Autoantibodies to glucose‐6‐phosphate isomerase are elevated in the synovial fluid of rheumatoid arthritis patients

Abstract

Objective: This study investigated whether anti‐glucose‐6‐phosphate isomerase (GPI) antibody in the synovial fluid is specifically related to human rheumatoid arthritis (RA).Methods: Synovial fluid was collected from patients with RA, osteoarthritis (OA), gout, Behcet's disease, or ankylosing spondylitis. GPI‐binding activity was measured in the synovial fluid using a surface plasmon resonance (SPR) biosensor.Results: The mean level of anti‐GPI signal in the synovial fluid of RA patients was significantly elevated compared with that of OA patients (2.84±1.41 AU versus 1.19±0.42 AU, respectively; p<0.0001). Anti‐GPI signals in the synovial fluids of patients with non‐rheumatoid arthritis, such as gout, Behcet's disease, or ankylosing spondylitis were significantly lower than in the synovial fluid of RA patients (p<0.005), and were similar to those of OA patients.Conclusion: Our study indicates that anti‐GPI antibody in the synovial fluid is specifically related to RA, and suggests that GPI and its autoantibody might be important in the pathogenesis of human RA.