Abstract: Objective To investigate the role of dendritic cell （DC） subsets and T cell subpopulations expressing different intracellular cytokines in the pathogenesis of syphilis. Methods Flow cytometry was utilized to measure the frequencies of peripheral DC subsets and IFN-γ-, IL-2-, IL-4-, IL-10-expressing peripheral CD4+ and CD8+ T cell subpopulations in 20 patients with syphilis before and after therapy, and in 15 healthy human controls. Results The frequency of CD11c+ DC was significantly lower in pretreated patients than that in treated patients （P < 0.01）, but higher than that in the normal controls （P < 0.05）, and the same was true for the frequency of IFN-γ-expressing T cells, IL-2-expressing T cells, and IL-12-expressing T cells. By contrast, a decrease was noticed in the frequency of IL-4-expressing T cells and IL-10-expressing T cells in pretreated patients compared with that in the normal controls. Furthermore, in patients with syphilis, the frequency of CD11c+ and CD123+ DC was unrelated to the percentage of IFN-γ-expressing and IL-12- expressing T cells （both P > 0.05）. Conclusions IFN-γ, IL-2 and IL-12 may exert an immunoregulatory effect in the eliminating of Treponema pallidum, whereas IL-4 and IL-10 may perform an immunoinhibitory effect.

Key words: syphilis, dendritic cell, subset, T-lymphocytes, Cytokines