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Antiphospholipid antibody binding to bilayer-coated glass microspheres
A R Obringer1, N S Rote, A Walter
1Department of Microbiology and Immunology, Wright State University School of Medicine, Dayton, OH 45435, USA.
Journal of Immunological Methods
|September 11, 1995
Summary
Antiphospholipid antibodies (aPLs) targeting cardiolipin or phosphatidylserine are linked to thrombosis. This study reveals aPLs bind to phospholipid bilayers, with some antibodies recognizing antigens on activated platelets and cells, suggesting new insights into antiphospholipid syndrome.
Area of Science:
- Immunology
- Biochemistry
- Pathology
Background:
- Antiphospholipid antibodies (aPLs) are associated with thrombosis, recurrent fetal loss, and thrombocytopenia.
- Enzyme-linked immunosorbent assays (ELISAs) are standard for detecting aPLs, but antigen presentation in ELISAs is not fully understood.
- The specific binding of aPLs to phospholipid bilayers and their potential targets in vivo remain areas for investigation.
Purpose of the Study:
- To determine the specificity of three mouse monoclonal antiphospholipid antibodies (aPLs) for phospholipid bilayer membranes.
- To investigate the binding characteristics of aPLs to cardiolipin (CL) and phosphatidylserine (PS) in a bilayer model.
- To explore the potential in vivo binding sites of aPLs on cellular membranes.
Main Methods:
- Formation of phospholipid bilayers (varying percentages of PS or CL in phosphatidylcholine) on glass microspheres.
- Analysis of monoclonal aPL binding to these bilayers using flow cytometry.
- Investigation of binding as a function of ionic strength to elucidate intermolecular forces.
Main Results:
- Two monoclonal aPLs (BA3B5C4 and 3SB9b) bound specifically to both PS- and CL-containing bilayers, with binding increasing with higher anionic phospholipid content.
- These antibodies showed binding thresholds at 20 mol% PS and below 25 mol% CL, and binding was primarily mediated by electrostatic interactions.
- A third antibody (D11A4) showed restricted binding to 100% PS or 100% phosphatidylcholine bilayers, not binding to CL-containing bilayers.
Conclusions:
- The epitope conformation of CL and PS in bilayer membranes may differ from that presented in standard ELISAs.
- Two of the tested aPLs bound to bilayers at PS concentrations found on activated platelets, apoptotic lymphocytes, and senescent red blood cells.
- These cellular surfaces represent plausible sites for pathologically relevant aPL interactions in antiphospholipid syndrome.