The ratio of patients with RPR constant positive more than 2 years despite receiving standard syphilis treatment has been reported to be 11.54%~31.3%. The current interpretations on this phenomenon are cellular immune function restrained and the existence of neurosyphilis or asymptomatic neurosyphilis. We conducted this study to detect the treponemal antibody in cerebrospinal fluid (CSF) and lymphocyte subsets in peripheral blood of syphilis patients with persisting RPR positive more than 2 years without neurologic signs, and then explore their relationship. In this study, Treponemal antibody in CSF of 46 syphilitic with HIV negative were measured by syphilis serum test and compared with that of 5 neurosyphilis. Lymphocyte subsets were measured by flow cytometry (FCM) and compared with that of 30 healthy controls. We observed that treponemal antibody in CSF was detected not only in 12 cases (25.21%) of 46 treated patients, but also in 5 neurosyphilis. The ratio of lymphocyte subsets revealed that CD3+, CD4+ T cells and natural killer (NK) cells showed no significant differences between the patient and healthy controls (P>0.05), while CD8+ T cells in patients were significant higher than that in healthy controls (P<0.001). Lymphocyte subsets showed no significant differences between the patients with treponemal antibody positive and negative in CSF (P>0.05). In conclusion, the treponemal antibody in CSF of treated patients suggests that part of them were asymptomatic neurosyphilis and with cellular immunodifeciency. And there is no significant relationship between asymptomatic neurosyphilis and cellular immunodeficiency in peripheral blood.
Keywords: RPR; Syphilis; T-lymphocyte subsets; cerebrospinal fluid (CSF); natural killer cell; neurosyphilis.