An analysis of the levels of complement components in the synovial fluid in rheumatic diseases.

A linear relationship between the synovial fluid to serum concentration ratios and log molecular weight was found for six plasma proteins, which are largely synthesized by the liver. Production or utilization of a given protein in the joint can, therefore, be determined by its deviation from the calculated diffusion line. Based on this diffusion model the role of the complement system was investigated in the joint effusions of 48 patients with rheumatoid arthritis (RA), 6 patients with osteoarthritis (OA) and 7 patients with meniscus lesions (ML). Among these three groups quantitative differences were found in the metabolism or utilization of several complement components, based on the fact that the ratios were lower than expected for diffusion of proteins of similar molecular weight. The ratios for the RA group were the lowest. In the three patient groups, results showed increased consumption mainly of C3 and C4 locally in the joint. The existence of a real complement activation in the joints of the three different patient groups was further proved by the elevated levels of C3 breakdown products (C3d). Overall this kind of calculation provides us with a method for studying the role of other proteins which may be important in the inflammatory process of the joint.

Absence of IgA nephropathy in patients with ankylosing spondylitis.

In 40 patients with ankylosing spondylitis (AS) no evidence for IgA nephropathy was obtained. This conclusion was based on the absence of hematuria and on the inability to find an increased incidence of IgA-containing immunoglobulin deposits in skin biopsies. Increased Clq binding assay was only found in those AS patients with anterior uveitis. In 26% of the skin biopsies perivascular mononuclear cell infiltrates were observed, and immunoglobulin deposits were seen in 65%. These facts suggest that the immunologic system is involved in the pathogenesis of this disease.