Intrathecal synthesis of anti-mycobacterial antibodies in patients with tuberculous meningitis. An immunoblotting study.

Cerebrospinal fluid (CSF) and serum samples from eight patients with bacteriologically proven (6) or clinically suspected (2) tuberculous meningitis were tested for the presence of anti-mycobacterial IgG antibodies by an affinity-mediated immunoblot technique. This technique is based on agarose gel isoelectric focusing of paired CSF and serum samples diluted to the same IgG concentration, and transfer of the specific IgG antibodies onto mycobacterial antigen-loaded nitrocellulose sheets. An intrathecal synthesis of anti-mycobacterial oligoclonal IgG antibodies, often superimposed on diffuse polyclonal production was shown in all patients but not in patients with tension headache or other neurological disorders. Similar results were obtained when a purified mycobacterial antigen, A60, was used for coating the nitrocellulose sheets in place of a whole mycobacterial homogenate, indicating that A60 was a major immunogen. The number of anti-mycobacterial oligoclonal IgG bands increased with time, and persisted for years even in clinically cured patients. Some IgG bands had no detectable anti-mycobacterial activity, at least with the antigens preparations used in this study. The demonstration of such anti-mycobacterial IgG bands in the CSF could be a useful adjunct for the diagnosis of tuberculous meningitis, especially in the case of negative cultures.