ANTIENDOTHELIAL CELL ANTIBODIES TO THE ENDOTHELIAL HYBRIDOMA CELL-LINE (EAHY926) IN SYSTEMIC LUPUS-ERYTHEMATOSUS PATIENTS WITH ANTIPHOSPHOLIPID ANTIBODIES

The endothelial hybridoma (EAhy926) cell line was employed to clarify whether antiphospholipid antibodies (aPA) [lupus anticoagulant (LA), a ntiprothrombin antibody (aPT) and/or anticardiolipin antibody (aCL)] a nd antiendothelial cell antibodies (AECA) are identical, and establish whether beta(2)-glycoprotein I (beta(2)-GPI) is needed for reactivity of aPA to endothelial cells. Ig-G AECA was positive in 9/30 SLE patie nts with aPA (30.0%) and 10/22 SLE patients negative for aPA (45.5%). Ig-M AECA was positive in one SLE patient with aPA and one SLE patient without aPA. AECA-positivity was not significantly different among un fixed, TNF-stimulated and fixed EAhy926. The influence of beta(2)-GPI on the reactivity of serum to EAhy926 was minimal, and absorption expe riments of serum with cardiolipin-liposome/beta(2)-GPI or phosphatidyl serine-liposome/prothrombin gave little evidence of cross-reactivity o f aPA and AECA. The results of our study suggest that aPA and AECA may have partially cross-reacted, but were different antibodies. However, further study is needed to clarify the clinico-pathological significa nce of AECA.