Antiphospholipid antibodies affect trophoblast gonadotropin secretion and invasiveness by binding directly and through adhered beta2-glycoprotein I

OBJECTIVE

To investigate the in vitro ability of antiphospholipid antibodies (aPL) to bind human trophoblast cells and to affect gonadotropin secretion and invasiveness.

METHODS

Antiphospholipid antibody IgG from women with recurrent miscarriages, beta2-glycoprotein I (beta2GPI)-independent IgG aPL human monoclonal antibody (mAb) (519), and IgM anti-beta2GPI human mAb (TMIG2) were investigated for their binding to trophoblasts cultured for various amounts of time, their ability to affect invasiveness of Matrigel-coated filters, and their release of human chorionic gonadotropin (hCG).

RESULTS

Polyclonal IgG aPL, as well as mAb 519 and TMIG2, bound to trophoblasts, the highest binding being found when cells displayed the greatest amount of syncytium formation. TM1G2 binding was found to be betaGPI dependent. Both polyclonal and monoclonal aPL, but not the controls, significantly reduced hCG release and Matrigel invasiveness.

CONCLUSION

These findings suggest that aPL recognition of both anionic PL and adhered beta2GPI on trophoblast cell structures might represent a potential pathogenetic mechanism for defective placentation in women with the antiphospholipid syndrome.

Induction of apoptosis by flavones, flavonols (3-hydroxyflavones) and isoprenoid-substituted flavonoids in human oral tumor cell lines

Various flavones, flavonols (3-hydroxyflavones) and isoprenoid-substituted flavones (flavonols) were investigated for their cytotoxic activity. Most of these compounds were more cytotoxic against human oral squamous cell carcinoma and salivary gland tumor cell lines than human gingival fibroblasts. The cytotoxic activity of flavonoids was generally higher than that of tannin-related compounds. Flavonoids induced apoptotic cell death characterized by DNA fragmentation (as identified by TUNEL method) and activation of caspase(s) (as identified by degradation products of cytokeratin 18 with M30 monoclonal antibody). ESR spectroscopy revealed that higher concentrations of flavonoids produced radicals under alkaline conditions. However, not all of them enhanced the radical intensity of sodium ascorbate, suggesting that the redox potential of flavonoids differs considerably from samples to samples. Catalase failed to eliminate the cytotoxic activity of flavonoids, reducing the possibility of the involvement of hydrogen peroxide for the cytotoxicity induction by them.

Posterior rotational osteotomy for the treatment of femoral head osteonecrosis

Posterior rotational osteotomy in 46 hips of 39 patients with femoral head osteonecrosis was reviewed radiographically and clinically after 2-12 years of follow-up (mean 5 years). The age of the patients at the time of surgery ranged from 18 to 60 years, with a mean of 35 years. There were 18 women and 21 men. The cause of the osteonecrosis was steroid administration in 14, alcohol abuse in 5, trauma in 16, and no apparent risk factor in 4. According to the Ficat staging system, 2 hips were stage II, 30 hips III, and 14 hips stage IV. All hips had an extensive lesion. Forty-one hips showed less than 1/3 noncollapsed posterior living area, which was a contraindication for traditional anterior rotational osteotomy. The posterior rotational angle was 60-180 deg with an mean of 127 deg. Recollapse of the final follow-up anteroposterior radiograph was prevented in 36 hips (78%). Progressive joint space narrowing was found in 12 hips (26%). Of these hips, 9 suffered recollapse, while the remaining 3 hips did not. Clinically, 32 hips (70%) showed excellent or good results (both hips in stage II, 23 of 30 hips in stage III, 7 of 14 hips in stage IV. A fair or poor result was seen in 14 hips (30%)). These results suggest that posterior rotational osteotomy is effective in delaying the progression of degeneration for large necrotic lesions, especially in young patients. Extent of rotation is limited to 150 deg because of limitations of bone quality. The indications should be refined further, and longer term follow-up is necessary.

Autoantibodies against malondialdehyde-modified lipoprotein(a) in antiphospholipid syndrome

OBJECTIVE

To demonstrate the existence of antibodies that react against malondialdehyde (MDA)-modified lipoprotein(a) (MDA-Lp[a]), a molecule that exhibits behavioral similarities to MDA-modified low-density lipoprotein (MDA-LDL), and to assess the possible relationship of these antibodies (anti-MDA-Lp[a]) to anti-MDA-LDL antibodies (anti-MDA-LDL) in the antiphospholipid syndrome (APS).

