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- Hamad, Osama A., et al.
(författare)
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Contact activation of C3 enables tethering between activated platelets and polymorphonuclear leukocytes via CD11b/CD18
- 2015
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Ingår i: Thrombosis and Haemostasis. - 0340-6245 .- 2567-689X. ; 114:6, s. 1207-1217
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Tidskriftsartikel (refereegranskat)abstract
- Complement component C3 has a potential role in thrombotic pathologies. It is transformed, without proteolytic cleavage, into C3(H2O) upon binding to the surface of activated platelets. We hypothesise that C3(H2O) bound to activated platelets and to platelet-derived microparticles (PMPs) contributes to platelet-PMN complex (PPC) formation and to the binding of PMPs to PMNs. PAR-1 activation of platelets in human whole blood from normal individuals induced the formation of CD16(+)/CD42a(+) PPC. The complement inhibitor compstatin and a C5a receptor antagonist inhibited PPC formation by 50 %, while monoclonal antibodies to C3(H2O) or anti-CD11b inhibited PPC formation by 75-100 %. Using plasma protein-depleted blood and blood from a C3-deficient patient, we corroborated the dependence on C3, obtaining similar results after reconstitution with purified C3. By analogy with platelets, PMPs isolated from human serum were found to expose C3(H2O) and bind to PMNs. This interaction was also blocked by the anti-C3(H2O) and anti-CD11b monoclonal antibodies, indicating that C3(H2O) and CD11b are involved in tethering PMPs to PMNs. We confirmed the direct interaction between C3(H2O) and CD11b by quartz crystal microbalance analysis using purified native C3 and recombinant CD11b/CD18 and by flow cytometry using PMP and recombinant CD11b. Transfectants expressing CD11b/CD18 were also shown to specifically adhere to surface-bound C3(H2O). We have identified contact-activated C3(H2O) as a novel ligand for CD11b/CD18 that mediates PPC formation and the binding of PMPs to PMNs. Given the various roles of C3 in thrombotic reactions, this finding is likely to have important pathophysiological implications.
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- Kozarcanin, Huda, et al.
(författare)
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The lectin complement pathway serine proteases (MASPs) represent a possible crossroad between the coagulation and complement systems in thromboinflammation
- 2016
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 14:3, s. 531-545
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Tidskriftsartikel (refereegranskat)abstract
- The lectin pathway's MASP-1/2 activates coagulation factors but the trigger of the activation is unknown. MASP-1/2 activation was assessed by quantifying complexes between MASPs and antithrombin/C1-inhibitor. Activated platelets and fibrin were demonstrated to activate MASP-1 and MASP-2 both invitro and invivo. These findings may represent a crossroad between the complement and the coagulation systems. Summary Background The activated forms of the complement lectin pathway (LP) proteases MASP-1 and MASP-2 are able to cleave the coagulation factors prothrombin, fibrinogen, factor XIII and thrombin-activatable fibrinolysis inhibitor invitro. In vivo studies also show that MASP-1 is involved in thrombogenesis. Objectives To clarify the not yet identified mechanisms involved in triggering activation of the LP during thrombotic reactions. Methods Novel sandwich-ELISAs for detection of complexes between MASP-1 or MASP-2 and the serpins C1 inhibitor (C1-INH) or antithrombin (AT), were used to specifically detect and quantify the activated forms of MASP-1 and MASP-2. Results Activated platelets were shown by flow cytometry to bind Ficolin-1, -2 and -3 but not MBL, which was associated with activation of MASP-1 and MASP-2. We also demonstrated that fibrin and the plasmin-generated fibrin fragment DD in plasma, bind and activate MASP-1 and MASP-2. As demonstrated by the ELISA and SDS-PAGE/Western blotting, the fibrin-associated activation was reflected in a specific inactivation by AT during clotting without the assistance of heparin. In all other cases the MASPs were, as previously reported, inactivated by C1-INH. In systemic lupus erythematosus patients with thrombotic disease and in polytrauma patients, the levels of activated MASP-1 and MASP-2 in complex with both AT and C1-INH were associated with markers of thrombotic disease and contact/coagulation system activation. Conclusions MASP-1 and MASP-2 are activated during blood clotting. This activation is triggered by activated platelets and by the generation of fibrin during thrombotic reactions invitro and invivo, and may represent a novel activation/amplification mechanism in thromboinflammation.
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| 6. |
- Nilsson Ekdahl, Kristina, et al.
(författare)
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Dangerous liaisons : complement, coagulation, and kallikrein/kinin cross-talk act as a linchpin in the events leading to thromboinflammation
- 2016
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Ingår i: Immunological Reviews. - : Wiley. - 0105-2896 .- 1600-065X. ; 274:1, s. 245-269
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Forskningsöversikt (refereegranskat)abstract
- Innate immunity is fundamental to our defense against microorganisms. Physiologically, the intravascular innate immune system acts as a purging system that identifies and removes foreign substances leading to thromboinflammatory responses, tissue remodeling, and repair. It is also a key contributor to the adverse effects observed in many diseases and therapies involving biomaterials and therapeutic cells/organs. The intravascular innate immune system consists of the cascade systems of the blood (the complement, contact, coagulation, and fibrinolytic systems), the blood cells (polymorphonuclear cells, monocytes, platelets), and the endothelial cell lining of the vessels. Activation of the intravascular innate immune system in vivo leads to thromboinflammation that can be activated by several of the system's pathways and that initiates repair after tissue damage and leads to adverse reactions in several disorders and treatment modalities. In this review, we summarize the current knowledge in the field and discuss the obstacles that exist in order to study the cross-talk between the components of the intravascular innate immune system. These include the use of purified in vitro systems, animal models and various types of anticoagulants. In order to avoid some of these obstacles we have developed specialized human whole blood models that allow investigation of the cross-talk between the various cascade systems and the blood cells. We in particular stress that platelets are involved in these interactions and that the lectin pathway of the complement system is an emerging part of innate immunity that interacts with the contact/coagulation system. Understanding the resulting thromboinflammation will allow development of new therapeutic modalities.
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| 7. |
- Speth, Cornelia, et al.
(författare)
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Complement and platelets : Mutual interference in the immune network
- 2015
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Ingår i: Molecular Immunology. - : Elsevier BV. - 0161-5890 .- 1872-9142. ; 67:1, s. 108-118
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Forskningsöversikt (refereegranskat)abstract
- In recent years, the view of platelets has changed from mere elements of hemostasis to immunological multitaskers. They are connected in manifold ways to other cellular and humoral components of the immune network, one of which is the complement system, a potent player in soluble innate immunity. Our article reviews the crucial and complex interplay between platelets and complement, focusing on mutual regulation of these two interaction partners by their respective molecular mechanisms. Furthermore, the putative relevance of these processes to infectious diseases, inflammatory conditions, and autoimmune disorders, as well as the treatment of patients with biomaterials is highlighted. (C) 2015 Elsevier Ltd. All rights reserved.
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