Anticardiolipin Antibodies as a Risk Factor of Atherosclerosis in Intermittent Claudication

Anticardiolipin antibodies have been associated as a risk factor of atherosclerosis. The aim of this study was to evaluate the association between anticardiolipin antibodies and intermittent claudication. Forty consecutive patients (33 men, 7 women; age range: 45-84 years, mean 65.5) who were seen in the angiology and vascular surgery department with intermittent claudication were evaluated. Exclusion criteria included prior revascularization, angioplasty, or a history of thrombosis of a lower limb. Forty individuals (23 men, 17 women; age range: 58-82 years, mean 67.1) who attended a support group for senior citizens and who were apparently healthy formed the control group. Anticardiolipin antibodies were evaluated by means of enzyme-linked immunosorbent assay (ELISA) for quantitative measurement of immunoglobulin G (IgG) and IgM antibodies against cardiolipins in serum. IgG levels were considered normal when <7, borderline from 7 to 10, and elevated at >10 GPL units/mL; IgM levels were normal when <4, borderline from 4 to 7, and elevated at >7 MPL, as recommended by the test manufacturers. Statistical analysis used the relative risk test with a confidence interval of 95%. Twenty-three patients from the study group and 6 individuals from the control group were found to have elevated levels of anticardiolipin antibodies giving a relative risk of 3.833 (ranging from 1.749 to 8.4; p value <0.0001). In conclusion, patients who have elevated levels of anticardiolipin antibodies present a 3.8 times greater risk of developing intermittent claudication.

[The role of hyperhomocysteinemia in systemic lupus erythematosus and antiphospholipid syndrome]

AIM

To assess the role of hyperhomocysteinemia (HHC) in development of vascular complications in systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS).

MATERIAL AND METHODS

A total of 125 participants (24 males and 101 females aged 38 +/- 13 years) were divided into three groups: group 1--SLE patients (n=51); group 2--SLE+APS patients (n=49); group 3--primary APS patients (n=25). The patients had the disease for 14 +/- 11 years. Lupus anticoagulant (LA) and anticardiolipin antibodies (aCL) marked APS serologically. Homocystein (HC) was assayed by high performance liquid chromatography. HHC (HC > 15 mcg/l) was diagnosed in 82 of 125 (66%) patients: in 59% patients of group 1, 67%--of group 2 and 76%--of group 3. There was a relationship between HHC and digital necrosis (DN): 80% of DN patients had HHC while HHC was diagnosed in 57% patients free of DN (chi-square = 4.76, p = 0.03). Development of occlusions in APS was associated with HHC. Elevated levels of HC in blood was registered in 43 of 55 (78%) APS patients with thromboses vs. 9 of 19 (47%) patients with APS free of thromboses (p = 0.03). HHC occurred significantly more frequently in patients with arterial thromboses (in all 14 patients) than in patients with venous thromboses (in 16 of 23--69.6%, p = 0.03) and in the absence of thromboses (in 9 of 19, 47.4%, p = 0.04). HHC was associated with thromboses of cerebral, peripheral arteries (90 vs. 47% in patients without thrombosis, p = 0.005; 84 vs. 47%, p = 0.04, respectively), coronary vessels (79 vs. 47%, p = 0.04). In APS patients having arterial thromboses with duration of postthrombocytic period (PTP), estimated as time from thrombosis to entering the trial, less than 2 months, HC concentration was significantly higher (22.9 +/- 7.0 mcg/l) compared to patients with PTP more than 2 years (16.6 +/- 3.7 mcg/l (p = 0.04).

CONCLUSION

More than 50% patients with SLE and APS, irrespective of APS variants, had an elevated HC level in the blood. Correlation between HHC and development of thromboses, primarily arterial, in APS gives grounds for the role of HHC in development of vascular complications in SLE and APS.

Anticardiolipin antibodies and ocular disease

This paper reviews anticardiolipin antibodies and ocular disease. Its aim is to present the latest knowledge regarding the relationship between the two. It focuses mainly on ocular features and treatment, but also describes the epidemiology, main systemic features, immunology, and immunopathology of the antiphospholipid syndrome.

