Identification of target antigens of anti-endothelial cell and anti-vascular smooth muscle cell antibodies in patients with giant cell arteritis: a proteomic approach
AIM The prevalence of anti-endothelial cell autoantibodies (AECA) in patients with anti-neutrophil cytoplasmic autoantibody-associated systemic vasculitis (ASV) has been reported by several groups with conflicting results ranging from 8% to 100%. Types of substrate cells used for AECA testing partially explain this variation. Endothelial cells from kidney origin have been reported to be predominant in AECA binding. Therefore, we investigated AECA prevalence using a human glomerular endothelial cell line compared with primary human umbilical vein endothelial cells, which have frequently been used for AECA detection. METHODS Sera from 43 ASV patients (29 Wegener's granulomatosis (WG), 14 microscopic polyangiitis (MPA)) with active disease were assessed for AECA positivity using cell-based enzyme-linked immunosorbent assay. Forty serum samples from healthy controls were tested in parallel. To evaluate endothelial activation levels, soluble intercellular cell adhesion molecule-1 and vascular cell adhesion molecule-1 were measured with capture enzyme-linked immunosorbent assay. RESULTS The AECA were detected in 4 of 29 WG patients (14%), but none of 14 MPA patients was positive for AECA using glomerular endothelial cell as a substrate, whereas AECA were positive in 10% of WG patients and 14% of MPA patients on human umbilical vein endothelial cells. No significant differences were found between ASV patients and controls in AECA test. Serum levels of vascular cell adhesion molecule-1 and soluble intercellular cell adhesion molecule-1 in ASV patients were significantly higher than in controls. However, there were no differences between AECA-positive and -negative patients for both of the activation markers. CONCLUSION The AECA, directed against glomerular endothelial cells, have a low prevalence in ASV patients with active disease and are not correlated with endothelial activation.