title: Lack of CD4(+) T cells does not affect induction of CD8(+) T-cell immunity against Encephalitozoon cuniculi infection.
abstract: Cell-mediated immunity has been reported to play an important role in defense against Encephalitozoon cuniculi infection. Previous studies from our laboratory have underlined the importance of cytotoxic CD8(+) T lymphocytes (CTL) in survival of mice infected with E. cuniculi. In the present study, immune response against E. cuniculi infection in CD4(+) T-cell-deficient mice was evaluated. Similar to resistant wild-type animals, CD4(-/-) mice were able to resolve E. cuniculi infection even at a very high challenge dose (5 x 10(7) spores/mouse). Tissues from infected CD4(-/-) mice did not exhibit higher parasite loads in comparison to the parental wild-type mice. Conversely, at day 21 postinfection, susceptible CD8(-/-) mice had 10(14) times more parasites in the liver compared to control wild-type mice. Induction of the CD8(+) T-cell response in CD4(-/-) mice against E. cuniculi infection was studied. Interestingly, a normal antigen-specific CD8(+) T-cell response to E. cuniculi infection was observed in CD4(-/-) mice (precursor proliferation frequency, 1/2.5 x 10(4) versus 1/10(4) in wild-type controls). Lack of CD4(+) T cells did not alter the magnitude of the antigen-specific CTL response (precursor CTL frequency; 1/1.4 x 10(4) in CD4(-/-) mice versus 1/3 x 10(4) in control mice). Adoptive transfer of immune CD8(+) T cells from both CD4(-/-) and wild-type animals prevented the mortality in CD8(-/-) mice. E. cuniculi infection thus offers an example of an intracellular parasitic infection where CD8(+) T-cell immunity can be induced in the absence of CD4(+) T cells.
authors.affiliation: Department of Microbiology, Dartmouth Medical School, Lebanon, New Hampshire 03756, USA.
authors.forename: M
authors.initials: M
authors.lastname: Moretto
authors.forename: L
authors.initials: L
authors.lastname: Casciotti
authors.forename: B
authors.initials: B
authors.lastname: Durell
authors.forename: I A
authors.initials: IA
authors.lastname: Khan
mesh_terms: D019264:Adoptive Transfer; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000502:physiology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D016207:Cytokines / Q000096:biosynthesis; D009670:Encephalitozoon cuniculi / Q000276:immunology*; D016890:Encephalitozoonosis / Q000276:immunology*; D006412:Hematopoietic Stem Cells / Q000502:physiology; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D011817:Rabbits
chemical_list: D016207:Cytokines