CXCL13 and neurosyphilis: Mechanistically, enrichment and activation of B-cells have been observed within the CNS in neurosyphilis, as well as ectopic germinal centers, suggesting that CNS T. pallidum infection leads to CXCL13 overexpression and a positive feedback loop that recruits and activates a strong humoral response within the CNS that contributes to destruction of neurological tissue (63).