abstract
Trafficking and activation of the nucleic acid sensing TLRs is subject to unique regulatory requirements imposed by the risk of self-recognition. Like all TLRs these receptors traffick through the Golgi, however, access to the secretory pathway is controlled by a binding partner present in the ER. Receptor activation in the endolysosome is regulated through a proteolytic mechanism that requires activity of compartment-resident proteases, thereby preventing activation in other regions of the cell. Advances in our understanding of the cell biology of these receptors have been paralleled by efforts to understand their precise roles in autoimmunity. Mouse models have revealed that TLR7 and TLR9 make unique contributions to the types of self-molecules recognized in disease and possibly disease severity. Currently, methods of inhibiting TLR7 and TLR9 are being tested in clinical trials for systemic lupus erythamatosus.
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Affiliation(s)
- Sarah E Ewald
- Division of Immunology and Pathogenesis, Department of Molecular and Cell Biology, University of California, Berkeley, 405 Life Sciences Addition, Berkeley, CA 94720-3200, USA.
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276
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Sadallah S, Eken C, Schifferli JA. Ectosomes as immunomodulators. Semin Immunopathol 2010; 33:487-95. [PMID: 21136061 DOI: 10.1007/s00281-010-0232-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2010] [Accepted: 11/23/2010] [Indexed: 01/07/2023]
Abstract
Considerable progress has been made in recognizing microvesicles as important mediators of intercellular communication rather than irrelevant cell debris. Microvesicles released by budding directly from the cell membrane surface (i.e., ectocytosis) either spontaneously or in response to various stimuli are called shed vesicles or ectosomes. Ectosomes are rightside-out vesicles with cytosolic content, and they expose phosphatidylserine in the outer leaflet of their membrane. Depending on their cellular origin, ectosomes have been associated with a broad spectrum of biological activities. In the light of recent findings, we now know that ectosomes derived from polymorphonuclear leukocytes, erythrocytes, platelets, and tumor cells have profound effects on the innate immune system, as well as on the induction of the adaptive immunity, globally reprogramming cells such as macrophages or dendritic cells toward an immunosuppressive and possibly tolerogenic phenotype. Although the effects observed in the circulation are mainly procoagulant and pro-inflammatory, ectosomes might be anti-inflammatory/immunosuppressive in local inflammation.
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Affiliation(s)
- Salima Sadallah
- Immunonephrology Laboratory, Department of Biomedicine, University Hospital Basel, Basel, Switzerland
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277
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Roszer T, Menéndez-Gutiérrez MP, Lefterova MI, Alameda D, Núñez V, Lazar MA, Fischer T, Ricote M. Autoimmune kidney disease and impaired engulfment of apoptotic cells in mice with macrophage peroxisome proliferator-activated receptor gamma or retinoid X receptor alpha deficiency. THE JOURNAL OF IMMUNOLOGY 2010; 186:621-31. [PMID: 21135166 DOI: 10.4049/jimmunol.1002230] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Autoimmune glomerulonephritis is a common manifestation of systemic lupus erythematosus (SLE). In this study, we show that mice lacking macrophage expression of the heterodimeric nuclear receptors PPARγ or RXRα develop glomerulonephritis and autoantibodies to nuclear Ags, resembling the nephritis seen in SLE. These mice show deficiencies in phagocytosis and clearance of apoptotic cells, and they are unable to acquire an anti-inflammatory phenotype upon feeding of apoptotic cells, which is critical for the maintenance of self-tolerance. These results demonstrate that stimulation of PPARγ and RXRα in macrophages facilitates apoptotic cell engulfment, and they provide a potential strategy to avoid autoimmunity against dying cells and to attenuate SLE.
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Affiliation(s)
- Tamás Roszer
- Departamento de Cardiología Regenerativa, Centro Nacional de Investigaciones Cardiovasculares, 28029 Madrid, Spain
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278
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Pisetsky DS. The role of HMGB1 in efferocytosis: when the dead go unburied. Focus on “HMGB1 inhibits macrophage activity in efferocytosis through binding to the αvβ3-integrin”. Am J Physiol Cell Physiol 2010; 299:C1253-5. [DOI: 10.1152/ajpcell.00397.2010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- David S. Pisetsky
- Division of Rheumatology and Immunology, Department of Medicine, Duke University Medical Center, Durham Veterans Administration Medical Center, Durham, North Carolina
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279
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Abstract
The Tyro3, Axl, and Mer (TAM) receptor tyrosine kinases and their ligands Gas6 and Protein S are required for the optimal phagocytosis of apoptotic cells in the mature immune, nervous, and reproductive systems. Genetic analyses in mice, rats, and humans reveal that this receptor-ligand system plays an especially important role in the phagocytosis that is triggered by the "eat-me" signal phosphatidylserine. Deficiencies in TAM signaling lead to human retinal dystrophies and may contribute to lupus and other human autoimmune diseases. The TAM system appears to interact and cooperate with several other phagocytic networks, including scavenger receptor and integrin-based systems, and may serve as a signaling hub that integrates these systems.
