A unique antiphospholipid assay recognizing phospholipid mixture compared with criteria antiphospholipid immunoassays in lupus patients.

Background While essential for the classification of antiphospholipid syndrome (APS), anticardiolipin (aCL) assays lack specificity and anti-ß2glycoproteinI (anti-ß2GPI) assays lack sensitivity in this regard. Our aim was to perform a comparative analysis of the APhL ELISA assay (IgG/IgM) and criteria antiphospholipid (aPL) immunoassays in identifying APS-related clinical manifestations in a large group of patients with systemic lupus erythematosus (SLE). Methods Serum samples from 1178 patients from the Hopkins ( n = 543), LUMINA ( n = 588) and Jamaican SLE cohorts ( n = 47) were examined for IgG/IgM positivity in aCL (in-house), anti-ß2GPI (two commercial kits) and APhL (Louisville APL) ELISA assays. Correlation of assay positivity with clinical manifestations and sensitivity, specificity, positive and negative predictive values and likelihood ratios were evaluated. A case series analysis was also performed in patients for whom there was isolated positivity in the specific aPL assays. Results The prevalence of aCL positivity was 34.9%, anti-ß2GPI kit A was 22.6%, APhL was 11.5% and anti-ß2GPI kit B was 7.6% in the study population. Anti-ß2GPI kit B, aCL and APhL assays were correlated with venous thrombosis, while only APhL was significantly correlated with arterial thrombosis and consistently correlated with pregnancy-related morbidity. No significant correlations were noted for anti-ß2GPI kit A. Sensitivity was greatest for aCL assays followed by anti-ß2GPI kit A, APhL and anti-ß2GPI kit B, while specificity was greatest and equal for anti-ß2GPI kit B and APhL assays. Conclusions Overall, APhL antibodies, especially IgG, represent a promising biomarker for the classification of APS patients in the context of autoimmunity and in risk assessment with regards to pregnancy morbidity and thrombotic manifestations.

'Criteria' aPL tests: report of a task force and preconference workshop at the 13th International Congress on Antiphospholipid Antibodies, Galveston, Texas, April 2010.

Current classification criteria for definite antiphospholipid syndrome (APS) mandate the use of one or more of three positive 'standardized' laboratory assays to detect antiphospholipid antibodies (aPL) (viz: anticardiolipin [aCL] IgG and IgM; anti-ß(2)glycoprotein I [anti-ß(2)GPI] antibodies IgG and IgM; and/or a lupus anticoagulant [LAC]), when at least one of the two major clinical manifestations (thrombosis or pregnancy losses) are present. Although, efforts of standardization for these 'criteria' aPL tests have been conducted over the last 27 years, reports of inconsistencies, inter-assay and inter-laboratory variation in the results of aCL, LAC, and anti-ß(2)GPI, and problems with the interpretation and the clinical value of the tests still exist, which affect the consistency of the diagnosis of APS. A Task Force of scientists and pioneers in the field from different countries, subdivided in three working groups, discussed and analyzed critical questions related to 'criteria' aPL tests in an evidence-based manner, during the 13(th) International Congress on Antiphospholipid Antibodies (APLA 2010, April 13-16, 2010, Galveston, TX). These included: review of the standardization and the need for international consensus protocol for aCL and anti-ß(2)GPI tests; the use of monoclonal and/or polyclonal standards in the calibration curve of those tests; and the need for establishment of international units of measurement for anti-ß(2)GPI tests. The group also reviewed the recently updated guidelines for LAC testing, and analyzed and discussed the possibility of stratification of 'criteria' aPL tests as risk factors for APS, as well as the clinical value of single positive vs. multiple aPL positivity. The group members presented, discussed, analyzed data, updated and re-defined those critical questions at a preconference workshop that was open to congress attendees. This report summarizes the findings, conclusions, and recommendations of this Task Force.

A re-appraisal of the normal cut-off assignment for anticardiolipin IgM tests.

