PEGylated Domain I of Beta-2-Glycoprotein I Inhibits the Binding, Coagulopathic, and Thrombogenic Properties of IgG From Patients With the Antiphospholipid Syndrome.

APS is an autoimmune disease in which antiphospholipid antibodies (aPL) cause vascular thrombosis and pregnancy morbidity. In patients with APS, aPL exert pathogenic actions by binding serum beta-2-glycoprotein I (β2GPI) via its N-terminal domain I (DI). We previously showed that bacterially-expressed recombinant DI inhibits biological actions of IgG derived from serum of patients with APS (APS-IgG).

Performance Evaluation and Clinical Associations of Immunoassays That Detect Antibodies to Negatively Charged Phospholipids Other Than Cardiolipin.

Objectives: We evaluate the performance characteristics of antiphosphatidylserine (anti-PS), antiphosphatidylinositol (anti-PI), and antiphospholipid mixture (APhL) enzyme-linked immunosorbent assays (ELISAs) compared with anticardiolipin (aCL) and anti-β2 glycoprotein I (anti-β2GPI) in a large group of patients with antiphospholipid (aPL)-related diseases.

Methods: Serum samples from 548 patients from the Hopkins and Jamaican systemic lupus erythematosus cohorts, the PROMISSE cohort, and the Antiphospholipid Standardization Laboratory were examined for immunoglobulin G (IgG)/immunoglobulin M (IgM) positivity in aCL, anti-β2GPI, anti-PS, anti-PI, and APhL ELISA assays.

Results: All IgG assays were associated with one or more thrombotic and/or obstetric manifestations, with an increased risk associated with higher antibody titers.

Solid Phase Immunoassay for the Detection of Anti-β Glycoprotein I Antibodies.

The discovery in the 1990s that the protein beta-2-glycoprotein I (βGPI) was an antigen of central importance in the antiphospholipid syndrome (APS) was soon followed by the development of ELISA assays capable of identifying anti-βGPI antibodies recognizing this antigen. The determination of these antibodies has continued to play a major role in the management of APS patients because of their extremely high specificity for diagnosing the disease, despite their relatively poor sensitivity compared to anticardiolipin antibodies. Additionally, there is abundant evidence of the pathogenic capacity of these antibodies.

Solid Phase Immunoassay for the Detection of Anticardiolipin Antibodies.

The anticardiolipin (aCL) test was first developed in the 1980s and proved to be a valuable addition to the lupus anticoagulant assay for identifying patients with a disorder that came to be later known as the antiphospholipid syndrome (APS). Although the test has relatively poor specificity for APS diagnosis, particularly at low positive levels, it has continued to play a major role in the identification and management of these patients because of its high sensitivity and ability to be measured in both serum and plasma, and despite concomitant presence of anticoagulants normally given to APS patients. In this chapter we outline the procedure for producing essential assay components and for performing the aCL ELISA, which can be used to determine the presence of IgG, IgM and IgA aCL antibodies in human samples.

Major Histocompatibility Complex Class II Alleles Influence Induction of Pathogenic Antiphospholipid Antibodies in a Mouse Model of Thrombosis.

Objective: Both environmental and genetic factors are important in the development of antiphospholipid antibodies (aPL) in patients with antiphospholipid syndrome (APS). Currently, the only available data on predisposing genetic factors have been obtained from epidemiologic studies, without mechanistic evidence. Therefore, we studied the influence of major histocompatibility complex (MHC) class II alleles on the production of aPL in a mouse model of APS.

Value of isolated IgA anti-β2 -glycoprotein I positivity in the diagnosis of the antiphospholipid syndrome.

Objective: To examine the prevalence of isolated IgA anti-β2 -glycoprotein I (anti-β2 GPI) positivity and the association of these antibodies, and a subgroup that bind specifically to domain IV/V of β2 GPI, with clinical manifestations of the antiphospholipid syndrome (APS) in 3 patient groups and to evaluate the pathogenicity of IgA anti-β2 GPI in a mouse model of thrombosis.

