IgM class antitreponemal antibody in treated and untreated syphilis.

It is a particular advantage of the indirect fluorescent antibody (IFA) method that antibodies of different immunoglobulin classes may be separately detected and measured by the use of monospecific antiglobulin conjugates. Matuhasi, Mizuoka, and Usui (1966), Kiraly, Bachhausz, Jobbagy, Lajos, and Kovats (1968), Julian, Logan, and Norins (1969), and Atwood and Miller (1969) studied antibodies in syphilis using IFA methods, and are in general agreement that while reactivity in fluorescent treponemal antibody (FTA) tests is due mainly to IgG class antitreponemal antibody, antibodies of IgM and IgA classes also contribute. IgM class antitreponemal antibody, in particular, was present in nearly all sera from cases of early syphilis examined by these workers, but often absent or present only in small amounts in sera obtained later in the disease. The purpose of the present study was to define more precisely the clinical significance of IgM class antibody to Treponema pallidum. 1,100 sera from patients with syphilis (both treated and untreated) were examined by the fluorescent treponemal antibody absorption (FTA-ABS) test for IgG class and IgM class anti-T. pallidum antibody. The observations permit conclusions about the clinical circumstances in which IgM class antibody detectable by FTA-ABS may be expected.