title: CD8(+) T cell knockout mice are less susceptible to Cowdria ruminantium infection than athymic, CD4(+) T cell knockout, and normal C57BL/6 mice.
abstract: The role of T cells in immunity to Cowdria ruminantium was investigated by studying the responses to infection of normal, athymic, CD4(+) T cell knock out (KO) and CD8(+) T cell KO C57BL/6 mice. Normal C57BL/6 mice could be immunized by infection and treatment, and immunity was adoptively transferable from immune to naive mice by splenocytes. Following infection, athymic mice died sooner than normal mice (P=0.0017), and could not be immunized by infection and treatment. CD4(+) T cell KO mice were as susceptible to infection as normal mice and could be immunized by infection and treatment. In contrast, CD8(+) T cell KO mice were less susceptible than normal and CD4(+) T cell KO mice and 43% self-cured, while those that died did so after a prolonged incubation period. Antibody responses to C. ruminantium were CD4(+) T cell dependent, because responses were detected in immune normal and CD8(+) T cell KO mice but not in immune CD4(+) KO mice (P=0.005). Since CD8(+) T cell KO mice were less susceptible to infection, and since CD4(+) T cell KO mice could be immunized, it can be concluded that immunity to C. ruminantium can be mediated by both CD4(+) and CD8(+) T cells.
authors.affiliation: UF/USAID/SADC Heartwater Research Project, Central Veterinary Research and Diagnostic Laboratory, P.O. Box CY 551, Causeway, Harare, Zimbabwe.
authors.forename: B
authors.initials: B
authors.lastname: Byrom
authors.forename: A F
authors.initials: AF
authors.lastname: Barbet
authors.forename: M
authors.initials: M
authors.lastname: Obwolo
authors.forename: S M
authors.initials: SM
authors.lastname: Mahan
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D000907:Antibodies, Bacterial / Q000096:biosynthesis; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000502:physiology*; D004198:Disease Susceptibility / Q000276:immunology; D016995:Ehrlichia ruminantium; D005260:Female; D006357:Heartwater Disease / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL / Q000276:immunology*; D018345:Mice, Knockout / Q000276:immunology*; D008819:Mice, Nude / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial