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Arteriosclerosis, Thrombosis, and Vascular Biology. 1999;19:2807-2811

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(Arteriosclerosis, Thrombosis, and Vascular Biology. 1999;19:2807.)
© 1999 American Heart Association, Inc.

Thrombosis

ß2-Glycoprotein I Promotes the Binding of Anionic Phospholipid Vesicles by Macrophages

Perumal Thiagarajan; Anhquyen Le; Claude R. Benedict

From the Divisions of Hematology (P.T., A.L.) and Cardiology (C.R.B.), Department of Internal Medicine, University of Texas Health Sciences Center, Houston.

Correspondence to Perumal Thiagarajan, MD, University of Texas Health Sciences Center, 6431 Fannin St, MSB 5.284, Houston, TX 77030. E-mail perumal{at}heart.med.uth.tmc.edu


*    Abstract
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 *Abstract
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Abstract—ß2-Glycoprotein I is a single-chain 50-kDa protein that circulates in plasma at a concentration of {approx}200 µg/mL. Its physiological role remains uncertain, but an important clue is the frequent presence of antibodies to this protein in patients with recurrent thrombosis. We have isolated ß2-glycoprotein I and examined its effect on the binding of phosphatidylserine (PS) vesicles by human monocyte–derived macrophages and by phorbol ester–stimulated THP-1 cells. ß2-Glycoprotein I stimulated the binding of PS vesicles by these cells in a concentration-dependent manner. Vesicles containing other anionic phospholipids, such as cardiolipin, phosphatidic acid, or cardiolipin, inhibited the binding, whereas PC vesicles had no effect. Platelet-derived microvesicles, which contain anionic phospholipid on the outer leaflet of their phospholipid bilayer, also inhibited ß2-glycoprotein I–dependent binding of anionic phospholipid vesicles. The binding is associated with incorporation of phospholipid in the cell membrane and internalization of ß2-glycoprotein I. These findings suggest a physiological function for ß2-glycoprotein I in the clearance of procoagulant anionic phospholipid-containing cell surfaces from the circulation.


Key Words: lupus anticoagulant • antiphospholipid antibody • ß2-glycoprotein I • anionic phospholipid vesicles


*    Introduction
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ß2-Glycoprotein I is a single-chain 50-kDa lipid-binding serum glycoprotein first identified in 1961.1 The plasma concentration of this glycoprotein is {approx}4 µmol/L (200 µg/mL), of which one third is bound to lipoproteins.2 Because of its association with lipoprotein fractions, ß2-glycoprotein I is also referred to as apolipoprotein H. Human ß2-glycoprotein I was completely sequenced and cloned, and the gene has been localized to chromosome 17.3 4 5 ß2-Glycoprotein I is a member of the so-called "complement control protein" (CCP) superfamily,6 7 whose members are identified by the presence of >=1 repeats of {approx}60 amino acid sequences characterized by a relatively invariant arrangement of 2 disulfide bonds and a number of other highly conserved residues. ß2-Glycoprotein I is made up of 5 complement control protein repeats, the fifth of which has a relatively unusual pattern of 3 disulfide bridges and contains a positively charged sequence, CKNKEKKC, that has been shown to be a binding site for anionic phospholipid.8

The physiological role of ß2-glycoprotein I remains uncertain. It has been reported to bind negatively charged surfaces, including anionic phospholipid vesicles,9 platelets,10 platelet-derived microparticles,11 and apoptotic cells.12 Binding is accompanied in vitro by inhibition of phospholipid-dependent coagulation tests.13 Here, we show that ß2-glycoprotein I promotes the binding and internalization of anionic phospholipid vesicles by macrophages.


