Complement metabolism in the seronegative arthritides

Abstract

The plasma concentrations of Clq, C3, C7, and glycine rich β glycoprotein (GBG) (C3 proactivator) have been measured in groups of patients with various seronegative spondyloarthritides. The mean levels of Clq, C3, and C7 were raised in patients with ankylosing spondylitis, Still's disease, and psoriatic arthritis, but not Reiter's disease. Evidence of complement activation was obtained by the finding of C3 conversion on crossed antibody electrophoresis. The absence of GBG conversion to glycine rich γ glycoprotein suggests that activation is by the classical pathway, possibly as a result of the presence of circulating immune complexes.