Increased synovial fluid levels of interleukin-12, sCD25 and sTNF-RII/sTNF-RI ratio delineate a cytokine pattern characteristic of immune arthropathies.

The assessment of cytokines and their soluble receptors in the synovial fluid (SF) of inflammatory arthropathies may be useful in studying pathogenetic and immunoregulatory mechanisms underlying different diseases. The aim of this work was to study the cytokine network occurring in inflammatory arthropathies and to identify a cytokine profile which is characteristic of an immune-mediated synovitis. Levels of IL-12, as well as IL-4, IL-8, IL-10, IFN-gamma, sCD25, TNF-alpha and its soluble receptors were measured in the SF of various arthropathies, i.e. non-inflammatory arthropathies: "control" meniscus pathology (n = 21), osteoarthritis (n = 22) and chronic crystal arthritis (n = 9); a non-immune inflammatory arthropathy: acute crystal arthritis (n = 11); 2 immune inflammatory arthropathies: reactive arthritis (ReA) (n = 23) and rheumatoid arthritis (RA) (n = 44). SF levels of IL-10, TNF-alpha and sTNF-RII were found to be increased in the three inflammatory arthropathies compared to the "control" meniscus group. Within the inflammatory group, acute crystal arthritis was characterized by a significantly higher sTNF-RI/TNF-alpha ratio and ReA by a significantly lower sTNF-RII/TNF-alpha ratio compared to the two other diseases. The two immune arthropathies, RA and ReA, were characterized by increased SF levels of IL-12, sCD25 and of the sTNF-RII/sTNF-RI ratio. ReA differed however from RA by showing lower IL-8 and IL-4 levels, higher IFN-gamma levels and a higher IL-12/IL-10 ratio, suggesting a more prevalent Th1 profile in ReA SF. Our data indicate that the measurement of SF cytokines and soluble receptors may discriminate between each inflammatory arthropathy and might be useful in clinical practice.