beta 2-Glycoprotein I: target antigen for autoantibodies in the 'antiphospholipid syndrome'

Effect and mechanism of the aβ2‑GP I/rhβ2‑GP I complex on JEG‑3 cell proliferation, migration and invasion

Antiphospholipid antibody (aPL)-mediated antiphospholipid syndrome (APS) is an autoimmune disease. Upon binding to aPL, the primary antigen of aPL, β2-glycoprotein I (β2-GP I), induces abnormal immune function, which further activates downstream signaling pathways in the cell and eventually leads to APS. The present study aimed to determine whether β2-GP I antigen and anti-β2-glycoprotein I antibody (aβ2-GP I), which belong to the aPL class of antibodies, may affect human chorionic epithelium cell (JEG-3) proliferation, migration and invasion. Recombinant human (rh)β2-GP I protein was expressed using a prokaryotic expression system and aβ2-GP I antibody was purified from the blood serum of 10 patients with recurrent pregnancy loss. JEG-3 cells were stimulated with rhβ2-GP I and aβ2-GP I separately or simultaneously, and serum immunoglobulin G of normal pregnant women was used as negative control. Using cell counting kit-8, cell cycle and transwell assays in addition to EdU staining, it was determined that aβ2-GP I/rhβ2-GP I complex markedly increased JEG-3 cell proliferation, migration and invasion. The results revealed that mRNA levels of inhibitor of nuclear factor (NF)-κB kinase subunit (IKKβ), myeloid differentiation primary response protein MyD88 (MyD88), NF-κB and NF-κB inhibitor α (IκBα), as well as the protein levels of MyD88, IκBα and phospho(p)-IκBα in JEG-3 cells increased following incubation with the aβ2-GP I/rhβ2-GP I complex. The observed upregulation of p-IκBα protein suggested that IκBα-mediated inhibition of NF-κB was weakened. Furthermore, JEG-3 cells were transfected with PGMLV-NF-κB-Lu vector. Luciferase activity in JEG-3-NFκB-Luc1 and JEG-3-NFκB-Luc2 cells was enhanced following treatment with aβ2-GP I/rhβ2-GP I complex. The present study demonstrated that aβ2-GP I/rhβ2-GP I complex activates NF-κB through MyD88 signal transduction pathway, which further enhances JEG-3 cell proliferation, migration and invasion.

Cardiac papillary fibroelastoma presenting as chorea in childhood

A 5-year-old boy presented with acute onset of chorea and dysarthria. During his workup, a heart murmur was noted. Echocardiography revealed multiple mobile masses in the left ventricular outflow tract related to the mitral valve. Brain magnetic resonance imaging and magnetic resonance angiography did not detect any abnormalities. He underwent a subtotal resection of the mass to preserve valvular function. The anatomic pathology was papillary fibroelastoma.

APS and the brain

Antiphospholipid antibody syndrome (APS) may present with neurological syndromes. Cerebrovascular disease, chorea/ballismus, epileptic seizures, headache, cognitive impairment, transverse myelopathy, Devic's syndrome and multiple sclerosis-like presentations feature among others. Cerebrovascular disease is one of the most common presenting symptoms of APS, second only to deep vein thrombosis, and accounts for half of neurological manifestations in patients with APS; accelerated atherogenesis and cardioembolism are the most likely mechanisms implicated. Though infrequent, chorea is consistently associated with APS; the pathogenetic role of antiphospholipid antibodies (APLab) in this case might be routed through cerebrovascular disease in some cases and through purely immunological pathways in others. Both ischemic and immunological mechanisms have been demonstrated in the pathogenesis of epileptic seizures, which may account for 7% of neurological manifestations in APS. Although frequent in APS, a causative link between APLab and most common types of headache (migraine and tension-type headache) is more than dubious. Cognitive impairment may derive from a well-defined clinical tableau of multi-infarct dementia. Nevertheless, (highly frequent) less severe cognitive impairment has also been associated with the presence of APLab in the absence of magnetic resonance findings. A relationship between APS and transverse myelopathy seems likely but small numbers in the studies published to date preclude definite statements; routinely testing for APLab patients with neurological manifestations suggestive of multiple sclerosis seems to be unrecommended at the present time.

