The sera of 11 adults with primary, secondary, late latent, tertiary, and congenital syphilis were fractionated on a column (Sephadex G-200). A pattern consisting of three protein peaks and a small trailing peak of polypeptides was obtained with each serum. The distribution of immunoglobulins, M, A and G, in the peaks, was analyzed in relation to that of fluorescent treponemal antibody (FTA) and Venereal Disease Research laboratory test (VDRL) antibody. In the primary and secondary stages FTA was found to be both IgG and IgM. But in the eight patients with late syphilis the antibody was only IgG in all but two whose sera also contained some IgM-FTA. In none of the subjects was FTA found to be IgA. IgM-FTA could be detected at lower concentrations than IgG-FTA. This may be a function of the molecular size of the two antibodies.
Atwood WG, Miller JL. Fluorescent Treponemal Antibodies in Fractionated Syphilitic SeraThe Immunoglobulin Class. Arch Dermatol. 1969;100(6):763-769. doi:10.1001/archderm.1969.01610300113021