Increased serum anti-mycobacterial antibody titers in rheumatoid arthritis patients. Is there any specific antigenic target?

OBJECTIVE: To investigate the presence of immunoreactivity against mycobacterial antigens in the sera of patients with rheumatoid arthritis (RA) and to detect the target of the immune reaction.

METHODS: This study was carried out on 60 patients with RA, and 25 patients with no joint diseases in the laboratory of Clinical Microbiology Department of Ankara University Medical Faculty, Ankara, Turkey between July 2003 to January 2004. Secreted and cellular antigens of Mycobacterium tuberculosis (M. tuberculosis) H37Rv and Mycobacterium bovis (M. bovis) were isolated and purified by high performance liquid chromatography to antigenic fractions. The immunoreactivity of patient and control sera against these antigens were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS: Immunoreactivity against mycobacterial antigens in RA patients were significantly higher than controls. Significant difference between patients and controls has been determined with M. bovis Bacillus Calmette Guerin (BCG) culture fluid and sonicate antigens, but not with M. tuberculosis H37Rv. This suggests that the antigen triggering immune response in patients with RA may belong to or mainly expressed on M. bovis BCG. The ELISA results showed significant difference between RA patients and controls with all antigenic fractions.

CONCLUSION: Presence of increased immunoreactivity against mycobacterial antigens in the sera of patients with RA was detected. When statistical analyses was considered, we cannot put forward any antigenic fraction alone as the one responsible for the increased reactivity.