The absence of circulating immune complexes in patients with ankylosing spondylitis.

Sera from 50 patients with well-defined ankylosing spondylitis were examined for circulating immune complexes using both a Clq binding (fluid phase) assay and a Raji cell assay. No more than five of the patients assessed had circulating immune complexes by either one of these techniques and none were positive in both. This result is in contrast to the high prevalence in sera from unselected patients with rheumatoid arthritis and systemic lupus used as positive controls.