CD4 and syphilis: Compared to syphilis patients without neurological involvement (including primary, secondary, latent and serofast syphilis patients), there was a slight but not significant increase in CD4+ CD25high Treg frequency in peripheral blood of neurosyphilis patients (P = 0.06) (Figure 3A), but the percentage of CD4+ Foxp3+ Treg were significantly higher (P<0.05) (Figure 3B).