FIG 1.

Immune rabbits. (A) Three rabbits inoculated intratesticularly with Tp Nichols were challenged 60 days later, along with an uninfected control, on their shaved backs at each of 8 sites with 1 × 10³ freshly harvested Tp. Black marks indicate location of initial intradermal injections and used to monitoring animals for syphilitic lesion development (representative images 27 days postchallenge). (B) Immunoblot reactivity of sera from the three immune rabbits with Tp lysate strips.