Anti-xanthine oxidase antibodies in sera and synovial fluid of patients with rheumatoid arthritis and other joint inflammations

OBJECTIVE: To study anti-bovine milk xanthine oxidoreductase XOR antibody levels in synovial fluid as well as in serum of patients suffering from rheumatoid affections to assess a possible correlation between antibody titres and severity of disease.

METHODS: Sera and synovial fluids were collected from volunteer donors at Setif University Hospital, Setif, Algeria from 2001-2007 with the consent of patients. Human IgG and IgM levels of free and bound anti-bovine milk XOR antibodies were determined using bovine XOR as antigen, with enzyme-linked immunosorbent assay ELISA.

RESULTS: Serum IgG anti-bovine milk XOR titres in 30 healthy normal subjects 2.74±2.31 microgram/mL are in agreement with that reported in the literature. Immunoglobulin G and IgM anti-bovine milk XOR antibody titres were found to be significantly higher in serum from patients with rheumatoid arthritis RA, and latex positives subjects. Synovial IgM antibody titres to bovine XOR were found to be significantly higher in rheumatoid arthritis patients compared to patients with other joint inflammations.

CONCLUSION: In rheumatoid arthritis patients, high concentrations of antibodies against XOR were noticed. These antibodies may play a major role in RA by inhibiting both xanthine and NADH oxidase activities of XOR. They may also play a key role in eliminating XOR from serum and synovial fluid positive role but unfortunately, immune complex formation could also activate complement and participate in self maintenance of inflammation.