Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0024141 (systemic lupus erythematosus)
 44,322 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A full-length cDNA coding a human beta 2-glycoprotein I (beta 2-GPI) was introduced into the baculovirus genome to construct a recombinant baculovirus. Spodoptera frugiperda (Sf9) cells were infected with the recombinant baculovirus. A protein (mol. wt 43,000) reactive with anti-beta 2-GPI antisera was produced in the insect cells and secreted into the culture medium. The recombinant beta 2-GPI was purified from the culture supernatant by sequential cardiolipin (CL)-affinity column chromatography and gel filtration. The N-terminal amino acid sequence of the protein was identical to that of the native beta 2-GPI purified from human sera, and a putative signal peptide was cleaved from the secreted form of the recombinant protein. The purified recombinant protein had a cofactor activity which enhances CL binding of anticardiolipin antibodies (aCL) in systemic lupus erythematosus (SLE) patients, as well as the native beta 2-GPI. Thus, the beta 2-GPI expressed in insect cells is an immunologically active cofactor.
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PMID:Expression of anticardiolipin cofactor, human beta 2-glycoprotein I, by a recombinant baculovirus/insect cell system. 832

The authors studied whether or not anticardiolipin antibody (aCL), which is frequently detected in hemophiliacs with human immunodeficiency virus-1 (HIV-1) infection, is dependent on beta 2-glycoprotein I (GPI), a cofactor of cardiolipin (CL). GPI-independent aCL was positive in 27 of 36 hemophiliacs with HIV-1 antibody (75%) and in 23 of 29 patients without HIV-1 antibody (79%). However, only six HIV-1-positive and four HIV-1-negative patients were positive for GPI-dependent aCL. Thus the aCL in these hemophiliacs was GPI independent and therefore different from the aCL found in autoimmune diseases, such as systemic lupus erythematosus.
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PMID:Measurement of beta 2-glycoprotein I (apolipoprotein H)-independent anticardiolipin antibody in human immunodeficiency virus-1-positive and -negative hemophiliacs. 834 43

Cofactor-dependent IgG anti-cardiolipin antibodies (ACA) were examined in sera from various connective tissue diseases by ELISA using purified human beta 2-glycoprotein I. The frequency and titer of cofactor-dependent IgG ACA were higher in patients with SLE than in those with other diseases, such as RA, SSc, PM/DM, overlap syndrome, and MCTD. The predictive value for SLE was 95%. However, all of the ACA were not cofactor-dependent in SLE patients. These results indicated that cofactor-dependent IgG ACA were specific for SLE patients, but the epitopes of ACA were heterogenous, depending on various clinical manifestations.
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PMID:[Distribution of cofactor-dependent anti-cardiolipin antibodies in collagen diseases]. 836 Sep 93

In some individuals, the presence of antibodies to negatively charged phospholipids, currently measured as the lupus anticoagulant, and anticardiolipin antibodies is associated with certain clinical features, particularly a predisposition to both arterial and venous thromboses, thrombocytopenia, and spontaneous abortion. This syndrome is seen in patients with systemic lupus erythematosus (SLE). However, methods for measuring anticardiolipin antibody, especially epitope of anticardiolipin antibody which is not considered cardiolipin itself, but rather a complex of cardiolipin and beta 2-glycoprotein I are not well defined. Although many hypotheses have been proposed to explain the relation between antiphospholipid antibodies and thrombosis, the pathogenesis of thrombosis remains unclear. In this article, some problems in assaying anticardiolipin antibody, characteristics of antiphospholipid antibodies and the clinical significance of these antibodies are reviewed and discussed.
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PMID:[Assay of anticardiolipin antibodies and its clinical significance]. 837 1

We investigated the prevalence of various autoantibodies [anti-cardiolipin antibody (aCL), lupus anticoagulant (LA), immune complexes (ICs), anti-nuclear antibody (ANA), and anti-deoxyribonucleic acid antibody (aDNA)] in hemophiliac individuals with (n = 50) and without (n = 42) infection by human immunodeficiency virus type 1 (HIV-1). The positivity rate for ANA was similar in both groups, and none of the patients was positive for LA and aDNA. aCL was positive in 35 of 50 (70%) HIV-1-positive hemophiliac individuals and 33 of 42 (79%) HIV-1-negative hemophiliac individuals. However, the majority of the aCL was revealed to be beta 2-glycoprotein I independent, thus corresponding to a syphilis type aCL that does not cause the so-called antiphospholipid syndrome. A total of 39 of the 45 HIV-1 positive hemophiliac individuals (87%) and 34 of 41 HIV-1-negative hemophiliac individuals (83%) had at least one type of IC [C1q-, C3d-, and/or murine monoclonal rheumatoid factor (mRF)- IgG]. The mechanism producing various autoantibodies in hemophiliac persons irrespective of their HIV-1 status is still unclear, but pathogens (e.g., HIV-1, hepatitis B, and hepatitis C) and alloantigens in the blood products that these patients require may be possible candidates. The clinical significance of the presence of these autoantibodies and the underlying mechanisms involved both need to be clarified further.
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PMID:High prevalence of anti-cardiolipin antibody, C1q-, C3d-, and mRF-IgG immune complexes, and anti-nuclear antibody in hemophiliacs irrespective of infection with human immunodeficiency virus type 1. 841 Jun 68

