1. Mucopolysaccharidase on the surface of Treponema pallidum may be related to its pathogenicity. Human skin, aorta, eyes, placenta, umbilical cord and other tissues are rich in mucopolysaccharides, so Treponema pallidum has a high affinity for these tissues and can be adsorbed on them. Mucopolysaccharidase can decompose mucopolysaccharides in tissues, causing vascular collapse and local blood supply obstruction, and then causing vascular inflammation, tissue necrosis, ulcers and other diseases.
2. Because of the low concentration of Treponema pallidum antigen and weak immunogenicity, the immunity to Treponema pallidum is incomplete. Even if the antibody titer of Treponema pallidum in blood is high, TP can still reproduce and spread. Unresolved pathogens fluctuate with the rise and fall of immunity, and their clinical manifestations are self-healing, latent or progressive syphilis.