title: Relationship between anti-phospholipid and anti-endothelial cell antibodies III: beta 2 glycoprotein I mediates the antibody binding to endothelial membranes and induces the expression of adhesion molecules.
abstract: OBJECTIVE
  To investigate the role of antibodies reacting with beta 2 glycoprotein I (beta 2GPI) in the antiendothelial cell binding activity present in sera from patients with the anti-phospholipid syndrome.
  
  
  METHODS
  Sera positive for anti-phospholipid, anti-endothelial and anti-beta 2 GPI antibodies were studied for their binding activity on endothelial monolayers cultured in the presence or absence of media containing bovine serum as a source of beta 2GPI. Anti-endothelial activity was also evaluated on endothelial cells cultured without serum and supplemented with exogenous human purified beta 2GPI. Affinity purified anti-beta 2 GPI antibodies were investigated under the same experimental conditions. Finally, the effect of the incubation of these affinity purified fractions on the expression of adhesion molecules (ELAM-1) was studied.
  
  
  RESULTS
  The reactivity of the sera decreased on endothelial cells incubated in serum-free medium, while endothelial cell binding was restored in a dose dependent manner after the addition of exogenous purified human beta 2 GPI. Affinity purified anti-beta 2 GPI antibodies obtained from the same sera retained their endothelial cell binding and were able to activate endothelial cells by inducing the ex novo surface expression of adhesion molecules (ELAM-1).
  
  
  CONCLUSIONS
  These findings indicate that the close association between anti-endothelial and anti-phospholipid antibodies is sustained by antibodies which recognize beta 2 GPI adhering to the endothelial cells, and can promote their activation.
authors.affiliation: Istituto di Medicina Interna, University of Milan, Italy.
authors.forename: N
authors.initials: N
authors.lastname: Del Papa
authors.forename: L
authors.initials: L
authors.lastname: Guidali
authors.forename: L
authors.initials: L
authors.lastname: Spatola
authors.forename: P
authors.initials: P
authors.lastname: Bonara
authors.forename: M O
authors.initials: MO
authors.lastname: Borghi
authors.forename: A
authors.initials: A
authors.lastname: Tincani
authors.forename: G
authors.initials: G
authors.lastname: Balestrieri
authors.forename: P L
authors.initials: PL
authors.lastname: Meroni
mesh_terms: D017152:Antibodies, Antiphospholipid / Q000097:blood*; D016736:Antiphospholipid Syndrome / Q000276:immunology*; D001323:Autoantibodies / Q000097:blood*; D001665:Binding Sites; D015815:Cell Adhesion Molecules / Q000096:biosynthesis; D002478:Cells, Cultured; D003470:Culture Media; D019040:E-Selectin; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology*; D006023:Glycoproteins / Q000276:immunology; D006801:Humans; D066298:In Vitro Techniques; D053482:beta 2-Glycoprotein I
chemical_list: D017152:Antibodies, Antiphospholipid; D001323:Autoantibodies; D015815:Cell Adhesion Molecules; D003470:Culture Media; D019040:E-Selectin; D006023:Glycoproteins; D053482:beta 2-Glycoprotein I