*    Methods
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 *Methods
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RPMI medium 1640, cholesterol, and phorbol 12-myristate 13-acetate (PMA) were obtained from Sigma Chemical Co. Bovine brain phosphatidylserine (PS), egg phosphatidylcholine (PC), heart cardiolipin, liver phosphatidylinositol, liver phosphatidylethanolamine, and N-[4-nitro-2-oxa-1,3-diazole]-L-{alpha}-phosphatidylcholine (NBD-PC) were obtained from Avanti Polar Lipids. Butylated hydroxytoluene was added to a final concentration of 100 µmol/mol phospholipid. Carrier-free [125I]NaI was obtained from Amersham Corp. Iodogen was purchased from Pierce Chemical Co.

Isolation of ß2-Glycoprotein I
ß2-Glycoprotein I was isolated from normal citrated plasma as described previously,14 with some modifications. Plasma (100 mL) was mixed with 2.5 mL 70% (vol/vol) perchloric acid, stirred gently at 4°C for 15 minutes, and centrifuged at 13 000g for 15 minutes at 4°C. After the supernatant was neutralized to pH 7.0 with 12.5 mol/L NaOH, 43 g of ammonium sulfate powder was added, and the mixture was stirred at 4°C for 30 minutes. After centrifugation at 13 000g for 15 minutes at 4°C, the precipitate was dissolved in 0.03 mol/L NaCl, 0.02 mol/L Tris-HCl, pH 8.0, and dialyzed against the same buffer. The sample was applied to a column of heparin-Sepharose (2x15 cm) that was washed sequentially with 400 mL 0.05 mol/L NaCl, 0.02 mol/L Tris, pH 8.0, and 400 mL 0.15 mol/L NaCl, 0.02 mol/L Tris, pH 8.0, and then eluted with 0.35 mol/L NaCl, 0.02 mol/L Tris, pH 8.0. The ß2-glycoprotein I–containing peak was dialyzed against a buffer containing 0.05 mol/L HEPES, 0.05 mol/L NaCl, pH 7.0, applied to a Mono S column (Pharmacia Biotech Inc), and eluted with 0.05 to 0.5 mol/L salt gradient in the same buffer. The ß2-glycoprotein I peak was collected and dialyzed against HBS (0.15 mol/L NaCl, 0.02 mol/L HEPES, pH 7.4). ß2-Glycoprotein I was iodinated with [125I]NaI by the Iodogen method.15

Phospholipid Vesicles
Phospholipid-cholesterol vesicles were prepared with a molar ratio of phospholipid to cholesterol of 1:0.75. The phospholipid used was either 100% PS or PC. When mixed vesicles were prepared, the molar concentration of phospholipid was the same with different proportions of PS and PC. Vesicles were prepared with a nonexchangeable tracer, [3H]cholesteryl hexadecyl ether (Amersham Co), to quantify the binding of phospholipid.16 Phospholipid and cholesterol were dissolved in chloroform and evaporated to dryness in a glass ampoule with a gentle stream of dry nitrogen and suspended in 5 mL of buffer (0.15 mol/L NaCl, 0.01 mol/L HEPES, pH 7.4). The suspension was deaerated by bubbling with dry nitrogen for 15 minutes. The ampoule was flame-sealed and placed in a water bath, and the phospholipid suspension was emulsified by sonication (Heat System Ultrasonics, Inc) for 45 minutes, the temperature being maintained at 20°C to 25°C by the addition of ice to the bath. The phospholipid vesicles were then passed through a 0.2-µm filter (Gelman Sciences) and stored at 4°C. The phospholipid vesicles were examined by electron microscopy and negative staining with uranyl acetate and shown to be almost exclusively unilamellar vesicles <200 nm in diameter. Lipid peroxidation products in the phospholipid preparations were measured by the thiobarbituric acid method as described before.17 The lipid peroxide contents were <1.07±0.03 (n=3) nmol/mg of phospholipid. Fluorescent vesicles had the same lipid composition with the addition of NBD-PC (2% of the total phospholipid, wt/wt) but without the tracer.

