Antibodies against mycobacterial antigens in the synovial fluid of patients with temporomandibular disorders

In the absence of active pulmonary disease, mycobacterial infection frequen tly causes arthritis and can be considered to initiate autoimmune diseases such as rheumatoid arthritis. Temporomandibular disorder (TMD) is a disease in which pain and impaired mandibular movement appear to arise directly fr om degenerative or inflammatory changes within the temporomandibular joint, but its precise pathogeny has not been elucidated. Here we examined whethe r mycobacterial infection is related to the pathology of TMD. The antibody levels against mycobacterial antigen in the synovial fluid (SF) of patients with TMD were assessed by enzyme-linked immunosorbent assay (ELISA). Six o f 17 TMD patients (35%) were found to possess mycobacterial antigen-specifi c immunoglobulin (Ig) G but not IgM, while the six healthy volunteers posse ssed neither. Western-blot analysis was used to isolate the reacted antigen , and the IgG reacted strongly to 44-kDa antigen. The first 14 N-terminal a mino acid sequences were determined, and computer analysis revealed that it was homologous to translational elongation factor Tu (EF-Tu) of Mycobacter ium tuberculosis, which was a major target antigen for these antibodies. Th e 44-kDa protein of Mycobacterium bovis BCG (BCG) was identical with the EF -Tu of M. Tuberculosis. We cloned the gene encoding the EF-Tu of BCG by usi ng the synthesized oligonucleotide primers by means of polymerase chain-rea ction. The gene was expressed in Escherichia coli. The protein was purified , and the antibody levels against this recombinant protein in the SF of TMD patients were assessed by ELISA. Our findings suggest that some cases of T MD are concerned with the synovial IgG against the EF-Tu of M. tuberculosis , and that the existence of the antibody is a clinical indication of TMD.