Primary anti-phospholipid antibody syndrome (APS): current concepts

Primary anti-phospholipid syndrome (APS) is a thrombophilic state characterized by recurrent arterial and venous thrombosis, recurrent pregnancy loss, and the presence of circulating anti-phospholipid antibodies that may be responsible for thrombophilia and pregnancy morbidity. Ophthalmologic features are present in 15-88% of the patients with primary APS, thus ophthalmologists are one of the first physicians to whom the patient will present. An accurate diagnosis may save the patient from recurrent, potentially life-threatening thrombosis. In the U.S.A., an estimated 35,000 new cases of APS-related venous thrombosis occur each year in a population that is several decades younger than the patient population typically affected by thrombosis. Clinical features, such as chorea, transverse myelitis, cardiac valvular lesions, and accelerated atherosclerosis, are hypothesized to be due to a direct tissue-antibody interaction and cannot be explained purely by thrombosis. The use of recently proposed, well-defined diagnostic criteria, and better standardization of laboratory assays for the anti-phospholipid antibodies should help enable epidemiological surveys to establish the prevalence of these antibodies in patients with thrombosis and in the general population. Diagnosis of APS should be considered in all patients with recurrent systemic or ocular thrombosis in the absence of known risk factors. Several well-designed prospective studies show an increased risk of thrombosis in the presence of medium to high antibody level. With ocular involvement in as many as 88% of APS patients, an ophthalmic assessment should be an integral part of the clinical work-up of any patient with suspected or confirmed APS. The presence of isolated ocular thrombophilia with persistently elevated anti-phospholipid antibodies or lupus coagulant should confirm the diagnosis of APS. Management of these patients must be a multi-disciplinary effort with either a rheumatologist or a hematologist having the overall responsibility for coordinating treatment and monitoring the patient's immune status and anticoagulation. Treatment of isolated ocular thrombophilia in the presence of moderate to high titers of antiphospholipid antibodies should be on the same principles as patients with APS to prevent recurrent ocular or cerebral thrombosis.

Management of pregnancy in antiphospholipid syndrome

Pregnant women with APS are at high risk of maternal and fetal pregnancy complications. Multidisciplinary teams expert in this condition should coordinate management. Even with current management strategies, the risk of maternal thrombosis, fetal loss, or other adverse obstetric outcomes remains. Close monitoring of the various aspects of this condition may reduce maternal morbidity and improve fetal outcome. The pathogenesis of the adverse pregnancy outcome in APS has not yet been fully elucidated, although active research in this field continues. Until this is ascertained, we must accept that many aspects of management are purely empiric, and it is our duty to counsel patients thoroughly so that they understand the risks and benefits of the treatment options they are offered.

Testing for the antiphospholipid syndrome: importance of IgA anti-beta 2-glycoprotein I

BACKGROUND

Testing for the antiphospholipid syndrome (APS) using anticardiolipin antibodies (aCL) has been problematic. Titers may fluctuate or even become negative. Anti-beta 2-glycoprotein I assays (abeta2-GPI) may be more reliable for diagnosis.

METHODS

In a prospective, blinded study over a nine-month period we retested all patients seen for routine follow-up visits in our clinic who had previously been evaluated for aCL-associated illnesses. Patients were stratified into two groups: group A-patients previously positive for aCL; group B-patients previously negative for aCL. Both groups were further classified according to disease severity. Patients were retested for both aCL and abeta2-GPI (isotypes G, M, A for each) using uniform testing standards.

RESULTS

118 patients with previously positive aCL (group A) were retested. Repeat aCL were positive in 52/118 (44%), abeta2-GPI positive in 69/118 (58%) and 82/118 (69.5%) were positive for one or both assays. In patients with serious organ damage (92% with documented APS), 48.6% were aCL positive, 64% positive for abeta2-GPI, and 75.7% were positive for one or both assays. When only one assay was positive, abeta2-GPI was most frequent (P=0.0096). Overall, IgA abeta2-GPI was the most frequent isotype found (60.9%). On retesting of 73 aCL-negative patients (group B), 9/73 (12%) were aCL positive, 27/73 (36%) were abeta2-GPI positive, with 24/73 (32.9%) having isolated abeta2-GPI. Of those positive for abeta2-GPI, IgA abeta2-GPI was present in 74. 1%. Many of these patients had documented APS.

CONCLUSION

Based on our data, abeta2-GPI assays are superior to aCL assays for diagnosis of APS. The combined use of both assays enhance positive testing results in up to 75% of patients with APS at any stage of illness. ACL negative patients suspected of having APS should be retested for both abeta2-GPI and aCL. IgA abeta2-GPI appears to be the most important isotype detected.

Anti-phospholipid antibodies in patients with multiple sclerosis and MS-like illnesses: MS or APS?

OBJECTIVE

To describe the frequency, clinical, and laboratory features of patients diagnosed with multiple sclerosis (MS) or MS-like illnesses (MSL) among a large, prospectively followed cohort of anti-phospholipid antibody (aPL)-positive patients.

METHODS

Between 1990 and 1995 patients referred to a university-affiliated rheumatology clinic were prospectively evaluated for aPL based on questionnaires designed to detect aPL-related symptoms and/or a family history of aPL-related illnesses. Magnetic resonance imaging (MRI) was performed when significant neurological features were present. A subgroup of all patients diagnosed with MS or MSL was identified and their clinical, laboratory, and imaging findings were reviewed.