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Affiliation(s)
- Greg Lemke
- The Salk Institute, La Jolla, California 92037, USA.
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280
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Silverman GJ. Rethinking the red wolf disease: does Protein S suppress systemic lupus erythematosus clinical activity? Arthritis Res Ther 2010; 12:144. [PMID: 21067626 PMCID: PMC2991027 DOI: 10.1186/ar3162] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In systemic lupus erythematosus, the forces responsible for disease initiation and self-perpetuation in these clinically heterogeneous populations remain poorly understood. Recent studies of the TAM (Tyro3, Axl and MerTK) family of receptor tyrosine kinases may lead to a better understanding of the fundamental control system responsible for the clearance of apoptotic cells and the regulation of inflammation. In a recent report, serum levels of the TAM ligand, Protein S, was found to correlate with certain disease manifestations and with C3 and C4 levels. Protein S levels could provide a quantitative clinical biomarker but it remains to be determined whether this factor directly affects disease activity.
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281
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Silva MT. Secondary necrosis: the natural outcome of the complete apoptotic program. FEBS Lett 2010; 584:4491-9. [PMID: 20974143 DOI: 10.1016/j.febslet.2010.10.046] [Citation(s) in RCA: 288] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2010] [Revised: 10/17/2010] [Accepted: 10/19/2010] [Indexed: 12/31/2022]
Abstract
The predominant definition of apoptosis considers that the elimination of the apoptosing cell is by heterolytic degradation following phagocytosis by an assisting scavenger (efferocytosis). However, an alternative and largely underestimated outcome of apoptosis is secondary necrosis, an autolytic process of cell disintegration with release of cell components that occurs when there is no intervention of scavengers and the full apoptotic program is completed. Secondary necrosis is the typical outcome of apoptosis in unicellular eukaryotes but, importantly, it may also occur in multicellular animals and has been implicated in the genesis of important human pathologies. Secondary necrosis is a mode of cell elimination with specific molecular and morphological features and should be considered the natural outcome of the complete apoptotic program.
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Affiliation(s)
- Manuel T Silva
- Instituto de Biologia Molecular e Celular, University of Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
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282
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Rothlin CV, Lemke G. TAM receptor signaling and autoimmune disease. Curr Opin Immunol 2010; 22:740-6. [PMID: 21030229 DOI: 10.1016/j.coi.2010.10.001] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2010] [Revised: 09/09/2010] [Accepted: 10/01/2010] [Indexed: 11/26/2022]
Abstract
The TAM receptor tyrosine kinases Tyro3, Axl, and Mer and their ligands Gas6 and Protein S are essential for the phagocytosis of apoptotic cells and membranes in the adult immune, nervous, and reproductive systems. Genetic studies indicate that this receptor-ligand system is central to apoptotic cell engulfment that is triggered by the 'eat-me' signal phosphatidylserine (PtdSer). At the same time, TAM signaling is normally activated by Toll-like receptor (TLR) and type I interferon signaling, as part of the innate inflammatory response in dendritic cells (DCs) and macrophages, where it inhibits this response. Deficiencies in TAM signaling result in human retinal dystrophies and may contribute to lupus and other human autoimmune diseases.
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Affiliation(s)
- Carla V Rothlin
- Department of Immunobiology, Yale University School of Medicine, New Haven, CT 06520, United States.
