The immune response to Haemophilus ducreyi resembles a delayed-type hypersensitivity reaction throughout experimental infection of human subjects

Previous work in 3 subjects infected for 2 weeks indicated that experimenta l infection with Haemophilus ducreyi recruits CD4 cells to the skin at the pustular stage of disease. In order to describe the kinetics of the host re sponse, 23 subjects were infected at 2 sites with a standardized dose of H, ducreyi. Subjects were biopsied 1 or 4 days after inoculation or when they developed a painful pustular lesion (days 7-14), Papules and pustules cont ained a predominant T cell infiltrate that consisted of CD45RO and CD4 cell s of the alpha beta lineage. Both papules and pustules contained mixed or T helper 1 type cytokine mRNA and interleukin-8 and tumor necrosis factor-al pha mRNA, Although the subjects had no history of chancroid, their immune r esponses resembled delayed-type hypersensitivity reactions that occurred wi thin 24 h of inoculation and persisted throughout the course of experimenta l infection.