METHODS

We studied 104 patients with APS (61 with primary APS and 43 with APS secondary to systemic lupus erythematosus) and 106 healthy controls. Anti-MDA-Lp(a) were measured by enzyme-linked immunosorbent assay (ELISA) using MDA-Lp(a) as antigen. Plasma levels of Lp(a) were determined. Anti-MDA-LDL, anticardiolipin antibodies (aCL), and anti-beta2-glycoprotein I antibodies (anti-beta2GPI) were also measured by ELISA. Inhibition assays were performed to determine the presence of cross-reactivity between anti-MDA-Lp(a) and anti-MDA-LDL.

RESULTS

Anti-MDA-Lp(a) were detected in 38 of 104 patients (37%) but in only 6 of 106 controls (6%) (chi2 = 28, P<0.0001). Levels of anti-MDA-Lp(a) were also higher in patients than in controls (P<0.0001). Titers of these antibodies did not correlate with plasma levels of Lp(a). The presence of anti-MDA-Lp(a) was significantly associated with that of anti-MDA-LDL (chi2 = 22.09, P<0.0001). There was a strong correlation between the titers of anti-MDA-Lp(a) and anti-MDA-LDL (r = 0.59, P<0.0001), and inhibition assays showed significant cross-reactivity between the 2 populations of antibodies. Anticardiolipin antibodies and anti-beta2GPI were present in sera from 67 patients (64%) and 48 patients (46%), respectively. No correlation was found between the titer of anti-MDA-Lp(a) and titers of either aCL or anti-beta2GPI.

CONCLUSION

We report for the first time the existence of autoantibodies against MDA-Lp(a). The presence of antibodies reacting not only against MDA-LDL but also against MDA-Lp(a) supports the hypothesis of a role for oxidative phenomena in the pathogenesis of APS and atherosclerosis.

A chimeric antibody with the human gamma1 constant region as a putative standard for assays to detect IgG beta2-glycoprotein I-dependent anticardiolipin and anti-beta2-glycoprotein I antibodies

OBJECTIVE

Thromboembolic manifestations or thrombocytopenia in association with anticardiolipin antibodies (aCL) or lupus anticoagulant are known as the antiphospholipid syndrome (APS). Efforts have been made to elucidate precise clinical features and adequate therapeutic options for treating patients with APS. However, the lack of a proper international standard for measurement of aCL makes it difficult to compare data derived from different laboratories. We attempted to design a chimeric antibody with human gamma constant regions and variable regions of WBCAL-1, a monoclonal antibody established from an APS-prone mouse which has a specificity similar to that of aCL in sera from humans with APS.

METHODS

Variable-region genes of WBCAL-1, which were cloned using reverse transcription-polymerase chain reaction, were inserted into plasmids containing human gamma1 and kappa constant-region genes. The construct was transfected to a mouse myeloma cell line. Stable transfectants that secreted a chimeric antibody, HCAL, into the culture supernatant were obtained. The reactivity of HCAL to cardiolipin and to beta2-glycoprotein I (beta2GPI) was studied using a solid-phase enzyme immunoassay. The binding of HCAL was compared with the binding of standards for IgG aCL and anti-beta2GPI antibody assays done in 18 independent laboratories.

RESULTS

In the presence of beta2GPI, HCAL bound to the wells of cardiolipin-coated microtiter plates in a dose-dependent manner and reacted with beta2GPI on oxygenated polystyrene plates. The aCL activity of HCAL can be converted into GPL units (IgG phospholipid units), which is widely used to quantify IgG aCL activity, using the following formula: 1 GPL unit = 32.9 x (concentration of HCAL [in microg/ml])(0.503). The reactivity of HCAL to cardiolipin or beta2GPI was similar to the reactivity of standards for IgG aCL or anti-beta2GPI antibody assays done in collaborative laboratories.

CONCLUSION

Because the reactivity of HCAL is similar to that of aCL in sera from humans with APS, HCAL will be useful as a standard for human IgG aCL and anti-beta2GPI antibody assays.

