| 1. |
- Foltyn Zadura, Anna, et al.
(author)
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Factor H Autoantibodies in Patients with Antiphospholipid Syndrome and Thrombosis.
- 2015
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In: Journal of Rheumatology. - : The Journal of Rheumatology. - 0315-162X .- 1499-2752. ; 42:10, s. 1786-1793
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Journal article (peer-reviewed)abstract
- Autoantibodies to complement factor H (FH) are associated with atypical hemolytic uremic syndrome, but can also be detected in patients with rheumatoid arthritis and in patients positive for lupus anticoagulants and thus potentially antiphospholipid syndrome (APS). To our knowledge, no data are available on the association between the presence of FH autoantibodies in APS and clinical manifestations.
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| 2. |
- Leffler, Jonatan, et al.
(author)
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A subset of patients with systemic lupus erythematosus fails to degrade DNA from multiple clinically relevant sources.
- 2015
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In: Arthritis Research and Therapy. - : Springer Science and Business Media LLC. - 1478-6362 .- 1478-6354. ; 17
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Journal article (peer-reviewed)abstract
- Patients with systemic lupus erythematosus (SLE) have a decreased ability to clear cell remnants and multiple deficiencies in the ability to degrade cellular chromatin have been linked to the disease. Since the discovery of neutrophil extracellular traps (NETs), a renewed interest has been sparked in this field of research with multiple studies reporting a decreased ability of patients with SLE to degrade NETs. In this study we extend these findings by investigating the ability of patients with SLE to degrade chromatin from multiple clinically relevant sources.
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| 3. |
- Leffler, Jonatan, et al.
(author)
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Annexin-II, DNA and histones serve as Factor H ligands on the surface of apoptotic cells.
- 2010
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In: Journal of Biological Chemistry. - 1083-351X. ; 285:6, s. 3766-3776
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Journal article (peer-reviewed)abstract
- Apoptotic cells are opsonized by complement components such as C1q and C3b, which increases their susceptibility to phagocytosis. Soluble complement inhibitors such as factor H (fH)b also recognise apoptotic cells to minimize the pro-inflammatory effects of downstream complement activation. We used four radiolabelled protein constructs that span different regions of the 20 CCP modules that make up fH, and found that fragments comprising CCPs 6-8, CCPs 8-15 and CCPs 19-20 but not CCPs 1-4, bound to apoptotic Jurkat T-cells. There are four possible ligand types on apoptotic cells that could recruit fH: proteins, carbohydrates, lipids and DNA. We found that CCPs 6-8 of fH bind to annexin-II, a trypsin-insensitive protein that becomes exposed on surfaces of apoptotic cells. The second ligand of fH, which interacts with CCPs 6-8 and 19-20, is DNA. Confocal microscopy showed co-localisation of fH with antibodies specific for DNA. FH also binds to histones devoid of DNA and CCPs 1-4, 6-8 and 8-15 mediate this interaction. Treatment of apoptotic cells with neuraminidase, chondroitinase, heparitinase and heparinase did not change fH-binding. Treatment of apoptotic cells with phospholipase A2 dramatically increased both binding of fH and cell-surface DNA. We also excluded the possibility that fH interacts with lysophospholipids using surface plasmon resonance and flow cytometry with lipid-coated beads. Identification of annexin-II as one of the fH ligands on apoptotic cells together with the fact that autoantibodies against annexin-II are found in systemic lupus erythematosus provides further insight into understanding of the pathogenesis of this disease.
