Inhibition of complement-mediated solubilisation of antigen-antibody complexes by serum factor(s) in patients with various connective tissue diseases.

Control of immune complex formation is important to limit disease resulting from their deposition in tissues. Any inhibition of immune complex solubilisation is thus significant in the pathogenesis of immune complex diseases. More than half of our patients with various rheumatic connective tissue diseases were demonstrated to have serum inhibition of immune complex solubilisation (12/16 rheumatoid arthritis, 22/37 systemic lupus erythematosus, 16/29 primary Sjogren's syndrome, and eight of nine with mixed connective tissue disease). This serum inhibitory activity did not correlate well with serum levels of IgM rheumatoid factor or circulating immune complexes, and its nature remains to be elucidated.