Reflex sympathetic dystrophy in a patient with the antiphospholipid syndrome

We describe a 50-year-old woman who developed severe pain of the left lower limb after an episode of thrombophlebitis. Bone scintigraphy and thermography showed results indicative of reflex sympathetic dystrophy. Laboratory analysis revealed the presence of the lupus anticoagulant. The patient was diagnosed as antiphospholipid syndrome complicated with reflex sympathetic dystrophy of the left lower limb. To our knowledge, this is the first report of a patient with reflex sympathetic dystrophy with underlying antiphospholipid syndrome.

Radical intensity and cytotoxicity of butylated hydroxyanisole and its orthobisphenol dimer

The radical intensity of BHA (4-Hydroxy-3-t-butylanisole) and its dimer (3,3'-Di-t-butyl-5,5'-dimethoxy-1,1'-biphenyl-2,2'-diol, Bis-BHA) were compared with their cytotoxic activity. ESR spectroscopy showed that BHA produced characteristic five peaks of radicals under alkaline conditions (pH > 9.5). At higher pH, BHA radical rapidly disappeared, and progressively transformed into new radical species, as detected by the splitting of the ESR signal. BHA showed higher cytotoxic activity against salivary gland tumor cell line than against normal human gingival fibroblast. On the other hand, Bis-BHA did not produce any detectable amounts of radicals at wide ranges of pH, corresponding with its weaker cytotoxic activity as compared with BHA. BHA scavenged DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical and superoxide anion, more efficiently than Bis-BHA. The present study demonstrated that BHA is more cytotoxic, produces higher amounts of radicals and more efficiently scavenges various radical species, as compared with Bis-BHA. This suggests the possible link between the cytotoxic activity and radical generation/scavenging activity in BHA-derived compounds.

Correlation between beta2-glycoprotein I valine/leucine247 polymorphism and anti-beta2-glycoprotein I antibodies in patients with primary antiphospholipid syndrome

OBJECTIVES

Beta2-Glycoprotein I (beta2GPI) exon 7 polymorphism leads to a valine leucine amino acid exchange at position 247 in domain 5 of beta2GPI, between the phospholipid binding site and the cryptic site of the epitopes for anti-beta2GPI antibodies. Therefore, position 247 polymorphism may affect the conformational change of beta2GPI and the exposure of the epitopes for anticardiolipin antibodies (aCL) (= anti-beta2GPI antibodies). In this study we analysed the genetic polymorphism of beta2GPI in a British cohort of well-defined antiphospholipid syndrome (APS) patients.

METHODS

This study comprised 88 Caucasoid patients with APS [57 with primary APS and 31 with APS secondary to systemic lupus erythematosus (SLE)]. Polymorphism assignment was determined by polymerase chain reaction followed by allele-specific restriction enzyme digestion (PCR-RFLP). The presence of anti-beta2GPI antibodies was detected by ELISA utilizing irradiated ELISA plates.

RESULTS AND CONCLUSIONS

Anti-beta2GPI antibodies were present in 28 of 57 primary APS patients (49%) and in 19 of 31 secondary APS patients (61%). The allele containing valine247 was significantly more frequent in primary APS patients with anti-beta2GPI antibodies than in controls (OR = 2.51, 95%, CI 1.03-6.13, P = 0.0396) or in primary APS patients without anti-beta2GPI antibodies (OR = 2.92, 95% CI 1.16-7.39, P = 0.0204). This tendency was not found in the secondary APS group. In conclusion, the beta2GPI polymorphism, valine/leucine247, is correlated with anti-beta2GPI antibody production in patients with primary APS, and valine247 may be important in the formation of beta2GPI antigenicity.

[A case of Bickerstaff's brainstem encephalitis which started with Wallenberg's syndrome]

A 54-year-old female developed dysarthria, left limb ataxia, and crossed dissociated sensory impairment, followed by external ophthalmoplegia, severe bulbar palsy and bilateral pyramidal tract involvement. A high titer of anti-GQ1b IgG antibody was detected in her serum. Brain MRI (T2 weighted image, diffusion weighted image) and peripheral nerve conduction study were normal. We diagnosed her as having Bickerstaff's brainstem encephalitis. In the past literature, we could not find any case of Bickerstaff's brainstem encephalitis showing crossed dissociated sensory impairment.

