INTRATHECAL SYNTHESIS OF IMMUNOGLOBULIN-G AND MYCOBACTERIUM-TUBERCULOSIS - SPECIFIC HUMORAL IMMUNE-RESPONSE IN TUBERCULOUS MENINGITIS

Local synthesis of immunoglobulin G (IgG) in the central nervous syste m was investigated in 10 patients with tuberculous meningitis (TBM), 1 5 patients with aseptic meningitis (AM), and 15 patients with pulmonar y tuberculosis only (PTBO). The IgG synthesis rate for patients with T BM was 56.4 +/- 18.9 mg/day (mean +/- standard deviation), which was s ignificantly higher than that for patients with AM (8.0 +/- 6.7 mg/day , P < 0.001) and that for patients with PTBO (7.5 +/- 4.4 mg/day, P < 0.001), Therefore, the increased IgG synthesis rate in the central ner vous system provided supporting evidence for differentiating the diagn osis of TBM from that of AM (sensitivity, 100%; specificity, 83.3%), S imultaneous measurement by enzyme-linked immunosorbent assay of IgG se roreactivity to lipoarabinomannan and purified protein derivative anti gens in cerebrospinal fluid (CSF) demonstrated seropositivity in all 6 patients with TBM, 4 of 15 patients with AM, and 4 of 10 patients wit h PBTO. All patients showing false-positive reactivity in CSF demonstr ated seropositivity in sera and normal ranges for IgG synthesis rates in CSF, Also, the semiquantitive measurement of IgG antibody (Ab) tite rs in these patients demonstrated higher IgG Ah titers in serum than i n CSF except for one patient with a highly elevated albumin quotient, suggesting a leaky blood-brain barrier, The results strongly suggested that the Mycobacterium tuberculosis-specific IgG Abs were diffusible through the blood-brain barrier, which addresses the pitfall of serolo gical tests for the early diagnosis of TBM, The serological detection of IgG Abs to lipoarabinomannan and purified protein derivative antige ns in CSF could be misleading in the presence of simultaneously elevat ed levels of IgG Abs in serum.