| 1. |
- Adler, Anna, et al.
(författare)
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Regulation of the innate immune system by fragmented heparin-conjugated lipids on lipid bilayered membranes in vitro
- 2023
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Ingår i: Journal of materials chemistry. B. - : Royal Society of Chemistry. - 2050-750X .- 2050-7518. ; 11:46, s. 11121-11134
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Tidskriftsartikel (refereegranskat)abstract
- Surface modification with heparin is a powerful biomaterial coating strategy that protects against innate immunity activation since heparin is a part of the proteoglycan heparan sulfate on cell surfaces in the body. We studied the heparinization of cellular and material surfaces via lipid conjugation to a heparin-binding peptide. In the present study, we synthesized fragmented heparin (fHep)-conjugated phospholipids and studied their regulation of the innate immune system on a lipid bilayered surface using liposomes. Liposomes have versatile applications, such as drug-delivery systems, due to their ability to carry a wide range of molecules. Owing to their morphological similarity to cell membranes, they can also be used to mimic a simple cell-membrane to study protein–lipid interactions. We investigated the interaction of complement-regulators, factor H and C4b-binding protein (C4BP), as well as the coagulation inhibitor antithrombin (AT), with fHep-lipids on the liposomal surface. Herein, we studied the ability of fHep-lipids to recruit factor H, C4BP, and AT using a quartz crystal microbalance with dissipation monitoring. With dynamic light scattering, we demonstrated that liposomes could be modified with fHep-lipids and were stable up to 60 days at 4 °C. Using a capillary western blot-based method (Wes), we showed that fHep-liposomes could recruit factor H in a model system using purified proteins and assist in the degradation of the active complement protein C3b to iC3b. Furthermore, we found that fHep-liposomes could recruit factor H and AT from human plasma. Therefore, the use of fHep-lipids could be a potential coating for liposomes and cell surfaces to regulate the immune system on the lipid surface.
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| 2. |
- Bexborn, Fredrik, et al.
(författare)
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The tick-over theory revisited : formation and regulation of the soluble alternative complement C3 convertase (C3(H2O)Bb)
- 2008
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Ingår i: Molecular Immunology. - : Elsevier BV. - 0161-5890 .- 1872-9142. ; 45:8, s. 2370-2379
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Tidskriftsartikel (refereegranskat)abstract
- The molecular interactions between the components of the C3 convertase of the alternative pathway (AP) of complement and its regulators, in both surface-bound and fluid-phase form, are still incompletely understood. The fact that the AP convertase is labile makes studies difficult to perform. According to the so called tick-over theory, hydrolyzed C3, called C3(H(2)O), forms the initial convertase in fluid phase together with factor B. In the present study, we have applied western blot analysis and ELISA together with fluorescence resonance energy transfer (FRET) to study the formation of the fluid-phase AP convertases C3(H(2)O)Bb and C3bBb and their regulation by factor H and factor I at specific time points and, with FRET, in real time. In our hands, factor B showed a higher affinity for C3(H(2)O) than for C3b, although in both cases it was readily activated to Bb. However, the convertase activity of C3bBb was approximately twice that of C3(H(2)O)Bb, as monitored by the generation of C3a. But in contrast, the C3(H(2)O)Bb convertase was more resistant to inactivation by factor H and factor I than was the C3bBb convertase. Under conditions that totally inactivated C3bBb, C3(H(2)O)Bb still retained approximately 25% of its initial activity.
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| 3. |
- Ekdahl, Kristina N, et al.
(författare)
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Cardiovascular disease in haemodialysis : role of the intravascular innate immune system.
- 2017
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Ingår i: Nature Reviews Nephrology. - : Springer Science and Business Media LLC. - 1759-5061 .- 1759-507X. ; 13:5, s. 285-296
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Forskningsöversikt (refereegranskat)abstract
- Haemodialysis is a life-saving renal replacement modality for end-stage renal disease, but this therapy also represents a major challenge to the intravascular innate immune system, which is comprised of the complement, contact and coagulation systems. Chronic inflammation is strongly associated with cardiovascular disease (CVD) in patients on haemodialysis. Biomaterial-induced contact activation of proteins within the plasma cascade systems occurs during haemodialysis and initially leads to local generation of inflammatory mediators on the biomaterial surface. The inflammation is spread by soluble activation products and mediators that are generated during haemodialysis and transported in the extracorporeal circuit back into the patient together with activated leukocytes and platelets. The combined effect is activation of the endothelium of the cardiovascular system, which loses its anti-thrombotic and anti-inflammatory properties, leading to atherogenesis and arteriosclerosis. This concept suggests that maximum suppression of the intravascular innate immune system is needed to minimize the risk of CVD in patients on haemodialysis. A potential approach to achieve this goal is to treat patients with broad-specificity systemic drugs that target more than one of the intravascular cascade systems. Alternatively, 'stealth' biomaterials that cause minimal cascade system activation could be used in haemodialysis circuits.
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| 4. |
- Ekdahl, Kristina N., et al.
(författare)
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Complement inhibition in biomaterial- and biosurface-induced thromboinflammation
- 2016
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Ingår i: Seminars in Immunology. - : Elsevier BV. - 1044-5323 .- 1096-3618. ; 28:3, s. 268-277
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Tidskriftsartikel (refereegranskat)abstract
- Therapeutic medicine today includes a vast number of procedures involving the use of biomaterials, transplantation of therapeutic cells or cell clusters, as well as of solid organs. These treatment modalities are obviously of great benefit to the patient, but also present a great challenge to the innate immune system, since they involve direct exposure of non-biological materials, cells of non-hematological origin as well as endothelial cells, damaged by ischemia-perfusion in solid organs to proteins and cells in the blood. The result of such an exposure may be an inappropriate activation of the complement and contact/kallikrein systems, which produce mediators capable of triggering the platelets and PMNs and monocytes, which can ultimately result in thrombotic and inflammatory (i.e., a thrombo-inflammatory) response to the treatment modality. In this concept review, we give an overview of the mechanisms of recognition within the innate immunity system, with the aim to identify suitable points for intervention. Finally, we discuss emerging and promising techniques for surface modification of biomaterials and cells with specific inhibitors in order to diminish thromboinflammation and improve clinical outcome.
