Abstract: Objective To study the relationship between the different courses of Treponema pallidum(TP)infection and the immunological changes of the host.Methods ELISA was used to detect the anti-TP antibody in the sera of patients with primary syphilis and secondary syphilis.The MTT chromatometry was used to detect the effect of syphilitic sera on the proliferation of lymphocyte from umbilical cord blood.ABC-ELISA was used to detect the serum level of IL-2,IL-4 in syphilis patients.Results The activity index(AI)of anti-TP antibody in secondary syphilis was higher than that in primary syphilis(t=3.919,P<0.01).Stimulation index(SI)for lymphocyte proliferation in primary and secondary syphilis was significantly lower than that in control group(q₁=12.99,P₁<0.01.q₂=12.04,P₂<0.01).The SI in secondary syphilis group was significantly lower than that in primary group(q=7.18,P<0.01).The serum level of IL-2 in primary syphilis was higher than that in secondary syphilis(t=3.50,P<0.05).The serum level of IL-4 in primary syphilis was not different from that in secondary syphilis(t=1.31,P>0.05).Conclusions The anti-Treponema pallidum antibody significantly increases as the course progresses from primary syphilis to the secondary stage.It seems that the celluar immunity in syphilis patients is suppressed along with the progress of course from primary stage to secondary stage.

Key words: Treponema pallidum, Syphilis, IgG, IgM, Interleukin-2, Interleukin-4