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PubMed1997

Influence of degraded phosphatidylserine on binding of antiphospholipid antibodies.

BACKGROUND: Antiphospholipid antibodies (aPL) show great heterogeneity. Different phospholipids, with or without protein cofactor(s), and phospholipid binding proteins alone have been proposed as the target molecules for aPL. In order to determine the influence of phospholipid degradation products on the binding of aPL, sera from 6 patients with the antiphospholipid syndrome were studied. METHODS: Fresh and aged phosphatidylserine and cardiolipin were used as coating reagents in solid-phase immunoassay procedures. Antibody reactivity was tested by enzyme-linked immunosorbent assay in the sera and in eluates from columns packed with polystyrene scrapings coated with either cardiolipin or phoshatidylserine. RESULTS: Three reaction patterns of affinity-purified antibodies were seen: (1) reactivity with phosphatidylserine but not with cardiolipin or degraded phosphatidylserine, (2) reactivity with cardiolipin and degraded phosphatidlyserine, and (3) reactivity with all three phospholipid antigens. CONCLUSIONS: Striking differences in the antiphospholipid antibody reactivity with cardiolipin, phosphatidylserine and degraded phosphatidylserine in the presence of serum proteins were observed among patients with venous thromboembolism. The analyses showed that the degradation of phosphatidylserine influences the binding of aPL in in vitro assays.

Adolescent↗
PubMed1991

Patterns of anti-phospholipid antibody specificities.

To determine the importance of assaying for anti-phospholipid (PL) antibodies other than anti-cardiolipin antibodies in patients with putative anti-phospholipid antibody syndrome (APA), 1,513 serum samples from over 399 patients with the potential for thromboembolic disease were tested for IgM, IgG or IgA class antibodies to the following phospholipids: cardiolipin, phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine, phosphatidylglycerol and phosphatidic acid. Non-specific binding was subtracted from total binding of antibodies to each PL to eliminate false positive ELISA results. Only patients whose sera contained antibody levels which were greater than three standard deviations above the means were considered positive. Patients who were positive for anti-PL antibody had antibodies to at least one of six phospholipids tested. Approximately 60% of the positive samples contained antibodies to a phospholipid other than cardiolipin. For IgG class, antibodies to phosphatidylserine were the most prevalent followed by antibodies to phosphatidylethanolamine and cardiolipin. These findings indicate that anti-phospholipid antibody analysis should be performed for more than anti-cardiolipin antibody to detect patients with APA.

Abortion, Habitual↗
PubMed1990

Antiphospholipid antibodies in syphilis.

1. An enzyme-linked immunosorbent assay was used to determine the phospholipid specificity of antibodies present in sera from 35 syphilis patients. 2. Based on the cross-reaction obtained against a mixture of cardiolipin, phosphatidylcholine and cholesterol that is standard for flocculation tests according to the Venereal Disease Research Laboratory (CECON, São Paulo, Brazil), all 35 patients tested positive for antibodies of the IgG class whereas 13 (37%) also had IgM antibodies for the same mixture of lipids. IgG antibodies to cardiolipin were demonstrated in 2 patients (6%) and IgM antibodies in 5 (15%). Significant levels of IgG anti-phosphatidylcholine were detected in 3 patients (9%) and IgM antibodies in 4 (11%). IgG anti-phosphatidylethanolamine antibodies were found in 1 patient (3%) and IgM antibodies in 3 (9%). Antibody binding to cardiolipin plus cholesterol or cardiolipin plus phosphatidylcholine was as effective as when the standard mixture of all 3 lipids was used. 3. A comparison with serum from systemic lupus erythematosus patients and inhibition studies using liposomes of cardiolipin or the mixture of 3 lipids suggests that there are at least 3 groups of anticardiolipin antibodies.

Antibodies, Anti-Idiotypic↗
PubMed1985

Anti-phospholipid antibodies in syphilis and a thrombotic subset of SLE: distinct profiles of epitope specificity.