Lupus anticoagulant in cardiovascular diseases: the role of beta2-glycoprotein I

The presence of antiphospholipid antibodies (aPL) in plasma is an important risk factor for the development of thrombosis. A major breakthrough came in 1990 with the finding that aPL do not react with phospholipids per se, but are directed towards beta2-glycoprotein I, a plasma protein with affinity for anionic phospholipids. Afterwards other plasma proteins with affinity for phospholipids have been identified as possible antigens for aPL. Human beta2-glycoprotein I is a heavily glycosylated plasma protein that has been implicated in the binding of aPL to negatively charged phospholipids. We recently solved the crystal structure of beta2-glycoprotein I. In this review we will discuss what the 3-dimensional structure teaches us about the role of beta2-glycoprotein I in the pathogenesis of the thrombotic complications characteristic of the antiphospholipid syndrome.

Venous gangrene in a patient with adenocarcinoma of the lung

Cancer-related thromboembolism is a severe but not uncommon paraneoplastic syndrome in mucinous cancer patients. However, cancer-induced venous gangrene is extremely rare and has never been reported in the English literature. Here, we present a case of lung cancer complicated with venous gangrene of the left foot. An elevated serum anticardiolipin level was detected during hospitalization, but the patient's clinical condition stabilized after heparinization. We suggest that in cancer patients, an elevated serum anticardiolipin antibody level might be a warning sign of an impending thrombotic event and that low-molecular-weight heparin is a sensible choice in treating this kind of cancer-related thromboembolism.

[Antiphospholipid antibodies and thrombosis: the putative mechanisms of hypercoagulable state in patients with anticardiolipin antibody]

Antiphospholipid antibodies are well recognized as associated with serious clinical complications such as arterial and venous thrombosis and recurrent spontaneous abortion. These complications are collectively called antiphospholipid syndrome(APS). The mechanisms responsible for the thrombosis are unclear. We reported three mechanisms. beta 2-glycoprotein I(beta 2GPI) inhibited activated protein C(APC) activity and, furthermore, APC activity decreased by the addition of monoclonal aCL and beta 2GPI. Monoclonal anticardiolipin antibodies(aCL) seemed to enhance the inhibition of APC procoagulant activity caused by beta 2GPI. Monoclonal aCL in the presence of beta 2GPI also increased the activity of plasminogen activator inhibitor(PAI)-1 in the mixture of tissue-plasminogen activator(t-PA) and PAI-1 by inhibiting the function of beta 2GPI, which increased the remaining t-PA activity in the mixture. The formation of thrombin-antithrombin complexes(TAT) in APS was impaired. The level of TAT in APS did not increase, however the level of prothrombin fragment 1 + 2 (F1 + 2) increased. Therefore, free thrombin present in patients' blood may contribute to thrombosis in APS. These reports indicate that thrombosis in APS may be caused by several thrombogenic factors that stimulate aCL.

[Investigation of binding capacity of beta 2-glycoprotein I with anti-beta 2-glycoprotein I antibodies in lymphocytes undergoing apoptosis]

Apoptosis (programmed cell death) is accompanied by loss of phospholipid asymmetry, i.e., translocation of aminophospholipids such as phosphatidylserine to the outer leaflet of the plasma membranes, which results in recognition of these cells by macrophages. In the present study, I studied on the involvement of beta 2-glycoprotein I (beta 2-GPI) and anti-beta 2-GPI antibodies in apoptotic lymphocytes. By flowcytometric analysis, I demonstrated that beta 2-GPI could bind to a human T cell line, Jurkat cells, treated with an anti-Fas antibody, CH11. beta 2-GPI-bound cells were detected 2 hr later after anti-Fas treatment and the most cells were bound to beta 2-GPI by 6 hr later. The accumulation of beta 2-GPI-bound cells paralleled with morphological changes and DNA fragmentation of the cells. I also demonstrated that anti-beta 2-GPI antibodies and a beta 2-GPI-dependent anti-cardiolipin antibody, established from a patient with antiphospholipid syndrome, could recognize beta 2-GPI-bound Jurkat cells treated with anti-Fas-antibody. These results imply that beta 2-GPI and anticardiolipin antibody may have a role in the clearance of apoptotic cells from the blood stream.

