ABSTRACT
The Immunological diagnosis of tuberculous meningitis (TBM) requires the presence of de novo synthesis of immunoglobulin in the central nervous system. We investigated the CNS IgG synthetic rate and IgG antibody titers against lipoarabinomanan (LAM) and PPD antigens in the serum and CSF by using ELISA in patients with TBM and patients with only pulmonary tuberculosis (PTB). The CNS IgG synthetic rate was markedly increased in all 11 patients with TB with PTB (56.42+l886 mg/day vs 7.47+435 mg/day). On the other hand, abnormally elevated IgG titers in the CSF against either LAM or PPD antigen were present in all 7 patients with TBM and in 4 of 11 patients with PTB tested. The 4 patients with the false positivity showed markedly elevated IgG antibody titers in the sera suggesting the passive diffusion of IgG antibodies through the intact blood brain barrier from the sera to the CSF. It is likely that the simultaneous measurement of CNS IgG sythesis is an useful addition to the ELISA of IgG antibody titration against the antigens of M. tuberculare in the CSF for the accurate diagnosis of TBM, especially in the endemic area of tuberculosis.