Precipitating antibodies to nuclear antigens in systemic vasculitis

We have examined sera from 61 patients with systemic vasculitis for precipitating antibodies to components of saline tissue extracts. Precipitins were rare in patients with polyarteritis nodosa (PAN) and their absence helped to distinguish PAN from vasculitis associated with other connective tissue diseases. Precipitins were detected in some patients with other vasculitides. Previously described precipitating antibodies (anti-Ro [SSA] and anti-La [SSB]) were restricted to a few patients with features of systemic lupus erythematosus (SLE). A different, as yet unidentified, precipitin which reacted with a component of rabbit thymus extract but not calf thymus or human spleen extracts was detected in many patients with rheumatoid disease. This precipitin was present in all patients with active rheumatoid vasculitis (RV) as well as 52% of patients with uncomplicated but active rheumatoid synovitis. Higher titres of precipitating antibody were present in patients with active RV than those with inactive RV or uncomplicated rheumatoid synovitis, and serial studies showed a good correlation between a fall in antibody titre and healing of vasculitis with treatment. These studies suggest that this unidentified precipitin may be an important marker of RV.