PROBLEM: To investigate the role of the plasma cofactor for antiphospholipid antibodies in antibody binding to endothelial cells.
METHOD OF STUDY: a) Evaluation of endothelial cell binding of polyclonal and monoclonal anti-β2 glycoprotein I antibodies; and b) study of the effects of antibody binding: adhesion molecule expression, leukocyte adhesion, and interleukin-1β secretion. RESULTS: Anti-β2 glycoprotein I antibodies bind endothelial cell monolayers in vitro by reacting with the cofactor adhered to the cell membranes. Antibody binding induces an upregulation of adhesion molecules, favours leukocyte adherence, and increases interleukin-1β secretion. Interleukin-1β plays an active role to mediate adhesion molecule expression through an autocrine loop, as shown by the inhibitory effect of interleukin 1 receptor antagonist.
CONCLUSIONS: Antiphospholipid antibodies do react with endothelium through the co-factor adhered to their cell membranes and induces a pro-adhesive cell phenotype.