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283
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Gregory CD, Pound JD. Cell death in the neighbourhood: direct microenvironmental effects of apoptosis in normal and neoplastic tissues. J Pathol 2010; 223:177-94. [PMID: 21125674 DOI: 10.1002/path.2792] [Citation(s) in RCA: 149] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Revised: 09/12/2010] [Accepted: 09/21/2010] [Indexed: 12/24/2022]
Abstract
Here we consider the impact of the physiological cell-death programme on normal tissue homeostasis and on disease pathogenesis, with particular reference to evolution and progression of neoplasia. We seek to describe the direct contributions played by apoptosis in creating the microenvironments of normal and malignant tissues and to discuss the molecular mechanisms underlying the elements of the '3Rs' that define the meaning of apoptosis: recognition, response, and removal. Apoptotic cells elicit responses in other cell types-both phagocytic and non-phagocytic-through short- and long-range signalling modes that range from direct contact to intercellular communication via membrane-bound microparticles. Such cellular responses include migration, proliferation, and differentiation, as well as production of immunomodulatory and anti-inflammatory mediators together with, in the case of phagocytes, engulfment, and breakdown of apoptotic cells. In normal tissues, the removal of apoptotic cells is rapid and typically non-phlogistic. We discuss the importance of this clearance process in tissue homeostasis and the consequences of its failure in disease pathogenesis. Using the typical cell culture environment in vitro as an illustrative example in which apoptosis occurs commonly in the absence of the removal mechanisms, we also discuss the inhibitory effects of persistent apoptotic cells on their otherwise viable neighbours. Since apoptosis is a common and sustained event in high-grade malignancies, we hypothesize on its purposeful role in conditioning the tumour microenvironment. We propose that apoptosis subserves several pro-tumour functions-trophic, anti-inflammatory, and immunomodulatory-and we identify strategies targeting host responses to apoptotic cells as promising modes of future therapies that could be applied to multiple cancer types in which tumour-cell apoptosis is active.
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Affiliation(s)
- Christopher D Gregory
- MRC Centre for Inflammation Research, University of Edinburgh, Queens Medical Research Institute, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK.
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284
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Eken C, Martin PJ, Sadallah S, Treves S, Schaller M, Schifferli JA. Ectosomes released by polymorphonuclear neutrophils induce a MerTK-dependent anti-inflammatory pathway in macrophages. J Biol Chem 2010; 285:39914-21. [PMID: 20959443 DOI: 10.1074/jbc.m110.126748] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
At the earliest stage of activation, human polymorphonuclear neutrophils release vesicles derived directly from the cell surface. These vesicles, called ectosomes (PMN-Ect), expose phosphatidylserine in the outer membrane leaflet. They inhibit the inflammatory response of human monocyte-derived macrophages and dendritic cells to zymosan A (ZymA) and LPS and induce TGF-β1 release, suggesting a reprogramming toward a tolerogenic phenotype. The receptors and signaling pathways involved have not yet been defined. Here, we demonstrate that PMN-Ect interfered with ZymA activation of macrophages via inhibition of NFκB p65 phosphorylation and NFκB translocation. The MerTK (Mer receptor tyrosine kinase) and PI3K/Akt pathways played a key role in this immunomodulatory effect as shown using specific MerTK-blocking antibodies and PI3K inhibitors LY294002 and wortmannin. As a result, PMN-Ect reduced the transcription of many proinflammatory genes in ZymA-activated macrophages. In sum, PMN-Ect interacted with the macrophages by activation of the MerTK pathway responsible for down-modulation of the proinflammatory signals generated by ZymA.
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Affiliation(s)
- Ceylan Eken
- Basel University Hospital, 4031 Basel, Switzerland.
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285
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Rahman ZSM, Shao WH, Khan TN, Zhen Y, Cohen PL. Impaired apoptotic cell clearance in the germinal center by Mer-deficient tingible body macrophages leads to enhanced antibody-forming cell and germinal center responses. THE JOURNAL OF IMMUNOLOGY 2010; 185:5859-68. [PMID: 20952679 DOI: 10.4049/jimmunol.1001187] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Germinal centers (GCs) are specialized microenvironments that generate high-affinity Ab-forming cells (AFCs) and memory B cells. Many B cells undergo apoptosis during B cell clonal selection in GCs. Although the factors that regulate the AFC and GC responses are not precisely understood, it is widely believed that dysregulated AFCs and GCs contribute to autoimmunity. The Mer receptor tyrosine kinase (Mer) facilitates macrophage clearance of apoptotic cells. The Tyro-3, Axl, and Mer receptors, including Mer, suppress TLRs and cytokine-mediated inflammatory responses. We report in this study that tingible body macrophages (TBMφs) in GCs express Mer. Compared to C57BL/6 (B6) controls, Mer-deficient (Mer(-/-)) mice had significantly higher AFC, GC, and Th1-skewed IgG2 Ab (especially IgG2c) responses against the T cell-dependent Ag (4-hydroxy-3-nitrophenyl) acetyl-chicken γ globulin. Mer(-/-) mice had a significantly higher percentage of GC B cells on days 9, 14, and 21 postimmunization compared with B6 controls. Significantly increased numbers of apoptotic cells accumulated in Mer(-/-) GCs than in B6 GCs, whereas the number of TBMφs remained similar in both strains. Our data are the first, to our knowledge, to demonstrate a critical role for Mer in GC apoptotic cell clearance by TBMφs and have interesting implications for Mer in the regulation of B cell tolerance operative in the AFC and GC pathways.
