Abstract: Objective To investigate the levels ot CD4⁺CD25^bright regulatory T cells in the peripheral blood of patients with syphilis.Methods Flow cytometric analysis was employed to study the surface antigens (CD3,CD4,CD25) of T cells in the peripheral blood of 78 patients with syphilis.Results The proportion of CD4⁺CD25^bright regulatory T cells was significantly higher in patients with sero-resistance than in healthy controls (P<0.01),while no difference was found between the patients with primary,secondary or latent syphilis and healthy controls (P>0.05).The levels of CD4⁺CD25^bright regulatory T cells were not correlated with the titer of rapid plasma regain test in syphilitic patients (P>0.05).Conelusion CD4⁺CD25^bright regulatory T cells may play an important role in the pathogenesis of sero-resistance in syphilitic patients,likely by immunosuppression.

Key words: T-lymphocytes, Syphilis, Sero-resistance