RESULTS

Of 322 patients evaluated for aPL-related symptoms or events, 189 (59%) were positive for at least one class of aPL. Twenty-six of 322 patients (8%) carried a diagnosis of MS or MSL, either at the initial evaluation or during the study period. Twenty-three of the 26 individuals (88%) tested positive for aPL, while the remaining 3 (11%) tested repeatedly negative. Eighteen of the 23 patients (78%) had either more than one class of aPL or had multiple positive titers. IgM aCL was noted in 18 of the 23 patients (78%). Oligoclonal bands were noted in five patients. Antinuclear antibodies (ANA) and low complement levels were frequently observed. Blinded MRI readings showed lesions consistent with MS in the majority of cases. Clinically, 7 patients had transverse myelitis (TM), while optic neuritis (ON) was present in 8 patients. Most patients had either occult symptoms of rheumatic disease or contributory family histories. None had a defined underlying connective-tissue disease.

CONCLUSION

A substantial number of aPL-positive patients have a concurrent diagnosis of MS or MSL, frequently presenting with elevated IgM aCL, optic neuritis, and transverse myelitis. The anti-phospholipid syndrome (APS) should be strongly considered as an alternative diagnosis to MS in these patients.

Beta2-glycoprotein I (beta2-GPI) mRNA is expressed by several cell types involved in anti-phospholipid syndrome-related tissue damage

We report here the expression of beta2-GPI mRNA by cell types involved in the pathophysiology of the anti-phospholipid syndrome (APS), i.e. endothelial cells as a target of autoantibodies in the APS, astrocytes and neurones involved in APS of the central nervous system (CNS). Lymphocytes were also included in the study, as it has been demonstrated that patients with systemic lupus erythematosus-associated CNS diseases have serum anti-lymphocyte antibodies cross-reacting with brain antigens, and intrathecally synthesized anti-neurone antibodies. Reverse transcriptase-polymerase chain reaction followed by restriction enzyme digestion of the product obtained demonstrated the presence of beta2-GPI mRNA in all cell types here tested, cultured both in presence and absence of fetal calf serum. In both culture conditions, the same cell types were immunoreactive to an anti-beta2-GPI MoAb, as determined by indirect immunofluorescence technique. Taken together, these results indicate a direct cell synthesis of beta2-GPI, suggesting an antigenic function of beta2-GPI in the APS, including the CNS disease that occurs in this syndrome.

Antiphospholipid antibodies and reproductive outcome: the current state of affairs

Antiphospholipid antibodies were first linked to pregnancy loss more than 20 years ago, and the condition known as antiphospholipid syndrome is perhaps the most convincing 'immunologic' disturbance other than anti-erythrocyte and anti-platelet alloimmunization disorders. Specific criteria for the antiphospholipid syndrome have been delineated, the anticardiolipin assay has been standardized, and authorities agree on laboratory criteria defining lupus anticoagulant. Nonetheless, considerable confusion exists regarding antiphospholipid syndrome and related reproductive problems. The state of affairs primarily derives from two problems: the first is the premature introduction of non-standardized antiphospholipid assays into clinical use without rigorous standardization and prior to convincing proof of clinical utility. As a result, well-intending, but less well-versed clinicians sometimes make the diagnosis of antiphospholipid syndrome in women who are negative for lupus anticoagulant and anticardiolipin antibodies. This is especially confusing in the face of of growing evidence that the relevant in vivo antiphospholipid antigen is formed by a complex between beta 2-glycoprotein 1 and phospholipids. A second major problem is that of unwarranted discrepancies in the clinical and laboratory features of patients considered to have a diagnosis of antiphospholipid syndrome. This problem is most apparent in the case selection for pregnancy-loss treatment series and trials. Many series have included women with predominantly pre-embryonic and embryonic pregnancy losses, while others included a large majority of patients with one or more second or third trimester pregnancy losses. Some treatment trials purposefully excluded patients with a history of thrombosis or systemic lupus erythematosus, features found in nearly 50% of patients in other series. Though most authorities require the presence of either lupus anticoagulant or medium-to-high titer IgG anticardiolipin antibodies to make a diagnosis of antiphospholipid syndrome, in some series no more than half of the study patients had lupus anticoagulant and as many as 20% had only IgM anticardiolipin antibodies. It is very unlikely that patients with such disparate clinical and laboratory findings have the same autoimmune syndrome, and a stated or implicit diagnosis of antiphospholipid syndrome in such a wide variety of women is scientifically unsound and clinically dangerous. The relationship between antiphospholipid antibodies and poor reproductive outcomes must be approached through rigorous scientific study and appropriate treatments established by well-designed clinical trials.