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| 4. |
- Leffler, Jonatan
(author)
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Complement in Autoimmunity - the importance of clearing waste
- 2013
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Doctoral thesis (other academic/artistic)abstract
- Systemic lupus erythematosus (SLE) is an autoimmune disease where improperly cleared apoptotic cells and neutrophil extracellular traps (NETs) induce an autoimmune response. Complement is crucial to prevent SLE by tailoring immune responses and opsonizing dead cells but may also induce inflammation and tissue damage once the disease is initiated. Complement C1q binds to apoptotic cells and ensures rapid and tolerogenic clearance by phagocytes. C1q can also activate complement. To avoid excessive activation, binding of the complement inhibitor factor H to the apoptotic cells is crucial. In this thesis we have discovered that factor H as well as C1q bind to the phospholipid binding proteins annexin A2 and that C1q also binds A5. These proteins are expressed on apoptotic cells. Further, we have observed that both C1q and factor H bind to the chromatin constituents, DNA and histones. Binding of C1q to these ligands led to complement activation indicating the need for factor H on the apoptotic cells. NETs constitute one mechanism of how neutrophils can protect the body from pathogens. By releasing chromatin covered with antimicrobial enzymes the neutrophil can catch and kill pathogens. In this thesis we confirm that NETs are not degraded properly in 30% of patients with SLE. Further, C1q binds to NETs, prevents degradation and also activates complement. Consequently, the patients with decreased ability to degrade NETs more often suffer from complement consumption and glomerulonephritis, manifestations of severe SLE. This initial study was followed-up by a longitudinal study where temporal associations such as glomerulonephritis, pleuritis and elevated levels of histone antibodies could then be linked to a decreased ability to degrade NETs. NET degradation was also affected in some patients with antiphospholipid syndrome and systemic sclerosis. However the effect was not as pronounced as in SLE and was more evident the more SLE-like the APS was. In conclusion, complement may both prevent and contribute to the pathogenesis in SLE. In this thesis, ligands for complement C1q and factor H have been revealed on the apoptotic cells and further, the interactions of complement with NETs have been elucidated. Additionally, the ability to degrade NETs has been analyzed in SLE and SLE like diseases, which may be used to better diagnose or treat these patients in the future.
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| 5. |
- Leffler, Jonatan, et al.
(author)
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Decreased Neutrophil Extracellular Trap Degradation in Shiga Toxin-Associated Haemolytic Uraemic Syndrome
- 2017
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In: Journal of Innate Immunity. - : S. Karger AG. - 1662-811X .- 1662-8128. ; 9:1, s. 12-21
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Journal article (peer-reviewed)abstract
- Background: Neutrophil extracellular traps (NETs) can stimulate thrombosis, and their degradation is decreased in several autoimmune disorders. It was recently reported that some patients with haemolytic uraemic syndrome (HUS) also fail to degrade NETs and that neutrophils from Shiga toxin-associated HUS are primed to form NETs. Method: We used a well-characterized cohort of 74 thrombotic microangiopathy (TMA) patients, with a subset also providing follow-up samples, and 112 age-matched controls to investigate NET degradation and serum nuclease activity in TMA before, during and after treatment. Results: We identified that in the cohort of TMA patients, 50% of patients with Shiga toxin-associated HUS displayed a decreased ability to degrade NETs. NET degradation correlated with serum nuclease activity, but not with autoantibodies against double-stranded DNA, which has been previously observed in some autoimmune disorders. Further, NET degradation negatively correlated with serum creatinine levels, suggesting that kidney function was negatively impacted by the low NET degradation ability. Conclusions: We revealed that decreased NET degradation is a common feature of Shiga toxin-associated HUS and that it is associated with decreased kidney function in these patients. It remains to be clarified whether improving NET degradation would be beneficial for the patient.
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| 6. |
- Leffler, Jonatan, et al.
(author)
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Degradation of neutrophil extracellular traps co-varies with disease activity in patients with systemic lupus erythematosus
- 2013
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In: Arthritis Research and Therapy. - : Springer Science and Business Media LLC. - 1478-6354. ; 15:4
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Journal article (peer-reviewed)abstract
- Introduction: The ability to degrade neutrophil extracellular traps (NETs) is reduced in a subset of patients with systemic lupus erythematosus (SLE). NETs consist of chromatin covered with antimicrobial enzymes and are normally degraded by DNase-I, an enzyme which is known to have reduced activity in SLE. Decreased ability to degrade NETs is associated with disease activity. In the current study we investigated how the ability of serum from SLE patients to degrade NETs varies during the course of SLE as well as what impact this may have for the clinical phenotype of SLE.Methods: Serum from 69 patients with SLE, included in a prospective study, was taken every 60 days for a median of 784 days. The ability of serum to degrade NETs was determined and associated with clinical parameters occurring before and at the time of sampling, as well as after sampling by using conditional logistic regression.Results: As many as 41% of all patients in the study showed decreased ability to degrade NETs at least once, but with a median of 20% of all time points. Decreased degradation was associated with manifestations of glomerulonephritis as well as low complement levels and elevated levels of antibodies directed against histones and DNA. Furthermore, the odds ratio for the patient to develop alopecia and fever after an episode of decreased NETs degradation was increased by four to five times compared to normal.Conclusions: Decreased degradation of NETs is associated with clinical manifestations in SLE and may contribute to disease pathogenesis. Potential therapeutics restoring the ability to degrade NETs could be beneficial for certain patients with SLE.
