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M Dueymes

Publications and source records attributed to M Dueymes.

At least 19 recordsLinked to original sources
PubMed2001

Functional heterogeneity of anti-endothelial cell antibodies.

While it has been claimed that some anti-endothelial cell antibodies (AECA) activate EC, there is also evidence that others trigger apoptosis. To address the issue of whether activation is a prerequisite for AECA-mediated apoptosis of EC, 23 AECA-positive sera were evaluated for their ability to induce activation and/or apoptosis. Activation was defined as an over-expression of E-selectin and intercellular adhesion molecule 1. Optical microscopy, annexin V binding, hypoploid cell enumeration, and determination of poly (ADP-ribose) polymerase cleavage-related products were used to assess apoptosis. Four functional profiles were defined: 10 sera promoted activation and apoptosis (act+/apo+), one was act+/apo-, six act-/apo+, and the remaining six act-/apo-. The reduced membrane expression of thrombomodulin was associated with apoptosis, rather than activation. Caspase-3 was implicated in the two models of apoptosis, the ratios of several survival proteins to Bax decreased, regardless of the ability of apo+ AECA to activate the cells, while radical oxygen species did not appear to be involved. Furthermore, it occurred that macrophages engulfed EC treated with apoptosis-promoting AECA, but not those incubated with AECA that did not induce apoptosis. Hence, AECA represent an extremely heterogeneous family of autoantibodies, not only because of the variety of their target antigens, but also the subsequent diversity of their effects.

Antibody Diversity↗
PubMed2000

Increased N-linked glycosylation leading to oversialylation of monomeric immunoglobulin A1 from patients with Sjögren's syndrome.

Increased serum immunoglobulin A (IgA) level is a common finding in primary Sjögren's syndrome (pSS). IgA might not be properly eliminated because of an abnormal glycosylation. We reported previously that IgA1 from patients with pSS was oversialylated. We extend this finding by showing that monomeric IgA1 contains more sialic acid (SA) in patients than in controls, as determined by enzyme-linked immunosorbent assay (ELISA) and Western blot with Sambucus nigra agglutinin (SNA), a lectin specific for SA. To localize this excess of SA on the N- and/or O-linked oligosaccharides, we analysed them separately, using N- and O-linked oligosaccharide profiling kits based on fluorophore-assisted carbohydrate electrophoresis. N-linked, but not O-linked, oligosaccharides of patients' IgA1 were oversialylated, and this seemed to be linked to an excess of SA on the same number of polysaccharides as normal IgA1. To localize the abnormality to the Fab and/or Fc fragments, monomeric IgA1 was digested with protease, separated and transferred to nitrocellulose, where SA was identified by SNA. Both Fab and Fc fragments appeared to be oversialylated. Oversialylation of N-linked oligosaccharides of IgA1 from patients with pSS might prevent the recognition of IgA by receptors that are responsible for their clearance, resulting in an excess of serum IgA and related immune complexes.

Adult↗
PubMed2000

Enhanced sialyltransferase activity in B lymphocytes from patients with primary Sjögren's syndrome.

Despite the indisputable role of immunoglobulin (Ig)A in the pathogenesis of primary Sjögren syndrome (pSS), the causative abnormality remains largely unknown. As an extension of our report that IgA is oversialylated in this disease, the thrust of the present study was to measure the sialyltransferase (ST) activity in B lymphocytes. ST containing lysates of B cells from 17 pSS patients and 10 controls, were obtained using a combination of detergents, and incubated with affinity purified IgA that had been previously desialylated. The deposition of cytidine 5' monophosphate sialic acid (SA) by ST from B cells onto IgA was detected by two ELISA based upon the use of biotinylated lectins (Sambucus nigra agglutinin which is specific for alpha2-6 SA and Maackia amurensis which is specific for alpha2-3 SA). In parallel, the amount of SA on IgA from ten of the 17 patients and eight of the 10 controls was assayed using the same method. An excess of alpha2-3 and alpha2-6 SA on IgA was found in those patients with excessive activity of alpha2-3 and alpha2-6 ST. Thus, IgA hypersialylation in pSS patients may result from undue activity of ST.

