TLR4 and IL-1RI, the reciprocal signalling receptors for the HMGB1 complex partner molecules LPS, IL-1α and IL-1β, were expressed on synovial fibroblasts from both RA (RASFs) and OA (OASFs) patients as demonstrated by immunofluoresencent staining. Here, HMGB1 is linked to rheumatoid arthritis.