This study was undertaken in an effort to understand the role of cytokines in T lymphocyte trafficking into inflamed synovium and in the potential enhancement of antigen presentation by human synovial fibroblasts. We found that interleukin-lp (IL-lp), tumor necrosis factor a (TNFa), and interferon-y (IFNy) each increased the cell surface expression of intercellular adhesion molecule I (ICAM-I) on human synovial fibroblasts in a dose-and time-dependent manner. Maximal ICAM-1 expression occurred within 8 hours of induction, with the following order of efficacy: IFNy > TNFa > IL-1p. The number of cells bearing the ICAM-1 antigen also increased, from a basal level of -30% to more than 83% after cytokine induction (for all 3 cytokines). ICAM-1 expression rapidly decreased fdlowing cytokine removal. The expression of lymphocyte function-associated antigen 3 was also examined, but it was not changed by any of the 3 cytokines. Class I major histocompatibility complex antigen expression was increased modestly by all 3 cytokines, and expression was maximal by 24 hours after treatment. Only IFNy induced HLA class I1 antigen expression, and this expression persisted for up to 6 days following removal of the lymphokine. IL-6 and granulocyte-macrophage colony- stimulating factor had no effect on any of the parameters examined. Our data support an interactive role for inflammatory cytokines and the expression of adhesion ligands and HLA antigens by human synovial fibroblasts in the pathogenesis of synovial inflammation in rheumatoid arthritis.Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease characterized in part by the proliferation of pannus tissue in diseased joints, which leads to eventual degradation of the articular cartilage and the subchondral bone (1)(2)(3). It has been demonstrated that the RA synovium contains cells that express HLA-DR antigens (4-7). There is also evidence that indicates that cells populating the inflamed tissue lining the RA joint have adhesion molecules as ligands for homing receptors on circulating T lymphocytes (8,9). It is hypothesized that the increased adhesiveness of the inflamed synovial tissue may play a central role in lymphocyte homing and retention in the diseased joint. The current study was initiated in an effort to elucidate cellular mechanisms that may be involved in chronic inflammatory synovitis. We examined the time and dose effects of various cytokines present in the inflammatory microenvironment in RA (10) on the expression of adhesion ligands intercellular adhesion molecule I (ICAM-1) and lymphocyte function-associated antigen 3 (LFA-3), and the expression of class I and class I1 major histocompatibility complex (MHC) antigens, 4 fibroblast cell surface molecules whose regulation may play critical roles in synovial inflammation.In previous studies, interferon-y (IFNy) has been shown to induce the expression of class I1 MHC antigens on synovial fibroblasts (1 l), and ICAM-1 has
MATERIALS AND METHODSRecombinant cytokines and antibodies. Recombinant human i...