[Complement (C3)-activating material in synovial fluid from patients with rheumatoid arthritis].

Synovial fluid from patients with the following diagnoses was investigated: - rheumatoid arthritis (RA) - rheumatoid arthritis with benign development (BRA) - osteoarthrosis (A) The sediment was isolated by ultracentrifugation, its C3 cleaving activity measured by 2-dimensional electrophoresis and its concentration if IgG, IgM, IgA, C3, C4 and C3-proactivator by immunoprecipitation. There is evidence that there is more C3 cleaving activity in RA than in osteoarthrosis. Activity levels of BRA were between those of osteoarthrosis and RA. Although there was no significant difference in the IgG-, IgM- or IgA-level of the 3 mentioned diagnoses after 21 minutes of centrifugation (133 000 g), it was possible to demonstrate more C3 breakdown products in RA than in osteoarthrosis and BRA. Very big molecules seem to be responsible for the generation of C3 cleaving products. These observations are not only of theoretical interest but seem also to be useful diagnostically.