A novel autoantibody against fibronectin leucine-rich transmembrane protein 2 expressed on the endothelial cell surface identified by retroviral vector system in systemic lupus erythematosus Full Text
Arthritis Research & Therapy, 07/03/2012
Shirai T et al. – The authors identified the membrane protein fibronectin leucine–rich transmembrane protein 2 (FLRT2) as a novel autoantigen of Anti–endothelial cell antibodies (AECA) in systemic lupus erythematosus (SLE) patients using the retroviral vector system. Anti–FLRT2 antibody has the potential to induce direct endothelial cell cytotoxicity in about 10% of SLE patients and could be a novel molecular target for intervention. Identification of such a cell surface target for AECA may reveal a comprehensive mechanism of vascular injury in collagen diseases.Methods
- AECA activity in sera from patients with collagen diseases was measured by flow cytometry using human umbilical vein endothelial cells (HUVEC).
- A cDNA library of HUVEC was retrovirally transfected into a rat myeloma cell line, from which AECA–positive clones were sorted by flow cytometry.
- cDNA of the cells was analyzed to identify an autoantigen, then the clinical characteristics and the functional significance of the autoantibody was evaluated.
- Two distinct AECA–positive clones were isolated using serum immunoglobulin G (IgG) from a patient with systemic lupus erythematosus (SLE).
- Both clones were identical to cDNA of fibronectin leucine–rich transmembrane protein 2 (FLRT2).
- HUVEC expressed FLRT2 and the prototype AECA IgG bound specifically to FLRT2–transfected cells.
- Anti–FLRT2 antibody activity accounted for 21.4% of AECA in SLE.
- Furthermore, anti–FLRT2 antibody induced complement–dependent cytotoxicity against FLRT2–expressing cells.