Elevated levels of anti-proteus antibodies in patients with active rheumatoid arthritis

We carried out this study to determine if our patient population with rheumatoid arthritis (RA) has elevated levels of antibodies to gut bacteria. Seventy patients with RA were categorised as being either active or inactive on clinical grounds. Antibodies to the H and O antigens of Proteus mirabilis and Salmonella typhi were determined by tube agglutination method in these patients, 18 patients with osteoarthritis and 82 healthy controls. There was no significant difference in the anti-proteus antibody titres between both the control groups and patients with inactive disease. However, antibody levels among patients with active disease were significantly higher than controls (P < 0.001). There was no significant difference in anti-salmonella antibody titres among the various disease and control groups. Elevated antibody levels could suggest a role for Proteus as an etiological agent in RA.