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Biomedical subjects

E N Harris

Publications and source records attributed to E N Harris.

At least 55 records · Page 3Linked to original sources
PubMed1996

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.

Antibodies, Anticardiolipin↗
PubMed1996

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.

Animals↗
PubMed1995

The antiphospholipid syndrome. Diagnosis, management, and pathogenesis.

Much more is known about the APLS than 15 yr ago, but more needs to be done. Clinically, major characteristics of the disorder have been defined, but the course of the disease and its relationship to other disorders, such as systemic lupus erythematosus (SLE), need to be defined. Good progress has been made in standardizing anticardiolipin and, to a lesser extent, LA. However, problems with interlaboratory and inter-assay variation need to be addressed. Doctors are getting a better idea of how to manage these patients with a view to preventing recurrences of thrombosis or pregnancy losses, but prospective studies are still desirable to give more definitive answers. Attention has turned to the pathogenesis of the disorder. It seems likely that antibodies mediate the clinical disorders with which they are associated, but the mechanisms by which this occurs still require further study.

Antibodies, Anticardiolipin↗
PubMed1995

Diastolic dysfunction is a feature of the antiphospholipid syndrome.

Recurrent thrombi, thrombocytopenia, pregnancy loss, and stroke in association with medium to high concentrations of anticardiolipin antibodies are well-recognized features of antiphospholipid syndrome. Cardiac manifestations of primary antiphospholipid syndrome (PAPS) also have been documented but involve structural and valvular heart disease. Diastolic dysfunction in PAPS has not been well described. Therefore, 10 patients with PAPS (nine women and one man) of mean age 30 +/- 7 years (range 20 to 46 years) and 10 healthy age-, sex-, weight-, and height-matched control subjects were studied by echocardiography. Anticardiolipin antibody concentrations of patients with PAPS were > 80 immunoglobulin G phospholipid units as determined by enzyme-linked immunosorbent assay. Doppler-derived parameters of left ventricular filling showed a significant association between PAPS and diastolic dysfunction compared with control, as evidenced by a decrease in peak early filling velocity (52 +/- 10 cm/sec vs 67 +/- 12 cm/sec; p < 0.01), a decrease in the ratio of peak early to peak atrial filling velocities (1.03 +/- 0.40 vs 1.52 +/- 0.28; p < 0.005), a decrease in the mean deceleration rate of early filling (338 +/- 75 cm/sec2 vs 590 +/- 227 cm/sec2; p < 0.005), and an increase in the percentage of atrial contribution to filling and deceleration time. Left ventricular mass, diastolic filling time, and heart rate did not differ between groups. Left ventricular systolic function was normal and ejection fraction did not differ between patients with PAPS and control subjects (63% +/- 2% vs 65% +/- 7%; p not significant).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Intravenous immunoglobulin therapy for the antiphospholipid syndrome in pregnancy.

OBJECTIVE: Our purpose was to study the influence of intravenous immunoglobulin on pregnancy outcome. STUDY DESIGN: Pregnancy outcomes were evaluated in five patients with 17 unsuccessful previous pregnancies. Each patient received 400 mg/kg immunoglobulin for 5 days monthly beginning in the first or early second trimester. Four patients with previous thromboembolic events were treated with concomitant heparin prophylaxis. Four patients received 81 mg of aspirin daily. RESULTS: Short- and long-term decreases of anticardiolipin immunoglobulin G were noted in three patients. Four patients were delivered of healthy infants at term, one at 32 weeks' gestation with a diagnosis of fetal distress. Neither preeclampsia nor fetal intrauterine growth retardation were observed. The immunoglobulin therapy was not associated with major side effects. Significant placental histologic anomalies were not identified. CONCLUSIONS: The observations suggest that immunoglobulin therapy may improve pregnancy outcomes beyond that observed with heparin and aspirin. A prospective trial is encouraged.

Adult↗
PubMed1995

Induction of high levels of anticardiolipin antibodies in mice by immunization with beta 2-glycoprotein I does not cause fetal death.