Antiphospholipid (aPL) antibodies are of major interest not only because the lupus anticoagulant (LA) causes an inhibition of in vitro blood coagulation, but also because the presence of aPL antibodies confers a risk of thrombosis. The inhibition of in vitro phospholipid-dependent coagulation (LA) is thought to be caused by the binding of LA to procoagulant phospholipid surfaces, thus impeding the clotting process. Another class of aPL antibodies are those originally described to be directed against negatively charged phospholipids, in particular cardiolipin (ACA). ACA are usually directed against a complex antigen consisting of negatively charged phospholipid and a plasma protein, beta 2-glycoprotein I (beta 2-GPI). Further, there is antibody heterogeneity even within individual patients so that ACA and LA are separable using physicochemical techniques such as ion exchange chromatography and chromatofocusing. Using such techniques we have enriched Ig fractions for LA and ACA from two patient plasmas. The majority of Ig with LA activity had a pI of 7.2 to 7.3 whereas ACA had a pI of 5.0 to 5.2. Using these enriched fractions labeled with [125I]-iodine we have shown that LA binds to platelets in a specific and saturable manner. Binding is dependent on thrombin activation. [125I]-ACA behaves differently. Like LA, binding is specific and dependent on thrombin activation but in this case requires the presence of beta 2-GPI. ACA, in the presence of beta 2-GPI, competes for binding with LA suggesting the same or contiguous site. There is no cross-reactivity of these antibodies with GPIIb/IIIa and the most likely binding site is phospholipid. In neither case does LA nor ACA have an effect on thrombin-induced release of serotonin or beta-thromboglobulin nor do they affect platelet aggregation induced by a number of agonists. This antibody binding may play an etiological role in thrombocytopenia associated with aPL, but does not explain thrombosis on the basis of hyperaggregability or increased platelet release.
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PMID:Beta 2-glycoprotein I is a requirement for anticardiolipin antibodies binding to activated platelets: differences with lupus anticoagulants. 844 87

We have recently described the in vitro mechanism of action of anticardiolipin (aCL) and lupus anticoagulant (LA) antibodies in patients with the antiphospholipid syndrome. LA antibodies inhibit coagulation reactions in plasma because they appear to recognize the complex of lipid-bound (human) prothrombin, whereas aCL antibodies require beta 2-glycoprotein I (beta 2-GPI) for binding to anionic phospholipids. aCL antibodies can be divided into two subgroups, according to their behaviour in lipid-dependent coagulation reactions: aCL-type A enhances the anti-coagulant effect of beta 2-GPI, whereas aCL-type B does not. In the present study we investigated the effect of purified aCL-type A and B and of LA antibodies on the procoagulant activity of both Ca-ionophore activated platelets and platelet-derived microvesicles, using an assay system with highly purified bovine coagulation factors Xa, Va, and prothrombin from human and bovine origin. In the absence of beta 2-GPI neither type of aCL was able to inhibit the prothrombinase activity of platelets or microvesicles. However, a strong and dose-dependent inhibition of the prothrombinase activity of both platelets and platelet-derived microvesicles was observed within a few minutes, when aCL-type A antibodies were added in combination with beta 2-GPI. This inhibitory effect was dependent also on the concentration of beta 2-GPI. Conversely, no inhibitory effect of aCL-type B antibodies on platelet- (or microvesicle) prothrombinase activity in the presence of beta 2-GPI could be observed. LA antibodies were able to inhibit in a dose-dependent way the procoagulant activity of activated platelets and platelet-derived microvesicles. With two LA preparations this inhibition was only apparent when human prothrombin was used as substrate, while a third preparation exhibited its inhibitory effect both in the presence of human and bovine prothrombin. The data indicate that, in the presence of their respective cofactors beta 2-GPI and prothrombin, aCL and LA antibodies interact with the membrane of activated platelets and platelet-derived microvesicles in a very similar way as previously observed for their interaction with anionic phospholipid surfaces.
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PMID:Effect of antiphospholipid antibodies on procoagulant activity of activated platelets and platelet-derived microvesicles. 813 94

