The serum of a syphilitic subject contains antitreponema antibodies which are globulins. If one fixes a treponeme for example treponemes of Nichols strain, identical to those used in Nelsons test and obtained by passages through rabbit testicles suspension on a slide, these globulin-antibodies will fix themselves on the spirochete, but also act as antigen for an antiglobulin-human serum which also fixes itself on the treponeme antigen-antibody complex. Since the antiglobulin-human serum is combined with a fluorescein derivative, the treponeme becomes fluorescent under ultraviolet examination. On the other hand, in the absence of antibody, that is to say in the study of a nonsyphilitic serum, the antiglobulin is not fixed and the antigen remains nonfluorescent.
Trans. of Societe de Medecine Militaire Francaise. Bulletin Mensuel, v58 p282-287 1964.