OBJECTIVE: Our purpose was to determine whether anticardiolipin antibodies induced by immunization with beta 2-glycoprotein I cause fetal death in mice. STUDY DESIGN: Female BALB/c mice were immunized with beta 2-glycoprotein I in a carbohydrate adjuvant or with carbohydrate adjuvant alone. The mice were mated with BALB/c males and killed on day 11 to 13 of pregnancy, and the fetal status was determined. Posttreatment blood samples were obtained for measurement of anticardiolipin and anti-beta 2-glycoprotein I antibodies and platelet counts. RESULTS: Anticardiolipin and anti-beta 2-glycoprotein I antibodies developed in all mice immunized with beta 2-glycoprotein I. Fetal death occurred in 17 of 145 gestational sacs (12%) in 18 mice immunized with beta 2-glycoprotein I compared with 24 of 177 (14%) sacs in 21 control mice. There were no morphometric or histologic differences between gestational tissues, and platelet counts were similar for each group. CONCLUSIONS: The induction of high levels of anticardiolipin antibodies in BALB/c mice by beta 2-glycoprotein I immunizations did not result in fetal death or thrombocytopenia. These nonpathogenic beta 2-glycoprotein I-induced anticardiolipin antibodies should prove useful in the characterization of clinically relevant epitopes for antiphospholipid syndrome.

Animals↗
PubMed1995

Interactions and molecular structure of cardiolipin and beta 2-glycoprotein 1 (beta 2-GP1).

beta 2-GP1 is a serum protein which influences binding of anticardiolipin antibodies to cardiolipin, may influence induction of these antibodies in animals and may play a role in anticardiolipin-mediated thrombosis. Various investigators have proposed that when beta 2-GP1 binds cardiolipin, structural alterations occur in one or both molecules, resulting in exposure of new epitopes for anticardiolipin binding, but there has been no proof that such alterations occur. Utilizing Fourier transform infrared spectroscopy, this study analysed the structure of cardiolipin and beta 2-GP1 alone, then mixed with each other. For pure cardiolipin, analysis of the CH2 stretching, scissoring and carbonyl bands suggested this molecule assumes a hexagonal crystal lattice packing structure in both anhydrous and aqueous samples. Based on the second derivative analysis of the amide 1 band from the beta 2-GP1 protein backbone, as well as Fourier self-deconvolution and curve fit algorithms, beta 2-GP1 was calculated to contain 18% turns, 37% alpha-helix, and 45% beta-sheet structure. beta 2-GP1 binding with cardiolipin results in a significant change in the conformation as well as geometry of the lipid and protein components. This is indicated by a broadening of the CH stretching band and a marked shift in intensity of the carbonyl band of cardiolipin, indicating less hydrogen bonding. There was a decrease in beta-sheet structure of beta 2-GP1 from 46% to 23% and appearance of 26% to 28% random structure. These findings indicate that mixing beta 2-GP1 with cardiolipin results in profound changes in both molecules which might explain the effect of beta 2-GP1 on anticardiolipin binding activity.

Amides↗
PubMed1995

Demonstration of antiphospholipid antibody heterogeneity by phospholipid column chromatography and salt gradient elution techniques.

Antiphospholipid (aPL) antibodies are associated with thrombosis, recurrent abortions and thrombocytopenia. Studies to determine the mechanisms of action of these antibodies have been hindered by their heterogeneity and limited availability of techniques to isolate and characterize subgroups of the antibodies. We report a new phospholipid affinity chromatography method which enables separation of antiphospholipid positive sera into more than one antibody subpopulation. Sera from five patients with complications of the antiphospholipid syndrome (APS) were studied. Each serum was applied to chromatography columns prepared by coating polystyrene beads (diameter 100 A) with phosphatidylserine (PS) or cardiolipin (CL). A linear salt gradient (0.03-1.0 M NaCl) was used for elution. Eluates were analyzed for phospholipid binding and for inhibition of the prothrombin-thrombin conversion reaction. Each sample yielded two to three peaks for CL and PS affinity columns. Molarities at which peaks were eluted differed between samples. For individual samples, molarities at which peaks were eluted differed between CL and PS columns. These data suggest that aPL antibodies are heterogenous, with differences existing between patients and even within single serum samples. Subpopulations differed in their avidities for CL and PS but generally all had prothrombinase inhibitory activity.

