Abstract: | Rabbit antisera to Leptospira interrogans, Borrelia hermsii, and Treponema phagedenis biotype Reiter, reactive to shared spirochetal antigens, failed to enhance phagocytosis of Treponema pallidum by macrophages, while immunoglobulin G to Treponema pallidum subsp. pertenue and Treponema paraluiscuniculi promoted phagocytosis. Opsonic antibodies are directed to pathogen-restricted, not shared spirochetal, antigens. |