CXCL12 and rheumatoid arthritis: Monocytes from RA patients with active disease migrate towards the CXCL12/HMGB1 heterocomplex formed at lower HMGB1 concentration, compared to monocytes obtained from healthy individuals, due to the production of thioredoxin and thioredoxin reductase, enzymes implicated in maintaining HMGB1 in its reduced form (35).