Objective  To observe the change of interleukin-2 (IL-2) levels in the peripheral blood of patients with secondary syphilis.

  Methods  Totally 26 patients (20 males and 6 females) with acquired syphilis aged 16-76 years (mean 40±13 years), who were treated in the Sexually Transmitted Disease Clinic of Peking Union Medical College Hospital from September to December 2010, were enrolled in this study. Definite diagnosis was based on the results of rapid plasma reagin (RPR) and Treponema pallidum particle agglutination (TPPA) assay. Serum IL-2 level was detected by enzyme-linked immunosorbent assay (ELISA) in these patients and 14 age-matched uninfected volunteers (controls).

  Results  Compared with the controls, serum IL-2 level significantly increased in patients with secondary syphilis(2.510±0.529) pg/ml vs. (2.225±0.157) pg/ml, P=0.016. However, there were no significant differences between the secondary syphilis patients grouped with different age, gender, treatment, IgM, or RPR titers.

  Conclusions  The invasion of Treponema pallidum induces the increase of serum IL-2 levels in patients with early syphilis, which may reinforce the immune response against Treponema pallidum and facilitate the clearance of this pathogen.