Cell Lines and Macrophages
THP-1 cells obtained from the American Type Culture Collection were grown in tissue culture flasks under 5% CO2 at 37°C in RPMI 1640 medium containing 10% heat-inactivated FCS. The cells were treated with PMA (100 nmol/L), plated in 24-well plates (Costar) (2x106 cells/plate), and allowed to differentiate for 72 hours. Human monocyte–derived tissue macrophages were prepared by culturing peripheral blood monocytes isolated by the Ficoll-Hypaque gradient method, as previously described.18 Platelet-derived microvesicles were prepared as described before.19 20

Phospholipid Binding Assay
Tissue culture wells containing 2x106 adherent, differentiated THP-1 cells or 0.5x106 monocyte-derived macrophages were washed in PBS and replaced with serum-free Medium 199 containing various concentrations of [3H]cholesterol-labeled phospholipid vesicles. The medium contains 1 mmol/L Ca2+. ß2-Glycoprotein I was added and incubated at 37°C for 4 hours. At the end of the incubation period, the cells were rapidly washed 6 times in serum-free Medium 199. The cells were solubilized by incubation in a 200-µL volume of 2% SDS for 20 minutes. The cell-associated radioactivity was counted in a scintillation counter. To correct for nonspecific binding, in each experiment, parallel wells containing tissue culture medium without cells were incubated with ß2-glycoprotein I and anionic phospholipid vesicles, and the binding was subtracted from total binding.

Flow Cytometric Analysis of Incorporation of Phospholipid
Phorbol ester–stimulated THP-1 cells were incubated with fluorescent-PS vesicles (100 µmol/L) in serum-free medium in the presence or absence of ß2-glycoprotein I (100 µmol/L). After 4 hours of incubation at 37°C, the cell layers were washed in serum-free medium and trypsinized. The single-cell suspensions of THP-1 cells were analyzed for cell-associated fluorescence by flow cytometry.

Internalization of 125I-Labeled ß2-Glycoprotein I
THP-1 cells (15x106) were seeded in 60-mm tissue culture dishes (Corning Glass Works) in the presence of 100 nmol/L PMA. Three days later, cell layers were washed 3 times in serum-free medium, and 1 mL of medium containing 3% BSA and 400 nmol/L 125I-ß2-glycoprotein I was added. After incubation for 1 hour at 37°C, the overlying medium was removed, and the cells were incubated for 30 minutes at 4°C in tissue culture medium containing 0.25% Pronase, which removes cell surface ligands and also detaches the cells. The detached cells were separated from the medium by centrifugation and washed 3 times. Radioactivity associated with the cell pellet (internalized Pronace-insensitive ligand) was determined in a gamma counter.


*    Results
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Effect of ß2-Glycoprotein I on the Binding of Anionic Phospholipid Vesicles
As shown in Figure 1ADown, when phorbol ester–stimulated THP-1 cells were incubated with PS vesicles (75 µmol/L) at 37°C in the presence of ß2-glycoprotein I, the vesicle binding was linear for 2 hours and reached saturation at 2.5 to 3 hours. In the absence of ß2-glycoprotein I, the vesicle binding was decreased by 90%. Binding was dependent on the concentrations of both PS vesicles (Figure 1BDown) and ß2-glycoprotein I (Figure 1CDown) and was optimal at 150 µmol/L of PS and at 100 µg/mL of ß2-glycoprotein I. The effect of ß2-glycoprotein I on PS vesicle binding was temperature-dependent (Figure 1DDown): PS binding at 4°C was {approx}20% of the binding at 37°C. Binding of PC vesicles by THP-1 cells under the same conditions was 20-fold less, and ß2-glycoprotein I did not have any stimulatory effect on the binding. When peripheral blood monocyte-derived macrophages were incubated with PS, a similar ß2-glycoprotein I–dependent binding of anionic phospholipid vesicles was seen (Figure 2Down). The ß2-glycoprotein I–dependent binding of PS vesicles to THP-1 cells is proportional to the concentration of PS in the vesicles (Figure 3Down). Binding increases when the PS content is >10% of total phospholipids.



