High levels of osteoprotegerin and soluble receptor activator of nuclear factor kappa B ligand in serum of rheumatoid arthritis patients and their normalization after anti-tumor necrosis factor alpha treatment.

Objective: To test the hypotheses that 1) proinflammatory cytokines affect osteoprotegerin (OPG) and soluble receptor activator of nuclear factor kappa B ligand (sRANKL) production and therefore the OPG and sRANKL levels differ in rheumatoid arthritis (RA) patients in comparison with healthy individuals; and 2) anti-tumor necrosis factor alpha (anti-TNF alpha) therapy influences OPG and sRANKL levels.

Methods: Sera were obtained from healthy individuals or RA patients receiving the combination of infliximab and methotrexate. Peripheral blood mononuclear cells (PBMCs) and synovial fluid mononuclear cells (SFMCs) were isolated from RA patients.

High levels of IL-17 in rheumatoid arthritis patients: IL-15 triggers in vitro IL-17 production via cyclosporin A-sensitive mechanism.

Recent data suggest that IL-15 plays an important role in the pathogenesis of rheumatoid arthritis. In the present study, we hypothesized that elevated in the joints of rheumatoid arthritis, but not osteoarthritis, patients, IL-15 may exert its proinflammatory properties via the induction of IL-17, a cytokine known to stimulate synoviocytes to release several mediators of inflammation including IL-6, IL-8, GM-CSF and PGE2. To test this hypothesis, we first measured the levels of IL-17 and IL-15 using specific ELISA and found that synovial fluids of patients with rheumatoid arthritis, but not with osteoarthritis, contain high levels of these cytokines.