Methods: Patients with systemic lupus erythematosus (SLE) from a multiethnic, multicenter cohort (LUpus in MInorities, NAture versus nurture [LUMINA]) (n = 558), patients with SLE from the Hopkins Lupus Cohort (n = 215), and serum samples referred to the Antiphospholipid Standardization Laboratory (APLS) (n = 5,098) were evaluated. IgA anti-β2 GPI titers and binding to domain IV/V of β2 GPI were examined by enzyme-linked immunosorbent assay (ELISA).

A prospective open-label pilot study of fluvastatin on proinflammatory and prothrombotic biomarkers in antiphospholipid antibody positive patients.

Objective: To determine if proinflammatory and prothrombotic biomarkers are differentially upregulated in persistently antiphospholipid antibody (aPL)-positive patients, and to examine the effects of fluvastatin on these biomarkers.

Methods: Four groups of patients (age 18-65) were recruited: (a) primary antiphospholipid syndrome; (b) systemic lupus erythematosus (SLE) with antiphospholipid syndrome (APS) (SLE/APS); (c) persistent aPL positivity without SLE or APS (Primary aPL); and (d) persistent aPL positivity with SLE but no APS (SLE/aPL). The frequency-matched control group, used for baseline data comparison, was identified from a databank of healthy persons.

Apolipoprotein E receptor 2 is involved in the thrombotic complications in a murine model of the antiphospholipid syndrome.

Antiphospholipid (aPL)/anti-β(2) glycoprotein I (anti-β(2)GPI) antibodies stimulates tissue factor (TF) expression within vasculature and in blood cells, thereby leading to increased thrombosis. Several cellular receptors have been proposed to mediate these effects, but no convincing evidence for the involvement of a specific one has been provided. We investigated the role of Apolipoprotein E receptor 2 (ApoER2') on the pathogenic effects of a patient-derived polyclonal aPL IgG preparation (IgG-APS), a murine anti-β(2)GPI monoclonal antibody (E7) and of a constructed dimeric β(2)GPI I (dimer), which in vitro mimics β(2)GPI-antibody immune complexes, using an animal model of thrombosis, and ApoER2-deficient (-/-) mice.

Markers of oxidative and nitrosative stress in systemic lupus erythematosus: correlation with disease activity.

Objective: Free radical-mediated reactions have been implicated as contributors in a number of autoimmune diseases, including systemic lupus erythematosus (SLE). However, the potential for oxidative/nitrosative stress to elicit an autoimmune response or to contribute to disease pathogenesis, and thus be useful when determining a prognosis, remains largely unexplored in humans. This study was undertaken to investigate the status and contribution of oxidative/nitrosative stress in patients with SLE.

Statins for the treatment of antiphospholipid syndrome?

Fluvastatin has been shown to revert proinflammatory/prothrombotic effects of antiphospholipid antibodies (aPL) in vitro and in mice. Here, we examined whether fluvastatin affects the levels of proinflammatory/prothrombotic markers in antiphospholipid syndrome (APS) patients. Vascular endothelial growth factor (VEGF), soluble tissue factor (sTF), tumor necrosis factor-alpha (TNF-alpha), soluble intercellular adhesion molecule-1 (sICAM-1), sE-selectin (E-sel), C-reactive protein (CRP), and soluble vascular cell adhesion molecule (sVCAM-1), were measured in the sera of 93 APS patients and 60 controls and in the sera of nine patients with APS before and after 30 days of treatment with fluvastatin.

Annexin A2 is involved in antiphospholipid antibody-mediated pathogenic effects in vitro and in vivo.

Antiphospholipid (aPL) antibodies recognize receptor-bound beta(2) glycoprotein I (beta(2)GPI) on target cells, and induce an intracellular signaling and a procoagulant/proinflammatory phenotype that leads to thrombosis. Evidence indicates that annexin A2 (A2), a receptor for tissue plasminogen activator and plasminogen, binds beta(2)GPI on target cells. However, whether A2 mediates pathogenic effects of aPL antibodies in vivo is unknown.