The percentage of activated cytotoxic T-lymphocytes (HLA-DR+ CD8+) and T-helper cells (HLA-DR+ CD4+) was compared with 24 controls (emergency patients, mostly with severe headache, but ultimately without evidence for meningitis or subarachnoid bleeding, see Figure 3): before therapy, the fraction of activated CD4+ as well as CD8+ T-lymphocytes was significantly increased (more than 2 SDs) in this patient’s CSF. This evidence concerns the gene CD4 and infectious meningitis.