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.
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.
Del Papa
N
N
Istituto di Medicina Interna, University of Milan, Italy.
Guidali
L
L
Spatola
L
L
Bonara
P
P
Borghi
M O
MO
Tincani
A
A
Balestrieri
G
G
Meroni
P L
PL
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
D017152:Antibodies, Antiphospholipid; D001323:Autoantibodies; D015815:Cell Adhesion Molecules; D003470:Culture Media; D019040:E-Selectin; D006023:Glycoproteins; D053482:beta 2-Glycoprotein I