Application of bis-eugenol to a zinc oxide eugenol cement

OBJECTIVES

To assess the usefulness of dimerized eugenol (bis-eugenol) in dentistry, the physical properties of zinc oxide eugenol cement (ZOE) with bis-eugenol and the cytotoxicity of bis-eugenol were studied.

METHODS

Setting time, compressive strength, solubility and disintegration of ZOE cement with bis-eugenol according to the specifications of JDMAS315 were evaluated. The cytotoxicity of bis-eugenol and eugenol toward two different cell types, HGF (a primary culture of human gingival fibroblast) and HSG (a human epidermoid carcinoma cell line derived from a salivary gland) was evaluated by the MTT test and in terms of cell survival.

RESULTS

Addition of bis-eugenol to ZOE did not decrease the physical properties when employed at the ratio of 9:1 or 6:1 (liquid ND:bis-eugenol, w/w). Bis-eugenol was less toxic than eugenol in the cell culture tests.

CONCLUSIONS

The results of this assay demonstrated that bis-eugenol is useful in ZOE.

Suppression of transforming growth factor beta and vascular endothelial growth factor in diabetic nephropathy in rats by a novel advanced glycation end product inhibitor, OPB-9195

AIMS/HYPOTHESIS

Advanced glycation end products (AGEs) participate in the pathogenesis of diabetic nephropathy. We reported earlier that OPB-9195, a synthetic thiazolidine derivative and novel inhibitor of advanced glycation, prevented progression of diabetic glomerulosclerosis by lowering serum concentrations of advanced glycation end products and reducing their deposition in the glomeruli. Here, we examined their contribution and that of growth factors, such as transforming growth factor-beta (TGF-beta) and vascular endothelial growth factor (VEGF), to the progression of diabetic nephropathy. We also investigated the expression of type IV collagen in the kidneys of Otsuka-Long-Evans-Tokushima-Fatty (OLETF) rats, a Type II (non-insulin-dependent) diabetes mellitus model, after treatment with OPB-9195.

METHODS

Using northern blots and immunohistochemical techniques, we determined the renal expression of TGF-beta and type IV collagen mRNAs and proteins in OLETF rats. We also examined OPB-9195's effects on renal expression of VEGF mRNA and protein.

RESULTS

Concomitant increases in TGF-beta and type IV collagen expression were observed at each point in time in OLETF rats not given OPB-9195. In contrast, OPB-9195 treatment greatly suppressed the renal expression of TGF-beta, VEGF and type IV collagen mRNAs and proteins to that seen in non-diabetic rats.

CONCLUSION/INTERPRETATION

Since OPB-9195, an AGE-inhibitor, prevented the progression of diabetic nephropathy by blocking type IV collagen production and suppressing overproduction of two growth factors, TGF-beta and VEGF, in diabetic rats, this compound warrants further investigation.

Gab-family adapter proteins act downstream of cytokine and growth factor receptors and T- and B-cell antigen receptors

We previously found that the adapter protein Gab1 (110 kD) is tyrosine-phosphorylated and forms a complex with SHP-2 and PI-3 kinase upon stimulation through either the interleukin-3 receptor (IL-3R) or gp130, the common receptor subunit of IL-6-family cytokines. In this report, we identified another adapter molecule (100 kD) interacting with SHP-2 and PI-3 kinase in response to various stimuli. The molecule displays striking homology to Gab1 at the amino acid level; thus, we named it Gab2. It contains a PH domain, proline-rich sequences, and tyrosine residues that bind to SH2 domains when they are phosphorylated. Gab1 is phosphorylated on tyrosine upon stimulation through the thrombopoietin receptor (TPOR), stem cell factor receptor (SCFR), and T-cell and B-cell antigen receptors (TCR and BCR, respectively), in addition to IL-3R and gp130. Tyrosine phosphorylation of Gab2 was induced by stimulation through gp130, IL-2R, IL-3R, TPOR, SCFR, and TCR. Gab1 and Gab2 were shown to be substrates for SHP-2 in vitro. Overexpression of Gab2 enhanced the gp130 or Src-related kinases-mediated ERK2 activation as that of Gab1 did. These data indicate that Gab-family molecules act as adapters for transmitting various signals.