Clinical significance of IgG phospholipid-dependent anti-beta 2-glycoprotein I (beta 2-GPI) antibodies in patients with antiphospholipid syndrome (APS) was studied. The subjects consisted of 14 patients with primary APS (PAPS) and 32 with secondary APS based on SLE. IgG phospholipid-dependent anti-beta 2-GPI antibodies were examined by ELISA. Incidences of malar rash, arthritis, renal disorder, leucopenia, immunological disorder, and hypocomplementemia were significantly less frequent in patients with PAPS than in those with secondary APS based on SLE. However, sustained positive reactions of IgG anticardiolipin antibodies were found in 86% of patients with PAPS. Frequency of IgG phospholipid-dependent anti-beta 2-GPI antibodies was significantly higher in patients with PAPS (100%) than in those with secondary APS (34%). Moreover, titer of IgG phospholipid-dependent anti-beta 2-GPI antibodies was significantly higher in patients with PAPS than in those with secondary APS. These data indicated that IgG phospholipid-dependent anti-beta 2-GPI antibodies are useful for identifying a subset in patients with APS as well as for studying the mechanism of thrombotic events in these patients.
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PMID:[Clinical subsets and phospholipid-dependent anti-beta 2-glycoprotein I antibodies in antiphospholipid syndrome]. 853 26

beta 2-Glycoprotein I (beta 2-GPI) is a cofactor in the recognition of the phospholipid antigen cardiolipin by anti-cardiolipin antibodies in autoimmune diseases such as systemic lupus erythematosus. We examined the interactions of various forms of bovine beta 2-GPI, such as its intact form, desialylated form (Asialo-beta 2-GPI), N-terminal domain (Domain I), and modified forms of beta 2-GPI and Asialo-beta 2-GPI with nicks in their C-terminal domains, with phospholipid liposomes under different conditions of pH and ionic strength. We found that at neutral pH and low ionic strength, beta 2-GPI became bound to liposome membranes containing cardiolipin, phosphatidylglycerol, phosphatidylserine, phosphatidylserine, phosphatidic acid, or phosphatidylinositol, but not phosphatidylcholine alone. The number of phospholipids involved in the binding seemed to depend on the head group structure of the negatively charged phospholipids, but the dissociation constant did not, being about 10(-8) M, except that for the interaction with phosphatidylinositol, which was one order of magnitude lower. We also found that Domain I and Asialo-beta 2-GPI bound to liposome membranes containing negatively charged phospholipids, and that in the interaction with cardiolipin, their dissociation constants were about 10(-6) and 10(-8) M, respectively. At neutral pH and both low and high ionic strengths, the affinities of the nicked forms of beta 2-GPI and Asialo-beta 2-GPI for cardiolipin were both lower than those of their intact forms but similar to that of Domain I.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Role of the N- and C-terminal domains of bovine beta 2-glycoprotein I in its interaction with cardiolipin. 853 1

Antiphospholipid antibodies in autoimmune sera have been shown to react with a complex of phospholipids (cardiolipin) and a plasma phospholipid-binding protein, beta 2-glycoprotein I (apolipoprotein H). The binding of these antibodies was inhibited by oxidized low-density lipoprotein (LDL) in sera from patients with systemic lupus erythematosus (SLE), suggesting cross-reactivity between antiphospholipid antibodies and antibodies binding to oxidized LDL. We purified antiphospholipid antibodies by cardiolipin-polyacrylamide column from seven SLE sera and studied the reactivity of eluted fractions with cardiolipin-beta 2-glycoprotein I complex and oxidized LDL (malondialdehyde-conjugated LDL) in solid-phase enzyme immunoassay. In four sera the binding of IgG antibodies to cardiolipin-beta 2-glycoprotein I complex and to oxidized LDL appeared in the same fractions, whereas in three sera reactivities against cardiolipin and oxidized LDL were observed, at least in part, in separate fractions. The binding to solid-phase cardiolipin was dependent on the presence of exogenous beta 2-glycoprotein I in all fractions. Our findings show that antiphospholipid antibodies are heterogeneous in their binding to oxidized LDL, indicating that these two antibodies may have different subspecificities. Some eluted fractions reacted only with oxidized LDL, and did not show binding to cardiolipin-beta 2-glycoprotein I complex, suggesting that the lipid part in the antigenic complex might be responsible for the cross-reactivity of these antibodies. Accordingly, the biological functions of antibodies against phospholipid-beta 2-glycoprotein I complex and antibodies against oxidized LDL may also be different.
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PMID:Affinity-purified cardiolipin-binding antibodies show heterogeneity in their binding to oxidized low-density lipoprotein. 862 19


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