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Affiliation(s)
- Ziaur S M Rahman
- Department of Microbiology and Immunology, Thomas Jefferson University, Philadelphia, PA 19107-5541, USA.
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286
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Nguyen CQ, Peck AB. Inflammation in dry eye diseases culminating in loss of ocular homeostasis. EXPERT REVIEW OF OPHTHALMOLOGY 2010. [DOI: 10.1586/eop.10.51] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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287
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Shao WH, Kuan AP, Wang C, Abraham V, Waldman MA, Vogelgesang A, Wittenburg G, Choudhury A, Tsao PY, Miwa T, Eisenberg RA, Cohen PL. Disrupted Mer receptor tyrosine kinase expression leads to enhanced MZ B-cell responses. J Autoimmun 2010; 35:368-74. [PMID: 20822883 DOI: 10.1016/j.jaut.2010.08.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 08/07/2010] [Accepted: 08/09/2010] [Indexed: 11/19/2022]
Abstract
Control of lymphocyte homeostasis is essential to ensure efficient immune responses and to prevent autoimmunity. Splenic marginal zone B cells are important producers of autoantibodies, and are subject to stringent tolerance mechanisms to prevent autoimmunity. In this paper, we explore the role of the Mer tyrosine kinase (Mertk) in regulating autoreactive B cells. This receptor tyrosine kinase serves to bind apoptotic cells, to mediate their phagocytosis, and to regulate subsequent cytokine production. Mice lacking Mertk suffer from impaired apoptotic cell clearance and develop a lupus-like autoimmune syndrome. Here we show that such Mertk-KO mice have expanded numbers of splenic marginal zone B cells. Mertk-KO mice bearing a DNA-specific immunoglobulin heavy-chain transgene (3H9) produced anti-DNA antibodies that appeared to be secreted largely by marginal zone B cells. Finally, Mertk-KO mice developed greater antibody responses after NP-Ficoll immunization than their B6 counterparts. Taken together, our data show that Mertk has a major effect on the development of the marginal zone B-cell compartment. Mertk is also important in establishing DNA-specific B-cell tolerance in 3H9 anti-DNA transgenic mice.
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Affiliation(s)
- Wen-Hai Shao
- Section of Rheumatology, Department of Medicine, Temple University, USA
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288
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Taher TE, Parikh K, Flores-Borja F, Mletzko S, Isenberg DA, Peppelenbosch MP, Mageed RA. Protein phosphorylation and kinome profiling reveal altered regulation of multiple signaling pathways in B lymphocytes from patients with systemic lupus erythematosus. ACTA ACUST UNITED AC 2010; 62:2412-23. [PMID: 20506108 DOI: 10.1002/art.27505] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
OBJECTIVE The cause of B lymphocyte hyperactivity and autoantibody production in systemic lupus erythematosus (SLE) remains unclear. Previously, we identified abnormalities in the level and translocation of signaling molecules in B cells in SLE patients. The present study was undertaken to examine the extent of signaling abnormalities that relate to altered B cell responses in SLE. METHODS B lymphocytes from 88 SLE patients and 72 healthy controls were isolated from blood by negative selection. Protein tyrosine phosphorylation and cellular kinase levels were analyzed by Western blotting, flow cytometry, and a kinome array protocol. Changes in protein phosphorylation were determined in ex vivo B cells and following B cell receptor engagement. RESULTS Differences in tyrosine phosphorylation in B cells from patients with SLE, compared with matched controls, were demonstrated. Further, the kinome array analysis identified changes in the activation of key kinases, i.e., the activity of phosphatidylinositol 3-kinase, which regulates survival and differentiation, was up-regulated and the activity of Rac and Rho kinases, which regulate the cytoskeleton and migration, was increased. In contrast, the activity of ATR, which regulates the cell cycle, was down-regulated in SLE patients compared with controls. Differences in signaling pathways were seen in all SLE B lymphocyte subsets that manifested phenotypic features of immature, mature, and memory cells. CONCLUSION This study revealed dysregulation in multiple signaling pathways that control key responses in B cells of SLE patients. Data generated in this study provide a molecular basis for further analysis of the altered B lymphocyte responses in SLE.
