Synovial inflammation is often associated with systemic changes, such as increased levels of acute phase proteins and hypergammaglobulinemia, which cannot be explained by the cytokines described in synovial fluids and synoviocyte secretions. Interleukin 6 (IL-6) has recently been characterized as a mediator of multiple inflammatory responses. This cytokine promotes T and B lymphocyte growth and differentiation, and acute phase protein synthesis. We therefore examined IL-6 production by human synoviocytes and its presence in synovial fluids. In vitro, synoviocytes spontaneously released IL-6, which was increased by IL-1 and tumor necrosis factor-alpha. Synoviocyte-derived IL-6 activity was able to induce hybridoma-plasmacytoma proliferation, and immunoglobulin and acute-phase protein synthesis. The synovial fluids from patients with diverse arthropathies contained IL-6 activity, but higher levels were present in inflammatory arthropathies than in osteoarthritis. These results demonstrate that synoviocytes are a potent source of IL-6, which can contribute to important manifestations of inflammatory arthropathies.
P A Guerne, B L Zuraw, J H Vaughan, D A Carson, M Lotz
Guidelines: The Editorial Board will only consider letters that we deem relevant and of interest to our readers. We will not post data that have not been subjected to peer review, nor will we post letters that are essentially a reiteration of another letter. All accepted letters will be posted on our website within one week of acceptance. We reserve the right to edit any letter for length, content, and clarity. Authors of all accepted letters will be asked to preview any changes. Authors will be notified by e-mail if their letters were not accepted. As this is a final decision, no appeals will be considered.
Specific requirements: All letters must be 400 words or fewer. You may enter the letter as plain text or HTML. The author's name and e-mail address are required, and will be posted with the letter. All possible conflicts of interest must be noted, even if they are not posted. If you wish to include a figure (keep in mind that non-peer-reviewed data will not be posted), please contact the editors directly at firstname.lastname@example.org.