[Association between antiphospholipid antibodies and arterial or venous thrombosis/thrombocytopenia]

The relationship between thrombotic or thrombocytopenic complications and the existence of anticardiolipin antibodies (aCL) and/or lupus anticoagulant (LA) was studied in 146 patients with systemic lupus erythematosus (SLE). The prevalence of arterial thrombosis was obviously higher in patients who had both aCL and LA than in patients with either aCL or LA alone or in those with neither. Since a substantial fraction of the former group of patients with arterial thrombosis also had thrombocytopenia, there is a possibility that aCL and LA might enhance platelet activation and aggregation. To test this hypothesis, we studied the in vitro effects of aCL and LA on the enhancement of platelet activation by flow cytometric analysis using anti-CD62P and anti-CD41 monoclonal antibodies directed against platelet activation-dependent granule-external membrane (PADGEM) protein and platelet glycoprotein IIb (GPIIb). The IgG fraction purified from aCL+.LA+ plasma apparently enhanced platelet activation induced by adenosine diphosphate (ADP) at a low concentration, but IgG fractions from aCL+.LA- or aCL-.LA+ plasma did not cause enhancement of platelet activation. These results suggest that aCL and LA may cooperate to promote platelet activation, and may be involved, at least partially, in the pathogenesis of arterial thrombosis in patients with SLE.

Cardiolipin binding a light chain from lupus-prone mice

Autoantibodies in systemic lupus erythematosus react with multiple epitopes on highly conserved molecules such as nucleic acids, cytoskeletal proteins, phospholipids, and phospholipid-binding proteins. Analysis of the heavy- and light-chain variable sequences (VH and VL) has shown that a restricted set of V genes gives rise to these autoantibodies. Several monoclonal antibodies were developed from a strain of mouse prone to lupus (F1 male NZW x BXSB). Two of these antibodies, A1.72 and A1.84, reacted directly with cardiolipin and their VH and VL sequences were analyzed. Surprisingly, these two antibodies had identical light-chain variable sequences despite having substantially different heavy-chain variable sequences. This VL sequence, VL 72/84 was 97% identical with the germ-line sequences with only four single nucleotide substitutions. When this VL sequence was shuffled with the VH sequence of other monoclonal antibodies and expressed as single chain variable fragment (scFv) in Escherichia coli, it imparted cardiolipin-binding activity to the hybrids. Furthermore, the VL 72/84 sequence, when expressed alone without any VH sequence, also bound to cardiolipin. The antibodies and their recombinant fragments were immunoaffinity-purified on cardiolipin liposomes. The dissociation constant of the light chain for cardiolipin was similar to the intact molecule (21 +/- 0.01 vs 20 +/- 0.03 nM). These studies demonstrate that the VL sequence alone, in the absence of any other immunoglobulin domains, can mediate cardiolipin binding, raising the possibility that antigen specificity of certain antibodies may exclusively reside in their light-chain sequences.

A highly specific functional test for factor V leiden: A modified tissue factor assay for activated protein C resistance

We compared the sensitivity and specificity of a tissue factor-based assay (FVR) with the addition of a phospholipid/silica preparation, to the commercially available aPTT-based method, APCR (CoatestTM), and a modified aPTT-based method (APCM) which utilized factor V-depleted plasma, for the detection of the factor V Leiden mutation. A total of 110 patients were included in this study. This included 32 patients on coumadin therapy, 7 patients on heparin therapy, 5 patients on both anticoagulants therapy, and 24 patients who were positive for anticardiolipin antibody (ACL) and/or lupus inhibitor (LI). Our data demonstrate that the FVR is not affected by anticoagulation treatment or ACL/LI antibodies, whereas in the APCR method, 33 patients cannot be determined either due to the anticoagulant therapy or presence of the ACL and/or LI. With the APCM method, the clotting endpoint could not be determined in 1 patient due to the presence of a strong LI. The additional phospholipid/silica material utilized in the FVR enhanced the APC degradation of factor Va and therefore sharpened the demarcation between the factor V Leiden-positive and -negative patients. The sensitivity for the APCR, APCM and FVR was 42, 97 and 100% respectively. The specificity for the APCR, APCM and FVR was 94, 96 and 100% respectively.