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Affiliation(s)
- Taher E Taher
- Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
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289
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Elliott MR, Ravichandran KS. Clearance of apoptotic cells: implications in health and disease. ACTA ACUST UNITED AC 2010; 189:1059-70. [PMID: 20584912 PMCID: PMC2894449 DOI: 10.1083/jcb.201004096] [Citation(s) in RCA: 390] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Recent advances in defining the molecular signaling pathways that regulate the phagocytosis of apoptotic cells have improved our understanding of this complex and evolutionarily conserved process. Studies in mice and humans suggest that the prompt removal of dying cells is crucial for immune tolerance and tissue homeostasis. Failed or defective clearance has emerged as an important contributing factor to a range of disease processes. This review addresses how specific molecular alterations of engulfment pathways are linked to pathogenic states. A better understanding of the apoptotic cell clearance process in healthy and diseased states could offer new therapeutic strategies.
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Affiliation(s)
- Michael R Elliott
- Center for Cell Clearance and the Department of Microbiology, University of Virginia, Charlottesville, VA 22908, USA
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290
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Abstract
Systemic lupus erythematosus (SLE) persists as a chronic inflammatory autoimmune disease and is characterized by the production of autoantibodies and immune complexes that affect multiple organs. The underlying mechanism that triggers and sustains disease are complex and involve certain susceptibility genes and environmental factors. There have been several immune mediators linked to SLE including cytokines and chemokines that have been reviewed elsewhere [ 1-3 ]. A number of articles have reviewed the role of B cells and T cells in SLE [ 4-10 ]. Here, we focus on the role of dendritic cells (DC) and innate immune factors that may regulate autoreactive B cells.
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Affiliation(s)
- Heather M Seitz
- Johnson County Community College, Science Division, Overland Park, Kansas, USA
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291
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Scapini P, Hu Y, Chu CL, Migone TS, Defranco AL, Cassatella MA, Lowell CA. Myeloid cells, BAFF, and IFN-gamma establish an inflammatory loop that exacerbates autoimmunity in Lyn-deficient mice. ACTA ACUST UNITED AC 2010; 207:1757-73. [PMID: 20624892 PMCID: PMC2916124 DOI: 10.1084/jem.20100086] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Autoimmunity is traditionally attributed to altered lymphoid cell selection and/or tolerance, whereas the contribution of innate immune cells is less well understood. Autoimmunity is also associated with increased levels of B cell–activating factor of the TNF family (BAFF; also known as B lymphocyte stimulator), a cytokine that promotes survival of self-reactive B cell clones. We describe an important role for myeloid cells in autoimmune disease progression. Using Lyn-deficient mice, we show that overproduction of BAFF by hyperactive myeloid cells contributes to inflammation and autoimmunity in part by acting directly on T cells to induce the release of IFN-γ. Genetic deletion of IFN-γ or reduction of BAFF activity, achieved by either reducing myeloid cell hyperproduction or by treating with an anti-BAFF monoclonal antibody, reduced disease development in lyn−/− mice. The increased production of IFN-γ in lyn−/− mice feeds back on the myeloid cells to further stimulate BAFF release. Expression of BAFF receptor on T cells was required for their full activation and IFN-γ release. Overall, our data suggest that the reciprocal production of BAFF and IFN-γ establishes an inflammatory loop between myeloid cells and T cells that exacerbates autoimmunity in this model. Our findings uncover an important pathological role of BAFF in autoimmune disorders.
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Affiliation(s)
- Patrizia Scapini
- Department of Laboratory Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
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292
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Silva MT. Bacteria-induced phagocyte secondary necrosis as a pathogenicity mechanism. J Leukoc Biol 2010; 88:885-96. [PMID: 20566623 DOI: 10.1189/jlb.0410205] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Triggering of phagocyte apoptosis is a major virulence mechanism used by some successful bacterial pathogens. A central issue in the apoptotic death context is that fully developed apoptosis results in necrotic cell autolysis (secondary necrosis) with release of harmful cell components. In multicellular animals, this occurs when apoptosing cells are not removed by scavengers, mainly macrophages. Secondary necrotic lysis of neutrophils and macrophages may occur in infection when extensive phagocyte apoptosis is induced by bacterial cytotoxins and removal of apoptosing phagocytes is defective because the apoptotic process exceeds the available scavenging capacity or targets macrophages directly. Induction of phagocyte secondary necrosis is an important pathogenic mechanism, as it combines the pathogen evasion from phagocyte antimicrobial activities and the release of highly cytotoxic molecules, particularly of neutrophil origin, such as neutrophil elastase. This pathogenicity mechanism therefore promotes the unrestricted multiplication of the pathogen and contributes directly to the pathology of several necrotizing infections, where extensive apoptosis and necrosis of macrophages and neutrophils are present. Here, examples of necrotizing infectious diseases, where phagocyte secondary necrosis is implicated, are reviewed.
