Antibodies to proteus in rheumatoid arthritis.

Antibodies to proteus species were measured in patients with rheumatoid arthritis (RA) and ankylosing spondylitis (AS) and in healthy controls by a Coombs agglutination method. The titres to Proteus mirabilis were higher in 30 RA patients being treated with gold than in 24 patients with active AS (p less than 0.001), 28 patients with inactive AS (p less than 0.001), and 41 healthy control subjects (p less than 0.001). Control studies with Klebsiella pneumoniae var oxytoca showed high antibody titres only in active AS patients.