[Immunity in syphilis].

Following a brief review of the characteristics of the causative organism of syphilis, its maintenance in laboratory animals and its relationship to the treponemes of the tropical treponematoses, consideration is given to the immune reactions and the development of antibodies to the treponeme of syphilis. The individual tests used in the diagnosis of syphilis, especially the complement fixation reactions and the flocculation tests, as well as the reactions employing specific antigens, such as the Treponemal Immobilisation Test (TPI), the Reiter Protein Complement Fixation Test (RPCFT), the Fluorescent Treponemal Antibody Test (FTA-ABS) and the Treponema Pallidum Haemagglutination Assay (TPHA), are discussed in detail. An evaluation of the results of the tests and the possible sources of errors are considered. The problem of the persistence of treponemes after clinically successful treatment is analysed and existing literature reviewed. The paper ends with a discussion of existing knowledge on protective immunity against infection with Treponema pallidum and a reminder of the need for further research into the immunology of syphilis.