Adult↗
PubMed2000

False positivity in a cyto-ELISA for anti-endothelial cell antibodies caused by heterophile antibodies to bovine serum proteins.

BACKGROUND: ELISAs with fixed endothelial cells or cell lines are widely used screening tests for anti-endothelial cell antibodies (AECAs), but spurious increases occur. We examined interferences by heteroantibodies and means to eliminate them. METHODS: AECAs were measured by ELISA on fixed layers of the human endothelial cell line, EA.hy 926, in a panel of 60 patient serum samples diluted in bovine serum albumin. Heteroantibodies against fetal calf serum (FCS) proteins were demonstrated and characterized in an ELISA-the interference assay-that used FCS-coated plates and Tween 20-containing buffer as blocking agent and sample diluent, as well as by immunoblotting. RESULTS: In 12 of 60 patient serum samples, spurious increases of AECA titers were produced by endogenous antibodies reacting with FCS proteins from culture medium that were coated onto the solid-phase at the time of cell plating. This mechanism of interference was supported experimentally by exposing extracellular matrix, varying cell density, and incubating wells with FCS alone. The heterophile antibodies were mainly IgG and IgA, and in inhibition experiments, they recognized serum proteins from goat, sheep, and horse. Washing cells free of FCS before plating, or adding FCS (100 mL/L) to the patient sample diluent eliminated spurious signals from all 30 tested sera, but the latter method had practical advantages. CONCLUSIONS: Antibodies against animal serum proteins are a frequent cause of erroneous results in cyto-ELISAs. The interference can be eliminated by simple antibody absorption in FCS-containing dilution buffer.

Animals↗
PubMed1999

Glycosylation of immunoglobulin A influences its receptor binding.

Immunoglobulin A (IgA), which is heavily glycosylated, interacts with a variety of receptors, e.g. the asialoglycoprotein receptor (ASGP-R), which binds terminal galactose residues, and the Fcalpha receptor (FcalphaRI). It has thus been proposed that elevated serum levels of IgA in primary Sjögren's syndrome (pSS) are caused by its defective clearance. To test this hypothesis, we developed a method (based on sialyl transferases eluted from a hepatoma cell line) to increase the amount of sialic acid (SA) on IgA, and used a battery of IgA1- and IgA2-specific glycosidases to reduce this amount. Binding of IgA1 and IgA2 to ASGP-R and FcalphaRI was found to be sugar dependent because oversialylated IgA bound less than native or desialylated IgA. However, individual sugars did not play a direct role in this binding. Given that IgA are oversialylated in pSS, defective clearance of IgA may indeed be ascribed to an excess of SA in IgA1 and IgA2.

Acetylgalactosamine↗
PubMed1998

The binding of some human antiendothelial cell antibodies induces endothelial cell apoptosis.

The pathogenic role of antiendothelial cell antibodies (AECA) remains unclear. They are frequently associated with antibodies to anionic phospholipids (PL), such as phosphatidylserine (PS), which is difficult to reconcile with the distribution of PL molecular species within the plasma membrane. Since it is already known that PS is transferred to the outer face of the membrane as a preclude to apoptosis, the possibility exists that apoptosis is initiated by AECA. AECA-positive/anti-PL antibody-negative sera from eight patients with systemic sclerosis (SS) and 21 control patients were evaluated. Endothelial cells (EC) were incubated with AECA and the exposure of PS was established through the binding of annexin V. Hypoploid cell enumeration, DNA fragmentation, and optical and ultrastructural analyses of EC were used to confirm apoptosis. Incubation of EC with AECA derived from six of eight patients with SS led to the expression of PS on the surface of the cells. This phenomenon was significantly more frequent in SS (P < 0.04) than in control diseases. The redistribution of plasma membrane PS preceded other events associated with apoptosis: hypoploidy, DNA fragmentation, and morphology characteristic for apoptosis. Apoptosis-inducing AECA did not recognize the Fas receptor. We conclude that AECA may be pathogenic by inducing apoptosis.

