Host Defenses in Experimental Scrub Typhus: Role of Cellular Immunity in Heterologous Protection.

摘要

The relative contributions of cellular and humoral immunity in scrub typhus infections were studied in inbred mice employing paired strains of Rickettsia tsutsugamushi differing in virulence. An infectious dose of the less virulent Gilliam strain resulted in heterologous immune protection against and otherwise lethal challenge of the virulent Karp strain. Partial heterologous protection against lethal Karp challenge was observed in animals preimmunized with the Gilliam strain as early as 3 days prior to challenge, whereas complete protection against illness and death existed in animals immunized at least 7 days prior to challenge. Cellmediated immunity played a major role in the heterologous protection observed after Gilliam immunization. This was evidenced by the significant protection against Karp challenge afforded by the passive transfer of spleen cells from animals immunized with Gillaim 7 to 63 days previously.