Studies on the Depressed Hemolytic Complement Activity of Synovial Fluid in Adult Rheumatoid Arthritis

Summary The hemolytic C'activity (= the no. of C'H50 units per ml.) was determined in synovial fluid and in serum from 68 cases with a variety of joint diseases.A method for estimating the synovial C'activity was selected, which allowed a comparison between different cases.A suppressed synovial C'activity was mainly found in cases of R.A. and in cases of S.L.E.According to the degree of suppression of the synovial C'activity the cases could be grouped from a pronounced to a slight degree of suppression in the following order: classical R.A. with subcutaneous nodules — S.L.E. — classical R.A. without nodules — definite R.A.A suppressed C'activity was found in fresh effusions equally often as in longstanding ones.The synovial C'activity varied independently of the rheumatoid factor titers of serum and of synovial fluid.For cases of R.A. and of S.L.E. a negative correlation was observed between the C'activity and the L.D.H. activity in synovial fluid.This investigation was mainly supported by a grant from Alfred österlund's Fn. — I am endebted to Mrs A. Lundquist and Miss A. Afzelius for valuable assistance in the determinations of complement and to Tutor Gerd Persson (Allmänna Sjukhuset, Malmö) for the carefully performed paper-electrophoretic examinations.