Annexin A5↗
PubMed1998

Anti-endothelial cell antibody binding makes negatively charged phospholipids accessible to antiphospholipid antibodies.

OBJECTIVE: Anti-endothelial cell autoantibodies (AECA) are often associated with antibodies to anionic phospholipids (PL), such as phosphatidylserine (PS). Yet, beta2-glycoprotein I (beta2GPI)-dependent anti-PL antibodies (aPL) do not have access to their target antigens on the membrane of endothelial cells (EC). Given that AECA are capable of exposing PS and, thereby, initiating apoptosis, we explored the relationships between AECA, beta2GPI, and aPL on the surface of EC. METHODS: Human EC were incubated with mouse AECA monoclonal antibodies, and the translocation of PS was established through the binding of annexin V, which binds specifically to PS. A rabbit anti-beta2GPI antibody and biotin-conjugated F(ab')2 aPL derived from 3 patients were also used to detect beta2GPI on the cells. RESULTS: Twenty percent to 36% of the cells expressed anionic PL following incubation with AECA, as revealed by the binding of annexin V and beta2GPI. The proportion of anionic PL-expressing EC (up to 90%) correlated with the period of incubation of EC with AECA and depended on the dose of AECA. Bound aPL resided exclusively within the AECA-positive EC population. CONCLUSION: Based on our findings, AECA may be pathogenic. Some of them may even have the potential to induce production of aPL.

Animals↗
PubMed1998

Changes in glycosylation of immunoglobulins in primary Sjögren's syndrome.

Serum IgG and IgA are glycoprotein and significant glycoform abnormalities have been established in primary Sjögren's syndrome. The proportion of asialylated IgG is abnormally high in the patients, whereas IgA1 and IgA2 appear to be over-sialylated. This peculiarity might explain the defective binding of IgA to asialoglycoreceptors. Furthermore, the activity of alpha 2,6 sialyl transferase is higher in the IgA-producing B cells from the patients than in the controls, whereas the alpha 2,3 sialyl transferase operates in the former cells but not in the latter. The mechanism of this enzyme dysregulation warrants elucidation.

B-Lymphocytes↗
PubMed1997

Antiendothelial cell antibodies: useful markers of systemic sclerosis.

BACKGROUND: Systemic sclerosis (SS) encompasses a wide spectrum of clinical presentations. Antiendothelial cell antibodies (AECA) in patients with primary Raynaud's phenomenon (PRP), limited SS (lSSc), or diffuse SS (dSSc) may help to determine the long-term prognosis of the disease. METHODS: Twenty-seven normal controls, 13 patients with PRP, 36 with lSSc, and 31 with dSSc were included in the study. Sera were examined for the presence of AECA, using a cellular enzyme-linked immunosorbent assay (ELISA). Angiotensin-converting enzyme (ACE) activity, plasma von Willebrand factor antigen (vWfAg), and thrombomodulin (Tm) concentrations were also evaluated. The medical records of 50 of the lSSc and dSSc patients were reviewed and the organ system involvement noted. RESULTS: Antiendothelial cell antibodies were present in 3 patients with PRP, 16 patients with lSSc, and 26 patients with dSSc. These autoantibodies were mainly of the IgG isotype. There was no difference in ACE activity between patients and controls. In contrast, vWfAg and Tm concentrations were higher in patients with PRP relative to controls, and higher in patients with lSSc compared with those with PRP. The presence of AECA was associated with digital scars and ulcers (P < 0.004 and P < 0.003, respectively), severe RP (P < 0.01), grade 3 tortuosity of vessels (P < 0.0004), and lung involvement (P < 0.02). CONCLUSION: The significant trend for AECA to increase with disease severity across the three groups of patients studies suggests that the AECA test can identify subsets of SSc with differing prognoses.