Risk of thrombosis in patients with antiphospholipid antibodies and factor V Leiden mutation

OBJECTIVE

Antiphospholipid antibodies (aPL) are thrombophilic risk markers in patients with systemic lupus erythematosus (SLE) or primary antiphospholipid syndrome (APS). The risk factors for recurrent venous or arterial thrombosis and indications for longterm anticoagulation therapy are debated. We hypothesized that carrying a second thrombophilic defect, factor V Leiden mutation, would increase the risk for thrombosis in patients with aPL.

METHODS

Seventy-five patients with primary APS and 83 with SLE and aPL with or without thrombosis followed at 2 university hospitals were studied. Factor V mutation rate was analyzed in patients and in 200 healthy blood donors by polymerase chain reaction analysis.

RESULTS

The prevalence of factor V Leiden mutation in patients with SLE and aPL or primary APS was similar to controls. Patients with deep vein thrombosis or arterial thrombosis did not have a significantly increased rate of factor V mutation compared to controls or to patients with aPL without thrombosis.

CONCLUSION

Factor V Leiden mutation is not significantly associated with vein thrombosis in patients with aPL. However, due to the sample size we cannot rule out synergy between both factor V Leiden and aPL. A trend toward increased risk for thrombosis was detected in patients with the mutation and this should be analyzed in a larger study.

Self-renewal and differentiation of a basic fibroblast growth factor-dependent multipotent hematopoietic cell line derived from embryonic stem cells

Despite the accumulation of informat on on the origin of hematopoietic stem cells, it is still unclear how these cells are generated in ontogeny. Isolation of cell lines equivalent to early embryonic hematopoietic progenitor cells can be helpful. A multipotent hematopoietic progenitor cell line, A-6, was isolated from H-1 embryonic stem (ES) cells. The self-renewal of A-6 cells was supported by basic-fibroblast growth factor (b-FGF) and their differentiation into definitive erythroid cells, granulocytes and macrophages was induced after co-culture with ST-2 stromal cells. A-6 cells were positive for the surface markers of hematopoietic stem cell, c-kit, CD31, CD34, Flt3/Flk2, PgP-1, and HSA, but were negative for that of the differentiated cells. Reverse transcription-polymerase chain reaction analysis showed that A-6 cells produced mRNA from SCL/tal-1 and GATA-2 genes. Among various cytokines examined, on y stem cell factor (SCF) and Flt3/Flk2 ligand (FL) supported the proliferation of A-6 cells instead of b-FGF. The FL, as well as b-FGF, supported the self-renewal of A-6 cells, whereas SCF induced differentiation into myeloid cells. A-6 cells will be useful for the characterization of hematopoietic progenitor cells derived from ES cells and provide a model system to realize the control mechanisms between self-renewal and different ation of hematopoietic stem cells.

Na+-driven flagellar motor resistant to phenamil, an amiloride analog, caused by mutations in putative channel components

The rotation of the Na+-driven flagellar motor is specifically and strongly inhibited by phenamil, an amiloride analog. Here, we provide the first evidence that phenamil interacts directly with the Na+-channel components (PomA and PomB) of the motor. The alterations in Mpar (motility resistant to phenamil) strains were mapped to the pomA and/or pomB genes. We cloned and sequenced pomA and pomB from two Mpar strains, NMB205 and NMB201, and found a substitution in pomA (Asp148 to Tyr; NMB205) and in pomB (Pro16 to Ser; NMB201). Both residues are predicted to be near the cytoplasmic ends of the putative transmembrane segments. Mutational analyses at PomA-Asp148 and PomB-Pro16 suggest that a certain structural change around these residues affects the sensitivity of the motor to phenamil. Co-expression of the PomA D148Y and PomB P16S proteins resulted in an Mpar phenotype which seemed to be less sensitive to phenamil than either of the single mutants, although motility was more severely impaired in the absence of inhibitors. These results support the idea that PomA and PomB interact with each other and suggest that multiple residues, including Asp148 of PomA and Pro16 of PomB, constitute a high-affinity phenamil-binding site at the inner face of the PomA/PomB channel complex.

