Auto-antibodies to vascular endothelial cadherin in humans: association with autoimmune diseases

To identify patients with autoimmune diseases who are at high risk of developing vascular cell dysfunction, early biomarkers must be identified. This study was designed to detect and characterize circulating autoantibodies to VE-cadherin (AAVEs) in patients with early-stage autoimmune diseases. An enzyme-linked immunosorbent assay (ELISA) was developed to capture autoantibodies, using a recombinant human VE-cadherin fragment covering the extracellular domains as a target antigen. AAVEs specificity for the target antigen was confirmed by western blotting. Basal AAVEs levels were determined for healthy donors (n=75). Sera from patients (n=100) with various autoimmune diseases, including rheumatoid arthritis (n=23), systemic lupus erythematosus (SLE, n=31), systemic sclerosis (n=30), and Behçet's disease (BD, n=16) were also tested. Levels of AAVEs were significantly higher in rheumatoid arthritis (P<0.0001), SLE (P<0.05), and BD (P<0.05) populations than in healthy subjects. Purified immunoglobulin G (IgG) from a BD patient with exceptionally high AAVEs levels recognized the EC1-4 fragment in western blots. Further characterization of the epitopes recognized by AAVEs showed that BD patients had antibodies specific for the EC3 and EC4 domains, whereas SLE patients preferentially recognized the EC1 fragment. This suggests that distinct epitopes of human VE-cadherin might be recognized in different immune diseases. Purified IgG from BD patients was found to induce endothelial cell retraction, redistribution of VE-cadherin, and cause the formation of numerous intercellular gaps. Altogether, these data demonstrate a potential pathogenic effect of AAVEs isolated from patients with dysimmune disease. This is the first description of AAVEs in humans. Because regions EC1 and EC3-4 have been shown to be involved in homophilic VE-cadherin interactions, AAVEs produced in the course of dysimmune diseases might be specific biomarkers for endothelial injury, which is part of the early pathogenicity of these diseases.