Fluorescent treponemal antibody studies.

Fluorescent antibody methods were originally introduced by Coons and associates in 1942. Included in this first publication was a procedure for antibody-fluorescein conjugation and a description of fluorescent reactions obtaincd by means of ultraviolet light microscopy. This communication, and later ones by other authors, indicated that fluorescent antibody procedures were practical for rapid and direct identification of infectious agents, and might be applied in a variety of fields. Fluorescent antibody reactions may be obtained in either of two ways. The direct reaction is most frequently employed for pathogen identification and consists of preparing a highly specific antiserum in an appropriate animal and conjugating the gamma globulin with fluorescein. The value of the finished product or conjugate is judged by its ability to react with, or stain, a specific pathogen and no others. The indirect reaction in contrast to the direct procedure is performed in two stages. First, the pathogen is treated with a specific unlabeled antiserum (example: rabbit serum); and then after washing thoroughly to remove unreaeted serum, fluoreseein labeled goat antirabbit globulin is applied to detect the presence of rabbit antibody. The Fluorescent Treponemal Antibody (FTA) test is an example of the indirect reaction, and as employed, is used to detect human treponemal antibody. Since the pathogen (Treponema pallidum) is a known quantity, the procedure has been modified to detect the unknown quantity (human treponemal antibody or human globulin). The FTA test is performed in the following manner. First, Treponema pallidum is extracted from rabbits in the same manner as is used in the Treponema Pallidum Immobilization (TPI) test. The intact treponemes are dried on microscope slides, and after fixing with acetone, are exposed to the human test serums. Slides are gently rotated at 37° C. to facilitate antibody coupling,