IgG anti-endothelial cell autoantibodies from patients with systemic lupus erythematosus or systemic vasculitis stimulate the release of two endothelial cell-derived mediators, which enhance adhesion molecule expression and leukocyte adhesion in an autocrine manner.

OBJECTIVE: To investigate the ability of anti-endothelial cell antibodies (AECA) to modulate endothelial cell function.
METHODS: The effects of purified IgG from 11 patients with systemic lupus erythematosus (SLE) and 4 patients with systemic vasculitis on the expression of adhesion molecules (intercellular adhesion molecule 1, vascular cell adhesion molecule 1, E-selectin) by human umbilical vein endothelial cells and on the adhesion of the human promyelocytic cell line U937 were examined in vitro.
RESULTS: IgG from 6 of 8 AECA-positive SLE patients and 3 of 3 AECA-positive systemic vasculitis patients up-regulated adhesion molecule expression and leukocyte adhesion to endothelial cells. The 4 AECA-negative samples had no effect. Transfer experiments demonstrated that at later time points (2-8 hours) after AECA addition, endothelium-derived interleukin-1 (IL-1) accounted for the ability of AECA to increase leukocyte adhesion. However, even within very short times after addition of AECA (<30 minutes), endothelial cells released a distinct transferable mediator with similar effects.
CONCLUSION: AECA in patients with SLE or systemic vasculitis may contribute to pathogenesis by increasing leukocyte adhesion to endothelial cells. AECA act by inducing the release of at least two endothelium-derived mediators, one (as-yet-unidentified) rapidly and another (IL-1) more slowly, both of which stimulate endothelial cells in an autocrine manner.