Immunological cross-reaction between antigen Tp-4 of Treponema pallidum and an antigen common to a wide range of bacteria.

By electro-immunoprecipitation methods it was shown that antigen Tp-4 of Treponema pallidum, antigen TR-c of the Reiter treponeme and 'Common Antigen' of Pseudomonas aeruginosa are immunologically cross-reactive. This finding establishes a taxonomic relationship between T. pallidum and a wide range of bacteria. The cross-reactivity explains some false positive reactions in serodiagnostic treponemal tests for syphilis. The cross-reactivity may also play a role in a possible 'normal' immunity against infection with T. pallidum induced by antigens by the normal human bacterial flora.