In a study of connective tissue and infectious disease sera, we have demonstrated IgM and IgG anti-cardiolipin activity, in a solid phase radioimmunoassay, in systemic lupus erythematosus (SLE), rheumatoid arthritis, syphilis and in acute malaria caused by four different species of Plasmodium. The highest values were noted in SLE (IgM anti-cardiolipin P less than 0.005, IgG anti-cardiolipin P less than 0.01), but there was no correlation with anti-dsDNA, rheumatoid factor or VDRL titres in any disease group. Anti-cardiolipin binding was significantly associated with the lupus anticoagulant, thrombocytopenia, spontaneous abortions and thromboses in the SLE patients. Ten SLE sera from this thrombotic subset and 10 syphilitic sera with similar anti-cardiolipin activity, were tested against four phospholipid antigens and showed significantly different anti-phosphatidyl ethanolamine/anti-phosphatidyl serine binding ratios (P less than 0.001). These differences in phospholipid epitope specificity could explain the specificity of the VDRL antigen in syphilis serology, and we discuss a putative role for anti-phosphatidyl serine in the thrombotic diathesis of SLE.

Adult↗
PubMed1987

Immunological specificity and mechanism of action of IgG lupus anticoagulants.

Although observations have implied that lupus anticoagulants have immunologic specificity toward anionic phospholipids, this assumption has been directly demonstrated in only one patient with a monoclonal IgM paraprotein. We tested the generality of this hypothesis directly by isolating five IgG lupus anticoagulants from patients with lupuslike syndromes and/or thrombosis. IgG lupus anticoagulant fractions were isolated free of other plasma proteins and free of contaminating phospholipid by adsorption to and elution from cardiolipin-cholesterol-dicetyl phosphate liposomes, followed by chromatography on protein A-Sepharose. Cardiolipin liposomes, but not phosphatidylcholine liposomes, were capable of removing all, or nearly all, lupus anticoagulant activity from patient plasma. The affinity-purified IgG preparations reacted with cardiolipin, phosphatidylserine, phosphatidylinositol, and phosphatidic acid, but not with phosphatidylcholine or phosphatidylethanolamine, and inhibited calcium-dependent binding of prothrombin and of factor X to phosphatidylserine-coated and to cardiolipin-coated surfaces. F(ab')2 fragments retained lupus anticoagulant activity and bound to cardiolipin in an enzyme-linked immunosorbent assay (ELISA). Anticardiolipin and lupus anticoagulant activity were both present in acidic fractions on isoelectric focusing. These data strongly suggest that most, if not all, lupus anticoagulants are antibodies that have immunologic specificity towards anionic phospholipids, thereby blocking the calcium-mediated binding of vitamin K-dependent coagulation factors to coagulation-active phospholipid surfaces.

Antibodies↗
PubMed1985

The effect of head group structure on phase transition of phospholipid membranes as determined by differential scanning calorimetry.

The phase transition characteristics of cardiolipin and phosphatidylglycerol suspensions were investigated by differential scanning calorimetry. The phase transition temperatures for dimyristoylphosphatidylglycerol, tetramyristoylcardiolipin, dipalmitoylphosphatidylglycerol and tetrapalmitoylcardiolipin were 25.0, 47.0, 40.5 and 62.2 degrees C, respectively. The phase transition temperature for a mixture of two analogous phospholipids was higher than that for phosphatidylglycerol alone, but lower than that for cardiolipin alone. It increased along with cardiolipin content. The phase transition temperature for cardiolipin was increased in the presence of divalent cations, particularly Ca2+. The results indicate that the head group of cardiolipin by itself can increase the phase transition temperature.

Calorimetry, Differential Scanning↗
PubMed1985

[Antiphospholipid antibodies, thrombosis and lupus disease. Value of the assay of anticardiolipin antibodies by the ELISA technic].

The authors have developed a sensitive immunoenzymatic method for assaying anti-cardiolipin antibodies in the serum of patients with lupus (SLE). These antibodies were present in the serum of 43/108 SLE patients, particularly in those patients with either false syphilis serology (p less than 0.02) or circulating anticoagulant (p less than 0.05). The mean titre of anti-cardiolipin antibodies was higher in the group with positive VDRL (less than 0.03). The anti-cardiolipin antibody titre was independent of the anti-native DNA antibody titre, but there was a correlation with the anti-denatured DNA antibody titre (p less than 0.02). This correlation can be partially explained by the antigenic similarity (phosphodiester bridge) between the two molecules. The preliminary clinical studies have not shown any correlation between the presence of anti-cardiolipin antibodies and the presence of signs such as thrombocytopenia, haemolysis, cerebral vascular accident, venous thrombosis, recurrent abortion. A longitudinal study of certain patients suggests that the anti-cardiolipin antibodies may disappear at the time of thrombotic accidents, which induces fixation of these antibodies to a platelet or vascular target and as a result of corticosteroid therapy.

Antibodies, Antinuclear↗
PubMed1995

Flow cytometric analysis of human epidermal cell ageing using two fluorescent mitochondrial probes.

