Objective: To observe the changes in peripheral blood lymphocyte subsets in patients with latent syphilis after treatment, who had persistent positive results of test for rapid plasma reagin (RPR) and remained infectious.
Methods: T-lymphocyte subsets and natural killer (NK) cells in peripheral blood were measured with flow cytometry (FCM) in these 43 patients and 30 normal subjects served as controls.
Results: Peripheral blood CD3, CD4 and NK cells exhibited no significant difference between the latent patients and the controls (P>0.05), but CD8 cells were higher in these patients (P<0.05). The treated patients with persistent positive RPR within two years had elevated levels of CD3, CD4 and CD8 lymphocytes (P<0.05), but NK cells appeared to be lowered (P<0.05); in patients with positive RPR for over two years, CD3, CD4 and NK cells were comparable with those in the controls (P>0.05), but CD8 cells was elevated (P<0.05). Patients with RPR positivity within two years had higher CD3 and CD4 lymphocytes, but lower NK cells in comparison with the patients with more than two years' of positivity (P<0.05); CD8 cells were comparable between the two groups (P>0.05).
Conclusions: Cellular immunity imbalance and immune suppression can be present in treated syphilis patients with persistent positive RPR and the risk to transmission, which may lower the host ability to resist and clear Treponema pallidum and is associated with the difficulty in treating syphilis patients and the persistence of positive RPR even after treatment.