BACKGROUND: Recent reports show an apparent large number of individuals with low to moderate titers of anticardiolipin antibodies (ACA), particularly of the IgM isotype with no clinical signs of antiphospholipid syndrome (APS). The significance of these results is unknown. This study examined the prevalence of low positive titers of IgM ACA antibodies in a large number (n = 982) of normal blood donors (Group 1) and in a group of 159 individuals > 60 years of age (Group 2). The effect of re-defining the currently used cut-off values for the IgM ACA tests was also examined. METHODS: IgM ACA antibodies were tested in three ELISA assays: the Bindazyme Anti-IgM Cardiolipin EIA kit (assay A), an 'in-house' ACA test (assay B), and the APhL ELISA kit (assay C). RESULTS: THE normal range cut-offs were re-calculated using the 95th percentile of the data for Group 1 (12.4 MPL U mL(-1) for assay A, 5.4 MPL U mL(-1) for assay B and 9.5 MPL U mL(-1) for assay C) and Group 2 (9.9 MPL U mL(-1) for assay A, 5.5 MPL U mL(-1) for assay B and 13.2 MPL U mL(-1) for assay C). These values were not significantly different from the current cut-off values for each assay. The prevalence of low positive results in Group 1 relative to the re-defined cut-off for that group were: 1.0%, 1.1% and 0.9% in assay A, B and C; and in Group 2: 0.6%, 0.6% and 0.6%, respectively. An indeterminate zone (between the 95th and 99th percentile) was then established for the two groups. The prevalence in Group 1 was 3.8%, 3.9% and 3.9% for assays A, B and C, respectively, and for Group 2: 4.4% in all three assays. CONCLUSIONS: The data confirm that the current cut-off point for each of the three assays is correct. We suggest based on this study that the low positive range is re-assigned 'indeterminate' and recommend that samples falling in this category should be retested to confirm positivity at a later date.

Thrombogenic effects of antiphospholipid antibodies are mediated by intercellular cell adhesion molecule-1, vascular cell adhesion molecule-1, and P-selectin.

Recent studies have shown that antiphospholipid (aPL) enhances expression of intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and E-selectin on endothelial cells (ECs) and that these effects are correlated with increased adhesion of leukocytes to endothelium in cremaster muscle in vivo and with thrombosis in a mouse model. Activation of ECs by aPL may create a hypercoagulable state that precedes and contributes to thrombosis in patients with aPL syndrome (APS). This study proposed to examine whether this in vivo activation of ECs and enhanced thrombosis by aPL are mediated by ICAM-1, P-selectin, or VCAM-1. The dynamics of thrombus formation and the number of adhering leukocytes were studied in ICAM-1-deficient (ICAM-1(-/-)) mice or ICAM-1-/P-selectin-deficient (ICAM-1(-/-)/P-selectin(-/-)) mice treated with affinity-purified aPL antibodies (ap IgG-APS) or with control IgG and compared with wild-type mice treated in a similar fashion. In another set of experiments, the adhesion of leukocytes to cremaster muscle and the dynamics of thrombus formation were studied in CD1 mice treated with aPL or control IgG before and 30 minutes after intravenous infusion with 100 microg monoclonal antibody anti-VCAM-1. The results indicate that the enhanced adhesion of leukocytes to endothelium in wild-type mice was significantly reduced in ICAM-1(-/-) and completely abrogated in ICAM-1(-/-)/P-selectin(-/-) mice treated with ap IgG-APS compared with wild-type mice treated with ap IgG-APS (6.9+/-2.3, 0.4+/-0.4 versus 35+/-12, respectively). More importantly, this correlated with a significant reduction in thrombus size compared with wild-type mice treated with ap IgG-APS (895+/-259 microm(2), 859+/-243 microm(2) versus 3816+/-672 microm(2), respectively). Infusion of the mice with anti-VCAM-1 antibodies significantly reversed the enhanced adhesion of leukocytes (14.9+/-3 to 11.3+/-2.1) and thrombus size 3830+/-1008 microm(2) versus 876+/-548 microm(2)) in mice treated with ap IgG-APS. The data indicate that ICAM-1, P-selectin, and VCAM-1 expression are important in thrombotic complications by aPL antibodies and may provide novel targets for therapy in patients with APS.