Activated protein C resistance phenotype in patients with antiphospholipid antibodies

The effect of antiphospholipid antibodies (aPL) on the action of activated protein C (APC) was examined in 32 patients: 19 with lupus anticoagulant (LA), 6 with anticardiolipin antibodies (aCL), and 7 with LA and aCL. Eighteen patients had a ratio of activated partial thromboplastin time (APTT) with APC to APTT without APC (APTT ratio) <2.06 (cut-off level) and no factor V Leiden mutation; these patients showed APC-resistance (APC-R) phenotype. The mean prolongation of APTT after addition of APC in a control group was 45.3 seconds, with a lower limit of 31.4 seconds. Only 3 of the 18 patients with low APTT ratio had a prolongation of <31.4 seconds; they were classified as true APC-R phenotype, whereas the other 15 patients were classified as spurious APC-R. Of the 3 patients with true APC-R, 2 had deep venous thrombosis, 1 with pulmonary embolism, and the third had recurrent abortion. Of the other 15 patients, 2 had had ischemic stroke, 1 had recurrent abortion, and 12 were asymptomatic. Circulating APC level was measured in 14 of the 18 aPL patients with a low APTT ratio; it was lower than the normal lower limit in 4 patients and within the lower limit in 2. Three of the 4 patients with reduced APC levels had a history of thrombosis. We conclude that patients with aPL who show APC-R phenotype due to a low APTT ratio without the factor V Leiden mutation can be classified into two groups: true and spurious APC-R phenotype. Since those with true APC-R phenotype could have greater thrombotic risk, adequate classification of these patients is important. Moreover, aPL can sometimes interfere with the activation of protein C, thus reducing the circulating levels of APC, and this could constitute another thrombotic risk factor.

Antiphospholipid antibody: functional specificity for inhibition of prothrombin activation by the prothrombinase complex

The antiphospholipid syndrome (APS) is associated with production of autoantibodies with lupus anticoagulant (LA) activity. These antibodies cause prolongation of in vitro clotting tests by inhibition of the conversion of prothrombin to thrombin in the presence of anionic phospholipid (PL). The extent to which this inhibition reflects antibody binding to, or functional inhibition of, phospholipids alone, prothrombin alone, or a prothrombin-phospholipid complex is pertinent to our understanding of the pathophysiology of this syndrome. Immunoglobulin fractions (IgG) from 18 patients with LA activity were tested for inhibitory activity against prothrombin activation by either factor Xa, in a purified prothrombinase system, or by purified fractions of snake venoms (E. carinatus, E. multisquamatus) which cleave prothrombin at the same initial site as the prothrombinase complex but do not require anionic phospholipid as a cofactor. Parallel testing of the same IgG samples for prothrombin binding by immunoassay was performed. Although all IgG samples inhibited the prothrombinase reaction, only three exhibited any inhibition of venom protease prothrombin activation in either the presence or absence of PL. Only one sample exhibited prothrombin binding by Western blot. These results suggest that lupus anticoagulant antibodies are heterogenous and that many, if not most, of the autoantibody populations responsible for LA activity impair prothrombin activation by interaction either with phospholipid alone or with a restricted range of prothrombin-phospholipid epitopes expressed by prothrombin only as part of the intact prothrombin-prothrombinase complex.

In vivo models of thrombosis for the antiphospholipid syndrome

Utilizing this unique animal model of thrombosis we demonstrated that human (IgG, IgM or IgA) polyclonal and monoclonal antiphospholipid antibodies derived from APS patients have a significant enhancing effect on thrombus formation. This effect is reversed by treatment of the mice with hydroxychloroquine (plaquenil). In addition murine polyclonal and monoclonal anticardiolipin antibodies induced by active immunization with human beta 2-GP1 or human anticardiolipin antibodies showed to have thrombogenic properties in CD1 mice. Antibodies with antihuman beta 2-GP1 activity alone did not seem to affect thrombus formation.