Cardiolipin, mitochondrial transmembrane potential, cell refringence and cell diameter were examined in epidermal cells obtained from 42 women between 9- to 75-year-old. The study was carried out in situ by flow cytometry on cells having incorporated either Nonyl Acridine Orange or Rhodamine 123, 2 mitochondria-specific dyes. Cardiolipin levels, determined by the binding of the cardiolipin-specific probe Nonyl Acridine Orange, decreased significantly with age, especially in young individuals. This suggests 2 stages in the age-dependent transformation of mitochondria (organelle number and/or size): one during childhood development and to adulthood (9 to 27 years) in which cardiolipin levels decrease dramatically (slope: -3.742; p = 0.0243) and the other corresponding to senescence (35 to 75 years) in which this decrease is less pronounced (slope: -0.618; p = 0.0467). These changes have no effect on mitochondrial potential, measured by Rhodamine 123 incorporation, which remained constant with age. This function, controlling calcium partitioning within the cell, might allow keratinocytes to differentiate and maintain the skin barrier function of the epidermis. Like cardiolipin, intrinsic parameters such as cell size and refringence also significantly decreased in epidermal cells from elderly subjects. The methodology can be used to determine physiological ageing in various cell types and to analyse human ageing and related parameters.

Acridine Orange↗
PubMed1987

Lipid specific penetration of melittin into phospholipid model membranes.

The relative depth of penetration of melittin into egg phosphatidylcholine and bovine heart cardiolipin model membranes was investigated using fluorescence spectroscopy techniques. The tryptophan intrinsic fluorescence shift suggests a more hydrophobic surrounding of this residue in cardiolipin, while the accessibility for charged and uncharged aqueous quenchers is decreased in the cardiolipin system when compared with the phosphatidylcholine-bound situation. A lipid incorporated hydrophobic, collisional quencher and a resonance energy transfer acceptor on the other hand are more effective in quenching the tryptophan fluorescence of cardiolipin bound melittin. The combination of these results is interpreted as prove of a deeper positioning of the tryptophan containing part of the peptide molecule in the cardiolipin system in comparison with the situation in phosphatidylcholine. Models that take this difference into account are presented, which try to explain the opposite effect of melittin binding to the two lipid systems with respect to supramolecular structure, as reported in the preceding article (Batenburg, A.M., Hibbeln, J.C.L., Verkleij, A.J. and De Kruijff, B. (1987) Biochim. Biophys. Acta 903, 142-154).

Amino Acids↗
PubMed1998

Site-directed mutational analysis for the membrane binding of DnaA protein. Identification of amino acids involved in the functional interaction between DnaA protein and acidic phospholipids.

DnaA protein, the initiator of chromosomal DNA replication in Escherichia coli, interacts with acidic phospholipids, such as cardiolipin, and its activity seems to be regulated by membrane binding in cells. In this study we introduced site-directed mutations at the positions of hydrophobic or basic amino acids which are conserved among various bacteria species and which are located in the putative membrane-binding region of DnaA protein (from Asp357 to Val374). All mutant DnaA proteins showed much the same ATP and ADP binding activity as that of the wild-type protein. The release of ATP bound to the mutant DnaA protein, in which three hydrophobic amino acids were mutated to hydrophilic ones, was stimulated by cardiolipin, as in the case of the wild-type protein. On the other hand, the release of ATP bound to another mutant DnaA protein, in which three basic amino acids were mutated to acidic ones, was not stimulated by cardiolipin. These results suggest not only that the region is a membrane-binding domain of DnaA protein but also that these basic amino acids are important for the binding and the ionic interaction between the basic amino acids and acidic residues of cardiolipin and is involved in the interaction between DnaA protein and cardiolipin.

Adenosine Diphosphate↗
PubMed1982

Synthesis of various phospholipids from 2-acyl lysophospholipids by Escherichia coli extract.