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| 5. |
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| 6. |
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| 7. |
- Ekdahl, Kristina N., et al.
(författare)
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Use of serum or buffer-changed EDTA-plasma in a rapid, inexpensive, and easy-to-perform hemolytic complement assay for differential diagnosis of systemic lupus erythematosus and monitoring of patients with the disease
- 2007
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Ingår i: Clinical and Vaccine Immunology. - 1556-6811 .- 1556-679X. ; 14:5, s. 549-555
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Tidskriftsartikel (refereegranskat)abstract
- We previously described a simplified quantitative hemolytic assay for classical pathway (CP) hemolytic function in serum that has been shown to correlate with the 50% hemolytic complement (CH50) assay. In the present study, we used this assay to compare CP functions; plasma levels of C3, C4, and C3dg; and ratios of C3dg to C3 in healthy individuals and patients with systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA) with different degrees of complement activation. A significant depression in CP function and levels of C4 and C3 and increased C3dg levels and C3dg/C3 ratios were observed in the SLE patients. In patients with RA, CP function was normal, whereas C3, C4, and C3dg levels and the C3dg/C3 ratio were elevated. The SLE results are compatible with systemic complement consumption, whereas the RA data suggest an acute-phase reaction with a normal C3 catabolic rate. To facilitate the handling of patient samples, we also developed a method to restore the hemolytic function of EDTA-plasma by transferring it to Veronal-buffered saline containing the thrombin inhibitor lepirudin. This process inhibits coagulation and enables complement activation, allowing a longer time lag between sample harvesting and testing. These results, combined with previous correlation studies, suggest that the CP hemolytic assay can effectively replace the CH50 assay for routine SLE differential diagnosis and monitoring of disease activity.
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| 8. |
- Engberg, Anna, 1982-, et al.
(författare)
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BLOOD PROTEIN-POLYMER ADSORPTION FINGERPRINTING:IMPLICATIONS FOR UNDERSTANDING HEMOCOMPATIBILITYAND FOR BIOMATERIAL DESIGN
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Within seconds after an artificial material has been implanted into the blood thesurface will be covered by adsorbed plasma proteins. The composition of theprotein layer is determined by the physical-chemical properties of the surface. Asthe layer itself will become the new interface between the material and blood, itis of major importance for the hemocompatibility. In this project we have studiedthe adsorption of proteins to a model material (polystyrene, PS) with the peptidemass fingerprint technique (PMF) analyzed on a Matrix Assisted LaserDesorption/Ionization Time-of-Flight (MALDI-TOF). To further be able to studythe adsorption of plasma proteins to polymer surfaces, we have synthesized 33new polymer compositions with variable surface properties. Six of thosepolymers were selected and their protein binding ability was determined as wellas quantification of adsorption of 20 plasma proteins to the surface of thepolymers. Our results showed that fourteen high abundant plasma proteins werepositively identified on the PS-surface by MALDI-TOF. Further, the resultsshowed that the synthesized polymers had very distinctive adsorption patterns,with enrichment of different proteins after incubation in plasma and serum. Oneof the polymers was shown to adsorb large amounts of the complementactivating recognition protein C1q, which makes this polymer to a potentialactivating surface. Two of the polymers showed a clear enrichment of thecomplement regulating protein vitronectin as well as two apolipoproteins (AI andAIV) to the surface of the polymers, while some of the polymers bound proteinsapproximately in correlation to the concentration found in plasma.
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| 9. |
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| 10. |
- Hamad, Osama A., 1978-, et al.
(författare)
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Complement component C3 binds to activated normal platelets without preceding proteolytic activation and promotes binding to complement receptor 1
- 2010
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Ingår i: Journal of Immunology. - : The American Association of Immunologists. - 0022-1767 .- 1550-6606. ; 184:5, s. 2686-2692
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Tidskriftsartikel (refereegranskat)abstract
- It has been reported that complement is activated on the surface of activated platelets, despite the presence of multiple regulators of complement activation. To reinvestigate the mechanisms by which activated platelets bind to complement components, the presence of complement proteins on the surfaces of nonactivated and thrombin receptor-activating peptide-activated platelets was analyzed by flow cytometry and Western blot analyses. C1q, C4, C3, and C9 were found to bind to thrombin receptor-activating peptide-activated platelets in lepirudin-anticoagulated platelet-rich plasma (PRP) and whole blood. However, inhibiting complement activation at the C1q or C3 level did not block the binding of C3 to activated platelets. Diluting PRP and chelating divalent cations also had no effect, further indicating that the deposition of complement components was independent of complement activation. Furthermore, washed, activated platelets bound added C1q and C3 to the same extent as platelets in PRP. The use of mAbs against different forms of C3 demonstrated that the bound C3 consisted of C3(H(2)O). Furthermore, exogenously added soluble complement receptor 1 was shown to bind to this form of platelet-bound C3. These observations indicate that there is no complement activation on the surface of platelets under physiological conditions. This situation is in direct contrast to a number of pathological conditions in which regulators of complement activation are lacking and thrombocytopenia and thrombotic disease are the ultimate result. However, the generation of C3(H(2)O) represents nonproteolytic activation of C3 and after factor I cleavage may act as a ligand for receptor binding.
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