HMGB1 and arthritic joint disease: Four proteases associated with arthritis, neutrophil-derived human elastase (HNE) and Cathepsin G (CG), fibroblast-derived matrix metalloproteinase 3 (MMP-3) and the serine protease dipeptidyl peptidase-IV (DPP-IV), were investigated for their ability to process HMGB1.