title: Depletion of CD8+ cells abolishes memory in acquired immunity against Chlamydia pneumoniae in BALB/c mice.
abstract: The importance of T cells in Chlamydia pneumoniae infection in mice was assessed by comparing wild-type BALB/c mice with nude mice and mice depleted in vivo of either CD4+ or CD8+ T cells. Whereas wild-type mice cleared the primary infection in 3 weeks, nude mice were only able to restrict the infection and could not clear it during the observation period of 56 days. Nude mice exhibited a greater number of macrophages in their lungs and the pulmonary cells secreted a higher level of tumour necrosis factor-alpha (TNF-alpha) than wild-type mice. Depletion of CD4+ cells did not change the overall infection kinetics of the primary infection. However, depletion of CD8+ cells resulted in a slightly impaired clearance of the bacteria in the late stages of primary infection. To assess the role of the two T-cell subsets in the acquired immunity that develops during primary infection in wild-type BALB/c mice, in vivo depletions were performed during reinfection. Prior to reinfection, immunocompetent wild-type mice were infected and natural immunity was allowed to form. During reinfection, depletion of CD4+ cells did not have any effect on infection kinetics, whereas depletion of CD8+ cells abolished the protection, reverting the infection kinetics and bacterial load to the same levels found in wild-type mice during primary infection. These results show that T cells are necessary for clearing C. pneumoniae infection in mice. Furthermore, whereas neither of the two main T-cell subsets, separately, were essential for clearance of primary infection, the induced protective immunity was strongly CD8 dependent.
authors.affiliation: Department of Vaccines, National Public Health Institute, Helsinki, Finland.
authors.forename: J M
authors.initials: JM
authors.lastname: Penttilä
authors.forename: M
authors.initials: M
authors.lastname: Anttila
authors.forename: K
authors.initials: K
authors.lastname: Varkila
authors.forename: M
authors.initials: M
authors.lastname: Puolakkainen
authors.forename: M
authors.initials: M
authors.lastname: Sarvas
authors.forename: P H
authors.initials: PH
authors.lastname: Mäkelä
authors.forename: N
authors.initials: N
authors.lastname: Rautonen
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D002455:Cell Division / Q000276:immunology; D002690:Chlamydia Infections / Q000276:immunology*; D016993:Chlamydophila pneumoniae; D016207:Cytokines / Q000096:biosynthesis; D005260:Female; D007111:Immunity, Cellular; D007156:Immunologic Memory; D008168:Lung / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude
chemical_list: D016207:Cytokines