Adult↗
PubMed1995

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.

Adenosine Diphosphate↗
PubMed1995

Familial anticardiolipin antibodies and C4 deficiency genotypes that coexist with MHC DQB1 risk factors.

OBJECTIVE: To investigate the familial basis of antiphospholipid antibodies by studying putative risk factors at the C4 and MHC class II loci. METHODS: Autoimmune diseases, anticardiolipin (aCL) and other autoantibodies were studied in 38 first and 2nd degree family members of 3 index cases selected for primary antiphospholipid syndrome (APS) and 33 controls. C4 protein phenotyping and restriction fragment length polymorphism analysis of C4 and MHC class II loci were performed. RESULTS: Nineteen family members (46%) had autoimmune diseases or autoantibodies; aCL were present in 10 family members, 4 of whom had primary APS. Each family had 2 or more subjects with aCL. Among 22 independent haplotypes in family members, there was a high frequency of C4A and C4B deficiency alleles (0.41 vs 0.18 in 66 controls, p = 0.03) and a strong trend toward an increase in MHC DQB1 putative risk factors that share the TRAELDT structural domain. This DQB1 structural domain was present in 4/5 different haplotypes that contained a C4B deficiency genotype; however, neither of 2 different haplotypes with a C4A deletion (one being a common ancestral haplotype) contained this DQB1 putative risk factor. Among the 10 family members who had aCL, 10/20 haplotypes contained a C4 deficiency genotype; moreover, the DQB1 putative risk factor was present in all 16 MHC haplotypes that did not contain a C4A deletion. CONCLUSION: In these families, expression of an autoimmunity trait as aCL antibody appears to be associated with the coexistence of C4 deficiency alleles with DQB1 alleles that contain the TRAELDT structural domain.

Adolescent↗
PubMed1995

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.

Animals↗
PubMed1994

Antiphospholipid antibodies and the antiphospholipid syndrome.

The study of aPL antibodies and the APS has appealed to large numbers of investigators over the last decade. This accounts, in part, for the great degree of apparently contradictory data being published. What seems certain is that these antibodies are associated with thrombosis and recurrent pregnancy loss, and animal data suggest a direct role in pathogenesis. In vitro studies demonstrate that these antibodies have a variety of functional effects on the hemostatic system, giving further credence to an antibody role in thrombosis. Further studies will doubtless give better insight into the mechanisms of antibody action and this will provide a more rational basis for treatment.

Animals↗
PubMed1994

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.

Antibodies, Anticardiolipin↗
PubMed1994

Inhibition of prothrombin activation by antiphospholipid antibodies and beta 2-glycoprotein 1.

Lupus anticoagulants, commonly found in the immunoglobulin fraction of patients with the antiphospholipid syndrome (APS), and the normal plasma protein beta 2-glycoprotein 1 (beta 2GP1) may both contribute to the in vitro impairment of prothrombin activation associated with the APS. We examined the effects upon prothrombin activation supported by phospholipid vesicles of plasma IgG preparations from APS patients in the presence and absence of beta 2GP1. Using a purified system for measurement of prothrombin activation to thrombin, we demonstrated significant phospholipid concentration-dependent inhibition of prothrombin activation in the absence of beta 2GP1 by 11 consecutive patient IgG preparations. The degree of inhibition of prothrombin activation by equivalent concentrations of patient IgG correlated well with the extent of prolongation of the plasma clotting time in lupus anticoagulant assays of whole patient plasma. Additional studies with eight patient IgG preparations indicated that the addition of beta 2GP1 to patient IgG-phospholipid vesicle mixtures resulted in either independently additive inhibition by the two protein species (six cases) or potential inhibition of beta 2GP1 of the IgG inhibitory activity demonstrable in the absence of beta 2 GP1 (two cases). In addition, beta 2GP1-independent inhibition of prothrombin activation also occurred with three patient IgG preparations obtained by affinity binding to cardiolipin.

Antibodies, Anticardiolipin↗
PubMed1994

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.

Antibodies, Anticardiolipin↗
PubMed1994

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.

Animals↗