Antiphospholipid antibodies from antiphospholipid syndrome patients activate endothelial cells in vitro and in vivo.

BACKGROUND: Antiphospholipid (aPL) antibodies are associated with thrombosis in patients diagnosed with antiphospholipid syndrome (APS) and enhance thrombus formation in vivo in mice, but the mechanism of thrombosis by aPL is not completely understood. Although aPL antibodies have been shown to inhibit protein C activation and activate endothelial cells (ECs) in vitro, no study has examined whether these antibodies activate ECs in vivo. Therefore, human affinity-purified aPL (ap aPL) antibodies from APS patients were tested in a mouse model of microcirculation using the cremaster muscle that allows direct microscopic examination of thrombus formation and adhesion of white blood cells (WBCs) to ECs as an indication of EC activation in vivo. Adhesion molecule expression on human umbilical vein endothelial cells (HUVECs) after aPL exposure was performed to confirm EC activation in vitro. METHODS AND RESULTS: All 6 ap aPL antibodies significantly increased the expression of VCAM-1 (2.3- to 4.4-fold), with one of the antibodies also increasing the expression of E-selectin (1.6-fold) on HUVECs in vitro. In the in vivo experiments, each ap aPL antibody except for 1 preparation increased WBC sticking (mean number of WBCs ranged from 22.7 to 50.6) compared with control (14.4), which correlated with enhanced thrombus formation (mean thrombus size ranged from 1098 to 6476 versus 594 microm2 for control). CONCLUSIONS: Activation of ECs by aPL antibodies in vivo may create a prothrombotic state on ECs, which may be the first pathophysiological event of thrombosis in APS.

A retrospective review of 61 patients with antiphospholipid syndrome. Analysis of factors influencing recurrent thrombosis.

BACKGROUND: Antiphospholipid syndrome (APS) is a disorder of recurrent venous or arterial thrombosis, pregnancy losses, and thrombocytopenia. Recurrent thrombosis has particularly adverse effects on patients prognosis. The factors that influence recurrence and management techniques that prevent these events remain controversial. To add further insight regarding predisposing factors and the prevention of thrombotic recurrence, 61 well-characterized patients with APS were followed up for a median time of 77 months. METHODS: A retrospective cohort study was conducted in which the following factors were examined to determine their influence on thrombotic recurrence: primary vs secondary syndrome; the presence of hypertension, hyperlipidemia, diabetes, or smoking; patient age, sex, and race; pregnancy and oral contraceptives use; and treatment with warfarin sodium, warfarin plus aspirin, aspirin alone, prednisone, or no treatment. RESULTS: There was no difference between patients with primary and secondary APS with respect to recurrent arterial (55% vs 38%, respectively) or recurrent venous (47% vs 50%, respectively) thrombotic events. In all patients with APS, white race (P = .02) was associated with recurrent arterial events. Venous thrombosis occurred during pregnancy or in the postpartum period in 16 (30%) of 53 women and in 8 women taking oral contraceptives. Recurrent arterial and venous thromboses were significantly decreased with prophylactic warfarin use when compared with prednisone use or no treatment. Recurrences were infrequent in patients with prothrombin ratios of 1.5 to 2.0. CONCLUSIONS: Treatment with warfarin was most effective in preventing recurrent arterial and venous thrombosis. Pregnancy and the use of oral contraceptives or prednisone may also influence recurrence.

Thrombosis, recurrent fetal loss, and thrombocytopenia. Predictive value of the anticardiolipin antibody test.

