title: Heterogeneous recognition of beta 2-glycoprotein I by antibodies from antiphospholipid syndrome patients.
abstract: Beta 2-glycoprotein I plays a pivotal role in the binding of antiphospholipid antibodies to phospholipid in patients with antiphospholipid syndrome. In this study the nature of the epitopes on beta 2-glycoprotein I (beta2-GPI) recognised by sera from antiphospholipid syndrome (APS) patients (n = 15) was investigated and compared to rabbit polyclonal and mouse monoclonal anti-beta2-GPI antibodies. beta2-GPI was only recognised when bound to a high affinity binding support. The antigenic epitope on beta2-GPI recognised by all APS patients was also dependent on disulphide bond integrity. Digestion of beta2-GPI with elastase rapidly destroyed the epitope(s) on beta2-GPI recognised by antibodies in 91% of APS patients. The main cleavage occurred at tryptophan316-lysine317 in the fifth domain. Digestion with staphylococcal V8 protease resulted in a 50% reduction in antibody binding in 81% of patients and the cleavage sites mainly involved the first domain of the molecule. There was considerable variability in the recognition of six different species of beta2-GPI by serum from APS patients. The epitopes on beta2-GPI bound by APS sera appear conformationally determined in all patients but are quite heterogeneous in the regions of beta2-GPI that are recognised.
authors.affiliation: Department of Immunology, St. James's Hospital, Dublin, Ireland.
authors.forename: J
authors.initials: J
authors.lastname: Guerin
authors.forename: R
authors.initials: R
authors.lastname: Sim
authors.forename: B B
authors.initials: BB
authors.lastname: Yu
authors.forename: J
authors.initials: J
authors.lastname: Ferluga
authors.forename: C
authors.initials: C
authors.lastname: Feighery
authors.forename: J
authors.initials: J
authors.lastname: Jackson
mesh_terms: D000327:Adsorption; D000818:Animals; D000906:Antibodies / Q000097:blood* / Q000737:chemistry; D000915:Antibody Affinity / Q000187:drug effects; D000918:Antibody Specificity / Q000187:drug effects; D016736:Antiphospholipid Syndrome / Q000276:immunology*; D004220:Disulfides / Q000378:metabolism; D004229:Dithiothreitol / Q000378:metabolism; D000939:Epitopes / Q000737:chemistry / Q000187:drug effects; D006023:Glycoproteins / Q000737:chemistry* / Q000276:immunology*; D006801:Humans; D051379:Mice; D010447:Peptide Hydrolases / Q000378:metabolism; D011487:Protein Conformation / Q000187:drug effects; D011489:Protein Denaturation / Q000276:immunology; D011817:Rabbits; D012997:Solvents / Q000494:pharmacology; D013045:Species Specificity; D013499:Surface Properties; D053482:beta 2-Glycoprotein I
chemical_list: D000906:Antibodies; D004220:Disulfides; D000939:Epitopes; D006023:Glycoproteins; D012997:Solvents; D053482:beta 2-Glycoprotein I; D010447:Peptide Hydrolases; D004229:Dithiothreitol