Adolescent↗
PubMed1997

Modulation of CD72 by ligation of B cell receptor complex molecules on CD5+ B cells.

B cells expressing CD5 also carry its ligand, CD72. As an approach to understanding the role of CD5 and CD72 on B cells, we have examined the association of CD72 with CD5 and slgM by modulation/co-modulation and capping/co-capping following ligation of these surface molecules with specific antibodies. Modulation and co-modulation were measured after 24 h, whilst capping was measured after 1 h. CD5 and slgM co-modulated each other, CD72 co-modulated with slgM and CD5, but anti-CD72 did not affect either slgM or CD5. CD5 and slgM co-capped each other, whilst CD72 failed to co-cap with either slgM or CD5. The CD5-induced co-modulation of CD72 was partially blocked by specific protein tyrosine kinase inhibitor, but not the slgM-induced co-modulation, Protein kinase C (PKC) inhibitors abrogated the anti-mu- but not the anti-CD5-triggered modulation of CD72, whereas PKC activators prevented the CD5- but not the slgM-induced 24 h modulation of CD72. None of these drugs was able to modify the anti-CD72-induced modulation of CD72. Our data suggest that CD5 is physically associated with slgM in the B cell receptor complex but not with CD72. Furthermore, from the effect of drugs on modulation, there appears to be different associations of CD72 with slgM and CD5. These two pathways differed in some respects, consistent with a co-stimulatory function of CD72 and CD5 in B cell activation.

Antigenic Modulation↗
PubMed1997

The functional affinity of IgM rheumatoid factor is related to the disease duration in patients with rheumatoid arthritis.

OBJECTIVE: To determine the relevance of the functional affinity of IgM rheumatoid factor (RF) to the clinical and serological characteristics of patients with rheumatoid arthritis. METHODS: The functional affinity of IgM RF of 57 seropositive rheumatoid arthritis patients was evaluated by an enzyme linked immunosorbent assay based on the use of a chaotropic agent. The inhibition index was taken as an estimate of functional affinity. The patient group was divided into high functional affinity subgroup 1 (functional affinity < 0.5, n = 37) and low functional affinity subgroup 2 (functional affinity > 0.5, n = 20). The medical records of all patients were reviewed with a particular note of the disease activity and the articular damage score. RESULTS: The disease duration was shorter (P < 0.01) in subgroup 1 patients [7.9 (SD 6.4) years] than in subgroup 2 patients [13.4 (11.29) years], so that Ritchie's, Lee's, and Steinbrocker's indices were lower in the former than in the latter (P < 0.01, 0.001, and 0.01, respectively). In contrast, erythrocyte sedimentation rates, C reactive protein concentrations, antinuclear antibody, and HLA DR4 prevalences were similar in the two subgroups. CONCLUSIONS: Different forms of RF are present during progression of the disease.

Adult↗
PubMed1997

Association between IgM anticardiolipin antibodies and deep venous thrombosis in patients without systemic lupus erythematosus.

Patients with systemic lupus erythematosus (SLE) are at risk of developing deep venous thrombosis (DVT). Should anticardiolipin antibodies (aCL) be detectable, this risk is significantly raised, particularly when these autoanti-bodies are cofactor-dependent. We conducted a cross-sectional study of consecutive unselected outpatients referred for clinical suspicion of DVT, as an attempt to address the following questions: firstly, were aCL antibodies associated with DVT in non-SLE patients? Secondly, was this association related to the cofactor dependence? From March 1992 to February 1994, 208 patients were enrolled in the study. Venography was positive in 110 patients (DVT patients), while the diagnosis of DVT could not be confirmed in the remaining 98 (referred to as disease controls). ACL was measured by ELISA, for IgG and IgM isotypes in two ways: fetal calf serum or bovine serum albumin were used as blocking agents to distinguish between cofactor-dependent and cofactor-independent antibodies. Positive aCL was defined as optical density (OD) values greater than the 95th percentile of OD distribution of 60 healthy controls. We found a high frequency of positive IgG aCL antibodies in both DVT patients and in disease controls (25.5 vs 23.5%). We suggest an association between IgM aCL and DVT. This association was, however, not dependent on the cofactor requirement.