When 2-[14C]acyl lysophosphatidylethanolamine was incubated with the envelope fraction of E. coli in the presence of Mg2+ ion, phosphatidylethanolamine, acylphosphatidylglycerol and free fatty acid were produced. When 2-[14C]acyl lysophosphatidylglycerol was examined similarly, six phospholipids as well as free fatty acid were produced. These were dilysocardiolipin, lysocardiolipin, phosphatidylglycerol, cardiolipin, bis(monoacylglycero)phosphate and acylphosphatidylglycerol; they were identified by thin layer chromatography, acetolysis and mild alkaline hydrolysis. Studies with an E. coli mutant which is deficient in cardiolipin synthase showed that dilysocardioilipin, lysocardiolipin and cardiolipin were synthesized by cardiolipin synthase. Bis(monoacylglycero)phosphate as well as acylphosphatidylglycerol was produced by acylphosphatidylglycerol synthase. While phosphatidylglycerol and cardiolipin were produced predominantly from 2-acyl lysophosphatidylglycerol, almost the same amounts of dilysocardiolipin, lysocardiolipin and bis(monoacylglycero)phosphate were produced from the 1-acyl and 2-acyl isomers. Metabolites of 2-[14C]acyl lysophosphatidic acid were also examined. Phosphatidic acid, acylphosphatidylglycerol, free fatty acid and monoglyceride were produced, together with a small amount of diglyceride.

Escherichia coli↗
PubMed1994

A human monoclonal IgA autoantibody--185/12--behaves like an autoimmune antiphospholipid antibody.

A human monoclonal anticardiolipin autoantibody (ACA) of the IgA-k isotype, designated 185/12, is described. The antibody was prepared from peripheral B cells, obtained from a patient with a history of habitual abortion, by immortalization with Epstein-Barr virus (EBV). The antibody displays a strong binding activity to cardiolipin and phosphatidyl L-serine, but not to phosphatidylcholine, phosphatidylinositol, ssDNA and dsDNA. It binds to cardiolipin in a concentration-related and saturable manner (Kd = 3.0 x 10(-8) M). This reaction is dependent upon the presence of bovine serum, and is fully inhibited by cardiolipin vesicles. The 185/12 antibody exhibits different binding patterns to the solid-phase bound cardiolipin-serum complex and to its individual components (cardiolipin and bovine serum). The Bmax of 185/12 binding to the complex (0.968 OD units) is higher than the sum of the Bmax values calculated for each one of the complex components (0.352 + 0.179 = 0.531 OD units). Bovine serum as well as purified beta 2-glycoprotein I (beta 2-GPI) in suspension inhibit the binding of 185/12 to the complex. 185/12 binding capacity increases in direct relation to the rising concentration of beta 2-GPI. Collectively, these data may be interpreted to suggest that 185/12 antibody, which is an IgA isotype, exhibits characteristics usually attributed only to antiphospholipid autoantibodies (APA) of the IgG isotype, that are associated with the clinical spectrum of APA syndrome (APA-S). It is, therefore, possible that autoantibodies of the IgA isotype could play a pathogenic role, which may be different from that of the IgG isotype, in the development of autoimmune phenomena.

Abortion, Habitual↗
PubMed1985

Biosynthesis of novel acidic phospholipid analogs in Escherichia coli.

When cultured in the presence of 600 mM D-mannitol, Escherichia coli K-12 cells synthesized two novel phospholipids. The identities of these compounds are postulated to be phosphatidylmannitol and diphosphatidylmannitol, the sugar alcohol analogs of phosphatidylglycerol and cardiolipin, respectively. The nonacylated glycerol moieties of the normal acidic phospholipids were substituted by D-mannitol. The formation of the analogs was significantly enhanced when strains harboring the pss-1 allele, a temperature-sensitive mutation in phosphatidylserine synthase (Ohta and Shibuya, J. Bacteriol. 132:434-443, 1977), were grown at 42 degrees C, and the accumulation of the analogs was maximum in late stationary phase; more than 90% of the total cellular lipids were these novel phospholipids. Strains with a defective cardiolipin synthase (Pluschke et al., J. Biol. Chem. 253:5048-5055, 1978) failed to form the analog lipids, whereas cells with increased cardiolipin synthase activity due to the presence of a pBR322-derived recombinant plasmid containing the structural gene for cardiolipin synthase produced more mannitol lipids than wild-type strains. These observations and the structures of the analog lipids indicated that cardiolipin synthase participates in the formation of these novel phospholipids. We suggest that reversible alcoholysis and condensation, in addition to low substrate specificity of the enzyme, are the mechanisms involved in this process. Addition to the medium of other straight-chain alditols, D-arabitol, ribitol, xylitol, erythritol, and L-threitol also yielded pairs of novel phospholipids, whereas sorbitol or galactitol produced only one analog in small quantities. These acidic phospholipid analogs have not been reported in any living system. They should be useful in the study of structure-function relationships of phospholipids and in manipulating the structures of various membrane systems.

Escherichia coli↗
PubMed2004

Heterogeneity of antibodies to beta2-glycoprotein 1 from patients with systemic lupus erythematosus.

