[Specific antibody activity as a marker of pathogen-stimulated immune response in the central nervous system. Exemplified by syphilis and zoster diseases].

Under normal conditions the portion of any antigen specific IgG of total IgG is identical in serum and CSF. This thesis was investigated in 51 patients who were found to have seropositive syphilis without CNS involvement. For this purpose a special index (ITpA-index) was used, based on the ratio of specific IgG per total IgG of CSF to specific IgG per total IgG of serum. This index has a value of 1 (0.5-2), if there is no antibody synthesis in the CNS, as confirmed on the 51 seropositive control patients. In patients with syphilitic CNS involvement the index rose above 2 (3-430), due to local antibody synthesis in the CNS. When there is an ITpA-index below 2.0 in patients with seropositive syphilis who show any CNS symptoms whatsoever, it can be presumed that the actual CNS disease is not a consequence of the former syphilitic infection, but is caused by a condition other than syphilis. In 6 patients with reactive syphilis tests, moderate CSF pleocytosis and increased CSF total IgG, the ITpA-index was below 0.5. Among these 6 patients the inflammatory CNS process was non-syphilitic. The principle of the ITpA-index is applicable to other bacterial or viral CNS diseases insofar as a local humoral immune response takes place. This could be demonstrated in cases of herpes zoster.