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  		Figure 1. Binding of PS vesicles by THP-1 cells. A, Time course. PMA-stimulated THP-1 cells were incubated with [3H]cholesterol-labeled PS vesicles (75 µmol/L) in tissue culture wells at 37°C for the indicated times in the presence ({circ}) or absence (•) of 100 µg/mL of ß2-glycoprotein I, and the cell-bound radioactivity was determined after washing. B, Concentration dependence of PS vesicle binding. The cells were incubated in the presence ({circ}) or absence (•) of 100 µg/mL of ß2-glycoprotein I and various concentrations of PS vesicles at 37°C, and the cell-bound radioactivity was determined after 4 hours of incubation. C, ß2-Glycoprotein I concentration dependence of PS vesicle binding. The cells were incubated with PS vesicles (75 µmol/L) and various concentrations of ß2-glycoprotein I at 37°C, and the cell-bound radioactivity was determined after 4 hours of incubation. The error bars reflect the SDs of triplicate determinations. D, Temperature dependence. PS binding at 4°C and at 37°C. Conditions were similar to those in panel B.



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  		Figure 2. Binding of PS vesicles by peripheral blood monocyte-derived macrophages. Human peripheral blood monocyte-derived macrophages were grown in tissue culture wells and incubated with various concentrations of PS vesicles as in Figure 1BUp, and the binding was determined as before. The error bars reflect the SDs of triplicate determinations.



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  		Figure 3. Binding of PS vesicles depends on the content of PS. Phorbol ester–stimulated THP-1 cells were incubated with ß2-glycoprotein I (100 µg/mL) and various concentrations of PS vesicles (75 µmol/L) containing different amounts of PS, and binding was measured as in Figure 1BUp.

Effect of Phospholipid Composition on ß2-Glycoprotein I–Dependent Binding of Anionic Phospholipid Vesicles
Anionic phospholipid vesicles containing PS, phosphatidic acid, or cardiolipin (Figure 4Down) inhibited binding of the radiolabeled PS vesicles, whereas neutral or zwitterionic phospholipid vesicles composed of PC (Figure 4Down), sphingomyelin, or phosphatidylethanolamine (data not shown) had no effect. Incorporation of dicetyl phosphate or stearylamine to give a net negative or positive charge to the phospholipid vesicles, respectively, had no significant effect on the binding, suggesting that charge alone does not confer ß2-glycoprotein I–dependent binding (data not shown). Platelet-derived microvesicles have previously been shown to contain anionic phospholipid on their outer surface.20 Inhibition of ß2-glycoprotein I–dependent binding of PS vesicles is consistent with these observations (Figure 4Down).



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  		Figure 4. Effect of unlabeled phospholipid vesicles on the binding of PS vesicles by the THP-1 cells. Phorbol ester–stimulated THP-1 cells were incubated with radiolabeled PS vesicles (75 µmol/L) and ß2-glycoprotein I (100 µg/mL) in the presence of various inhibitors, and the cell-bound radioactivity was determined after 4 hours of incubation at 37°C. The unlabeled phospholipid concentration was 1.5 mmol/L. The microparticles are derived from supernatants from calcium ionophore A23187–stimulated platelets at a concentration of 109/mL. The binding in the presence of HBS is considered to be 100%.

ß2-Glycoprotein I–Dependent Incorporation of Anionic Phospholipid
To determine whether the enhanced binding of anionic phospholipid vesicles to macrophage membranes is associated with incorporation of phospholipids in the membrane, fluorescent PS vesicles containing NBD-PC as fluorescent tracer were incubated with phorbol ester–stimulated THP-1 cells in the presence of ß2-glycoprotein I. The cell-bound phospholipid vesicles were analyzed by flow cytometry. The presence of ß2-glycoprotein I resulted in increased incorporation of PS-containing fluorescent phospholipids (Figure 5Down). No significant effect of ß2-glycoprotein I was seen when cells were incubated with PC-containing vesicles.



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  		Figure 5. Binding of anionic phospholipid vesicles by THP-1 cells. PMA-stimulated THP-1 cells were incubated with fluorescein-labeled PS or PC vesicles in the presence or absence of ß2-glycoprotein I for 4 hours at 37°C. The cells are washed and trypsinized, and the single-cell suspension of THP-1 was examined for fluorescence by flow cytometry.

