CXCL13 and neurosyphilis: The CSF CXCL13 level in neurosyphilis patients (median 1905.7 pg/ml, ranged from 15.6 to 57526.1 pg/ml) was the most significantly elevated chemokine in comparison with that in non-neurosyphilis patients (median 15.6 pg/ml, ranged from 15.6 to 4564.39 pg/ml, p = 0.000) (Fig. 2A).