Functional effects of anticardiolipin antibodies

The 'lupus anticoagulant' phenomenon is the best documented functional effect of antiphospholipid (aPL) antibodies, occurring either by inhibition of the prothrombinase and/or Factor X activation reactions. Understanding the mechanism by which aPL antibodies inhibit phospholipid dependent coagulation reactions may yield important clues about their 'thrombogenic effects' in vivo. We conducted a series of studies to determine the specificity, diversity, and mechanism by which aPL antibodies inhibit phospholipid dependent reactions. Results showed that purified immunoglobulins with lupus anticoagulant and anti-cardiolipin activities were absorbed by negatively charged phospholipids and both activities were recovered from the phospholipid-antibody precipitate. Purified aPL antibodies inhibited the prothrombinase reaction in a plasma free system in which beta 2-glycoprotein 1 (beta 2-GP1) was absent. Affinity purified aPL antibodies had 25-50 times the inhibitory activity of immunoglobulin preparations. The phospholipid binding proteins, beta 2-GPI and placental anticoagulant protein I (PAP I), independently inhibited the prothrombinase reaction, and when these proteins were combined with aPL, inhibition of the prothrombinase reaction was additive. Antibodies of syphilis had no inhibitory effect, partially accounted for by lack of specificity for phosphotidylserine (PS). Although aPL antibodies inhibited the protein C activation reaction, there was no correlation of these activities with inhibition of the prothrombinase reaction. Together, these results show that aPL exert their effects by interaction with negatively charged phospholipids, in particular phosphotidylserine, but lack of correlation between inhibition of the prothrombinase and protein C activation reactions, suggests that the nature of the coagulation protein is also important.

Thrombogenic properties of murine anti-cardiolipin antibodies induced by beta 2 glycoprotein 1 and human immunoglobulin G antiphospholipid antibodies

BACKGROUND

Recurrent arterial thrombosis and venous thrombosis are frequent complications of the antiphospholipid syndrome (APS). Patients produce anti-cardiolipin antibodies, but the role of these antibodies in thrombus formation is uncertain. This study used a unique CD-1 mouse model of thrombosis to determine whether anti-cardiolipin and anti-beta 2 glycoprotein 1 (beta 2 GP1) antibodies induced immunologically in these animals are thrombogenic.

METHODS AND RESULTS

The CD-1 mouse model enables measurement of the kinetics of a thrombus induced in the femoral vein of the animal. Animals are first anesthetized, then one femoral vein is exposed and subjected to a standardized, nonpenetrating "pinch" injury that induces a thrombus. The vein is trans-illuminated, and the growing thrombus is visualized on a television screen. The rate of formation and disappearance of the thrombus as well as its area can be measured by a computer attached to the television. Three groups of CD-1 mice (each group comprising seven animals) were studied. Group 1 mice were actively immunized with beta 2GP1, resulting in production of anti-beta 2GP1 and anti-cardiolipin antibodies. Group 2 mice were actively immunized with human immunoglobulin G (IgG) anti-cardiolipin antibodies and produced anti-human IgG as well as anti-cardiolipin antibodies (the latter by an idiotype-anti-idiotype reaction). These animals did not produce anti-beta 2GP1 antibodies. Group 3 mice were immunized with human serum albumin (HSA) and produced anti-HSA but not anti-cardiolipin antibodies. The kinetics of thrombus formation induced in the femoral veins of the experimental mice were compared. Results showed that the mean thrombus area as well as mean time during which thrombi persisted were significantly greater in group 1 and group 2 mice compared with group 3. There was no statistical difference between group 1 or group 2.

CONCLUSIONS

Demonstration of a thrombogenic effect of murine anti-cardiolipin antibodies suggests that these antibodies may be pathogenic in humans with APS.

Anticardiolipin antibodies in patients with pregnancy loss induce factor Xa production in the presence of beta 2-glycoprotein I

PROBLEM

Anticardiolipin antibodies (aCL) are commonly associated with recurrent pregnancy loss, though the mechanism is uncertain. Some investigators have indicated that aCL may be directed at a complex made up of cardiolipin and a blood anticoagulant, beta 2-glycoprotein I (beta 2GPI). We therefore investigated the effects of beta 2GPI-dependent aCL IgG enriched fractions, isolated from sera of patients with pregnancy losses, on blood coagulation.