To determine the predictive value of the IgG anticardiolipin antibody (ACA) test for thrombosis, recurrent fetal loss, and thrombocytopenia, the clinical features of 121 patients with varying antibody levels were studied. When patients were grouped into high-positive, low-positive, and normal groups according to their ACA levels, there were strong statistical correlations with arterial thrombosis, venous thrombosis, fetal loss, thrombocytopenia, and a positive Coombs' test. At levels of 7 SD and above, the test was highly specific (greater than 80%) and predictive (greater than 70%) for thrombosis, thrombocytopenia, and recurrent fetal loss. This study suggests that the IgG ACA test may be a useful predictor for thrombosis, recurrent fetal loss, and thrombocytopenia in patients with autoimmune disorders.

The "primary" antiphospholipid syndrome: major clinical and serological features.

The antiphospholipid syndrome--the association of venous and/or arterial thromboses, often accompanied by thrombocytopenia in the presence of the antiphospholipid antibodies ("lupus anticoagulant" antibodies to cardiolipin)--is seen mainly in patients with systemic lupus erythematosus (SLE) and the closely related "lupus-like" disease, i.e., lupus patients not conforming to the 1982 revised American Rheumatism Association classification for SLE. It is also seen in a group of patients who do not manifest any of the major clinical or serologic features of SLE, the majority of whom do not appear to progress to classical lupus. A multicenter study of 70 of these patients is documented and their major clinical and serologic characteristics examined: They have been characterized as suffering from a "primary" antiphospholipid syndrome and present typically with a history of deep vein thromboses, often accompanied by pulmonary thromboembolism, which in a few is complicated by thromboembolic pulmonary hypertension, arterial occlusions (most commonly strokes), or fetal loss. The events are often recurrent and may be accompanied by hemocytopenias (thrombocytopenia and less frequently Coombs positivity and/or hemolytic anemia). They are often antinuclear antibody-negative and are always negative for antibodies to dsDNA and to ENA, typical serologic features of SLE. There may be a family history of SLE or a familial clotting tendency in a minority. The group of patients presented appears to be closely related, but distinctly separate from SLE.

E-Selectin mediates pathogenic effects of antiphospholipid antibodies.

Antiphospholipid (aPL) antibodies, detected in patients with antiphospholipid syndrome (APS) are associated with thrombosis, pregnancy loss and thrombocytopenia. Studies have shown that aPL are thrombogenic in vivo, but the mechanism(s) involved are not completely understood. Several studies have demonstrated that aPL antibodies activate endothelial cells (ECs) in vitro, as determined by up-regulation of adhesion molecules: E-selectin (E-sel); intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), and in vivo. The objectives of these study were to determine the effects of aPL antibodies on the expression of E-selectin on ECs, on the adhesion of monocytes to ECs and to study the role of E-selectin on aPL antibodies enhanced thrombus formation and activation of ECs in vivo. We demonstrated that the surface expression of E-selectin on HUVEC by ELISA was increased 400-fold when treated with tumor necrosis factor-alpha (TNF-alpha) and 421-fold when treated with aPL antibodies during 4 h. APL antibodies also induced activation of the nuclear factor-kappa B (NF-kappaB). APL antibodies increased significantly the number of adhering leukocytes to ECs in vivo in C57BL/6 J mice when compared to IgG-NHS treated mice. This effect was abrogated in E-selectin-deficient mice. The thrombus size was significantly increased in C57BL/6 J mice treated with aPL antibodies when compared to mice treated with IgG-NHS. This enhancement in thrombus size by aPL antibodies was abrogated in E-selectin-deficient mice treated with aPL antibodies.

Fluvastatin inhibits up-regulation of tissue factor expression by antiphospholipid antibodies on endothelial cells.