Aged↗
PubMed1997

IgG subclasses of human autoantibodies.

IgG comprises of four subclasses which differ from each other with respect to their biological properties. Fc gamma receptor shedding as well as a variety of T cell cytokines are influential in the distribution of these subclasses, but the route the antigen is introduced into the body is also important. With regard to nonorgan-specific autoimmune conditions, such as rheumatoid arthritis and systemic lupus erythematosus, IgG1 and IgG3 autoantibodies predominate, whereas IgG4 antibodies are regularly encountered in organ-specific autoimmune diseases. This suggests that the target organ may be continuously stimulating the immune system.

Autoantibodies↗
PubMed1996

Aberrant glycosylation of IgA from patients with IgA nephropathy.

Despite the prominent role of IgA, particularly IgA1, in the pathogenesis of IgA nephropathy (IgAN), the precise role of this molecule in the process remains unclear. Four biotin-conjugated lectins in sandwich-type enzyme-linked immunosorbent assays were devised to determine the glycosylation profiles of total IgA and its subclasses. We took advantage of differential binding properties of these lectins to sugar residues to dissect the oligosaccharide chains O-linked to the hinge and those N-linked to the Fc region of total IgA and IgA subclasses in 47 patients with IgAN and an equal number of controls. The proportion of sialylated IgA1 was higher in patients compared with controls (p < 0.02), whereas IgA2 in patients appeared less well sialylated. A reduction of galactose in pathological IgA as detected by RCA-I became significant after treatment of the molecule with neuraminidase (p < 0.01). Defective galactosylation was also observed for patient IgA1 when it was probed with ECL, a lectin that has a specificity for Gal 1,4 N-acetylglucosamine groupings on N-linked oligosaccharides. The RCA and ECL results, therefore, suggest that increased sialylation on the IgA1 is on O-linked oligosaccharides in the hinge region. This was partly confirmed by a small increase in the binding of PNA to IgA1 from the patient group. This lectin binds preferentially to Gal 1,3 N-acetylgalactosamine groups that are found on O-linked oligosaccharides.

Galactose↗
PubMed1996

Establishment and characterization of permanent human endothelial cell clones.

Though vasculitic diseases have been claimed to be associated with anti-endothelial cells antibodies (AECA), there is a widespread awareness of the limitations of the tests currently in use. Our objective was therefore to establish clones, in the hope that some of them would express disease-specific membrane autoantigens. Two EC lines and 7 clones were established by fusing human umbilical vein EC with epithelial A549/8 cells, and cloning by limiting dilution. An additional clone was derived from the EA.hy 926 cell line. All clones carried EC markers, such as thrombomoduline (TM) and platelet-EC adhesion molecule 1 but differed from each other, depending on whether they expressed HLA class II antigen, LFA-1, thrombospondin receptor or von Willebrand factor (vWf) antigen. Clones were also characterized by their ability to release tissue plasminogen activator, interleukin 6, TM and vWf. This panel is meant to distinguish reactivities of AECA.

Antibodies, Monoclonal↗
PubMed1996

Do some antiphospholipid antibodies target endothelial cells?

Anti-endothelial cell activity is partly due to antiphospholipid antibodies (aPLA) because: a) the two types of antibodies are present in patients with connective tissue diseases and cardiolipin-binding monoclonal antibodies recognize endothelial cells (EC); b) anionic phospholipids are detectable on the outer face of the EC membrane lipid bilayer and an anti-beta 2-glycoprotein I (beta 2-GPI) monoclonal antibody binds to EC; c) the binding of aPLA to EC and the functional affinity of this binding are dependent on the presence of beta 2-GPI; d) anti-EC antibodies trigger the expression of anionic phospholipids on the outer leaflet of the EC membrane.

Antibodies, Antiphospholipid↗