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| 7. |
- Leffler, Jonatan, et al.
(author)
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Degradation of neutrophil extracellular traps is decreased in patients with antiphospholipid syndrome.
- 2014
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In: Clinical and Experimental Rheumatology. - 1593-098X. ; 32:1, s. 66-70
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Journal article (peer-reviewed)abstract
- A decreased ability to degrade neutrophil extracellular traps (NETs) is seen in a subgroup of patients with systemic lupus erythematosus (SLE) and correlates with the presence of autoantibodies. Antiphospholipid syndrome (APS) can develop secondary to SLE or as a primary disease. In the current study we investigated the ability of sera from patients with APS to degrade NETs. The presence of antibodies against NETs and neutrophil remnants were also determined in the same patients.
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| 8. |
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| 9. |
- Leffler, Jonatan, et al.
(author)
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Neutrophil Extracellular Traps That Are Not Degraded in Systemic Lupus Erythematosus Activate Complement Exacerbating the Disease.
- 2012
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In: Journal of immunology. - : The American Association of Immunologists. - 1550-6606 .- 0022-1767. ; 188:7, s. 3522-3531
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Journal article (peer-reviewed)abstract
- Ongoing inflammation including activation of the complement system is a hallmark of systemic lupus erythematosus (SLE). Antimicrobial neutrophil extracellular traps (NETs) are composed of secreted chromatin that may act as a source of autoantigens typical for SLE. In this study, we investigated how complement interacts with NETs and how NET degradation is affected by complement in SLE patients. We found that sera from a subset of patients with active SLE had a reduced ability to degrade in vitro-generated NETs, which was mostly restored when these patients were in remission. Patients that failed to degrade NETs had a more active disease and they also displayed lower levels of complement proteins C4 and C3 in blood. We discovered that NETs activated complement in vitro and that deposited C1q inhibited NET degradation including a direct inhibition of DNase-I by C1q. Complement deposition on NETs may facilitate autoantibody production, and indeed, Abs against NETs and NET epitopes were more pronounced in patients with impaired ability to degrade NETs. NET-bound autoantibodies inhibited degradation but also further increased C1q deposition, potentially exacerbating the disease. Thus, NETs are a potent complement activator, and this interaction may play an important role in SLE. Targeting complement with inhibitors or by removing complement activators such as NETs could be beneficial for patients with SLE.
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| 10. |
- Leffler, Jonatan, et al.
(author)
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The complement system in systemic lupus erythematosus: an update.
- 2014
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In: Annals of the Rheumatic Diseases. - : BMJ. - 1468-2060 .- 0003-4967. ; 73:9, s. 1601-1606
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Research review (peer-reviewed)abstract
- The complement system plays a major role in the autoimmune disease, systemic lupus erythematosus (SLE). However, the role of complement in SLE is complex since it may both prevent and exacerbate the disease. In this review, we explore the latest findings in complement-focused research in SLE. C1q deficiency is the strongest genetic risk factor for SLE, although such deficiency is very rare. Various recently discovered genetic associations include mutations in the complement receptors 2 and 3 as well as complement inhibitors, the latter related to earlier onset of nephritis. Further, autoantibodies are a distinct feature of SLE that are produced as the result of an adaptive immune response and how complement can affect that response is also being reviewed. SLE generates numerous disease manifestations involving contributions from complement such as glomerulonephritis and the increased risk of thrombosis. Furthermore, since most of the complement system is present in plasma, complement is very accessible and may be suitable as biomarker for diagnosis or monitoring of disease activity. This review highlights the many roles of complement for SLE pathogenesis and how research has progressed during recent years.
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| 11. |
- Martin, Myriam, et al.
(author)
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Annexin A2 and A5 serve as new ligands for C1Q on apoptotic cells.