BACKGROUND: Mechanisms of thrombosis induced by antiphospholipid (aPL) antibodies include up-regulation of tissue factor (TF) expression on endothelial cells (ECs). Statins have been shown to reduce levels of TF induced by tumor necrosis factor (TNF-alpha) and lipopolysaccharide (LPS) on ECs. In a recent study, fluvastatin inhibited thrombogenic and proinflammatory properties of aPL antibodies in in vivo models. The aim of this study was to determine whether fluvastatin has an effect on aPL-induced expression of TF on ECs. METHODS: IgGs were purified from four patients with APS (IgG-APS) and from control sera (IgG-NHS). Cultured human umbilical vein endothelial cells (HUVEC) were treated with IgG-APS or IgG-NHS or with medium alone or with phorbol myristate acetate (PMA), as a positive control. In some experiments, cells were pretreated with fluvastatin (2.5, 5 or 10 micro m) with and without mevalonate (100 micro m). TF expression on HUVECs was measured by ELISA. RESULTS: PMA and the four IgG-APS preparations increased the expression of TF on EC significantly (4.9-, 2.4-, 4.2-, 3.5- and 3.1-fold, respectively), in a dose-dependent fashion. Fluvastatin (10 micro m) inhibited the effects of PMA and the four IgG-APS on TF expression by 70, 47, 65, 22 and 68%, respectively, and this effect was dose-dependent. Mevalonate (100 micro m) completely abrogated the inhibitory effects of fluvastatin on TF expression induced by aPL. CONCLUSION: Because of the suggested pathogenic role of aPL on induction of TF on ECs, our data provide a rationale for using statins as a therapeutic tool in treatment of thrombosis in APS.

The prevalence and clinical associations of anticardiolipin antibodies in a large inception cohort of patients with connective tissue diseases.

PURPOSE: To determine the prevalence and clinical associations of anticardiolipin antibodies (aCL) in a blinded, controlled study of patients with a variety of connective tissue diseases (CTD) using a standardized aCL testing system. PATIENTS AND METHODS: Anticardiolipin antibodies (IgG, IgM, and IgA) were measured by direct enzyme-linked immunosorbent assay (ELISA) in the baseline serum samples of patients enrolled in a Cooperative Study of Systematic Rheumatic Diseases (CSSRD), National Institutes of Health (NIH) supported, 5-year inception-cohort, prospective study of early rheumatic diseases: rheumatoid arthritis (RA, n = 70), systemic lupus erythematosus (SLE, n = 70), scleroderma (PSS, n = 45), myositis (PM/DM, n = 36), and early undifferentiated connective tissue disease (EUCTD, n = 165). Diagnosis was based on standardized criteria and determined at the last study visit. A nested group of patients with Sjögren's syndrome (SJ, n = 44) was also defined. Serum from 200 blood donors (BB) served as controls. Additional patients with known antiphospholipid syndrome (APS, n = 33) and ANCA-related renal vasculitis (ANCA, n = 52) were also studied. Laboratory personnel were blinded to sample diagnostic group. RESULTS: The prevalence of either IgG or IgM aCL among each diagnostic group was RA 15.7%, SLE 15.76%, PSS 6.7%, PM/DM 8.3%, EUCTD 9.1%, SJ 6.8%, ANCA 3.8%, and BB controls 4.0%. Prevalence of aCL was significantly different for both the RA and SLE groups versus BB controls (P < 0.01) but not among other diagnostic groups. Only 2 study patients had positive tests for IgA aCL (1 with PM/DM and 1 with EUCTD) versus 15% of APS with positive IgA aCL. Study patients positive for IgG or IgM aCL were significantly more likely to have hemolytic anemia or a positive serologic test for syphilis and less likely to have Raynaud's phenomenon. However, no associations were found between aCL positivity and thrombocytopenia, seizures, renal insufficiency, presence of a positive antinuclear antibody or rheumatoid factor, subcutaneous nodules or digital ulcers. CONCLUSIONS: Based on results from this large CSSRD inception cohort, anticardiolipin antibodies are present in approximately 16% of patients with RA or SLE but are less common in patients with PSS, PM/DM, EUCTD, SJ, and ANCA vasculitis, where their prevalence approaches that in the normal population. Few consistent clinical association can be found among patients with CTD who are aCL positive. The complete diagnostic and prognostic importance and specificity of these antibodies remains to be fully determined.

