In addition, meningeal (3.4±0.9 ng/ml) and parenchymal (2.8±0.5 ng/ml) neurosyphilis patients had significantly lower CSF TGF-β levels than asymptomatic neurosyphilis (10.7±2.0 ng/ml) and syphilis patients without neurological involvement (8.2±1.7 ng/ml), indicating that decreased CD4+ CD25high Treg frequencies in CSF of symptomatic neurosyphilis patients may be associated with low CSF TGF-β concentration. Here, CD4 is linked to neurosyphilis.