HMGB1 and Arthritis: Previous work has shown that cytoplasmic HMGB1 protein is detectable in synovial macrophages and dendritic cells in male rats subjected to collagen-induced arthritis.36 Translocation of HMGB1 from nucleus to cytoplasm is an indicator of release, thus macrophages and dendritic cells are potential sources of HMGB1 in conditions with joint inflammation.