Inhibition of immune precipitation in rheumatic disease. A clinical and laboratory study.

Antigen-antibody complexes formed in the presence of serum do not precipitate. This complement-dependent function is impaired in approximately half of all patients with seropositive rheumatoid arthritis (RA) but not in patients with other chronic inflammatory arthropathies. As patients with seropositive RA have normal or elevated serum complement levels, this findings suggests that an inhibitor is present in the serum of these patients. Although degree of impairment of solubilization is correlated with rheumatoid factor (RF) titre, decreases in RF titre in patients receiving gold therapy were not always accompanied by improvement of the solubilization process. Thus we can conclude that impaired solubilization is related to, but may be distinct form, RF. Impaired solubilization was associated with the presence of subcutaneous nodules, but not with other systemic features of RA. Thus this phenomenon may be of pathogenetic importance.