Increased Expression of Interferon (Ifn)-Gamma Together With Ifn-Gamma Receptor in the Rheumatoid Synovial Membrane Compared With Synovium of Patients With Osteoarthritis

Abstract

Data concerning the presence of T-cell-derived cytokines in the rheumatic joint are conflicting, challenging the hypothesis that rheumatoid arthritis (RA) is a T-cell-mediated disease. In this study synovial tissue specimens of 11 patients with RA and eight patients with osteoarthritis (OA) were stained for interferon-gamma (IFN-gamma) and its receptor. The level of expression of IFN-gamma was compared with that in tissue specimens of delayed-type hypersensitivity (DTH) reactions of the skin and of chronic tonsillitis. Furthermore, the percentage of T-lymphocytes which stained positive for IFN-gamma was determined using double staining techniques. IFN-gamma and its receptor were detected in all patients with RA and in 7/8 and 3/8, respectively, of patients with 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 in RA synovial tissue, the level of expression was less when compared with DTH reactions of the skin and tonsillitis. The percentage of CD3+ cells being positive for IFN-gamma was approximately 1% in RA, whereas in DTH reactions of the skin it was >90% and in tonsillitis approximately 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 immunological reaction of the inflamed joint.

Immunohistochemical Detection of Interferon-γ: Fake or Fact?

“…Apart from staining of various cellular constituents, 12 of 13 anti-IFN␥ antibodies revealed staining of a CD138-positive plasma cell subset (Figure 4) but not of T-cells. Non-T-cell positivity with anti-IFN␥ antibodies has been reported previously and is considered a result of receptor-bound IFN␥ (Dolhain et al 1996). Indeed, some of the IFN␥ staining patterns resemble the IFN␥ receptor staining pattern ( Figure 1J).…”

“…For example, anti-IFN␥ clone MD-2 was first described for ELISA application by Van der Meide et al (1985) and only much later was applied for immunohistochemical purposes (Hoefakker et al 1993). The latter application is subsequently cited by other investigators and has led to the use of this antibody on tissue sections (Dolhain et al 1996;Thepen et al 1996;Van Hoffen et al 1996;Smeets et al 1998b).…”

“…Apparently, immunocytochemical staining of intact T-cells is not a reliable model system for testing the immunohistochemical applicability of IFN␥ antibodies on cryostat tissue sections, as has been suggested in the literature Dolhain et al 1996).…”

“…Not only may the IFN␥ antibodies themselves may play a role but also the application of different tissue fixatives before the IFN␥ staining procedure may have an effect on the final staining result. For example, acetone fixation was employed by Hoefakker et al (1993), Dolhain et al (1996), Smeets et al (1998b), and Thepen et al (1996), whereas PFA fixation and saponin treatment were used by Ulfgren et al (1995), Smeets et al (1998a), and . In our hands, a comparison of these two popular fixatives showed a dramatic loss of IFN␥ staining after acetone fixation of intact T-cells ( Figures 3D and 3E), confirming the use of PFA fixation as indicated by .…”

Functional CD40 ligand is expressed by T cells in rheumatoid arthritis.

“…Many cytokines produced by activated T cells, such as IFN-␥ , IL-2, and IL-4, are either absent or found at low levels within the rheumatoid synovium (19)(20)(21). Furthermore, treatments directed against CD4 ϩ T cells, such as thoracic duct drainage and cyclosporine and mAb therapies, have provided inconsistent benefit in chronic RA (22)(23)(24)(25).…”