TXN and rheumatoid arthritis: Serum and plasma Trx1 levels were found to be elevated in RA compared with healthy subjects.21, 22, 27 Moreover, the synovial fluid of RA patients revealed higher Trx1 concentrations than those of osteoarthritis.22, 27 In addition, it was also demonstrated that RA disease activity correlated with elevated Trx1 plasma levels22 and Trx1 activity.23 The high concentration of Trx1 described for RA patients in particular21 might be associated with the hyporesponsiveness of T cells in RA patients.20