Objectives: To quantify the T-helper type (Th) 1 cytokine interferon gamma (IFN-gamma)-positive and the Th2 cytokine interleukin (IL)-4-positive cells in synovial fluid (SF) and synovial membrane (SM) at the single-cell level in rheumatoid arthritis (RA) in comparison to reactive arthritis (ReA), and to manipulate the cytokine pattern of RA patients in vitro.
Methods: Eighteen patients with RA and 17 with ReA were studied. For intracellular staining of cytokines, SF mononuclear cells (MNC) from seven patients with RA, in comparison to eight patients with ReA, were triple stained with anti-IFN-gamma, IL-4 and anti-CD4 or anti-CD8 monoclonal antibodies (mAb) and analysed by flow cytometry. Furthermore, in 13 patients with RA, immunohistology of SM was performed and compared with seven ReA patients. In addition, in six of the RA patients, synovial T cells were grown over 3 weeks in the presence of various cytokines and intracellular cytokine staining analysed by flow cytometry weekly.
Results: In SF, the mean percentage of IFN-gamma+/CD4+ T cells in RA was almost 4-fold higher than the number of IL-4+/CD4+ T cells (11.3+/-5 vs 3.02+/-1.04; P=0.0012), while the ratio of IFN-gamma/IL-4+ CD4+ T cells was only 1.59 in ReA (P=0.047 for the ratio difference). A similar result was obtained for SM: the ratio of IFN-gamma/IL-4+ cells in RA was 4.3 (P<0.0001 for the IFN-gamma/IL-4 difference), but only 1.2 for ReA (P=0.02 for the ratio difference). Of the CD3+ cells in SM, 2.8% were positive for IFN-gamma and 0.4% for IL-4 in three RA patients. A decrease in the number of IFN-gamma-positive SF T cells and an increase in the number of IL-4-positive SF T cells could be achieved in vitro through IL-4, but not by IL-10 or transforming growth factor beta.
Conclusions: The Th1 pattern in the joint of RA patients demonstrated at the single-cell level may be important for the pathogenesis of RA and may provide a target for future immunotherapy. Our data suggest a therapeutic role for IL-4.