Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02749 (beta2-glycoprotein I)
 836 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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 investigated beta2-glycoprotein I (beta2GPI) binding to platelet-derived microparticles (PMP) and its effect on GPIIb/IIIa. PMP were isolated from washed human platelets after stimulation with A23187, and analyzed by surface plasmon resonance spectroscopy. Beta2GPI as well as activated protein C (APC) or annexin V bound to PMP-coated sensorchips, demonstrating exposure of anionic phospholipids on immobilized PMP. Beta2GPI binding was impaired by calcium and occurred in a concentration-dependent manner with apparent k(on) = 2.6 x 10(4) M(-1) s(-1) and k(off) = 4.4 x 10(-3) s(-1), corresponding to a KD value of 1.7 x 10(-7) M. When analyzed by flow cytometry, the binding of certain mAbs specific for GPIIb and/or GPIIIa was reduced in the presence of beta2GPI but not of APC or annexin V, whereas the binding of anti-GPIb or anti-P-selectin mAbs, or of soluble fibrinogen remained unchanged. These results suggest a broad but specific influence of beta2GPI on GPIIb/IIIa immunoreactivity, and indicate that beta2GPI may act as a modulator of GPIIb/IIIa-dependent functions of PMP.
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PMID:Beta2-glycoprotein I binding to platelet microparticle membrane specifically reduces immunoreactivity of glycoproteins IIb/IIIa. 1124 54

Three antiphospholipid antibodies (aPLs), namely, antiphosphatidylinositol antibody (antiinositol antibody), antiphosphatidylserine antibody (antiserine antibody), and anticardiolipin. beta 2-glycoprotein I complex antibody (antiCL. beta 2-GPI antibody), were determined in 49 children with idiopathic thrombocytopenic purpura (ITP) consisting of 14 newly-diagnosed cases and 35 chronic cases. Determination of aPL was performed twice in the newly-diagnosed patients, once each during the acute and convalescent phases, and once in the chronic patients. The positive rates in the acute and convalescent phases of the newly-diagnosed group and in the chronic group were, respectively, 14.3%, 28.6%, and 18.8% for the antiinositol antibody, 14.3%, 14.3%, and 15.6% for the antiserine antibody, and 21.4%, 28.6%, and 25.0% for either of these 2 antibodies. Thus, antiinositol and antiserine aPLs were present at high incidences; however, all patients were negative for the antiCL. beta 2-GPI antibody. No correlation was noted between either the antiinositol or the antiserine antibody and peripheral platelet count, anti-GP IIb/IIIa antibody or PAIgG. Thus, although some aPLs are present in both acute and chronic pediatric ITP, the aPLs seems to be of an infectious disease type. No results that suggest possible involvement of aPLs in ITP pathology were obtained.
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PMID:[Antiphospholipid antibodies in children with idiopathic thrombocytopenic purpura]. 1241 85