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 less than 0.001) and inversely with the level of immune complexes (P less than 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.