title: CD8+ T cells accumulate in the lungs of Mycobacterium tuberculosis-infected Kb-/-Db-/- mice, but provide minimal protection.
abstract: Recent studies have shown that MHC class I molecules play an important role in the protective immune response to Mycobacterium tuberculosis infection. Here we showed that mice deficient in MHC class Ia, but possessing MHC class Ib (K(b-/-)D(b-/-) mice), were more susceptible to aerosol infection with M. tuberculosis than control mice, but less susceptible than mice that lack both MHC class Ia and Ib (beta(2)m(-/-) mice). The susceptibility of K(b-/-)D(b-/-) mice cannot be explained by the failure of CD8(+) T cells (presumably MHC class Ib-restricted) to respond to the infection. Although CD8(+) T cells were a relatively small population in uninfected K(b-/-)D(b-/-) mice, most already expressed an activated phenotype. During infection, a large percentage of these cells further changed their cell surface phenotype, accumulated in the lungs at the site of infection, and were capable of rapidly producing IFN-gamma following TCR stimulation. Histopathologic analysis showed widespread inflammation in the lungs of K(b-/-)D(b-/-) mice, with a paucity of lymphocytic aggregates within poorly organized areas of granulomatous inflammation. A similar pattern of granuloma formation has previously been observed in other types of MHC class I-deficient mice, but not CD8alpha(-/-) mice. Thus, neither the presence of MHC class Ib molecules themselves, nor the activity of a population of nonclassical CD8(+) effector cells, fully restored the deficit caused by the absence of MHC class Ia molecules, suggesting a unique role for MHC class Ia molecules in protective immunity against M. tuberculosis.
authors.affiliation: Department of Pediatrics, Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA.
authors.forename: Kevin B
authors.initials: KB
authors.lastname: Urdahl
authors.forename: Denny
authors.initials: D
authors.lastname: Liggitt
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bevan
mesh_terms: D000280:Administration, Inhalation; D000336:Aerosols; D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology* / Q000382:microbiology / Q000473:pathology; D002465:Cell Movement / Q000235:genetics / Q000276:immunology*; D006099:Granuloma / Q000235:genetics / Q000276:immunology / Q000473:pathology; D006183:H-2 Antigens / Q000235:genetics* / Q000502:physiology; D064532:Histocompatibility Antigen H-2D; D007113:Immunity, Innate / Q000235:genetics; D007153:Immunologic Deficiency Syndromes / Q000235:genetics / Q000276:immunology / Q000473:pathology; D007371:Interferon-gamma / Q000096:biosynthesis; D008168:Lung / Q000276:immunology* / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D008213:Lymphocyte Activation / Q000235:genetics; D018655:Lymphocyte Count; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009169:Mycobacterium tuberculosis / Q000276:immunology*; D014376:Tuberculosis / Q000235:genetics / Q000276:immunology* / Q000517:prevention & control*
chemical_list: D000336:Aerosols; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D064532:Histocompatibility Antigen H-2D; D007371:Interferon-gamma