Beta2-glycoprotein I is necessary to inhibit protein C activity by monoclonal anticardiolipin antibodies

OBJECTIVE

To clarify mechanisms of the thrombosis associated with anticardiolipin antibodies (aCL), we examined the effects on activated protein C (APC) of monoclonal aCL and beta2-glycoprotein I (beta2GPI), which is required for formation of the epitopes of aCL.

METHODS

We developed the chromogenic assay, in which the degradation of coagulation factor Va by APC is reflected in the reduced generation of thrombin from prothrombin, using soybean trypsin inhibitor to inhibit APC. APC activities were measured in the presence and absence of 3.4 microM beta2GPI and/or 2.5 microg/ml of IgM monoclonal aCL (EY2C9 and EY1C8) established from peripheral blood lymphocytes obtained from a patient with aCL.

RESULTS

Without APC, the formed thrombin activity decreased by the addition of 3.4 microM beta2GPI. When 12.8 nM APC was added, beta2GPI partially reversed the APC-induced inhibition of thrombin generation in a concentration-dependent manner. With 3.4 microM beta2GPI, the thrombin generation in monoclonal aCL (2.5 microg/ml) decreased to 77.1-80.2% by the addition of 12.8 nM APC, but the values were above that in the control IgM (72.7%). Without beta2GPI, the APC activity was unaffected by the addition of monoclonal aCL.

CONCLUSION

Beta2-glycoprotein I exhibits procoagulant activity by inhibiting APC activity and anticoagulant activity by inhibiting thrombin generation. Any further inhibition of APC activity was caused by monoclonal aCL and only in the presence of beta2GPI.

Free radical scavenging activity in the nonenzymatic fraction of human saliva: a simple DPPH assay showing the effect of physical exercise

Free-radicals and other reactive oxygen species (ROS) have been implicated as being major damaging species in pathology and they have been widely investigated. Using 1,1'-diphenyl-2-picrylhydrazyl (DPPH), we estimated total free radical scavenging activity in the low-molecular-weight nonenzymatic fraction (LMNEF) of human whole saliva. The activity of the whole saliva and serum were measured in terms of the rate of decrease in the absorbance at 517 nm in a 40% ethanol DPPH solution (pH 7.4) at room temperature. The DPPH activity of saliva and serum showed a significant linear relationship. The mean DPPH activities of saliva from 257 subjects aged 4-72 was found to be 0.389+/-.190 micromol/ml and bore no relation to age or sex. The activity in saliva of 86 subjects aged 4-11 was significantly different before and after exhaustive aerobic dance exercise for 1 hr. Physical exercise markedly decreased free radical scavenging activity in whole saliva of children. On the basis of the above results, we concluded that DPPH is useful for evaluating the total antioxidant capacity of LMNEF of human saliva.

Alkalization produced by high-dose carbachol in HSG cell line is independent of Ca2+

OBJECTIVES

The aim of this investigation was to clarify the mechanism of alkalization induced by carbachol in HSG cells.

MATERIALS AND METHODS

Cells of the HSG cell line derived from a human submandibular gland adenocarcinoma and those of the A-431 human epidermoid carcinoma cell line were loaded with a fluorescent pH indicator, BCECF/AM, and the change in the intracellular pH of adherent cells and suspended ones were measured following stimulation with various concentrations (10(-7) M to 10(-2) M) of neurotransmitters (carbachol, noradrenaline, and isoproterenol).

RESULTS

Isoproterenol did not cause alkalization of either cell type, whereas, noradrenaline and carbachol alkalized both types over the concentration ranges of 10(-6) M to 3 x 10(-3) M (HSG cell by noradrenaline), 10(-7) M to 2 x 10(-4) M (A-431 cell by noradrenaline), and 7 x 10(-5) M to 10(-4) M (A-431 cell by carbachol). On the other hand, alkalization induced by carbachol in the HSG cells was recognized at concentrations higher than 6 x 10(-5) M, and it showed no upper limit in terms of carbachol concentration. This high-dose carbachol alkalization was not eliminated by preincubation with nifedipine (100 microM), a Ca2+ channel blocker, or with thapsigargin (100 microM), a microsomal Ca(2+)-ATPase inhibitor.

CONCLUSIONS

The alkalization system induced by carbachol in the HSG cell was quite different from that in the A-431 cell, and that induced by high-dose carbachol in HSG cells appeared to be independent of intracellular Ca2+. These findings will be useful to clarify the mechanism of salivary secretion stimulated by neurotransmitters.

