To investigate the prevalence of antiepithelial cell antibody (AECA) in systemic vasculitis (SV) and the target antigen thereof.
Sera of 113 patients with SV of different kinds, 46 patients with Behcet's disease, 23 patients with Takayasu arteritis, 19 patients with Wegener's granulomatosis, 8 patients with polyarteritis nodosa, 7 patients with microscopic polyangiitis, and 10 patients with Churg-Strauss syndrome were collected to detect the protein expression of AECA by Western blotting, with the protein of the endothelial cells of the line EA. hy926 line as substrate. Two-dimensional electrophoresis combined with immunoblotting, liquid chromatography-electrospray ionization mass spectrography was used to detect the target antigens related to vasculitis. Sera of 57 patients with systemic lupus erythematosus (SLE), 25 patients with rheumatoid arthritis (RA), and 20 healthy persons were collected as controls.
The AECA-positive rate of the SV patients was 69.0%, not significantly different from that of the SLE patients (66.7%), but significantly higher than those of the RA patients (6.7%, P < 0.01) and healthy persons (0, P < 0.01). The AECA from the SV patients reacted with the endothelial cell (EC) antigens with the molecular size of 26 to 125 kDa, and the AECA from the SLE patients reacted with the EC antigens with the molecular size of 15 to 97 kDa. The EC antigens with the molecular size of 47 kDa was commonly found in the sera of the AECA-positive SV patients and SLE patients, however, was not found in the RA, and polymyositis-dermatomyositis patients. The EC protein reacted by 47 kDa protein was identified by proteomic techniques as alpha-enolase.
A group of heterogeneous antibodies, AECA can be found frequently in patients with SV and SLA. AECA reacts against a common EC antigen, alpha-enolase.