CD4 and syphilis: We found that blood CD4+ CD25+ Tregs isolated from secondary syphilis (84.0%±1.4%, P<0.05) and serofast syphilis (84.3%±3.0%, P<0.01) but not primary syphilis (74.5%±1.1%, P>0.05) and latent syphilis (73.8%±1.1%, P>0.05) patients exhibited significantly higher suppressive activity than healthy controls (66.3%±1.1%) at a 1∶1 (suppressor: responder) ratio (Figure 1C).