Autoantibody patterns in synovial fluids from patients with rheumatoid arthritis or other arthritic lesions

Patients with rheumatoid arthritis (RA) produce a variety of autoantibodies, not only demonstrable in the circulation, but also locally in the inflamed joint. We investigated the local production of several autoantibodies in the synovial fluid (SF) of 24 patients with RA and of 26 patients with other arthritic lesions. RA patients had higher titres of immunoglobulin M (IgM) and immunoglobulin G (IgG) rheumatoid factors (RFs) and of collagen type II antibodies in SF, whereas there were no demonstrable differences between groups with regard to antibodies against double-stranded (ds) DNA, C1q or the hapten 2,4,6-trinitrobenzene sulfonic acid (TNP). No differences were observed for total synovial levels of IgM or IgG. There was no autoantibody pattern that was typical of RA patients, except for the local presence of RF, primarily in seropositive RA patients. Our findings therefore support the notion that RF and collagen type II antibodies are induced by immunogenic material present in the local inflamed environment. In the accompanying paper we studied various synovial fluid cytokines in the same patient groups. Here we correlated the level of these cytokines with autoantibody titres in SF, but no specific cytokine associated with the production of RF was found. Hence, we conclude that several different inflammatory mediators might contribute to the chronic inflammation and autoantibody production in the joint of RA patients. An inverse correlation was established between concentrations of tumour necrosis factor-alpha (TNF-alpha) and levels of total IgG.