PS Vesicle–Dependent Internalization of ß2-Glycoprotein I by THP-1 Cells
To determine whether incubation of ß2-glycoprotein I with PS vesicles results in the internalization of ß2-glycoprotein I, 125I-labeled ß2-glycoprotein I (400 nmol/L) was incubated with phorbol ester–stimulated THP-1 cells in the presence of PS or PC vesicles. There was a dose-dependent increase in the internalization of ß2-glycoprotein I by PS vesicles, whereas PC vesicles had no significant effect (Figure 6Down).



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  		Figure 6. PS vesicles induced internalization of ß2-glycoprotein I by THP-1 cells. PMA-stimulated THP-1 cells were incubated with PS vesicles (100 µmol/L) and 400 nmol/L 125I-labeled ß2-glycoprotein I for 4 hours at 37°C. The cells were washed, treated with Pronace (0.25% wt/vol) at 4°C for 30 minutes, and washed again, and the cell-bound radioactivity was determined.


*    Discussion
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 *Discussion
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The experiments reported here show that ß2-glycoprotein I promotes the binding of anionic phospholipid vesicles to macrophages. This effect is saturable, temperature-dependent, and specific for anionic phospholipids. Cell surfaces containing anionic phospholipids, such as platelet-derived microvesicles, inhibit this binding. These studies suggest a physiological function for ß2-glycoprotein I in the clearance of anionic phospholipid-containing procoagulant surfaces from the circulation. The complex of anionic phospholipid vesicles and ß2-glycoprotein I is recognized by a putative cell surface receptor on macrophages or possibly other cells. These complexes are taken into a receptor-mediated pathway, and this may play a role in the removal of procoagulant anionic phospholipid surfaces from the circulation. Wurm et al21 showed that infusion of ß2-glycoprotein I in rats results in an accelerated clearance of triglyceride-rich vesicles from the circulation, and Chonn et al22 showed ß2-glycoprotein I–dependent clearance of anionic phospholipid vesicles in mice. Our results showing that ß2-glycoprotein I enhances the binding of anionic phospholipid to macrophages are consistent with these reports.

Nishikawa et al23 first reported in 1990 that macrophage scavenger receptor mediates the binding of anionic phospholipid to mouse peritoneal macrophages. However, using Chinese hamster ovary cells transfected with class A bovine macrophage scavenger receptor, Lee et al24 could not demonstrate this effect. The possible role of ß2-glycoprotein I was not studied, and it is possible that the presence of ß2-glycoprotein I might have given these conflicting results. Recently, additional receptors, distinct from the type A scavenger receptors that bind oxidized LDL and PS vesicles, have been identified.25 26 27 At least 1 of these receptors also binds oxidized red blood cells and apoptotic cells by a PS-dependent mechanism.28 The precise identification of the receptor(s) that mediates ß2-glycoprotein I–dependent binding of anionic phospholipid vesicles will require transfection studies with these candidate receptors.

