INCREASED LEVELS OF LEUKEMIA INHIBITORY FACTOR IN SYNOVIAL-FLUID FROM PATIENTS WITH RHEUMATOID-ARTHRITIS AND OTHER INFLAMMATORY ARTHRITIDES

Objective. To examine svnovial fluid (SF) from patients with arthritis, for the presence of the cytokine leukemia inhibitory factor (LIF). Methods. SF from 152 subjects was examined for LIF, using a radioreceptor competition assay. Results. LIF was present at concentrations of 1-43 ng/ml in the SF of 23% of patients with rheumatoid arthritis (RA) or other inflammatory or infectious arthritides but in only 1 of 29 patients with osteoarthritis (P < 0.01). In the RA patients, the SF LIF concentration correlated significantly with the peripheral blood white blood cell count (WBC) (P < 0.05) and the SF WBC count (P < 0.01), but not with other clinical or radiologic parameters of disease activity or progression. Conclusion. LIF is implicated as a potential mediator of the local or systemic inflammatory response or the joint destruction seen in inflammatory arthritis.