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Affiliation(s)
- Manuel T Silva
- Instituto de Biologia Molecular e Celular, University of Porto, Rua do Campo Alegre 823, Porto, Portugal.
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293
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Williams JC, Wagner NJ, Earp HS, Vilen BJ, Matsushima GK. Increased hematopoietic cells in the mertk-/- mouse peritoneal cavity: a result of augmented migration. THE JOURNAL OF IMMUNOLOGY 2010; 184:6637-48. [PMID: 20483720 DOI: 10.4049/jimmunol.0902784] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The peritoneal cavity is recognized as an important site for autoreactive B cells prior to their transit to other immune tissues; however, little is known of the genes that may regulate this process. Mice lacking the receptor tyrosine kinase, Mertk, display a lupus-like autoimmune phenotype with splenomegaly and high autoantibodies titers. In this study, we investigate whether Mertk regulates the composition of peritoneal cells that favor an autoimmune phenotype. We found an increase in the number of macrophages, dendritic cells (DCs), plasmacytoid DCs, T cells, and B cells in the peritoneal cavity of mertk-/- mice when compared with wild-type mice. This disparity in cell numbers was not due to changes in cell proliferation or cell death. In adoptive transfer experiments, we showed an increase in migration of labeled donor cells into the mertk-/- peritoneal cavity. In addition, bone marrow chimeric mice showed hematopoietic-derived factors were also critical for T cell migration. Consistent with this migration and the increase in the number of cells, we identified elevated expression of CXCL9, its receptor CXCR3, and IL-7R on peritoneal cells from mertk-/- mice. To corroborate the migratory function of CXCR3 on cells, the depletion of CXCR3 donor cells significantly reduced the number of adoptively transferred cells that entered into the peritoneum of mertk-/- mice. This control of peritoneal cells numbers correlated with autoantibody production and was exclusively attributed to Mertk because mice lacking other family members, Axl or Tyro 3, did not display dysregulation in peritoneal cell numbers or the autoimmune phenotype.
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Affiliation(s)
- Julie C Williams
- Curriculum in Oral Biology, Department of Microbiology and Immunology, University of North Carolina Neuroscience Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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294
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Shao WH, Zhen Y, Rosenbaum J, Eisenberg RA, McGaha TL, Birkenbach M, Cohen PL. A protective role of Mer receptor tyrosine kinase in nephrotoxic serum-induced nephritis. Clin Immunol 2010; 136:236-44. [PMID: 20444650 DOI: 10.1016/j.clim.2010.04.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 03/29/2010] [Accepted: 04/01/2010] [Indexed: 12/30/2022]
Abstract
The Mer receptor tyrosine kinase is strongly expressed in the glomerulus. We wondered if this molecule might modify immune-mediated glomerular disease through its functions as a receptor for apoptotic cells and immunoregulatory molecule. Mer-knockout (KO) mice showed decreased survival rate and greatly increased proteinuria and serum urea levels compared to wild type (WT) mice by day 3 after injection of NTS. Their glomeruli were hyperplastic and later became necrotic. In the glomerulus of WT mice, a significant increase of Mer expression was observed. Apoptotic bodies were evident in NTS-treated Mer-KO kidneys, but not in normal controls. NTS-treated Mer-KO mice had massive neutrophil infiltration and inflammatory cytokine expression. Mer thus has a critical role in attenuating renal inflammation, both as a receptor for apoptotic cells and as a molecule that downregulates inflammation.