Decreased levels of ß2-glycoprotein I have been reported in disseminated intravascular coagulation, a condition associated with platelet activation and generation of microvesicles in vivo.29 30 In addition, patients with antiphospholipid antibody syndrome have in their serum immunoglobulins that react with anionic phospholipids in a variety of immunological assays.31 The precise antigenic target of antiphospholipid antibodies, whether neoepitopes induced in protein, such as ß2-glycoprotein I, after phospholipid or surface binding or a complex conformational epitope consisting of protein and phospholipid, has not been resolved and is a subject of controversy.9 31 32 33 34 At least some of these antibodies recognize a complex epitope consisting of anionic phospholipid bound to ß2-glycoprotein I and other phospholipid-binding proteins.31 32 These antibodies may impair the clearance of ß2-glycoprotein I–dependent binding of anionic phospholipid vesicles by interfering with the binding and/or internalization of procoagulant anionic phospholipid surfaces of activated platelets and apoptotic cells, allowing prolonged survival of procoagulant anionic phospholipid vesicles in the circulation. In fact, increased levels of platelet-derived microvesicles have been reported in the plasma of patients with the antiphospholipid antibody syndrome.35 However, hereditary deficiency of ß2-glycoprotein I does not appear to be associated with risk of a hypercoagulable state.36 Thrombosis is a complex multigene phenotype. Because of the large number of genes that influence this phenotype, teasing out the role of the ß2-glycoprotein I locus will be difficult. One would expect that ß2-glycoprotein I deficiency would contribute to a prothrombotic tendency when it is coincident with other genetic risks for thrombosis, for example, heterozygosity for factor V Leiden. When these studies were in progress, Balasubramanian et al37 reported that human ß2-glycoprotein I did not stimulate the uptake of PS vesicles by mouse macrophages. However, the concentration of ß2-glycoprotein I used in that study (5 µg/mL) was at least 10 times lower than the physiological concentration. Furthermore, species differences could account for the differences. Manfredi et al38 did not find a significant role for ß2-glycoprotein I in the phagocytosis of apoptotic T cells by macrophages. They used 10% serum as a source of ß2-glycoprotein I, a suboptimal concentration for enhanced binding. Furthermore, the extent of PS exposure may vary under different conditions, giving rise to negative effects.

In conclusion, our results show that ß2-glycoprotein I promotes the binding of anionic phospholipid-containing vesicles by a macrophage. This mechanism may have a physiological role in removing procoagulant phospholipid vesicles or cell fragments from circulation.


*    Acknowledgments
 
This work was supported by NIH grants HL-40860, HL-50100, and HL-50653 and a Grant-in-Aid from the American Heart Association. We thank Dr I. Jialal for thiobarbituric acid assays and Dr Jose Lopez for critical review of the manuscript.

Received August 18, 1998; accepted March 26, 1999.


*    References
up arrowTop
 up arrowAbstract
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 *References
 

