Preliminary characterization of inflammatory infiltrates in response to Rickettsia prowazekii reinfection in man: immunohistology.

The local perivascular mononuclear cell inflammatory infiltrate (PVI) response to intradermal (ID) challenge with viable R. prowazekii was studied in a typhus-immune subject. An immunohistochemical method for specific mononuclear cell markers was used on skin punch biopsies taken 6, 24 and 48 hr after challenge. By 24 to 48 hr, the histologic findings were consistent with a delayed-type hypersensitivity reaction (DTHR). Both CD4+ and CD8+ T lymphocytes dominated the PVI at 48 h. CD8+ cells entered the PVI more rapidly than CD4+ cells. Local control of R. prowazekii challenge in an immune human subject was associated with recruitment into the PVI of T lymphocytes which are rich sources of gamma-interferon, and CD8+ T cells which are potentially cytotoxic for R. typhi-infected cells.