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Affiliation(s)
- Wen-Hai Shao
- Department of Medicine, Temple University, Philadelphia, PA 19140, USA
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295
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Muñoz LE, Lauber K, Schiller M, Manfredi AA, Herrmann M. The role of defective clearance of apoptotic cells in systemic autoimmunity. Nat Rev Rheumatol 2010; 6:280-9. [DOI: 10.1038/nrrheum.2010.46] [Citation(s) in RCA: 472] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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296
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Cash JL, Christian AR, Greaves DR. Chemerin peptides promote phagocytosis in a ChemR23- and Syk-dependent manner. THE JOURNAL OF IMMUNOLOGY 2010; 184:5315-24. [PMID: 20363975 DOI: 10.4049/jimmunol.0903378] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Chemerin peptides represent a recently identified component of the endogenous anti-inflammatory network that act via the G protein-coupled receptor ChemR23. The role of the chemerin peptide/ChemR23 pathway in phagocytosis, the clearance of apoptotic cells (efferocytosis), and the resolution of inflammation is unknown. In this article, we report that low picomolar concentrations of the chemerin peptide chemerin15 (C15) enhance macrophage (MPhi) phagocytosis of microbial particles and apoptotic cells by up to 360% in vitro. These prophagocytic effects of C15 are significantly impaired in ChemR23(-/-) MPhis and are associated with increased actin polymerization and localization of F-actin to the phagocytic cup. Importantly, pharmacological inhibition of Syk activity completely abrogates the prophagocytic activities of C15 and associated changes in actin polymerization and phagocytic cup formation, suggesting that C15 promotes phagocytosis by facilitating phagocytic cup development in a Syk-dependent manner. During peritoneal inflammation, C15 administration (8 pg/mouse) enhances microbial particle clearance and apoptotic neutrophil ingestion by MPhis in wild-type but not ChemR23(-/-) mice, such that levels of apoptotic and necrotic cells at the inflammatory site are profoundly reduced. In contrast, neutralization of endogenous chemerin species during peritoneal inflammation significantly impairs MPhi ingestion of apoptotic neutrophils and zymosan. Our data identify a key role of the chemerin peptide/ChemR23 axis in the efficient clearance of foreign material, efferocytosis, and, hence, the resolution of inflammation. Manipulation of the chemerin peptide/ChemR23 axis may represent a novel therapeutic approach for the treatment of inflammatory pathologies, especially if failure to efficiently clear phagocytic targets has been implicated in their pathogenesis.
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Affiliation(s)
- Jenna L Cash
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
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297
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Cacciapaglia F, Spadaccio C, Gregorj C, Margiotta D, Coccia R, De Marco F, Chello M, Picardi A, Amoroso A, Afeltra A. Apoptosis and Autoimmunity Induced by Clodronate in Systemic Lupus Erythematosus Mononuclear Circulating Cells. Int J Immunopathol Pharmacol 2010; 23:535-42. [DOI: 10.1177/039463201002300215] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The aim of this study is to evaluate the effect of clodronate on apoptosis of human systemic lupus erythematosus circulating mononuclear cells and to analyze possible correlations with changes in autoantibody production in vitro. Lympho-monocytes from 20 SLE patients were isolated and incubated with or without addition of 1 μM clodronate for 72 hours. Apoptosis and release of genomic material was assessed by immunofluorescent detection of cleaved caspase-3 and by Cell-Death-Detection ELISAPLUS kit (Roche). Anti-Nucleosome IgG and anti-dsDNA IgM and IgG autoantibody levels were determined in supernatants by commercially available ELISA kits. Clodronate induced apoptosis in monocytes as confirmed by cleaved caspase-3 immunostaining and by quantification of cleaved nucleosome in the supernatants (treated 0.22±0.05 O.D. vs untreated 0.09±0.04 O.D.; P<0.001). This finding was coupled with a significant increasing in supernatants of IgG anti-Nucleosome (treated 6.5±1.1 vs untreated 5.5±0.6 IU/mL; p=0.001) and IgM (treated 3.0±1.3 vs 2.2±0.9 IU/mL; p=0.02) and IgG (treated 4.0±1.8 vs untreated 2.8±1.5 IU/mL; p=0.02) anti-dsDNA autoantibody levels. Our findings stressed the proapoptotic activity of clodronate, as well as its potential autoimmunity induction in SLE mononuclear circulating cells. Clinical studies could clarify the role of bisphosphonates on autoantibody production and worsening of disease activity.
