In situ analysis of interleukin-6 expression at different sites of zygapophyseal joints from patients with ankylosing spondylitis in comparison to controls.

Objectives: Analysis of interleukin (IL)-6 serum levels in patients with ankylosing spondylitis (AS) has indicated that IL-6 might be a pro-inflammatory cytokine involved in AS. However, two placebo-controlled trials with monoclonal antibodies directed against the IL-6 receptor have failed to demonstrate the efficacy of the monoclonal humanized anti-human IL-6 receptor antibody over placebo for the treatment of symptoms of AS. In this study we conducted an in situ analysis of IL-6 expression at different sites of inflammation in zygapophyseal joints of patients with AS in comparison to osteoarthritis autopsy controls (CO).Method: Our immunohistochemical analysis involved 14 patients with AS, 12 autopsy controls (CO), and 11 patients with osteoarthritis (OA). Immunohistochemistry was performed to detect IL-6+ cells at five different sites: within subchondral bone marrow, fibrous tissue replacing subchondral bone marrow, hyaline cartilage, and the subchondral bone plate, and at entheseal sites.Results: Apar...