METHOD

beta 2GPI-dependent aCL were prepared from sera of three women with second trimester pregnancy losses, by cardiolipin affinity column chromography, following by anti-beta 2GPI affinity column chromatography. The effects of beta 2GPI and beta 2GPI-dependent aCL on the activation of factor X in vitro were examined.

RESULTS

beta 2GPI inhibited the activation of factor X and beta 2GPI-dependent aCL blocked this inhibitory effect in a dose dependent manner.

CONCLUSION

These results imply the possibility of beta 2GPI-dependent aCL induce hypercoagulation or thrombus by blocking the inhibitory effect of beta 2GPI on activation of factor X, which may result in pregnancy loss.

Antibodies to oxidized low-density lipoprotein and to cardiolipin in nonpregnant and pregnant women with habitual abortion

OBJECTIVE

To determine the occurrence of antibodies to oxidized low-density lipoprotein (LDL) in women with a history of habitual abortion before and during pregnancy.

DESIGN

Immunoglobulin G class antibodies to malondialdehyde modified LDL were determined by a solid-phase ELISA in 42 habitual aborters before pregnancy, in 39 patients during pregnancy, and in 23 comparable nonpregnant and 22 pregnant control women without a history of abortion. In addition, we assessed the presence of anticardiolipin antibodies by ELISA in the same sera.

SETTING

Departments I and II of Obstetrics and Gynecology, University Central Hospital of Helsinki, Helsinki, Finland.

RESULTS

Early pregnancy was accompanied by a decrease in the median levels of antibodies to oxidized LDL both in habitual aborters and in the control series. Only one patient exhibited a raised level of antibodies to oxidized LDL before pregnancy but, during pregnancy, nine patients (23%) had elevated levels of antibodies to oxidized LDL, similar to women with a favorable outcome of pregnancy (6/27, 22%) and in women whose current pregnancy also ended in abortion (3/12, 25%). Cardiolipin binding antibodies were detected in three habitual aborters before pregnancy (7%) and in nine women during pregnancy (23%), with a tendency to be more frequent in patients with miscarrying pregnancies than in those with continuing pregnancies (4/12, 33% and 5/27, 19%). Antibodies to oxidized LDL and cardiolipin were simultaneously present in three habitual aborters with continuing pregnancies.

CONCLUSIONS

Increased levels of antibodies to oxidized LDL and cardiolipin may be associated with habitual abortion.

Differences in functional activity of anticardiolipin antibodies from patients with syphilis and those with antiphospholipid syndrome

Anticardiolipin antibodies are produced both in patients with the antiphospholipid syndrome (APS) and in patients with syphilis, but lupus anticoagulant activity has been reported only for the former group. To understand these differences, affinity-purified immunoglobulin G anticardiolipin antibodies from APS (n = 11) and syphilis (n = 5) patients were compared. Only the antibodies from the APS group inhibited prothrombin conversion to thrombin and cross-reacted with phosphatidylserine. These findings may enable better definition of the phospholipid epitopes involved in the hemostatic abnormalities of APS.

Anticardiolipin antibodies: specificity and function

Antibodies detected by solid phase anticardiolipin immunoassays are heterogeneous but understanding the nature of this heterogeneity has proven difficult. Differences in any of the following features may account for differences in anticardiolipin antibodies: avidity for cardiolipin, phospholipid cross-reactivity, specificity for beta 2 glycoprotein I (beta 2GPI)-cardiolipin complexes, functional activity (as defined by the ability to inhibit phospholipid dependent coagulation reactions) and specificities for different conformations of phospholipids. Understanding these differences may be important in explaining the variations in clinical presentation of patients with these antibodies. This review attempts to define and discuss anticardiolipin heterogeneity.

The role of anticardiolipin autoantibodies in the pathogenesis of autoimmune hemolytic anemia in systemic lupus erythematosus

OBJECTIVE

To elucidate the role of anticardiolipin antibodies (aCL) in the pathogenesis of hemolytic anemia in patients with systemic lupus erythematosus (SLE).

METHODS

Immunoglobulins (Ig) and cardiolipin reactivity were evaluated in red blood cell (RBC) eluates and in the sera of patients with SLE and controls by a solid phase enzyme linked immunosorbent assay.