  1. Schultze HE, Heide K, Haupt H. Über ein bisher unbekanntes niedermolekulares ß2-Globulin des Humanserums. Naturwissenschaften. 1961;48:719–721.
  2. Polz E, Kostner GM, Holasek A. Studies on the protein composition of human serum very low density lipoproteins: demonstration of the ß2-glycoprotein-1. Hoppe Seylers Z Physiol Chem. 1979;360:1061–1067.[Medline] [Order article via Infotrieve]
  3. Lozier J, Takahasi N, Putnam FW. Complete amino acid sequence of human plasma ß2-glycoprotein I. Proc Natl Acad Sci U S A. 1984;81:3640–3644.[Abstract/Free Full Text]
  4. Steinkasserer A, Estaller C, Weiss EH, Sim RB, Day AJ. Complete nucleotide and deduced amino acid sequence of human beta 2-glycoprotein I. Biochem J. 1991;277:387–391.
  5. Haagerup A, Kristensen T, Kruse TA. Polymorphism and genetic mapping of the gene encoding human ß2-glycoprotein I to chromosome 17. Cytogenet Cell Genet. 1991;8:2004–2012.
  6. Bottenus RE, Ichinose A, Davie EW. Nucleotide sequence of the gene for the ß subunit of human factor XIII. Biochemistry. 1990;29:11195–11209.[Medline] [Order article via Infotrieve]
  7. Day AJ, Campbell RD, Reid KBM. The mosaic nature of the complement proteins. Prog Immunol. 1989;7:209–212.
  8. Hunt J, Krilis SA. The fifth domain of ß2-glycoprotein I contains a phospholipid binding site and a region recognized by antiphospholipid antibodies. J Immunol.. 1994;152:653–659.[Abstract]
  9. Wurm H. ß2-Glycoprotein-I (apolipoprotein H) interactions with phospholipid vesicles. Int J Biochem. 1984;16:511–515.[Medline] [Order article via Infotrieve]
  10. Schousboe I. Binding of ß2-glycoprotein I to platelets: effect of adenylate cyclase activity. Thromb Res. 1980;19:225–237.[Medline] [Order article via Infotrieve]
  11. Nomura S, Yanabu M, Miyake T, Miyazaki Y, Kido H, Kagawa H, Fukuhara S, Komiyama Y, Matsuura E, Koike T. Relationship of microparticles with beta 2-glycoprotein I and P-selectin positivity to anticardiolipin antibodies in immune thrombocytopenic purpura. Ann Hematol. 1995;70:25–30.[Medline] [Order article via Infotrieve]
  12. Price BE, Rauch J, Shia MA, Walsh MT, Lieberthal W, Gilligan HM, O’Laughlin T, Koh JS, Levine JS. Antiphospholipid antibodies bind to apoptotic but not to viable thymocytes in a ß2-glycoprotein I-dependent manner. J Immunol.. 1996;157:2201–2208.[Abstract]
  13. Nimpf J, Bevers EM, Bomans PH, Till U, Wurm H, Kostner GM, Zwaal RF. Prothrombinase activity of human platelets is inhibited by beta 2-glycoprotein-I. Biochim Biophys Acta. 1986;884:142–149.[Medline] [Order article via Infotrieve]
  14. Finlayson JS, Mushinski JF. Separation of subfractions of human beta-2-glycoprotein I. Biochim Biophys Acta. 1967;147:413–420.[Medline] [Order article via Infotrieve]
  15. Bolton AE, Lee-Own V, McLean RK, Challand GS. Three different radioiodination methods for human spleen ferritin compared. Clin Chem. 1979;25:1826–1830.[Abstract/Free Full Text]
  16. Greenspan P, Gutman RL. Endocytosis of sulfatides by macrophages: relationship to the cellular binding of phosphatidylserine. J Leukoc Biol. 1994;55:99–104.[Abstract]
  17. Agil A, Fuller CJ, Jialal I. Susceptibility of plasma to ferrous iron/hydrogen peroxide-mediated oxidation: demonstration of a possible Fenton reaction. Clin Chem. 1995;41:220–225.[Abstract/Free Full Text]
  18. Bevilacqua MP, Amrani D, Mosesson MW, Bianco C. Receptors for cold-insoluble globulin (plasma fibronectin) on human monocytes. J Exp Med. 1981;153:42–60.[Abstract/Free Full Text]
  19. Sims PJ, Wiedmer T, Esmon CT, Weiss HJ, Shattil SJ. Assembly of the platelet prothrombinase complex is linked to vesiculation of the platelet plasma membrane: studies in Scott syndrome: an isolated defect in platelet procoagulant activity. J Biol Chem. 1989;264:17049–17057.[Abstract/Free Full Text]
  20. Thiagarajan P, Tait JF. Collagen-induced exposure of anionic phospholipid in platelets and platelet-derived microparticles. J Biol Chem. 1991;266:24302–24307.[Abstract/Free Full Text]