Early and late endosomal compartments of Entamoeba histolytica are enriched in cysteine proteases, acid phosphatase and several Ras-related Rab GTPases.

Pure populations of early and late endosomes of Entamoeba histolytica were isolated by magnetic fractionation and characterized. It was shown that these vesicles were enriched in acid phosphatase and cysteine protease activities. An important virulence factor, a 27-kDa cysteine protease, was also enriched in early and late endosomes of E. histolytica. These data suggest that E. histolytica hydrolases reside in compartments that are part of or communicate with the endosomal pathway. To begin to identify the role of Rab GTPases in E. histolytica, an oligonucleotide approach was employed to screen an E. histolytica cDNA library for genes encoding Rab-like proteins. cDNAs encoding a Rab11-like protein (EhRab11) and a novel Rab protein (EhRabA) were isolated and characterized. The EhRab11 cDNA predicts a polypeptide of at least 206 amino acids with a molecular mass of at least 23.2 kDa. Phylogenetic analysis and alignment of EhRab11 with other Rab proteins demonstrated that EhRab11 shared significant homology at the amino acid level with Rab11-like proteins from a number of other eukaryotes, suggesting that EhRab11 is a Rab11 homolog for E. histolytica. The EhRabA clone predicts a polypeptide of 219 amino acids with a molecular mass of at least 24.5 kDa. EhRabA shared only limited homology at the amino acid level with other Rab proteins, suggesting that it is a novel member of this family of GTP-binding proteins. Finally, Western blot analysis demonstrated that EhRab11 and a previously described Rab7-like GTPase from E. histolytica was enriched in magnetically purified endosomal compartments of this organism.

Comparison of the effects of anticardiolipin antibodies from patients with the antiphospholipid syndrome and with syphilis on platelet activation and aggregation.

Anticardiolipin antibodies (aCL) are induced both in the Antiphospholipid Syndrome (APS) and syphilis, but thrombosis, thrombocytopenia, and pregnancy loss occur only in the APS. Differences in specificity and function of aCL antibodies might explain clinical differences between APS and syphilis. This study compared the effects on platelet activation and aggregation of affinity purified IgG anticardiolipin antibodies from 6 patients with the APS (IgG-APS) and 5 patients with syphilis (IgG-syph). Platelet aggregation was studied by aggregometry and platelet activation by flow cytometry. In the presence of low concentrations of thrombin, ADP, or collagen, all 6 IgG-APS samples induced platelet aggregation and activation, but none of the IgG-syph samples had this effect. In the absence of platelet agonists, only 3 of 6 IgG-APS caused platelet aggregation and none caused platelet activation; IgG-syph had no effect. The IgG-APS samples but not IgG-syph bound phosphatidylserine by ELISA. We conclude that polyclonal antibodies specific for phosphatidylserine may induce platelet activation and aggregation in the presence of low concentrations of platelet agonists.

Induction of thrombosis in a mouse model by IgG, IgM and IgA immunoglobulins from patients with the antiphospholipid syndrome.

Antiphospholipid syndrome is a disorder of recurrent thrombosis and pregnancy losses associated with production of anticardiolipin antibodies and lupus anticoagulant positivity. Recently, we have adapted a mouse model of induced venous thrombosis to study the role of autoantibodies in thrombus formation. To determine whether immunoglobulins from patients with the antiphospholipid syndrome play a role in thrombosis, we injected groups of CDI mice either with immunoglobulins purified from seven patients with the antiphospholipid syndrome (nine preparations studied: four IgG, three IgM and two IgA) or with immunoglobulins of the same isotype from healthy controls. Seventy-two h after injection, a non-occlusive thrombus was induced in the femoral veins of experimental mice by a pinch injury; the thrombus areas as well as times of formation and disappearance of the thrombi were measured. Eight of the nine antiphospholipid syndrome immunoglobulin preparations caused a significant increase in mean thrombus area and a significant delay in mean thrombus disappearance time as compared with normal controls. To determine whether anticardiolipin antibodies might be involved, separate groups of mice were injected with affinity-purified IgG (n = 2) or IgM (n = 2) anticardiolipin antibodies or with normal immunoglobulins of the same isotype, and the effects on thrombus formation compared. Mean thrombus area and mean disappearance times were again significantly increased in all four groups injected with affinity-purified antibodies. This is the first study to show that anticardiolipin antibodies of IgG, IgM and IgA isotypes may play a role in thrombosis in vivo.

