INCREASED EXPRESSION OF INTERFERON (IFN)-GAMMA TOGETHER WITH IFN-GAMMA RECEPTOR IN THE RHEUMATOID SYNOVIAL-MEMBRANE COMPARED WITH SYNOVIUM OF PATIENTS WITH OSTEOARTHRITIS

Data concerning the presence of T-cell-derived cytokines in the rheuma tic joint are conflicting, challenging the hypothesis that rheumatoid arthritis (RA) is a T-cell-mediated disease. In this study synovial ti ssue specimens of 11 patients with RA and eight patients with osteoart hritis (OA) were stained for interferon-gamma (IFN-gamma) and its rece ptor. The level of expression of IFN-gamma was compared with that in t issue specimens of delayed-type hypersensitivity (DTH) reactions of th e skin and of chronic tonsillitis. Furthermore, the percentage of T-ly mphocytes which stained positive for IFN-gamma was determined using do uble staining techniques. IFN-gamma and its receptor were detected in all patients with RA and in 7/8 and 3/8, respectively, of patients wit h OA. Expression of IFN-gamma (P < 0.02) and IFN-gamma receptor (P < 0 .01) in synovial tissue of patients with RA was more abundant compared with that in patients with OA. Although IFN-gamma could be detected i n RA synovial tissue, the level of expression was less when compared w ith DTH reactions of the skin and tonsillitis. The percentage of CD3 cells being positive for IFN-gamma was similar to 1% in RA, whereas i n DTH reactions of the skin it was >90% and in tonsillitis similar to 30%. We conclude that the presence of IFN-gamma and its receptor in RA synovial tissue suggests a role for this cytokine in the ongoing immu nological reaction of the inflamed joint.