Demonstration and immunochemical characterization of natural, autologous anti-idiotypic antibodies throughout the course of experimental syphilis.

Immunoglobulin Gs (IgGs) from serial bleeds obtained 1 week to 5 months after infection of rabbits with Treponema pallidum were examined for autologous anti-idiotypic (auto-anti-Id) antibodies. The capacities of IgGs to bind 125I-IgG F(ab')2 anti-T. pallidum prepared from earlier bleeds were determined by using radioimmunoassays. Results obtained in these assays suggested that auto-anti-Id IgGs were demonstrable between 60 and 180 days postinfection. Following reinfection, 90 days after the initial infection, auto-anti-Id IgGs peaked 6 to 8 weeks later, even though they were first noted as early as 2 weeks postreinfection. In the reinfection model the auto-anti-Id continued to persist throughout the remaining 3 months of the study. As auto-anti-Id antibodies to anti-fibronectin antibodies were demonstrable also in reinfected animals, our findings raise questions concerning the possible role of the anti-Id in modulating the Id expression of both T. pallidum-specific and autoimmune humoral responses.