ELEVATED FACTOR-J LEVELS IN SYNOVIAL-FLUID FROM PATIENTS WITH INFLAMMATORY ARTHROPATHIES

Factor J (FJ) is a complement inhibitor that is able to regulate in vi tro both the classical and alternative human complement pathways. In t he search of its biological significance, we have analyzed FJ levels i n synovial fluid from patients with different arthropathies, in which IL-6 levels had been previously measured. The pathologies included in this study were: rheumatoid arthritis (RA) (n = 21), crystal depositio n diseases (CDD) (n = 6), osteoarthritis (OA) (n = 23), spondyloarthri tis (SpA) (n = 3) and other inflammatory arthropathies (OIA) (n = 4). We found a good correlation between IL-6 and FJ levels (r = 0.33, p = 0.0132) in the 57 processed samples. Synovial fluids had high levels o f IL-6 (median: 3000 pg/ml). Besides, we found that FJ levels were ele vated (241 +/- 429 mu g/ml) when compared with NHS (5.32 +/- 2.82 mu g /ml). Considering OA patients as control group for non-inflammatory si tuation, we found that FJ levels were significantly elevated in inflam matory patients only if RA patients were excluded. Furthermore, there were also significant differences with CDD patients. In addition, we h ave examined the presence of this inhibitor in synovial fluid by Weste rn blot after running gels at acid pH and electrophoretical transferen ce at the same pH. In these experiments, we evidenced the presence of a cationic protein immunoreactive with polyclonal and monoclonal anti- FJ antibodies. In conclusion, FJ levels are elevated in pathological s ynovial fluids. FJ could be an acute phase reactant as other molecules present in the synovial fluid, or could be shed from extracellular ma trix as a consequence of the high enzymatic activity present in the ar ticular fluid or as a response to the inflammatory stimulus. (C) 1997 Elsevier Science B.V.