Tryptase is a candidate autoantigen in rheumatoid arthritis

Autoimmune processes have been implicated in the development of rheumatoid arthritis (RA); however, specific autoantigens that play a role in the aetiology of RA have been lacking. In this study, we found that sera from RA patients were particularly immunoreactive against the protein tryptase. Compared with osteoarthritis (OA) patients and healthy controls, RA patients had relatively higher levels of tryptase and concomitant anti-tryptase antibodies in their synovial tissues and sera. Similarly, synovial fluid from RA patients, but not from OA patients, contained antibodies that recognized tryptase in vitro. In addition, serum tryptase levels in both early and late RA patients significantly correlated with clinical indices usually used to diagnose RA, such as rheumatoid factor, Disease Activity Score using 28 joint counts and autoantibodies against cyclic citrullinated peptide. Our results identify tryptase as a candidate autoantigen involved in the pathogenesis of RA and monitoring its levels may have diagnostic and prognostic value.