Comparison of test methods for the lupus anticoagulant: international survey on lupus anticoagulants-I (ISLA-1).

Six lyophilized plasma samples were sent to 20 "expert" laboratories for assessment of lupus anticoagulant (LA). Four samples contained pooled LA of graded potency mixed with aged normal plasma. One contained LA plus cephalin phospholipid and one contained a nonspecific venom anticoagulant. Sixteen methods were used overall with some participants using up to 8 methods. Results were scored in regard to the known potencies of LA in the samples and other known induced defects. Activated partial thromboplastin time (APTT) tests used by most participants for preliminary screening were relatively sensitive, but non-specific. Platelet or phospholipid neutralization procedures (PNP) appeared to be sensitive and specific but showed a non-linear response to increased LA content. Kaolin clotting time (KCT) tests showed the most sensitive response to increased LA content but the weaker LA were not scored as abnormal by most laboratories as the samples may have contained platelet fragments. Other commonly used tests such as the tissue thromboplastin inhibition (TTI) test and the dilute Russell's viper venom test (DRVVT) were carried out somewhat inconsistently. The variability in performance of tests in different laboratories indicates that standardization of methodology is urgently required. Generally it seemed that most clotting tests were "bypassed" by the addition of phospholipid to a known LA-positive sample in apparently direct proportion to their sensitivity. Sample preparation, especially prevention of contamination with activated platelets is a vital preliminary part in the assay of LA.

Effect of human IgG antiphospholipid antibodies on an in vivo thrombosis model in mice.

High levels of IgG antiphospholipid antibodies (aPL) have been associated with clinical thrombosis. It is uncertain however whether these antibodies play a direct role in thrombosis or are merely epiphenomena. To investigate whether antiphospholipid antibodies might play a role in thrombosis, we utilized a novel mouse model in which the dynamics of in vivo thrombosis can be studied. CD1 mice (26-30 g) were passively immunized with 25 mg of human IgG from a patient with the Antiphospholipid Syndrome (IgG-APS) (n = 17), IgG from normal pooled sera (IgG-NHS) (n = 9), or saline solution (n = 12), followed by 40 mg of the same preparations at 48 h. At 72 h, levels of human aPL antibodies, detected using the anticardiolipin ELISA test (aCL ELISA test), in mice immunized with IgG-APS, were 50-100 GPL units. Each animal was anesthetized, femoral vein minimally mobilized and subjected to a standardized "pinch" injury to induce thrombosis. The vessel was transilluminated using acrylic optical fibers connected to a light source, and clot formation and dissolution were visualized by a standard surgical microscope equipped with a video camera, video recorder, and computer assisted analysis system. Results showed that average clot size was significantly larger in mice immunized with IgG-APS compared to those treated with saline (p < 0.037). In addition, the thrombus persisted longer in a significantly higher number of mice immunized with IgG-APS (10/17) compared to mice immunized with IgG-NHS (1/9) or saline (2/12) (p < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Chorea in systemic lupus erythematosus and "lupus-like" disease: association with antiphospholipid antibodies.

