The significance of the fluorescent treponemal antibody (FTA-ABS) test in collagen disorders and leprosy.

A test is described to distinguish the immunofluorescence seen on T. pallidum in syphilis from that due to antibodies against DNA. The method consists of comparing the results of the fluorescent treponemal antibody (FTA-ABS) test with the staining obtained with T. gondii and T. cruzi using an indirect fluorescent technique. The ability of a particular serum to stain other organisms, in addition to T. pallidum, at a significant titre indicates that the treponemal fluorescence is not specific, and the loss of this staining property when organisms are pretreated with deoxyribonuclease suggests that the common microbial antigen is DNA. The isolated treponemal fluorescence found in syphilis is unaffected by pretreatment of T. pallidum. When 123 sera from patients with collagen disorders were examined, non-specific bacterial fluorescence was observed in six sera, while in 95 sera from patients with lepromatous leprosy, a positive FTA-ABS reaction was obtained in 14. There was no accompanying immunofluorescence on other protozoa. Therefore the antibody reacting in the FTA-ABS test in leprosy is likely to be treponemal in origin. A mitochondrial antibody was found in seven out of the 15 sera from patients with lepromatous leprosy.