  21. Wurm H, Beubler E, Polz E, Holasek A, Kostner G. Studies on the possible function of ß 2-glycoprotein-I: influence in the triglyceride metabolism in the rat. Metabolism. 1982;31:484–486.[Medline] [Order article via Infotrieve]
  22. Chonn A, Semple SC, Cullis PR. Beta 2 glycoprotein I is a major protein associated with very rapidly cleared liposomes in vivo, suggesting a significant role in the immune clearance of "non-self" particles. J Biol Chem. 1995;270:25845–25849.[Abstract/Free Full Text]
  23. Nishikawa K, Arai H, Inoue K. Scavenger receptor-mediated binding and metabolism of lipid vesicles containing acidic phospholipids by mouse peritoneal macrophages. J Biol Chem. 1990;265:5226–5231.[Abstract/Free Full Text]
  24. Lee KD, Pitas RE, Papahadjopoulos D. Evidence that the scavenger receptor is not involved in the binding of negatively charged liposomes by cells. Biochim Biophys Acta. 1992;1111:1–6.[Medline] [Order article via Infotrieve]
  25. Sambrano GR, Parthasarathy S, Steinberg D. Recognition of oxidatively damaged erythrocytes by a macrophage receptor with specificity for oxidized low density lipoprotein. Proc Natl Acad Sci U S A. 1992;91:3265–3269.[Abstract/Free Full Text]
  26. Ramprasad MP, Terpstra V, Kondratenko N, Quehenberger O, Steinberg D. Cell surface expression of mouse macrosialin and human CD68 and their role as macrophage receptors for oxidized low density lipoprotein. Proc Natl Acad Sci U S A. 1996;93:14833–14838.[Abstract/Free Full Text]
  27. Rigotti A, Acton SL, Krieger M. The class B receptors SR-BI and CD36 are receptors for anionic phospholipids. J Biol Chem. 1995;270:16221–16224.[Abstract/Free Full Text]
  28. Sambrano GR, Steinberg D. Recognition of oxidatively damaged and apoptotic cells by an oxidized low density lipoprotein receptor on mouse peritoneal macrophages: role of membrane phosphatidylserine. Proc Natl Acad Sci U S A. 1995;92:1396–1400.[Abstract/Free Full Text]
  29. Brighton TA, Hogg PJ, Dai YP, Murray BH, Chong BH, Chesterman CN. ß 2-glycoprotein I in thrombosis: evidence for a role as a natural anticoagulant. Br J Haematol.. 1996;93:185–194.[Medline] [Order article via Infotrieve]
  30. Matsuda J, Wakasugi K, Saitoh N, Tsukamoto M, Miyajima Y, Kazama M, Asami K, Hashimoto M. Low ß 2-glycoprotein I levels in patients with disseminated intravascular coagulation. Am J Hematol. 1993;42:234–235.
  31. Thiagarajan P, Shapiro SS. Lupus anticoagulants and antiphospholipid antibodies. Hematol Oncol Clin North Am. 1999;12:1167–1192.
  32. McNeil HP, Simpson RJ, Chesterman CN, Krilis SA. Anti-phospholipid antibodies are directed against a complex antigen that includes a lipid-binding inhibitor of coagulation: ß2-glycoprotein I (apolipoprotein H). Proc Natl Acad Sci U S A. 1990;87:4120–4124.[Abstract/Free Full Text]
  33. Galli M, Comfurius P, Maassen C, Hemker HC, deBaets MH, vanBreda-Vriesman PJ, Barbui T, Zwaal RF, Bevers EM. Anticardiolipin antibodies (ACA) directed not to cardiolipin but to a plasma cofactor. Lancet. 1990;335:1544–1547.[Medline] [Order article via Infotrieve]
  34. Matsuura E, Igarasi Y, Fujimoto M, Ichikawa K, Koike T. Anticardiolipin cofactor(s) and differential diagnosis of autoimmune disease. Lancet. 1990;336:177–178. Letter.[Medline] [Order article via Infotrieve]
  35. Galli M, Grassi A, Barbui A. Platelet-derived microvesicles in patients with antiphospholipid antibodies. Thromb Haemost. 1993;69:912. Abstract.
  36. Bancsi LF, van der Linden IK, Bertina RM. Beta 2-glycoprotein I deficiency and the risk of thrombosis. Thromb Haemost. 1992;67:649–653.[Medline] [Order article via Infotrieve]
  37. Balasubramanian K, Chandra J, Schroit AJ. Immune clearance of phosphatidylserine-expressing cells by phagocytes: the role of beta2-glycoprotein I in macrophage recognition. J Biol Chem.. 1997;272:31113–31117.[Abstract/Free Full Text]
  38. Manfredi AA, Rovere P, Heltai S, Galati G, Nebbia G, Tincani A, Balestrieri G, Sabbadini MG. Apoptotic cell clearance in systemic lupus erythematosus, II: role of beta2-glycoprotein I. Arthritis Rheum. 1998;41:215–223.[Medline] [Order article via Infotrieve]



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