Abstract

Synovial fluid cryoproteins from various inflammatory and noninflammatory arthritides were examined for the presence of immunoglobulin, fibrinogen, antiglobulin activity, and third component of complement and correlated with the synovial fluid leucocyte count. The majority of rheumatoid synovial fluid cryoproteins contained either IgG-IgM complexes or IgG alone. Contrary to previous reports, many synovial fluid cryoproteins from psoriasis, Reiter's syndrome, nonspecific acute polyarthritis, gout, and gonococcal arthritis also contained IgG and occasionally IgG-IgM complexes. Noninflammatory synovial fluids were less likely to contain any immunoglobulin. The highest concentration of cryoprotein was found in Reiter's syndrome. There was a significant (P < 0.05) correlation between the presence of immunoglobulin and the concentration of the synovial fluid cryoprotein with the synovial fluid leucocyte count. Since synovial fluid cryoproteins containing immunoglobulin are present in the synovial fluids of many diverse rheumatic diseases not postulated to be immune complex mediated, they may be a nonspecific phenomenon related to the degree of inflammation.