Epitopes on beta2-GPI recognized by anticardiolipin antibodies

Anticardiolipin antibodies (aCL) found in sera from patients with antiphospholipid syndrome recognize a cryptic epitope that appears on the beta2-glycoprotein I (beta2-GPI) molecule when beta2-GPI interacts with a lipid membrane composed of negatively charged phospholipid or when beta2-GPI is adsorbed on a polyoxygenated polystyrene plate. A homology based model of beta2-GPI was constructed based on the NMR coordinates of sushi domains of human factor H. The conformation was like a cylinder consisting of five domains, its IV and V domains being glued by electrostatic interaction. We used phage-displayed random peptide libraries to search the epitopes of human aCL. Structures similar to consensus sequences selected by a biopanning method was found on domain IV of beta2-GPI.

Multiple antiphospholipid tests do not increase the diagnostic yield in antiphospholipid syndrome

The family of antiphospholipid antibodies (aPL) includes a heterogeneous population of autoantibodies whose specificity is directed against not only phospholipids, but their complex with plasma proteins. Anticardiolipin antibodies (aCL) and lupus anticoagulant (LA) tests are widely performed to screen the aPL family which is associated with thrombotic complications in patients with systemic lupus erythematosus (SLE) or antiphospholipid syndrome (APS). The clinical significance of other aPL tests, including antibodies against phosphatidylserine (aPS), phosphatidylinositol (aPI), phosphatidic acid (aPA), phosphatidylcholine (aPC) and phosphatidylethanolamine (aPE), has not been established. The purpose of this study was to evaluate whether multiple aPL tests have enhanced diagnostic value for APS. We tested IgG/M/A aPS, aPI, aPA, aPC and aPE by ELISA using 10% bovine serum as blocking and sample diluent in 26 SLE patients with clinical manifestations of APS, but negative for both aCL and LA (Group 1). The results were compared with 32 SLE patients without any features of APS (Group 2) and 24 SLE patients with APS (aCL and/or LA positive) (Group 3). In Group 1, 1/26 (4%) was positive for IgA aPE, less frequent than in other groups, and none of the patients had any other aPL. In Group 2, 1/32 (3%) was positive for aPS, two (6%) for aPI, one (3%) for aPA and four (12.5%) for aPE. None was positive for aPC. In the third group, 13/24 (54%) were positive for aPS, 11 (46%) for aPI, 15 (63%) for aPA, four (17%) for aPC and seven (29%) for aPE. Since aPE was found in some patients, we extended the study, including 207 SLE patients, and tested aPE. IgG/M/A aPE was found in six (3%), 10(5%) and 21 (10%), respectively, but no association was found between aPE and any clinical features of APS. This study suggests that screening by multiple aPL tests does not increase the diagnostic yield in APS.

Antibodies to beta2-glycoprotein I: a potential marker for clinical features of antiphospholipid antibody syndrome in patients with systemic lupus erythematosus

OBJECTIVE

To clarify risk factors for the development of clinical features of antiphospholipid syndrome (APS) in patients with anticardiolipin antibodies (aCL) in systemic lupus erythematosus (SLE).

METHODS

We studied 65 SLE patients, all with positive IgG and/or IgM aCL. Patients were divided into 2 groups; I: 29 SLE patients with features of APS (SLE/APS) and II: 36 aCL positive SLE patients without any feature of APS (SLE/aCL). Serum samples were collected from our serum bank. Anti-beta2-glycoprotein I (anti-beta2-GPI) were tested by ELISA using irradiated plates in the absence of cardiolipin. Anti-dsDNA antibodies were tested by standard Farr assay.

RESULTS

There were no major differences between SLE clinical manifestations in both groups. However, the frequency of IgG anti-beta2-GPI was markedly increased in SLE/APS (18/29, 62%) than in SLE/aCL (4/36, 11%) (chi-squared 18.6, p=0.0001). The levels of anti-dsDNA antibodies in the same samples were slightly lower in SLE/APS.

CONCLUSION

Our data suggest that increased levels of IgG anti-beta2-GPI may be a specific feature of SLE/APS patients rather than reflecting a polyclonal B cell activation.