Reinfection of chancre-immune rabbits with Treponema pallidum. I. Light and immunofluorescence studies.

Inoculation of infectious Treponema pallidum into the skin of chancre-immune rabbits results in a limited inflammatory response. Intact organisms are identifiable by immunofluorescence in the dermis of the infection site for 1-2 days. By Day 3 structurally intact T pallidum are seen localized in hair follicles, erector pili muscles, and cutaneous nerves, while inflammatory cells containing fluorescent (T pallidum) fragments are seen in the dermis. After Day 6 intact organisms are no longer found. It is proposed that hair follicles, erector pili muscles, and particularly nerves may provide relatively protected sites for T pallidum, and that T pallidum may migrate within nerves. Clearance of organisms from the infected site appears to be mediated by phagocytosis and digestion by macrophages as a result of an accelerated delayed hypersensitivity response, but antibody-mediated destruction and T pallidum migration may also be involved.