Capacity to solubilize immune complexes in sera and synovial fluids from patients with rheumatoid arthritis

Fifty-six sera and 33 synovial fluids from rheumatoid arthritis patients were studied to evaluate their capacity to solubilize immune complexes. A decreased function was found in 65% of rheumatoid synovial fluids when compared with 13 osteoarthritis synovial fluids. The decrease of immune complex solubilization capacity correlated with the decrease of hemolytic activity of the alternative complement pathway (P < 0.001) and inversely with the level of immune complexes (P < 0.05). Synovial fluids with low and normal immune complex solubilization capacity were compared; the results confirmed a possible role of the synovial complement system in modulating the size and thus the diffusion and clearance of locally generated immune complexes.