- 2012
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In: Journal of Biological Chemistry. - 1083-351X. ; 287:40, s. 33733-33744
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Journal article (peer-reviewed)abstract
- C1q is the initiator of the classical complement pathway and opsonizes apoptotic cells to facilitate phagocytosis. Deficiency of C1q is the strongest known risk factor for development of systemic lupus erythematosus (SLE)a, which appears to be related to ensuing impaired clearance of apoptotic material. The objective of the current study was to investigate new ligands for C1q on the surface of apoptotic cells. We revealed that the two phospholipid-binding proteins annexin A2 and A5 are, beside DNA, significant C1q ligands. We furthermore demonstrated that C1q binds directly to histones exposed on the surface of dying cells but we did not detect significant interaction with phosphatidylserine. The complement inhibitors C4b-binding protein (C4BP) and factor H (FH) also interact with dying cells, most likely to decrease complement activation beyond the level of C3 in order to allow non-inflammatory clearance. Despite the fact that C4BP, FH and C1q share some ligands on dying cells, we showed that these three proteins did not compete with one another for binding to apoptotic cells. We additionally demonstrated that the way in which apoptosis is induced influenced both the degree of apoptosis and the binding of C1q. The knowledge, that annexin A2 and A5 act as ligands for C1q on apoptotic cells, sheds new light on the pathophysiology of autoimmune diseases.
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| 12. |
- Martin, Myriam, et al.
(author)
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Factor H uptake regulates intracellular C3 activation during apoptosis and decreases the inflammatory potential of nucleosomes.
- 2016
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In: Cell Death and Differentiation. - : Springer Science and Business Media LLC. - 1350-9047 .- 1476-5403. ; 23, s. 903-911
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Journal article (peer-reviewed)abstract
- Factor H (FH) binds apoptotic cells to limit the inflammatory potential of complement. Here we report that FH is actively internalized by apoptotic cells to enhance cathepsin L-mediated cleavage of endogenously expressed C3, which results in increased surface opsonization with iC3b. In addition, internalized FH forms complexes with nucleosomes, facilitates their phagocytosis by monocytes and induces an anti-inflammatory biased cytokine profile. A similar cytokine response was noted for apoptotic cells coated with FH, confirming that FH diminishes the immunogenic and inflammatory potential of autoantigens. These findings were supported by in vivo observations from CFH(-/-) MRL-lpr mice, which exhibited higher levels of circulating nucleosomes and necrotic cells than their CFH(+/+) littermates. This unconventional function of FH broadens the established view of apoptotic cell clearance and appears particularly important considering the strong associations with genetic FH alterations and diseases such as systemic lupus erythematosus and age-related macular degeneration.Cell Death and Differentiation advance online publication, 15 January 2016; doi:10.1038/cdd.2015.164.
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| 13. |
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| 14. |
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| 15. |
- Martin, Myriam, et al.
(author)
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Plasma C4d as marker for lupus nephritis in systemic lupus erythematosus
- 2017
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In: Arthritis Research and Therapy. - : Springer Science and Business Media LLC. - 1478-6354 .- 1478-6362. ; 19:1
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Journal article (peer-reviewed)abstract
- Background: In the present study, we sought to evaluate the complement activation product C4d as a marker for lupus nephritis in systemic lupus erythematosus (SLE). Methods: C4d levels were determined by enzyme-linked immunosorbent assay in plasma samples of patients with established SLE using a novel approach based on detection of a short linear cleavage neoepitope. Cross-sectional associations were studied in 98 patients with SLE with samples taken at lower or higher respective disease activity. Temporal associations were investigated in 69 patients with SLE who were followed longitudinally for up to 5 years. Plasma samples from 77 healthy donors were included as controls. Results: C4d levels were negligible in healthy control subjects and significantly increased in patients with SLE in the cross-sectional study (p < 0.0001). C4d levels discriminated between higher and lower disease activity according to ROC curve analysis (p < 0.001), exhibiting a positive predictive value of 68%. At higher disease activity, C4d levels correlated with the modified Systemic Lupus Erythematosus Disease Activity Index (p = 0.011) and predominantly with lupus nephritis (p = 0.003), exhibiting a sensitivity of 79% to identify patients with nephritis. High C4d levels together with the presence of anti-dsDNA autoantibodies preceded and thus predicted future lupus nephritis in the longitudinal study (OR 5.4, 95% CI 1.4-21.3). When we considered only patients with renal involvement (19 of 69) during the longitudinal study, we found that high C4d levels alone could forecast recurrence of future lupus nephritis (OR 3.3, 95% CI 1.2-9.6). Conclusions: C4d appears to be a valuable marker for use in monitoring of patients with SLE, particularly for lupus nephritis. Importantly, C4d levels can predict impending flares of lupus nephritis and may thus be useful for informing treatment.
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