Twelve patients with chorea from a population of 500 patients with SLE and "lupus-like" disease were reviewed. Clinical histories, including time relationships of chorea to the systemic illness and other neurologic manifestations, are reported. Chorea appeared early in the course of disease in most patients, but the development of cerebral infarctions or TIAs occurred subsequently in seven of nine patients demonstrating antiphospholipid antibodies. The relationship of chorea to the presence of these antibodies in nine of 12 patients and the therapeutic outcome are briefly discussed.

Special report. The Second International Anti-cardiolipin Standardization Workshop/the Kingston Anti-Phospholipid Antibody Study (KAPS) group.

Forty-three laboratories in 13 countries participated in a workshop to determine the degree of agreement between laboratories performing anticardiolipin tests. Each laboratory received freeze-dried aliquots of three samples labeled G1 (107 GPL units), G2 (20 GPL units), and G3 (6 GPL units) to be used as reference standards in the IgG assay, and three samples labeled M1 (106 MPL units), M2 (21 MPL units), and M3 (5 MPL units) as references for the IgM assay. Participating laboratories were divided into 8 groups and serum samples were exchanged between laboratories in each group. For IgG anticardiolipin, results were reported as: high, IgG positive for samples with optical absorbance readings exceeding G1; medium, IgG positive for samples with readings between G1 and G2; low, IgG positive between G2 and G3, and negative, if less than G3. In like manner, samples were defined as high-, medium-, or low-IgM positive, with reference to standards M1, M2, and M3. An index of agreement was computed to determine the degree of agreement between laboratories in each group. Interlaboratory agreement was excellent in each category assessed. For high positive and negative IgG and IgM results, the index of agreement exceeded 90%, and for medium and low positive results, agreement exceeded 75%. The overall index of agreement between laboratories exceeded 90%. The researchers conclude that the use of these six standards to obtain a semiquantitative measure of anticardiolipin positivity will enable good interlaboratory agreement in reporting anticardiolipin results.

Anticardiolipin wet workshop report. Fifth International Symposium on antiphospholipid antibodies.

An anticardiolipin wet workshop was conducted at the Fifth International Antiphospholipid Symposium (San Antonio, Texas, September 9-12, 1992). The workshop had four objectives: 1. to determine variability in measurement of immunoglobulin (Ig) G, IgM, and IgA anticardiolipin of eight unknown sera; 2. to examine the correlation between three commercial enzyme-linked immunosorbent assay (ELISA) kits and the Antiphospholipid Standardization Laboratory; 3. to examine protocols by which anticardiolipin binding to phospholipid antigens and beta 2 glycoprotein 1 (beta 2GP1) might be compared; and 4. to examine the beta 2GP1 effect on cardiolipin binding activity. Results showed good overall correlation of quantitative anticardiolipin measurements between workshop participants and the Antiphospholipid Standardization Laboratory. Correlation with individual ELISA kits was also good. With respect to the third objective, all participants showed comparable binding to cardiolipin and phosphatidylserine but none to phosphatidylcholine or beta 2GP1. Finally, beta 2GP1 enhanced, but was not essential for, anticardiolipin binding. This workshop will not settle controversies about anticardiolipin measurement and specificity, but suggests protocols to resolve these issues.

Origin of antiphospholipid antibodies.

Our observations and those from others give further support to our hypothesis that "autoimmune aPL" may be generated by immunization with products from bacteria or viruses after incidental exposure or infection. We also were able to generate an APS-like syndrome in a strain of mice susceptible to autoimmunity, indicating that other factors such as genetic factors are likely to be involved in development of APS. Furthermore, not all aPL generated by immunization with bacterial or viral products were pathogenic. Based on the clinical experience and on the numerous reports indicating the presence of aPL in large number of infectious diseases, it may be expected that not all aPL produced during infection are pathogenic. We hypothesize that a limited number aPL induced by certain viral or bacterial products would be pathogenic in certain groups of predisposed individuals. Identification of those bacterial or viral agents may help to find strategies for the prevention of production of "pathogenic" aPL. Alternatively, free peptides may be used to induce tolerance against aPL production.