We studied antibodies to beta2-glycoprotein 1 (anti-beta2GP1) from 72 patients with systemic lupus erythematosus (SLE) with or without antiphospholipid syndrome (APS) or with or without anticardiolipin antibodies (aCL). Fifteen patients had APS and positive antiphospholipid antibodies [clinical APS(+)/aPL(+)], 12 patients had APS, negative serum IgG and IgM aCL, antiphosphatidylethanolamine, anti-phosphatidylserine and no lupus anticoagulant [clinical APS(+)/ aPL(-)]. A third group included 16 patients without APS but high aCL levels [clinical APS(-)/ aPL(+)]. In a fourth group we studied 29 patients without clinical manifestations of APS or aCL [clinical APS(-)/aPL(-)]. One hundred anticardiolipin and VDRL-negative normal sera were studied as controls. IgG antibodies to cardiolipin proper in a bovine beta2GP-free system, to human beta2GP1 immobilized on cardiolipin or to human beta2GP1 alone were detected in all sera by ELISA using irradiated and nonirradiated plates from two manufacturers. Sera from APS(+)/aPL(+) patients showed IgG binding to CL, CL + beta2GP1 and beta2GP1 in irradiated and nonirradiated plates. APS(+)/ aPL(-) sera had more significant IgG binding to beta2GP1 than normal controls when studied in both irradiated or nonirradiated plates (P = 0.001). This binding was inhibited by solid-phase cardiolipin in a dose-dependent manner. Sera from the APS(-)/aPL(+) subgroup had comparable IgG activity in both the CL and CL + beta2GP1 assays, while no anti-beta2GP1 activity was detected in these sera. Sera from the clinical APS(-)/aPL(-) patients were negative in the three ELISA systems. Antibodies to human beta2GP1 from SLE patients recognize various epitopes. Those from APS(+)/ aPL(+) patients appear to react with an epitope boosted by cardiolipin in addition to another one present in the native protein. In contrast, anti-beta2GP1 from patients with APS(+)/aPL(-) are blocked by cardiolipin, suggesting that their epitope is the phospholipid-binding site.

Adult↗
PubMed1976

Phospholipids as ionophores.

The ionophoretic capabilities of phospholipids have been examined by direct measurement in a Pressman cell of the phospholipid-mediated translocation of cations across an organic phase separating two aqueous phases. Cardiolipin and phosphatidic acid were the most active inonophores among the phospholipids tested, with activities comparable to that of X537A in respect to the translocation of divalent cations. Cardiolipin translocates both divalent and monovalent cations at approximately equal rates. The ionophoretic activity of cardiolipin could be modulated by other phospholipids (inhibition), by butacaine (stimulation), by complexation with cytochrome c (inhibition), and by ruthenium red and lanthanum (inhibition). The rate of translocation of cations mediated by cardiolipin was independent of pH over a wide pH range (5.4 to 8.3). The same general pattern of properties observed for cardiolipin applied to phosphatidic acid except for stimulation by butacaine. Complexation of phospholipid mixtures, such as asolectin or mitochondrial lipid, with reduced cytochrome c, enhanced the ionophoretic capability of these phospholipids by 1 order of magnitude. The complex thus formed has the properties of a polyionophore. The possible physiological significance of this enormous ionophoretic potential of phospholipids is examined.

Calcium↗
PubMed1989

The nature of the inhibition of 4,7-dioxobenzothiazole derivatives on mitochondrial ubiquinol-cytochrome c reductase.