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Affiliation(s)
| | - C. Spadaccio
- Department of Cardiovascular Sciences, University Campus Bio-Medico of Rome
| | - C. Gregorj
- Department of Haematology, University “Campus Bio-Medico” of Rome
| | | | - R. Coccia
- Department of Biochemical Sciences, Sapienza University, Rome
| | - F. De Marco
- Laboratory of Virology, Regina Elena Institute for Cancer Research, Rome
| | - M. Chello
- Department of Cardiovascular Sciences, University Campus Bio-Medico of Rome
| | | | - A. Amoroso
- Department of Clinical Medicine, Sapienza University, Rome, Italy
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298
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Cooper G, Gilbert K, Greidinger E, James J, Pfau J, Reinlib L, Richardson B, Rose N. Recent advances and opportunities in research on lupus: environmental influences and mechanisms of disease. CIENCIA & SAUDE COLETIVA 2010; 14:1865-76. [PMID: 19851599 DOI: 10.1590/s1413-81232009000500028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2007] [Accepted: 03/05/2008] [Indexed: 12/14/2022] Open
Abstract
We summarize research on mechanisms through which environmental agents may affect the pathogenesis of lupus, discuss three exposures that have been the focus of research in this area, and propose recommendations for new research initiatives. We examined studies pertaining to key mechanistic events and specific exposures. Apoptosis leading to increased production or decreased clearance of immunogenic intracellular self-antigens and defective apoptosis of autoreactive immune cells both have been implicated in the loss of self-tolerance. The adjuvant or bystander effect is also needed to produce a sustained autoimmune response. Activation of toll-like receptors is one mechanism through which these effects may occur. Abnormal DNA methylation may contribute to the pathogenesis of lupus. Each of the specific exposures has been shown, in humans or in mice, to act upon one or more of these pathogenic steps. Specific recommendations for the continued advancement of our understanding of environmental influences on lupus and other autoimmune diseases include the development and use of mouse models with varying degrees of penetrance and manifestations of disease, identification of molecular or physiologic targets of specific exposures, development and use of improved exposure assessment methodologies, and multisite collaborations designed to examine understudied environmental exposures in humans.
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Affiliation(s)
- Glinda Cooper
- National Center for Environmental Assessment, U.S. EnvironmentalProtection Agency, Washington, DC 20460 USA.
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299
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Schaller M, Bigler C, Danner D, Ditzel HJ, Trendelenburg M. Autoantibodies against C1q in systemic lupus erythematosus are antigen-driven. THE JOURNAL OF IMMUNOLOGY 2010; 183:8225-31. [PMID: 20007586 DOI: 10.4049/jimmunol.0902642] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Autoantibodies against complement C1q (anti-C1q Abs) were shown to strongly correlate with the occurrence of severe nephritis in patients with systemic lupus erythematosus (SLE), suggesting a potential pathogenic role by interfering with the complement cascade. To analyze the humoral immune response against C1q at the molecular level, we screened a bone marrow-derived IgGkappa/IgGlambda Fab phage display library from a SLE patient with high anti-C1q Ab titer against purified human C1q. Six Fabs that exhibited strong binding to C1q in ELISA were isolated. The anti-C1q Fabs recognized neoepitopes that were only exposed on bound C1q and not present on soluble C1q mapping to different regions of the collagen-like region of C1q. Analysis of the genes encoding the variable H and L chains of the IgG-derived anti-C1q Fab revealed that all the variable H and L chain regions were highly mutated, with nucleotide and amino acid homologies to the closest germline in the range of 71-97% (average 85 +/- 4) and 72-92% (average 88 +/- 6), respectively. In addition, the variable region of the Fabs exhibited high replacement to silent ratios. The six anti-C1q Fabs were shown to be of high affinity, with a K(d) ranging from of 8.4 x 10(-8) M to 1.4 x 10(-7) M, comparable to an antiviral immune response. Our data underlines the notion that the development of anti-C1q Abs in SLE is the consequence of an Ag-driven, affinity-matured immune response. Those anti-C1q Fabs are unique tools to address how complement C1q is implicated in the pathogenesis of SLE.
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Affiliation(s)
- Monica Schaller
- Department Biomedicine, Laboratory of Clinical Immunology, University Hospital Basel, Basel, Switzerland.
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300
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Abstract
Autoimmunity has been a topic of intensive research for several decades, yet amazingly, no uniform hypothesis exists to explain the basis for the spectrum of autoantibody specificities seen in autoimmune diseases. It therefore seems appropriate to consider whether our current framework for understanding tolerance, and thus the mechanisms controlling the initiation and perpetuation of autoimmunity, may be faulty. Adapting the paradigm of Matzinger-the 'danger model', a case can be made for a perspective that appreciates the fundamental role of the tissues in controlling immune response, favouring a shift of focus in studies on the initiation of autoimmunity. Applying the elements of this model, I set forth a number of scenarios for how autoreactivity could emerge, with emphasis on the likely sources of the involved autoantigens and the functional basis of their appearance. The emerging picture is one in which disruption of tissue homeostasis takes centre stage, with the antigen-presenting cells as the key players.
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Affiliation(s)
- Anders A Tveita
- Department of Biochemistry, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway.
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