Anti-Treponema pallidum IgM, IgA, and IgG subclass antibody responses after treatment in patients with syphilis at various stages: 1. Assessments by enzyme-linked immunosorbent assay.

Patients with syphilis at various stages were followed from the beginning by serial measurements of antibodies against Treponema pallidum that belonged to the classes IgM and IgA, and to the subclasses IgG1 to 4 by an enzyme-linked immunosorbent assay. A marked decrease in levels of antibodies was noted within three months after treatment. In the case of IgM this occurred in 19 of the 31 patients studied (61%), in the case of IgA in 15 patients (48%) and in the case of one or more of the subclasses of IgG in 18 patients (52%). These findings indicate the usefulness of levels of IgM antibodies as markers for evaluating the effects of treatment. There were, nevertheless, 12 patients (39%) whose levels of IgM antibodies remained consistently below the normal limits or failed to decline despite treatment. In five (16%) of these cases, the serum level of IgA antibodies or of one or more subclasses of IgG fell after treatment. The results suggest the potential usefulness of IgA antibodies in the various IgG subclasses as a marker for evaluating the results of treatment in those patients whose levels of IgM antibodies do not change in response to treatment.