To investigate the inhibitory action and binding site of a quinone-like molecule, 5-undecyl-6-hydroxy-4,7-dioxobenzothiazole (UHDBT), a series of 4,7-dioxobenzothiazole derivatives were synthesized and their inhibitory efficiencies studied. Replacing the 6-hydroxyl or 2-hydrogen of UHDBT with a bromo or a methoxy group causes only a slight decrease in inhibitory efficiency, indicating that the 6-hydroxyl or the 2-hydrogen of UHDBT is not a structural requirement for inhibition. 5-Undecyl-6-bromo (or methoxy)-4,7-dioxobenzothiazole shows a pH-dependent inhibition similar to that observed with UHDBT, suggesting that the pH dependence is due to the presence of a dissociable group in the protein complex and not to the deprotonation of the hydroxyl group of the inhibitor. Replacing the 6-hydroxyl group with an azido group causes changes similar to those observed with UHDBT; the inhibition is accompanied by alteration of the epr characteristics of reduced iron-sulfur protein in ubiquinol-cytochrome c reductase. The extent of inhibition is not changed upon illumination of the treated reductase. When the photolyzed, 6-azido-5-(1',2'-[3H] undecyl)-4,7-dioxobenzothiazole [( 3H]6-azido-UDBT)-treated reductase is subjected to organic solvent extraction, no radioactivity is found in the reductase protein. Rather, the radioactivity is located in the phospholipid fraction. A [3H]azido-UDBT-cardiolipin adduct, identified after separation of the phospholipid fraction by high performance liquid chromatography, has 6-azido-UDBT linked to an acyl group, not to the head group of the cardiolipin molecule. These results suggest that inhibition by UHDBT is due to perturbation of specific cardiolipin molecules in ubiquinol-cytochrome c reductase. Since UHDBT and 6-azido-UDBT also inhibit the ubiquinol-cytochrome c reductase activity of delipidated reductase (10% of the original lipid remaining) assayed after reconstitution with ubiquinone and phospholipid, and the [3H]azido-UDBT-cardiolipin adduct is also found in the delipidated reductase, the UHDBT-perturbed cardiolipin molecule is structurally indispensable to reductase and it tightly bound to the reductase protein, most likely the quinone binding proteins.

Electron Transport Complex III↗
PubMed1988

Polyspecific human and murine antibodies to diphtheria and tetanus toxoids and phospholipids.

Human-human hybridomas produced from lymphocytes of normal individuals yielded seven clones producing monoclonal antibody reacting with tetanus toxoid. Three of these antibodies cross-reacted with diphtheria toxoid. These three and two others also reacted with cardiolipin and two with other phospholipids. One of the seven antibodies reacted with tetanus and diphtheria toxoids, cardiolipin and single-stranded DNA. All seven antibodies were IgM. To examine further this unusual cross-reactivity serum antibodies from patients with SLE and healthy individuals were affinity-purified to yield diphtheria toxoid antibodies. Six out of nine of these anti-diphtheria preparations contained IgG antibodies which cross-reacted with tetanus toxoid and two of these also reacted with cardiolipin; four preparations cross-reacted with DNA. Anti-cardiolipin and anti-DNA cross-reactivity were found in preparations from both normal and SLE sera. Similar cross-reactivities were demonstrated using four mouse monoclonal IgM antibodies raised against phospholipids. All four of these antibodies reacted with both cardiolipin and tetanus toxoid and two also reacted with diphtheria toxoid and DNA. Using a thiocyanate elution procedure, it was shown that the cross-reactivity of the monoclonal antibodies was not related to their relative affinities. The results clearly indicate that cross-reactive epitopes occur on routinely used toxoid vaccines and self antigens. Antibodies which bind to these cross-reactive epitopes are common and are not restricted in isotype, affinity or species of origin.

Animals↗
PubMed1997

Characterization of beta2-glycoprotein I-dependent and -independent "antiphospholipid" antibodies from lupus-prone NZW/BXSB F1 hybrid male mice.

Male (NZW x BXSB)F1 (W/BF1) mice develop a systemic lupus-like syndrome characterized by thrombocytopenia, coronary vascular disease, nephritis, and anticardiolipin antibodies. Three stable hybridoma cell lines secreting monoclonal anticardiolipin antibodies were developed from these mice by fusing their splenic lymphocytes with nonsecreting myeloma cell line, NS-1. Monoclonal antibody A1.17 reacted with cardiolipin in a beta2-Glycoprotein I-dependent manner. The epitope for this antibody consisted of beta2-glycoprotein I bound to cardiolipin or immobilized on plastic plates. Other anionic phospholipid-binding proteins, such as prothrombin or annexin V, had no significant effect in the reactivity of these antibodies. The specificity is similar to the autoimmune anticardiolipin antibodies described in patients with systemic lupus erythematosus and other infectious diseases. In contrast, monoclonal antibodies A1.72 and A1.84 reacted with cardiolipin in the absence of beta2-glycoprotein I. Beta2-glycoprotein I, either in the fluid phase or bound to cardiolipin, inhibited the binding of these antibodies. The specificity of the latter two antibodies was similar to that described in patients with syphilis and allied disorders. Both types of antibodies had lupus anticoagulant properties. Thus lupus-prone male (NZW x BXSB)F1 (W/BF1) mice develop both beta2-glycoprotein I-dependent and beta2-glycoprotein I-independent anticardiolipin antibodies.

Animals↗