RESULTS

aCL were detected in sera of 2 patients with SLE with active hemolytic anemia. The RBC eluates of these patients contained Ig (mainly IgG) with significant cardiolipin reactivity. RBC eluates from healthy volunteers failed to demonstrate measurable amounts of Ig whereas Ig eluted from RBC of chronic lymphocytic leukemia patients with active hemolysis but no aCL did not react with cardiolipin. Furthermore, under treatment, one patient went into complete remission with resolution of the hemolysis, negative Coombs' tests and lower serum aCL. The other patient, however, continued to demonstrate both high sera aCL and positive Coombs' tests.

CONCLUSION

aCL may play a direct role in the pathogenesis of hemolytic anemia in some patients with SLE by acting as anti-RBC autoantibodies.

Prevention and induction of occlusive coronary vascular disease in autoimmune (W/B)F1 mice by haploidentical bone marrow transplantation: possible role for anticardiolipin autoantibodies

Male (NZW x BXSB)F1 (W/BF1) mice develop systemic autoimmunity involving autoantibodies, thrombocytopenia, lupus nephritis, and coronary vascular disease with myocardial infarction (CVD). To determine whether this murine lupus-associated CVD could be transferred to otherwise autoimmune-resistant (C57BL/6 x C3H/He)F1 (B6C3F1) mice via W/BF1 T-cell-depleted marrow (TCDM) transplants, or conversely whether the CVD of W/BF1 mice could be prevented by the reciprocal transplant, reciprocal haploidentical transplants of TCDM were performed. CVD developed only in mice with systemic autoimmunity. Mice that developed lupus had glomerulonephritis and thrombocytopenia and also had elevated titres of autoantibodies to double-strand DNA, cardiolipin, and platelets and elevated levels of circulating immune complexes. Of control W/BF1 mice, 80% developed lupus, and of these, 81% developed CVD with a mean grade of 2.5 +/- 0.8. Engraftment of W/BF1 mice with B6C3F1 marrow protected 90% of the recipients from the development of lupus, and none developed CVD. Engraftment of B6C3F1 mice with W/BF1 marrow induced lupus in 60% of the recipients, and of those, 33% developed CVD with a mean grade of 1.3 +/- 0.3. The B6C3F1 recipients of W/BF1 marrow which developed CVD had significantly higher titres of autoantibodies to cardiolipin (aCL; P < .01). These findings show that genetic abnormalities present in the W/BF1 hematopoietic stem cells contribute to autoantibody development, including aCL, and suggest that thrombogenic mechanisms induced by aCL may contribute to the development of CVD in this form of murine lupus erythematosus.

Acetylsalicylic acid inhibits anticardiolipin antibody-induced platelet-activating factor (PAF) synthesis

Enhanced endothelial cell PAF synthesis has been identified as a consequence of anticardiolipin antibody (ACA)-positive serum exposure. We proposed this observation as a contributing factor to thrombogenesis in women with the antiphospholipid syndrome. Since acetylsalicylic acid (ASA) is an accepted therapeutic alternative in these patients, we sought to determine if ASA would attenuate endothelial cell PAF production resulting from ACA exposure. Using primary, confluent monolayers of umbilical vein endothelial cells, experiments were performed to evaluate PAF synthesis after incubation with antibody-positive serum and ASA. Total PAF and its radyl-derivatives (1-alkyl- and 1-acyl-PAF) were quantified by tritiated acetate incorporation, phospholipid extraction, thin-layer chromatography and scintillation spectroscopy. ASA consistently decreased ACA-induced PAF synthesis (No ASA, 9573 +/- 443 vs 1mmol/L ASA, 4829 +/- 838 dpm/ml; p = 0.016) and the observed reduction was dose-dependent over a range of ASA concentrations (0.1, 1, 10 and 100 mmol/L; ANOVA, p = .00015). Reduced PAF synthesis was also observed in cultures exposed to ASA and incubated with antibody-negative serum. These observations suggest that in ACA-positive women, the antithrombotic effects of ASA may relate in part, to reduced endothelial cell PAF synthesis.