title: Requirement for invariant chain in macrophages for Mycobacterium tuberculosis replication and CD1d antigen presentation.
abstract: Mycobacterium tuberculosis is an intracellular bacterium that persists in phagosomes of myeloid cells. M. tuberculosis-encoded factors support pathogen survival and reduce fusion of phagosomes with bactericidal lysosomal compartments. It is, however, not entirely understood if host factors that mediate endosomal fusion affect M. tuberculosis intracellular localization and survival. Neither is it known if endosomal fusion influences induction of host immune reactivity by M. tuberculosis-infected cells. Lysosomal degradation of M. tuberculosis appears to be pivotal for making available lipid substrates for assembly into lipid-CD1d complexes to allow activation of CD1d-restricted invariant natural killer T (iNKT) cells. To clarify the role for endosomal fusion in M. tuberculosis survival and induction of host CD1d-mediated immune defense, we focused our studies on the invariant chain (Ii). Ii regulates endosome docking and fusion and thereby controls endosomal transport. Through direct binding, Ii also directs intracellular transport of the class II major histocompatibility complex and CD1d. Our findings demonstrate that upon infection of Ii-knockout (Ii(-/-)) macrophages, M. tuberculosis is initially retained in early endosomal antigen 1-positive lysosomal-associated membrane protein 1-negative phagosomes, which results in slightly impaired pathogen replication. The absence of Ii did not affect the ability of uninfected and infected macrophages to produce nitric oxide, tumor necrosis factor alpha, or interleukin-12. However, induction of cell surface CD1d was impaired in infected Ii(-/-) macrophages, and CD1d-restricted iNKT cells were unable to suppress bacterial replication when they were cocultured with M. tuberculosis-infected Ii(-/-) macrophages. Thus, while the host factor Ii is not essential for the formation of the M. tuberculosis-containing vacuole, its presence is crucial for iNKT cell recognition of infected macrophages.
authors.affiliation: Department of Dermatology, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
authors.forename: Fenna C M
authors.initials: FC
authors.lastname: Sillé
authors.forename: Constance
authors.initials: C
authors.lastname: Martin
authors.forename: Pushpa
authors.initials: P
authors.lastname: Jayaraman
authors.forename: Alissa
authors.initials: A
authors.lastname: Rothchild
authors.forename: Sarah
authors.initials: S
authors.lastname: Fortune
authors.forename: Gurdyal S
authors.initials: GS
authors.lastname: Besra
authors.forename: Samuel M
authors.initials: SM
authors.lastname: Behar
authors.forename: Marianne
authors.initials: M
authors.lastname: Boes
mesh_terms: D000818:Animals; D017951:Antigen Presentation; D055610:Antigens, CD1d / Q000276:immunology* / Q000378:metabolism; D000944:Antigens, Differentiation, B-Lymphocyte / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D011992:Endosomes / Q000378:metabolism / Q000382:microbiology; D017353:Gene Deletion; D000949:Histocompatibility Antigens Class II / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D018664:Interleukin-12 / Q000378:metabolism; D007694:Killer Cells, Natural / Q000276:immunology; D008264:Macrophages / Q000276:immunology* / Q000382:microbiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D050296:Microbial Viability; D009169:Mycobacterium tuberculosis / Q000276:immunology* / Q000472:pathogenicity*; D009569:Nitric Oxide / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D055610:Antigens, CD1d; D000944:Antigens, Differentiation, B-Lymphocyte; D000949:Histocompatibility Antigens Class II; D014409:Tumor Necrosis Factor-alpha; C045084:invariant chain; D018664:Interleukin-12; D009569:Nitric Oxide