CD4 and viral meningitis: In neurological disorders such as Lyme neuropathy, bacterial meningitis, viral meningitis, clinical isolation syndrome, and relapsing multiple sclerosis, immune dysregulation of the CSF is characterized by significant changes in the proportion of CD4 T (CD3+/CD4+) and CD8 T (CD3+/CD8+) immune cells as well as cytokine levels in the CSF (Schröder et al., 2018).